Concorde question

[stilton]

Considering the era in which the Concorde was produced I am curious as to why there was no APU fitted. It would seem to have been quite an inconvenience at times.


Was there ever any consideration given to fitting one and was the decision against the installation solely a weight issue ?

[M2dude]

Hi Stilton, that is a question that we all used to ask ourselves; not having an APU was a major pain in the butt for the fleet, particularly at charter destinations, where air start trucks, GPU's and air conditioning trucks would all have to be pre-arranged.
One problem with 'Conc' was always one of weight, (for every extra pound you carried, another pound of fuel was required) so any APU installation would have to have been light, and worth the extra weight. But the main problem was one of 'where to put the darned thing. The only suitable space available for an APU was in the tailcone, aft of the tail wheel. Now a ready supply of fuel would have been available either from the aft trim tank, #11, or from one of the two trim galleries. (For stability reasons, tank 11 was invariably left empty during ground transits). The real crunch however, was how to arrange pneumatic services from an APU: Tank 11 was directly forward of the tailcone, so this would have meant either ducting the pneumatics THROUGH the fuel tank (not a particularly good idea :)) or externally around the fuselage, which would have been 'draggy' to say the least.
You could still have had an APU powering hydraulics, and in essence electrics too (the emergency generator was powered from the Green System), but without pneumatics for engine starting and air conditioning, it would really have been a waste of weight. Still, it really is a shame that there was no APU.
Historically, there were 'sort of' aux power units fitted to development aircraft: The prototypes had two GTS's (Gas Turbine Starters), one in each nacelle pair, that could start the engines without an air start truck, but these never saw the light of day in later aircraft. The most unusual unit of all was the MEPU (Monogol Emergency Power Unit), located in the tail cone. This was manufactured by Sundstrand, and was fitted to all of the development aircraft. (A derivation of a unit fitted to the X-15!!). The idea was that if you had a four-engined flameout at Mach 2, this thing would fire up, power Green and Yellow hydraulics (plus the emergency generator, again from the Green system), and give you power and control down to a safe relight altitude. The MEPU was powered by Hydrazine rocket fuel (unbelievably unstable) and I seem to remember that the thing would run for about 8 minutes. There was no way that this monstrosity would ever be acceptable on a commercial aircraft, and so a conventional RAT was developed by Dowty for the production aircraft. (Also, the windmilling engines would give you full electrics down to Mach 1.1, and Hydraulics down to about Mach 0.7, so the thing had little practical use when supersonic anyway).
I hope this extended blurb helps answer your query Stilton. :)

[galaxy flyer]

Yes, M2dude, but how long could you remain above M1.1 with a four-engine flameout while drifting down? I presume you would driftdown above M0.7. BTW, the RAT on the F-16 is hydrazine powered as was the ME 162 rocket interceptor.

[M2dude]

Point taken GF, but it was discovered during development flying that that the Olympus 593 could be relit, given sufficient IAS, at almost any altitude within the normal flight envelope. The variable inlet would even be automatically scheduled, as a funcion of N1, in order to improve relight performance at lower Mach numbers. I certainly agree that you would decelerate and lose altitude fairly quickly under these conditions, however a multiple flame out was never experienced during the entire 34 years of Concorde flight testing and airline operation. There was, as a matter of interest an un-commanded deployment of a Concorde RAT AT MACH 2!! (The first indications of the event were when the cabin crew complained about 'a loud propeller sound under the rear cabin floor'. A quick scan of the F/E's panel revealed the truth of the matter). The aircraft landed at JFK without incident, and the RAT itself, apart from a very small leak on one of the hydraulic pumps, was more or less un-phased by the event. Although it sounds horrific, a prop rotating in a Mach 2 airstream, the IAS it 'felt' would be no more than 530 KTS at any time. The RAT was of course replaced before the aircraft flew back to LHR.
Not quite sure about your reference to the RAT on an F16 being Hydrazine powered; a Ram Air Turbine is just that, using the freely rotatting propellor to power hydraulics, electrics or both. Or do you mean the the F16 has an emergency power unit? Either way, it's fascinating stuff.
Yes, I do remember that the Germans used Hydrazine as a fuel during WW2: The father of one of our Concorde pilots was on an air raid to destroy one o the production plants there, this aviation business is such a small world.:)

[galaxy flyer]

M2dude

Thanks for the reply, Concorde expertise is always interesting. I should not have called the F-16 Emergency Power Unit a RAT, it is indeed not. The Concorde RAT was located aft between the engine pods, correct?

What I found interesting is that the AC generators would remain on-line at all; they drop instantaneously at subsonic speeds and the associated N2 rpm. I believe the hydraulics on the 747 will power flight controls down to a pretty low IAS.

Four engine flameout is a very unlikely event, unless one runs into a volcanic cloud.

[stilton]

Thanks M2Dude for your interesting and informative reply.

[TURIN]

For what it's worth, I read a book years ago. "By the Rivers of Babylon" I think it was.
It involved a couple of El-Al (Yes I know hard to believe) Concordes that had APUs fitted in the area normally used as the forward baggage hold. Small it would have to be to fit methinks.

No idea if the author had researched it or just made it up to fit the story.

[M2dude]

Galaxy Flyer
Thanks very much for your comments. It's true, that while supersonic, a windmilling Olympus engine would have sufficient N2 to keep all servics on line. (The hydraulic systems on Concorde also operated at 4000 PSI). The RAT itself was 'said' to be good down to approach speeds, fortunately we never had to find out if that was true. (Although the thing was tested routinely using a hydraulic rig to drive it and check the variable pitch speed control). Thr RAT was in fact located and stowed in the fwd part of the R/H inboard elevon Powered Flying Control Unit Fairing. It was an absolute work of art by Dowty, to make the device fit into such a small space.
Yep, an ash cloud would be particularly bad news, particularly at FL600 :ok:
Stlton
You are most welcome, thank you for posting this topic also. These forums are a wonderful way for all of us out there in the aviation world to share and learn interesting information from each other.:)
TURIN
I remember reading By the Rivers of Babylon many MANY years ago. The terrorists, I seem to remember, had a bomb fitted inside Tank 11 (the rear trim tank) during construction 'before it was welded shut'. Not sure if the author had researched how aircraft were built, but still I guess it sold a copy or two. (Well at least you and I read it).:)

[Christo]

Not quite sure about your reference to the RAT on an F16 being Hydrazine powered; a Ram Air Turbine is just that, using the freely rotatting propellor to power hydraulics, electrics or both.

I think he got confused with the F16 JFS which does use hydrazine but like you mentioned, is most certainly not a RAT :)

[ChristiaanJ]

TURIN,
I've read "By the Rivers of Babylon" too..... and there is some fact behind the fiction.

History does not relate if and where the El Al Concordes would have had APUs.

However, history DOES relate, that the two Concordes ordered by Iran Air WOULD have had APUs (which would have made sense in the Middle East).
Now, Iran Air was the very last company to cancel its orders, and by the time they did, Concorde 214 (now G-BOAG) and 216 (now G-BOAF) were already well underway (they ended up flying initially as white tails).

As a result, both 214 and 216 still have the mounting holes and fittings for an APU. Don't ask me where, but experts know where to find them to this day....

[M2dude]

ChristiaanJ
Both A/C 214 (OAG) and 216 (OAF) were Variant 192 A/C (British Unsold A/C). 216 was later converted to a 102 (British Airways) Variant, where 214 more or less stayed as a Variant 192. I'm not disputing what you say about possible APU mountings (I guess it would HAVE to be at the front section of the lower cargo hold somewhere) but I for one have certainly never seen any evidence of them. I'm still trying to imagine where the air inlet and exhausts would have to be arranged, not to mention pneumatic services ducting/hydraulics. Wouldn't it be interesting to find out? :)

[Dan Winterland]

The original BOAC/BA VC10s didn't have APUs either. The ones converted to K4s for the RAF had to have them fitted.

[ChristiaanJ]

Wouldn't it be interesting to find out? :)It would be, yes!
I can try asking around, but can't remember my original source - it probably came up during a discussion of the MEPU on Delta Golf or on 01 several years ago. I very much doubt it would be mentioned explicitly in the SRM (Structural Repair Manual).
IIRC the MEPU lived in the tail (I'll look it up), so it's not impossible the APU was planned in the same location.

[ChristiaanJ]

Just looked up the MEPU in the 01 AFM, and indeed it's located in the tail cone. I'll scan the page this evening.
In the meantime, here's the MEPU exhaust in the tailcone of Delta Golf, courtesy of Neil Walker.

http://www.concordeproject.com/photos/2006/060306_8.jpg

CJ

[ChristiaanJ]

Just scanned this off the Concorde 01 (G-AXDN) Flight Manual, and cropped as much as possible.

http://img.photobucket.com/albums/v324/ChristiaanJ/MEPU011.gif

http://img.photobucket.com/albums/v324/ChristiaanJ/MEPU012.gif

[M2dude]

Hi Christiaan, yes THAT was the MEPU (Good photo of G-BBDG by the way). As far as fitting an APU in the tail cone, I still personally think that UNLESS you are prepared to pass a sizable pneumatic duct through a fuel tank, (Remember that tank 11 occupied the entire rear fuselage between the rear cargo aft wall and the front of the tail cone). then I don't think that this was really on. (It's quite possible of course that I'm missing something here, it comes with age :}).
As far as the MEPU goes, all it really did was drive 2 hydraulic pumps; the Green System then powering the 40 KVA emergency generator; unless you are going to use the APU for engine starting and ground air conditioning, then I honestly don't think that there would be much point. It's interesting also to note that the MPU, being a rocket motor, needed no air intake, and as it was not driving any huge loads, the exhaust duct dould be quite narrow. :)

[ChristiaanJ]

M2dude,

Nice set of photos of "The Thing" here :
MEPU at MAE at le Bourget (http://f-wtss.over-blog.com/article-15380845.html).
This one is at the Air and Space Museum at Le Bourget, near Paris. My guess is that is was a spare, since the manufacturing date is 1973. 'SA flew in January '73 and 'SB in December '73.
IIRC, Delta Golf arrived at Brooklands with the MEPU still in place; I might have a photo.

As to the installation, we're obviously thinking along the same lines....

However, there were already several conduits through tank 11, such as hydraulics for the tail wheel, various electrics, and the 'backbone' fuel manifolds, that ended at the fuel jettison port in the tailcone.
A couple of fairly substantial air ducts would only have displaced a few hundred kgs of fuel at the most, out of the more than 10,000 kgs in tank 11.

And yes, of course, the whole point of the APU would be to have independent ground start and ground airco available, so clearly an APU would have been bigger and heavier than the MEPU (which was only just over 80 lbs), plus the problem of the air intake and bigger exhaust.
I'd have to get the drawings out to see how easy or difficult it would have been to fit one in the available space.

Since the tailcone was BAC, and both 214 and 216 were built at Filton, I wonder if anybody there still remembers?

[M2dude]

ChristiaanJ
Thanks for the MEPU link, that really brings back memories (or was that nightmares :rolleyes:). I remember at Fairford, a small drop of Hydrazine leaked onto the hangar floor; the next thing you heard was a really loud crack, and a after the smoke cleared, there was a sizable hole in the floor.
I'd still really like to know what the 'thoughts' on this APU issue actually were. Although as you rightly point out tank 11 already had a fair amount of 'plumbing' running through it, we are talking here about a duct with sufficient size that can provide enough mass flow to turn over an Olympus engine to at least between 10 and 20% N2. You are looking at an least 10" diameter duct, not including the copious amounts of thermal insulation surrounding it, as well as an extremely sensitive overtemperature protection system. (This tank is going to be near empty, filled with fuel vapour). I'm not really convinced that this idea would even be considered by the CAA/DGAC/FAA etc. for safety reasons alone.
Still, it's food for thought though :)

[Biggles78]

10,000kg in a trim tank? :eek: No, I am really not that stupid to think it was all used for trim but I am beginning to realise just how little I knew about this technological wonder of the skies. Also wish someone had recorded her being rolled (like the B707 when being displayed). Now that would be something that would stand along side the noise abatement takeoff or maybe not. The T/O is impressive!!

M2dude and ChristiaanJ, please keep posting any anecdotes that you remember about this incredible aeroplane. It really is fascinating learning about the technical side from those who actually knew her.

[ChristiaanJ]

M2dude,

Re the MEPU at the Le Bourget museum...
The story I just got was that it was taken off F-WTSA or F-WTSB at Roissy for a fault and replaced (both 'SA and 'SB operated out of Roissy around '74 / '75 for things like route proving, etc.).
It got left on a shelf in a store, and was only discovered again in 2003 during the "big clean-out" and was saved 'in extremis' by somebody who recognised it for what it was, stopped it from being 'binned' and took it over to the museum.

10,000kg in a trim tank? No, I am really not that stupid to think it was all used for trimInitially of couse it was. It was not until the return to subsonic, towards the end of the flight, that the contents of the n° 11 trim tank were moved forward again to the other tanks.
So yes, you're right, essentially all of it was "useable" fuel, it did not serve only for the trim.

Also wish someone had recorded her being rolled (like the B707 when being displayed).Don't we all....
Jock Lowe seems to have stated there is a photo.... and we all still wonder if there is some footage taken from the Lear Jet during the filming of "Airport 79". But none is publicly known to exist ... we just know it's been done!

[TURIN]

There's an interesting piece here...

Concorde: story of a supersonic pioneer By Kenneth Owen, Science Museum (Great Britain) (http://books.google.co.uk/books?id=VzNUJlX7CXoC&pg=PA206&lpg=PA206&dq=concorde+apu&source=bl&ots=Huz1UKxM0C&sig=93eVfF-V28ZetRthTkN3ncdWwUY&hl=en&ei=Zz9sTLrEOM2K4Aa4uZy4Ag&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBsQ6AEwAQ#v=onepage&q=concorde%20apu&f=false)

Dr Hooker's argument that it makes more sense leaving the dead weight of an APU on the ground rather than carry it around at supersonic speed makes sense. (I presume this is the late Sir Stanley Hooker)

"It surprises me to hear you people asking for equipment to be carried around at supersonic speed when it could be left on the ground. It cannot be economical to carry this stuff around at Mach 2.2 just to save a little labour cost at the airport. On the possibility of aircraft damage, you must organise yourselves so that you do not damage the aeroplane. [Damage by engine starter vehicles to aircraft, and the labour costs involved had been mentioned by Eastern Airlines]. The problems you are imposing involve us in developing entirely new equipment at vast cost. The equipment will be baked consistently at 150 deg C. The problems of certification must be worked out for this equipment and may alter the case considerably."

[ChristiaanJ]

TURIN,
Thnks for the headup... I still have to get that book into my little library.

I've seen that quote before.
Dr. Hooker was right of course.

I think we'll never know what Iran Air's reasoning was......
Even with the vastly inferior infrastructucture in the Middle East at the time, it would seem to me it would have been much cheaper to station enough GPUs and ASUs at their various destinations (only two aircraft, after all), rather than go for an airline-specific APU fit.

[M2dude]

Biggles78
I must admit, it seems excessive carrying 10,000kg in a trim tank, but this fuel system really was a study in elegance. Every single drop of fuel carried was usable by the engines, and the Mach Trimming was so good that you could fine-tune the process so as to achieve the minimum drag configuration for the aircraft of 1/2 degree down elevon in supersonic cruise. One rather amusing point about the fuel Mach trimming; the airworthiness authorities insisted that the aircraft also had a conventional Mach trimmer built into the electric pitch trim system. As the aircraft was mostly flown on autopliot, assuming the fuel trimming was being done correctly (it always was), the auto-trim would wind off this Mach trimming as it was applied, the net result of course being no change to the pitch demand. This really was a totally superfluous addition to the electric trim system. (If for any reason the aircraft HAD been hand flown during acceleration, the pilot would have to nudge the trim button nose down all the time as the A/C accelerated, in order to to oppose the nose up electric trim input).
The fuel, apart from 'lighting the fires' and trimming the aircraft was also used as a cooling medium for engine and IDG oil, as well as for the hydraulic system also. Where it was used to massive effect, was as a cooling medium for the air conditioning system. Here, at Mach 2 conditions, we needed air to exit the 'packs' (on Concorde these were called 'groups') at around -25 deg's C. By the time this air had travelled through the wing ducting it had risen to a sweltering 0 deg's C, at which temperature it entered the cabin. The astonishing thing is, that the air used for this, HP compressor delivery air, P3, was at around 550 deg's C as it left the engine. The ram air itself, used to cool the Primary and Secondary heat exchangers, had a total temperature anything up to 127 deg's C, and to complete this story, the fuel itself had an average temperature of around 60 deg's C. And surprisingly enough, it was a more or less conventional air conditioning system, using air/air intercoolers, an air cycle machine, with just the addition of the fuel exchanger (between the outlet of the secondary heat exchanger and the ACM turbine) to make it any different in concept to most other air cond' systems.

[Biggles78]

Damn, guess I am really that stupid. :O (Let's just keep that between you, Christiaan and myself ).

M2, the figures you give are incredible (I like stats) so I shall ask for more. Anytime you get tired of answering please just say enough.

How much fuel was used in the taxi. T/O roll. To TOC. Usage in cruise. From TOD?
How long did it take to get to TOC and was it done in one hit or were there stages when fuel burn allowed the climb to resume? What was the ground distance covered to get to TOC? How far out was TOD and what was ROD during the approach?

The amusing trim piece I found quite funny. That requirement must have been designed by several different Government committees; net result, nothing changes. :eek:

Had a question on the nose. You mentioned somewhere about a decompression when the nose was lowered to the 5° stage. This indicates that the nose had more than the Up and Down positions that I always thought. Were there multiple nose positions and when would they have been used. (Obviously nose full down was for T/O and Landing)

Last one for this post. What was the CoG range? I remember when I started flying and finally twigged to what it was all about that the PA28 had something like a 5" from the forward to aft limit and was massively surprised by the small "balance point". Trim tanks on 1 aeroplane I flew would have been most welcome. :oh:

I know I have asked a lot so please answer at your convenience.

Many thanks.

[M2dude]

Biggles78
Stupid, you? no way!! (Besides, I'm Mr Stupid of the aviation world, that's my title :E). The thing is, out here in the world of flying machines, there are almost an infinite number of questions (and hopefully answers too). This applies to just about all aircraft from the Wright Flyer up!!. :)
Keep asking away, there are so many of us Concorde 'nuts' out here who are more than happy to help out/bore the socks off you.
Fuel burns: The problem was that when flying slow/taxying, Concorde was an extreme gas guzzler, even when idling each engine burnt around 1.1 tonnes/hour (so every 15 minutes after push back meant over a tonne gone). A typical taxi fuel would be around 1.4/1.5 tonnes, depending on the runway in use on the day. I'd have to leave it to some of my pilot/F/E friends to remember some of the specific fuel burns after take off etc, but I can at least give you some interesting consumption figures:
At the beginning of the take off roll, each engine would be burning around 21 tonnes/hour. (Made up of around 12 T/Hr dry fuel (Fe) and 9T/Hr afterburner (reheat to us Brits) fuel (Fr). As Fr was scheduled against Fe, as a function of inlet total temp (T1) by the time V2 was reached (around 220 KTS) the rising T1 has pushed the total fuel flow (Ft) up to a staggering 25 tonnes/hour/engine. As i've pointed out before in previous topics, although the afterburner only gave us a 17% improvement in take off thrust, it was responsible for around an 80% hike in fuel burn. (Hence that is whay it was only used sparingly). However when reheat was used for transonic acceleration, it used a dramatically reduced schedule (roughly a 60% rise in fuel flow) , so it was not quite as scary. The afterburner would be lit at the commencement of the acceleration (0.96 Mach) and cancelled completely at 1.7 Mach. After this time the aircraft would accelerate on dry power only up to mach 2 and beyond. (The cooler the temperature the quicker the time to Mach 2). On an ISA+ day, it sometimes felt that the aircraft was flying through cold porridge, and could take quite a while to get to Mach 2 after reaheat cancellation, where as on a nice ISA - day, she would go like a bat out of hell, and the AFCS would have to jump in to prevent overspeeds.
Before I hit some more numbers, let me say that with Concorde, TOC = TOD!! After reheat cancellation at Mach 1.7, the aircraft would be at FL 430. The aircraft would climb at an IAS of 530 KTS until Mach 2 was reached at fractionally over FL500. From then on the aircraft would cruise/climb as fuel was burnt, up to a maximum of FL600. On warmish days (eg. the North Atlantic) TOD would typically be around FL570-580. On a cool day (the lowes temperatures would of course be reached in the more tropical regions; the LGR-BGI sector encountered this), FL 600 would be reached easily and she would love to climb some more. BUT, the aircaft was only certificated to 60,000' with passengers onboard, for decompression emergency descent time reasons, and so we were stuck with it. The pity is of course, the fuel burn would have been improved, but we never were able to take advantage of this. On test flights however, the aircraft would routinely zoom climb to FL 630. On her maiden flight, aircaft 208 (G-BOAB) reached an altitude of 65000'; the highest recorded Concorde altitude was on one of the French development aircraft, which achieved 68,000'. On a technical point, the analog ADC's were 'only' calibrated to 65,000'.
Anyway, back to some figues; at Mach 2, 50,000', the typical fuel burn per engine would be around 5 tonnes/hour, falling to around 4.2 tonnes/hour at 60,000'.

THE NOSE You are quite correct in your assumption, there were two positions of droop: 5 deg's for taxi/take-off and low speed flight and 12.5 deg's for landing. The glazed visor retracted into the nose and could ONLY be raised once the nose was fully up, and had to be stowed before the nose could move down. There were 2 emergency nose lowering sysyems; one using stby (Yellow) hydraulics and a free-fall system. Free-fall would drop the nose all the way to 12.5 deg's, the visor free falling into the nose also.

[Biggles78]

Mate, if you could have seen my jaw drop when I read the T/O burn you would probably hurt yourself laughing to much. That is just incredible but the cruise flow seems like stuff all especially considering the speed. The idle flow was also a bit of a jaw dropper. :eek:

Was surprised, yet again, that Mach 2 was achieved without reheat. They really were/are an amazing powerplant.

On my list of regrets, not getting a flight on Concorde would be in the top 5. If they hadn't grounded them what sort of life did the airframes have left in them?

[Nick Thomas]

As I understand it due to friction heat caused by flying at mach 2 Concorde would expand by approx 6 inches. Some of this expansion could be seen between the FE panel and flight deck partition. Obivously the interior would be at a comfortable temp of say 21c; thus the exterior would expand but the interior linings etc would not. So finally to my question- How was this differential expansion delt with? I have really enjoyed reading the clear answers posted answering many interesting Concorde questions.

[ChristiaanJ]

Biggles78,
To complement M2dude's notes re nose and visor:

There were basically four 'positions':
Nose and visor up (supersonic),
Nose up, visor down only (subsonic climd and descent),
Nose down 5°, visor down (take-off and initial climb),
Nose down 12.5°, visor down (approach and landing).

Normally nose and visor are raised and lowered by the green hydraulic system (as is done until today on F-BTSD at Le Bourget).

In 'standby' mode, the visor was lowered by the yellow hydraulic system.
Then the nose uplocks were released by the yellow system, and the nose would free-fall to the 5° position.
Another switch allowed to hydraulically release the 5° downlocks, and the nose would free-fall again, now to the 12.5° psition.
In this 'standby' mode, the nose and visor could not be raised again.

In the best "belt, braces AND a piece of string" tradition of Concorde, if both the 'normal' and 'standby' system failed, there was a big handle on the F/O side of the central pedestal.
This released the nose uplocks manually, the nose would start to free-fall, automatically unlocking the visor, and both would then free-fall down: the nose only to the 5° position.

To complete the story... there is a 5th position: nose 17.5° down!
This was the 'nose fully down' position as designed originally and installed on 001 and 002.
It met with sharp criticism from the test pilots, because of the lack of a forward visual reference with the nose fully down. "It's like looking over the edge of a cliff", was the unanimous comment of the pilots.
So a couple of mechanical stops were added that limited the 'nose down' angle to 12.5°.
But the basic design of the nose was not changed otherwise, so even on the production aircraft the nose could be lowered to 17.5°, but only in the hangar, by removing the mechanical stops. It may have been done a few times, for better access to the visor and nose mechanism.

Minor anecdote... the nose and visor were up during supersonic flight, of course, but also when the aircraft were on the ground and parked outside, simply to keep the rain and dirt out.
But... the prototypes had a metal visor, with two tiny windows, and it was inconveniently dark on the ground in the cockpit with the visor up . So on the ground we always kept the visor down, unless the aircraft was parked outside for any length of time.

[ChristiaanJ]

As I understand it due to friction heat caused by flying at mach 2 Concorde would expand by approx 6 inches. Some of this expansion could be seen between the FE panel and flight deck partition. Obivously the interior would be at a comfortable temp of say 21c; thus the exterior would expand but the interior linings etc would not. So finally to my question- How was this differential expansion dealt with? I have really enjoyed reading the clear answers posted answering many interesting Concorde questions.
"...due to friction heat caused by flying at mach 2 ..."
"Friction" is the "easy explanation", but not really true.
It was due to the air being compressed, being "pushed sideways" by the aircraft trying to make its way through the air at Mach 2, if you like
Same as what happens in a bicycle pump, that get hot as you compress the air. The analogy is somewhat oversimplified, but the phenomenon is the same.
The hottest spots were actually the nose and the wing leading edge, not because of friction, but because that's where the air was locally brought to a total standstill, hence compressed the most. Temperature there could rise to +127°C, from the -50°C and less of the air at 50,000ft just ahead.

"How was this differential expansion dealt with?"
Mostly by attaching things like equipment racks (think of the hat) and floors, and other bits and pieces, to the outer fuselage structure only at one end, and making sure they could move relative to the outer structure when it expanded.
Hope that explains it?

[ChristiaanJ]

...on this APU issue...we are talking here about a duct with sufficient size that can provide enough mass flow to turn over an Olympus engine to at least between 10 and 20% N2. You are looking at an least 10" diameter ductNot really..
We are looking at two 4 inch diameter ducts, the same that are still used to this day on aircraft such as the B777.
One for the air start turbine, which was driven at about 45 psi nominal by the same kind of ASUs (Air Start Units) as are still in use today.
The other for the aircon... not to be confused with the huge near-ambient pressure hoses that were connected directly to the cabin, rather than to the aircon packs.

[stilton]

Absolutely fascinating, the fuel burns are way beyond what I expected.




One of my favourite sentences is that TOC=TOD !



It all makes sense though.




Not to beat a dead horse, but, on the choice of location for APU, the 727 had a problem with this but for different reasons. Because of the location of the engines that were all mounted at the rear, the Aircraft was quite tail heavy and adding more weight with an APU in the tail section was not desirable.



The solution found that I have not seen in any other Aircraft was to mount it in the wheel well transversely across the keel beam with the exhaust out and over the right wing. Quite unusual but it worked fine with the restriction that it could only be operated on the ground.



Its all academic now but, just out of curiosity could this have worked on the Concorde ?

[Nick Thomas]

Thanks for your answer CJ. There must have been some flexibilty built in around the window openings other wise the window openings near the fixed point would show less movement than the ones at the other end which would show 3 to 4 inches difference between the inside panel and the actual window. I guess all the hydraulic and fuel lines must have had some "slack" to allow for expansion.

[ChristiaanJ]

Its all academic now but, just out of curiosity could this have worked on the Concorde ?I would say not: there wouldn't have been any space in the wheel well.
The gears retracted inwards, and when up, the bogies were right next to each other on each side of the keel. As a matter of fact, the main gear legs had to be "shortened" while they retracted, otherwise they wouldn't even have fitted...
...some flexibilty built in around the window openings... 3 to 4 inches difference between the inside panel and the actual window.No, because the inside trim wall panels were relatively short (say about 10 ft, don't remember exactly) and each moved with their bit of fuselage (think roof tiles). Same applied to the floor panels, which also were in fairly short sections. The movement was of course hidden by the carpets.
I guess all the hydraulic and fuel lines must have had some "slack" to allow for expansion.Yes indeed. Flexible sections all over the place.

[M2dude]

Biggles78
Mate, if you could have seen my jaw drop when I read the T/O burn you would probably hurt yourself laughing to much. That is just incredible but the cruise flow seems like stuff all especially considering the speed. The idle flow was also a bit of a jaw dropper. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/eek.gif

I know these fuel flows seem crazy (If take-off fuel flows had been maintained the endurance of the aircraft would have been about 55 minutes!!). But as the majority of the flight was carried out at Mach 2 and above, with the relatively miniscule fuel flows, you can see how we were able to cross the Atlantic with relative ease. It was the subsonic bit that was the pain.
Was surprised, yet again, that Mach 2 was achieved without reheat. They really were/are an amazing powerplant.

The powerplant was as you say truly amazing. We had an, as yet, unmatched engine/intake combination, with a variable primary and secondary nozzles. The variable intake allowed supersonic operation with maximum pressure recovery, minimum aerodynamic drag, as well as extreme operational stability. (Extreme temperature shears, that would have caused surge/unstarts in military installations) were dealt with as a total non event). It's astonishing to believe, but at Mach 2 cruise, the intake provided approximately 63% of the powerplant thrust. It was controlled by the world's first airborne digital control system. (The system computers were built by the Guided Weapons Division of what was then BAC). The combination of the variable intake, plus the LP and HP compressors gave an overall compression ratio of 80:1.
The engine itself, being supplied with air at an ideal pressure, could run at an almost conststant TET, thanks to the variable primary nozzle. This also allowed N1 and N2 (corrected for total temperature) to be controlled more or less independently and run as close as possible to their separate surge lines throughout the entire flight envelope.
The variable secondary nozzle (wide open above Mach 1.1) allowed the jet efflux to gently expand against a cushion of air that was passed over the rear ramp of the intake, through the engine bay and into the annulus of the nozzle itself. This prevented thrust being wasted by the jet efflux widely splaying as it met ambient air that was at a pressure of as little as 1.04 PSIA.
It was this integrated powerplant that made true supersonic cruise possible
On my list of regrets, not getting a flight on Concorde would be in the top 5. If they hadn't grounded them what sort of life did the airframes have left in them?
The airframe life issue was sort of like 'how long is a piece of string?'. The airframes are lifed in supersonic cycles, (which had been extended before, with modifications) and studies were always underway as far as further life extensions were concerned. (Basically the airframe was as tough as a brick outhouse in structural terms). The only real area of concern was the crown area (the roof :O). There was a design flaw here in that the structure had not been designed fail-safe (allegedly by designed a Korean designer at Aérospatiale who, it was said, went a bit loopy). When the FAA evaluated the design (in order for the aircraft to be registered in the USA, for Braniff operations out of IAD) they wanted 'crown planking' to be fitted externally, which would have added over a tonne to the weight of the aircraft, as well as producing some not inconsiderable drag. Fortunately a compromise was reached and additional NDT inspections were carried out, as well as more limited structural modifications. There was a long term, cost effective solution being studied, which would have cured the problem altogether. (The changes would have been mandated, over new requirements for ageing aircraft)

Nick Thomas
Nick, the whole expansion issue was one of the biggest issues that had to be addressed. Wiring looms would 'snake' in some underfllor areas to take up expansion, but the biggest difficulty of all were the mulitudes of hydraulic lines. These required sliding expansion joints, with of course seals to prevent leakage. When a seal deteriorated YPU GOT A LEAK!! (Fluid at 4000 PSI tends torun for freedom very quickly :{). As far as fittings go, ChristiaanJ is quite right, you tried to anchor at one end only. I seem to remember that the passenger seat rails travelled over a roller afair. Fuel lines wer less of a problem, because their relative lengths were less.
I also agree wholeheartedly with ChristiaansJ's explanation about the 'friction' thing, I never really liked those stories. As a matter of interest, 127 deg's, for Mach 2, that would be at ISA +5 (-51.5 deg's C). Any warmer than that and we could not achieve Mach 2, due to the Tmo limit of 127. I remember one year, for several weeks we had unusually high north Atlantic temperatures; these impacted both the flight time AND the fuel burn. The further away you were from Mach 2, the higher the fuel consumption. (The faster you flew, the less fuel you burnt. How's that for a paradox?).
At ISA (-56.5 deg's C) temperatures, the total temperature was at around 118 deg's C.

ChristiaanJ
I remember the 17.5 degree position on the nose; it always looked as if the aircraft was trying to eat ants to me :p. I can not recall personally anyone removing the 12.5 deg' stops for access, although this could of course have been done on your side of the 'puddle' I guess.
As far as the APU ducting issue goes (hee, hee, not often we disagree Christiaan ;)) we are just going to have to agree to disagee about this, although I accept that two 4" diameter pipes (PLUS THERMAL INSULATION) might have done it, BUT I still stand by the other points. :)

Stlton
Not to beat a dead horse, but, on the choice of location for APU, the 727 had a problem with this but for different reasons. Because of the location of the engines that were all mounted at the rear, the Aircraft was quite tail heavy and adding more weight with an APU in the tail section was not desirable.The solution found that I have not seen in any other Aircraft was to mount it in the wheel well transversely across the keel beam with the exhaust out and over the right wing. Quite unusual but it worked fine with the restriction that it could only be operated on the ground.
Its all academic now but, just out of curiosity could this have worked on the Concorde
Unfortunately not; the keel beam area was extremely thin and there was not anywhere near enough room. Interesting solution on the 727 though, I never knew that one.

[Nick Thomas]

Once again thanks M2dude and ChristiaanJ for such interesting answers. Whilst Concorde was not a commerical success it was certainly a technical "tour de force". Would it be too much of an exaggeration to say that Concorde provided the sound technical foundations on which Airbus have now so successfully built?
Am I right in saying that Concorde was the first fly by wire commerical plane?

[M2dude]

Hi Nick, thanks again for your comments. As far as not being a commercial success, for the airline this side of the Channel it was a HUGE commercial success (but of course I accept that in manufacturing terms this was far from the case. The project suffered from very poor financial control). Concorde was the first commercial FBW aircraft as you rightly surmised.
A huge amount of Airbus work was 'burried' in the Concorde project; at Filton a large amount of Airbus components came through that were almost identical to those on Concorde. (witness the STRIKING similarity between the A300 main gear and that of Concorde). Apologies if this post is a little tardy, it's done from my IPhone).:p

[Nick Thomas]

Thanks M2dude.
I agree that Concorde was a commerical success especially for BA. Unfortunatly due to outside factors ie cost of fuel etc; it never had a chance to sell in sufficent numbers.
I wonder if it had been an american product if it would have sold more? Ideal speculation maybe!
What is certain is that everyone involved in designing,maintaining and operating her has every reason to be proud of their contribution to aviation.

[ChristiaanJ]

Once again thanks M2dude and ChristiaanJ for such interesting answers. No thanks needed.. I like plunging back into the history, especially when people are interested, and I have a sneaky suspicion that M2dude does too! :8
Would it be too much of an exaggeration to say that Concorde provided the sound technical foundations on which Airbus have now so successfully built?As M2dude says... to some extent, yes!

As an example in my particular field, you have to be an expert to distinguish the Concorde ADI (Attitude Director Indicator) and HSI (Horizontal Situation Indicator) - the two big central instruments on the pilot's and copilot's panel - from those on the first Airbus, the A300, or the early A310s. Apart from a couple of lights and buttons, they were the same, and the innards were pretty well identical.

And a lot of the technology in the AFCS (Automtic Flight Control System, i.e., the autopilots, etc.) was also virtually indistinguishable (the circuitry was obviously different... an A300 did not do Mach2).

But even more than the technical foundations, Concorde also laid the foundations for an effective and successful international cooperation in aircraft design, development and production.
We learned a tremendous amount from Concorde... Airbus might still have happened without Concorde, but it certainly would have happened years later.

Am I right in saying that Concorde was the first fly by wire commerical plane?Yes, you're right.
The one difference with "modern" FBW commercial planes (such as the A320) is that Concorde still did have a mechanical back-up for when all else failed.
At the time, there was still a doubt about all these new-fangled elektriks replacing good old rods and cables, so when you look under the floor in a Concorde, the rods and cables are still there.
But apart from tests and training for emergencies, essentially they were never used.

[ChristiaanJ]

ChristiaanJ
As far as the APU ducting issue goes (hee, hee, not often we disagree Christiaan ;)) we are just going to have to agree to disagee about this, although I accept that two 4" diameter pipes (PLUS THERMAL INSULATION) might have done it, BUT I still stand by the other points. :)I think we already do agree about the story that Iran Air was going to have an APU, that Rotring had already been put to Mylar to sort out the how and where, and that some traces are likely to be left in 214 and 216.

So I happily agree to disagree on the rest... between the two of us, each looking at our own clues, and with the help of anybody else who has more info, we might still find the answer!

One thought I had... with an APU in the forward baggage hold, you'd also have to take the air intake and exhaust through the pressure hull, and provide sound and thermal insulation for the entire APU itself.
From a design point of view, I'd have gone for the same location of the earlier pseudo-APU (the MEPU), and then solved the remaining problems from that starting point.

[Ozgrade3]

Oh what I would give for M2dude and Christiaan to write technical book on the Concord for pilots to read.....oh and not to forget the stories of operations.

M2dude your info is far from boring.........i call it enthralling. Pure Gold.

As in the great line from a movie ...."more plese"

[galaxy flyer]

Just a note from a mature Yank pilot. When I was first getting interested in commercial aviation around the middle Sixties, Flying magazine (US) had ads from most US carriers featuring the Concorde as the future of aviation. Best of all these were ads to hire pilots, along the lines of "this is your future as an airline pilot-supersonic flight. One offered, "we'll pay you over one million dollars over your career to fly for us." The carriers were TWA, Pan Am, American. The 747 was supposed to a passenger plane as an interim to supersonic flight, it would be a cargo plane. If can find an old magazine and figure out posting it here, I'll do so.

The other great Concorde fact was the variety of simple "rules of thumb" to deal with deceleration and descent over the alert areas off of NYC. CJ or M2, any comments?

[stilton]

With reference to the noise level in the Cockpit with the nose and visor up.


How do you think this compared with say a 747 or 777 at Mach 2 and normal cruise climb levels (500-600) ?


Thanks for the truly fascinating information.

[Sygyzy]

I think you'll have to speak to the Chinese...They have experience of the 747 at supersonic speeds:ok:

[M2dude]

Biggles78
Last one for this post. What was the CoG range? I remember when I started flying and finally twigged to what it was all about that the PA28 had something like a 5" from the forward to aft limit and was massively surprised by the small "balance point". Trim tanks on 1 aeroplane I flew would have been most welcome. :oh:

Sorry Biggles78, I'd forgotten to answer your CofG query, so here we go: CofG was a really critical parameter on Concorde, being a delta, with no tailplane made it more so at take off speeds, and as we've previously said, was how we trimmed the aircraft for supersonic flight. CG was expressed as a percentage of the aerodynamic chord line. To get indication of CG you needed to know the mass of fuel in each tank; easy, from the FQI system. You needed to know the moment arm of each tank, (fixed of course). You then needed the zero fuel weight (ZFW) and zero fuel CG (ZFCG); these were manually input into the CG computers by the F/E, from load control data. The final parameter you needed was total fuel weight, again easy from the FQI system.
The 'normal' T/O CG was 53.5%, but in order to increase fuel weight (and hence range) an extra 'bump' was enabled to allow a max T/O CG of 54%. (CG was indicated on a linear gauge, with forward and aft limit 'bugs' either side of the needle. These bugs would move as a function of Mach and at the lower end of the speed range, A/C weight also). As the A/C accelerated, the limit bugs would move rearwards (with of course the rearward shifting centre of pressure) and so the fuel would be moved from the two front trim tanks 9 & 10 to the rear tank. 11. Once tank 11 reached it's preset limit (around 10 tonnes), the remainder of the 'front' fuel would automatically over-spill into tanks 5 & 7. (Once the fuel panel was set up, the whole process was controlled with a single switch). At Mach 2, the CG would be around 59%, the whole rearwards shift being in the order of 6'. As we said before, the 'final' CG could be tweaked to give us a 1/2 degree down elevon, for minimum drag.
I really hope this helps Biggles78.:)

Guys, back to the Airbus thing; My friend ChristiaanJ gave some really accurate insights, (he always does) but there is another legacy that carries on the this day; some of the audio warning tones were COPIED from Concorde into Airbus. (For example, the A/P disconnect audio is identical). I think this is great, and gives 'our' aircraft a lasting everyday legacy.

As far as the fly by wire goes, Concorde had a relatively simple analog system, with little or no envelope protection (Except at extreme angles if attack). As has been previously poted before, production series test aircraft 201, F-WTSB, pioneered the use of a sidestick within a new digital fly by wire Controlled Conviguration Vehicle sytem, with envelope protection and attitude rate feedback. (This evolved into the superb system known and loved by the Airbus community). It is a really bizaar twist of fate that the Concorde FBW system has more mechanical similarities to the system used in the B777 than Airbus. (Mechanically similar at the front end, with an electric backdrive system moving the column in A/P mode; Concorde being backdriven by a hydraulic relay jack).
As a final piece of irony; the Primary Flight Control Computers on the B777 are designed and built by GEC Marconi Avionics in Rochester Kent, now BAe Systems. This is the same plant where Elliot (becoming Marconi and finally GEC Marconi Avionics) developed and built the UK half of the AFCS computers. Isn't this aviation world strange? :8
Galaxy Flyer
Your inputs here are great, and I'm sure appreciated by all. (I assume from your name that you were a C5A pilot. While I was in the RAF on C-130's, our Lockheed rep' used to supply us all with company magazines, that were full of stuff on this new (it was then) giant of the sky. I fell in love with it there and then).
Anyway, back to Conc': The decel' positions were carefully worked out and adhered to; the aim was to be subsonic to within (I think) 50 nm of the east coast. I'll wait for one of my Concorde pilot friends to confirm that here, but i think I'm correct. I do have a fond memory of one flight out of JFK; we were temporarily 'held' by Boston ATC to Mach 1.6 (and at around FL440) because of an Air France Concorde heading for JFK. We saw this guy above us, at around FL580 on a near reciprical , doing Mach 2, screaming straight over the top of us. We were excited by this amazing spectacle, and so were the AF crew over the VHF ('you never boomed us, did we boom you?'). But the most excited person of all was this guy in Boston ATC. ('I've never seen anything like it guys, your two blips whistled over each other on my my screen like crazy').
Stliton
As far as the F/D noise levels were concerned, once the nose and visor were raised, it was as if someone had switched off the noise :). The main source of noise up there was just the equipment cooling, and that was not bad either. It was, in my view, little noisier up than most subsonics. (But not the 744, where you are so far away from all the racket :p).
Ozgrade3
You're making us blush here; thanks for your comments, I think we are just trying to share some of our experiences (and 'bit's we've picked up over the years).
From my perspective, I did write some stuff used by our pilots, AF even got a copy or two I think.

[Spooky 2]

Facinating posts. On the more human side of the story were the flight crew positions on the Concorde awarded by virtue of seniority or was there a different selction process for these positions? Also was there a freeze in that seat once checked for some period of time?

Thanks!:ok:

[ChristiaanJ]

Ozgrade3,
I would say those books already have been written... from the autobiographies of Turcat and Trubshaw, through the books by people like Brian Calvert, Christopher Orlebar and others, to the Haynes "Concorde Owners' Workshop Manual" (!), that's come out recently.

I've written some bits and pieces, but it's more for my offspring, to explain what all that Concorde junk and documentation in the shed is all about, so they don't all thrash it when I'm gone... I don't think my story would interest a larger public.

As M2dude says, we just like to share some of our experiences with those who are interested.

[Biggles78]

First, I must apologise to Stilton for hi-jacking his thread. I had inadvertantly asked a question in the wrong thread and have only just realised it, so sorry Stilton. The good part of this is all this delicious Concorde info that were are privileged to be receiving from M2dude and ChristiaanJ is all in the one thread. Unless anyone has any objections maybe the Forum Moderator could merged the other 2 threads into this one.

Thank you for the CoG answer. 6 feet sounds like an awful lot but then I am only able to compare it to the littlies that I fly. The ability to use the trim tanks to only have to use a ½° of elevon must have made a substantial impact on performance and the resulting reduced fuel consumption. To think it was all computer controlled at the time when the PC didn't even exist.

M2, you have said that the fuel system was a work of elegance and the above desciption give me a small insight into this. I know that I am just going to have to find books written about this lady to find out more. I have been lazy when asking about item that I could Google but there was a method behind my laziness. When you and Christiaan share your knowledge there is always a personal anecdote or insight that will never be found in any books that I may be able to find. Gentlemen, for this THANKS seem so insufficient. :D :D

The TOC=TOD had me thinking and I believe insomnia may have assisted with some understanding (otherwise the stupid sign for me comes out again :uhoh: ). Gee I hope I have this even partly right. I assume that when accelerating to Mach 2, that it was done while climbing. I was initially stuck with the compression factor of Mach 1 and without thinking the same would happen at Mach 2 (A C Kermode was the hardest book I have read that I didn't understand :confused: ). Therefore with that in mind I was stuck trying to figure TOC=TOD. Am I right or even slightly so in thinking that cruise climb and cruise descent was the flight and there was minimal actual level cruise in the "pond" crossing?

I had also forgotten to take into account the speed factor, DUH!! Subsonic climbs, what 35 - 45 mins to FL4xx and then it is in level cruise for the next 6 hours before TOD. The lady took what, about 3.5 hours, and the extra 20,000 feet it had to climb and descend ate up or into any level cruise it had (or didn't have). Am I on the right track or am I making an ass out of me and me. :)

I was in the jump seat of a B767 on a trans Tasman crossing, CAVOK, when about 2,000 feet lower a dot followed by a straight white cloud approached and passed by. I found that impressive so the 2 supersonics passing at the speed of an SR71 must have been spectacular. Shame radar track isn't available on You Tube. Oh yes, did they boom you?

As you have said, fuel flow was reduced the higher you got. I think it was 5T per powerplant at FL500 down to 4.1T at FL600. Was there any figures for higher the Levels? I am curious to see how much less fuel would have been used at the higher FLs considering it was reduced by 900Kg/hr for just 10K feet. Very interesting what you said about when the temps were ISA+. I would never have thought such a small temperature change could have effected such a signifigant performance result. It also sounds odd, as you said, the faster you go the less fuel you use.

Last greedy question for this post. How much of the descent was carried out while supersonic and how did this affect the fuel flow?

[Coffin Dodger]

As M2dude says, we just like to share some of our experiences with those who are interested.You have a growing audience. This is turning into an extremely interesting thread. :ok:

[M2dude]

What I omitted to say about the Concorde FBW was that autostabilisation commands were superimposed onto the manual/autopilot demands directly at powered flying control unit (PFCU) level, on all 3 axis. . This made the aircraft superbly stable and precise to handle at almost any speed or condition. Apologies for IPhone again ;)

[Biggles78]

I don't think my story would interest a larger public

I beg to differ Christiaan. I am certain your Concorde participation story would be of great interest to the aviation community. The project was a considerable undertaking and is made even moreso when you consider that almost 50 years after its' inception there has never been another aeroplane that has come within a mile (1,852mts) of having the performance of her; military included.

I would hate for all the little tit bits of this important part of aviation history be lost.

There is a thread in the Military Forum called Gaining An R.A.F Pilots Brevet In WWII (http://www.pprune.org/military-aircrew/329990-gaining-r-f-pilots-brevet-ww11.html) where we are privileged to share some the personal stories of the heroes involved in that war. It is critical for our future generations that these stories are known and the participants, their stories and contributions are not forgotten. While Concorde was not part of any military conflict it is still important that the personal side of this massive engineering feat is not lost.

The technical information that you and M2dude are providing is absolutely absorbing but equally so are the personal contributions. An example is the mention above of the Air France and British Airways Concordes passing each other. Anecdotes like that are unlikely to be in the Concorde history books and I am sure there are thousands of other pieces of information like that from both the ground and air that will eventually be lost for all time unless we can get it written down somewhere. Where better than here.

[PA-28-180]

i think it was mentioned before....however, I will add my own comment. One of my greatest regrets in life, was not being able to fly on Concorde. I grew up during a time when my father took me out to Cleveland Hopkins airport to see one of the very first United 747's. This was the epitome of U.S. aviation, and at the same time that Concorde was routinely flying across the Atlantic at Mach 2!

What an incredibly beautiful aircraft it was....and how sad I am that she is now gone. :{

Please continue posting your personal information about this incredible aircraft! :ok:

[Nick Thomas]

Well said Biggles 78. It's not just the technical know how of CJ and M2dude that is so impressive; it's also the clear way that they explain everything.
If an engine had a fire or an explosive failure; it would seem on the face of it that the adjacent engine could easily be affected. As everything on Concorde has a sound technical reason. I have been wondering what that reason or reasons was? and also if there was any inbuilt dividing protection between engines on the same wing?
Not being an expert on jet engines (or any aviation matter), I was wondering am I right to assume that as air pressure decreases with altitude then the amount of thrust needed to maintain M2 would also decrease? This would explain the reduced fuel consumption at higher altitudes.
Would I also be right to assume that the max power delivered by the engines would reduce at altitude, thus even if the engines were run at near to available max power at high altitude it would be no way near the max power at lower levels? The reason I ask this is that I started to think that if the engines were being run at near to max output then the life of the engines would be compromised. Yet if what I have said above is true this would not be the case?
My other query concerns the FE. I understand that he set take off power etc and I can understand that it would be difficult for the pilots to do this at a time of heavy workload. I also understand that he also checked the pilots inputs into the INS system. So was he/she also a qualified pilot?
Once again many thanks

[ChristiaanJ]

Ozegrade3, Biggles78 and all,
I agree, the more of the history that we can write down somewhere, the better....
Just look at the "Did You Fly the Vulcan?" thread here on PPRuNe....

A chance remark by M2dude reminded me of something I meant to write about sometimes... and that has barely been mentioned in the various Concorde stories.
It's the huge gap between the prototypes on the one hand, and the pre-production and production aircraft on the other hand.

It's not just the visor, or the shorter tail.

In my own "field", the AFCS (autopilot, etc.), there was not a lot of similarity between the prototypes and their successors.
The prototypes were "proof-of-concept", designed in the early to mid 1960s.
The pre-production aircraft were designed in the end of the '60s and already close to the production aircraft in most respects.

Some of this difference was due to the very sudden and rapid evolution in electronic technology, with the arrival of the integrated circuit in particular.
The microprocessor - in a way just a large integrated circuit - didn't arrive in time... I don't think there was a single microprocessor on board Concorde until the days that they had to fit TCAS (in the '90s, IIRC).

I'll have to see how to do it.... maybe write it off-line and post snippets on here, then move it into a blog or suchlike?

[ChristiaanJ]

M2dude,
Re your story about the Boston ATC comments about the "crossover".
"That reminds me...."

Ancient tale.

There's this SR-71 Blackbird stooging around Cuba on a top-secret mission, at FL500+ and Mach 2+.... when they get a call requesting them to change heading "because of traffic at your altitude".
Traffic at THEIR altitude ??
Anyway, they comply, and shortly, yes, there's an Air France Concorde out of Caracas (Air France flew there in the early days) slowly sailing across their flight path.

Just imagine... two guys in bonedomes and full pressure suits, in a cramped cockpit, watching something like a hundred people in shirt sleeves or summer dresses, sipping their champagne and maybe just starting on their smoked salmon hors d'oeuvres, flying at their altitude and nearly their speed....

[ChristiaanJ]

Biggles78,

Re your questions about the CofG, this diagram should help you to visualise the CofG "corridor".

http://img.photobucket.com/albums/v324/ChristiaanJ/CGcorridor.gif

It's the one for G-AXDN (01) but the production one is closely similar.

To make some more sense of this.... all those percentages quoted are in terms of the "wing root reference chord".
Mentally cut the wing off the fuselage and measure the length of the cut (including the elevons)..
That's the "root reference chord", and it's 27,76 m.
To give you another reference point: the main gear attachment point is located at 57% ""root reference chord".
So any CofG beyond 57% on the ground, and you have yourself a tailsitter (it's happened)..

[M2dude]

Biggles78
Am I right or even slightly so in thinking that cruise climb and cruise descent was the flight and there was minimal actual level cruise in the "pond" crossing?

You are right on the button. Under NORMAL circumstances, Concorde never flew supersonically in level flight. You would always follow the Vmo bug on the ASI during the supersonic climb. (The ASI pointer actually nudged into the bug; it was a beautiful design). Initially this would be at a constant Vc of 400 kts, the 400 KT segment then went off towards 530 KTS as you climbed. You then 'stuck' to 530 knots until a fraction over 50,000', when 530 KTS became Mach 2. You would then continue the climb at between Mach 2 and around Mach 2.02, depending on the temperature of the day. (the colder the temperature, the faster you tended to fly). There was an extremely complex AFCS mode for the supersonic climb, that I promise to cover in anaother post.
So yes, on the whole, TOC did equal TOD.
The 'subsonic climb' wasn't quite as you thought; you'd normally subsonic climb to FL280, staying there (at Mach 0.95) until the acceleration point. Mach 0.95 was 'subsonic cruise'. But you were on the right track. :)
Oh, and NOPE, they never boomed us either :O
Nick Thomas
If an engine had a fire or an explosive failure; it would seem on the face of it that the adjacent engine could easily be affected. As everything on Concorde has a sound technical reason. I have been wondering what that reason or reasons was? and also if there was any inbuilt dividing protection between engines on the same wing?

Keeping the powerplants as separate as possible was a major design headache, but generally they were just that; there was a titanium centre wall between the two engines and a really substantial heatshield above the engine also, to protect the wing above. To give you an idea how all this worked in practice, in 1980 G-BOAF, flying at Mach 2 between JFK and LHR had a major failure of one of the engines, caused by a defective material ingot used in the forging of one of the 1st stage LP compressor blades; which was subsequently shed. (The analysis done by Rolls Royce ensured that no such incident ever happened again in the life of Concorde). The resulting mayhem terminated in a large amount of engine debris flying around, and a titanium fire burning in the engine bay also. The aircraft however decelerated and landed at Shannon safely. On inspection, although there was extensive damage found in the engine bay, the adjacent engine was completely unmarked, protected by the titanium centre wall, and more importantly, when the heat shield werer removed, the wing was found to be completely undamaged!
The only problem you ever had with the dual nacelle arrangement was if you had an engine surge above Mach 1.6 (These were relatively rare, but could happen with an engine or intake control system malfuntion). If one engine surged, the other would surge in sympathy, because of the shock system being expelled from one intake severely distorting the airflow into it's neighbour. These surges were loud, quite scary (to the crew that is, most passengers never noticed much), but in themselves did no damage at all. Delicate movement of the throttles (employed during the subsequent surge drill) would invariably restore peace and harmony again to all. (The intake on Concorde was self-starting, so no manual movement of the intake variable surfaces should be needed in this event). After this was over, normal flying was resumed again As I said before, these events were relatively rare, but when they did occur, they would be dealt with smartly and professionally; the engine and intake structure being undamaged. (Post surge inspetion checks were always carried out on the ground after an event, on both engine and intake, but nothing much was EVER found).
Would I also be right to assume that the max power delivered by the engines would reduce at altitude, thus even if the engines were run at near to available max power at high altitude it would be no way near the max power at lower levels?
The reduction of fuel flow as you climbed was quite interesting. Although the throttles would be 'at the wall' (dry power remember), the electronic control system was constantly winding fuel off as a function of Static Air Temperature, as well as falling Total Pressure. The system was always 'tweaking' as you climbed, and you only used as much fuel as you really needed to stay at Mach 2. There were various ratings that would also be manually selected at various phases of flight; each rating change 'detuned' the engine slightly, so yes, you did not run the engine when flying fast at anywhere near the levels you did at lower speeds/altitudes. The engine final ratings were changed from 'Climb' to 'Cruise' manually at FL 500, just as you hit Mach 2).

[M2dude]

ChristiaanJ
I don't think there was a single microprocessor on board Concorde until the days that they had to fit TCAS (in the '90s, IIRC).

For once my friend you're not quite correct. The Plessey PVS1580 Aircraft Integrated Data System, fitted to all BA aircraft from mid' 1977 used a microprocessor in the data entry panel. In the mid-80's, a fault interrrogation module was fitted to the Engine Control Units; this used a 4 bit Intel 4004. Otherwise (as usual :p) we agree.
I've some production series CG diagrams, that I will post here when I can find out how to do it......:ugh:

[M2dude]

All Posters
I'm really touched by your comments (as is I'm sure ChristiaanJ), thank you. It's amazing that so many aviation people are still fascinated by this wonderful aircraft.
I'll happily continue to share some more anecdotes if I can, and try and answer any queries that you may have, either here or through PM.
Thank you all for your kind comments.

[galaxy flyer]

M2Dude

Yes, 4,000 hours in Lockheed's contribution to wide-body cargo planes. The marvel in all of these planes from the '60s that they were designed by men who began their engineering careers during WW II, used slide rules and tested nearly everything in the sky. I asked a Lockheed engineer (a Canadian from the Avro Arrow program which throw off a number of engineers to the US) how many guys did the actual design work--his answer was something like 300. With GE engines, the Galaxy is finally reaching its potential. A proper plane--it has a Flight Engineer.

My one contact with the Concorde was when I flew a US corporate jet in the mid-80s for a British-American company (industrial gases, you can guess the rest) whose MD was an American who worked in London. During the summer, like clockwork, he worked in London on the Friday mornings, take the mid-day Concorde to JFK. Customs would meet him AT THE GATE, clear him and turn him over to us for the short flight to Martha's Vineyard. His wife could recognize the plane, meet us at the airport at noon for lunch. On Monday, the return trip would unfurl in reverse. NOT one bit of that story can happen today, I cannot imagine US Border officials doing such a thing.

I did hear that a Concorde did once need a engine change in Dulles.

One more question, could the Concorde lose pressurization, descend to some low level (FL180 or below, perhaps FL100) and make it to scheduled destination or would a divert to Shannon or Gander be required? What was a low level cruise speed?

I was recently at Duxford and did tour the Concorde there, amazing how small the cabin was--DC-9-like.

[Bellerophon]

Nick Thomas

... My other query concerns the FE. I understand that he set take off power etc...

Actually the F/E didn’t set T/O power, but did set most of the other power settings.

Broadly speaking, taxy-out to gear up, and gear down to engine shut down, the handling pilot operated the throttles. At other times, it was (almost) always the F/E.

Bear in mind that several of the routine engine power changes were effected through controls other than the throttles. For instance, selection of the re-heats, engine control schedules, engine ratings and intake lanes were all switch selections.


... I also understand that he also checked the pilots inputs into the INS system...

Correct, using INS3.


...So was he/she also a qualified pilot?..

No, they were professional flight engineers, who held a Flight Engineers Licence; they were not pilots biding their time before moving to the right hand seat.

I believe one or two may have held a PPL, but that was purely incidental, not a requirement.

All of the Concorde FEs had spent years on the VC10, B707, DC10, L10-11 or B747 fleets before coming to Concorde.


Biggles78

...Am I right or even slightly so in thinking that cruise climb and cruise descent was the flight...

Cruise climb, yes. Cruise descent, no.


...and there was minimal actual level cruise in the "pond" crossing?..

Correct, any level flight in the “cruise”, was just coincidence, probably caused by the outside air temperature increasing very gradually. Typically, she drifted up at around 30 to 50 fpm, but, if encountering warmer air, she would start to drift back down, in order to maintain M2.0.


... As you have said, fuel flow was reduced the higher you got. I think it was 5T per powerplant at FL500 down to 4.1T at FL600...

Rather optimistic figures for FL500 I’d have said! 6,000kg/hr/engine would have been nearer the mark!


...I am curious to see how much less fuel would have been used at the higher FLs considering it was reduced by 900Kg/hr for just 10K feet...

The reason the fuel flows dropped so much at the higher altitudes was that the aircraft had to be a lot lighter before she would get up there. It was her lighter weight that was the primary reason for the reduced fuel flows, not the higher altitude.

Forgive me if I’ve misunderstood you, but in her cruise climb, Concorde was flown at her optimum speed (M2.00) with (constant) optimum power set (max cruise power) and so (assuming a constant OAT above the tropopause) the only thing which affected her cruising altitude was her weight.

So, in theory at least, in cruise climb, she was always at her optimum altitude.

Any variation from that optimum altitude, such as a premature climb to higher altitudes, would have cost fuel, not saved it.


... How much of the descent was carried out while supersonic...

At the decel point, the cruise climb ceased and she was flown level at constant altitude. The F/E partially throttled back the engines and she stayed in level flight until her speed reduced to 350kts IAS, typically M1.5.

This took about 50nm, and most of the passengers would have sworn that they were already descending.

She then descended at 350kts IAS, meaning the Mach number would reduce constantly. On a straight in approach to JFK, with no subsonic cruise section, she would become subsonic descending through (around) FL350.

For a straight in approach, in zero wind, on a standard day, from FL600 to touchdown, typical figures would be something like a track distance of around 200nm, flying time of 22 minutes and 3,500kg of fuel.

Into LHR, she had to be subsonic much further away from her destination, and then had a subsonic cruise section on airways, so a slightly different procedure was used, and approaching FL410 she was slowed still further, becoming subsonic around FL400.


Anonymous

In response to your PM, earlier posters were correct in what they posted, however the manual reversion they refer to is a reversion from electrical to mechanical signalling to the flying controls.

There was no way to operate the flying controls manually in the absence of hydraulic power.

[stilton]

Biggles78.


No apology needed, I can't think of anything I have read on this forum that can compare to the delight of this thread.

[Biggles78]

I feel like the fog is begining to clear and I am getting a slight understanding of how she flew. I was hung up with her flying at Mach speeds where as she was flown at an IAS (specific the the profile she was in). The Mach speed, especially when high, was a result of the temperature and not because she was f a s t ! The altitude flown was due to temperature and weight of the areoplane. This is true of all aeroplanes but due to the extreme environment this was more true of Concorde?

The subsonics have issues with Coffin Corner (I think I read that one Airbus model had somehting like 7kts between the high and low end of the envelope when up high); did Concorde have this "problem"?

I remember reading the BA Concorde flew with 2 Captain Pilots (and of course the most important Flight Engineer) and when I was watching The Rise and Fall of the Concorde, I was looking for the 4 bars in the RHS. Didn't see one but on the Air France Concorde the RHS pilot had 3 stripes. Was this correct or are my "little grey cells" confused?(sorry can't type a Belgium accent :{)

I don't know why this popped into my head but what was her glide ratio if all the engines stopped? Maybe because I remember from my early training being told the a B707 had a better glide ratio than the PA28-140 I was learning in. Now that was an eye opener at the time.

[main_dog]

Just wanted to add my voice to those encouraging you to continue... this thread is great stuff! What a fascinating ship; makes my day job on the B744 look plain in comparison :}

I too would like to ask what her idle thrust glide ratio was? From Bellerophon's post: For a straight in approach, in zero wind, on a standard day, from FL600 to touchdown, typical figures would be something like a track distance of around 200nm, flying time of 22 minutes and 3,500kg of fuel.

Sounds like a typical airliner 15:1 glide ratio? (but down from FL600 in 22 minutes :eek:?)

[flyboy_nz]

From Chariots to the Concorde, how far we have come. Words won't describe the feeling the pilots felt while flying her. This has to be in the top three threads on pprune. Thank you so much for making my day.

[M2dude]

:pGalaxy Flyer
One more question, could the Concorde lose pressurization, descend to some low level (FL180 or below, perhaps FL100) and make it to scheduled destination or would a divert to Shannon or Gander be required? What was a low level cruise speed?

We never had a case of lost pressurisation, ever. The cabin windows had dual laminated panes; an inner pressure pane and an outer thermal pane. We had dual systems that kept the cabin at a max diff' of 10.7 PSI, the engine bleeds pushing about 200lb of air per minute into the cabin. This allowed you to fly the cabin at an altitude of around a 6000' maximum only, right up to TOD. If you HAD to fly subsonically, the ideal was Mach 0.95 at FL290. (Subsonically the aircraft had similar range to normal, but took well over twice as long of course). If however you had to shut down an engine, your range deteriorated quite dramatically, and a diversion was usually sought.

It's great that Bellerophon is posting here again; we need a steely eyed Concorde pilot's input here (not just the boffins/nutters and nerds [that's me :\]. To touch more on a couple of his valid points;
Fuel burn: The aircraft would naturally require less fuel as she became lighter and as a consequence gently climbed to maintain cruise Mach number, this is what the engine control system was doing all the time, even though the throttles were wide open it was 'tweaking'.. BUT, the decreasing IAS as you climbed, due of course to the reducing density, just like any other aircraft meant that drag was reducing too, so it was a combination of both of these factors, reducing weight and reducing drag.
Flying controls: It was a slightly weird but wonderful arrangement; pilots inputs would move a servo valve in the hydraulic relay jack, the jack would move in response and drive both a resolver AND mechanical linkages. The resolver ourput was sumed with the flying control position resolvers, and the error signal was fed into an autostab' computer, where it was summed with stabilisation demands (primarily axis rate and acceleration). The autostab computer would the directly drive the surface, and the reducing error signal would reduce the demand etc. While all this was going on, the mechanical linkages would slavishly follow, but as long as you were in FBW (what we used to call 'signalling') mode, these mechanical inputs were de-clutched at the PFCU, so did nothing at all. Only if there was an EXTREMELY unlikely failure of BOTH FBW channels would these inputs be clutched in and the flying control group (rudders, inner elevons or outer and mid' elevons) would then be in Mechanical signalling. The system redundancy was checked after engine start on every flight. But to reinforce what Bellerophon stated, there was no mechanical reversion here; without hydraulics you had nothing. Another aside here; the designers, being paranoid like all good designers (no offence Christiaan :O) were worried what would happen if the controls would somehow jam up. A jammed mechanical flying control input run itself would have no effect on FBW operation whatsoever, due to spring boxes being fitted to the runs. A 'Mech Jam' light would be set, together with a separate red light and audio warning, but this was all. But to completely protect against the aircraft was fitted with a Safety Flight Computer (SFC) system. The idea was, if a control axis (pitch or roll only) jammed up, the captain could press down on a switch light set between the two halves of his control wheel, (at the centre of the 'W') and the Emergency Flight Controls would activate. Strain gauges at the front of the control wheel, two sets on each control column for pitch and roll axis, would input into an SFC that would covert the control force into an elevon demand. These commands were then fed into the autostab' computers, and hence directly into the controls. (A little like L-1011 CWS in a way). There was a little test button that was used to test this system, again after engine start. So although the controls were jammed, the aircraft could still be flown. (Never used in anger I'm pleased to report).
But there was a problem; if this system was inadvertantly used, the results could have been catastrophic, as the system was extremely sensitive indeed, and full elevon movement could be enabled with only moderate effort. Because of this hairy prospect some safeguards were obviously put in place. The first safeguard was an interlock in the autostab' engage logic; If the switchlight had been inadvertently selected beforehand (the light was green by the way) you would not be able to engage pitch or roll autostab's (both channels too) so you would not be going flying until that was fixed. The second safeguard was a little more subtle; A plastic, frangible cover was fitted over the switchlight, unless the captain pressed reasonably hard the cover would prevent the switchlight from being pressed. At least that was the theory, in practice this little bit of plastic could be a pain in the ass :mad:. It was carefully fashioned, and I seem to remember BAe charging the airlines a few hundred pounds each for these things. If some wally fitted the cover upside down (and unless you were careful it was easy to do) THE THING WOULD NOT BREAK!! I remember at Fairford in 1976, G-BOAD was on pre-delivery flight testing, and the late great test pilot John Cochrane was doing a test of the system. The cover on this occasion HAD been fitted upside down, and of course he could not plunge his thumb through it and engage the EFC button. After trying everything, in the end he removed a shoe, took out his pen, and smashed the plastic cover until it broke. (It's OK, the autopilot was engaged at the time). Unfortunately, his combined shoe/pen emergency device also wrecked the switchlight as well, so the system still could not engage. (There was only a switchlight on the captain's side). After he landed and he confronted us all with his dilemma, he was shaking; not with rage but with laughter. (This was the great John Cochrane, sometimes the dour Scotsman but he was always able to see the lighter side). After that event, careful instructions were issued regarding the fit of the cover, and it was modified and made a little more frangible.

[Bellerophon]

Biggles78


...The altitude flown was due to temperature and weight of the areoplane. This is true of all aeroplanes...

Sadly, it isn’t, as subsonic aircraft are allocated a specific cruising flight level and often - for example on the North Atlantic Track system - a specific cruising Mach number as well, and no deviation from that clearance is permitted without specific permission from ATC. Obviously everyone flight plans at the most economic heights and speeds for their aircraft type, but in busy airspace not everyone gets what they want!

Think of your flight plan as being Angelina Jolie, and your ATC clearance as being your wife. Your flight plan is what you’d really like to have, but your ATC clearance is what you’re going to have to live with!


... altitude flown was due to temperature and weight of the areoplane...this was more true of Concorde?...

Subsonic aircraft could equally benefit from using cruise-climb techniques (early long range aircraft crews knew all about cruise-climb techniques and used them when able) but with the large number of subsonic aircraft now using the world’s airways it is impractical for ATC to allow them to drift up and down at will, and so they are assigned specific cruising altitudes.

Few other aircraft got up to Concorde’s cruising levels, and so ATC were able to issue much more flexible clearances to her.

A typical Concorde ATC clearance would have allowed her to accelerate to M2.00 whilst operating within a "block" of altitude, rather than at a specific flight level. Typically this block clearance would have been to operate anywhere between FL450 up to FL600 without restriction.

So, unlike subsonic aircraft assigned a fixed cruising altitude such as FL350, Concorde could, and did, drift up or down, and was thus able to remain at the optimum altitude for the prevailing conditions throughout most of the flight.


... I remember reading the BA Concorde flew with 2 Captain Pilots (and of course the most important Flight Engineer)...

Concorde operated, as did all 3 crew aircraft in BA, with a standard crew of a Captain, F/O and F/E.

A small number of trips had two Captains on board (or two F/Es for that matter) when training or checking was going on, or an extra crew member was carried for PR purposes, but otherwise, the vast majority of occasions, just the standard crew was on board. Everyone preferred it that way, especially the F/O and F/E!


... The subsonics have issues with Coffin Corner (I think I read that one Airbus model had somehting like 7kts between the high and low end of the envelope when up high); did Concorde have this "problem"?...

Have a look at this picture of G-BOAE, cruising at her maximum certificated altitude of FL600, en-route to Barbados on 16 August 2003:


http://i303.photobucket.com/albums/nn142/Bellerophon_photos/P8160022-1.jpg


The available IAS speed range is shown on the ASI, and lies between the yellow and black Barbers Pole, currently indicating 440kts, and the white bug set to 300kts, the VLA (Lowest Authorised speed) at this altitude.

The available Mach speed range is shown on the Mach meter, and lies between the yellow and black Barbers Pole, currently indicating M2.05, and the yellow bug which indicates the lowest Mach number allowed for the current aircraft CG position (the AFT limit) currently showing M1.35.

So, given that at her maximum altitude she had a speed range of 140kts IAS and a Mach range of M0.7, we can see that coffin corner was not a problem!


main_dog


...I too would like to ask what her idle thrust glide ratio was...

By my calculations, the figures quoted for a straight in approach, give an average glide ratio of around 20:1, however these were for a standard decel/descent, and on Concorde the early part of the decel/descent was not flown at idle power.

A considerable amount of power was left on initially, around 94% N2, for various reasons, and only below M1.0 were the throttles usually selected to idle.

I hadn’t noticed it until now but there does not appear to have been a chart giving glide distance at idle thrust!

However, since the speeds to be flown during the “4 Eng Flame Out” procedure were not too far from the normal decel/descent speeds, I’ll hazard a guess (and that is all it is) that the glide distance from FL600, with no thrust, would have been about 150nm, giving a glide ratio of around 15:1.

[ChristiaanJ]

[Re microprocessors on Concorde]
ChristiaanJ, for once my friend you're not quite correct. The Plessey PVS1580 Aircraft Integrated Data System, fitted to all BA aircraft from mid' 1977 used a microprocessor in the data entry panel. In the mid-80's, a fault interrrogation module was fitted to the Engine Control Units; this used a 4 bit Intel 4004.You're right, M2dude, I should really have written that there were no µPs on board when she first went into service (1976), and that they only slowly filtered in afterwards.

Another example on the BA aircraft, of course, in full view of the pax, were the "Marilake" cabin displays that showed Mach, altitude, speed, etc. that replaced the earlier Mach-only displays, and where everybody just HAD to have their picture taken once at Mach 2. Each of the four displays (two up front, two at the back) had a micro-processor.

Not sure when those were first fitted.... it was during one of the cabin re-do's and livery changes.

[ChristiaanJ]

Re the questions about depressurisation, this may be useful.

http://img.photobucket.com/albums/v324/ChristiaanJ/Decompression.gif

It shows the emergency descent profile (solid line, 'Avion'), and the resulting effect on the cabin altitude (dotted lines) in the cases of one window ('hublot') blowing out with either three or four air conditioning packs ('groupes') operating.

As the graph shows, in the worst case the cabin altitude rises to about 40,000ft for about two minutes before starting to drop again, which is survivable when breathing oxygen.

It was studies like this, that lead to the small windows on Concorde. Keen spotters may actually notice that the windows on the prototypes are bigger than on all the other aircraft :8

The diagram is taken from "The Concorde Story" by Chris Orlebar, but the original was so pale that it was uncopyable, so I did redraw it, in answer to a question by a French friend (hence the legends in French).

[Biggles78]

...The altitude flown was due to temperature and weight of the areoplane. This is true of all aeroplanes...
Sorry Bellerophon, a badly worded question from me but you gave a really good analogy. Gonna remember that even though I don't like my Flight Plans have collagen filled lips. :E I will see if I can reword it to make it comprehensible. :ugh:

Thank you for the Instrument Panel image that I have now added to my collection. What is the Yellow Arc on the Mach metre that starts at about M1.12?
Do you remember if you had a signifigant headwind at that stage? I notice that the G/S is 1,139kts was this fairly standard for an East-West flight? (DUH me. Just read the fastest crossing was an east-west direction. Winds must have been quite favorable) I am now guessing the displayed G/S would be fairly typical, plus or minus a bit.
The Glide Ratio, even if it is a highly educated guess, is impressive. I would not have expected it to have been about the same as a B747. How many more times is this Lady going to surprise me with her performance.

Also notice the ball is slightly off to the left even though it is still inside the lines. Was this normal or does it need a tad more rudder trim? Can't imagine it is really out of balance.

Everyone preferred it that way, especially the F/O and F/E!
Was that because of the tight fit on the flight deck or because we really don't like others in our workspace? :uhoh:

ChristiaanJ thanks for the CoG diagram. That I am still getting my head around. There is a large range at the bottom and top of the speed range but fairly narrow in the mid speed range. Seems like 165T was a less complex balancing act than it was at 105T.

The center rear fuselage gear unit, what was that for? I have seen it deployed on many occasions but I can't for the life of me remember if it was during T/O or LDG however it didn't seem to be extended every time the aeroplane flew. Was this used during loading so she didn't accidently "rotate" at the ramp or to avoid a tailstrike during LDG? I can't imagine an over rotate during T/O.

And a big Thank You to Bellerophon for sharing his knowledge with this thread.

[ChristiaanJ]

Re Mach 2 ....

In the earliest days of the project, Concord(e) was described as a Mach 2.2 airliner.

Once the RR58 alloy arrived, and the first thermal fatigue tests were underway, Mach 2.2 appeared as somewhat optimistic, and to assure an acceptable airframe life, the Mmo (maximum operating Mach number) to be certified was brought down to Mach 2.04.

Interesting question just asked by somebody on another forum....
Why Mach 2.04 ? Why not Mach 2.10, or Mach 1.96 ?
With thermal fatigue still being a field that was only starting to be explored, was that a fully technical choice.... or was there a commercial aspect ?

Mach 1.96 would again have meant a few more hours life for the airframes, and would not really have made a significant difference in the flight duration.
But think of the huge difference between "more than twice the speed of sound" and "not quite as fast as twice the speed of sound".....
Mach 1.96 would simply not have "sold"......

I have no answer to the question who finally decided on '2.04', and I don't think many of the people that wrote the "TSS spec" are still with us, so we'll probably never know.


And along the very same lines, another snippet.....

In 1985, during a major cabin upgrade, BA installed the "Marilake" displays, that showed Mach, altitude, groundspeed, etc. in place of the simple Mach-only displays that Air France kept until the end.
Nice display, complete with microprocessors.... you must have seen photos.

Of course everybody wanted their photo taken next to the display saying "Mach 2".
So these display were subtly programmed to read "Mach 2.00" as soon as the Mach number was above 1.98, and they stayed there....even if the aircraft went to Mach 2.03 or beyond.
A tiny bit of cheating... but commercially it made a lot of sense, of course.

Like the earlier BA cabin displays, the Air France displays only showed the Mach number, and they were little more than "rescaled" digital voltmeters that directly displayed the 0-12V Mach signal from the Air Data Computer. They tended to flicker a bit from 2.00 to 2.01 to 2.02 and back, but at least they didn't "cheat". And I still proudly have a photo of myself with a "Concorde grin", at Mach 2.03 !

[Nick Thomas]

I have yet another couple of questions and I hope all you Concorde experts don't mind me taking up your valuable time.
As regards fuel burn: was there any difference between each indvidual airframe and if so was it significant enough to be considered when calculating the trip fuel? Also did different engines also have slightly different fuel consumption?
Whilst on the subject of engines, I just wondered how many were required to keep the BA Concorde fleet flying? What sort of useful life could be expected from the engines?

[norodnik]

Fascinating thread!

I think (along with the other PAX that day) that I can claim to have been faster on Concorde than anyone else.

Despite many trips, I only flew on BOAB once (sad I know) and there was obviously a malfunction of some sort as the speed (on the Marilake display), instead of stopping in the normal range of 1260-1320 mph continued steadily climbing to 1990 mph.

This was the second "fault" as we had previously begun the flight from JFK with a low speed RTO due to one of the computers disagreeing with the other 2 on takeoff. Despite the slow speed we still had to wait 10 mins for the brakes to cool.

I have it all on Video! (The RTO and the Speed anomaly)

[ChristiaanJ]

I have yet another couple of questions and I hope all you Concorde experts don't mind me taking up your valuable time.In my case, my time is no longer THAT valuable, being retired for several years !
And I enjoy answering those questions, if and whenever I can!
As regards fuel burn: was there any difference between each indvidual airframe and if so was it significant enough to be considered when calculating the trip fuel?There WERE differences... after its misadventure at Dakar, F-BVFD definitely consumed more fuel, although IIRC he was already reputed as a gas guzzler even before that incident.
It was one reason why, when Air France withdrew an aircraft from service, Fox Delta was the first one to go.
Also, due to the gradual improvements in production methods, and minor redesign, the last British production Concorde, G-BOAF, was about a ton lighter than the first one (G-BOAC). While the differences weren't huge, they were noticeable.
Also did different engines also have slightly different fuel consumption?Of course... but there I have no figures at all, and I doubt the differences, evened out over four engines, were really significant.
Whilst on the subject of engines, I just wondered how many were required to keep the BA Concorde fleet flying? What sort of useful life could be expected from the engines?Interesting question, and I hope somebody will come in and answer it.
According to 'Wikipedia', 67 engines were built, which would mean, in theory, 64 engines for 16 aircraft and 3 spares....
In practice, of course, fewer aircraft flew at any one time, so the statistics are different, but even so, a lot of engine swapping went on over the years.
As to the MTBO, I don't know... it's not my field at all....

[ChristiaanJ]

....there was obviously a malfunction of some sort as the speed (on the Marilake display), instead of stopping in the normal range of 1260-1320 mph continued steadily climbing to 1990 mph.Nice one....
That would have been about Mach 3 !!!!!!
(Without taking head or tail wind into account.)

[stilton]

Christiaan J


What happened to the Concorde at Dakar ?

[ChristiaanJ]

What happened to the Concorde at Dakar ?The story has never been fully elucidated....
But in brief, F-BVFD made an extremely hard landing at Dakar in November 1977, with a vertical speed in the order of 14 ft/sec (with 10 ft/sec being the formal limit).
The result was a major tailstrike, ruining the tail wheel and some of the tail structure.
The aircraft was repaired, repatriated, and put back into service, but it was the first one to be withdrawn from service when the Paris-Dakar-Rio route was closed.

In the end it was scrapped in 1994... only a section of the forward fuselage still remains in the stores of the Air and Space Museum at Le Bourget (Paris).

[M2dude]

Biggles78
What is the Yellow Arc on the Mach metre that starts at about M1.12?
This is the minimum Mach number that can be flown with the existing CG. (which would be around 59%). Just as the CG indicator (not shown in this photo) gave minimum and maximum CG for a given Mach number, the Machmeter gave a reciprical indication also). You can also see that as the aircraft is not flying at Vmo any more, being at Mach 2 cruise, that the VSI pointer is now away from the orange and black Vmo bug. At our 'not so coffin corner', now that the aircraft is at maximun alllowable altitude, Vmo would naturaly coincide with Mmo; the orange and black Mmo bug being shown at Mach 2.04. This really superb photo taken by Bellerophon gives a graphic illustration of what the panels looked like at Mach 2. Note that the with the TCAS VSI Concorde retained it's original linear VSI also. (Miust have beeen the only aircraft flying with FOUR VSIs. (The originals had to be retained due to the fact that the autopilot Vert' Speed Mode error was derived from the indicator itself. As far as TCAS goes, R/As werer inhibited above FL300 (on acceleration this would coincide with the aircraft becoming supersonic, and the mfrs would not countenance the aircraft doing extreme manoeuvrs as a result of TCAS RAs at supersonic speeds).
The center rear fuselage gear unit, what was that for? I have seen it deployed on many occasions but I can't for the life of me remember if it was during T/O or LDG however it didn't seem to be extended every time the aeroplane flew. Was this used during loading so she didn't accidently "rotate" at the ramp or to avoid a tailstrike during LDG? I can't imagine an over rotate during T/O.

The tail wheel was lowered for all 'normal' gear cycles (not stby lowering of free-fall). It was designed to protect the bottom the nacelles in the case of over-rotation, but in practical terms the thing was a waste of space (and weight) and a simple tail skid (used on the prototypes) would have sufficed. Any time that the tail wheel contacted the ground, it would ALWAYS collapse, damage the tailcone structure and in fact aforded no protection whatsoever. Fortunately these events were EXTREMELY few and far between. The biggest problem with the tail wheel was a major design flaw: On gear retraction the assembly would retract in sequence with the nose and main gear, and as it entered the opening in the tailcone, it would release over-centre locks that were holding the spring-loaded doors open. The doors would then firmly spring shut behind the gear assembly and finish the job. UNFORTUNATELY this was a very poor design; if for any reason one of the two doors had not gone over-centre on the previous gear lowering, it would be struck by the retracting tail wheel gear and cause structural damage to the local skin area, that would have to have a repair done. Unfortunately these events were not quite so rare, and several measures were tried to reduce the chance of this happening. Although not a safety issue, it was an issue that was a total pain. (As a matter of interest, G-BOAC had this happen on one of it's first test flights out of Fairford in 1975).
Nick Thomas
As regards fuel burn: was there any difference between each indvidual airframe and if so was it significant enough to be considered when calculating the trip fuel? Also did different engines also have slightly different fuel consumption?

As ChristiaanJ said, the last two BA aircraft WERE lighter than the others, and would be preferred aircraft for certain charters. But that is not to say that any aircraft could not happily do ANY sector. We fortunately had no distorted airframes in the British fleet, so this was never an issue. There was very little spread, regarding fuel consumption between different engines; one of the best parts about the Olympus 593 was that it hade very little performance deterioration with time, it was an amazing piece of kit.
Whilst on the subject of engines, I just wondered how many were required to keep the BA Concorde fleet flying? What sort of useful life could be expected from the engines?

Time on wing for the engines was a real variable. Each engine was built up of modules, each one of these had a seperate life. In the early days of operation, time on wing was quite poor, and MANY engines would be removed on an attrition basis. One of the early failure problem was the fuel vapourisers inside the combustion chamber were failing, taking bits of turbine with it!! A Rolls Royce modification that completely changed the design of the vapouriser not only solved the problem completely, but also increased the performance of the engine. As the engine matured in service time on wing greatly improved, and in service failures became a thing of the past. A 'trend analysis' was done after each protracted supersonic flight, where engine parameters were input into a propiatry RR computer program, that was able to detect step changes in the figures, and if this were the case, more boroscope inspections were carried out. The OLY time on wing was nothing compared to the big fan engines, but the conditions that it operated under bore no comparison. Not really sure about absolute figures on this one Nick, I'll ask one of my Rolls Royce friends and see if I can find a figure.

[nomorecatering]

One thing I have noticed on take-off is the way the throttles are handled. Application of take-off thrust is done by slamming the throttles forward rather than the traditional ease them up method used on most other aircraft.

Why.

[Bellerophon]

nomorecatering

...I have noticed...Application of take-off thrust is done by slamming the throttles forward rather than the traditional ease them up method used on most other aircraft...Why...

It does seem rather brutal at first glance doesn't it, especially if you are used to handling piston engines with care!

Firstly however, unlike most jet aircraft, you never set reduced thrust for take-off but always set full power, which on Concorde meant that the throttles had to be fully forward, as far as they would go.

Secondly, you were not actually controlling the engines as directly as you might think. Various control units between the throttles and the engines would electronically regulate everything for you, especially spool-up rates, temperatures and thrust levels, even keeping #4 eng throttled back initially to 88% until reaching 60kts.

In effect, you were really just operating a switch telling the computers to set full take-off power.

And how slowly do you turn on a switch?

[M2dude]

The reason that #4 engine was limited to 88% N1 on take-off was an interesting one, down to something known as 'foldover effect'. This was discovered during pre-entry into service trials in 1975, when quite moderate levels of first stage LP compressor vibrations were experienced at take-off, but on #4 engine only. Investigations revealed that the vibrations were as the result of vorticies swirling into #4 intake, in an anti-clockwise direction, coming off the R/H wing leading edge. As the engine rotated clockwise (viewed from the front) these vorticies struck the blades edgewise, in the opposite DOR, thus setting up these vibrations. The vorticies were as a result of this 'foldover effect', where the drooping leading edge of the wing slightly shielded the streamtube flowing into the engine intake. #1 engine experienced identical vorticies, but this time, due to coming off of the L/H wing were in a clockwise direction, the same as the engine, so were of little consequence. It was found that by about 60 KTS the vorticies had diminished to the extent that the N1 limit could be automatically removed. Just reducing N1 on it's own was not really enough however; some of this distorted airflow also entered the air intake through the aux' inlet door (A free floating inward opening door that was set into the spill door at the floor of the intake. It was only aerodynamically operated). The only way of reducing this part of the problem was to mechanically limit the opening angle of the aux' inlet door, which left the intake slightly choked at take off power. (The aux' inlet door was purely aerodynamically operated, and diff' pressure completely it by Mach 0.93).

[Nick Thomas]

On the ITVV Concorde DVD the Captain explains that during the cruise climb at mach 2 the auto throttles were armed and would be used as required. Then during descent the throttles were gradually pulled back whilst the autopilot was given an IAS of I think 350 knots. Therefore the plane would have to descend to maintain that speed. He explained that the power settings were chosen to ensure that there was sufficent cooling etc.
My query is if an autoland was to be undertaken was the auto throttle system able to maintain the required landing speed or would the pilot have to manage the throttles? I guess that decreasing or increasing the pitch to control speed when on the glide slope would not be a good idea.
Thanks again
Nick

[EXWOK]

Approach handling was an interesting exercise - being so far down the back of the drag curve (over 100kts below best L/D) very accurate thrust handling was required.

The autothrottle was always used for approach if servicable, except for a two-engined approach, and was absolutely excellent. There were two, operating in parallel, and if the speed was more than a couple of knots out for more than a few seconds it was unusual. In IAS ACQ mode there was an active input from the INS which tracked grounspeed and so enabled anticipatory throttle movements during wind changes - if an autoland runway was available the preferred method of dealing with an approach likely to experience windshear was to carry out an autoland. (I think I speak for everyone, though, if I express a preference for the just going somewhere else option).

In Supercruise one autothrottle only was rearmed if the associated autopilot was engaged - it wasn't active but was available to cater for sudden drops in temperature which could cause unpleasant sudden high rates of climb if the temp shear was sufficient.

The rest of the flight - basically manual thrust, usually with the throttles fully forward.

Maybe one day we'll start making aeroplanes with such sophisticated systems again...........there's still lots that hasn't been hinted at on this thread

[Biggles78]

there's still lots that hasn't been hinted at on this thread
EXWOK, more than happy to take a hint........PLEASE! and welcome to this gem of a thread.

With the FBW, was there any feedback built into the yoke? The Airbus with it's "joystick" has, I believe, no feel unlike a Flight Sim force feedback one.
If there was a yoke movement on one side did the other side mirror the movement or like the Airbus did the sidestick play dead?

M2, it appears the tailwheel was, so far, the only "fault" in an otherwise extreme machine. Were there any other items like the tailwheel that were unworthy to be in her?

Does anyone have a tech drawing of the "sliding seals" used in the hydraulics. I have trouble visualising something that could withstand the 4,000psi pressure. Why was such a high pressure used? After all the control surfaces couldn't have required that much input to effect an authority movement. I understand it was also a special fluid that was used. Was this because of the pressure it was under or the temperature extremes?

[4greens!]

This is a wonderful thread about the most superlative aircraft ever built.We were once fortunate enough to be given seats 1 C&D (I would have liked to see a roll-call of their previous occupants) and with regard to the hugely knowledgeable points made about fuel transfer and trim, during boarding and in flight the sound of fuel pumping was often louder than the Olympus music.During a visit to the FD the captain verified that these were the noisiest rows in the cabin despite their often being used by royalty and REAL A-listers. Many thanks for sharing your deep insights into this machine.

[EXWOK]

Biggles:

Yep, there was feedback. In this respect, the implementation of FBW had a rather different philosophy to FBW Airbus'.

Below 200kts it was basically a spring feedback, above that speed it was achieved throught the feel system, not entirely unlike conventional aircraft.

Of course, the feel was tempered also by the autostab system, which didn't feedback through the yoke, but did make control surface inputs. A basic analogy is to imagine a yaw damper, but on all three axes. (It was of course rather more sophisticated, especially in pitch).

During airtests we would fly portions of the supersonic accel without autostabs and it was then very obvious exactly how much input was being made - great care was needed to remain within sensible bank angles in the low supersonic regime.

Also - watch a video of the control surfaces in the latter stages of the approach and landing - all those rapid deflections are the autostabs overlaid on the pilot's inputs. One has to remember that the aircraft is effectively statically unstable in pitch at approach speeds, so a pilot up-elevator input would soon be followed by a countering autostab elevon-down to contain the tendency to keep pitching up, and vice-versa. Gusts affecting the IAS would also create an input.

All of which means the basic spring feel below 200kts is not as basic as it sounds.....and in normal signalling modes (ie FBW and autostab active) the amazing thing is that the aircraft handled beautifully through an 1100kt speed range.

If you look at a picture of the flightdeck you will see a row of 14 white switches full width of the fwd edge of the overhead panel. These were autostab pitch/roll/yaw, feel pitch/roll/yaw left and right systems and the two pitch trim switches (which played a big part in the low-speed protection).

If any of them dropped out you could be sure that the first thing the nearest pilot would do would be to try to re-engage them, as it made for a vastly more pleasant life.

[EXWOK]

Also, regarding the 4000psi pressure adopted - the control surfaces most definitely did need powerful actuators; as you now know they were very active, especially on approach and transonic, and as well as IASs of up to 530kts you have all the lever arm changes brought by shifting centres of pressure over the surfaces caused by shockwave movements.

If you want to fly supersonic, frontal area is everything so 4000psi also has the benefit of keeping the PFCU cross-section down.

I'm sure M2Dude will be able to give a better explanation of this aspect - it's nearly seven years since I flew the beast (that's depressing) and it's hard enough to remember detail of the flying bits, let alone the complex engineering aspects.

[EXWOK]

Oh yeah - finally:

As for my allusion to other interesting areas of this aeroplane, we've all got our favourite examples - but I for one will see how the thread progresses naturally before I start proselytising about my favourite bits. :)

[M2dude]

Biggles78
M2, it appears the tailwheel was, so far, the only "fault" in an otherwise extreme machine. Were there any other items like the tailwheel that were unworthy to be in her?
Does anyone have a tech drawing of the "sliding seals" used in the hydraulics. I have trouble visualising something that could withstand the 4,000psi pressure. Why was such a high pressure used? After all the control surfaces couldn't have required that much input to effect an authority movement. I understand it was also a special fluid that was used. Was this because of the pressure it was under or the temperature extremes?
The tailwheel design really was the one exception in poor design terms, but I'm sure that if the aircraft was doing what she should be doing right now, (you know routinely flying across the Atlantic and beyond, instead of languishing in museums), modifications would have finally put this particular malady to bed). In design terms, the rest of the aircraft was nothing short of a flying work of art, a masterpiece. Having said that though, personally I would rather that four rather than three hydraulic systems had been used. Originally there were four systems in the design, but the RED system was deleted, as it was felt to be superfluous. My own view is that this particular decision was total poppycock. Oh, and Green, Blue and Yellow hydraulic systems was something else that Airbus copied from Concorde.... although we ourselves pinched that idea off of the Comet :p).
As far as the hydraulic expansion joints go, I will scour around and see if I can find a diagram for you. Try and picture two titanium (or stainless) tubes, on inside the other, with a sealed chamber being formed at the join. Inside this chamber were multiple lands fitted with special viton GLT seals. They did work incredibly well, although occasionally one of the seals gave out, and things got wet, VERY WET.
As far as the 4000 PSI hydraulic system, as EXWOK quite rightly pointed out, the loading on the flying control surfaces were immense throughout the whole flight envelope. (Picture alone just the T/O from JFK RWY 31L, where the aircraft is tightly turning and the gear retracting, all at the same time). As well as the flying controls and landing gear, you also had the droop nose to consider, four variable engine intakes as well as a couple of hydraulically operated fuel pumps. Oh, and in emergencies, a hydraulically driven 40 KVA generator too. The reason that 4000 PSI was chosen was that if a large amount of hydraulic 'work' was to be done, the only way to keep the size of jacks and actuators to a reasonable size/weight was to increase the system pressure by 25% from the normal 3000 PSI. (On the A380 they've gone a step further and gone for 5000 PSI, saving them over a tonne on the weight of the aircraft).
Concorde used a special hydraulic fluid, Chevron M2V. This is a mineral based fluid, as opposed to the ester based Skydrol, used by the subsonics. The reason that we went for a different fluid was a simple one; Skydrol is rubbish at the high temperatures that Concorde operated at, no good at all in fact, so we needed something better and in M2V we found the PERFECT fluid. As an aside, unlike Skydrol, that attacks paintwork, certain rubber seals, skin, EYES etc., M2V is completely harmless, wash your hair in it. (I did, several times when we had leaks. Thinking about it, maybe THAT is why my hair is such a diminished asset :ugh:

EXWOK
It's so great having another of my pilot friends diving in to this post, welcome welcome :)
I remember the Mech' Signalling part of the air tests, my lunch has just finished coming back up thank you. :\ (for interest chaps and chapesses, with mechanical signalling, using just the conventional control runs under the floor, there was no auto-stabilisation).

The artificialfeel system worked incredibly well I thought, I always found it curious that the peak load law in the computer was at the transonic rather that the supersonic speed range. It was explained to me long ago that this was because the controls really are at their most sensitive here, but at high Mach numbers are partially 'stalled out', due to shockwave movements along the surfaces, and were therefore less effective. (For this reason I was told, the inner elevons were so critical for supersonic control, being the most effective of all elevons at high speed).

To all, I forgot to mention in my previous post regarding the engine failure in G-BOAF in 1980; I remember an FAA surveyor, who was taking a look at the carnage within the engine bay, saying that in his opinion, no other aircraft in the world could have survived the intensity of the titanium fire that ensued. Analysis showed that the fire was successfully extinguished, possibly at the first shot of the fire bottle. This was a testament to the way that the Concorde engine bay could be completely 'locked down' when the fire handle was pulled, as well as to the way that the whole engine installation was technically encased in armour plate. To put all this in context, acording to Rolls Royce a titanium fire, once it takes hold, can destroy the compressor of a jet engine in four seconds.


Dude :O

[Tim00]

I'm just an interested non-pilot bystander, & hope it's OK to post here.
Thank you all for this truly fascinating information. I've a question arising from watching the ITVV DVDs:

Having two pilots obviously gives some options if one becomes ill or incapacitated, but how were things handled if the FE became unable to perform his duties? Did the FO take over, & how familiar were the pilots with the FE's duties - could either pilot do the FE's job in full, or was it limited to some subset such as required for a diversion/landing etc. I assume this kind of thing was practised in the simulator regularly?

I note (unless I've misunderstood) that there was some presetting of the load limit fuel transfer system, so that the pilots could initiate a CofG movement for descent if required.
Thanks!

[M2dude]

MEMORIES
Like so many in the Concorde family, I have millions, I'd like to share a couple here. I remember at Fairford in mid 1974, a CAA test pilot (I honestly forget the gentleman's name) was taking the British pre-production A/C 101 (G-AXDN) for a special test flight. The reason that this flight was so special was that for the first time, the CAA were going to do an acceptance flight trial of the brand new digital air intake system. This revolutionary system had been retro fitted to 101 barely a year earlier, and being a brand new (and totally unique, in electronics terms) system had been plagued with teething troubles. It was quite reasonable for any airworthiness authority to have serious misgivings about any system that was going to wave great big metal lumps around in front of the engine compressor face, and that if only a few degrees out from the commanded position out could cause the engine to 'backfire' etc.
So anyway, 101 took off and disappeared into the very blue sky and we waited, and waited, AND WAITED. (I'd only left the RAF and joined the project a few months previously, and did not want my new association with this amazing aircraft to end). I was biting my nails, drinking coffee, losing my hair... (without the help of M2V :ugh:). Anyway after about 2 1/2 hours the aircraft returned to Fairford, and everybody crowds around the crew for the debrief. A very stern faced CAA pilot looked at us all, broke into a grin and said "as far as I'm concerned gentlemen, you've got yourselves an airliner". At that point the room was a study of total happiness, blessed relief, and a need to go to the loo..... But from my point of view, I will remember those words forever.
101, which now resides at the Imperial War Museum Duxford was the fastest Concorde ever. She achieved Mach 2.23, which was an incredible irony, as Concorde can trace a large part of it's developement history back to the BAC 223, proposed SST.
As far as flying memories go, I just don't know where to start; My first ever Concorde flight was in November 1976, out of Fairford on a pre-delivery test flight on G-BOAD. (Now sadly bobbing up and down on the Hudson, next to the USS Intrepid). I was staggered how fast and high we flew (Mach 2.08, FL580). Most of my flying up to that date had been in C-130's in the RAF, at around 340 KTS and FL300; Concorde also being infinately quiter in flight than the good old Herc'. I remember a BA QA guy showing me how I could touch the skin of the aircraft at Mach 2 (You reached behind a door busstle flap, moved your hand through some insulation until you felt bare metal). OUCH!! it was hot, very hot.
But I think one of my most memorable flight memories was aboard G-BOAG, (now residing in the Boeing Museum of Flight in Seattle) returning from BKK, having stopped off to refuel in BAH. We were forced to fly subsonic over Saudi, and got caught in this amazing electrical storm, There was St Elmo's fire cracking and bubbling all over the visor panels, but just as incredible was the long blue electrical discharge coming off of the nose probe; it seemed to extend about 50' in front of the aircraft. The crime was, none of us on the F/D had a camera. Every time I bump into the captain on that day (are you reading this Ian?), we go back to remonissing about that incredible flight. Also, later on the same sector, after we had decelerated to subsonic cruise again, this time flying up the Adriatic, we had another fascinating sight: It was getting quite dark now, and here we were, travelling at Mach 0.95 at FL290, when above us was all this Mach 0.8 ish traffic at around FL330-350. All we could see were all these navigation and ant-coll' lights above us, seemingly travelling backwards. It was quite a sight. On the original BAH-BKK sector a week earlier, we flew through some of the coldest air I'd ever seen; The air was at ISA -25, and at Mach 2 our TAT was only about 85 deg's C. (You could feel the difference too; the cabin windows felt only warm-ish to the touch). The upside also of all this was that your fuel burn was much lower than usual. (The only downside of course is that your TAS is a little lower). Rolls Royce did some analysis on the flight, and were amazed at how well the propulsion systems coped with some of the temperature sheers that we encountered, sometimes 4 to 5 deg's/second. They said that the prototype AFCS had been defeated by rises of only 0.25 deg's/second ).
Not meaning to go off onto a (yet another) tangent; Negative temperature shears, very common at lower lattidudes, always plagued the development aircraft; you would suddenly accelerate, and in the case of a severe shear, would accelerate and accelerate!! (Your Mach number, quite naturaly, suddenly increased with the falling temperature of course, but because of the powerplant suddenly hitting an area of hyper-efficiencey, the A/C would physically accelerate rapidly, way beyond Mmo). Many modifications were tried to mitigate the effects of severe shears, in the end a clever change to the intake control unit software fixed it. (Thanks to this change the production series A/C would not be capable of level flight Mach numbers of any more than Mach 2.13, remembering that Mmo was set at 2.04).
There was one lovely story, involving the Shah of Iran, having one of MANY flights in a developmment aircraft. The aircraft encounterd quite a hefty series of temperature shears that plagued havoc with some Iranian F4's that were attempting to close on the Concorde, to act as an escort for the Shah. (or so the strory goes). I'm still trying to picture these F4's, on full afterburner trying to get close to a Concorde cruising away on dry power). It is said that the F4's were having such difficulties, due to their relatively crude powerplant, coping with the temperature changes, that the Concorde was ordered to slow down, 'so the escorting F4's could catch up'!! True or not, it is part of Concorde folklore.

Dude :O

[EXWOK]

Hi M2Dude - keep it coming! I missed all this stuff from the early days......

Tim00 - good question, and very relevant.

It takes a lot to incapacitate a Flight Engineer - beer, cigars and scary women were no issue - they were definitely the most relaible part of the operation. (And arguably the least attractive.....)

If the unthinkable happened the First Officer would find himself on the FE's seat. We practised it less often than you might think, but thought about it a great deal. Especially the fuel system management.

Which brings me to your second point - yes, there was a preset for the 'automatic' fuel transfer system, although that wasn't the mechanism used for the pilots to 'take control' of the CG. The critical thing was to be able to get the CG forward if a rapid decel had to be made - for this reason there was an override switch above the First Officer which used various pumps and valves to txfr fwds - primarily by txfring from tank 11. It would be used in various recall checklists (supersonic 4-engine flameout and Continuous Ssurge at M>1.3 seem to register from the dim past) until the FE was able to take over the txfr system himself.

I didn't ever need it - in the surges I encountered the FE was always ready to manage the txfr before we needed the override.

Oooooooh!!!! There's a new topic for someone: Surges.

Theoretically the correct checklist to call for was the "Continuous Engine surge above M 1.3 Conditional Procedure, please". In reality the call was always much more succinct.

Monosyllabic, in fact................

I'm off to the pub, but I bet Bellerophon can speak with erudition on the operational aspects, and if M2Dude is who I suspect he is, I KNOW he'll be able to cover the technical aspects in great depth!

WOK

[Jo90]

Fascinating thread. Please keep it going.

I see from photo in post 66 that pitch attitude at Mach 2 was about 4 nu. Could you say what attitudes were normal at other stages of flight?

I think I read that initial rotation was to a pre-computed attitude which allowed for simultaneous climb and acceleration. What was the speed typically when re-heat was cancelled at I assume 1000 agl?

Jo

[ChristiaanJ]

M2dude,

Thanks for bringing up the story of the temperature shears at low latitudes, saves me some explaining !

The phenomenon was not really "discovered" until the route proving started.
As you say, it meant abrupt changes in Mach and Tt.
Since the pitch autopilot in, say, 'Mach Hold', had only one way to cope with those changes : pitching up or pitching down, this resulted in abrupt climb and descent manoeuvres that were totally inacceptable.

It was not only fixed by modifiying the intake controls.... !
It also led to a fairly major mod in the AFCS, by bringing the auto-throttle into the loop.
Instead of letting the pitch A/P take the aircraft into a zoom climb to try and stay within the "speed limits", it woold be the autothrottle pulling the throttles back.
After a fair amount of flight tests, this became the final form of the 'Max Cruise' mode.

I know... I should have kept a diary.
All this happened 35 years ago, so I can't put exact dates, or even specific aircraft, into the story. At least I still have some Concorde doc, that at times allows me to refresh my memory.

But one thing stayed in my memory over the years ...

The initial A/P+A/T 'Max Cruise' mod meant a major modification of the autothrottle computers. One of the circuit boards in particular was totally "butchered" on-site (Fairford), with well over a hundred track cuts and new wire links, not to mention the number of component changes (to give an idea to the 'experts', these were double-sided PCBs of about 15x20cm).

We got the job done (4 boards : 2 boards per computer, 2 computers), got the computers tested and on the aircraft. Knowing full well how easy it was to introduce faults and problems during such a modification (a dud solder joint could be enough), we expected to see them back within days, or at least within a few flights.

Well..... those computers left the lab with each about a thousand hours "on the clock" (they have little elapsed-time counters that indicated hours under power, NOT flight hours).
The first time we saw them back (for a minor mod, not a fault), both clocks showed over 10,000 hours !

Ah, those were the days :8

CJ

[ChristiaanJ]

There were questions about the JFK 31L take-off.

I think this is it....

YouTube - Concorde British Airways take-off (http://www.youtube.com/watch?v=c_0AK_OwagE&NR=1)

CJ

PS The YouTube legend says last t/o from Heathrow, obviously wrong.

[Nick Thomas]

As Concorde was in reality the first and only successful SST; a lot of useful information must have been gained during the flight testing phase. Were there any plans to incorporate any updates/modifications based on leasons learnt into later production models(if there of course had been more orders)?
Whilst typing the above I was reminded of something I read many years ago; that MI6 managed to pass slightly doctored "blueprints" to the Russians and that was the reason that "Concordski" was such a failure. I have always assumed that this was an "urban myth".
Regards
Nick

[EXWOK]

Always more nose up than a conventional a/c.

As you note, about 4 in the CRZ. About 10.5 degs on approach.

As part of the performance calcs we calculated a 'theta 2' value of pitch. This was bugged on the ADI with a little bug controlled from a thumbwheel on the yoke - at all speeds very accurate pitch control was required, hance this device and the ADI being calibrated in 1 degree increments.

Theta 2 was attitude reqd to obtain V2 in the first segment with one engine out, i.e. the target attitude if an engine failed after V1. Once the gear was up (second segment) one would pitch up a little to hold V2 until 600ft then start initial accel.

On all engines, one held it until 250kts then pitched up to maintain that speed. You'd typically reach it before passing over the M25 departing LHR to the West.

In all cases, as soon as SID altitude or noise abatement limits had been reached you went to the barber's pole asap (400kts initially) as this was where best performance lay.

[Coffin Dodger]

Sorry, haven't worked out how to embed videos. Stunning departure!

YouTube - Concorde: Last Takeoff From JFK Airport With Live Commentary (http://www.youtube.com/watch?v=qr8s4zbd39M)

[Landroger]

First of all, many, many thanks to our four main sources of Concorde 'nectar'; M2Dude, ChristiaanJ, Bellerophon and Exwok. Their input, each from a slightly different viewpoint, is absolutely captivating. As fascinating as the lady herself.

The initial A/P+A/T 'Max Cruise' mod meant a major modification of the autothrottle computers. One of the circuit boards in particular was totally "butchered" on-site (Fairford), with well over a hundred track cuts and new wire links, not to mention the number of component changes (to give an idea to the 'experts', these were double-sided PCBs of about 15x20cm).


Christiaan rang an awful lot of bells with his description of some of the electronics - it was very, very similar to the stuff I used to work on, back in the early days of production CT Scanners. Cut tracks and wire links were the 'staff of life' and the stuff of nightmare. :eek: Our first minicomputers - to reconstruct the CT image - had 32 kilobytes of memory on four boards, each about 17" square!! My phone has about 2 Gigabytes of memory! Now this was in the late seventies, when Concorde had been flying for a good number of years.

My question, which is a bit of a tilt at windmills, is this; If you had to build Concorde all over again with the same airframe and engines, how much more room, how much lighter and how much more capable would the electronics be if they were made using the latest surface mount, Extremely High Density integrated circuits and microprocessors?

Thanks again everyone, for the best thread I have read on PPRuNe for two years (and there have been some superb ones in that time :))

Roger.

[ChristiaanJ]

As Concorde was in reality the first and only successful SST; a lot of useful information must have been gained during the flight testing phase. Were there any plans to incorporate any updates/modifications based on leasons learnt into later production models(if there of course had been more orders)?Rather than me waffling and doing cut-and-paste, just look here :
Concorde "B" (http://www.concordesst.com/concordeb.html)
Concorde '217' would have been the 'prototype' for the 'B' version. Sadly it never happened.
Whilst typing the above I was reminded of something I read many years ago; that MI6 managed to pass slightly doctored "blueprints" to the Russians and that was the reason that "Concordski" was such a failure. I have always assumed that this was an "urban myth".Like all urban myths, there's some truth in that.
Yes, there was some industrial espionage, and a Russian or two was arrested with microfilms of blueprints and a few components, in the best James Bond style (this was in France, BTW...).

Some "duff gen" may have been passed as well... although the main reason the Concordski failed was that they didn't really get some of the vital stuff sorted, with the subtlety of the wing shape and the intake controls being only a few of the examples.

To my mind, the best story (urban legend or not) was that a Russian got caught scraping tyre deposits off the runway after a few accelerate/stop tests. The sample was duly sent to Russia, mixed with chewing gum and a few other ingredients, and a certain amount of time is reputed to have been wasted tryng to reproduce the 'formula"..... :ugh:

Legend also has it, that the Russians at one point quite seriously inquired if they could buy the license to the intake control system.
Since at the time it would still have had quite significant military use as well, the answer was a very firm "njet" !

CJ

[ChristiaanJ]

Coffin Dodger,
Thanks for your link to the video of the last JFK takeoff, with the full comentary.

CJ

[M2dude]

ChristiaanJ
aaah yes, Max Climb/Max Cruise modes. I'd not forgotten this my friend, I was going to say a few words about that in a future post, but maybe we can do that now. (And I'd love to hear more of your comments on this here too, ChristiaanJ). The intake and autopilot modifications were in a way complimentary it's true, but really dealt with separate problems, at least in my view:
The intake control unit software change (a change to the control law that limited engine N1 as a function of intake local Mach number, Mo, and inlet total temperature, T1) was able to put an absolute limit on aircraft achievable Mach number during Mmo overshoots, but it would not PREVENT Mmo overshoots occurring altogether, it was more of a safety brake. This particular overspeed problem manifested itself well before route proving, and in fact the intake system 'fix' resulted in the Thrust Auto Reduce System being deleted, electronic control boxes and all. The TAR system was fitted on all development aircraft equiped with the digital intake system, and it tried (in vain) to limit extreme Mach overshoots. The production aircraft retained the TAR wiring and locked out circuit breakers, as well as two vacant spaces on the electronic racks. The prime reason for all these efforts were that some of the rapid excessive Mach overshoots quite often drove the intake into surge; the modification to this N1 limiter control enabled engine mass flow to be controlled in such a way that these surges could be prevented during temperature shears. The aircraft Mach limit was an extremely useful fringe benefit.
The AFCS mode change from what was Max Op and Max Op Soft (always loved that name) to Max Climb/Max Cruise was at a stroke able to deal with the regular Mmo overspeeds that kept on occuring during, as you say, the route proving trials of 1975, when British aircraft G-BOAC and the French aircrfraft F-BTSD carried out pre entry into service evaluation flights, SD sadly was the aircraft that was tragically lost at Gonez in July 2000). The Max Climb/Max Cruise AFCS mode combo is a mode like no other that I've personally seen before or since anywhere, (it for instance resulted an elsewhere taboo; an autopilot and an autothrotte working together IN A SPEED MODE).
This problem encountered primarily at lower lattitudes, (for example, G-BOAC doing route proving flights out of Singapore), occurring initially as the aircraft reached Mach 2. It was termed 'the insurmountable problem', but the AFCS designers (such as ChristiaanJ) fortunately did not have 'insurmountable problems' in their vocabulary. The issue was that the aircraft would have been climbing rapidly at Vmo of 530 KTS, with throttles at the gate as usual, At exactly 50,189' we hit what was known as 'the corner point' in the flight envelope, where 530 KTS IAS equated to Mach 2 exactly. Max Op mode would then 'let go' of the Vmo segment, and try and control the aircraft to Mach 2. (As the aircraft climbed, Vmo itself would progreesively decrease in order to equate to Mmo, or 2.04 Mach). But in very cold conditions, the aircraft still 'wanting' to accelerate, and the simple Max Op/Max Op Soft modes just could not cope with gentle pitch changes alone. The problem became even bigger during the cruise/climb when severe temperature shears occured, and routinely regular Mmo exceedences occured. Something had to be done, and something WAS done and how; enter Max Climb/Max Cruise. It was really a classic piece of design, where the aircraft would do the initial supersonic climb in Max Climb mode. This mode itself was relatively simple, in that it was more or less a Vmo -Vc hold mode. That meant that the difference at selection between indicated airspeed, Vc and Vmo would be maintained, with a vernier datum adjust to this being available. In practice this mode was selected pretty much at Vmo, so datum adjusting was not always required. Now comes the clever part; the autothrottle, this would operate in standy mode at this point, just waiting there doing nothing, with the throttles at maximum as before. So the aircraft would now climb as Vmo increased to 530 KTS, and then following a now constant Vmo of 530 KTS until the magic 'corner point' (51, 189' remember). Now all hell would break loose; the mode would automatically change to Max Cruise, the autothrottle would also be automaically selected to Mach Hold mode (initially datumed here to Mach 2) and the throttles would retard, attempting to hold this Mach 2 datum, and the autopilot is commands a 'fly up' signal, over a 20 second lag period to 600'/minute. Now comes an even cleverer (?) part; the autothrottle Mach Hold datum is gradually increased over a 100 second period towards Mach 2.02, and so in stable conditions the throttles would now gradually increase again until they once more reach the maximum limit. At this point, the autothrottles now come out of Mach Hold mode and back into the waiting in the wings standby mode. The autopilot would now cancel it's 600' fly up, demand, returning to a datum of Mach 2. There was a little more complexity built in also, where the difference between the 'commanded' and actual vertical speeds offset the autoplilot Mach 2 datum. This would apply whether the autothrottle had cut in (+600'/min demand) or with the throttles back at maximum (0'/minute demand. A positive climb error tweaked the cruise Mach up slightly, a negative error (eg. in a turn) the converse was true. The effect of all of this complexity was that the aircraft itself could 'scan' until it settled at a point where the throttles could be at maximum, and the speed between Mach 2 and 2.02. On the North Atlantic, with warmer ISA temperatures, there was usually just the initial routine with the autothrottle as you hit the corner point. However at lower lattitudes (eg. LHR BGI) there could be a few initial autothrottle intercepts before things settled down. This whole incredible routine completely took care of the insurmountable problem, a problem that was shown not only to be insurmountable, but was put to bed forever, by people like ChristiaanJ.
I hope that my explanation here does not sound too much like gibberish.

EXWOK
I think you've guessed right as far as my identity goes; it's great that it's not just Concorde pilots I can bore the socks off now :p
PS. I bet the ex-SEOs LOVED your comments :D

Dude :O

[ChristiaanJ]

Cut tracks and wire links were the 'staff of life' and the stuff of nightmare. :eek: Our first minicomputers - to reconstruct the CT image - had 32 kilobytes of memory on four boards, each about 17" square!!
Not the autothrottle board in question, but one of the same size and technology.

http://img.photobucket.com/albums/v324/ChristiaanJ/11280007w-1.jpg

You were already working with advanced stuff, Roger...
The notorious AICU (air intake control unit) had something like 2 kilobit RAM, and 42 512-bit PROMs on 5 boards. That's a grand total of 2688 bytes of program storage, look-up tables, etc.

My question, which is a bit of a tilt at windmills, is this; If you had to build Concorde all over again with the same airframe and engines, how much more room, how much lighter and how much more capable would the electronics be if they were made using the latest surface mount, Extremely High Density integrated circuits and microprocessors?How much lighter?
I can only make a stab in the dark, but ... I would say (mentally totting up all the electronics boxes and weighing them) the electronics fit weighed in the order of a couple of tons (maybe somebody has a closer figure?). So on an aircraft of 185T TOW, even if you could bring that down to a quarter of that weight, you'd gain less than 1%.

How much more capable?
Concorde did fine, so what more capability do you want ? :rolleyes:
Seriously, you would have a glass cockpit, which would make nav etc. easier.
And of course you would be able to get rid of the flight engineer and his panel, so that would be a few more hundred kilos.... beer and all.
Where an electronics update would make a difference would be in the amount of aircraft wiring. In the olden days, every single signal had its own bit of wire... now everything passes via digital 'buses', where dozens of signals are transmitted over a single twisted pair.

For the computer and electronics buffs among you : it's the difference between the old Centronics printer interface, where every signal has its own wire, and todays USB.

CJ

[M2dude]

Landroger
My question, which is a bit of a tilt at windmills, is this; If you had to build Concorde all over again with the same airframe and engines, how much more room, how much lighter and how much more capable would the electronics be if they were made using the latest surface mount, Extremely High Density integrated circuits and microprocessors?
Wow, that's a very interesting question, do you mind if I give it a tiny slant of my own, namely system distribution?
Concorde had an ENORMOUS number of electronic control boxes, for example the powerplant alone used TWENTY SIX rather heavy computers and control units, all of which used conventional 1970's manufacturing technology. (Although the intake box was a work of art; rows and rows of double sided PCBs completely crammed with TTL chips). This whole entourage literally weighed a ton, and could be easily replaced by four modern relatively light units with multiple redundancy built in). Even the AFCS used a total of sixteen heavy boxes, again these could be reduced to three, for a modern triple channel system. The three INUs and two ADCs (Very heavy units all) could be replaced with a single ADIRU and SAARU. To complete the package two FMCs (which would also furnish autothrottle functions) could be added. A massive weight saving could be made on the FBW system, by removing the bulky mechanical components (the feel and relay jacks as well as all the mechanical control runs and the massive mixing unit under the rear floor). Careful design could easily provide a full authority triplex or quadraplex FBW system. The current controls could be replaced with either an Airbus or Boeing type system, using either a sidestick (Airbus) or retain a conventional control column system (B777/787) using electric backdrive. The pilots can decide this one. A modern databus system would also be required for providing communication and redundancy; ARINC 629 would be MY preferred choice). The wholesale replacement of the various control units and computers, not to forget miles of wiring, as well as some bulky mechanical hardware would in my view save around 3 tonnes or more in weight alone. A now far more accurate control of aircraft systems would also bring major efficiency savings. As far as saving space, that possibly free up a couple of seat rows, if it were all done properly.
We can all dream I suppose :)

Dude :O

[Bellerophon]

M2dude

...The Max Climb/Max Cruise AFCS mode combo is a mode like no other that I've personally seen before or since anywhere...

True.

On descent, with the throttles at idle, it also worked beautifully as a MAX DESC mode

It was a very versatile mode. ;)


Best Regards

Bellerophon

[M2dude]

ChristiaanJ
Loved your AICU stuff. Here's an extract from 'The Concorde Air Intake Control System':
The Control Highway
This highway is a uni-directional databus that carries binary data transmitted by the AISU to it's pair of AICU's. The Control Highway effectively comprises of a single wire, that has transmitted along it multiplexed digital data, clock and address. (In reality this is a twisted wire pair). The AICS Control Highway data word comprises of 64 bits, transmitted at a PRF of (at least by modern standards) an extremely pedestrian 35 Kbits/second.
Sounded mouthwatering in the 1970's though, 35 Kbits/sec' is almost NINE KB/sec'!!!!.

Dude :O

[chksix]

That's the era when the space shuttles were built. Excellent thread, I'm checking every day for new replies.

[stilton]

Bellerophon, if I may pick your brain a little further.


In your superb photograph you posted earlier in the Mach 2 Cruise level at FL600 I notice that both RMI'S shown seem to be showing a heading of 230 while the heading on the HSI shows 220 with the annunciation TRUE above the HSI.



Were you operating on TRUE headings in this case as it seems and what was the reason for this ?



I am thinking that the RMI's are showing magnetic headings ?

[Landroger]

Thanks for the detailed replies guys, which pretty much chime with some of what I'd guessed, although it is clear I had 'overestimated' the technology available to you at that time. There was me talking kilobytes and you only had kilobits to work with! :eek:

Your photograph really brings it home Christiaan. What little horrors hid inside those TO5 cans? :ok: Apart from the fact that your board must be brand new - the track cutters and wire linkers hadn't got at it yet! :) What is interesting are the connections - only eight pins, as far as I can tell? We had 15/25/60 pin 'D' connectors or multi path, gold 'edge' connectors at least. :ok:

How much lighter?
I can only make a stab in the dark, but ... I would say (mentally totting up all the electronics boxes and weighing them) the electronics fit weighed in the order of a couple of tons (maybe somebody has a closer figure?). So on an aircraft of 185T TOW, even if you could bring that down to a quarter of that weight, you'd gain less than 1%.


I wasn't quite clear what you meant here Christiaan, 1% of what? Because Dude is talking about serious weight and space saving - which I would expect.

The wholesale replacement of the various control units and computers, not to forget miles of wiring, as well as some bulky mechanical hardware would in my view save around 3 tonnes or more in weight alone. A now far more accurate control of aircraft systems would also bring major efficiency savings. As far as saving space, that possibly free up a couple of seat rows, if it were all done properly.
We can all dream I suppose

We can, indeed dream Dude - I envy you both, your involvement with such a fabulous (in its truest sense) project.

Roger.

[Bellerophon]

stilton

...In your superb photograph ... thank you ... both RMI'S shown seem to be showing a heading of 230 while the heading on the HSI shows 220 with the annunciation TRUE above the HSI...I am thinking that the RMI's are showing magnetic headings ?...

Correct. The RMIs show 230°(M) and the HSI shows 220°(T).


...were you operating on TRUE headings in this case as it seems...

Yes.

The HSI had earlier been selected to show TRUE data, by moving the RAD/INS switch (out of picture) to INS. This changed the data inputs to the HSI from Magnetic to True, but did not affect the data input to the RMI compass cards. The data input to the RMIs was always magnetic, supplied by one of two compass systems; normally #2 compass system fed the Captain’s RMI card.

The red/black flags visible in the VOR RMI indicate that both the VOR stations selected are out of range.

The flags visible on the HSI indicate:


TRUE.......True compass data (not magnetic) is being displayed. (TRUE/MAG)


INS..........An INS (not a VOR) is supplying Nav data to this HSI. (INS/RAD)


1............#1 INS (not #2) is supplying Nav data to this HSI. (1/2)


HDG.........The steering index shows selected heading (not track). (HDG/TRK)


LIN...........The beam bar is displaying linear (not angular) displacement. (LIN/ANG)



... what was the reason for this ?...

When flying long legs over areas of the world with few/no radio facilities, aircraft generally navigate from one Lat/Long waypoint to the next Lat/Long waypoint by using their INS systems, rather than tracking from radio beacon to radio beacon. The North Atlantic Track system is good example of this, as is this route down to BGI. Because there is no useful magnetic/radio information to display in such areas, True (INS) information is usually displayed, which brings with it two main advantages.

Firstly, you get to monitor how well the autopilot is doing, because the beam bar in the HSI should always be centralised if the aircraft is on track.

Secondly, as the aircraft changes course over a waypoint, you get the chance to check the Initial True Track it then takes up corresponds to the ITT pre-calculated on your flight plan. This is an important check (called the “Waypoint Change Drill”) in BA, that you have not mis-programmed the INS waypoints!

This procedure, of navigating in True, is by no means a Concorde procedure, all long range BA aircraft utilise it, and it is in common use in most airlines and aircraft flying long range routes around the World.

Best Regards

Bellerophon

[Nick Thomas]

Going back to my earlier question regarding expansion of the airframe. I have noticed that the BA Concorde paint scheme was slightly different to the rest of the fleet. All other BA aircraft have blue paintwork to the lower third of the fusalage yet all of the Concorde fuselage was painted white. Was this to reflect heat or just a marketing ploy? I have always presumed it was the former.
Thanks
Nick

[G SXTY]

I have been been on Pprune for 10 years now, and this is one of the most fascinating threads I've ever read. Some of the quotes give me goosebumps:

this fuel system really was a study in elegance.
On test flights however, the aircraft would routinely zoom climb to FL 630 . . . . . . the highest recorded Concorde altitude was on one of the French development aircraft, which achieved 68,000'.
The powerplant was as you say truly amazing. We had an, as yet, unmatched engine/intake combination, with a variable primary and secondary nozzles. The variable intake allowed supersonic operation with maximum pressure recovery, minimum aerodynamic drag, as well as extreme operational stability. (Extreme temperature shears, that would have caused surge/unstarts in military installations) were dealt with as a total non event). It's astonishing to believe, but at Mach 2 cruise, the intake provided approximately 63% of the powerplant thrust. It was controlled by the world's first airborne digital control system.
We never had a case of lost pressurisation, ever.
the aircraft handled beautifully through an 1100kt speed range.

And to think that she was designed in the 1960s by men with slide rules and drawing boards. How fitting that the most sophisticated airliner ever built was also by far and away the most beautiful.

Some years ago I had the privilege of meeting Capt. David Rowland (he of the ITVV video fame) at a GAPAN aptitude test day, and it is one of my cherished memories. I recall we spent about 30 seconds discussing my test results, and the remaining 10 minutes chatting about Concorde . . .

Please keep the memories coming guys – as a humble Dash 8 driver, I will always be in awe of the technological marvel which was Concorde.

[ChristiaanJ]

M2dude et al,
I have the rare privilege of actually having one of those rare "secret" air intake computers (AICU) sitting right next to my desk.
The circuit boards are mostly quite neat, with only the odd wire strap here and there.
However, the wiring of the unit itself, between the connectors, is a nightmare.

This is one of the PROM boards from the AICU, with one of the PROMs taken out of its socket. I have more photos, but will have to download those first, if anyone is interested.

http://img.photobucket.com/albums/v324/ChristiaanJ/04100004w.jpg

LandrogerWhat little horrors hid inside those TO5 cans?They're operational amplifiers, one per can!
Don't forget that all the computing in the AFCS computers was analog, not digital!
The vast majority were LM101As, with 741s in non-critical locations, and the odd LM108 for the really hiigh-precision stuff.
Apart from the fact that your board must be brand new - the track cutters and wire linkers hadn't got at it yet!The board is actually a true antique, dating from one of the development aircraft.
We did not always do the kind of "butcher job" I described for the A/T. If there was enough time between major mods, the "firm" would redesign the board(s) and send us a new set, and the old ones would be binned... it made for better reliability. I kept a few as souvenirs.
What is interesting are the connections - only eight pins, as far as I can tell? We had 15/25/60 pin 'D' connectors or multi path, gold 'edge' connectors at leastI see you missed the real connector!
It's the big blue "thing" at the centre of the board, with no less than 80 pins.

This is the back of the card

http://img.photobucket.com/albums/v324/ChristiaanJ/11280008w-1.jpg

This is the central connector closer up

http://img.photobucket.com/albums/v324/ChristiaanJ/11280009w-1.jpg

The idea wasn't bad at first sight.... it allowed stacking three boards on top of each other, so that many signals could pass from one board to another without any intermediate wiring. A small motherboard with a fourth conector would then take certain signals to other stacks, etc.

Another claimed advantage was that it made the board layout easier.

What was learned only gradually was that those connectors were hideously difficult to solder in place, and even more difficult to repair. Concorde was too far "on the way" to redesign the entire AFCS, so we learned to live with them, but the concept was abandoned afterwards.

The central connectors were only used for the analog boards ; the logic boards used more conventional 84-pin connectors on one side.

This is one of the logic boards.

http://img.photobucket.com/albums/v324/ChristiaanJ/12260001w.jpg


Re the weight question, I would say M2dude's answer is a lot better than mine, so ignore my remarks.....
Re the wiring, Concorde had about 300km of it.
IIRC the A380 Flying Hippo, which is vastly bigger, "only" has about 500km of wiring, and it seems a lot of that is the IFE (in-flight entertainment) :ugh:

CJ

[ChristiaanJ]

And to think that she was designed in the 1960s by men with slide rules and drawing boards.Well, of course we did have computers in those days, mostly for the really big number-crunching jobs.
But you're right, nearly all of the mundane day-to-day design was with a slide rule, and pencil-and-paper.

I still remember how in about 1972 we had to start calculating the electric trim computer resistor values to 0.1% (rather than +-1%), so I bought my very first pocket calculator.... little red LED display, just the basic 4 functions. Cost £42, and those were 1972 pounds (what would the equivalent be today?). Luckily I could put it on my expense account ....

CJ

[M2dude]

Nick Thomas
You are right on the button first time, the white paint finish is for heat reflection purposes. (When I worked at Filton/Fairford I remember reading a document showing the difference in 'hot soak' supersonic skin temperatures for white and black paint finishes. I'm afraid I can't remember any figures (it was a couple of million years ago ) but there was quite a surprising difference.

G SXTY
A hearty welcome to this thread, and thank you for your very kind comments; I'm sure I speak for all the Concorde people here when I say that it is quite amazing that so many people, both aviation professionals as well as more 'normal' people are so fascinated by what most of us still regard as the finest aircraft ever to grace the skies. Your comment about 'men with slide rules' is so totally correct; I still remember the No7 & No8 design offices at Filton, these were huge rooms filled with draughtsmen's boards, a horde of designers, all without a single computer in sight.
Dave Rowland is a total gentleman as well as being an extremely knowledgeable flyer too, and I know he (like most of us) would be happy to talk about Concorde until the cows come home.

ChristiaanJ
Aghhhh The dreaded AICU. I'd almost forgotten the innards, as you say the motherboard wiring was a total nightmare (good piece of knitting I seem to remember). As far as the 'secret' bit of the AICU, I think we all know that is a little bit of Concorde mythology, more science museum than secret really. Around ten years ago we had some fairly substantial modifications done to the units, due to component obsolescence. (I seem to remember that some of the components concerned were not only out of production, but only a few hundred examples existed worldwide}. I do remember that the power supply board, resolver demodulator boards as well as a couple of others were replaced with new ones using modern components. The modification did do wonders for component reliability.
The PROM board that you have the photo of reminds me of a really amusing anecdote, told to me by Dr Ted Talbot a while ago. Now Ted is one of the true fathers of the Concorde air intake, an absolute genius as well as being a really pleasant gentleman indeed. I'm pleased to say that when I met him a few months ago, he was still as sharp as ever in his advancing years.
The story goes like this: Much of the Concorde intake development trials were flown out of Tangiers and Casablanca, where cold stratospheric temperatures would be guaranteed. Software changes as a result of the flight trials had to be done in there and 'the field'. The way that you made programmed the PROMS was by 'burning' each individual logic gate with a 9v battery. It was highly specialised, as well as extremely tedious work indeed, as we can all well imagine. Anyway, in while he was in Tangiers with aircraft G-AXDN, Ted had arranged for a rather lovely looking lady to be flown out to do his ROM programming. The HS 125 from Filton landed at Tangiers and taxied in and parked next to Concorde, and all the flight test people were waiting on the tarmac. The door of the 125 opened and out stepped this really leggy lady. 'who's the bint then ?' pipes up a really gritty airframe fitter, in a really broad Bristol accent. Without giving it a thought, Ted chirps 'she's come to blow my proms'. The little fitter grunts, glares at Ted and comes out with 'typical office staff, you get all the ***ing perks'.

[Nick Thomas]

Thanks M2dude and all other aviation professionals for making us "normal" posters so welcome on this thread.
Being a child of the sixties I clearly remember the feeling that we were at the dawn of a new technological age and Concorde and the Apollo project were the outstanding examples of what was possible. Great times.
Am not a computer expert but I have always wondered if the limitations of the 60's hardware meant that the software had to be more elegantly desgined than now?
Having watched the ITVV Concorde DVD, Captain David Rowlands and SEO Roger Bricknell come over as very knowlegable and friendly people. I hope they are both enjoying their retirement.
Thanks again
Nick

[Self Loading Freight]

Thanks from the peanut gallery seconded.

If anyone's looking for a good home for Concorde avionics, perhaps they might consider the National Museum of Computing at Bletchley Park, which has many fine examples of British electronics (LATCC donated an old ATC system) and is making a good fist of curating them.

I know the people there quite well, and would be delighted to put anyone in touch.

R

[Brit312]

A great thread and it only goes to show that you can always learn even about a subject that you thought you knew quite a lot about

As M2Dude described the rearwards transfer of fuel during acceleration was meant to be an automated process but in reality there was a lot of manual input. The first requirement of the F/E was to match the rearwards movement of the C of G to that of the ever increasing Mach number. If this was proving to be no problem he would take over the transfer manually by switching off the pumps on one side of tank 9 or 10 so as to pump only to either tank 5 or 7. This was because if you transferred evenly to these tanks due to their different shape size and position the aircraft would go out of trim laterally so the F/E would pump rearward just to one tank so as to keep the C of G going aft whilst maintaining lateral trim.

Being Concorde nothing was straight forward , which meant that when Tanks 5 and 7 ran out and you started using tanks 6 and 8, their size shape and position,was exactly opposite to that of tanks 5 and 7 so it now required the F/E to pump fuel the opposite way across the ship, using various valves and pumps, so as to keep the aircraft in trim laterally.

All the time he had to maintain the trim so as to keep an elevon trim of ½ deg down, which as fuel was burnt required him to trickle fuel forward from tank 11. On the longer trips such as those to and from BGI the fuel towards the end of cruise became quite low and to stop fuel in the collectors from dropping below 1000kgs each, fuel would be transferred from tank 11 into the collectors until the
C of G had reached it's forward limit at Mach 2.0 of 57.5 %. If then the collectors dropped to 1000kgs the aircraft had to descend to subsonic heights and speed.

Surges

Surges were not an uncommon or common event on Concorde,but when they happened as they usually affected both engines on that side the aircraft would lurch /yaw and everybody on board would know about it as “Her In Doors” would testify to that when glasses full and otherwise ended up in her lap during the meal service when a surge occurred.

The drill required all engines to be throttled to a predetermined position and the intake and engine control switches moved to their other position. If this stopped the surge then the throttles were restored to their cruise power a pair at a time and if no surge re-occured then the aircraft would return to cruise / climb

The crews post surge action was normally to have a cup of tea and light up a cigarette.

In the early days on a flight between London and Bahrain when the aircraft was in supersonic cruise the F/E who was a mature and refined gentleman, had to go to the toilet, which was just behind the front galley, and whilst there the engines surged. He was seen running from the toilet to the flight deck with his trousers around his ankles, which was a hell of shock to his refined nature

Enough for now sorry about the length

[ChristiaanJ]

Aghhhh The dreaded AICU. I'd almost forgotten the innards, as you say the motherboard wiring was a total nightmare (good piece of knitting I seem to remember).Mine is one of the 202 development units, and 'knitting' is too kind... 'kludge' describes it better. I'll post a photo, if you like.
As far as the 'secret' bit of the AICU, I think we all know that is a little bit of Concorde mythology, more science museum than secret really.That myth was amplified substantially by BA removing those "secret" AICUs from the aircraft after the final delivery flights.
The way I understood the story was that they tried to collect as many reasonably reliable spare AICUs for the last few delivery flights, so as not to have to suddenly cancel a flight.
The AICU was right at the top of the list of "unscheduled removals". IIRC the tea maker was second...
Around ten years ago we had some fairly substantial modifications done to the units, due to component obsolescence. (I seem to remember that some of the components concerned were not only out of production, but only a few hundred examples existed worldwide}. I do remember that the power supply board, resolver demodulator boards as well as a couple of others were replaced with new ones using modern components. The modification did do wonders for component reliability.The one I know about is the ADC/DAC board (analog-digital and digital-analog converter board). The supply of either ADCs or DACs ran out literaly worldwide, and the board had to be redesigned, requalified and recertified with more recent components, and a new batch manufactured. The cost, for the replacement of that board alone, came to about 3 million euros.
Much of the Concorde intake development trials were flown out of Tangiers and Casablanca, where cold stratospheric temperatures would be guaranteed.Software changes as a result of the flight trials had to be done in there and 'the field'. The way that you made programmed the PROMS was by 'burning' each individual logic gate with a 9v battery. It was highly specialised, as well as extremely tedious work indeed, as we can all well imagine. Somebody passed me a photo taken at Casablanca of a table full of AICUs waiting to be programmed... of course every software mod had to be programmed into all eight computers!
"... 'burning' each individual logic gate with a 9v battery." I believe you, thousands wouldn't... Didn't you have at least some sort of programming unit?
I went through a similar exercise around 1976, but at that time at least we had a programming "suitcase", that let you copy the original in RAM, modifiy bit-by-bit with a keyboard, then 'burn' the PROM (or EPROM, by then) 'automatically'. Still took half the night....

Funny in a way how these things have stuck in our memories... But then, yes, Concorde was unique.
I've said this elsewhere, but I don't mind repeating it... in those days, there were two programmes to be part of. One was Apollo, the other was Concorde. And I've had the chance to be part of one of them.

CJ

[DozyWannabe]

Any magnetic core memory in any of those systems?

[galaxy flyer]

CJ

Quite right on the two projects of the Sixties. Many of the engineers on Apollo were ex-Avro Arrow types. The shame is that these projects could not get off the ground (no pun intended) today, even with modern technology. Just a "relofted" (to use a nautical term) Concorde would be a marvelous machine. Politics, environmental regs and NIMBYism would kill anything like it.

I was speaking with a seat mate on an airliner who happened to be a civil engineer. As a young man, he had worked on the US Interstate Highway system, said it could never be done today and widening and improving the one that exists is very hard to approve.

Mach2dude

How was takeoff performance calculated? Was it very different from subsonic jets and how did Vzf fit in?


GF

[Landroger]

Ah now, those boards are actually very good looking boards. I particularly like the PROM board and although I know about the programming of those, it is only at third hand. I certainly had to install many of those PROMS that had been specially 'burned' in Milwaukee, to overcome a particular problem.

I'm a bit embarrassed about missing that multi pin socket on the AICU board. :O I somehow thought it was a specific function chip or a development test socket. Some of those used to appear and remained on some of our boards.

I'm not surprised about the massive cost of replacing certain boards in the later years. Some of those components would have been made of unobtainium long before the millenium. And I just noticed DozyWannabe's question about core memory. I guess it would have been core, because the 8Kb memory boards I spoke about, from the early CT Scanners, were Data General core memory, with a cycle time of 800usec. :eek: Although with four way interleaving, we could get that down to the read cycle time of 200usec!! :ok:

I freely admit I am staggered at how capable were Concorde's electronics - indeed how capable was the whole aeroplane - despite their rather ..... fundamental nature. :uhoh: My respect for everyone involved in the project increases with every post to this thread. :ok:

Roger.

[ChristiaanJ]

Any magnetic core memory in any of those systems?I can't be positive about the INS (inertial nav system).
The prototypes used a SAGEM/Ferranti system, replaced by a Litton system on the preprods, then Delco on the production aircraft.
There may have been magnetic core in the prototype INS.

As to the AICS (air intakes) and AFCS (automatic flight control), the answer is a definite NO. The AICUs used PROMs (fuse type, not EPROM) and the AFCS was entirely analog.

Some of the systems were even more 'antique'...

The ADC (air data computer) for instance was still largely electro-mechanical.

And those nifty NAV and COMM frequency selectors, that always stand out on cockpit pictures... no electronics at all, just a set of wafer switches, and about thirty wires linking them to the transmitters/receivers.

CJ

[ChristiaanJ]

I'm a bit embarrassed about missing that multi pin socket on the AICU board. :O I somehow thought it was a specific function chip or a development test socket. Some of those used to appear and remained on some of our boards.The PROM board is from an AICU, the other board is from an AFCS computer.
Could be Autostab, Lateral Autopilot or Trim, since they all used exactly the same technology, board size, etc.
Looking at the board, I think it's 'Lat A/P' but I can't be certain.
No excuse needed about missing the "central connector" !
It was really a "one-off" feature, invented by Bendix, and abandoned afterwards. I'm not even sure the early A300B AFCS computers, that used much of the Concorde technology, still had them.

I just noticed DozyWannabe's question about core memory. I guess it would have been core... See my post on the subject. I doubt there was any core memory at all in the production aircraft.

CJ

[M2dude]

Brit312
It's so great to have a Flight Engineer's input into this fascinating thread. Your write up on the complexities of managing the fuel system was something else; the best such description I've ever read. I'm still wetting myself with your story about the E/O coming out of the loo with his trolleys around his ankles after a surge. (Not you I hope :=).
The original air intake that was in use for the first few years of airline operation was as you know far more prone to surging than the later modified intake with the thinned and lowered bottom lip, which was far more stable and forgiving. Not only was the 'new' intake more stable, a new leading edge fitted to the rear ramp as part of the same modification, at a stroke cured the very serious ramp vibration issue, that was causing intake structural problems at lower supersonic Mach numbers. The most impressive change of all was a fuel saving of around 1.5 Tonnes per Atlantic crossing, with even bigger improvements in cooler temperatures. A major software change obviously accompanied this modification.

ChristiaanJ
The one I know about is the ADC/DAC board (analog-digital and digital-analog converter board). The supply of either ADCs or DACs ran out literaly worldwide, and the board had to be redesigned, requalified and recertified with more recent components, and a new batch manufactured. The cost, for the replacement of that board alone, came to about 3 million euros
YEP! I remember now, the ADC/DAC board definitely WAS one of the candidates that were modified.
I think you will find the tale about AICUs being removed after museum delivery flights was more urban myth. The only units that I can remember being removed or relocated were the ground power protection unit, the TCAS processors and the radar transceivers. (BA had retrofitted their aircraft with a superb Bendix system a few years earlier, and the same units (with windshear detection re-enabled) are used on other aircraft types).
As far as ferrite cores are concerned, asked by DozyWannabe, the original Delco C1VAC INS fitted to the BA Concorde aircraft did utilise ferrite cores. These were replaced with CMOS EPROMs when a modification was carried out in the early 90's, in which a navigation database was fitted to the units. The fuel consumed and total fuel remaining indicators definitely used a ferrite core memory. These electronic displays used an internal memory in case of power interrupts. As far as AFCS goes, can you check your records? Although, as you say, a completely analog system (with the exception of the ITEM test computers) I seem to remember that the Safety Flight Control Computer used a ferrite core for the flying control strain gauge null memory. I could be wrong here, but I can't remember any other NVM in use at the time.

Galaxy Flyer
I'll leave it to one of my pilot (or F/E) friends to answer this one it that's OK.

Dude :O

[DozyWannabe]

Thank you very much for that information guys. I guess I was trying to work out how the processing work was done, and I suppose from the answers given that other than the INS, it must have been worked out directly on the hardware in realtime. Obviously this was in the decades before von Neumann architecture became ubiquitous, which is why I find the subject so fascinating being a computer scientist (of sorts) myself!

This thread is officially awesome.

[stilton]

Thanks for the reply in regard to operating in TRUE Bellerephon.




At my Airline I have only seen this procedure used before on Polar Routes. I had theorized the reason this was done on the Concorde was because you were crossing Isogonic Lines so rapidly this would minimise heading changes.



So much for my theory !




On another subject entirely was smoking permitted in the Cockpit ?

[RedhillPhil]

Brit312 at 19.39 yesterday has given us a clue.
Surges
3rd paragraph.

[EXWOK]

Galaxy flyer -

TO perf calcs were basically sinilar to a susonic type, which involved a tabulation for each runway in a manual and an A4 proforma.

It was no more complex than a 'Classic' 747, but with a slightly different emphasis - e.g. all take-offs at full, reheated thrust, calculation of fuel transfer or burn off during taxy to achieve TOCG, calculation of timings and thrust setting for runway-specific noise abatement procedures, calculation of theta 2, and planned fuel flow and P7 to set in the take-off monitor (A system designed to aid, but not substitute, the decision of the FE as to whether TO thrust had been achieved, as well as auto selection of contingency power if a failure was detected).

You'd also determine whether a single reheat failure was acceptable that day - the little '3' or '4' bug at the lower left of the engine instruments was set as a visual reminder.

Not sure what you mean by Vzf? No flaps on this machine, so no change. May be a difference of nomenclature. Since there is no defined stalling speed for a delta (by conventional standards we lifted off about 60kts below 'stalling speed') Vzrc was substitued. This is the speed at which full thrust would result in a zero rate of climb. On three engines, this was the basis of the perf calculation, but we also calculated 2-eng Vzrc's gear up and gear down. IIRC they would come out at about 250kts/300kts.

On a transatlantic sector you would do all this and the speeds would invariably be within 5 kts of 160/190/220kts. (V1,Vr,V2)......

In the end we had a little handheld computer which would perform take off calcs, but to be honest it was only a minute more effort to carry out a manual calc.

[Nick Thomas]

Going back to expansion and paint. With the aircraft expanding approx 6 inches and a temp change up to 127`c, I guess a special kind of paint; able to withstand such adverse conditions; must have been used? When deciding on the paint specification was any consideration given to the overall weight of the paint?
Did the repeated expansion and contraction cycle have a detremental effect on the ulitamate life of the airframe?
I read somewhere that on the last supersonic flight of each BA Concorde, the flight engineer placed his cap into the gap between his panel and the cockpit bulkhead thus leaving it there for ever more. A nice story if true.
Once again thanks
Nick

[galaxy flyer]

EXWOK

Excuse me, Vzrc was exactly what I meant. I remember reading it in the Concorde CDG report and wondered if it figured into daily per calcs or was it a more technical

If you could depart with 3 reheats, I guess it wasn't a problem with the transition to supersonic flight? What I find amazing is the F-22 goes on about super cruise but here was a plane designed over 40 years that routinely super cruised.

GF

[ChristiaanJ]

As far as AFCS goes, can you check your records?LOL. That should teach me to check my sources before putting finger to keyboard !
Most of my personal memories date from my Fairford years (1969 - 1974), so there may be the odd gap.....

CJ

[ChristiaanJ]

Surges were not an uncommon or common event on Concorde, but when they happened - as they usually affected both engines on that side - the aircraft would lurch /yaw and everybody on board would know about it...It was determined in a very early stage, that an engine surge or engine failure at supersonic speed would produce a very abrupt, inacceptable, and possibly dangerous, amount of yaw.

So the prototypes were equipped with "autorudder" computers. They used pressure sensors in the engines to detect engine failures, and they would then kick in a "pre-dosed" amount of rudder, that would then be "washed-out" gradually while the pilot dealt with the issue and added rudder trim.

They were manufactured by SFENA, and since I was their flight test support at Fairford, they became automatically my "babies".

The computers (analog, big boxes, the same size as the autopilots or air intake computers) were extremely reliable (we had only two passive faults during the entire flying career of 002).
Unfortunately the same could not be said of the pressure sensors, and since it was always easier to "pull" a computer than a pressure sensor, we found a computer on the bench every few weeks, which then had to be taken through a full test spec and sent back with "no fault found", before anybody was willing to look at the sensors.

Luckily a better solution was found, using a lateral accelerometer, and from the preprod aircraft onwards, each big separate autorudder computer was replaced by a single board tucked away in the autostab computer.

Since the function was always "on", there was no separate autorudder engage switch. Many years later, I discovered that several airline Concorde pilots did not even know the function existed....

CJ

[M2dude]

Nick Thomas
Going back to expansion and paint. With the aircraft expanding approx 6 inches and a temp change up to 127`c, I guess a special kind of paint; able to withstand such adverse conditions; must have been used? When deciding on the paint specification was any consideration given to the overall weight of the paint?[/QUOTE
Can't remember much about paint spec's, but a lot of experimentation/trial and error was carried out with different paints until the right one was found. I remember when G-BOAD was delivered, that copiuous sheets of paint had peeled off in flight. Finally a superb polyurithane paint was found that did the trick perfectly.
Did the repeated expansion and contraction cycle have a detremental effect on the ulitamate life of the airframe?
Yes Nick, the life of the airframe was limited by the number of supersonic cycles, however modifications carried out extended the life of the airframe significantly. (and more were planned).
And the 'hat in the gap' stories are quite true.

ChristiaanJ
[quote]Many years later, I discovered that several airline Concorde pilots did not even know the function existed....
This was the real beauty of the autostab' on all 3 axis; you could just safely take it all for granted. The Mach 2 engine out case was a classic, as not only would the aircraft yaw towards the dead engine but there was an adverse roll input, where the wing on the same side would LIFT due to the excess intake air for the failed automatically being 'dumped' through the now open spill door. If for any reason the aircraft HAD been under manual rather than autopilot control, then life without autostab would be rather uncomfortable to say the least. And putting further Concorde's achievements in terms of stability; the world's only previous large delta winged Mach 2 aircraft, the B58 Hustler, had the slightly awkward feature in the case of an outer engine failure at Mach 2, in that the yaw forces were sufficient to tear the fin off. This happened on more than one occasion during service life of the Hustler, but engine failure (or far more likely a deliberate precautionary shut-down) although hardly a non-event in the case of Concorde, it was routinely dealt with without drama or danger.

Dude :O

[stilton]

During the early years of Concorde testing and Airline service I had read it was used as a 'target' for practice interceptions by the RAF.



Is there any truth to this and does anyone know the profiles that were flown ?

[Nick Thomas]

I understand that before the first flights the test pilots had many sessions in the Concorde simulator. I have always wondered how before the first flight they decided to programme the flight enverlope into the simulator; especially as Concorde was so different to other jet transports?
I guess that as more information was gained during flight testing; that this was programmed into the simulator and therefore made it a more suitable machine for airline crew training.
Thanks
Nick

[ChristiaanJ]

I understand that before the first flights the test pilots had many sessions in the Concorde simulator. I have always wondered how before the first flight they decided to programme the flight enverlope into the simulator; especially as Concorde was so different to other jet transports?From the thousands of hours of windtunnel tests, test flying with aircraft like the Mirage IV, HP 115, BAC221, etc. etc. they already had a pretty close idea of how the aircraft was going to fly.
IIRC, André Turcat remarked after the first flight of 001 it flew pretty well like the simulator, or if anything somewhat better!

I guess that as more information was gained during flight testing; that this was programmed into the simulator and therefore made it a more suitable machine for airline crew training.There were two development simulators, one at Toulouse and one at Filton, that were used by the test pilots and by the engineers. These were "tweaked" whenever more data became availble before the first flights, and then updated with flight test data.
For airline crew training, two new simulators were built in the early seventies, again one in Toulouse (later moved to CDG) and one in Filton.
In the best Concorde style, they were designed and built by two different firms....

I don't believe anything of the development simulators has survived.
As you will know, the "cab" of the British Airways Filton simulator was salvaged and taken to Brooklands, where it's now slowly being brought back to life.
The Air France simulator at CDG, minus motion system and video display, was taken back to Toulouse, where it's slowly being restored, to go on display in the planned Museum at Toulouse.

CJ

[M2dude]

stilton
During the early years of Concorde testing and Airline service I had read it was used as a 'target' for practice interceptions by the RAF.
Really a question for my pilot friends, BUT.. I do recall that several years ago an RAF Tornado F3 requested permission to try a practice intercept on a JFK bound aircraft coming up to the accel' point... ATC relayed the request to the crew who had no objections, provided tha the rules of the air were obeyed, the ATC conversation went something like this.... 'OK, the Tornado is 15 miles astern of you.'. (at this point the burners are lit for the transonic acceleration).. ' he's 14 miles astern of you... 15..16....17...20... you can gues the rest, the F3 gave up in embarassment.

Dude :O

[chksix]

YouTube - Concorde breaking the sound barrier (http://www.youtube.com/w/Concorde-breaking-the-sound-barrier?v=5JOkSVlmuhY)

I feel the need to post this clip. :ok:

[notfred]

It was a Lightning that intercepted Concorde from behind:

English Electric Lightning Site - Story of the Month (http://www.lightning.org.uk/archive/0410.php)

I was in the Air Training Corps in Bristol in the late 80s and flew in the Chipmunks based at Filton. Used to see the spare Concorde sitting there outside the hangar. My father worked at BAe so we would go to the open day and see Concorde do her stuff there.

And a question of my own - I've heard that the engines were pretty powerful even at ground idle, so powerful that if all 4 were running then a tug would not be able to push her back. Any truth to this? Were just 2 started, pushback and then start the remainder? Also heard that the pilots had to watch the brake temps whilst taxiing out to takeoff - was this also due to the power?

[Brit312]

Yes we always started just the two inboard engines prior to push back and the outers when the push back was complete. This was for a number of reasons, but I do seem to remember it was not unheard of to break the tow bar shear pin on the initial push, so the less power the better

Remember that Concorde had no APU and no across the ship ducting for stating engines, therefore prior to push an air start unit was plugged into each pair of engines and the inboard engines would be started. This allowed, after push back, air from each inboard engine to be used to start it's outboard engine.

The other good reason for starting the inboards prior to push was that with no APU the cabin temp would rise quite quickly [specially in places like Bahrain in summer] and never mind the passengers
comfort, but some of M2dude and ChristiaanJ fancy electronic equipment was very temp sensitive , especially those intake control units down the rear galley. With Two engines running we could use their bleed air to at least try and hold the cabin air temp during the push back

When we first started LHR-IAD flights[ prior to thin lip///54% and other mods which improved our range] some thought was given to towing the aircraft to the taxi way near the end of the runway before starting engines so as to save fuel. I do not remember this actually ever being done though.

\

[ChristiaanJ]

YouTube - Concorde breaking the sound barrier (http://www.youtube.com/w/Concorde-breaking-the-sound-barrier?v=5JOkSVlmuhY)
I feel the need to post this clip. :ok:It IS a nice one....
There's a longer one with more of the story, but this is the essence.

TESGO is the designation of one of the waypoints on the Concorde route from CDG to JFK, shortly beyond the point where Concorde goe ssupersonic on its way over the Atlantic.
At the occasion of one of the last Air France CDG-JFK flights, a small group of French enthusiasts hired a boat to get a record of the overflight and the sonic bang, and they succeeded beyond expectations.

There can't be many Concorde friends, who haven't already seen this clip....

CJ

[ChristiaanJ]

notfred,
Not exactly the same subject, but still brake-related.

Some of the earlier-mentioned items like "3-2-1-NOW", the little 3/4 tab for the afterburners, the "T/O monitor lights" and such, were all due to the fact that it was not possible to run up Concorde to full take-off thrust, light the reheats, check everything, and only then release the brakes.... she would start to slide forward well before full thrust was reached.

Only 185 tons TOW, only ten little wheels... in brief, not enough "grip" to keep almost 70 tons thrust stationary !

CJ

[notfred]

Thanks Brit312 and ChristiaanJ.

Living in Bristol we used to see her go over on the way in to LHR and on a quiet day with the wind in the right direction we could sometimes here a very faint version of the "BaBoom" that was in the linked video.

Such a shame that they didn't keep at least one in a relatively easier to restore to flight condition and send it on the air show circuits with the Vulcan. With the talk of analogue FBW and PFCUs it reminded me of some of the Vulcan controls that I have read about, was there much technology transfer from the Vulcan to Concorde in the design stage?

[Brit312]

ChristiaanJ

The way I remember it was

"3-2-1 now" was to ensure that all 3 crew members started their stop watch at the same time i e on the call of NOW as that was the point the throttles were moved rapidy to the forward stops. In fact the noise abatement timing assumed the engines were allowed to accelerate at their own rate, rather than at a rate controlled by the crew

"Green lights" served two purposes
1] To allow the pilots to have a quick reference as to the state of the engines during the Take off

2] Prior to the nose gear mod ona rough runway [when it could be difficult to red the engine instruements] it did give the F/E an indication that the engines had reached the basic power required

3/4 tab. as different T/Os required diferent minimum reheats either 3 or 4
The small 3/4 tab was there just to visually remind crew as a back up to the briefing whether they were on a 3 or 4 reheat day

I have not I believe been on an aircraft where you run up to full power before releasing the brakes, but there again the memory could be fading, and I am sure the sudden release of brakes at full power would not do them any
good

Mind you I could be wrong

[M2dude]

Notfred
Love the lightning story, hadn't heard that one before.
I was in the Air Training Corps in Bristol in the late 80s and flew in the Chipmunks based at Filton. Used to see the spare Concorde sitting there outside the hangar.
That would have been production series test aircraft G-BBDG, A/C 202 before a purpose built hangar (more shed really) was built to house her, with fin and U/C removed. This aircraft has now been beautifully restored at Brooklands museum.
And a question of my own - I've heard that the engines were pretty powerful even at ground idle, so powerful that if all 4 were running then a tug would not be able to push her back. Any truth to this? Were just 2 started, pushback and then start the remainder? Also heard that the pilots had to watch the brake temps whilst taxiing out to takeoff - was this also due to the power?
You are quite correct about the pushback, not having an APU (THAT story again :p) meant that a one engine in each nacelle pair had to be started on the gate, and the other in each nacelle started after push. Having a symetrical pair started enabled all 3 hydraulic systems, and hence most of the critical systems to be checked puring pushback.
Brake temperatures always had to be monitored; they really could get very hot. If a wheel was still too warm after T/O, then the gear would be left down just a little longer to aid cooling. (Each brake also had an electric cooling fan).
Idle thrust was always a problem in that it was too high; there was a 'lo idle' setting, but depending on the temperature of the day the difference was not that big. You could not just reduce idle some more because of a malady known as rotating stall. This can plague any engine, but the Olympus 593 was particularly susceptible. At very low idle speeds, pockets of air 'rotate' around the first few compressor stages and can completely alter the airflows through the engine. It is important that the engine is always accelerated quickly through this zone on start-up, because serious damage can occur if the engine runs for any period of time in the rotating stall region. If the engine DOES operate in this zone, then the combustion process can even occur in the last few stages of the HP compressor, causing extreme damage. This damage, although malignant, can result in blade failure and the subsequent damage to the combustion chamber and turbine areas. This can occur within a few flights of the event, so just cranking down the idle was never an option.

[M2dude]

Brit312
Your memory is not fading; the ONLY disadvantage with carbon brakes is their susceptabilty to over-torque damage. For this reason 'max power on brakes wasalways verboten. I seem to remember that the development A/C with steel brakes could be 'wound up' on the brakes. But the improved braking performance, not to mention a 1,200lb weight saving of carbon made this a small price to pay.
The 3/4 tab; that takes me back, it was officially called the 'Reheat Capability Indicator', definately not the most sophisticated part of the Concorde flight deck. (I seem to remember that before the 'RCI :}' was fitted, an INS CDU Waypoint thumbwheel was used as a 3 or 4 reminder).

Oh and ChristiaanJ; I always loved that clip.

Dude :O

[ChristiaanJ]

Brit312,
Of course you're right on all those items.
I only mentioned them as they were linked in some way to the fact of not being able to run up to full thrust "on the brakes".

CJ

[milsabords]

In the late 60 a major computer manufacturer prototyped a miniaturized version of one of its products dedicated to real time process control. The original beast was bigger than an american fridge, while the prototype and its memory were as small as two shoe boxes.

It was proposed to the Concorde project, but never seriously considered.

[twochai]

I rode Concorde two or three times and what a ride it was!

On one occasion I had booked to travel BA 'J' class from Washington to Delhi on a regular business trip. Out of DCA to JFK they booked me on the 'Concorde shuttle' (a Dash 8 of US Airways, believe it or not) to connect with a 744 to LHR and another connection on to Delhi. At DCA check in the agent mumbled something about a catering problem out of JFK, but I took no particular notice. On arrival at Kennedy an agent with a name placard diverted me to the Concorde gate, a nice surprise indeed, even for a BA Gold Card holder.

On boarding Concorde, I gave my business card to the purser, asking that she pass it forward. A few minutes later as the door was closing she came back to pass along an invitation from the skipper to join them in the cockpit. During the short delay for start clearance, the captain briefed me on the Canarsie 31L departure I was about to watch from the jump seat behind. "3-2-1 GO" as the aircraft lept forward, V1/Vr/V2, 100', roll left 30 degrees to track towards Canarsie, 1' 30" (or something similar, some details are long forgotten now) power back for 500'/minute ROC to 3,000', then accelerate to 250K as the heading continued around for the outbound course and the ocean crossing. A true aerial ballet.

For the balance of the climb I plied the guys with questions and received courteous and detailed answers to every one, along with a 'freebie' - some hilarious repartee between the BALPA captain and the management F/O type, with occasional interjections by the Engineer. I stayed through the supersonic acceleration until I thought I'd worn out my welcome at cruise climb, returning to my seat in the mid cabin area for lunch. They invited me back for the descent and approach, which was very well appreciated.

On descent over the U.K. and passing through 10K' abeam Southampton, as I remember it we got a yellow 'Radiation' caution light (normally to warn of higher than normal levels of radiation in the tropoause from sun spot activity, I believe), which caused me to ask WTHWT? The slightly bored F/O said, as he cancelled the light, "Oh, its 'just' a nuclear power plant down there, we get this all the time"! (And for all these years I had swallowed the PR line from the nuclear industry that they were squeaky clean, unlike those of us in the aircraft manufacturing business??)

The approach and landing at LHR was fascinating to watch, without the frenetic activity of the departure. No flaps and no configuration change after gear down, virtually no flare, perhaps even a little nose down pitch as I observed (was that true??) the handling pilot just let it float into ground effect for a gentle touch down, snappily into reverse and heavy, but not maximum braking. It looked easy, of course.

The F/E was a key part of the entire operation and I find it hard to believe that a Concorde "B" would have eliminated his position, no matter how automated the systems might have become. The whole flight was very, very professionally handled with that air of apparent casualness that comes only from a very disciplined team operating at the peak of performance. A true joy to watch.

I guess I was just a minor part of the vaunted 'halo' effect that BA marketing always claimed for Concorde - its ability to pull additional traffic to its worldwide services in a very competitive business climate. But it sure worked for me! And all because of a catering misadventure, or was that just an excuse??

However, the thing that has always truly amazed me about Concorde is that this machine was created by two companies, two countries, with two languages, two systems of measure and two very different cultures in a period before the invention of Computer Aided Design and on-line communications! What a marvellous thing that mankind created. My hat off to you all.

Thank you, John, that was some flight!

TC

[atakacs]

@twochai

No idea who you are but THAT is what I would call first class treatment ! Except allowing you to barrel roll it I don't what more they could do ;)

All other: as may other lurkers I immensely enjoy this thread - keep it up :ok:

[Nick Thomas]

I know that other planes such as the 747 had INS; so in a way this question is not specifically related to Concorde. With the radio navigation update was the lat and long of appropiate radio beacons hard wired into the system and then based on the assumed position the nearest beacons would automatically be tuned or did the pilots enter the lat and long of the beacons that they would then manually tune?
I guess there were three INS units to allow for drift etc and it would be easier to spot if one unit was less accurate than the other two. So when radio updating was not possible ie over the atlantic was it possible for the automatics to weigh against one rouge reading
Finally as Concordes ground speed was over double that of other aeroplanes was there any need to take this into account when designing and building the INS system(other than the speed display that would have to show an extra digit)?
Thanks
Nick

[rudderrudderrat]

Hi Nick,

On 707s in early 70s I can only remember 2 INS sets on the centre console. (Where was the third?) They were independent of each other, but we could load up to 9 new way points into both sets simultaneously using the "REMOTE" buttons. There was no automatic radio position updating.

The best we could do was press the "HOLD" button when we were over a VOR, compare the displayed position with the published, and update the position if it was in significantly in error. (In practice we hardly ever did it because determining the overhead position was always a bit iffy). All radio Nav aids had to be manually tuned. Navigation was done using Heading select, whilst comparing Cross Track Error and Desired Track, Dist to Go etc.

Later, with the introduction of FMS (on L1011) we had 3 INS, Tripple MIX, Radio position updating using DME/DME, ETA prediction etc. PFM.

Since INS was developed initially for Intercontinental Ballistic Missile Guidance and the Apollo Space programme, I don't think Mach 2 or less was a problem.

I've enjoyed reading this Concorde thread more than anything else that's been posted. Please tell how the Nav displays evolved during their service.

Regards, RRR

[M2dude]

twochai
It is wonderful that you have such fond flying memories of Concorde;in the pre-911 days there was a fairly liberal open door policy for flight deck visits (Although all passengers were made to feel really special, it is so great that the guys had you up front for so long on that flight. You just never lose those sort of memories, I know).
On descent over the U.K. and passing through 10K' abeam Southampton, as I remember it we got a yellow 'Radiation' caution
The Radiation Meter was an interesting addition to Concorde's collection of avionics kit. It was primarily designed to detect solar proton, as well as neutron radiation, (the detector element lived behind the fwd r/h wardrobe as I remember and was a total pain in the 'you know where' to get at). The indicator displayed the dose rate in millirems/hour, with amber and red triggers, triggering a master alarm. (The amber was a mere caution, whereas the red was a warning. I can't quite remember any figures, but a descent was required with a genuine red warning. I think I'm correct in saying that no such descent was ever required, at least in the UK). There was a huge amount of concern initially about crews long term exposure to radiation, after all there is a fairly linear relationship between solar radiation and altitude. In reality however Concorde crews received far less radiation than subsonic crews; although the dose rates may have been higher, the sector times were a fraction of a lot of the subsonic routes. (Even a subsonic LHR-JFK is WELL over twice the sector length). Nuisance ambers were not uncommon, a certain 'facility' in Berkshire would often register as the aircraft over-flew, as well as MANY years ago, Three Mile Island itself. I remember that there were long term plans to replace the radiation meter with a portable 'carry on' device that was being trialled. (Spares for the detector were becoming very difficult to obtain).

Dude :O

[M2dude]

Nick Thomas
You really do have a great selection of queries Nick :).
With the radio navigation update was the lat and long of appropiate radio beacons hard wired into the system and then based on the assumed position the nearest beacons would automatically be tuned or did the pilots enter the lat and long of the beacons that they would then manually tune?

Although Concorde was wired for full area navigation, with autotuning nav radio selectors, this was never fully implemented, and the autotuning selectors replaced with fairly conventional units at entry into service. (Although on route proving trials, G-BOAC did fly with the autotuning selectors).
HOWEVER, a really neat 'next best thing' system evolved: Originally the INS's had an optical card reader for inputting waypoints etc. (when 'island dodging' flying supersonic over the Mediterranean, to avoid booming the populous, it was said to be almost impossible to add waypoints quick enough manually). This card reader was really quite poor; when you inserted the card it was a lottery whether it came out of the reader in one piece, or even at all. Eventually a fairly sophisticated system was developed, and the card readers done away with altogether, and a navigation database was added to the INS units. This database would be updated a couple of times a year, and had to be loaded into each of the three units separately, USING A CASSETTE TAPE!!! All the 'normal' collection Concorde of routes were stored in the database, although the INS core memory could still only handle 9 waypoints at a time. (A light flashed when it was time to 'turn the page' and with a simple push of a button the next bank of waypoints were automatically uploaded into INS core memory. DME co-ordinates were also stored, along with the co-sited VOR frequency that had to be manually dialled for that station; ideally the left and right INSs would use two differing DMEs for best accuracy, and INS3 would use the mean. (Another simple button push would nominate and select the DME to be used by the INS). So, when flying within range of a VOR, the INS position would be refined with the co-sited DME slant range, but when flying oceanic, the 3 INSs would 'triple mix' their inertial positions to give a mean position. A 'rogue' INSs position would be rejected by the other two however, so as not to be sent to the moon because of a bad unit.
Rudderrudderrat
Nowhere near as sophisticated as the FMS system on the Tristar as you can see, but it seemed to work absolutely beautifully. (And when the system was DME updating, we even got an indication from an RNAV light, originally fitted for Area Navigation.
Since INS was developed initially for Intercontinental Ballistic Missile Guidance and the Apollo Space programme, I don't think Mach 2 or less was a problem.
Actally there was a problem of sorts, above 900 KTS G/S, the original DELCO INS would generate an error (after all, WHO would ever want to travell at more than 900 KTS; something must be wrong here :=?). A special 'supersonic mode' had to be enabled by the way of pin programming in the INS rack, which inhibited this warning.
Really glad you are enjoying the ravings of us supersonic nutters. :)

Dude :O

[Nick Thomas]

Thanks for your comment M2dude, am just SLF with an interest in design, due to being a member of the profession accused by the Prince of Wales "of doing more damage to this country than the Luftwaffe"!
This may seem a trival question but on the ITVV video Capt Rowlands is checking the pitch trim and the sound made is as he says "rather like a french bicycle bell" and he suggests that it may indeed be made by such a bell. I rather like that idea; but was it so?
I remember in the early eighties loading programmes into my ZX81 using cassettes; and not having much success! Mind you a cassette tape would be far better than an 8 track as an 8 track would keep reloading the route and you would end up flying in circles!
There is a serious point here and that is if you are designing such a complex machine as Concorde, if you can use proven technology in some areas then do so. It appears that all the people involved did so and didn't waste time on "reinventing the wheel" or complicating things just for the sake of it. Good design is about finding the most appropiate solution and Concorde is a fine example of that.
Once again thanks
Nick

[M2dude]

Nick Thomas
SLF keep the rest of us in business, your input is so very welcome here. Nick, the 'French Bike Bell' is exactly what it was, as the electric pitch trim wheen ran up or down a striker would impact this tiny bell and make the sound that you describe. 'Pitch Trim' sounds like a strange term, after all the aircraft had no trim tabs or tailplane as we all know. What varying the pitch trim used to do was to alter the neutral setting of the artificial feel unit, the control column following this neautral datum.
ZX81, takes me back here. The tape loading that was used on the INS took around 45 minutes per navigation unit, that's two and a quarter hours total for the system. (There was no cross-loading). If Concorde had remained in service, new legislation meant that a more accurate primary navigation system would have been required. One of the systems under consideration was a Litton 82 laser INS with GPS refinement. (As well as DME updating also).

Dude :O

[Lurking_SLF]

Having only dropped in on this thread and wasted about two hours of supposedly work time reading it....
I have to recommend this piece of _homage_ to Concorde and the plane that unfortunately(!) beat it.
Like him or lump him - Dickinson's "everything goes to 11" does describe her beautifully...

Part 1: YouTube - Flying Heavy Metal Episode Three: Size Matters-Part 1 HQ (http://www.youtube.com/watch?v=ztM-co447Po)
Part 2: YouTube - Flying Heavy Metal Episode Three: Size Matters-Part 2 HQ (http://www.youtube.com/watch?v=f-nEKYthtm8)
(The clip starting at 1:38 always makes me smile...)
Part 3: YouTube - Flying Heavy Metal Episode Three: Size Matters-Part 3 HQ (http://www.youtube.com/watch?v=r-5QtrQwk-Q)
(4:01 - fuel flow...)
(4:40 - An apology to concorde

My name say who I am, so back to lurking....
Darragh

[twochai]

No idea who you are but THAT is what I would call first class treatment

Other than being a regular customer of BA at the time, I was nobody. It certainly was First Class treatment, but as M2Dude said:

all passengers were made to feel really special, it is so great that the guys had you up front for so long on that flight.

On the other hand, among the really important people that I recognized on that same flight included:

Boutros Boutros Ghali sitting in row 1 with his security detail
Paul Newman sitting directly behind me, reading my sports car magazines and asking why I was the one who got to ride up front
John McEnroe down the back, but uncharacteristically quiet!

[atakacs]

Just wondering: does anyone know if a Concorde driver ever flew the Koncordski (Tu-144) ?

[M2dude]

Lurking SLF
An interesting post Darragh, but with the greatest respect I think that you may have missed the whole point of this thread. As wonderful as the Boeing 747 is (personally I think that the 744 is one of the finest commercial aircraft ever built), I think anyone would agree that there is no comparison at all, as far as technical achievement goes, between the 747 and Concorde. So many boundaries had to be crossed with the Concorde design, and technical problems were overcome that had defeated many of the world's leading designers. I do have a vague idea what I am talking about here; although I was directly involved with Concorde for 30 years, I am also licensed on both the 744 AND the 777, and although I hold Boeings with the greatest respecect and admiration, nothing so far in the realms of commercial aviation can really compare with the technological marvel that was Concorde.
I think that most of the posters here will be sorrry that you felt you wasted 2 hours reading through these pages, I feel most of us have thoroughly enjoyed reading each others posts.
The YouTube links were great though.
atakacs
To the best of my knowledge no. The original TU144 was an extremely crude attempt by the Soviets at commercial supersonic aviation, and the political climate at the time would not have permitted such a thing. The TU144D used in the 1990's as a joint NASA/Russian experiment was a different beast altogether however, with far better engines and systems, but as far as I am aware the only western pilots to fly it were American chaps.

Dude :O

[DozyWannabe]

The original TU144 was an extremely crude attempt by the Soviets at commercial supersonic aviation
Well, it was essentially a development airframe pressed into premature service for the sake of beating a western project into the air. One wonders whether the story would have been different if the designers had been allowed to take their time and develop it properly.

[galaxy flyer]

Having seen some of their other efforts, this one doesn't wonder. Ever fly on an IL96 or see a IL62? Their fighters aren't crude, they are positively agricultural! Out tractors are more elegant in their engineering.

GF

[atakacs]

The TU144D used in the 1990's as a joint NASA/Russian experiment was a different beast altogether however, with far better engines and systems, but as far as I am aware the only western pilots to fly it were American chaps
I wasn't aware of the significant upgrades - devised into the tune of $300mn - that where applied to this airframe. Your remarks made me read some very interesting articles on this project.

[Nick Thomas]

M2dude I have another question concerning "debow" You very clearly answered my original question on another thread. I just wondered how the engine was kept at a sub idle 30% N2? Was it done by careful metering of the fuel? and if not how was it done? I ask because the throttles would be closed during start up.
The whole engine installation with the ramps, spill doors, reheats and noozles must have been a nightmare to "fine tune" through all the different phases of flight.
Thanks for the explanation of how the pitch was "trimmed" Due to Concorde having elevrons instead of ailerons; was the aileron trim dealt with in a similar way? I guess the rudder trim could be applied normally.
Thanks again
Nick

[DozyWannabe]

Having seen some of their other efforts, this one doesn't wonder. Ever fly on an IL96 or see a IL62? Their fighters aren't crude, they are positively agricultural!
This is off-topic, so I ain't going to bang on this subject after this post, but I wouldn't be so quick to denigrate former Soviet technology in all cases. Those "agricultural" fighters can mix it up with the best the west has to offer (until - or if - the F22 comes online) in terms of manoeuvering ability, if not in terms of weapons. Elements of their rocket technology were in advance of what we had at the time, and the solutions they came up with to put the Tu-144 in the air may have been crude, but they were to some degree effective, which can denote an elegant solution in itself.

That said, this thread is about an aircraft which was the result of - unarguably - some of the best engineering in aviation history, and I'd much rather talk about that! :)

[Bellerophon]

Nick Thomas

...I just wondered how the engine was kept at a sub idle 30% N2?...

Just below each engine's individual start switch, there was a second switch, which would select the type of start required, either NORMAL or DEBOW.

When between ten minutes and five hours had elapsed since an engine was last run, a debow start was required. With a debow start selected, the engine was started normally, but the debow system automatically stabilised the engine at a sub-idle RPM, around 30% N2, whilst the interior engine temperatures became more uniform and the HP spool shaft re-aligned/straightened itself.

As to exactly how it did this, you're going to need a reply from an engineer not a pilot. As far as we were concerned, it was the PFM box in the engine start system!

After running for one minute stabilised in debow (or when the debow light came on) the F/E would return the debow switch to normal and check that the N2 returned to idle and the debow light went out. The F/E would monitor the N2 very carefully over these few seconds, as the engine came out of debow, to check that the engine cleared rotating stall.

If it didn't, two things would happen.

Firstly the F/E got fairly busy, trying to clear the engine out of rotating stall without causing it to surge, and secondly, as with any Concorde engine malfunction drill, I quietly give thanks that I was a pilot and not a F/E.

If a debow start was required, but somehow got missed, the engine could give a reasonable impression of an out-of-balance tumble drier, or so I'm told. ;)

Best Regards

Bellerophon

[galaxy flyer]

DW

No argument from me on former Soviet fighters being capable, but please read Red Eagles, if you want a Western view on their planes. Lots of poor engineering and execution, not that impressive.

GF

[Lurking_SLF]

M2Dude,

Sorry, I certainly don't consider it a wasted two hours - I should be more careful in my phrasing in future...

I never got to fly on Concorde, but I did get to sit in the left hand seat in Manchester for a few minutes on one of their tours - it's one of my prouder pictures on my desk.

Apologies for not getting the tone I wanted across - and no offence taken!

No more post from me in this forum - I'll leave it to the experts...

Lurking_SLF

[ChristiaanJ]

The TU144D used in the 1990's as a joint NASA/Russian experiment was a different beast altogether however, with far better engines and systems, but as far as I am aware the only western pilots to fly it were American chaps.
I wasn't aware of the significant upgrades - devised to the tune of $300mn - that were applied to this airframe.
To conclude this slightly o/t story :

The Tu144D was the last production model of the Tu144.
With improved engines and other refinements, it was capable of supercruise (Mach 2 without afterburners). Only five were built, and they came too late ; the aircraft went out of service, and were put into storage.

Tu-144D s/n 77114 was brought out of mothballs (with less than 83 hours "on the clock") for the joint NASA/Russian program in the '90s and modified, with completely new more powerful engines (same as those of the 'Blackjack' Tu-160 bomber) and a fit of sensors and test equipment, to become the Tu-144LL (flying laboratory). A total of 27 flights were made.

The entire "High Speed Civil Transport" study indeed cost over $300M, but the actual work on the Tu-144LL reputedly cost less than $20M, although it's not known exactly what that bill represents.

CJ

[M2dude]

DozyWannabe
Well, it was essentially a development airframe pressed into premature service for the sake of beating a western project into the air. One wonders whether the story would have been different if the designers had been allowed to take their time and develop it properly.
Good point I suppose, but you could say that the six Concorde prototypes, Pre-Production and Production Series Test aircraft were also development aircraft, and yet more or less worked just as it said on the tin', where the TU144, in spite of all the facilities of Andrei Tupolev's design bureaux, not to mention more or less unlimited Soviet state funds produced a machine that in my opinion really BELONGED in a tin can. (I know this is all off topic, honest guys, I won't mention this stuff again :O).
In reality the Soviets really lacked both propulsion technology as well as the systems expertise required to build an aircraft with even a remote hope of Mach 2 cruise, let alone safe and comfortable enough for fare paying passengers. The original aircraft had all for engines in one giant nacelle, and the landing gear retracted into the engine inlet duct itself, great for an undistorted flow path to the engines :}. The variable inlets were manually operated by the flight engineer as well, no automatics here. In the mid 1970's the Russians even approached PLESSEY to build a digital engine control unit for the TU144. A similar PLESSEY unit had been VERY successfully flight trialled on production series aircraft 202 (G-BBDG) and only lack of funds prevented it being used on the production aircraft. As this unit could obviously be used for Soviet military applications, there was objection from the UK government, and more than just a little trans-Atlantic pressure applied, and so this venture never happened.
Those "agricultural" fighters can mix it up with the best the west has to offer (until - or if - the F22 comes online) in terms of manoeuvering ability, if not in terms of weapons.
Until the advent of the Mig-29 and Sukhoi SU-27 this really was not the case. I'm afraid I'm with galaxy flyer on this; If you look at the air war over Vietnam, when an F4 met a MIG 19 or MIG 21 in an even air-to-air combat, the MIG was going down. (OK this could be partially down to superior US pilot traing etc, but if you look at the handful of skirmishes where the 1960's/1970's Soviet aircraft were engaged in Combat against US or French built fighters, the MIGs never really did very well at all). However, the aircraft that the Russians have been producing from the Mig 29 onwards seem to be in a completely different class now; hope they really are the good guys now.
ANYWAY, back on topic :mad:
Lurking SLF
No problem at all Darragh, please keep visiting us and post here also anytime. :)
Nick Thomas
M2dude I have another question concerning "debow" You very clearly answered my original question on another thread. I just wondered how the engine was kept at a sub idle 30% N2? Was it done by careful metering of the fuel? and if not how was it done? I ask because the throttles would be closed during start up.
I'm not sure that I can describe the DEBOW process remotely as eloquently as my friend Bellerophon did, I particularly loved the 'out of balance tumble-drier' bit, but starting a hot or even warm engine, even at DEBOW, you could certainly 'feel' the noise on the flight deck, until the shaft distortions evened out. :}
Now for the PFM bit, equally eloquently alluded to by Bellerophon:
DEBOW itself was maintained by a special sub-idle datum in the electronic Engine Control Unit, and once the engine was accelerated towards normal idle (61-65% N2, depending on the temperature of the day) even if the switch described by Bellerophon was accidently re-selected, an electronic inhibit gate in the ECU prevented this sub-idle datum from being used again that engine cycle.
Thanks for the explanation of how the pitch was "trimmed" Due to Concorde having elevrons instead of ailerons; was the aileron trim dealt with in a similar way? I guess the rudder trim could be applied normally.

You're welcome Nick, actually the roll and yaw trims operated in a similar manner to the pitch, although of course these was applied by a manual trim wheel only. (No French bike bell either :p). Rotation of either wheel (more a giant knob actually) merely shifted the neutral datum of the relevant artificial feel unit, which in turn shifted the rudder pedals or control yoke; the resolvers for the FBW system would in consequence demand this 'trimmed' control surface movement.

Dude :O

[galaxy flyer]

The BR710 on the GLEX and G 550 also need to "rotor bow" on start within the same time limits. I fly the GLEX and the FADEC does it automatically, but I understand the G550 installation requires the pilots to recognize the requirement and motor for 30 seconds. Sub-idle vibration is quite discernible during an unbow start. Interesting that RR engines require this as I have flown GE and P&W, never heard of it.

GF

[ChristiaanJ]

Well, it was essentially a development airframe pressed into premature service for the sake of beating a western project into the air.
Good point I suppose, but you could say that the six Concorde prototypes, Pre-Production and Production Series Test aircraft were also development aircraft
Something I think I hinted at before, was how much the two Concorde prototypes differed from the aircraft that followed, even from the pre-production aircraft.

Wherever you look... the cockpit, the visor, the engines, the tail, the avionics, other systems... the prototypes were a first "iteration", designed and built to prove the concept.

The real development was done on what were the real "development aircraft", the pre-production and first two production aircraft (even if 01 / G-AXDN was a bit of a hybrid, retaining the short tail and the early engine nozzles).

I hope sometime the story; of how different were 001 and 002 from those that followed, will go on record before it fades into the mists of time.

CJ

[wiggy]

If you look at the air war over Vietnam, when an F4 met a MIG 19 or MIG 21 in an even air-to-air combat, the MIG was going down. (OK this could be partially down to superior US pilot traing etc

Umm, at the risk of thread drift and also offending those who were there dare I say that's a little broadbrush. The USAF had serious issues early on in the Vietnam conflict with the exchange rate (of losses), due in part to the dreaded Rules of Engagement but also due to the F4's poor turning performance vs. the Mig 19/21, exacerbated by the average USAF pilot's lack of training in Dissimilar Air Combat.

Certainly in F-4 v a Mig 19/21 (especially the later varient 21's) with a determined pilot I wouldn't be as bold as to assume "the "MIG" was going down" - ask anyone who's done any training with the Aggressor Squadrons :E

[ChristiaanJ]

Umm, at the risk of thread drift ....Yes indeed.
That sort of discussion belongs in the Military Aircrew forum.

One could say that the Tu-144, and also the Boeing 2707 and Lockheed L2000 were part of the background against which Concorde was born.

But "F-4 v a Mig 19/21" is not really part of that context...... so please?

CJ

[galaxy flyer]

CJ

Back to thread, which came first, the American designs or the Concorde? Somehow I thought the American entries were a reaction to the Concorde. In any case, both US planes would have been huge. There has been talk of a supersonic biz jet for decades, but no real progress and I doubt there will be until it can fly over land supersonic.

GF

[ChristiaanJ]

CJ
Back to thread, which came first, the American designs or the Concorde? Somehow I thought the American entries were a reaction to the Concorde.I think you're right, but I'd have to look up some dates first.

Interestingly, all the supersonic transport designs of the era (Concorde,Tu-144, B2707, L2000) can trace their ancestry back to NASA (NACA?) public-domain studies of the late fifties, that demonstrated the advantages of a slender delta for a supersonic transport aircraft.

CJ

[Nick Thomas]

Hi everyone
Please correct me if am wrong but was there not a slender delta wing prototype built by Fairley in the middle fifties. As I understand it, the plane was built to study a delta wing performance at low speeds. Therefore it had a fixed undercarriage.
Regards
Nick

[wiggy]

But "F-4 v a Mig 19/21" is not really part of that context...... so please?

Forgive me for butting in again, you're in part quoting me but I wasn't the one that brought the F-4 into the debate in the first place. If the Concorde fanclub brings the F-4 vs MIG 19 into the debate and then glibly uses it as an example of the superiority of Western technology then I feel there's a right of reply from those of us who have actually flown the aircraft ( 1000 hours F-4 in my case) and used the technology, irrespective of wether or not it's a military or civil forum....or do you just want to argue in the abstract?

As a general point many in the West have almost always believed in the superiority of Western designers and engineers and whilst Concorde may be one shining example of what the West did right we should not forget that on the evidence of Sputnik, Vostok, Luna 9, Lunakhod and even the MIG21 Russian ( or German :E) engineers can achieve worldbeating results with minimal resources.

But, to summarise, yes, it would seem the TU-144 was a dog :sad:, does that get us back on thread?

[M2dude]

Nick Thomas
Please correct me if am wrong but was there not a slender delta wing prototype built by Fairley in the middle fifties. As I understand it, the plane was built to study a delta wing performance at low speeds. Therefore it had a fixed undercarriage.
I think you are refering to the Handley Page HP115 Nick. The Fairey design was the FD2, the first conventional aicraft in the world to exceed 1,000 MPH in level flight. A re-winged version, designted the BAC 221, was used also to evaluate the handling characteristics of an ogival delta wing for the Concorde pragramme.

Dude :O

[Nick Thomas]

Thanks M2dude. You are right and my memory is getting worse due to old age!
Regards
Nick

[ChristiaanJ]

A nice touch is that both the HP115 and the BAC221 have escaped the scrapman, and are now standing next to Concorde 002 in the Fleet Air Arm museum at Yeovilton (GB).

CJ

[Lance Landing]

Long time lurker, first time poster here.

This is the best, most educational and informative thread I've read on any website in ages.
Keep up the good work! There are many of us out here who are very grateful for all the time and trouble taken by you people at the "Sharp end" to share your recollections.

Thank you. :ok:

[stilton]

Yes, in my humble opinion I vote this as my favourite thread of the year, it has been absolutely fascinating, educational and most enjoyable.


The technical insights revealed by the real operators have only added to the appeal of this Aircraft for me.


Bellerophon I found the photograph taken in the Cruise at FL600 and Mach 2 to be quite
stunning, what an amazing set of numbers to have in front of you as an Airline Pilot !




Thanks M2dude, ChristiaanJ, Bellerophon for your insiders view and all other contributors.

[ChristiaanJ]

I think I speak for all the "contributors", when I say we all have a certain amount of pride in having been part of the "Concorde Story" and that we all take real pleasure in sharing that story with all those who are interested !

So all you "lurkers" ... don't hesitate to go on asking your questions. We'll do our best to answer them !

CJ

[TURIN]

As a BA apprentice in the early eighties I spent 12 months in the old 'wing hangar' (TBB) cutting my teeth, as it were, on the future of aviation. (The newly introduced B757 was also housed there so I was partly right). I was still growing-9 stone wet through and I had to run around in the rain to get wet-so if there was work to be done in the "Bent Nail's" fuel tanks then I was volunteered. Pouring tins and tins of Thiokols best sealant along leaking joints was a favoured pastime, so it begs the question were the leaks ever plugged?

I have a load of photos of G-BOAG just before it was reintroduced (rebuilt?) into service after being a Christmas tree for years. I think it was taken out of service after the wrong hydraulic fluid was uplifted but I may be wrong there. Never seen so many robbery labels before or since. If I ever get my scanner I'll post 'em up one day.

Fascinating thread gents, keep it going. :ok:

[Cron]

My question concerns the Concorde nose gear. It rotates forward for stowage thus against the airflow and perhaps requiring more hyd power than a rear retract mechanism. What were the factors in this design decision - particularly considering that this beautiful machine seemed long enough to accommodate rear retraction?

Thanks

Cron.

[M2dude]

I can only echo ChristiaanJ, we all are quite humbled to be able to share our experiences with you guys. Please keep on posting everybody. (There's no such thing as a stupid question here, but as to some of my answers..... :O).
And Stlton.. our thanks all go out to YOU, for starting this thread in the first place. :D
TURIN
Glad to hear that you enjoyed your 'Rocket' time in TBB. As far as plugging the leaks, well things did improve quite a bit. but a fully laden aircraft could sometimes still be a little 'wet' on the ramp.
CRON
The nose leg had to retract forward, purely because the fuselage section of fuel tank 9 was immediately behind. (The nose wheel also had a single steel disk brake, based on an automotive design. (I'm 90% sure it was a Ford Cortina)

Dude :O

[bizdev]

I cannot think of a civil airliner where the nose gear retracts backwards - they all retract forwards. Except the Trident fleets where the NLG was offset from the centre line of the fuselage and retracted sideways. I remember my Avionic colleagues teling me that this was designed specifically because the Cat3b autoland was so accurate they didn't want the pax to have an uncomfortable ride as the nose wheels rolled over the runway lights on landing :O

[TURIN]

I cannot think of a civil airliner where the nose gear retracts backwards - they all retract forwards.

No me neither. It helps when gravity extension is required too as the airflow pushes the leg back to the locked down position.

M2Dude thanks, a lot of memories returning with this thread.:ok:

[twochai]

I cannot think of a civil airliner where the nose gear retracts backwards

Tupolev 114?

[canuck slf]

I had the pleasure of one trip as SLF on Concorde LHR - JFK (1978/9? grey cells depleting) which involved a return to LHR after dumping fuel due to hydraulic failure of two systems. No complaints from me, two take offs and landings for the price of one plus two hours of additional catering at LHR while the aircraft was fixed. Big run on asprins by the time we approached JFK!
However on the second departure the AC also suffered loss of hydraulic systems and I understood that it arrived at JFK on one system. After a storm delay at JFK I departed on AA listening to the ATC on the IFE with the Concorde following. Yet again the Concorde requested fuel dump and return due to hydraulic failures. The previous days I believe the Concorde had also experienced hydraulic failures and at one point BA cancelled some flights. AF were not experiencing the same problems and I read several years later that the problem was attributed to minute quantities of water being introduced into the system by a repenishing tanker being parked outside, wheras AF stored their tanker inside. The water then generated steam when the system ran with consequent seal failures.

Is the above cause correct, or was there more to the story?

Apart from all the normal Concorde observations, I also noticed that when trolling around over Bristol dumping fuel at a relatively high AoA the rear outboard surfaces, I was seated at the rear, vibrated at an alarming aplititude and frequency. Would this be caused by aerodynamic buffet or rapid auto pilot control inputs?

Thanks in anticipation.

[M2dude]

Hi canuck slf, Your incident was not the hydraulic contamination one, I'll describe that one in a minute or so below.
As far as your adventure goes, in the early days of Concorde operation there was an on-going issue of hydraulic seal failures. This led to the sort of thing that you described, where a major seal failure would occur, resulting in the loss of a main system. The standby Yellow system would be switched in to replace the failed one, and depending on the nature of the initial failure, could leak out of the same failed seal. (There were a couple of 'common areas', they were the intake spill door jack, and the Powered Flying Control Units; failures here could result in a double system fail). Your incident was almost certainly due to one of these cases. In the early 1990's the original Neoprene hydraulic seals were replaced with a new Viton GLT seal; this material had far superior age shrinking characteristics to Neoprene, and more or less cured the problem overnight. Eventually all the seals in each aircraft were replaced, and apart from a very few isolated cases, dual system losses were eliminated forever. Air France suffered a similar proportion of failures, however as their flying hours were a fraction of BA's, the effects were not as immediately apparent.
As far as far as the hydraulic contamination story goes, this happened in 1980 but involved one aircraft only, G-BOAG, but in it's original registration of G-BFKW. (having previously been on loan from British Aerospace, where it flew originally as a 'white tail' under this registration). The fragile nature of Concorde hydraulic fluid was not fully understood at this time, and as you say, a hydraulic drum dispenser had inadvertently been left exposed to the atmosphere, and had subsequently suffered water contamination, and this contaminated fluid had found it's way into G-BOAG. Now this hydraulic fluid, CHEVRON M2V has only two vices: One is that is extremely expensive, and the second is that it is highly susceptible to water contamination, EXTEMELY SO. If my memory serves me correctly, the maximum allowable level of water in the fluid is about 8ppm. (parts per million) and the fluid that was analysed after G-BOAG's problems was at about 30 ppm. The water deposits in the fluid gave the equivalent effect of 'rusting up' of critical hydraulic components. I was investigating an air intake control defect the previous day to the incident, but like everybody else had no idea that the real issue here was one of major systems contamination. We were all convinced that we had nailed the problem, only to find that the aircraft turned back on it's subsequent LHR-JFK sector with more serious problems, not only affecting the air intakes, but the artificial feel system also. It was now that we realised that there had to be a hydraulics problem here, and after fluid analysis, the awful truth was discovered. After this event, and the fragilities of M2V fluid were better understood, a strict regime of housekeeping was put in place in terms of fluid storage, and no such incidents with BA ever occurring again. The aircraft itself did not fly again for nine months, all components that were affected were removed from the aircraft and completely stripped and overhauled. Also all of the system hydraulic lines had to be completely purged, until there were no further traces of any contamination. After the aircraft was finally rectified, she successfully again returned to service with her new 'BA' registration of G-BOAG. However the following year, during a C Check, it was decided that due to spares shortages, and the closure of the LHR-BAH-SIN route, there just was not being enough work for seven aircraft, and therefore G-BOAG would be withdrawn from service. (In terms of spares, BA at the time for instance only had six sets of aircraft galleys, as aircraft went in for C checks the galley was 'robbed' to service the aircraft coming out of it's own C check). The aircraft was parked in a remote hangar, and was only visited when a component had to be 'robbed' for another Concorde, and the aircraft soon fell into disrepair, was filthy externally and became a really sad sight. Many people (not myself I might add) were adamant that G-BOAG would never fly again. However, in 1984 things had really started to improve for Concorde, with the charter business increasing and the LHR-JFK route in particular becoming a staggering success. It was decided that OAG would be returned to an airworthy condition. In 1985, with a fresh new interior, and with the new BA colour scheme, she was finally returned to service; and remained as one of the mainstays of the fleet right up to the end of Concorde services in October 2003. She now resides at the Boeing Museum of Flight in Seattle. (I have particularly fond memories of G-BOAG; in a previous post I mentioned flying through an electrical storm in late 1991 over Saudi Arabia, while returning from BKK-BAH to LHR. What I forgot to mention was the spectacle of DOZENS of fierce fires burning on the ground, towards our starboard horizon. These were Sadams oil fires, still burning in Kuwait. It made a sombre contrast to the amazing electrical spectacle right in front of us).

As far as low speed flying control activity was concerned, this was a combination of the fairly flexible outer wing sections, being buffeted by low speed turbulence (the wing tip tanks 5A & 7A also being empty), as well as some autostab inputs. This was perfectly normal, and part of the design our aircraft. However the development aircraft had even more flexible outer wing sections, which used to almost straighten up in high speed flight. However due to fatigue concerns, external lateral stiffeners were added to the underside of the wings during production of the airline aircraft. (these can be easily seen from underneath the wings, just outboard of the nacelles). Unfortunately these external stiffeners also resulted in over a one tonne fuel penalty to the production aircraft, due to increased weight, as well as higher drag in a critical part of the wing aerodynamic surface.

Dude :O

[Nick Thomas]

Hi canuck, I must admit to being rather jealous that you flew on Concorde! Your questions are particularly interesting as they arise from personal experience. Then to discover that M2dude was involved in overcoming the problem and explains it all so clearly is a delight.
Landing Concorde must have been "quite interesting". When ever I see videos of it; I always wonder how high up the eyeline of the pilots are compared to other airlines and especially when compared to the eyeline of a 747 pilot?(when the main wheels touch) I guess this must change the view of the runway when crossing the threshold. If so was special training required to overcome this as I would have thought that it would initially be tempting(though ill advised) to cross the threshold at too low an altitude? I know that the FE would call out the radio altimeter heights on landing but it must at first be difficult to disbelive the evidence of your own eyes.
I think am right to assume there were no spoilers so on landing did the act of bring the nose down spoil the lift or is that the reason why the non flying pilot pushed the yolk forward once she was down?
Thanks
Nick

[galaxy flyer]

Nick

What we are looking for is "eye-to-wheel" for the Concorde v. The B747. My question is were there ever turbulence problems at Concorde levels and speeds? Also, did the Concorde crews ever have to deviate around weather or slow down?

GF

[M2dude]

Nick Thomas
This of course is one for one of my pilot friends to answer properly again, but as galaxy flyer says, it's an 'eye to wheel' issue here when compared to other aircraft.
galaxy flyer
Again best answered by learned gentlemen such as my friends EXWOK or Bellerophon, but to the best of my feeble knowledge a resounding NO, at least as far as CRUISE flying was concerned. As the majority of the flight was carried out between FL500 and FL600 there was really no weather as such to avoid during supercruise. (As has been previously posted, at Mach 2 you would invariably be above FL500). Only at extremely low latitudes where the tropopause could theoretically extend up to around 70,000' was there ever any chance of seeing any cloud anywhere near your cruise altitudes. The only turbulence as such you would ever encounter was as the result of a temperature shear, but these never felt to be too much in the way of 'bumps' to me. And again, only at very low latitudes did you encounter severe shears anyway; anything encountered on the North Atlantic was generally very mild and civilised.
A CONCORDE PARADOX
The tropopause issue here is an interesting one, in that the coldest stratospheric temperatures we ever encountered were close to the equator, whereas the WARMEST temperatures possible are over the POLES:rolleyes: , where the tropopause can be as low as 22,000'. This is just one of the many paradoxes involving Concorde, and the reason why the aircraft would never be routed over the poles, BECAUSE THE DARNED TEMPERATURES ARE TOO HIGH, in terms of the stratosphere. The result here would be that the aircraft is temperature (Tmo) limited all the time to 127 deg's C. (I previously mentioned in another post in this thread that only 5 deg's C above ISA, -51.5 deg's C, would mean Tmo being reached at Mach 2; any warmer and we HAD to slow down) The relatively high polar temperatures mean that we are unable to fly anywhere near Mach 2. Another paradox would then come into play, the slower your cruise speed, the HIGHER your fuel burn. It was originally proposed in the early 1970's that Concorde would fly from London to Tokyo, and the routing for that needed two things: It could not be polar, and possibly just as important , you required a refuel stop. The Soviet Union amazingly proposed granting a supersonic corridor over Siberia, refuelling at the Siberian city of Novosibirsk. This was hardly an ideal routing (definitely far from a great circle) but was arguably one of the very few that was possible at all. This by the way was not some early iteration of glasnost, but the Soviets fully expected that flying thoroughbred, the TU-144 (bad dude:\) to be a success, and could compete side by side with Concorde.
ANOTHER CONCORDE PARADOX
If anyone wonders why when you flew faster you burned less fuel, it was primarily down to drag, actually a thing frighteningly termed as 'pre-entry spill drag'. As most people (???) are aware, the Concorde engine inlet utilised a series of carefully controlled and focused shockwaves to slow the air down entering the engine; in 14 feet of engine intake you lost in the order of 1,000 mph of airspeed! Now most of these different shocks varied with a combination of intake variable surface angle, intake local Mach number and also engine mass flow demand. However the oblique shock coming off the top lip of the intake produced a shock that varied with Mach alone, and would project downwards, just forward of the intake bottom lip. Due to the air downstream of this fairly weak shock still being supersonic, a measured amount of this air spills downwards, away from the intake. If you can possibly picture it, we have this wall of air spilling downwards over the lower lip of all four intakes, the combined effect of this supersonic forespill is a fair amount of drag. The faster we go, the more accute the angle of the shock and therefore the less air is spilled, and in consequence the lower the spill drag. Remembering that cool temperatures could produce a higher Mach number, temperature really could either be our friend or enemy, but cool was COOL :D
I hope this explanation does not sound like too much gibberish, but it really was a fact that 'More Mach = Less Fuel'. Hope it makes some sense.

Dude :O

[Totally_Bananas]

A small article in flight global suggest unspecified work is being carried out on the bristol based G-BOAF.

Any ideas/rumours?

[main_dog]

I always wonder how high up the eyeline of the pilots are compared to other airlines and especially when compared to the eyeline of a 747 pilot?

Yep I would be curious to know this too... from our FCTM for the B744, landing geometry on a 3˚ glideslope for a flap 30 landing at REF +5 and a 50' glideslope antenna TCH (Threshold Crossing Height): the pilot's eye should be at 66' with the main gear at 31'. Considering that during the flare the attitude will increase by 2˚-3˚ this distance can only increase, so I would hazard that a B744 pilot's eyes are in excess of 35' (10 metres) above the runway at touchdown (I wouldn't know, I usually shut my eyes at the 30' RA call-out, pull back a little and hope for the best:}).

Any idea what it is on that splendid machine that is Concorde? (I refuse to speak of it in the past tense)

MD

[galaxy flyer]

Maindog

That sounds right for the B747, the eye-to-wheel height for the C-5 at the THR was 34 feet.

GF

[ChristiaanJ]

I'll leave most of the answers to the pilots on this forum, but I can answer two small details.

During landing, Concorde isn't flared at all, it is flown onto the ground at a constant pitch attitude.
What does happen is that the ground effect over the last 50 ft or so of height considerably flattens the trajectory, so you do not touch down with the same vertical speed as during the final approach !
What also happens is that the ground effect produces a pitch-up moment, so the pilot has to push forward on the stick to maintain the same pitch attitude.

Putting the nosewheel down after touchdown is enough to completely “ruin” the lift, so that there is no need for “lift-dumpers” or spoilers.

CJ

[Biggles78]

in 14 feet of engine intake you lost in the order of 1,000 mph of airspeed
That answered the question I was going to ask. :{ Thanks for the explanation though. ;)

Were the Braniff crews trained specificially for Concorde or were they supplied as part of the lease package and what were they thinking flying a supersonic machine along the USA subsonic route? Marketing exercise???

[Brit312]

Biggles,

The Braniff crews [ I think it was 5 sets of crew] were trained for Concorde with some of crews trained in France whilst the others were trained in the UK. Flying training was done using an Air France Concorde
F-BVFA with flying being at Shannon initially but when they ran out of fuel it was moved to Montpellier. As their operation was to be subsonic they were only trained to operate the aircraft subsonically, but they were given a supersonic trans Atlantic trip as an observer.

ChristiaanJ

If I remember correctly ground effect tended to force the aircraft nose down, so requiring the pilots to pull back on the stick as if they were flaring ,but in fact what they were doing was as you say maintaining the pitch attitude constant. I have to say that in the early days the landing could be a bit of a hit or miss affair with some being perfect and some less so. The crews were originally taught to pull the power off in one stroke at about 15ft, but later they used to bleed it off and in my opinion this improved the landings greatly.

The problem with landing Concorde was when it got into ground effect if you let the nose drop you lost a lot of lift and arrived somewhat heavily. However if you pulled too hard you could raise the nose too much and suffer a big loss of speed causing a subsequent un-attractive landing, and you could also touch the tail wheel. This touch would be noticed by the ground engineer after landing as a scuff mark on the tail gear tyres. Therefore your friendly F/E on his external check prior to departure would always check the tail wheel tyres for scuff marks and if there were any you could inform the engineers at the other end of the trip that they were there prior to you taking the aircraft, and they would have to go and find another crew to blame


At touch down the pilots eye height was similar to that of a 747 pilot at touch down. Below 800ft when the aircraft had slowed down to landing speed the pitch attitude was such that the F/E could not see the runway ahead:eek:

[M2dude]

ChristiaanJ
During landing, Concorde isn't flared at all, it is flown onto the ground at a constant pitch attitude.
During AUTOLAND a flare manoeuvre was instigated by the Pitch Computer at 50' radio, where a fairly simple flare law was invoked. I seem to remember that the law , which used a combination of radio rate (from the RadAlt) and vertical acceleration (from the INS) gave you a commanded height rate of 10'/second at 50', exponentially reducing to 1.7'/second at point of main wheel touch down.
The autoland on Concorde was both extremely accurate and reliable, and an awful lot of guys said they hated using it 'because it can land the aircraft :mad: better than I can'; their words NOT mine. (Personally I never bought that one, the guys were just modest as far as I was concerned:ok:). This in my opinion is an absolute testament to the AFCS designers; ChristiaanJ and his colleagues at SFENA and GEC Marconi.
To give the complete final approach story; as the aircraft tracked the glideslope in LAND mode, the autopilot G/S deviation, like most aircraft, was geared as an inverse function of radio altitude, and at 75' radio this deviation was flushed down the loo altogether, leaving the A/P to hold radio rate for just a few feet. At 50' the flare was instigated, and at around 35' DECRAB was commanded, where the yaw channel would use a rudder input alone to 'kick off drift' and align the aircraft with the runway centreline. (Concorde did not employ a fwd slip manoeuvre in crosswind conditions, being a slender delta). The 'final' command was at 15' radio, when the autothrottle smartly retarded the throttles. (The Pitch Computer flare law of course continuing to control decent rate all the way down). On touchdown the autopilot would be manually disengaged and the nose gently (usually :p) lowered to the ground. (Concorde was only designed and certified as a CAT 3A system, so there was no automatic rollout guidance. However there was a runway guidance symbol on the ADI, which used a combination of Localiser deviation and lateral acceleration, to give you runway rollout track).
Now the flare law was tested every autoland, at G/S capture, and failure of this test resulted in the loss of LAND 3 status on the landing display panel. The most common defect of all with the Concorde autoland was in fact failure of the flare test, when at G/S capture, the previously illuminated LAND 3 indication would drop all of it's own to LAND 2. A simple changeover of autopilot paddle switches would nail the offending Pitch Computer, which would then be replaced before the next trip.

Dude :O

[M2dude]

Bigggles78
Brit312 has certainly answered your query about the Braniff crew issue; I remember being told that one of their captains, a Texan who allegedly wore big cowboy boots while flying, had an ambition at '3,2,1, NOW..' to KICK the throttles open with the sole of his right boot. Never did find out if this ever happened. :ooh:
The Braniff operation does seem a little crazy now, I must admit. They were supposed to have had long term ideas of serving the Pacific Rim with Concorde, it's a pity that we never got the chance to find out if that could have worked.

Dude :O

[Bellerophon]

Nick Thomas

... I think am right to assume there were no spoilers...

Correct.

...so on landing did the act of bring the nose down spoil the lift...

Yes, as with most conventional aircraft, reducing the aircraft pitch attitude (once the main wheels were on the runway) would reduce the angle-of-attack and therefore reduce the amount of lift being generated by the wing. Modern aircraft wings are very efficient and will still be generating a considerable amount of lift during the landing roll, even as the aircraft slows down.

Put simply, spoilers and/or lift dump systems are required to destroy this lift, in order to get as much of the aircraft weight as possible on the main landing gear, which, in turn, allows greater pressure to be applied to the wheel brakes before the wheels start to lock-up and the anti-skid units activate to release the applied brake pressure.

Concorde’s wing however developed very little lift at zero pitch attitude, so, once you had landed the nose wheel, there was no need for spoilers.


...is that the reason why the non flying pilot pushed the yolk forward once she was down?...

No.

The reason was that using reverse thrust on the ground on Concorde caused a nose-up pitch tendency, strong enough to lift the nose. The procedure was the handling pilot would call Stick Forward as soon as she had landed the nose wheel and the NHP would apply forward pressure on the control column to make sure the nose didn’t rise.

If the handling pilot applied reverse thrust before the nose wheel was on the ground, things could get very awkward very quickly.

Firstly, the nose would probably rise, quite possibly beyond the power of the control column to lower it. Secondly, the wing would still be generating (some) lift and so only reduced wheel braking would be available before the anti-skids kicked in, and the amount of runway left would be diminishing faster than normal.

The solution was to reduce to Reverse Idle power until the nose wheel was back on the runway, however, in the heat of the moment it was very easy to go through Reverse Idle and on into Forward Idle. Not only would this again hinder the deceleration of the aircraft, but it would also run the risk of scraping the reverser buckets on the runway (as the buckets moved from the reverse thrust position to the forward thrust position) so tight were the clearances between the buckets and the runway on landing.


Best Regards

Bellerophon

[Brit312]

M2dude,

The Braniff crews were great characters and yes many did wear cowboy boats, but the story I like is the one that goes as follows

After hours of briefing prior to going on the simulator [for the first time] the Braniff crew got on the sim and went through all their checks, started the engines and taxied out to the end of the runway for their first Concorde sim take-off. Everybody was strapped in with seats in the correct position and all checks complete.

The Captain called out "3,2,1, now" and all the throttles were moved sharply to full power and away we went with the visual showing the runway passing by at an ever increasing rate. Now the F/E had a couple of calls to make prior to V1 relating to how good the engines were performing the most important being at 100 kts, however before we got that far the Braniff F/E stood up in his harness and let out the cry " Gee Whiz look at the son of a bitch go".

Needless to say that take off was stopped and we went back to start again at the end of the runway

[db737]

Hey folks, I too have a wonderful love of the beautiful lady "Concorde"

I jsut fly the little ole 73 for Southwest. A former Braniff Captain, working as an instructor now(age 60 hit him); named Jerry white...has told me many fascinating stories of flying Concorde.:ok:

I could sit and listen to him all day long. :p

Not too long ago, fslabs released a version of Concorde for Microsoft flight sim FSX.

Don't know if any of you "Concorde" folks as well as others have seen it.
If not, take a look at Flight Sim Labs, Ltd. (http://www.flightsimlabs.com)

From what I understand, this is as close to flying a real Concorde as you can get. Marvelous bit of programming. I know a lot of the systems, flight model etc..were verified by former Concorde crews for accuracy.

Check it out when you have the time. :ok:

Now back to reading....

Best,
David

[Brit312]

db737,

I remember Jerry White, who did his Concorde training in Toulouse. He was a great bloke and and a good pilot. If you see him again send him by best wishes from the Brit F/E in Toulouse

[ChristiaanJ]

If I remember correctly ground effect tended to force the aircraft nose down, so requiring the pilots to pull back on the stick as if they were flaring ,but in fact what they were doing was as you say maintaining the pitch attitude constant.I'm sure you're right. The thing I wanted to stress was that there was a definite control input needed during the 'flare' to maintain a constant pitch attitude, but I did get the direction wrong....

M2dude,
Reading your description of the autoland, you must be quoting from documentation, no?
I've still got the AFM, but i don't think it's as detailed as that?
And for me it's now too long ago to remember it in full detail, without any documentation to cross-check.This in my opinion is an absolute testament to the AFCS designers; ChristiaanJ and his colleagues at SFENA and GEC Marconi.Indeed it was one of the things we were pleased about, getting it right, rather than the time wasted on the VOR mode (mentioned earlier).
BTW, it was still Elliott at the time.... both SFENA and Elliott have gone through a few permutations since.

CJ

[db737]

I've got training at the end of Sept....I'll be sure and tell Jerry you said hello.:ok:

Best,
David

[Bellerophon]

ChristiaanJ


Yes, as Brit312 has suggested, the pitch change as Concorde entered ground effect on landing was nose down.

In simple terms (i.e. as it was explained to me ;) ) due to the nose up approach attitude, (10½° PA) the wider trailing edge of the wing entered ground effect before the much narrower leading edge of the wing, meaning more lift was now being generated at the rear of the wing than before, aft of the CG, resulting in a nose down pitch change.

As you say, she landed at (or very nearly at) her approach attitude, with ground effect responsible for killing most of the rate of descent, but, during the last fifty feet or so, in order to maintain that steady pitch attitude against the increasing nose down pitch change, a definite, progressive, rearward movement of the control column was required, a movement that felt remarkably like a “flare” to the pilot.

The available pitch attitude range on landing was very tight. Depending on the approach speed selected, touchdown attitude typically would be 11° - 11½°, with a warning call of “Attitude” from the NHP at 12½° PA. On Concorde, effectively you only got one attempt at making a good landing, after that, with little room to manoeuvre (literally), you had to settle for a safe one, by making sure the wings were level, the rate of descent reasonable, and the pitch attitude within limits and just accepting whatever sort of touchdown she gave you!

The speed, pitch and tone of the F/E's voice, as he made the radio height calls, were as reliable an indication as any as to what sort of arrival was imminent!


Best Regards

Bellerophon

[ChristiaanJ]

Bellerophon,

Many thanks for filling one of the many current gaps in my memory!

I only "flew" her once, and that was on the original Filton development simulator.
Took her up to Mach 2.11, well into the "cricket" zone... never forgot... (I think that was some development issue we were trying to settle at the time).

I've been involved in a minor way with the restoration of both the Filton/Brooklands sim and the CDG/Toulouse sim, and with the SSTSIM and FlightSim Lab Concorde simulator programs, but never yet "flown" any of them.
Maybe it's time I should !

CJ

[M2dude]

BRIT312
Now the F/E had a couple of calls to make prior to V1 relating to how good the engines were performing the most important being at 100 kts, however before we got that far the Braniff F/E stood up in his harness and let out the cry " Gee Whiz look at the son of a bitch go".

This story is totally hilarious, can't quite get this visual out of my head. ('100 KTS, POWER SET' sounds so boring in comparison).:) I never had the good fortune to meet any of the Braniff guys; sounds like there was certainly a character or two there. It really is a pity that their operation never really got a chance to expand into the proposed Pacific Rim service, who knows, it might really have done something.
It's generally known that the BA aircraft were temporarily re-registered to facilitate Braniff's operation out of IAD to DFW; G-BOAA, B, D & E were re-registered from G-BOAA and so on, to G-N94AA etc. Being an older registration, G-BOAC was re-registered as G-N81AC. At IAD, the 'G' part of the registration was covered over, leaving a now perfect 'American' tail number. Only five aircraft were involved in the operation (at the time BA operated just six aircraft, G-BOAF was still at the manufacturers at Filton, and G-BFKW (later to become G-BOAG) was on loan from British Aerospace. In order for the necessary FAA certification, required for operation by a US airline, a modification package were required by the FAA. Some of these modifications seemed a little 'picky' and irrelevant at the time (they still do). However some modifications were certainly not in this category, and quite honestly should have been 'picked up' by the CAA & DGAC during original certification of the aircraft. As an example, if the flying controls had been operating on GREEN or BLUE hydraulics only (due to an indicated spool valve jam) and that particular hydraulic system was subsequently lost, there was originally no automatic switching to select the standby YELLOW system into the flying controls; the controls would have been completely unpowered until a manual selection was made by the pilot. . One of the 'FAA Mods' was to facilitate just that, so if this (extremely unlikely I grant you) scenario had occurred, then YELLOW would automatically been selected into the controls, and at no time would the controls have been in an unpowered state.
The Braniff operation ended in May 1980, due to heavy losses on the subsonic only route, and it's a rather sad irony that aircraft G-BOAF had been modified and reregistered at Filton, from it's original registration of G-BFKX to G-N94AF. Unfortunately the aircraft was delivered to BA in June 1980, one month too late to participate, and prior to delivery it's registration was converted to it's 'normal' British registration; all other aircraft also reverted to original registrations also.
ChristiaanJ
Reading your description of the autoland, you must be quoting from documentation, no?
Not really, being the sad b****d that I am, I still remember the Concorde flare law of: h+5h. = 0, so it was fairly easy to work out the programmed descent rates. (I did have to check the final 1.7'/second figure though). The rest I'm afraid is straight out of this sad old memory of mine.
Bellerophon
A brilliant description of the mechanics of final approach. It's so easy for us mere mortals to forget just what an involved and skilled process it was, to fly, and in particular land our totally amazing aircraft.

Dude :O

[telster]

Hi guys, just another SLF enjoying the thread...

How much cooperation was there between the two airlines in terms of training etc? Did any BA crews fly Air France aircraft for any reason for example? Were cockpit proceedures pretty standardised across the two airlines?

Cheers!

[Capt Chambo]

Great thread which I am thoroughly enjoying.

I seem to recall that Concorde was certified for the use of reverse thrust in the air. I also recall that it was "problematic".

Would any of the contributors like to expand?
:ok:

[EXWOK]

It was certificated - up to a point. Problematic? Maybe not, but it was a part of the flt envelope to be treated with respect.

Obviously there are no spoilers, and once you translate to 'vortex lift' (stalled in conventional terms) there is definitely no shortage of drag. (This happened at about 250kts at landing weight).

Supersonic - it was certainly no sailplane and an ability to increase drag wasn't required.

So - there is a bit of the flight envelope where you are subsonic, descending at about 350kts IAS, where you may need a bit of drag; e.g. to make the FL140 limit on the OCK 1A SID (as it then was) to LHR.

To facilitate this, engines 2 and 3 could be selected to reverse idle within certain strict limitations (most of which have now left my brain). The mechanism was to ask the SFE to arm the system on his panel and then to select reverse on the inboards. Where the system was slightly unreliable was that you were running the air-driven buckets with the engines at idle thrust - consequently they sometimes didn't make a full reverse selection, in which case you canx reverse on that engine and managed on one.

Clearly the big event would be if they didn't translate into fwd thrust, which is one of the reasons it wasn't done below 10 000'. I'm not aware of this happening.

To be honest it was only really used when ATC threw an alt constraint at you during the descent, because in general if you just pitched down to 380kts (Vmo when subsonic at typical approach weights) you would get the height off comfortably.

[EXWOK]

Question for engineering types:

I remember being told in my conversion course that the motors driving the secondary nozzles (buckets) were the fastest rotating devices on the aircraft. Is it true? Have you got a number for it? Was it really more than the gyro in the stby horizon?

If anyone has seen the video of AF landing at BZZ after the first post-grounding test flight, you may have noticed that you can hear the buckets translating to reverse even over the noise of the blustery wind and four Olympus 593's at idle.

[M2dude]

Capt Chambo
Concorde was, as EXWOK says, could use reverse in flight, on the inboard engines only, and only as far as reverse idle, the mechanism of which was quite complex and did on occasion not do work as advertised. Bear in mind here that the Rolls Royce Olympus 593 was a pure turbojet with no bypass, and so a hot stream reverser only had to be used; the reverser buckets acting directly on the efflux as it did any reverser in the 'old' days. Also the same buckets that were used for reverse were also progressively opened up between Mach 0.55 and wide open at Mach 1.1, this giving a vital control enhancement to the divergencing efflux. The overall effect of this was to give a true overall convergent/divergent nozzle assembly, the ideal for any supersonic aircraft.
As far as inflight reverse goes, the amount of HP compressor delivery air (P3) required to actuate the bucket airmotor in flight at an idle thrust settings, was quite minimal to say the least, and some help was definitely needed here. The moment that inflight reverse was selected (on the inboard engines only remember) the OUTBOARD engines would have their idle N2 automatically increased, and some of THEIR P3 air supply was also automatically ported over (via an isolation valve) to the inboard buckets. This whole process was required in order to give a little added muscle to the bucket airmotors, and give the system a fighting chance. Even this however was still not quite enough, the inboard travelling buckets required minimal air loading on their surface, and so the primary nozzles for the affected engines (the primary nozzle lived just aft of the LP turbine, aft of the reheat assembly) was automatically signalled wide open in order to assist matters here, by reducing gas velocity. One the buckets had reached full reverse the primary nozzle was then signalled full close (this applied for normal ground reverse also) and the automatic increased idle on the outboard engines was cancelled. To enable the described process to occur, provided all four engines were at idle, a solenoid latched button on the F/E's station could be selected. This signalled a circuit that enabled the selection of idle reverse on the inboard engines only, the opening of the P3 isolation valve, the raising of the outboard engine's idle and maximum primary nozzle angle for the outboards as soon as reverse was then selected..
The whole system was just a little fragile here; failure of either the extra air supply, or the raised idle on the 'other' engine was usually enough to stop the process working correctly.
EXWOK
While flying 'up front' I only ever experienced the use of inflight reverse once. (The captain was a bit of an Animal, if you flying guys see what I mean ;)). I would not say that it felt as if we'd hit a brick wall, as I'd expected the sensation to feel, more like we were flying into the dumped contents of a very large manure truck:O . The whole operation was so slick, we'd dumped the required amount of IAS more or less within a second or two, and normal thrust was immediately selected. As so often happened with you guys, you made it look too easy.
As far as the speed of the airmotor goes, I seem to remember that it was something in the order of 80,000 RPM at max chat; as you say faster (around twice as fast) as the standby horizon motor.
The basic core airmotor (not the whole assembly) was the same Garrett unit used on the P&W JT9 as well as the RB-211.

Dude :O

[M2dude]

telster
How much cooperation was there between the two airlines in terms of training etc? Did any BA crews fly Air France aircraft for any reason for example? Were cockpit proceedures pretty standardised across the two airlines?

One for the pilots really, but there was generally far less co-operation than you'd have thought. I never saw any cases of a BA pilot flying Air France or visa-versa. I know a couple of our guys had ridden jump seat on an AF aircraft, but that's all that I pesonally recall.
On the technical side of things there were meetings between the two airlines, both together and jointly with the airframe and engine manufacturers, but on a day to day basis there was precious little exchange of information, and you'd have thought that we (BA) were the only operator of Concorde, as I'm sure the AF guys felt the same also. In all of my 30+ years on Concorde, I personally went to CDG only once for an exchange of technical views and to help them out with an air intake defect.
I'm so glad that you are enjoying this post, it's great to have you here telster. (It's certainly forcing me to look deep into the dark corners my poor old grey matter).

Dude :O

[Nick Thomas]

Hi
I have yet another question! Last year I watched a programme where James May went up in a U2. He explained that at FL700 the plane was flying in "coffin corner" and that the difference in IAS between the stall and the max speed was only 10 knots. I understand that it's due to the very low air pressure at such heights. As Concorde could fly up to FL600 I wondered what this safe airspeed window was during the cruise/climb phase of flight and if this window was framed by the air pressure and/or the CofG position?
Once again thanks to everyone for such great answers and also for the background information.
Regards
Nick

[ChristiaanJ]

Nick,
Again I'll leave the full details to the real experts....

I saw that program with James May in the U2 too, so I know what you mean.
The "coffin corner" is the point for a subsonic aircraft where stall speed and limiting Mach number "meet" ; about 70000 ft for a U2, and considerably lower for an airliner. Either you stall, or you run into Mach buffet with control problems.

I'll try and find you a proper picture of the Concorde flight envelope (I have a few but one isn't scannable, the other is too ancient - preprod, yet another is 'buried' on a CD).

But nearly all of the edges and corners in that flight envelope "window" are a matter of certification.
You're not supposed to exceed M=2.04, Tt=127°C, IAS= 530kts, simply because of the "wear and tear" on the aircraft.
You're not supposed to go above 60000ft because your passengers might no longer survive a window blow-out.
You're not supposed to go below 300kts above 41000ft, don't know if that's a minimum control speed or linked to the engines...

Yet Concorde has been flown to Mach=2.23 and 68000ft without ill efect....
So the basic limitations are not linked to the classic "coffin corner" at all.

CJ

[norodnik]

I did experience reverse thrust (in flight) once and, as I recall, we needed to get down somewhat quicker than normal.

From my usual seat (25A) the airframe vibrated a good deal and you could feel that the descent was more rapid than usual.

However, after getting down we had to go twice (or maybe 3 times) round in the hold before lining up.

I always looked forward to holding as it was a little bit like being in a race car with the aircraft being powered round the loops all the time much like you would throw a go-kart round the track with full throttle and opposite lock. Normally I was out of luck as we usually went straight in.

[M2dude]

Nick Thomas
Just like Christiaanj I'm trying to dig up an accurate flight envelope diagram. (A lot of my Concorde 'technical library' is out on long term loan), but I would suggest that anywhere within Concorde's published flight envelope you never hit any equivilant to Coffin Corner, a la' U2. The whole issue is really one of air DENSITY, rather that pressure, where as you climb at a given Mach Number, your Indicated airspeed (IAS) falls away with altitude. (Velocity of sound being primarily tied to static air temperature). Now if you are climbing in the stratosphere, where temperature is more or less constant up to around 65,000', you can say that your TRUE Airspeed (TAS) is also constant with climb at a given Mach number. But lift and drag are functions of IAS (the equivalent airspeed that the aircraft would 'feel' at sea level) and not TAS. Because the U2 had a very low Maximum allowable Mach number (Mmo) as IAS fell away with altitude, it would get to the point where it's lowest permitted airspeed (we called this VLA) got to within a few knots of Mmo and severe aerodynamic buffering. i.e. you were screwed with nowhere to go but down :{.
In the case of Concorde, Mach 2 at FL500 was 530KTS, falling to 430KTS at FL600. Although we have less lift due to 100KTS lower IAS, the aircraft is now much lighter (this is the whole principal of cruise/climb) which keeps the universe in balance, but drag is now significantly lower too, getting us better MPG ;).
On the ASI, the only limitation displayed was Vmo; however the Machmeter did display fwd and aft CG limits at a given Mach number. The ONLY time that Concorde would experience relatively low speeds at altitude was at Top of Descent. I'm a little fuzzy here how it all worked exactly (it's an age thing you know), I'm sure one of the pilots can correct me, but I seem to remember that the autothrottle was disconnected, ALTITUDE HOLD was selected on the AFCS, and the throttles slowly retarded. (If you pulled back too far you'd often get a gentle 'pop surge' from the engines, and you had also to be wary of equipment cooling airflow too). The aircraft was then allowed to gently decelerate, still at TOD altitude, until Mach 1.6, when power was tweaked to give 350KTS IAS and IAS HOLD was selected. The aircraft was now free to carry out her loooong descent to 'normal' altitudes. VLA on Concorde was not directly displayed as you never flew anywhere near it, and also every pilot knew his VLA :p. (Stray into this and you'd get a 'stick' shaker warning.
I hope this blurb helps Nick

Dude :O

[telster]

Thanks M2dude, I'm sure you and your ex-colleagues are enjoying contributing to the thread as much as the rest of us are enjoying reading it! :O

[Nick Thomas]

Thanks CJ and M2Dude for such complete answers. When I was typing "air pressure" I knew it was not quite the right term; so M2dude thanks for explaining that the correct term is "air density".
Would I be right in thinking that TAS is different from speed over the ground? I presume GS would be TAS plus or minus wind speed.
Regards
Nick

[Bellerophon]

M2dude

Is this what you're looking for?


http://i303.photobucket.com/albums/nn142/Bellerophon_photos/scan0005.jpg

Best Regards

Bellerophon

[Shanewhite]

Although generally ignorant about aircraft, I have been absolutely rivetted by this thread, and can only sit in awe at the complexity and perfection that has been revealed here.
I've pretty much managed to keep up with the principals and technicalities involved, but there is one thing I don't understand. Could you explain to a complete novice the relationship between IAS, TAS ,GS and Mach no.?
Apologies if this is obvious to most here, but you can't get away with writing such a brilliant account of such a wonderful aircraft without attracting the odd ignorant byestander!

[SilverCircle]

This thread deserves an award...

I'm not a professional pilot, just a humble owner of a PPL with a very strong interest in aviation and a long time reader here (esp. in the Tech Log board). I've never posted here, because I prefer to read and learn from those who know it better, but this thread has finally managed to lure me out of lurking mode :)
If anyone has seen the video of AF landing at BZZ after the first post-grounding test flight, you may have noticed that you can hear the buckets translating to reverse even over the noise of the blustery wind and four Olympus 593's at idle.Like in this video?
YouTube - Concorde late 32 landing at Leeds/Bradford Airport (http://www.youtube.com/watch?v=AgmlLxS-EHc)

There is a strange high pitch sound that kicks in for about a second in the same moment the nose wheel makes contact with the ground and before the actual reverse thrust sound can be heard.

Thanks to all for sharing all this information about one of the most fascinating machines ever created by human mankind.

[ChristiaanJ]

Hi all,

Re the flight envelope diagram, Bellerophon got ahead of me, and his scan is cleaner than mine!

I've got a second one, which is basically the same, but has the envelope for a CG of 55% and for a CG of 59% hatched in.

http://img.photobucket.com/albums/v324/ChristiaanJ/Flightenvelope2w.gif

For anybody who wants the full scans to print them out in A4, use these links.

Flight envelope A4 format (http://img.photobucket.com/albums/v324/ChristiaanJ/Flightenvelope1c.gif)

light envelope w. CG limits A4 format (http://img.photobucket.com/albums/v324/ChristiaanJ/Flightenvelope2c.gif)

Apologies for the mediocre quality of the scans...

CJ

[mykul10]

Nice to see another Devon person here. I agree this is a great thread. Here is a simple explanation of airspeed.

A stationary aircraft, just like anything else is subject to static air pressure, which varies from place to place, day to day and decreases with an increase in altitude and.or a rise in temperature.

Once that aircraft starts moving through the air, it also experiences dynamic pressure which is the force of the air particles it meets as it moves. Of course the static pressure remains too, so the aircraft is experiencing static + dynamic which is called pitot pressure or total pressure. The laws of physics say that total pressure remains constant.

Indicated Airspeed (IAS) is a measurement of dynamic pressure which is described as 1/2 rho (rho is air density) X V2 (V= velocity). This is very important when talking about principles of flight (thrust, drag, stall speed etc)

Air density is a function of pressure and temperature, so if density (rho) is reduced V2 which is True Airspeed (TAS) has to have increased at a given IAS. (ie the same number of particles hit the aircraft in a given time)

In a nil wind situation TAS would be the same as your speed over the ground (GS). Groundspeed is then calculated by adding or subtracting wind speed from TAS. eg TAS 150kts, tail wind 20 kts = GS 170kts.

Fairly simple at low speeds. At speeds of 300kts and above the compressibility of air becomes an issue and has to be allowed for - the air is compressed as it stops against the aircraft. So TAS also includes an adjustment to compressibility.

Mach no is a percentage value of the speed of sound ie 0.85 = 85% speed of sound. Unfortunately the speed of sound changes with pressure but at sea level is around 760 mph and decreases as pressure decreases.

Aerodynamically things start going pear shaped as an aircraft nears the speed of sound as the airflow over parts of the aircraft can go supersonic. Aircraft approaching these kind of speeds have to fly mach numbers. Airliners typically fly Mach 0.80-0.85.

[Nick Thomas]

Thanks Bellerophon and CJ for posting the flight envelope. With regard to the CofG of 59%, I notice that the upper part of the envelope abuts the MMO boundary.So is the Cof G of 59% the determining factor for the MMO or is it some other factor?
Regards
Nick

[ChristiaanJ]

Could you explain to a complete novice the relationship between IAS, TAS ,GS and Mach no.?I'll try....

TAS (true air speed) is simple, it's the true speed of the aircraft through the air.

GS (ground speed) is equally simple, it's the speed of the aircraft over the ground i.e., TAS plus the component of the wind along the flight path. If your TAS is 1300 mph and you have a 100 mph tailwind, your GS will be 1400 mph.

Mach no. is TAS divided by the local speed of sound.
The speed of sound in air depends almost exclusively on the temperature: in a 'standard' atmosphere it's 760 mph on the ground at +15°C, drops to 660 mph at 37000ft / -57°C and remains constant above that height.

It's IAS (indicated air speed) that's complicated....

Lift, drag, control forces, stability, etc. are all proportional to the 'dynamic pressure' that the aircraft experiences moving through the air.
This 'dynamic pressure' is proportional to density x TAS squared.

Now take an aircraft flying along horizontally at sea level, say at 200 mph.
Lift = weight, so the aircraft stays on a horizontal flight path.

Take this same plane, without changing anything else, to an altitude where the air density is half that at sea level.

Dynamic pressure is now half, so the lift is half as well, but the weight is still the same, so the aircraft can no longer fly horizontally.

So what do we do... we increase the TAS until the dynamic pressure is the same as it was at 200 mph at sea level.
Half the density, so (TAS squared) has to be double, so TAS has to be increased to 1.4 (sqrt of 2) x 200 mph = 280 mph.

This is somewhat confusing for the pilot.... He flies the same aircraft, same weight, same angle of attack, etc. but not the same TAS... he'd have to mentally juggle airspeed and density (altitude) the whole time to maintain horizontal flight at different levels.

It would be much easier if he had an indicator showing dynamic pressure... and maintain that constant for different altitudes.
This is where IAS comes in.

Stick your hand out of a car window. The force you feel is due to the dynamic pressure.
Stick a tube, closed at one end, into the airstream and measure the pressure with a basic pressure indicator, that's your dynamic pressure.

Now the 'clever' bit. Mark your indicator, not in bar or psi, but in mph, so that at sea level it will indicate the same speed as the TAS (200 mph in the example).

Now, same as above, go and fly at an altitude where the density is half, with a TAS of 280 mph. Your indicator will still show 200 mph, showing you that the dynamic pressure, hence the forces (lift, drag, etc.) are the same as those at sea level at 200 mph.

So the 200 mph is your IAS, your "indicated air speed".

It's the IAS that tells you what happens to your aircraft in terms of the forces and aerodynamics, and that's why figures such as the Vne (never-exceed speed) or the stall speed are always in mph or knots IAS, not TAS.

As a matter of fact, a pilot is not very much interested in TAS as such, and most aircraft do not even have a TAS indicator.

It's not until you start approaching the speed of sound that TAS becomes important, and even then it's not TAS as such that's used but its relation to the speed of sound, i.e., the Mach number.


OK, Shanewhite, it's a long and complicated description, but maybe it helps?

CJ

Edit PS : I see mykul10 already had a go as well. So much the better, explanations from two different sides nearly always complement each other!

[Shanewhite]

Thankyou guys for your lucid explanations. Things are now a great deal clearer, and I now understand how you can be doing 550 knots at Mach 2, which previously seemed impossible!

Now, more about that beautiful machine, please...

[EXWOK]

Nick:

So is the Cof G of 59% the determining factor for the MMO or is it some other factor?

The top of the boundary is FL600, largely an artificial number - the airframe is good for rather higher than this, but I believe air supply and ramp scheduling could become an issue not so far above this level.

Mmo - ditto. As others have said, Mmo was originally going to be higher (M2.2) but was reduced to extend fatigue life as the aircraft design 'grew'.

The significance of the shaded 59% portion of the graph is that it shows the envelope at that CG - in this case the relevant line is the bottom of the shaded area - M1.56. This is the MINIMUM mach number that can be flown with the CG at 59% (normal for supersonic cruise). You will see it represented on the Machmeter (a few pages back) as the "AFT" bug. i.e. you can't fly slower than this without moving the CG forward.

So it can be seen that the decel must be done in concert with CG transfer - and as (mostly) always the designers had made it as straightforward as possible. Transferring forward from Tank 11 using the two electric pumps the rate of txfr pretty well matched the standard decel profile, leaving the FE to make the occasional tweak to keep the flight envelope in concert with the CG envelope through the decel/descent.

In the case of abnormal procedures depriving one of electrical power then some other way had to be found to enable a descent (which required a decel) and that is why there are also two hydraulically driven fuel transfer pumps in tank 11.

It's a bit confusing at first, but there are two overlapping flight envelopes - the speeds/alts drawn on the basic envelope and those determined by the CG postion at the time.

In practice - one had a takeoff CG, a landing CG, a subsonic crz CG, a supersonic cruise CG and the only area one had to keep a close eye on was the transition between the last two. There were several visual and aural warnings to back up the CG and Machmeter bugs.

[ChristiaanJ]

With regard to the CofG of 59%, I notice that the upper part of the envelope abuts the MMO boundary.So is the Cof G of 59% the determining factor for the MMO or is it some other factor?Nick,
No... for the manual they've just hatched the limits for a couple of example CGs inside the existing overall limits.
It's the M=1.56 limit that's related to CG, the Mmo=2.04 boundary is purely certification-related.
I think the CG "corridor" is already posted, if not I'll do so.

It's more the other way around... the aft CG limit is 59% for anything above about Mach 1.5.

CJ

[EXWOK]

For the sharp-eyed who may have actually gone back to look at Bellerophon's picture, you may note that the AFT bug is lower than M1.56, contrary to the flt envelope above. Billy ruffian will know for sure, but here's my surmise:

FL600 level flt means he was going to BGI. The length of this sector was, in crude terms, about 200NM more than the quoted max range of the aircraft, so the range envelope was being pushed a little.

Because there was no land you could stay supersonic all the way, so at the end of the cruise you would be supersonic, but with relatively little fuel in the tanks, and most of it in Tank 11 (at the back) to keep the CG aft. Even with a tweak to tanks 1&4 to run them at 50% level, eventually the CG would come forward as you burnt fuel out of tank 11. That's what is probably happening in Bellerophon's photo, hence the 'AFT' Mach bug being at a lower Mach. If the FCPI ('ICOVOL') was in the frame I wager you would see the elevons a somewhat above the optimum 1/2degree down position

The bugger was this; if you were a little tight on fuel, just when you wanted to maximise the time spent supersonic you'd have to start an early decel because there just wasn't enough fuel left to maintain the CG far enough aft to sustain M2.

All part of the fun, and why every sector was interesting and rewarding.

[ChristiaanJ]

EXWOK,
On Bellerophon's picture, it looks as if the FWD bug on the Mach meter is still at about M=2.2.... and just the barber pole at about M=2.04 as you would expect.
At that exact point in the picture I think he just hit his head against the ceiling... (FL600) but could still stay there a bit more.

Doesn't change any of your other comments, though.

CJ

[EXWOK]

Oooops - thanks for pointing out my AOT logic there. Note to self: don't post after returning from a night flight!

The other reason for the disparity of bugs on the Machmeter vs the flt envelope is whether they relate to the first or second M/CG warning. I can't remember and don't have the manuals to hand. I do recall that it was more accurate/practical to monitor the speed-driven limits on the CG indicator rather than the CG-driven limits on the machmeter.

[Bellerophon]

shanewhite

Following the excellent explanation given by ChristiaanJ about the relationships between OAT, Mach number, TAS and IAS (which I have now copied and shall shamelessly pass off as my own work in future ;) ) if you wish to see how these relationships work in practice you might look back at the photo posted at reply #66.

You will see that at FL600 the aircraft had a GS of 1,139 kts whilst flying at M2.00 and an IAS of 429 kts.

We don’t know what the wind was, nor what the TAS or OAT were, but we can easily deduce that:


If the OAT was standard at FL600, at -56.5°C, then, as at that temperature M2.00 equates to 1,147 kts TAS, in order to have a GS of 1,139 kts, she must have been flying into an 8 kt headwind.


If the wind at that altitude was calm, then her GS of 1,139 kts must have been the same as her TAS. For M2.00 to be 1,139 kts TAS, then the temperature at FL600 must have been 3°C colder than standard, at -59.5°C.


If, as was typical on a LHR-BGI sector, the OAT at FL600 was 10°C colder than standard, at -66.5°C, then M2.00 would equate to 1,120 kts TAS, so to have a GS of 1,139 kts, she must have been flying in a 19 kt tailwind.


For obtaining Mach/TAS/Temp values quickly and easily, as well as other useful information on the atmosphere, this (http://www.digitaldutch.com/atmoscalc) Standard Atmosphere Calculator website is extremely useful.

Best Regards

Bellerophon

[atakacs]

Supersonic - it was certainly no sailplane and an ability to increase drag wasn't required.

Makes me wonder... In the event of a complete loss of thrust at Mach 2 (say fuel contamination) would the deceleration be significant ? If so I guess the fuel redistribution / pumping to maintain acceptable CG would become interesting...

[ChristiaanJ]

Quick link to Bellerophon's post #66 and photo to save you having to 'leaf' back...
G-BOAE at Mach 2 (http://www.pprune.org/tech-log/423988-concorde-question-4.html#post5885515)

You will see that at FL600 the aircraft had a GS of 1,139 kts whilst flying at M2.00 and an IAS of 429 kts.Much as I look at that picture, I can't see the groundspeed.....

Ah, oh, ooooops!!!! Of course it's there, in the little window on the top right of the HSI (Horizontal Situation Indicator, the lower one of the two big central instruments).

Shanewhite, in a way, that illustrates that for flying the aircraft things like TAS and GS are not really that important... that's why there are no big instruments indicating TAS or GS, but only IAS and Mach, with only a little digital window for GS, which IS important for navigation (largely handled by the inertial navigation system, which is the system where the GS display comes from), but not for the minute-to-minute handling of the aircraft.

Bellerophon, dumb question from a techie... the 373 miles is presumably just the distance to the next INS waypoint?

CJ

[HarryMann]

Mykul10
Mach No is a percentage value of the speed of sound ie 0.85 = 85% speed of sound. Unfortunately the speed of sound changes with pressure but at sea level is around 760 mph and decreases as pressure decreases.Small correction

....sound. Unfortunately the speed of sound changes with (Abs) temperature but at sea level is around 760 mph and decreases as temperature decreases.

M (dry air within reasonable temperature limits) = Sq.Rt (Gamma x R* x Tabs)

R* is a combined gas molecular value
Gamma is 1.4 (truly adiabiatic compression wave)

[old,not bold]

I have two recollections which I treasure. The first is of a sales demo ride for a VIP party I had to organise from Abu Dhabi on 29th August 1974; one by one we went to the flight deck to look around, which is when I first saw the gap by the F/E panel as the skin stretched. The flight took us overhead Dubai and then halfway to Bombay with a level turn at M2 and back along the outward track. The contrail was close by the RH side and gave a tremendous impression of what the speed really meant.

Some 13 or 14 years later I had the privilege of a jump seat ride from Exeter for the whole of one of the round-the-bay flights. We flew North to join the westbound route to the acceleration point at minimum separation behind the schedule Concorde to New York (or perhaps Washington?). The display as the other aircraft's nose lifted and the aircraft accelerated was awesome.

Then on landing, handflown by the FO (currency requirement?), we seemed to be heading for a touchdown halfway down the runway. It was truly terrifying to a simple PPL, and just as I was about to let out a strangled sob the mainwheels touched down precisely on the markers, well below and behind. Apart from the terror, what impressed me was that as far as I could see the FO was flying the aircraft exactly as you would a Tiger Moth; stick, throttle and rudder. I know that there was far more to it than that, but that's how it appeared.

What a gorgeous aircraft. My model, in its original Gulf Air colours as presented in 1974, flies in the ceiling of my office.

[Nick Thomas]

Once again thanks to everyone who has patiently answered my questions. I have certainly learnt a lot about Concorde over the last couple of weeks.
I also agree with many other people who have said that the valuable information provided on this thread should be recorded for posterity. Not an easy task as she is such a wonderful and complex machine. Mind you I think that such a project would be worthy of a Heritage Lottery grant, I say that as in my "real life" I have had experience of how Lottery grants are awarded.
Regards
Nick

[M2dude]

http://i991.photobucket.com/albums/af32/riconc1/Concorde/CGlimits.jpgHi guys, here is a schedule showing CG against Mach number (It's very old just like the author here). I hope that it now completes our collection of flight envelope diagrams. (Bellerophon, by the way, your diagram is precisely the one that I was scouring around for). Great explanations by everybody on the Mach/TAS/IAS etc issue, mostly all clear and concise ( a couple of minor goofs that were subsequently corrected, otherwise very good) .
If I were in the LEAST bit pedantic (and any here that know me would say that the b****d certainly IS :mad: pedantic), I would merely add that Concorde (like virtually all complex aircraft) relied on CALIBRATED airspeed (Vc) and not IAS, taking into acount plate and probe errors. Just as well I'm not pedantic ;).

Dude :O

[Runaround Valve]

I believe that the main landing gear was shortened to fit into the wheel wells during the retraction sequence.
As I see it, as the gear started to retract, the oleo`s were compressed to something like when the weight was on the wheels. Then a latch would have been applied before the gear reached the full up position to hold the gear strut compressed.
I would like to find out more how this was accomplished.

[M2dude]

ChristiaanJ
....... in a way, that illustrates that for flying the aircraft things like TAS and GS are not really that important... that's why there are no big instruments indicating TAS or GS..
It was one of the strange little differences between the BA and Air France aircraft that the French had a small digital TAS indicator (on the lower F/O's instrument panel) and BA had none.
As you rightly say, as an indicator TAS is not that much use to you, BUT TAS is vital for calculating wind speed/direction within an INS/IRS system, hence that is why any air data computer gives a TAS output to the INS or IRS.
dumb question from a techie... the 373 miles is presumably just the distance to the next INS waypoint?
Nothing dumb about the question (I wonder if you are even capable of such a thing ChristiaanJ ;)). Yes, the distance window on the HSI related to the next INS waypoint.

Dude :O

[stilton]

M2Dude,


You mention a minor instrumentation difference between the AF and BA Concordes.


Were there any other technical differences between the two Airlines respective Concorde Fleets that come to mind ?

[M2dude]

Stilton
Hi again my friend. There were a few; BA used a Delco Carousel 4AC INS, where AF used a Litton system. BA updated the radar to a Bendix sytem, where I believe that AF retained the original RCA fit. (The RCA radar was awfully unreliable (rubbish actually, and very expensive to fix) , although most of the guys would agree that it gave a superbly detailed picture, better for mapping than the Bendix.
BA used quite a sophisticated Plessey integrated flight data system, where the AF recording system was a little simpler.
There were various other minor differences, but I think that's just about it.

Dude :O

[M2dude]

Runaround Valve

I believe that the main landing gear was shortened to fit into the wheel wells during the retraction sequence. As I see it, as the gear started to retract, the oleo`s were compressed to something like when the weight was on the wheels. Then a latch would have been applied before the gear reached the full up position to hold the gear strut compressed. I would like to find out more how this was accomplished.

This was quite a neat system, as the gear was retracted, a SHORTENING LOCK valve was signalled, allowing a relatively tiny jack to pull the entire shock absorber body into the body of the oleo progressively as the gear retracted. So the shock absorber itself never compressed on retraction, more like the whole shooting match was pulled inside the body of the oleo. On the ground the shortening lock was disabled, and also isolated by a geometric lock, the weight of the aircraft on the leg holding the shortening mechanism over centre.centre. Hope this helps.

Dude :O

[M2dude]

I hope this one is interesting; it's a Rolls Royce diagram illustrating what the wildly varying differences were in terms of the engine between take off and supersonic cruise. The primary nozzle can be seen at the rear of the engine, together with the reheat assembly and the secondary nozzle (reverser buckets).
Yes ChristaanJ, I FINALLY managed to upload stuff here.:Dhttp://i991.photobucket.com/albums/af32/riconc1/1Olympus.jpg