PPRuNe Forums

PPRuNe Forums (https://www.pprune.org/)
-   Tech Log (https://www.pprune.org/tech-log-15/)
-   -   Concorde question (https://www.pprune.org/tech-log/423988-concorde-question.html)

galaxy flyer 21st Aug 2010 03:48

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 21st Aug 2010 05:51

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 21st Aug 2010 09:41

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

M2dude 21st Aug 2010 10:47


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').
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).
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 21st Aug 2010 14:40

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?


ChristiaanJ 21st Aug 2010 15:12

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 21st Aug 2010 15:57

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 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 21st Aug 2010 16:04

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 21st Aug 2010 16:11

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 21st Aug 2010 16:42

Originally Posted by ChristiaanJ
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 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 21st Aug 2010 17:22

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 21st Aug 2010 18:52

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 21st Aug 2010 21:03

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 21st Aug 2010 21:26

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 21st Aug 2010 22:04


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


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 22nd Aug 2010 01:47


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 22nd Aug 2010 02:02


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 22nd Aug 2010 02:09

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 22nd Aug 2010 02:11


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 22nd Aug 2010 03:45

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.


...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.


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.

All times are GMT. The time now is 12:25.

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.