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

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

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?

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.

yoke feedback
 

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.

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.

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. :)

Biggles78
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

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!

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

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

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

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

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

I think this is it....

YouTube - Concorde British Airways take-off

CJ

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

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

Attitudes
 

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.

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

YouTube - Concorde: Last Takeoff From JFK Airport With Live Commentary

Modern LSI surface mounted, multi layer electronics.
 

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.

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.

Rather than me waffling and doing cut-and-paste, just look here :
Concorde "B"
Concorde '217' would have been the 'prototype' for the 'B' version. Sadly it never happened.
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

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

CJ

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

Not the autothrottle board in question, but one of the same size and technology.

http://img.photobucket.com/albums/v3...1280007w-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.

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

Landroger
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

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

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

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

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 ?

ChristiaanJ and M2Dude
 

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:

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.

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

Roger.

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:

... 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

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

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:

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.

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/v3.../04100004w.jpg

LandrogerThey'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.
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.
I 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/v3...1280008w-1.jpg

This is the central connector closer up

http://img.photobucket.com/albums/v3...1280009w-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/v3.../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

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

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'.

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

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

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

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.
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...
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.
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

Any magnetic core memory in any of those systems?

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