Posts about: "Afterburner/Re-heat" [Posts: 110 Pages: 6]

tristar ,
The question is less odd than it seems....
With full take-off power plus reheat, Concorde could not be held on brakes alone (hence the various procedures at take-off).

Maybe somebody has the full story.... in the light of chocks being less than perfect....

CJ

I cannot imagine any requirement for more than one engine (with or without reheat) to be run at full power when parked in the detuners. Thus there would be very little chance of exceeding the brake torque limits.

ZimmerFly said
I cannot imagine any requirement for more than one engine (with or without reheat) to be run at full power when parked in the detuners. Thus there would be very little chance of exceeding the brake torque limits.

Brake torque us only one of the things you have to think about when running at high power.

Consider running an engine on one side with all the others at idle or even shut down, what do you do when the aircraft starts to slide sideways?

The engine run drills call for "balanced" power. What this means is that you have to balance the power which means running the opposite engine at high power also.

Been there, done that!!

tristar 500

What was the minimum maneuvering speed for Concorde
It was expressed in the flight manual as "Lowest Authorised" speed, Vla, and didn't depend on weight. 0-15,000' Vla=V2 or Vref as appropriate, 15,000'-41,000' Vla=250kias, 41,000'-60,000' Vla=300kias

Also what was the typical climb speed I'm guessing you mean rate of climb rather than IAS?
- At lift-off? From memory Vr was around 200kts, V2 around 220kts and if restricted to 250kts (way below min drag) you'd get pretty poor rates of climb - about 1000fpm if you were lucky and IIRC - you'd quickly want to lower the nose, just barely climb and get her up to 400kts when she'd really fly...
- Once 240 kts is achieved? see above - but once you got her up to min drag (about 400kts at MTOW) things went better - about 4000fpm without reheat
- At minimum maneuvering speed at typical takeoff weight? At V2 she staggered up due the the drag of the slender delta wing at low IAS - but climb performance on three engines (in contingency reheat) at V2/MTOW was better than a conventional subsonic jet on three / MTOW / V2 due to conservative certification requirements of the TSS
- At MTOGW? Does the above answer your Q? Happy to add more if you need...

Edited to add, most transatlantic takeoffs were at MTOW - around 185 tonnes - and due to the slender delta aerodynamics, weight didn't affect performance as much as a conventional wing anyway because induced drag was the bigger player at slow speeds - and I've just completely exhausted my very limited grasp of aerodynamic engineering!!

<< I'm guessing you mean rate of climb rather than IAS? >>
<<No, I meant the airspeed you'd be flying at while climbing (post takeoff)>>

OK, then the answer to your Q's:
Also what was the typical climb speed
- At lift-off? About 200kts
- Once 240 kts is achieved? 240kts
- At minimum maneuvering speed at typical takeoff weight? Vla after takeoff was V2 until 15,000'. I.E. about 220kts
- At MTOGW? V2 didn't vary much by weight

Out of JFK we flew at Vmo once further than 12nms from the coast. Vmo=400kts IAS at low level.

Out of LHR overland the IAS restriction was 300kts until past the speed limit point early in the SID - much less draggy than 250kts and hence better climb rates. But you'd quickly be released to get to 400kts (barder's pole) where it was designed to be flown.

<<Why higher speed? That have to do with shockwaves and the resulting pressure distribution differences?>>
The flight envelope was bigger and more complex than subsonic types: it was developed in flight test and probably had many considerations involved. I think someone posted it earlier in this thread in graphical form (from the flight manual) if you want to see it. In practice, you had to be aware of three basic parameters - IAS, Mach and CG position (the CG "corridor"). Once understood, it wasn't that difficult to keep up with it...and the IAS and Machmeters had barber's poles handily programmed to show the limiting values (including, cleverly, max temp on the nose Tmo=127 degrees celcius).

Regarding climb rates - best ROC was at 400kts (MTOW) or 380kts (MLW). As speed reduced below that, drag increased and ROC reduced. At MTOW and 400kts you'd get about 4000fpm max dry power. At 250kts it was all noise and very few feet per minute - after noise abate procedures you had to lower the nose, just barely climb, and get IAS up toward min drag as soon as possible. With an engine failed go for 300kts minimum - Vmo as soon as you can.

<<shockwaves and the resulting pressure distribution differences>>
You had to avoid the "transonic" region due to these effects: maximum subsonic cruise was 0.95M due to the auto-stabilised flying controls become over-active as shockwaves started to "dance" around the airframe (usually asymmetrically). This calmed down by about 1.3M in the acceleration (when the intake ramps started to do their thing). To accelerate to 2.0M you needed reheat until 1.7M so you didn't hang around between 0.95M and 1.7M. FL260 was best for subsonic cruise because at that level 400kts IAS = 0.95M...

Hi all,

I'm a humble PPLer, and have been (speed) reading the last 70 pages...a fabulous story, of engineering and operational excellence, which I will read again at length when time permits.

I have only seen Concorde in the flesh on a few occasions...generally while passing through LHR.

But in October 2003, I had the privilege to watch the final Concorde take-off from Belfast at close quarters. I was standing at the GA Apron at Aldergrove as she took off on runway 07, actually getting off the ground barely 150yds from where we stood. I was among a crowd of local aviation buffs, all of whom had managed to cajole, bluff, and persuade their way into the GA area to see her go. And it was awesome. The afterburner roar rippled through my body, the noise was deafening, the reheat flame was mesmerising, but above all she was a beautiful creation.

Art comes in many forms, and to my mind, Concorde was up there with the works of all the great masters.

Nice one guys. I honestly is a pleasure to share my experiences (and feeble knowledge) of the aeroplane with so many wonderful people here, be they aviation professionals, former supersonic SLF or just inerested enthusiasts. Guys and gals, just keep posting away here and remember there is no such thing as a stupid question.
Unless of course it's from me. 'What pert of the aeroplane was manufactured by a division of General Motors in the USA?'.
Oh Shaggy, can't claim credit for the 3/4 flag, or reheat capability indicator', but I remember having a right chuckle when we fitted this highly comples piece of precision engineering ( ) in the early eighties. I thought it was some kind of belated April Fools's joke.

Hi Philflies
The 3/4 tab mounted by the #4 EGT indicator had in fact nothing to do with the EGT indication at all. It wasa reheat capability indicator and was set by the crew prior to take off. Set to 4 meant that all 4 reheats were required for take-off (and if one failed it then meant that the take-off should be rejected). Set to 3 it meant that a single reheat failure could be tolerated and the take-off could continue.
I hope this helps Philflies.
Oh and check out the website BRINGING CONCORDE G-BOAC BACK TO LIFE - Welcome The fat lady aint singing yet. Also check out the Concorde comes alive thread here too.

Philflies ,

M2dude is right, and IIRC there is already a description of this much earlier in the thread.

The background of the 3/4 tab is, that
... on most aircraft you can - at the start of the take-off - 'run up the engines against the brakes', check they all deliver full power, and release the brakes only then.
... on Concorde it was impossible to 'hold the aircraft on the brakes' while going to full t/o thrust including the reheat (not so much because of insufficient brakes as insufficient 'footprint' of the wheels, IMHO).
... so, full t/o thrust (including reheat) didn't occur until the aircraft had already started the take-off roll.

If, at that point, one of the four reheats didn't light (which did happen at times), you did not have an awful lot of time to decide on whether you could continue 'on three' or had to reject the take-off.
Rather than having to check your pre-flight take-off calculations in a sheaf of papers or rely on your memory of the briefing, that little Heath Robinson "3/4 tab" gadget told you instantly whether to RTO NOW, or whether you could continue the take-off.

Sorry to repeat an old story, but Philflies asked the question, and not everybody has read the entire thread.....

Christiaan,
Just to add a bit more to your explanation is that

The reheat decision speed on every take off was 100kts

If the little tag showed 4 then you needed 4 reheats at 100kts to continue
the take-off

If the little tag showed 3 then at 100 kts you could continue the take-off even if one reheat had failed

If above 100kts you could always continue with the take off, even if a reheat had failed [ always required 3 reheats working]

So if it was a "3 reheat day" and a reheat failed prior to 100kts then a further reheat failure between 100kts and V1 would require the take off to be rejected.

Hope that makes sense??

Humble aplogies to all, of course its mounted by the #1 EGT gauge (ANOTHER senior moment on my part). The RCICS, Reheat Capabilty Indication Control Sub-system (Oh OK then, I just made that up ) was fiitted in the very early days of Concorde operation. It looked at first sight a belated April Folls joke, but as was said (much) earlier prior to this amazing piece of technology the #3 INS CDU waypoint thumbwheel was used as the reheat GO/NO-GO indicator.
And NB2A, no apologies needed from you sir. A great link to the video starring Dave Rowland and Roger Bricknell (sorry Les).

Best regards to all
Dude

Anyone got \xa31.25m under the sofa?

Concorde Rolls-Royce Olympus 593-610 Turbojet Engine with Reheat | eBay

Thanks ChristiaanJ#1508 and CliveL#1509. That's what I thought. It was the quote in #1504 that implied left and right handed engines with all the stock problems that would cause.

At risk of thread drift I think that anything with propellers would be likely to suffer much more from asymmetry, but I think folk just put up with it - except in the few cases where there are contrarotating propellers.

Am I right in thinking that once the necessary minimum rpm was achieved, reheat was selected on all four engines, but that some (automatic?) control restricted the power to engine#4 until 60kt was achieved?

Wow, what an amazing thread which I have only recently found.

Congratulations to all for a fascinating read

Although I never got the opportunity to fly on Concorde, I will never forget seeing her fly some charters from Filton in the late 1990's. On one occasion I was stood at the wire fence at the end of runway 27 and watched Concorde taxi directly towards me, do a 360 degree turn and line up for takeoff. Concorde was only around 100ft-150ft away from me when the throttles were opened. Luckily I was holding tightly onto the fence and got a face full of dust as the reheats kicked in! The noise, power and heat I felt from those Olympus engines was phenomenal. She looked stunning as she rotated amongst the heat haze and the slender delta climbed steeply away towards the Bristol Channel. What an aircraft!

My grandfather worked on the Olympus 593 engines at Rolls Royce in Filton, so I will always hold Concorde close to my heart. I have been onboard Foxy at Filton when she was open to the public and I have visited 002 at Yeovilton and 101 at Duxford. I live quite close to Delta Golf at Brooklands and have been onboard her about 4 times now (including a sit in the cockpit) and recently flew the fantastic Concorde simulator with Captain John Eames and First Officer Ian Smith which is a day I will treasure. Opening up the throttles for take-off on 31L at JFK and tackling the checkerboard landing at Kai Tak were experiences I will never forget.

Keep up the great postings everyone!

Just for theories sake, if there were no noise, speed or boom considerations what would be the optimum profile for Concorde to fly after departure ?



In normal service I understand it had to comply with normal noise abatement departures, speed limits and remain subsonic until far enough from land to prevent the boom being a consideration.


But what if it could accelerate immediately, with no restrictions of any kind ?


I imagine you would stay in afterburner, accelerate to VMO and on to M2 in the climb ? or would airframe heating at lower altitudes prevent this ?



Lastly, was this ever done in testing, or for example leaving Barbados ?

For the french speaking (or reading) people here, I just found a mine of very interesting informations about Concorde on this website:
Accueil
This site has a database of thousand of concorde flights with the following datas: Date and time of the flight, airframe used, technical and commercial crews, guests, departure/arrival airports and flight type (regular, charter world tour...).
On top of that, many infos and stories around Concorde can also be found there.
I can't resist to translate one of those stories (I'm far from being a native english speaker or a professional translator; so forgive me for the misspellings and other translation mistakes). It is a report about one of the biggest incident that happened to the prototype 001 during the flight tests:

Shock of shockwaves
We were flying with Concorde at Mach 2 since 3 month already on both side of the Channel. The prototype 001 did outstrip 002 which was supposed to be the first to reach Mach 2.
Unfortunately, a technical issue delayed 002 and Brian Trubshaw fairly let Andr\xe9 Turcat be the first to reach Mach 2 with the 001 which was ready to go.
The flight tests were progressing fast and we were discovering a part of the atmosphere that military aircrafts hardly reached before. With Concorde, we were able to stay there for hours although limited by the huge fuel consumption of the prototypes.
The Olympus engines did not reached their nominal performance yet and, most of the time, we had to turn on the reheat in supersonic cruise to maintain Mach 2.
The reheat is what we call afterburner on military aircrafts. Fuel is injected between the last compressor stage of the low pressure turbine and the first exhaust nozzle. This increases the thrust for the whole engine and its nozzle.
The 4 reheats, one for each engine, are controlled by the piano switches behind the thrust leavers on the center pedestal between the two pilots. Air was fed into the engines through 4 air intakes, one for each engine, attached 2 by 2 to the 2 engine nacelle, one under each wing. The advantage in terms of drag reduction was obvious.
However, tests in wind tunnel showed that, at supersonic speed, if a problem happens on one engine, there was a great chance for the adjacent engine to be affected as well by the shockwave interference from one air intake to the other despite the presence the dividing wall between the two intakes. So we knew that an engine failure at mach 2 would result in the loss of 2 engines on the same side, resulting in a lateral movement leading to a strong sideslip that would likely impact the 2 remaining engines and transform the aircraft into the fastest glider in the world.
This is why an automatic anti sideslip device was developed and installed on the aircrafts.
The air intakes are very sophisticated. At mach 2, it creates a system of shockwaves that slows down the air from 600 m/sec in front of the aircraft to 200 m/sec in front of the engine while maintaining a very good thermodynamic performance. In supersonic cruise, the engines, operating at full capacity all the time, were sensitive to any perturbation and reacted violently with engine surge: the engine refusing the incoming air.
Stopping suddenly a flow of almost 200kg of air per second traveling at 600m/sec causes a few problems. As a result, a spill door was installed under the air intake and automatically opened in such event.
To control the system of shockwaves and obtain an efficiency of 0,96 in compression in the air intake, 2 articulated ramps, controlled by hydraulic jacks, are installed on the top of the air intakes in front of the engines. Each ramp is roughly the size of a big dining room table, and the 2 ramps, mechanically synchronized, move up or down following the instruction of an highly sophisticated computer that adapts the ramp position according to the mach number, the engine rating and other parameters such as skidding.
At that time, it was the less known part of the aircraft, almost only designed through calculation since no simulator, no wind tunnel, did allow a full scale test of the system.
The control of the system was analog and very complex but it was not easy to tune and we were moving ahead with a lot of caution in our test at mach 2.
On the 26th of January 1971, we were doing a nearly routine flight to measure the effect of a new engine setting supposed to enhance the engine efficiency at mach 2. It was a small increase of the rotation speed of the low pressure turbine increasing the air flow and, as a result, the thrust.
The flight test crews now regularly alternate their participation and their position in the cockpit for the pilots.
Today, Gilbert Defer is on the left side, myself on the right side, Michel R\xe9tif is the flight engineer, Claude Durand is the main flight engineer and Jean Conche is the engine flight engineer. With them is an official representative of the flight test centre, Hubert Guyonnet, seated in the cockpit's jump seat, he is in charge of radio testing.
We took off from Toulouse, accelerated to supersonic speed over the Atlantic near Arcachon continuing up to the north west of Ireland.
Two reheats, the 1 and the 3, are left on because the air temperature does not allow to maintain mach 2 without them.
Everything goes fine. During the previous flight, the crew experienced some strong turbulence, quite rare in the stratosphere and warned us about this. No problem was found on the aircraft.
We are on our way back to Toulouse off the coast of Ireland. Our program includes subsonic tests and we have to decelerate.
Gilbert is piloting the aircraft. Michel and the engineers notify us that everything is normal and ready for the deceleration and the descent.
We are at FL500 at mach 2 with an IAS of 530 kt, the maximum dynamic pressure in normal use.
On Concorde, the right hand seat is the place offering the less possibility to operate the systems. But here, we get busy by helping the others to follow the program and the checklists and by manipulating the secondary commands such as the landing gear, the droop nose, the radio navigation, comms, and some essential engine settings apart from the thrust leavers such as the reheat switches.
The normal procedure consists in stopping the reheat before lowering the throttle.
Gilbert asks me to do it. After, he will slowly reduce the throttle to avoid temporary heckler. Note that he did advise us during the training on the air intake to avoid to move the thrust leaver in case of engine surge.
As a safety measure, I shut down the reheat one by one, checking that everything goes fine for each one. Thus I switch off the reheat 1 with the light shock marking the thrust reduction. Then the 3\x85
Instantly, we are thrown in a crazy situation.
Deafening noise like a canon firing 300 times a minute next to us. Terrible shake. The cockpit, that looked like a submarine with the metallic and totally opaque visor obviously in the upper position, is shaken at a frequency of 5 oscillation a second and a crazy amplitude of about 4 to 5 G. To the point that we cannot see anymore, our eyes not being able to follow the movements.
Gilbert has a test pilot reaction, we have to get out of the maximum kinetic energy zone as fast as possible and to reduce speed immediately. He then moves the throttle to idle without any useless care.
During that time, I try, we all try to answer the question: what is going on? What is the cause of this and what can we do to stop it?
Suspecting an issue with the engines, I try to read the indicators on the centre control panel through the mist of my disturbed vision and in the middle of a rain of electric indicators falling from the roof. We cannot speak to each other through the intercom.
I vaguely see that the engines 3 and 4 seem to run slower than the 2 others, especially the 4. We have to do something. Gilbert is piloting the plane and is already busy. I have a stupid reaction dictated by the idea that I have to do something to stop that, while I can only reach a few commands that may be linked to the problem.
I first try to increase the thrust on number 4 engine. No effect so I reduce frankly and definitively. I desperately look for something to do from my right hand seat with a terrible feeling of being helpless and useless.
Then everything stops as suddenly as it started. How long did it last, 30 seconds, one minute?
By looking at the flight data records afterward, we saw that it only last\x85 12 seconds!
However, I have the feeling that I had time to think about tons of things, to do a lot of reasoning, assumption and to have searched and searched and searched\x85! It looked like my brain suddenly switched to a fastest mod of thinking. But, above all, it's the feeling of failure, the fact that I was not able to do anything and that I did not understand anything that remains stuck in my mind forever.
To comfort me, I have to say that nobody among the crew did understand anything either and was able to do anything, apart from Gilbert.
The aircraft slows down and the engine 3 that seemed to have shut down restart thanks to the auto ignition system. But the 4 is off indeed.
Michel makes a check of his instruments. He also notes that the engine 4 has shut down but the 4 air intakes work normally, which makes us feel better. After discussing together, we start to think that we probably faced some stratospheric turbulence of very high intensity, our experience in this altitude range being quite limited at that time. But nobody really believes in this explanation. Finally, at subsonic speed, mach 0.9, with all instruments looking normal, we try to restart engine 4 since we still have a long way to go to fly back to Toulouse.
Michel launches the process to restart the engine. It restarts, remains at a medium rotation speed and shuts down after 20 seconds, leaving us puzzled and a bit worried despite the fact that the instrument indicators are normal.
Gilbert then decide to give up and won't try to restart this engine anymore and Claude leaves his engineer station to have a look in a device installed on the prototype to inspect the landing gear and the engines when needed: an hypo-scope, a kind of periscope going out through the floor and not through the roof.
After a few seconds, we can hear him on the intercom:
"Shit! (stuttering) we have lost the intake number 4."
He then describes a wide opening in the air intake, the ramp seems to be missing and he can see some structural damages on the nacelle.
Gilbert reacts rapidly by further reducing the speed to limit even more the dynamic pressure.
But we don't know exactly the extent of the damage. Are the wing and the control surfaces damaged? What about engine 3?
We decide to fly back at a speed of 250 kts at a lower altitude and to divert toward Fairford where our british colleagues and the 002 are based. I inform everybody about the problem on the radio and tell them our intentions. However, I add that if no other problems occur, we will try to reach Toulouse since we still have enough fuel.
Flying off Fairford, since nothing unusual happened, we decide to go on toward Toulouse. All the possible diversion airport on the way have been informed by the flight test centre who follows us on their radar.
At low speed, knowing what happened to us and having nothing else to do but to wait for us, time passes slowly, very slowly and we don't talk much, each one of us thinking and trying to understand what happened. However, we keep watching closely after engine 3.
Personally, I remember the funny story of the poor guy who sees his house collapse when he flushes his toilets. I feel in the same situation.
Gilbert makes a precautionary landing since we don't rely much on engine 3 anymore. But everything goes fine.
At the parking, there is a lot of people waiting for us and, as soon as the engines stop, we can see a big rush toward the nacelles of the right hand side engines.
Gilbert and myself are the first to get off the plane and we are welcomed down the stairs by Andr\xe9 Turcat and Jean Franchi who came out from the crowd watching at the right hand side nacelle.
They both behave the same way, with a slow pace attitude, the same look, a mix of disbelief and frustration.
Andr\xe9 is the first to speak: "I can't believe we were not on this flight, really unlucky\x85". Yes, this flight was supposed to be just a routine flight\x85!
The condition of the nacelle is impressive. We come closer and everybody move aside for us with a look of disbelief and respect as if we were hell survivors.
The ramps of the intake 4, those 2 "dining tables", have completely disappeared leaving a hole where we can see the hydraulic jacks and the stub rod where the ramps were attached.
Indeed, only the ramps were missing, apparently ejected forward which was unbelievable knowing how fast we were flying. The ramp slipped under the nacelle causing some damages on it and on the hood of one of the elevon's servo control. Fortunately, the control did not suffer any damage.
What is left of the rear ramp seems to be blocked down inside the intake in front of the engine and we can see behind it the first blades of the compressor, or what is left of it, not much.
The engine swallowed a huge amount of metal but no vital parts of the aircraft has been damaged, no hydraulic leaks, no fuel leaks. I remembered at that time the stories of some B58 Hustler accident where the loss of an engine at mach 2 almost certainly ended with the complete loss of the aircraft. Our Concorde has only been shaken. This incident strengthened the trust I had in this plane. And I was not unhappy to have experienced this ordeal, especially when I saw the frustration on the face of Andr\xe9 Turcat and Jean Franchi.
But we had to understand what happened and how; and also why the ramp's fixing broke.
It didn't take much time to get the answers.
I unintentionally triggered the problem when shutting down the reheat of engine 3. The sudden stop of the fuel flow did of course stop the combustion and the back pressure behind the low pressure turbine. But, probably because of the modification made on the engine before the flight, the stop of the reheat has not been followed by the normal closing movement of the primary nozzle to compensate the pressure drop. So the low pressure turbine ran out of control, dragging down the low pressure compressor which reacts by surging.
Despite the opening of the spill door, the engine surge led to a sudden movement of the shockwaves in the air intake creating a surge in the intake itself. A similar surge happened in the adjacent intake 4 followed by a surge of the corresponding engine. This caused an excessive pressure above the ramps and the fixings of the intake 4 did not hold.
Since it was the first time we experienced a surge in the air intake, we had little knowledge of the stress it would create on the ramps. This led to miscalculation of the strength of the ramps's frames and they did brake.
Another mistake: instead of installing the motion detectors on the ramp itself, to make the production easier, they have been placed on the arms of the hydraulic jacks. This is why Michel R\xe9tif thought that the position of the ramps were correct. The hydraulic jacks did not suffer any damage and were still working normally even if the ramps were missing.
All the data recorded during this event helped us in redesigning the air intakes and the flight test program resumed three month later.
After this, we deliberately created dozen and dozen of air intake surge to fine tune the way to regulate them with digital calculator this time.
From now on, even if it was still very impressive, it was safe and their intensity was not comparable with what we experienced with the missing ramps.
However, a french president may kept a lasting memory of this, much later, during a flight back from Saudi Arabia. This time, I was on the left side, Gilbert on the right and Michel was still in the third seat\x85 But that's another story.
For me, the lasting impression of failing and being helpless during this incident made me wonder what a commercial pilot would have done in this situation. This plane was designed to be handled by standard commercial pilots and not only by the flight test pilots.
At that time, I was interested in taking in charge the management of a training center for the pilots of the future Airbus's clients. This event pushed me that way and I made it clear that I wanted to add the flight training on Concorde in this project. This has been agreed and I did it.
And the Concorde training program now covers the air intake surges and how to deal with them.
Jean PINET
Former test pilot
Member and former president of the Air and Space Academy

I've always seen it mentioned as SNECMA reheat until the other day..

The ORIGINAL design for the reheat was done by SNECMA, but due to them getting into all sorts of trouble with the fuel injection system and flame stabilisation, Rolls-Royce baled them out, and it became a Rolls-Royce/ SNECMA design.
ref heritageconcorde.com

Does anyone have any details on the 'joint' development alluded to above?

Thanks.

Attended a Powerplant Design Group reunion earlier, so I thought I would try to get an answer from somebody who really knows ....

The problem apparently was that flame stabilisation operating in "contingency" rating was sensitive to the point that every engine had to be checked, so there was a lot of engine plus reheat testing, most of which was done at Patchway. The solution was addition of some form of 'spike' at various points on the spray bar (my informant wasn't very specific). It sounded like a sort of vortex generator cum chine that gave the flame somewhere to latch onto. The development process was, as you suggested, a joint activity.

PJ2 reminds us of the way the airframes of other a/c queuing for take-off would resonate as Concorde departed. Whether it was the responsibility of SNECMA or Rolls Royce (or even Bristol Siddeley? ), the reheat was certain to set off a random sprinkling of car alarms on the airfield, which used to make my day when lucky enough to be returning to the car park around midday at LHR.

Even without reheat, however, the engine had a distinctly military sound - quite unlike other civil turbojets I can remember. The sound of it in the descent at about 4000ft over my house at 5 pm daily was unmistakeable. On the approach, if you weren't expecting it, it could be quite unnerving. One night in the late 1970s, during a long car journey, I stopped for a call of nature at a well-known public house near Hatton Cross (about a mile from touchdown on LHR 27L). It was pitch dark, and I decided that the hedge at the side of the car park would be a suitable venue. Never having heard Concorde on the approach before, I became increasingly nervous as the sound, initially unidentified, got progressively louder. And then the landing lights were switched on...

Many years ago, I'd flown into Heathrow (after a horrible flight - a 6+ hour delay after pushback at JFK due to weather). I was in line to pick up my rental car when suddenly there was this horrendous noise - a "can't hear yourself think" noise. The strange part was no one else even seemed to notice . I turned and looked outside, and there was a Concord on it's takeoff run in full afterburner . It was the only time I was able to see a Concord moving under it's own power .

No idea what tail number it is, but there is a Concord at the Seattle Museum of Flight. First time I walked inside I was stunned at how small it was. The windows are tiny, and the seats would not appear out-of-place in economy on todays international flights. The cockpit is blocked off with clear Plexiglas, but looked decidedly primitive by todays (or even 1980's) standards. No doubt the cabin service was top notch, and there is definitely a luxury in making a six hour flight in two hours. But it's also not hard to understand why it wasn't a commercial success .

But I sure wish I'd had the opportunity to fly on one