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Concorde question

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Concorde question

Old 3rd Sep 2010, 18:24
  #201 (permalink)  
 
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Biggles,

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

ChristiaanJ

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

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


At touch down the pilots eye height was similar to that of a 747 pilot at touch down. Below 800ft when the aircraft had slowed down to landing speed the pitch attitude was such that the F/E could not see the runway ahead
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Old 3rd Sep 2010, 18:58
  #202 (permalink)  
 
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ChristiaanJ
During landing, Concorde isn't flared at all, it is flown onto the ground at a constant pitch attitude.
During AUTOLAND a flare manoeuvre was instigated by the Pitch Computer at 50' radio, where a fairly simple flare law was invoked. I seem to remember that the law , which used a combination of radio rate (from the RadAlt) and vertical acceleration (from the INS) gave you a commanded height rate of 10'/second at 50', exponentially reducing to 1.7'/second at point of main wheel touch down.
The autoland on Concorde was both extremely accurate and reliable, and an awful lot of guys said they hated using it 'because it can land the aircraft better than I can'; their words NOT mine. (Personally I never bought that one, the guys were just modest as far as I was concerned). This in my opinion is an absolute testament to the AFCS designers; ChristiaanJ and his colleagues at SFENA and GEC Marconi.
To give the complete final approach story; as the aircraft tracked the glideslope in LAND mode, the autopilot G/S deviation, like most aircraft, was geared as an inverse function of radio altitude, and at 75' radio this deviation was flushed down the loo altogether, leaving the A/P to hold radio rate for just a few feet. At 50' the flare was instigated, and at around 35' DECRAB was commanded, where the yaw channel would use a rudder input alone to 'kick off drift' and align the aircraft with the runway centreline. (Concorde did not employ a fwd slip manoeuvre in crosswind conditions, being a slender delta). The 'final' command was at 15' radio, when the autothrottle smartly retarded the throttles. (The Pitch Computer flare law of course continuing to control decent rate all the way down). On touchdown the autopilot would be manually disengaged and the nose gently (usually ) lowered to the ground. (Concorde was only designed and certified as a CAT 3A system, so there was no automatic rollout guidance. However there was a runway guidance symbol on the ADI, which used a combination of Localiser deviation and lateral acceleration, to give you runway rollout track).
Now the flare law was tested every autoland, at G/S capture, and failure of this test resulted in the loss of LAND 3 status on the landing display panel. The most common defect of all with the Concorde autoland was in fact failure of the flare test, when at G/S capture, the previously illuminated LAND 3 indication would drop all of it's own to LAND 2. A simple changeover of autopilot paddle switches would nail the offending Pitch Computer, which would then be replaced before the next trip.

Dude
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Old 3rd Sep 2010, 19:17
  #203 (permalink)  
 
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Bigggles78
Brit312 has certainly answered your query about the Braniff crew issue; I remember being told that one of their captains, a Texan who allegedly wore big cowboy boots while flying, had an ambition at '3,2,1, NOW..' to KICK the throttles open with the sole of his right boot. Never did find out if this ever happened.
The Braniff operation does seem a little crazy now, I must admit. They were supposed to have had long term ideas of serving the Pacific Rim with Concorde, it's a pity that we never got the chance to find out if that could have worked.

Dude
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Old 3rd Sep 2010, 19:48
  #204 (permalink)  
 
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Nick Thomas

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

Correct.

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

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

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

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


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

No.

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

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

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

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


Best Regards

Bellerophon
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Old 3rd Sep 2010, 19:49
  #205 (permalink)  
 
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M2dude,

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

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

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

Needless to say that take off was stopped and we went back to start again at the end of the runway
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Old 3rd Sep 2010, 20:12
  #206 (permalink)  
 
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Awesome thread guys...special thanks to M2dude etal

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

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

I could sit and listen to him all day long.

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

Don't know if any of you "Concorde" folks as well as others have seen it.
If not, take a look at Flight Sim Labs, Ltd.

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

Check it out when you have the time.

Now back to reading....

Best,
David
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Old 3rd Sep 2010, 20:53
  #207 (permalink)  
 
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db737,

I remember Jerry White, who did his Concorde training in Toulouse. He was a great bloke and and a good pilot. If you see him again send him by best wishes from the Brit F/E in Toulouse
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Old 3rd Sep 2010, 20:58
  #208 (permalink)  
 
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Originally Posted by Brit312
If I remember correctly ground effect tended to force the aircraft nose down, so requiring the pilots to pull back on the stick as if they were flaring ,but in fact what they were doing was as you say maintaining the pitch attitude constant.
I'm sure you're right. The thing I wanted to stress was that there was a definite control input needed during the 'flare' to maintain a constant pitch attitude, but I did get the direction wrong....

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

CJ
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Old 3rd Sep 2010, 21:01
  #209 (permalink)  
 
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Hi Brit 312

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

Best,
David
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Old 3rd Sep 2010, 21:17
  #210 (permalink)  
 
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ChristiaanJ


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

In simple terms (i.e. as it was explained to me ) due to the nose up approach attitude, (10˝° PA) the wider trailing edge of the wing entered ground effect before the much narrower leading edge of the wing, meaning more lift was now being generated at the rear of the wing than before, aft of the CG, resulting in a nose down pitch change.

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

The available pitch attitude range on landing was very tight. Depending on the approach speed selected, touchdown attitude typically would be 11° - 11˝°, with a warning call of “Attitude” from the NHP at 12˝° PA. On Concorde, effectively you only got one attempt at making a good landing, after that, with little room to manoeuvre (literally), you had to settle for a safe one, by making sure the wings were level, the rate of descent reasonable, and the pitch attitude within limits and just accepting whatever sort of touchdown she gave you!

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


Best Regards

Bellerophon
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Old 3rd Sep 2010, 21:49
  #211 (permalink)  
 
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Bellerophon,

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

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

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

CJ
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Old 4th Sep 2010, 09:49
  #212 (permalink)  
 
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BRIT312
Now the F/E had a couple of calls to make prior to V1 relating to how good the engines were performing the most important being at 100 kts, however before we got that far the Braniff F/E stood up in his harness and let out the cry " Gee Whiz look at the son of a bitch go".
This story is totally hilarious, can't quite get this visual out of my head. ('100 KTS, POWER SET' sounds so boring in comparison). I never had the good fortune to meet any of the Braniff guys; sounds like there was certainly a character or two there. It really is a pity that their operation never really got a chance to expand into the proposed Pacific Rim service, who knows, it might really have done something.
It's generally known that the BA aircraft were temporarily re-registered to facilitate Braniff's operation out of IAD to DFW; G-BOAA, B, D & E were re-registered from G-BOAA and so on, to G-N94AA etc. Being an older registration, G-BOAC was re-registered as G-N81AC. At IAD, the 'G' part of the registration was covered over, leaving a now perfect 'American' tail number. Only five aircraft were involved in the operation (at the time BA operated just six aircraft, G-BOAF was still at the manufacturers at Filton, and G-BFKW (later to become G-BOAG) was on loan from British Aerospace. In order for the necessary FAA certification, required for operation by a US airline, a modification package were required by the FAA. Some of these modifications seemed a little 'picky' and irrelevant at the time (they still do). However some modifications were certainly not in this category, and quite honestly should have been 'picked up' by the CAA & DGAC during original certification of the aircraft. As an example, if the flying controls had been operating on GREEN or BLUE hydraulics only (due to an indicated spool valve jam) and that particular hydraulic system was subsequently lost, there was originally no automatic switching to select the standby YELLOW system into the flying controls; the controls would have been completely unpowered until a manual selection was made by the pilot. . One of the 'FAA Mods' was to facilitate just that, so if this (extremely unlikely I grant you) scenario had occurred, then YELLOW would automatically been selected into the controls, and at no time would the controls have been in an unpowered state.
The Braniff operation ended in May 1980, due to heavy losses on the subsonic only route, and it's a rather sad irony that aircraft G-BOAF had been modified and reregistered at Filton, from it's original registration of G-BFKX to G-N94AF. Unfortunately the aircraft was delivered to BA in June 1980, one month too late to participate, and prior to delivery it's registration was converted to it's 'normal' British registration; all other aircraft also reverted to original registrations also.
ChristiaanJ
Reading your description of the autoland, you must be quoting from documentation, no?
Not really, being the sad b****d that I am, I still remember the Concorde flare law of: h+5h. = 0, so it was fairly easy to work out the programmed descent rates. (I did have to check the final 1.7'/second figure though). The rest I'm afraid is straight out of this sad old memory of mine.
Bellerophon
A brilliant description of the mechanics of final approach. It's so easy for us mere mortals to forget just what an involved and skilled process it was, to fly, and in particular land our totally amazing aircraft.

Dude

Last edited by M2dude; 4th Sep 2010 at 12:12.
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Old 4th Sep 2010, 10:28
  #213 (permalink)  
 
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British Airways/Air France

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

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

Cheers!
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Old 4th Sep 2010, 23:52
  #214 (permalink)  
 
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Great thread which I am thoroughly enjoying.

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

Would any of the contributors like to expand?
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Old 5th Sep 2010, 01:29
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It was certificated - up to a point. Problematic? Maybe not, but it was a part of the flt envelope to be treated with respect.

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

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

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

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

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

To be honest it was only really used when ATC threw an alt constraint at you during the descent, because in general if you just pitched down to 380kts (Vmo when subsonic at typical approach weights) you would get the height off comfortably.
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Old 5th Sep 2010, 01:37
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Question for engineering types:

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

If anyone has seen the video of AF landing at BZZ after the first post-grounding test flight, you may have noticed that you can hear the buckets translating to reverse even over the noise of the blustery wind and four Olympus 593's at idle.
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Old 5th Sep 2010, 10:56
  #217 (permalink)  
 
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Devil In-Flight Reverse (A case of Bucket and See)

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

Dude

Last edited by M2dude; 5th Sep 2010 at 12:25.
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Old 5th Sep 2010, 11:12
  #218 (permalink)  
 
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telster
How much cooperation was there between the two airlines in terms of training etc? Did any BA crews fly Air France aircraft for any reason for example? Were cockpit proceedures pretty standardised across the two airlines?
One for the pilots really, but there was generally far less co-operation than you'd have thought. I never saw any cases of a BA pilot flying Air France or visa-versa. I know a couple of our guys had ridden jump seat on an AF aircraft, but that's all that I pesonally recall.
On the technical side of things there were meetings between the two airlines, both together and jointly with the airframe and engine manufacturers, but on a day to day basis there was precious little exchange of information, and you'd have thought that we (BA) were the only operator of Concorde, as I'm sure the AF guys felt the same also. In all of my 30+ years on Concorde, I personally went to CDG only once for an exchange of technical views and to help them out with an air intake defect.
I'm so glad that you are enjoying this post, it's great to have you here telster. (It's certainly forcing me to look deep into the dark corners my poor old grey matter).

Dude
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Old 5th Sep 2010, 17:51
  #219 (permalink)  
 
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Hi
I have yet another question! Last year I watched a programme where James May went up in a U2. He explained that at FL700 the plane was flying in "coffin corner" and that the difference in IAS between the stall and the max speed was only 10 knots. I understand that it's due to the very low air pressure at such heights. As Concorde could fly up to FL600 I wondered what this safe airspeed window was during the cruise/climb phase of flight and if this window was framed by the air pressure and/or the CofG position?
Once again thanks to everyone for such great answers and also for the background information.
Regards
Nick
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Old 5th Sep 2010, 20:02
  #220 (permalink)  
 
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Nick,
Again I'll leave the full details to the real experts....

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

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

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

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

CJ
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