Concorde question

[ChristiaanJ]

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

CJ

[Lance Landing]

Long time lurker, first time poster here.

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

Thank you.

[stilton]

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


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


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




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

[ChristiaanJ]

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

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

CJ

[TURIN]

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

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

Fascinating thread gents, keep it going.

[Cron]

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

Thanks

Cron.

[M2dude]

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

Dude

[bizdev]

Nose Leg Retraction

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

[TURIN]

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

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

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

[twochai]

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

Tupolev 114?

[canuck slf]

Hydraulic failures

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

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

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

Thanks in anticipation.

[M2dude]

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

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

Dude

[Nick Thomas]

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

[galaxy flyer]

Nick

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

GF

[M2dude]

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

Dude

[Totally_Bananas]

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

Any ideas/rumours?

[main_dog]

Eye-to-wheel

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

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

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

MD

[galaxy flyer]

Maindog

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

GF

[ChristiaanJ]

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

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

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

CJ

[Biggles78]

Originally Posted by M2Dude

in 14 feet of engine intake you lost in the order of 1,000 mph of airspeed

That answered the question I was going to ask. Thanks for the explanation though.

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