Captain John Eames (retired)
Senior Flight Engineer Roger Bricknell (retired)
On Tuesday evening 8th March 2011, at Royal Aeronautical Society London there was an excellent presentation by Cap. John Eames and Senior Flight Engineer Roger Bricknell on 'Training Aircrew for Concorde'. There were some real insights from those two experts. Here's what I noted plus some other stuff I added in to make the picture complete.
Concorde consumes 3.5 tons of fuel per circuit when crew training (the only time she flew circuits). Circuit height was 2,500 feet, but most rookie pilots reached at least 3,500 feet in their first attempts before they got the lightweight climb stopped and the aeroplane level. As an aside, one guy told me he used to ‘get it turning early on the climbout - that cooled things down a bit!”
On subsonic aircraft there is there is a rearward movement of the Centre of Lift (I'll use the abbreviation CL here, though it's usually term for co-efficient of lift) of a few inches between minimum and maximum flying speed. On Concorde, it’s about 7.5 feet, occurring mostly around Mach 1 (less so above Mach 1 because the wing twists to compensate for it at the higher speeds). That’s in the transonic regime it requires a similar shift in CG (Centre of Gravity) by moving up to 11.2 tons of fuel aft to tank 11 during acceleration, and back during decel (some of this decel fuel goes straight into the collector tanks rather than the trim tanks, and there is then further trimming from the trim tanks to the collectors and some very careful handling of transfer between the collectors at the end of the flight to prevent CG run-away at high incidence angles).
Subsonic CG is at 55% (of wing chord). Supersonic is 59%. You cannot fly subsonic with a 59% CG – you will lose the aeroplane as the CG is way aft of permissible. The Mach meter shows, for the current CG, the actual Mach speed and the allowable speed range; the CG meter shows, for the current speed, the actual CG and allowable CG range.
The fuel feeds the engines, moves the CG, trims the aeroplane in roll and pitch, cools the wings, cools the engine oil, and cools the air-conditioning for the passengers.
Ozone is present in large quantities at 60,000 feet and is very toxic. But the incoming cabin air from the engine compressors is at 400 degrees C, which renders the ozone harmless so there’s no problem for the pax. (By the way, have you seen those vents on the undercarriage doors? Ozone destroys tyres, so ozone-free cabin air is vented through the undercarriage bays and out to atmosphere to protect the tyres in cruise).
She consumes 40 gallons of fuel per mile at 160 knots, but just 4 gallons per mile at 1,160knots. (She's all about speed!)
Minimum drag is at 320 knots, so she's on the back of drag curve below that and therefore unstable in pitch (She's all about speed!)
1,500 tons of thrust is required to maintain level flight at min drag speed; 2,500 tons is needed at 120kts (She's all about speed!)
Total fuel consumption at take off is 80 tons/hour. At Mach two it’s 18 tons/hour (She's all about speed!)
Fuel transfer for trimming (as well as to move CG for CL shift) is entirely manual. There is a 'do it partially automatically' switch, but the FEs were trained not to use it. The B1 bomber, which BA FEs watched very closely, had an auto-fuel shift CG / CL sync system; the day it failed was the day they lost the aeroplane. So it stayed manual on Concorde.
One degree of difference between the port and starboard elevons, if not corrected by a lateral fuel transfer, will increase fuel consumption by 0.5%.
At 2 degrees incidence, the wing produces no lift (so cross-wind take-offs are a doddle – no need for into-wind elevon). At 3 degrees to 5 degrees the wing produces normal lift. From 5 degrees onwards it’s into vortex lift which, as it propagates backwards at higher angle of attack reaches the elevons and can be felt through the stick as a ‘burble’.
Mach one is achieved at 29,000 feet at 400 knots.
Flight Engineers had be to capable of multi-tasking; systems control was a non-stop task no matter what else was happening (emergencies etc). Roger at one stage had to cope with decel checklists, descent checklists, fuel checklists, and an emergency checklist all concurrently in one incident! Not everyone hacked this in training, and BA allowed failed FEs to go back to their original jobs with no trace on their record of having failed the Concorde course. You either took to it relatively easily… or you just couldn’t keep up with it. There was no in-between.
One incident Roger related shows how the engineers had to understand the aeroplane. They couldn’t get the main undercarriage to lock down (on a training flight) and the emergency checklist said retract the main wheels and land on the nose wheels and engine nacelles! Roger decided not to do this, and the gear remained extended during the subsequent landing, though each main leg was canted in by 7 degrees; any more than 9 degrees and the gear would have collapsed!
One reason Concorde is so complex to operate is that it is two aircraft – a subsonic aeroplane, and a supersonic one!
John mentioned that Autothrottle introduces pitch instability; normally, if the nose drops in cruise the speed builds up, the lift increases, and the nose rises again - a stable situation. With Autothrottle engaged, when the nose drops, the speed rises so the Autothrottle reduces power, and the nose drops even more! So careful pitch control by the pilot, especially during the approach, is vital.
During approach, at 40 feet the Autothrottle is disconnected. At 20 feet ground effect comes into play and the rate of descent reduces and causes a nose-down pitch moment which must be countered by the pilot pulling back slightly to MAINTAIN the pitch attitude at 10.5 degrees (at 14 degrees nose-up the tail wheels would hit the runway!). At 15 feet the power is gently bled off completely and more back pressure applied to hold 11 degrees pitch-up, whereupon she should touch down perfectly and the nosewheel can then be landed (it’s a long way off the ground)!
On take off V1 (go/no go decision speed on the runway) is typically 160knots. After V1, the aeroplane is committed to flight and the FE takes over the throttles from the Captain, who holds the stick neutral (so no lift yet from the wings). At 220 knots, the stick is eased back to the pre-selected pitch attitude on the Attitude Indicator (AI) where it is held – don’t forget it’s unstable in pitch at this speed - (the natural horizon is out of view below the windscreens) and the aeroplane rotates and lifts off.
There were some interesting photos, too, taken by John. He showed the view out of the cockpit at circuit height with the visor down and nose at 5 degrees, then the approach to Brize Norton with the nose at 12.5 degrees (I was lucky enough to see the latter myself back in 1999 on my Concorde jump seat flight), but on approach to Paris CDG!). The pictures showed how effective the droop nose was. He also showed one taken at Oshkosh, with Concorde at low level and banked to about 70 degrees in a very sharp turn; “I had 100 passengers on”, he said. “And only one was sick!”.
Roger confirmed that the aeroplane has been barrel rolled many times, especially during air tests, one of which he was on! Also that BA nearly lost a Concorde on an air test when it inadvertently went out of the back of the flight envelope; they recovered it just before control was lost!
Regarding the ending of Concorde services, it's commonly thought that the sole Concorde accident (at Paris, in 2000), the subsequent 18 months out of service for the post-accident modifications to be completed, followed by the terrorist action at the World Trade Centre in New York just as she came back into service (with consequent drastic reduction in US passenger numbers) were the factors that brought about Concorde's slightly early demise. But her demise was in fact imminent even before the Paris accident, as Airbus had made it known to British Airways and Air France that they wanted to cease support of the aeroplane late in the 1990s.
When 'Paris' happened, there was a desire to see the aeroplane fly again as it would have been negative in the extreme to finish it at that point. So it's entirely possible that the tragedy in Paris actually extended the aeroplane's time in service.