Posts about: "John Cochrane" [Posts: 3 Page: 1 of 1]¶

Galaxy Flyer
We never had a case of lost pressurisation, ever. The cabin windows had dual laminated panes; an inner pressure pane and an outer thermal pane. We had dual systems that kept the cabin at a max diff' of 10.7 PSI, the engine bleeds pushing about 200lb of air per minute into the cabin. This allowed you to fly the cabin at an altitude of around a 6000' maximum only, right up to TOD. If you HAD to fly subsonically, the ideal was Mach 0.95 at FL290. (Subsonically the aircraft had similar range to normal, but took well over twice as long of course). If however you had to shut down an engine, your range deteriorated quite dramatically, and a diversion was usually sought.

It's great that Bellerophon is posting here again; we need a steely eyed Concorde pilot's input here (not just the boffins/nutters and nerds [that's me ]. To touch more on a couple of his valid points;
Fuel burn: The aircraft would naturally require less fuel as she became lighter and as a consequence gently climbed to maintain cruise Mach number, this is what the engine control system was doing all the time, even though the throttles were wide open it was 'tweaking'.. BUT, the decreasing IAS as you climbed, due of course to the reducing density, just like any other aircraft meant that drag was reducing too, so it was a combination of both of these factors, reducing weight and reducing drag.
Flying controls: It was a slightly weird but wonderful arrangement; pilots inputs would move a servo valve in the hydraulic relay jack, the jack would move in response and drive both a resolver AND mechanical linkages. The resolver ourput was sumed with the flying control position resolvers, and the error signal was fed into an autostab' computer, where it was summed with stabilisation demands (primarily axis rate and acceleration). The autostab computer would the directly drive the surface, and the reducing error signal would reduce the demand etc. While all this was going on, the mechanical linkages would slavishly follow, but as long as you were in FBW (what we used to call 'signalling') mode, these mechanical inputs were de-clutched at the PFCU, so did nothing at all. Only if there was an EXTREMELY unlikely failure of BOTH FBW channels would these inputs be clutched in and the flying control group (rudders, inner elevons or outer and mid' elevons) would then be in Mechanical signalling. The system redundancy was checked after engine start on every flight. But to reinforce what Bellerophon stated, there was no mechanical reversion here; without hydraulics you had nothing. Another aside here; the designers, being paranoid like all good designers (no offence Christiaan ) were worried what would happen if the controls would somehow jam up. A jammed mechanical flying control input run itself would have no effect on FBW operation whatsoever, due to spring boxes being fitted to the runs. A 'Mech Jam' light would be set, together with a separate red light and audio warning, but this was all. But to completely protect against the aircraft was fitted with a Safety Flight Computer (SFC) system. The idea was, if a control axis (pitch or roll only) jammed up, the captain could press down on a switch light set between the two halves of his control wheel, (at the centre of the 'W') and the Emergency Flight Controls would activate. Strain gauges at the front of the control wheel, two sets on each control column for pitch and roll axis, would input into an SFC that would covert the control force into an elevon demand. These commands were then fed into the autostab' computers, and hence directly into the controls. (A little like L-1011 CWS in a way). There was a little test button that was used to test this system, again after engine start. So although the controls were jammed, the aircraft could still be flown. (Never used in anger I'm pleased to report).
But there was a problem; if this system was inadvertantly used, the results could have been catastrophic, as the system was extremely sensitive indeed, and full elevon movement could be enabled with only moderate effort. Because of this hairy prospect some safeguards were obviously put in place. The first safeguard was an interlock in the autostab' engage logic; If the switchlight had been inadvertently selected beforehand (the light was green by the way) you would not be able to engage pitch or roll autostab's (both channels too) so you would not be going flying until that was fixed. The second safeguard was a little more subtle; A plastic, frangible cover was fitted over the switchlight, unless the captain pressed reasonably hard the cover would prevent the switchlight from being pressed. At least that was the theory, in practice this little bit of plastic could be a pain in the ass . It was carefully fashioned, and I seem to remember BAe charging the airlines a few hundred pounds each for these things. If some wally fitted the cover upside down (and unless you were careful it was easy to do) THE THING WOULD NOT BREAK!! I remember at Fairford in 1976, G-BOAD was on pre-delivery flight testing, and the late great test pilot John Cochrane was doing a test of the system. The cover on this occasion HAD been fitted upside down, and of course he could not plunge his thumb through it and engage the EFC button. After trying everything, in the end he removed a shoe, took out his pen, and smashed the plastic cover until it broke. (It's OK, the autopilot was engaged at the time). Unfortunately, his combined shoe/pen emergency device also wrecked the switchlight as well, so the system still could not engage. (There was only a switchlight on the captain's side). After he landed and he confronted us all with his dilemma, he was shaking; not with rage but with laughter. (This was the great John Cochrane, sometimes the dour Scotsman but he was always able to see the lighter side). After that event, careful instructions were issued regarding the fit of the cover, and it was modified and made a little more frangible.

As M2dude says, there were about three separate ways of extending the nose gear, making the event extremely unlikely, and indeed it never happened in service.
It's a halfway interesting "what if" question...
Bearing in mind the c.g. is already almost over the main wheels... could it have been done by moving the c.g. as far back as possible, keeping the droop nose at 0\xb0, and after touchdown keeping the nose off the ground for as long as possible?
The radome would have shattered, but the droop nose structure would have acted like a skid.
Just as well nobody ever needed to try it.

There is only one well-known case of a landing gear problem.

Visualise a moment the main landing gear. The main leg 'l' is held down in the vertical position by a large hydraulic "stay" '\' .
___
\l

(I know that, to most people, it looks at first like the retraction cylinder, but it isn't. The retraction cylinder is much shorter, and inside the wheel bay.)

Now the story... It happened during what was going to be the last-but-one flight of the British prototype, 002, during a demonstration flight at Weston-super-Mare.
After a slow pass with the gear down, the co-pilot flying the aircraft put it into a steep turn, retracting the gear at the same time.

The next moment, there was a very loud bang, and one of the main gear lights did not go "green".

Somebody from the crew went to the back cabin, where there is a small porthole to look into the wheel well. When asked what he could see, the answer was "nothing..." ; both the main stay and the retraction cylinder had parted company with the aircraft, and the gear leg was dangling free.

The pilot, John Cochrane, took over the controls, and brought the aircraft back to Fairford. With his guardian angel doing overtime, he managed to put down the aircraft and keep it straight during the roll-out, without the gear collapsing.

I didn't see the landing, but I saw 002 in the hangar the next day. By that time a steel bar had been fitted to keep the leg upright, but the damage was still impressive.
Later on, a spare stay was fitted, but 002s flight test career was over. She stayed in storage at Fairford for some time, and was then flown to the Fleet Air Arm Museum in Yeovilton, where she still can be seen to this day.
Wisely, for the few minutes flight, they did not retract the gear....

CJ

Shaft109 ,
Thanks for your link for a start...

But it also lead me to this one ... a true gem.. I hadn't imagined it still existed.

Trubshaw on tests

The cutting of the cake after 002s first flight... many familiar faces, including Andr\xe9 Turcat, and John Cochrane, of course
Brian's comment about the "damn furriner" and Turcat's grin alone makes it a "must-watch"

CJ