Originally Posted by
philbky
UNCTUOUS's theory is interesting but I just wonder had the cockpit been severely damaged by an O2 fire, just how stable the aircraft and its control systems would have been.
Certainly any hole in the side of the aircraft would not have initially or later disabled its ability to stay aloft but the control surfaces are fly by wire so the questions have to be asked, in the light of the destruction to the Egyptair example, could the controls remain in a detente position exactly as they were at the time the cockpit end of the system burnt through? How would they cope with turbulence changing any of the axes of the aircraft? If there was time to handle the aircraft to turn it round, why did not the crew call Mayday a la Swissair 111?
How could anyone regain the cockpit and perform any useful function if the damage was as extensive as the Egyptair example and for that matter to the Swissair 111?
Had Swissair 111 suffered its fate an hour or two later we would likely still be looking for it given the hypothesis set out above as it would have been in mid Atlantic with, on the night, not the best HF comms, though the VHF guard frequency might have been used.
My money always has been and still is on a hypoxia situation but, like everyone else, I'm currently lost for a cause that ticks all the boxes.
Despite the severe fire in the cockpit roof of the Swissair- severe enough for molten metal to rain down on the fliightcrew, they were in contact with ATC until they lost control of the aircraft.
In
Unctuous scenario the crew shut down the electric buses and then exit the cockpit. Miraculously, not shutting down the FMC/FMS and not shutting down the SATCOM allowing the aircraft to fly for 7 hours apparently on either track or heading hold. Note that upthread (a long way)there was a discussion of the Egypt Air cockpit fire and it it was doubted if the same result would have happened in the air, and, that there had been a Boeing issued requirement for all 777 to have the cabling and ties checked to ensure that there was no chafing of the oxygen supply tubing to the first officer's seat.