Not sure if I'm missing some logic here here, but is there a time delay between 3 engine generators going offline (in the air) and the APU door beginning to open for an autostart?
Air India event:
The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec.
As per the EAFR, the Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN at about 08:08:52 UTC. The APU Inlet Door BEGAN opening at about 08:08:54 UTC, consistent with the APU Auto Start logic.
I assume we can ignore the cutoff to run part. Of course there will be spooldown time (unless addtional logic is attached to the fuel cutoff levers?
What is the generator trip speed? 55%N2 like a CF6, or higher? During main engine start, the generator symbols don't appear on EICAS until idle has been reached.
The RAT certainly had no issues deploying much earlier.
Thanks.