Originally Posted by
Joao.m
Where can I find info (FCOM was no help) regarding when the FADEC is actually powered off. is it as soon as the masterswich is set to off or only when the engine goes bellow a certain N1/n2?
Thanks in advance
Talking Boeing here, but I'd be shocked if Airbus was different:
The FADEC is powered by a dedicated Permanent Magnet Alternator (PMA) on the engine gearbox. The PMA will keep the FADEC powered whenever N2 is above 8% (it's usually better than that - 'stay alive' can be as low as 4-5% N2. Aircraft power is also supplied (via the fuel On?OFF switch), but it's 'backup' in case the PMA fails - a 'get home' mode. Dispatch is not allowed without a functional PMA.