A320 (CFM) FADEC
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A320 (CFM) FADEC
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
Thanks in advance
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.
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Educated guess (and please feel free to correct me if my guess is all wet) - but I'm thinking Airbus may have a time delay relay in the aircraft power circuit that keeps the FADEC powered from the aircraft for five minutes after the fuel shutoff command. We did something like that on the 747-8 so that the engine monitoring equipment could finish downloading everything after shutdown before everything is depowered (except it's 15 minutes).
Easy way to tell if the FADEC is powered is to look at EGT - if EGT is being displayed, then the FADEC must be powered since there is no backup (rotor speeds often have analog backup)
Only half a speed-brake
After powering up from cold, the whole aircraft is energized for 5 minutes for systems self-test, then many of the features de-power.
FADEC one of them, easily observed on the ECAM E/WD DU with amber crosses instead of the engine instruments after the time outs.
After ENG shut-down, assuming APU or EXT PWR is connected, the FADEC are left powered (EICAS showing what it should) for the same 5 minutes and then the indications go amber crossed again.
FADEC one of them, easily observed on the ECAM E/WD DU with amber crosses instead of the engine instruments after the time outs.
After ENG shut-down, assuming APU or EXT PWR is connected, the FADEC are left powered (EICAS showing what it should) for the same 5 minutes and then the indications go amber crossed again.
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