Originally Posted by
RVDT
Which would be the issue. EEC is supplied with battery/gen power for start. There are diodes on this supply so that the battery/gen can supply power but not the other way around as the PMA should not be able to power the helicopter main bus.
When the throttle is at idle the FADEC would go to MANUAL with no power source and due to the follow up characteristic in the HMU it may go below minimum fuel flow to sustain the engine and it may flameout.
If you have no battery/gen power for EEC to start it then you have a FADEC RESTART FAULT.
Thank you so much for that answer. I’m still trying to understand why the ECU wouldn’t have any power though? The book says that the ECU pulls from the higher voltage of either the PMA or battery/gen. If the PMA goes offline below 85% nP why wouldn’t the ECU automatically default to battery power? Also so I have this correct you said a RESTART FAULT would make the FADEC go into manual?