Coming from the world of somewhat larger keroseneburning aircraft (those who do have engines), the alternators I've come across have been able to generate their own power for critical engine functions as well as for the electromagnetical coils in the alternator through a permanent magnet generator.
Further, engines are required to be able to suck up their own fuel should the boost pumps go - at least below a certain altitude, IIRC.
I do not have any regulations at hand now nor time to look it up, but does this not apply to GA as well?
Anyone have the applicable certification requirements handy?
Cheers,
Fred - curious