/s? A generator or alternator powered directly by the engines is more efficient than towing a wind vane (still indirectly powered by the engines and/or the potential energy of the airplane) every single time.

This discussion has nothing to do with engine out failure modes.

> This discussion has nothing to do with engine out failure modes.

The 787's APU is not intended to run during flight. If it's running, you're in an engines-out scenario.

Huh? It’s a generator. It generates minimum power to keep the flight controls and instruments working. It’s not propulsion.