> Why would the Ran Air Turbine be time restricted?

Gravity?

But the turbine generates power to keep the plane flying. Why would it only work for 10 minutes? Certainly the flight time is a product of fuel level and altitude. Even if both engines fail the flight time would be a function of altitude. I don’t see how deployment of the RAT informs flight time.

It does not generate power to provide thrust; it generates power - using the airstream as the aircraft moves through the air - for the avionics and/or hydraulics.

Yes, exactly.

By definition, when you are using the RAT, you don't have any electrical power and you probably don't have thrust.

You are constrained by battery, airspeed, and altitude.

If the RAT could keep the plane flying indefinitely we would just be using RAT instead of fuel I suppose.

/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.

The RAT is a generator, not a device that can provide thrust. If anything it will minutely slow the plane down.