using the RAT to estimate airspeed.
Interesting theory, unfortunately the RAT's fitted on many large passenger carrying aircraft these days do not power the electrical systems on the aircraft but power an hydraulic pump which is fitted on the back of the RAT strut. The idea being that this pump provides sufficient hydraulic power to enable the aircraft's flying control actuators to keep control of the aircraft. Certainly the case on A320/A330 and B757/B767 aircraft.