> I wonder if you could use your propeller as a "wind turbine" when landing to recapture some energy? Helicopters do this, it's called autorotation. They spin

> I wonder if you could use your propeller as a "wind turbine" when landing to recapture some energy? Helicopters do this, it's called autorotation. They spin up the rotor while descending and then trade the rotational momentum for a little bit of lift to make a safe landing. It's a tricky maneuver but a part of every heli pilot's training. I doubt that it's a viable strategy for light aircraft, though. The loss of airspeed from extracting energy out of the wind stream is more dangerous than gliding. Thermals aren't powerful enough to keep a non-glider aircraft in flight as far as I know. Large aircraft use a small windmill or a ram air turbine to keep hydraulics and electrics up in case of a loss of power, though.