ORIGINAL: Sport_Pilot
What is a blown elevator? Did you mean foam. Or were you refering to our aircraft elevators. That is a differant situation as the control force is not just the total lift but also the vector of the airflow that is diverted by the elevator. Lift that is 90 degrees relative to the fuselage does not have to be as large as lift that is 30 degrees.
Hugh,
Blown elevators are those that are in the direct flow path of the prop's wash.
The air thrown back by the prop always hits them chord-wise. So they produce 'up', or 'down' force even when they are at close to an AoA of 90º relative to the actual direction of flight, because their AoA is relative to the prop-wash and not to the actual direction of flight.
The wing on the same aircraft can be at an AoA of 90º and even more, making no lift at all, but the elevator will still be effective under power.
Foam? What foam?