Automatic feathering to reduce the hazard of aircraft engine failure at take-off

FAILURE OF AN aircraft engine in flight changes the propeller of that engine from a source of thrust to a parasitic source of drag. Present-day propellers, selected for the efficiency with which they convert tremendous horsepower into thrust with comparatively small blade area, absorb proportionately high horsepower when wind-milling the engine. The propeller used on the Martin model 202 airplane converts a maximum of 2,400 horsepower into thrust at take-off. The same engine and propeller combination exerts a drag equivalent to approximately 220 horsepower when being windmilled at take-off air speed. In contrast, the drag of the feathered propeller is equivalent to 12 horsepower. Thus, it is evident that in the event of an engine failure, in addition to the immediate loss of half the thrust, a windmilling propeller steals approximately 10 per cent of the horsepower available from the remaining engine, reducing the net thrust to approximately 45 per cent of normal. With one propeller producing drag and the other producing thrust, a turning moment exists, tending to turn the airplane in the direction of the faulty engine.