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force will cause an over speed. Because of the centrifugal twisting moment, propellers such as
the 54H60 require hydraulic pressure to maintain the propeller blade angle. If hydraulic pressure
is lost, the propeller will go to fine pitch. If the engine is not operating, the result is very high
wind milling drag:
Centrifugal Turning Moment
The C-130 T-56A engine and propeller make up a single shaft turboprop, meaning the engine
and propeller are mechanically connected. During some flight conditions, especially at high
airspeed and low power, during engine control transients, or following engine flameout, the air
loads on the propeller cause it to wind mill, providing more torque than is being supplied to the
propeller by the engine. The wind milling propeller will drive the engine and all the accessories,
resulting in negative torque. Large negative torques causes high drag, resulting in controllability
and performance problems and potential engine over-speeds.