Advanced Overrunning Clutch Technology

This paper summarizes the results of a 3 year research program to advance the state-of-the-art in helicopter free-wheel units (overrunning clutches) by permitting operation at 20,000 rpm. By designing the free-wheel unit to operate at engine input speed instead of at the speed of the 2nd reduction where it is usually located, the torque, and hence size and weight of the unit, will be reduced. High-speed designs, test results, and application of the designs to the UH-60A BLACK HAWK are presented for spring, sprag, and ramp roller types of overrunning clutches.