What is a sprag clutch assembly primarily used for?

The sprag clutch assembly is primarily designed to prevent engine over-speed during the starting phase of an engine, which is particularly crucial for maintaining operational safety. This device allows the engine to start without the driving components rotating faster than intended. In situations where the rotor is driven by an external power source, the sprag clutch engages and allows the engine to start up smoothly. Once the engine reaches a certain speed, the clutch disengages, which prevents excessive rotational speeds that could lead to engine damage.

Understanding the role of the sprag clutch is vital because it ensures that the engine operates within its specified limits during the critical starting and acceleration phases, thereby enhancing the overall reliability and safety of the aircraft system.