The 958856 Sprag Clutch is a one-way clutch assembly used in ROTAX aircraft engines, primarily within the starter drive system. It allows torque to be transmitted in one direction while freewheeling in the opposite direction, enabling efficient engine starting and protecting the starter mechanism once the engine is running.

During engine start, the sprag clutch engages to transfer rotational force from the starter motor to the crankshaft. Once the engine exceeds starter speed, the clutch automatically disengages, preventing back-driving and potential damage to the starter components.

Its primary functions include:

Transmitting torque from the starter to the engine during start-up
Preventing reverse torque from damaging the starter system
Ensuring smooth engagement and disengagement within the starting mechanism

Sprag clutches like the 958856 are critical for reliable engine starting performance and longevity of the starter system, especially in high-compression aircraft engines where controlled torque transfer is essential.