Mast Assembly

The mast assembly is installed in the upper main rotor drive compartment and is integral with the transmission assembly. It transmits shaft power from the transmission assembly to the main rotor hub. It also absorbs and reacts to tension, torsion, and bending loads that are the result of the engine torque, helicopter weight, flight motion, and blade rotation.

The mast assembly includes the primary parts that follow:

• Mast pole

• Mast bearing

• Mast seal

The mast assembly is attached to the studs on the top case of the transmission assembly. The mast is tilted 3.5° forward and 0.87° to the left. The swashplate and support assembly is attached to the same studs and holds the mast assembly in position. In the transmission assembly, the planetary assembly drives the mast pole of the mast assembly which then drives the main rotor hub assembly. The transmission oil system supplies the necessary oil flow to lubricate the mast bearing of the mast assembly. The transmission indicating system monitors the quantity of metal particles that result from the wear of the mast bearing. The mast seal prevents contamination of the mast assembly when the mast pole turns.