US Patent 9677663 Gear geometry with fluid reservoir and fluid paths

A helicopter is provided and includes an engine, a rotor, a gear train configured to transmit torque from the engine to the rotor such that the rotor is rotatable about an axis of rotation, a primary lubrication system, which is configured to supply the gear train with a fluid and a secondary lubrication system disposed in a gear of the gear train, including a fluid reservoir, which is configured to receive and store the fluid and to continue to supply the gear train with the fluid following a failure of the primary lubrication system.