US Patent 9446842 Hybrid power rotary wing aircraft

A rotary wing aircraft includes a main rotor; an electric motor for rotating the main rotor; an electric generator for supplying electric power to the electric motor; an engine for driving the generator; and battery storage for providing battery power. The aircraft further includes a flight control system for controlling the engine to run at idle and causing the electric motor to receive the battery power to rotate the main rotor during takeoff; for controlling the engine to increase speed above idle and operate the generator to recharge the battery storage during flight; and for controlling the engine to return to idle and controlling the electric motor to receive the battery power for landing.