Electromotive Propulsion Concepts for Rotarcraft

The application of electromotive propulsion to rotorcraft provides several opportunities for the improvement of the helicopter's operational efficiency. The propulsion of rotors via tip thrusters has long been envisioned, since they provide the opportunity for higher G.W. helicopters, higher payload/G.W. ratios, and reduction in power and fuel requirements. Utilizing the electromotive drive to provide rotor blade propulsive thrust, as well as chordwise and blade coning balance, allows an overall reduction in weight empty, thus increasing the payload/lift capacity. This technology can be applied to rotorcraft gross weights from 10,000 to 350,000 lbs. The weight and complication of a mechanical drive are reduced with tip propulsion. Tip propulsion also eliminates the anti-torque side force required in a shaft-driven helicopter. Another advantage is the saving of the rotor blade balance weight (required for chordwise balance) by using the weight of the blade thruster and the drive system weight as the balance weight. This is particularly valuable in large diameter slow-turning rotors that require additional balance weight to keep the rotor coning angle within a practical angular limit. Improved lift performance, reduced maintenance, increased safety and reduced operational cost are potential attributes of the electromotive rotor tip propulsion system.