Abstract: A tunable vibration absorber in a helicopter rotor hub arrangement with a central mass suspended in a symmetrical outer casing over the rotor hub, including an air spring for variably stiffly supporting said central mass in three dimensions.

Abstract: X-wing aircraft employ a rigid rotor-wing utilizing symmetrical circulation irfoils. The rotor is driven mechanically, and lift is achieved by modulation of air circulation about the base airfoils. This is accomplished by blowing compressed air through trailing edge openings in the rotor blades, and controlling the amount of air being ejected through those openings. By cyclically modulating the amount of ejected airflow, cyclic lift control is obtained. Likewise, by collectively controlling the ejected airflow collective lift control is obtained. One reason for the lack of popularity of circulation control rotor systems is concern over a loss or air pressure resulting from a damaged rotor blade. The damage to a rotor blade, such as ballistic damage, can cause the entire plenum pressure to be vented through that damaged blade. The result is a loss of pneumatic control, not only of that blade, but control of all rotor blades.

Abstract: A four axis force stick provides signals indicative of force applied to the stick in an axis corresponding to a control axis of an aircraft, including pitch, roll, yaw and lift/speed. The force-related signals are applied through proportional and integral gain signal paths to operate electrohydraulic servos that control the aerodynamic surfaces of the aircraft, such as the cyclic and collective blade pitch of the main rotor and the tail rotor blade pitch of a helicopter, or the ailerons, rudder, elevator and thrust of a fixed wing aircraft. Signal conditioning provides a dead band to avoid integrating minute, inadvertent force stick signal outputs, and vernier sensitivity at low forces with high gain at high forces. Analog and digital embodiments are discussed. The relationship between this wholly new mode of aircraft control and ancillary aircraft functions, such as ground steering, autopilot and stability functions, are also discussed.