U.S. Patent Specifications

In a rotary wing aircraft having a fuselage and two load‐carrying rotors turning in opposite directions and having rotor blades of aerofoil cross section, means for controlling the directional heading of the fuselage comprising spoilers on said rotor blades and movable between an active position in which they increase the drag of the respective rotors on which they are provided and an inactive position in which they do not materially increase said drag, said spoilers being located not less than 30 per cent of the length of the blade from the tip of the blade, and pilot‐controlled operating mechanism for moving said spoilers between active and inactive position, said operating mechanism including a movable pilot‐controlled member and being connected to said spoilers to move said spoilers of one rotor to active position by movement of the pilot‐controlled member in one direction and to move said spoilers of the other rotor to active position by movement of the pilot‐controlled member in the opposite direction.