Abstract: Yaw control device for helicopters with contra-rotating rotors which controls the anti-torque action of the rotors on the helicopter fuselage by means of a variable speed reduction ratio drive transmission comprising a differential traction drive. At one setting of the yaw controls the rotor torques are balanced by means of the differential in which the input shaft drives a planet carrier and the output shafts are driven by traction discs.The yaw control is accomplished by means of tilting the axes of rotation of the planets thus changing the effective radia of driving the discs which upsets the rotor torques equilibrium. In a stabilized flight of the helicopter the rotations of the planets on their carrier is practically nil, hence the power loss due to the use of the traction drive is small.

Abstract: A VTOL launching and retrieval system comprising a single stud type primary landing gear and a mechanical arm equipped with a clamping device arranged to take hold of the VTOL while it is held in upright position using its own flight control system and it is either fully airborne or to some extent supported on its stud. The system allows an orderly transfer of the VTOL motion control from that by means of its flight controls to that by means of the mechanical arm which may be of flexible type, allowing to move the VTOL to stabilize in space its grasping digits or to move the VTOL from the landing site to a hangar.