600,374. Aircraft; variable-pitch propellers. LEONARD, L. H. Oct. 1, 1945, No. 25455. Convention date, Jan. 25, 1941. [Classes 4 and 114] An aircraft which can take off in a vertical attitude and then travel horizontally is provided with a variable pitch propeller so positioned with respect to the centre of gravity, and of such blade area in proportion to the area of the sustaining surfaces, that the aerodynamic centre of the aircraft, i.e. the point at which the transverse aerodynamic force intersects the longitudinal axis, during vertical flight with fine pitch is longitudinally forward of the centre of gravity, and during horizontal flight with coarse pitch is behind the centre of gravity. As shown in Figs. 1, 2 and 5 contra-rotating propellers 7, 8, are mounted in the rear of the pilot's cockpit 1, between front and rear supporting and control surfaces 13 and 14, and 12 respectively. The tail portion of the fuselage is divided into four pivoted segments 5 which open outwardly to form an undercarriage for supporting the machine in a vertical position upon alighting and when taking off. The segments 5 are expanded as shown in Fig. 5 by links 19, 24, when a bumper 23 carried by the piston rod 22 of a pneumatic shock-absorber 20 comes into contact with the ground. Additional shock absorbers 27 are fitted between the members 5 and the fixed portion of the tail structure. The propellers are driven by four engines 11, each mounted between a non-rotary axial member 10, Figs. 2 and 8, and portions 2, 3 of the fuselage forming the propeller hubs. The engines revolve bodily with the front hub 2 the rear hub being rotated by the reactive torque. A free-wheeling unit 43 and a two-speed gear are provided, the drive being taken through a large pinion 44 or a small one 45 according to the axial position of a clutch 57 operated through arms 64 by an axially-movable control rod 69 actuated by a hydraulic motor 133. Simultaneous blade pitch variation is also effected by axial movement of the rod 69 through universally mounted members 109, 109a, and links 116, 116a connected to crank arms at the ends of the blade shanks. Cyclical pitch variation for steering and control purposes is effected by tilting the universally mounted members 109, 109a, through links 118, 118a, operated by a hydraulic motor 125. Dampers 98c are fitted to permit yielding of the blades due to torque variations. The arrangement enables the change-speed gear to be set for high engine speed when the propeller blades are at low pitch, as required at take off. Engine cooling air enters through an annular opening 39 at the front of the hub portion 2, and leaves through an opening 38 at the rear thereof, an ejector effect being obtained by the flow of the exhaust gases through a narrow slot at the rear of an annular exhaust space 37. The flow of air is augmented by a fan 79 driven through gearing 82, The Specification as open to inspection under Sect. 91 describes a modification, Figs. 12 and 15 (Cancelled), in which the propellers are mounted at the front of the fuselage, and the undercarriage comprises pivoted telescopic shock-absorbing struts 139. In this case the aircraft is provided with the normal arrangement of front and rear supporting and control surfaces. This subject-matter does not appear in the Specification as accepted.