743,755. Aircraft; variable-pitch propellers. HUNT, W. E. Aug. 24, 1953, No. 23326/53. Classes 4 and 114. An aircraft comprises a wing structure including lift-increasing means normally adapted in the operative position to divert the airstream downwardly, propelling means including at least a pair of counter-rotating propellers, one each side of the longitudinal axis, each propeller including blades connected to a hub for flapping movement, the hub being drivingly connected to a constant speed universal joint and tiltable about a horizontal transverse axis lying in the propeller disc between horizontal and downwardly inclined positions, so disposed that at all times the wing structure and lift increasing means are substantially centred in the propeller slipstream, which flows over the major portion of the wing structure, and comprises an empennage positioned behind the wing structure so as to be at all times within the slipstream. The embodiment of Fig. 1 shows an aeroplane having a cabin 10, empennage 14, wings 11, leading edge slats 19, spoilers 21, flaps 20, and two forwardly exetnding propeller hub mounting beams 12. The engine is housed in a cowling 22 (Fig. 5) slung beneath the fuselage, and drives through bevel gears 24, 25 and a flexible coupling 28 a shaft 29 running through a wing strut 23 and journalled therein by a bearing 30. At its far end, shaft 29 drives a gear box 34 (Fig. 6, not shown) driving a propeller drive shaft 38 (Fig. 8) inside beam 12. Alternatively, as seen in Fig. 10, each propeller may have its own engine 22a mounted in a large beam 12a extending forwardly of the wing. At the forward end of shaft 38 is splined an extension 39 journalled in bearings 41, 42. An inner spherical member 47 is splined thereon, and drives an outer spherical member 49 through balls 50 engaged between flanges 52 on outer member 49 and guided by a cage 53 fast to the outer member 49. A tubular extension 54 of member 49 is journalled by bearings 57 in a socket in a member 55 pivoted on brackets 58 about a horizontal axis passing through the centre of spherical members 47, 49, and rocked by an arm 60 pivoted to the rod 62 of an electric screw jack 63, so that operation of the jack tilts the member 49, but shaft extension 54 continues to rotate at uniform speed. Splined to shaft extension 54 is a blade-supporting member 64 having arms 65 to which blades 67 are attached about flapping axes 66. An arm 74 integral with the blade root is secured to a cylinder 72 filled with oil and containing a piston 77 provided with bleed holes and centering springs 79, 80 to damp flapping and normally centralize the blades. Each blade 67 is also mounted on a cuff 68 journailed by bearings 69 to the yoke member 71 pivoted for flapping movement, and provided with an arm 95 to effect pitch change. A flexible conduit 88 leads from a governor-controlled valve in the wing to a hydraulic cylinder 81 containing a biasing spring 85 and a piston 84 connected by links 91, 93 to arms 95 on the blade cuffs, so that variations in speed control the fluid in cylinder 81 through the governor-controlled valve, and vary the blade pitch to produce constant speed of rotation. Preferably, as shown in Fig. 10, the electric jack 63 operates the leading edge slats 19 and flaps 20 simultaneously with tilting the propeller hub. Slat 19 is mounted on a parallelogram linkage 109, 108, 107, and flap 20 swings on arms 116 about a pivot on bracket 117. The aircraft is said to be capable of very slow and hovering flight, and the propeller hub can be tilted rapidly, the blade flapping action dissipating gyroscopic reactions. Specification 400,735 is referred to.