Patent GB-885652-A (GB)
Title: Improvements in or relating to a convertible aircraft
IPC: B64C29/00
Filed: 1958-11-17
Abstract: 885,652. Convertible aircraft; variable pitch propellers. YOUNG, A. M. Nov. 17. 1958 [Nov. 27, 1957], No. 36902/58. Classes 4 and 114. An aircraft capable of flight as a helicopter or aeroplane comprises a wing structure freely pivoted to a fuselage about a transverse axis lying along the centres of pressure of the wing sections, an engine for driving the aircraft as a helicopter or as an aeroplane, a rotor drivable by the engine during helicopter flight, control means to pivot the wing structure about its axis and means for positioning all leading edges of the rotor head on into the wind when the aircraft is operating as an aeroplane. In Fig. 2, wings 14a, 146, have spars 21a, 21b freely rotatable in bearings (not shown) on the fuselage 11. Each wing supports a nacelle such as 15a, containing an engine and supporting a variable pitch airscrew 17a and a rotor 18a. The pitch change and engine drive mechanisms of nacelle 15a are shown in Figs. 3 and 4, similar apparatus being associated with the other nacelle on wing 14b. The engine drive shaft 23a is connected to the sun gear 43a of an epicyclic transmission, the planet gears 41a of which are connected to a brake drum 44a cooperating with a band brake 45a, and to a carrier 40a on a shaft 35a connected to the airscrew hub 54a. The ring gear of the epicyclic transmission is formed on brake drum 38a cooperating with a band brake 39a and connected through a one way drive mechanism 37a to the sun gear 32a of a further epicyclic transmission, the ring gear 31a of which is fixed and the planet gears 30a of which are mounted on a carrier 29a secured to shaft 27a connected to the rotor hub 48a. A shaft S is connected at the end shown through bevel gears Ga, G<SP>1</SP>a, to sun gear 32a and at its other end is connected to similar apparatus in the other nacelle, so that should either engine fail, the remaining engine can drive both rotors. Normally however, shaft S serves only to synchronize the two engines. By tightening brake 45a and loosening brake 39a power is transmitted from shaft 23a to shaft 27a and the rotor hub only. By reversing the two brakes, power is transmitted to shaft 35a and the airscrew. hub only. The shafts are spaced and supported by ball races 34a, 28a and 36a. The airscrew blades 52a are connected by pitch change pivots 53a to hub 54a, and the rotor blades 51a are connected by pitch change pivots 77a to a gimbal ring 46a pivoted on stub shafts 47a to hub 48a. Collective pitch change of the airscrew and rotor is simultaneously affected by a longitudinally movable rod 72a, Figs. 2 and 3, within spar 21a, pivoted at 71a to one arm 70a of a bell crank lever pivoted to the nacelle structure at 68a, and having a forked arm 67a pivoted at 66a to the outer ring 65a of a ball race, the inner ring of which is attached to an outer shaft 62a apertured at 62<SP>1</SP>a to accommodate the rotor hub 48a and permit shaft 62a to move longitudinally. Shaft 62a thus rotates with the rotor 18a Shaft 62a is connected to the inner ring 60a of a ball race, the outer ring 59a having links 57a ball jointed to it. Each link 57a is also ball jointed to a pitch change horn 55a on one airscrew blade. Longitudinal movement of rod 72a thus results in longitudinal movement of shaft 62a and thus in pitch change of the airscrew. For cyclic pitch change of the rotor, a rotatable shaft 89a within spar 21a and surrounding rod 72a is connected by a crank arm 88a and link 87a to a horn 86a on the inner race of a swash plate 82a mounted by a spherical joint to a stub mast 26a secured to the nacelle structure. The outer race is connected by links 79a, 80a, to a pair of links 74a, 75a pivoted to a collar 73a on shaft 62a. Links 76a, 78a, extend between links 74a 75a, and pitch change horns 77a on the rotor blades 51a. Longitudinal movement of shaft 62a and collar 73a thus moves both links 76a, 78a equally, for collective pitch change of the rotor. Rotation of shaft 89a tilts the swash plate 82a, and thus moves links 76a, 78a, oppositely for cyclic pitch change. Fig. 12 shows the pilot's controls. The shaft 89a and the corresponding shaft 89b from the other nacelle are connected by drives 111a, 111b to a shaft 109 connected by drive 107, pulleys 105, 106 and drive 103, to a hand wheel 100 on a control column 101. Rotation of the hand wheel thus controls the cyclic pitch of the two rotors equally. The longitudinally movable rod 72a, and the corresponding rod 72b from the other nacelle are connected by pin and slot couplings to bell crank levers 120a, 120b pivoted at 121a and 121b to a sliding member 119a and also both pivoted to a rod 124 connected by linkage 126, 129 and 131 to a shaft 132 connected to a lever 133, which thus controls the collective pitches of the rotors and airscrews equally. The sliding member 119a is connected by a drive 114a, 114b to a crank 113 on a shaft 102 connected to the control column 101. Movement of the column about shaft 102 thus moves member 119a laterally together with the bell crank levers 120a, 120b and thus effects differential control of the collective pitches of the rotors and airscrews. For take off as a helicopter, brakes 45a and 45b (not shown) are applied and brakes 39a and 39b (not shown) loosened, Fig. 4. The wings 14a and 14b are set with their chord vertical, which may be done by adjusting the cyclic pitch of the rotors, or by the use of ailerons 14<SP>1</SP>a and 14<SP>1</SP>b, Fig. 2, used as servo tabs in the rotor slip stream. To convert to aeroplane flight, brakes 45a and 45b are loosened, so that power is transmitted to the airscrews. By cyclic pitch control, or by using the ailerons 14<SP>1</SP>a, 14<SP>1</SP>b as servo tabs, the wings are tilted towards a horizontal chord position. The common collective pitch control lever 133 is moved to an extreme position, in which the airscrew blades are set to a working pitch of 45 degrees, and the rotor blades are set to a pitch just over 90 degrees. With the aircraft in forward flight and the rotor shaft now horizontal, this results in an aerodynamic torque on the rotor, slowing it down. Pins 92a, Fig. 4, on shaft 62a contact an annular cam 93a fixed to the nacelle structure, whereby as the rotor blades pass the horizontal position shown in Fig. 2, their pitch is reversed to be that side of 90 degree pitch which tends to return the blades. to the horizontal. Ultimately, the blades come to rest in the horizontal position, where they are locked by engagement of a pin 94a in a notch 95a on shaft 62a. Brake 39a is also applied. Thus power is supplied to the airscrews only. In this position, the rotor blades can act as lift controlling flaps, by operation of the cyclic pitch control. The conventional tail unit can thus be dispensed with, or provided solely for stability. A conventional rudder is used. To facilitate pivoting of the wings, the axis of rotation passes through the centre of pressure of the combined wings, nacelles, rotors and airscrews and also close to their combined centre of gravity. In the example given, the airscrews have one third of the diameter and three times the rotational speed of the rotors. In another embodiment, the engines may be turbo-jet engines which can each be clutched to drive a three bladed rotor for helicopter flight, supplementing the lift by direct jet reaction from the downwardly directed jet, or used normally for forward flight when the wings have their chords horizontal. The airscrews are thus dispensed with.