Patent GB-393976-A (GB)
Title: Improvements in and relating to aircraft having freely rotative wings
IPC: B64C27/02
Filed: 1931-12-16
Abstract: 393,976. Aircraft with rotary wing systems. LA CIERVA, J. DE, Bush House, Aldwych, London. Dec. 16, 1931, Nos. 34867/31 and 21551/32. [Class 4.] Aircraft of the type known under the Registered Trade Mark " Autogiro " have means for controllably tilting the rotor axis in relation to the body in one or more substantially vertical planes about real or virtual pivot axes, any such pivot axis being located above the centre of gravity of the aircraft, below the point of intersection of the rotor axis with the projection of the line of resultant aerodynamic action of the rotor on a plane containing both the rotor axis and the shortest distance between the rotor axis and the pivot axis, and offset from the rotor axis in the direction of the aerodynamic reaction line. Figs. 2 and 5 show diagramatically an aircraft having a body b, a rotor comprising blades r, r connected by horizontal hinges a, a, to a rotor hub having an axis of rotation 0, 0. Lines 0-0, 1-1, 2-2, &c. represent the projections on the plane of the paper of the aerodynamic reaction lines corresponding to successively reduced angles of incidence of the rotor, line 0-0 representing the reaction line for an angle of incidence of 90‹ corresponding to vertical descent, line 5-5 representing that corresponding to a small angle of incidence corresponding to maximum flight speed. These projection lines intersect at a focal point f<1> the height of which above the hinges a, a depends upon the degree of separation thereof, this height being zero when the hinges a, a are coaxial and intersect the axis of rotation. The transverse axis about which the rotor may be tilted is shown at p<2> and is disposed below the point f<1> and forward of the axis of rotation 0, 0. In the limiting case where the hinges a, a are coaxial p<2> may pass through the point of intersection of the hinges with the axis 0-0. Fig. 5 shows how the longitudinal pivot axis p<5> for lateral tilting of the rotor is displaced from the axis of rotation 0-0 in the direction of the aerodynamic reaction line, i.e. in the direction of the retreating blade. The transverse pivot p<2> for longitudinal rotor tilting is located rearwardly of the centre of gravity, the perpendicular from the centre of gravity on the pivot making an angle of the order of 6‹ with the perpendicular to the longitudinal body axis. Means may also be provided for bodily displacing the rotor longitudinally of the aircraft whereby the attitude of the body to the line of flight may be controlled, in the plane of symmetry, independently of the flying speed and of the position of the centre of gravity. In one embodiment, Fig. 6, a pyramid of struts 36 supports a rotor comprising blades 38 secured to a hub 37 by horizontal pivots 39, links 40, and vertical pivots 41. Hub 37 is mounted on an axis member 78, Figs. 9 and 10, pivotally mounted on pyramid 36 by means of a transverse pivot 42 and a longitudinal pivot 43, Fig. 8. Pyramid struts 36 are bolted to an apex member 71 incorporating a fork 72, Fig. 10, carrying transverse pivot pin 42 on which is rotatably mounted an intermediate member 74 incorporating an offset backward projection 75 constituting the longitudinal pivot 43 and a downward projection 76 which serves to limit rocking of member 74 about the pivot 42 by co-operation with the sides of a slot 71<x> formed in apex member 71. Rocking movement of axis member 78 in pivot 43 is limited by integral lugs 80 which embrace the projection 76. Movements of part 74 about pivot 42 and of axis member 78 about pivot 43 are damped by spring-loaded friction discs 148, 153 respectively, the pressure on which may be varied by adjusting their respective nuts 151, 156. As shown in Fig. 9, an internal expanding rotor brake and rotor starting gear are associated with the axis member 78, the latter gear including a dog clutch permitting overrunning of the rotor with respect to the drive shaft. Means for controlling the rotor tilting movements comprise levers 48, 52 respectively associated with the intermediate member 74 and the axis member 78. Lever 48 is coupled to a bell crank 46, Fig. 6, by a rod 47 and lever 52 is coupled to a lever 50, Fig. 8, on a longitudinal rock shaft 49 by rod 51, bell crank 46 and rock shaft 49 being operated by a conventionally arranged control column 44. Rods 47, 51 are tubular and are connected to their respective levers 48, 52 by resilient connections comprising columns of rubber rings 106, Fig. 9, which bear against abutments 107 fixed in the bore of the rod and against a collar 108 formed on a slidable rod 109 which is connected to the operating lever by a forked shackle 110, in the case of rod 47, and by a shackle 111 and an eyed swivel 112, Fig. 10, in the case of rod 51. Means are provided for imposing an elastic bias on either control, these comprise in the case of the fore-and-aft control two lengths 116 of shock absorber elastic, Fig. 11, coupled at one end to a lever 115 on shaft 113 of bell crank 46 and at the other by cables 117 to an adjustable lever 119 working in a quadrant 120. Similarly, shock absorbers 123 are coupled to a lever 122 on rock shaft 49 and are connected by cables 124, Fig. 12, passed round pulleys 126 to a lever 127 mounted on a subsidiary rock shaft 128 the angular position of which is controlled by a ratchet lever 129, Fig. 11. Shackles 118 are adjustable for varying the initial stress in elastics 116 and turn buckles 125 are placed in the run of cables 124. In addition to control column 44, a rudder bar 55 is provided operating a rudder 54, Fig. 6, and a steerable tail wheel 64, and a lever 62 for adjusting a tail plane 57. All these controls may be locked in any adjusted position, lever 62 by a ratchet 63 and the remainder by means of friction clamps 141, 142, 143 respectively, Figs. 11 and 12. Clamp 141 locks a slotted lever 140 fast on rock shaft 49 to a fixed fuselage member. Similarly, clamp 135 co-operates with a slotted plate 134 linked by rod 133 to a lever 132 on rock shaft 113. Clamp 143 co-operates with a slotted plate 142 inserted in the run of a rudder cable 56<x>. A lock for holding column 44 in extreme forward position comprises a plate 144 rockably mounted on a transverse pivot and slotted to engage a flange 44a on the column when it is rocked upwardly and rearwardly, as shown. A spring 146 holds plate 144 in either operative or inoperative position. In a modified aircraft rotor tilting control is supplemented by conventional ailerons and elevators. In addition, means are provided for shifting the rotor axis bodily in the longitudinal plane. To effect this fork member 72 is slidably mounted in guides 224, Fig. 16, formed in an apex member 223. Means of adjustment comprise a quick-thread screw 225 traversed axially by a nut 226 having an integral sprocket 227 by which it may be rotated by chain 228, Fig. 17, and cables 231, Fig. 18, from a hand-wheel 235 in the cockpit. Fig. 18 shows the pilot's controls which are generally similar to those of Fig. 11 except that lateral control is by hand-wheel, rock shaft 49 terminating at the rear end in a spigot bearing 219 supporting the front end of a non - rotating shaft 220 carrying the transverse pivot of column 44. The ailerons are mounted on torque tubes 213, the inner ends of which project into the body and carry levers 212 linked to a transverse lever 210 secured to rock shaft 49. The elevators are operated by fore-and-aft movement of column 44 the transmission comprising rigid links 209, 207. In a further modification, Fig. 20, the aircraft has no fixed wings, elevator, or rudder and is controlled by tilting the axis structure of a two-bladed rotor. The body is rendered stable in yaw, pitch, and roll by means of a fin 300, stabilizer 301, and a streamlined fairing 302, respectively, the latter enclosing the rotor mounting structure. The main rotor supporting element consists of a tubular mast 308, Fig. 21, which with the control rods 47, 51 is enclosed in fairing 302. The transverse pivot pin 42 is carried by a fork 312 formed on a socket 311 fixed in the bore of tubular mast 308. Rotatably mounted on pin 42 is an intermediate member 313, a rearward projection of which forms the longitudinal pivot 43. Rocking movement of member .313 is limited by a downward projection 313<x> located between jaws 311<x> formed in socket 311. Mounted on pivot 43 is an axis member 314 carrying bearings 315 for hub member 37. Blades 38 are secured by links 40 to a single pivot pin 39 passing through a single-eyed lug secured to the upper face of the hub member 37. Hub member 37 terminates downwardly in a cone 317 lined with friction material 317<x>, and adapted, when the axis member is tilted to its extreme forward position, to make a driving contact with a friction cone pinion 318 mounted on the upper end of a shaft 303 driven by the engine through a dog clutch controllable by arm 305, Fig. 20. Tubular rod 47 is connected at its upper end to lever 48 carried by pivot 43, and at its lower end to a lever 321 mounted on a transverse rock shaft 322 to which is also secured a pedal lever 323. A lever 325 also fixed on shaft 322 is coupled by a strong spring 328 to a lever 326 freely mounted on shaft 322 and having a stop 327 arranged to bear against lever 325. Lever 326 is coupled by a rod 329 to extension 330 of a control column 331 working in a quadrant 333. Spring 328 is of a strength normally to hold stop 327 against lever 325 and thus to give positive control of longitudinal tilt by column 331 but rapid backward tilting of the rotor, as for landing, may be effected by depressing pedal 324, column 331 remaining locked in quadrant 333. The forward part of quadrant 333 is cut away to enable the rotor to be tilted forward to its greatest extent to engage cone 317 with pinion 318 for starting and to allow a smooth pressure to be applied between these elements by column 331. A lever 340 pivoted about a