AIRCRAFT of the type known under the Registered Trade Mark “Autogiio,” 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 diagrammatically 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, etc., 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 deg. 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 f1, 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 p2 and is disposed below the point f1 and forward of the axis of rotation 0, 0. In the limiting case where the hinges a, a are coaxial p2 may pass through the point of intersection of the hinges with the axis 0–0. Fig. 5 shows how the longitudinal pivot axis p5 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 re‐treating blade. The transverse pivot p2 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 deg. 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 42 on which is rotatably mounted an intermediate member incorporating an offset backward projection 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 shot 71x 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 over‐running 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 conveniently 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 turnbuckles 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 56x.
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