Patent GB-662319-A (GB)
Title: Rotary wing aircraft
IPC: B64C27/54
Filed: 1949-11-21
Abstract: 662,319. Helicopters. UNITED HELICOPTERS, Inc. Nov. 21, 1949 [Jan. 24, 1949], No. 29741/49 Class 4. A rotary wing aircraft of the type disclosed in Specification 645,234 includes a lift wing supporting column, a lift wing, a structure for mounting said lift wing on said column for rotation about the axis of the column and for pitch adjustment about a, first axis extending longitudinally of the lift wing and for flapping of the lift wing about a second axis extending transversely with respect to the first axis, a control blade mounted for rotation about the axis of said column and for pitch adjustment about a third axis extending longitudinal]y of said control blade and transversely with respect to the first axis, said third axis being spaced from said second axis along the axis of the column, and means including a pilot operable control member for effecting pitch adjustment of said control blade. The rotor 14, the torque reaction of which is balanced by a tail rotor not shown, is mounted on a vertical drive shaft 17 by means of a banjo type fitting 23 mounted on a gimbal ring 22 for universal freedom of movement. The fitting 23 is provided with upstanding lugs 26 pivotally connected to the ring 22 on an axis 24 which constitutes the axis of simultaneous pitch change of the blades 14. The ring 22 is in turn pivotally mounted on the shaft 17 on an axis 21 about which the connected blades 14 may tilt in a flapping sense. The end fittings 28 of the blades 14 are rotatably mounted in opposed fittings 27 formed on the fitting 23 and are each connected to the hub fitting 23 by a torsion link 58, Fig. 4, which restrains outward movement of the blade under the action of centrifugal forces. Each fitting 27 is vertically slotted to accommodate a collective pitch control arm 46. the outer extremity of which is connected to a link 44 attached to the upper end of a shaft 43 slidable within the rotor shaft 17. The lower end of the shaft 43 is pivoted to an extension 122 of an arm 133 connected by a rod 136 to a pilot's collective pitch control member, not shown. Control blades 16 are rotatably mounted on trunnions 31 secured to the fitting 23 on an axis 29 normal to and coplanar with the longitudinal axis of the rotor blades 14. An arm 42 extends downwardly from the root end fitting of each blade 16 and is connected to the upper element 41 of a scissors linkage, of which the lower element 39 is pivotally connected to the inner member 36 of a swash plate 32 actuated by a pilot's control arm 33. Rotation of the outer element of the swash plate is prevented by a horeshoe fitting 101, Fig. 4, attached thereto at 102 and connected to the apex of a pair of shear legs 104. Movement of the control member 33 effects pitch change of the blades 16 which results in a flapping movement thereof. Such movement causes pitch changing movement of the blades 14 about the axis 24 which in turn causes the rotor blades to flap about the axis 21. Since the pitching axis of the control blades 16 is situated below the flapping axis 21 of the blades 14 and the vertical distance between the swash plate 32 and the universally jointed connection between the levers 41 and 42 is greater than the length of the lever 42, initial movement of the pilot's control arm 33 effects a high initial increase of pitch of the control blades 16 with consequent flapping or tilting motion which will result in an increase of pitch of the rotor blades 14 and consequent flapping movement. Since the pivots 21 and 29 are spaced vertically such flapping will result in an automatic decrease of the pitch of the control blades 16 so that a condition of equilibrium is reached between the controlling and lifting rotors.