GB735571A - Rotor head for rotary wing aircraft - Google Patents

Abstract

735,571. Helicopters. HILLER HELICOPTERS. June 18, 1952 [June 25, 1951], No. 15364/52. Class 4, In a control mechanism for helicopters similar to that described in Specification 662,319 increase of pitch of the blades of a pilot actuated control rotor results in consequent flapping of that rotor and associated pitch change of the blades of a lifting rotor, the two rotors being mounted on a central hub in a common plane, so that when the lifting rotor flaps as a result of such pitch change a feed back linkage between the two rotors decreases the pitch of the control blades which in turn limits excessive flapping movement of the lifting rotor. In Specification 662,319 the feed-back linkage results from an offset between the pitch changing and flapping axes of the two rotors whereas in the present invention the axes lie in a common plane and in consequence each feed back linkage comprises an arm 106 pivotally mounted at its inner end 107 on a hub member 76 in which both lifting rotor blades 2 and control rotor blades 3 are pivotally mounted in a common plane for pitch changing movements. The outer end of arm 106 is connected by a ball joint 111 to the lower end of an arm 112 pivotally mounted at 113 on the shaft 72 of the control blade 3. Intermediate its ends, and preferably at its mid point, the arm 106 is connected by a universal joint 104 to one end of a scissors linkage 97, the other end 99 of which is pivotally mounted on the rotatable element 58 of a swash plate actuated by a pilotcontrolled arm 54. Ultimate flapping motion of blade 2 in the direction of arrow A, Fig. 2, as the result of pitch changing motion imparted to the control blade 3 will cause the joint 107 to move in the direction of arrow B and the joint 111 to move in the direction of arrow C thus causing pitch adjustment of the shaft 72 as indicated by arrow C<SP>1</SP> to cancel out some of the cyclic pitch initially imparted to the control blades by the swash plate mechanism. The input leverage X/Y of the linkwork is preferably 2¢ to 1 and the feed-back ratio D/L is preferably 1. Specifications 645,234, 713,358 and 735,572 also are referred to.