GB645234A - Helicopters - Google Patents

Abstract

645,234. Helicopters. UNITED HELICOPTERS, Inc. June 3, 1948, No. 15004. Convention date, June 3, 1947. [Class 4] The cyclic pitch adjustment of the blades of a helicopter rotor is effected by a servo control rotor, the blades of which are subject to cyclic pitch control initiated by the pilot. As shown, the main rotor comprises two non-articulated blades 21, the hub 19 being carried on the drive shaft 22 by a universal mounting, the axes of which are parallel and perpendicular to the longitudinal axes of the blades, and the servo rotor comprises two small blades 56 disposed below and perpendicular to the blades 21. The pitch setting of the servo blades 56 is controlled by a gimbal ring 81 connected by links 80 to a pilot-controlled ring 68. Inclination of the servo rotor tip path plane consequent upon unequal pitch settings of the blades 56 is communicated to the main rotor pitch control arms 79 by links 80<SP>1</SP>. Collective pitch control of the main rotor blades is effected by axial movement of the control ring 81 along the drive shaft 22. Fig. 9 shows the control arrangement for a helicopter with co-axial contrarotating rotors 21, 21a, the collective pitch of the blades being varied by a vertically-movable axial rod 82 inside the drive shaft 22. Such an arrangement may also be used for collective pitch control of a single rotor, Fig. 8 (not shown).