GB652817A - Improvements in means for controlling the pitch of rotor blades of helicopters - Google Patents

Abstract

652,817. Helicopters. PENNINE AIRCRAFT, Ltd., and NEALE, J. S. Sept. 14, 1948, No. 24104. [Class 4] Means for effecting collective pitch change in all the blades of the rotor of a helicopter comprises a universally supported tiltable member 42, disposed about the shaft 1 carrying the blades 17, and having its axis of tilt on the shaft axis and having at points equidistant from each other and from said axis connections 36 to the blade roots so that the aerodynamic forces on the blades are transmitted to the tiltable member so as to effect a cyclic change of blade pitch and has means damping the tilt of the tiltable member and means to vary the position of the axis of tilt along the axis of the shaft 1 to effect a collective pitch change. The main shaft 1 is mounted on a bracket 11 by bearings 8, 12 and is rotated by the shaft 4 through bolts 5 and rubber blocks 6. A spherical member 14 at the top of shaft 1 carries the hub 22 on which are mounted the blades 17 for rotation about their root axes. Rubber bushes 20 allow a restricted and damped universal movement of the hub 22. Members 36 attached at one end to the blade roots are universally jointed at 37 to a swashplate 42 carried by a spherical seating 38 on the shaft 1. A non-rotary ring 44 is connected to the swashplate by a ball race 43 and by universal joints 47 to the pistons 48 of a number of dash pots 40 arranged arround the shaft 1. Translation of the swashplate for collective pitch change of the blades is effected by a sleeve 50 screwed on a stationary member 49 and rotated by cables 54. Each blade 17 is so mounted that its centre of pressure is displaced from the axis of pitch change and the torsional impulses generated by the aerodynamic forces acting on the blades are fed into the damped swashplate, there being no pilot's control for tilting the latter.