GB605561A - Improved pitch controlling means for rotor blades of helicopters - Google Patents

Abstract

605,561. Helicopters. NEALE, J. S., and PENNINE AIRCRAFT, Ltd. March 24, 1945, No. 7472. [Class 4] A blade pitch control system for helicopters is characterized by means responsive to aerodynamic forces on the blades to effect cyclical pitch changes thereof automatically, so that the pitch of the blades is varied by changes in their airspeed. In the form illustrated the rotor carries three blades 19 whose roots are rotatably mounted in sockets 17 for pitch changing, and is mounted on a spherical bearing 10 for adjustment in azimuth, effected by pushpull control members 12. The latter serve as conduits for hydraulic pressure liquid for effecting collective pitch control of the blades, the liquid operating spring-loaded pistons 27 which actuate pistons 33 moving in cylinders 34 communicating with upper and lower sets of cylinders 35, 36, each of which contains pairs of spring-loaded pistons 35a, 36a, connected to diametrically opposed crank arms 38 at the ends of the blade roots. The profile of the rotor blades is such that they tend to assume smaller angles of attack with increasing airspeed, whereby the blade moving at the greatest relative velocity will tend to reduce its angle of attack, so transmitting an impulse to the constant-volume hydraulic system, and increasing the pitch of the remaining blades against the action of the piston springs which are so disposed as to oppose pitch increase, whereby during rotation of the blades there is a continuous automatic cyclic change of pitch.