GB598878A - Improvements in or relating to rotary wing aircraft - Google Patents

Abstract

598,878. Rotary-wing aircraft. FAIREY AVIATION CO., Ltd., and BENNETT, J. A. J. Sept. 21, 1945, No. 24535. [Class 4] A rotary wing aircraft has a rotor in which each blade is provided with a flapping and a drag pivot, but not a feathering or torsional pivot, the blades being mounted on drag links so shaped that the drag hinge is spaced from the axis of rotation and offset from the flapping pivot, and the drag pivot being so located that the angular displacement of the blade in azimuth in response to torque causes the collective pitch of the rotor to vary automatically with variation in rotor power to keep the speed of the rotor substantially constant. The drag pivot allows a sufficient forward angular displacement to decrease the rotor pitch to Zero or a negative value when the rotor brake is fully applied. As shown, the blades are mounted by drag links e<1> on a tiltable rotor head c. If k is the position of the blades for zero torque, A the angle of lag for a torque Q, Ao the angle of lag when the blades are normal to the flapping axis X-X, F the centrifugal force on a blade, Bo the blade pitch at a lag of Ao, B the blade pitch at a lag of A, C the coning angle and x the distance of the drag pivot j from the axis of rotation : approximately. By suitably choosing x, the required variation of pitch with variation of rotor power may be obtained without providing a feathering or torsional pivot for each blade.