GB618670A - Power assisted controls for aircraft - Google Patents

Abstract

618,670. Power-assisted aircraft controls. MOSS, N. Nov. 11, 1946, No. 33465. [Class 4] [Also in Group XXXVII] In a power-assisted aircraft control system a pushpull member operated by the pilot is arranged to divide the load in constant proportions between the pilot and a reversible motor. In the form shown, the push-pull rod is in two portions 1, 2, the adjacent ends of which are formed with screw-threads 3, 4 of the same hand but different pitch, and connected by a housing 8. The rod portions 1, 2 are connected to the pilot's control member and the control surface, respectively, and the pitch of the thread 4 is less than that of thread 3. The housing 8 is carried by a bearing 10 in a member formed with racks 9 engaged by pinions 12 on a cross-shaft 13 carrying a worm wheel 14 driven by a worm 15 on a reversible direct-current motor 16. As shown in Fig. 3, power for the motor 16 is supplied by a separately excited opposed field generator 17 driven at constant speed, the motor torque being varied by regulating pile resistances 18 in the generator field circuits. The resistances are controlled by an arm 21, carried by a sleeve mounted on a fluted portion of the housing 8. The rod portions 1, 2 are prevented from rotating by pin and slots 5, 6, so that the initial movement of the pilot's control member produces equal forces in the members 1, 2, resulting in an unbalanced torque being applied to the housing 8, thereby rotating it and the member 21 to energize the motor 16 and move the control rod through the racks and pinions 9, 12. The motor ceases to operate when the ratio of the loads in the members 1, 2 is equal to that of the pitches of the threads 3, 4, the unbalanced force being taken by the racks and pinions. Trimming may be effected by adjusting the arm 21 through a linkage and trimming wheel. A hydraulic motor may be used instead of an electric motor.