Patent GB-713015-A (GB)
Title: Aircraft control mechanism
IPC: B64C13/24
Filed: 1951-09-05
Abstract: 713,015. Controlling aircraft. NORTHROP AIRCRAFT, Inc. Sept. 5, 1951 [Nov. 13, 1950], No. 20975]51. Class 4 An aircraft control mechanism includes two oppositely moving taut cables each connected to a first actuator at one end and to a device to be actuated at the other end, said cables leading to opposite respective sides of an idler pulley means freely rotatable on an axis fixed to a structural support, then respectively extending to the outer sides of two auxiliary pulleys rotatably mounted one on each of two oppositely extending arms of a bellcrank member rotatable on an axis fixed to said support, said pulleys being at points equidistant from said bellcrank axis, the point of contact of each of said cables on the side of its auxiliary pulley nearest said idler pulley means describing an approximate involute curve of said idler pulley means when said bellcrank is rotated a relatively small amount, and an irreversible driving connection from a second actuator to a positive driving means connected to said bellcrank whereby said second actuator and bellcrank are not rotated by movement of said first actuator and said device. The apparatus controls an aircraft rudder wherein normal actuation of the rudder for directional control is achieved by a hydraulic actuator 29 connected to a lever 31 attached to the rudder post and a further actuator 42, forming part of an automatic yaw-controlling system, also adjusts the position of the rudder, the apparatus permitting pilot controlled actuation of the valve 27 of the actuator 29 and automatic actuation of the rudder by the actuator 42, the two systems operating independently of one another. The rudder pedals 3, 4 are connected respectively to cables 5, 7 running on pulleys 6, the cables being wound round a cable drum 12 and crossed and carried rearwards round idler pulleys 16 mounted on a common pivot 17. The cables then cross round auxiliary pulleys 19 mounted on the extremities of arms of a bellcrank 20 mounted on a fixed pivot 21 and are then passed over guide pulley 6a and round a pulley 22 mounted in a stirrup forming part of the mounting of the actuator 29. The pulley 22 has a pivotal connection with a rod 26 which actuates the control valve 27. The actuator 42 drives a sheave 41 through an irreversible driving assembly 44 and the sheave 41 drives a continuous cable 37 wound round pulleys 40 and connected to an arm 39 extending from the bellcrank 20. Movement of the rudder pedals 3, 4 actuates the cable system to operate the valve 27, the irreversible mechanism 44 holding the bellcrank 20 in a fixed position. If, as a result of change of yawing attitude of the aircraft, actuator 42 is automatically operated, the cable drive 37 rotates the bellcrank 20 about its pivot 21, resulting in an adjustment of the cables 5, 7 aft of the pulleys 16 and consequent adjustment of the valve 27. The rudder pedals are provided with a centring means 10, which restrains the forward cable run from movement when actuator 42 is operated. If more restraint is needed a spring loaded lever arm 46 may be pivoted to the fuselage and provided with a roller 47 which, with the rudder neutral, engages a cut-out portion in the cable drum 12. The system incorporates an auto-pilot 45.