Patent GB-611008-A (GB)
Title: Improvements relating to the control of aircraft and to the mounting of instruments on aircraft
IPC: G01C21/18
Filed: 1942-09-25
Abstract: 611,008. Automatic control systems for aircraft. SMITH & SONS (MOTOR ACCESSORIES), Ltd., S., and MEREDITH, F. W. Sept. 25, 1942, No. 13527. [Class 38 (iv)] Attitude; steering.-An automatic control system for an aeroplane comprising a rate-ofturn instrument of the kind described in Specification 611,005, [Group XXXVIII], which stabilizes the aeroplane about one of its axes, has the rate-of-turn instrument mounted on a platform or other member which can be tilted relatively to the aircraft with reference to the said axis so that the distance of stabilization is varied and the aeroplane caused to turn about the axis, whereby the platform is maintained in a predetermined position relative to the vertical. Any instrument, such as a rate-of-yaw device, compass, rate-of-roll device, rate-of-pitch device, bomb-sight, camera, telescope or guns which requires at any time to be in a definite position in relation to the true vertical such as on a horizontal base, may be mounted on the platform. When the axis of reference is fore-andaft, the angle of bank is determined by the tilt given to the platform and a rate-of yaw device controlling the course of the aeroplane may be mounted on the platform and turned at a rate correctly related to the imposed angle of bank to cause the plane to turn without side slip. A rate-of-turn device may be mounted with an inclined axis upon the platform so as to control the craft about the roll axis as well as the yaw axis. A compass controlling the aircraft has its north turning error eliminated and both rate-of-yaw device and compass may be mounted on a motor-driven turntable on the platform. A rate-of-pitch device also on the platform may control the elevators. Fig. 1 shows course-controlling means 21 comprising a rate-of-yaw device and compass on a turntable 15 which is driven by a D.C. motor 19 at a speed determined by the tilt applied to a platform 14 carrying the turntable and a rateof-roll device which controls the ailerons. The motor field is determined by setting a potentiometer 29 in accordance with air speed and the armature voltage is derived from a linear potentiometer at right angles to the normal plane of the platform so as to be proportional to the tangent of the angle of tilt. The bank angle may be indicated on a voltmeter V. Fig. 2 shows a rate-of-turn instrument 34 which is tilted so as to measure rate of yaw and rate of roll and which, with a compass 32 on a manually-controlled turntable, controls the ailerons. The instrument 34 is mounted on the platform 14 and is of the kind described in Specification 611,005 and its output is an A.C. voltage, the amplitude of which is a measure of the rate of turn combined with a carrier wave of the same frequency but of constant amplitude. The turning of the craft is effected by applying across the potentiometer 22 an A.C. voltage in opposition to that supplied by the rate-of-turn instrument 34. Tilting of the platform takes off from the potentiometer an A.C. voltage proportional to the tangent of the tilt and applies it across a resistance 35 and condenser 36 in series, the voltage across the latter being opposed to the voltage from the instrument 34. The resistance 35 is adjusted to be proportional to air speed and the condenser reactance to be proportional to air density. If the rate-of-turn instrument is not tilted, it may be used to measure rate of yaw. Specification 578,303, [Group XXXVI], also is referred to.