Patent GB-821705-A (GB)
Title: Improvements in or relating to computing and indicating apparatus for use in aircraft navigation
Inventor: PARSONS JAMES STUART
IPC: G01C21/20
Filed: 1956-08-27
Abstract: 821,705. Navigation instruments. CANADIAN PATENTS & DEVELOPMENT Ltd. Aug. 27, 1956, No. 26199/56. Class 97(2) [Also in Group XXXIII] An aircraft navigation instrument comprises a crossed marked indicator system for indicating computed co-ordinates of position derived by adding, in differential gearing devices, integrated components of resolved aircraft speed to integrated wind components, a further differential device being provided for adding to the drive representing wind a high speed drive by which the co-ordinates of a reference point in the display may be changed by an amount indicated on a counter. In the form shown a compass repeater 32, the stator of which may be rotated by a knob 35 to correct for magnetic variation, is operated by a master compass 33 and drives through a correcting device 36, a shaft 77, which drives both a compass dial 92 and a resolver 28 comprising gears 30, 31 carrying pins 75 and 76 which generate sine and cosine functions of the rotation. A commutator device 29 is rotated in terms of airspeed to produce a number of pulses on a brush 74 proportional to it. A drum 80, driven by a motor 81 has a triangular contact 79 wrapped round it and connected to the brush 74. Contacts 82, 83 actuated by the pins 75, 76, receive, in consequence, numbers of pulses proportion to the E-W and N-S components of air speed. These sets of pulses are integrated by stepping type motors 27, 71, which may be reversible motors controlled by electromechanically actuated escapements. The motors are reversed by contacts 84, 85 as the components from the resolver 28 change sign. A motor 47 is set, by a variable resistance 48, to rotate at a speed representing wind velocity and drive, through a differential 45, a disc 44 and a counter 53, driven through a clutch 51, showing the integrated effect of wind. Wind direction is set by a knob 90 on to a dial 91 and a gear 42, having a planetary gear to form a resolver which sets sine and cosine functions of wind direction on to bald carriages 41, 73, so that integrated displacements of the aircraft, due to wind, appear on the rollers 39, 72 and are added to the components due to aircraft speed, in the differentials 25, 70. The total E-W displacement is fed to a splined shaft 19 which drives a gear 18 and, through gears 16, 17, a lead screw 15 on which moves a carriage having a pin 13 which pivots a lever 12 to move a slide 11 carrying vertical hue across the dial assembly. The total N-S displacement is similarly fed to a horizontal line, so that the intersection of the two lines represents the position of a fixed reference point relative to the aircraft position. The leadscrew 15, and associated parts, together with the corresponding parts for the N-S displacement are all mounted on a carriage 94 movable, to change the scale of the dial presentation, on a leadscrew rotated by a motor 96 under control of a switch 103 and limit switches 104, 105. Limit switches 106, 107 interrupt power to the motors 27, 71 to prevent the displayed displacements becoming excessive. An additional motor 86, driving into the differential 45, permits a vector quantity to be set into the mechanism to change the reference point indicated by the crossed lines of the dial assembly. The direction required is set by the wind setting knob 90 on the dial 91 and the magnitude of the displacement is set on the counter 53 by the crank 62 thus slipping the clutch 51. At the same time an arm 60 is set with reference to a limit switch 61. When a switch 93 is actuated the motor 86 drives the necessary displacement into the mechanism until arm 60 actuates the limit switch 61. The wind data may then be re-set in the mechanism. Specification 803,128 [Group XXXIII] is referred to.