GB614689A - Aircraft instrument - Google Patents

Abstract

614,689. Aircraft indicating instruments. SQUARE D CO. July 20, 1946, No. 21740. Convention date, Aug. 4, 1945. [Class 4] An aircraft indicating instrument comprises a pointer and relatively movable dials graduated in terms of indicated airspeed and angle of attack to show values of these factors under all conditions of operation, the arrangement being such that the dials do not move relatively to each other under constant loading conditions regardless of changes in airspeed and angle of attack. Fig. 1 is a sectional elevation of the complete instrument and Fig. 2 a diagrammatic arrangement of the chief components. The pointer 32 is mounted on a shaft 31, and the angle of attack dial 61 on a sleeve 58 enclosing the shaft 31, while the airspeed dial 62 is fixed to the instrument casing. The top portion of the dial 61 is graduated in terms of percentage of load, and the scale also bears markings 86, 87 denoting the stalling angle, and the angle corresponding to maximum lift to drag ratio, respectively. A capsule 12 is connected at 14 to a pitot head and moves the pointer 32 in accordance with airspeed through a linkage 16, 17, shaft 18 and a toothed sector 24 engaging a pinion 33 on the shaft 31. The dial 61 is rotated in accordance with variation in angle of attack by a self-synchronous transmission system, the transmitter 74 of which is operated by a wind vane 75. The shaft 37 of the receiver 35 carries a lever 38 which engages a slotted lever 43 on a shaft 44 carrying a pinion 46 which meshes with a pinion 47 rigid with a rotary frame 48. A shaft 52 is mounted within this frame and carries two planetary pinions 53, 54, the former of which gears with an idler pinion 55 engaging a second toothed sector 23 on the shaft 18, the sector meshing with a pinion 57 integral with the sleeve 58 carrying the dial 61. In the event of change in angle of attack without variation of airspeed, the sector 23 and pinion 55 remain stationary, the movement of the frame 48 causing rotation of the planet pinions 53, 54, and consequent rotation of the pinion 57 and dial 61. If a change of loading occurs at constant angle of attack, the frame 48 remains fixed and the sectors 23, 24 rotate the dial 61 and pointer 32 through equal angles. At constant loading the consequent changes in airspeed and angle of attack result in movements of the sectors 23, 24 and the frame 48 such that the dial 61 remains stationary. To compensate for operation of the flaps 73, the latter are connected to the stator of the receiver 35 through cam mechanism 71, a flexible shaft 69, pinions 66, 65, a shaft 64 and gearing 63, 36.