GB515515A - An improved indicator for retractable undercarriages of aeroplanes and similar devices - Google Patents

Abstract

515,515. Electric indicators. BRISTOL AEROPLANE CO, Ltd.. FRISE, L. G., and HEARDER, R. POLLINGTON-, March 5, 1938, No. 6976. [Class 40 (i)] An instrument for indicating to the pilot of an aircraft the position of the retractable undercarriage comprises two electromagnets or solenoids 19, 20 adapted to be energized selectively so as to move a pivoted armature into one or other of two positions corresponding to the " up " and " down' positions of the undercarriage, the armature being provided with adjustable means for balancing it against inertia forces and with a pointer or like indicator. As shown, the instrument comprises a rear wall 10,adapted to be secured to the instrument board and carrying terminals 11, 12 connected to the solenoid windings and to switch contacts (not shown) adapted to be engaged by the undercarriage. On the wall is mounted an outer frame 13 having a transparent cover 14 and surrounding an inner frame 15 the front portion 16 of which is formed as a dial bearing the words " up " and " down " and carries a bracket 18 supporting the solenoids 19, 20, the central part 21 of the bracket having adjustable bearings 22, 23 for an axle 24. To a U-shaped metal strip 25 secured to the axle are fixed an arm 26 carrying a shield 17, members 27, 28 carrying soft-iron pole pieces 29, 30, and a screw-threaded spindle 31 carrying an adjustable balancing mass 32 lockable by nuts 33, 34. The shield 17 is movable over the dial 16 and in order to maintain it in an intermediate position, corresponding to an intermediate position of the undercarriage or for indicating a failure in the electric circuit, the part 21 of the bracket 18 also carries a U-shaped spring 35 the limbs of which embrace the strip 25. On energization of either solenoid the shield 17 moves over the dial and uncovers the appropriate word. Specification 147,194; [Class 40 (i)], is referred to.