GB380392A - Improvements in and relating to navigational apparatus - Google Patents

Abstract

380,392. Earth inductor compasses. THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Rhea, T. R. ; 1031, Wendell Avenue, Schenectady, New York, U.S.A.) April 19, 1932, No. 11206. Convention date, April 20, 1931. [Class 37.] An earth inductor aero-compass comprising an indicating instrument supplied with a voltage dependent upon the position of the aircraft in the earth's field, and wherein this voltage is controlled by course setting means, is provided with a further voltage variation to correct for drift of the aircraft. As shown, in conjunction with the compass 10 described in Specification 342,038, the course setter comprises a card 26 co-operating with a pointer 27 secured to a worm wheel 28 operated by a hand worm 30. Operation of the worm 30 rotates the shaft 33 in a horizontal plane, and since the gear 37 and worm wheel 38 are looked by the worm 45, the output gear 46 is rotated and effects a movement of the polepieces 16 equal to that of the pointer 27. The optical drift indicator comprises a glass plate 39 provided with hair lines 43 and mounted in a ring worm wheel 40 which is carried in the floor of the aircraft between pairs of rollers 41 and is held against lateral displacement by idler wheels 42. Normally the hair lines are set fore and aft of the craft, drift from a set course being indicated by ground objects crossing the hair lines. Correction for this drift is effected by rotating the worm 45, the gears 34, 35 being locked by the worm 30 against rotation around the axis 32, but rotating on shaft 33. This correcting movement is imparted to the polepieces 16 and a resultant voltage is supplied to the galvanometer 11, adjustment to the central position of the pointer of which holds the craft on its course or on a course parallel thereto.