Patent GB-848438-A (GB)
Title: Aircraft attitude display instrument with differential pitch trim insertion
IPC: B64D45/00
Filed: 1958-02-03
Abstract: 848,438. Aircraft indicators. COLLINS RADIO CO. Feb. 3, 1958 [May 31, 1957], No. 3498/58. Class 4. An aircraft instrument includes angular position transducers positioned in accordance with a vertical reference (e.g. a gyro), one transducer positioning an angle of bank indicator, and the other positioning a first input shaft of a mechanical differential, the second input shaft of which is positioned by a pitch trim control, and an angle of pitch indicator positioned by the output shaft of the differential. A transducer associated with a gyro vertical 70 provides an electrical output representing bank angle, which energizes the rotor coils of a bank synchro 30. The rotor is driven by a gear 26 fast to a shaft 25 driving a disc 18 marked with a horizon bar 19 visible through an instrument face mask 11. The stator of synchro 30 develops an error signal fed through amplifier 29 to a motor 28 driving gear 26, so that the angular position of shaft 25 represents the bank angle. A transducer 9 is driven by gear 26 and has an electrical output representing bank angle available for use anywhere in the aircraft. By a similar arrangement, pitch signals from a transducer in the vertical gyro 70 energize a pitch synchro 31, the rotor of which is driven by a motor 33 through a gear trim 35, gear 36, shaft 37, and gear 39, so that shaft 37 is driven into correspondence with the pitch angle, any error signal developed in synchro 31 energizing motor 33 through amplifier 24. A transducer 32 is driven by gear 39 and has an electrical output representing pitch angle available for use anywhere in the aircraft. Gear 39 engages a pinion 46 meshing with a pinion 47, both pinions being mounted on a sector 48. Pinion 47 engages gear 40 on a hollow shaft 38 driving a cam 42. Sector 48 is fast on a shaft 49 co-axial with shafts 37, 38, and driven by a toothed sector 50, worm 51, shaft 52, and knob 14 cooperating with a graduated escutcheon 20 on the front of the instrument face. The angular rotation of shaft 38 represents the algebraic seam of the rotations of shafts 37 and 49. The pitch bar 22 is operated by an arm 44 having a cam follower 45, whereby the pointer indicates departure of the angle of pitch from a trimmed reference pitch set by knob 14. Cam 42 has a non-linear contour, so that the sensitivity falls off as the pitch angle departs from the trimmed reference pitch. A shaft 53 extending within and secured to shaft 52 has a cam member 55 cooperating with a roller 56 on a centrally pivoted lever 57 biassed by a spring 61 so that roller 56 tends to contact cam 55. Normally roller 56 is held away from cam 55 by a cam 60 rotatable between two positions by a motor 66 controlled by a limit switch circuit 67, so that the pilot can select any desired pitch trim by rotating knob 14, whereby pitch bar 22 indicates zero pitch when the aircraft is at the desired pitch attitude. During an I.L.S. approach, however, a knob 15 is tuned, actuating switch 68 and circuit 67, rotating cam 60 so that roller 56 rotates cam 55 and shafts 53, 52 to apreset position, corresponding to the predetermined pitch attitude required during landing approach by instruments. Bar 22 then indicates departure from this pitch attitude. The relative angular positions of shaft 53, shaft 52, and worm 51 can be adjusted initially to set up the instrument. A guide slope receiver 83 operates a vertically moving pointer 12, and a computer 71 receiving radio navigation signals, and heading information, operates a pointer 23 indicating steering information. Specification 819,456 is referred to.