Patent GB-866013-A (GB)
Title: Aircraft flight instruments
IPC: G01S1/02
Filed: 1957-04-16
Abstract: 866,013. Attitude-indicating instruments for aircraft. SPERRY ROAD CORPORATION. April 16, 1957 [April 23, 1956], No. 12417/57. Class 4. An attitude indicating instrument for aircraft comprises a fixed casing 11 enclosing a vertical axis gyroscope 18 mounted on a transverse horizontal axis in roll gimbal 38 in turn mounted for movement about a longitudinal horizontal axis 61. A mask 16 is mounted by arm 19 on roll gimbal 38, and it carries diametrically opposed bank indexes 13 and 34. A meter movement 37 is supported by roll gimbal 38 with its axis coincident with the roll axis of the gyro, to operate a steering index 33. An horizon bar 12 extends across the front of mask 16 and is coupled to gyro 18 so that it indicates both pitch and roll of the aircraft, and a miniature aeroplane index 14 also extends across the face of the mask for vertical movement under the control of a meter movement 44. The front of casing 11 carries a bank angle scale 15 and diametrically opposed fixed indices 17, 17<SP>1</SP> and an annular compass card 20 formed with a heading scale is visible through a window in the front of the instrument, being mounted for rotation by gearing 32 concentrically about mask 16 to provide a heading indication against fixed lubber line 23. A further window 27 displays reciprocal heading indicia and an indicator 26 displays a selected or desired heading as selected by a control knob 25. A heading index 24 is driven through gearing 35, 36 from a differential 30 which has one mechanical input from selector knob 25 and another from a servo 29 responsive to the output from a directional gyro 21. Meter movement 44 can be supplied through combining circuit 46 and lead 62 with signals from an angle of attack sensor 45, a barometric type altitude detector 49 and a glide slope radio receiver 51. The outputs of sensor 45 and receiver 51 may be trimmed respectively at 47 and 52<SP>1</SP> and the resultant output signal from trimmer 52<SP>1</SP> is fed to contact APP (for approach) of a switch 48. A switch 42 ganged to switch 48 selects the output signal from a localizer radio receiver 41 from contact LOC (for localiser) or APP (for approach) or the receiver is isolated when the movable contact is located at F.I. (for flight instrument). The output signal is connected through a reversing switch 40 and lead 39 to meter movement 37. In use, when the aircraft banks the spin axis of gyro 18 remains vertical, causing mask 16 and horizon bar 12 to rotate with respect to stationary indexes 17-17<SP>1</SP> and 15 to indicate the amount of roll. With change of aircraft pitch horizon bar 12 rotates about the axis of gyro 18 to indicate pitch by reference to fixed indexes 17, 17<SP>1</SP>, The signal produced by gyro 21 causes simultaneous rotation of compass card 20 and heading index 24 so that the compass bearing under lubber line 23 indicates actual heading, and heading error is indicated by reading index 24 against line 23. During such movement selector knob 25 is located in an " in "position for engagement by a movement-preventing clutch 31, but to select a given heading the knob has to be pulled " out " from engagement by the clutch. When the signal from receiver 41 is passed through contact LOC, indicator 33 moves to left or right of its neutral position as the aircraft moves to right or left of its radiodefined course. Since meter movement 37 is mounted on roll gimbal 38, the visible indication is both a function of the position of the aircraft with respect to the radio beam and also the roll attitude of the aircraft. Movement of switch 42 to contacts APP stabilises the signal at close range. In an alternative embodiment windows 26 and 27, compass card 20 and index 24 are dispensed with and the heading selector provides an electrical instead of a mechanical input between gyro 21 and a meter movement equivalent to movement 37, which is also operated as in the first embodiment by receiver 41. Specifications 643,613, 771,017, 866,014 and 866,015 are referred to.