Patent GB-811523-A (GB)
Title: Improvements in navigational instruments
Inventor: MAJENDIE ALASTAIR MICHAEL ADAI
IPC: G01S1/02
Filed: 1955-08-08
Abstract: 811,523. Aircraft indicating instruments. SMITH & SONS (ENGLAND) Ltd., S. Nov. 8, 1956 [Aug. 8, 1955], No. 22855/55. Class 4. [Also in Group XL(c)] A navigational instrument for aircraft comprises a case housing a bearing scale 1 mounted for rotation about an axis parallel to the case axis for movement with respect to a fixed datum mark 2 under control of a gyro-compass 6 operating through synchro transformer 3, amplifier 4, motor 5 and gear train 5a to indicate magnetic heading of the aircraft. A moveable datum marker 7 carried on a gear ring 7a overlies scale 1 and is positioned by the output of a differential gear 8, one input to which is provided by gear 9 driven in accordance with aircraft heading by motor 5, the other input being provided by a planet carrier 10 operated by a heading selector knob 11 which is used to give marker 7 a selected heading reading on scale 3. Thus, with no adjustment of knob 11 marker 7 will remain in the selected position on scale 1 as heading changes. A heading counter 12 is mounted above mark 2 and geared to carrier 10 (duplicated for convenience of illustration in Fig. 3) to display the position of marker 7 relative to scale 1. Pointers 14 and 15, distinguished respectively by the forms of single shafted and double shafted arrows, are provided for rotation about the axis of the instrument by conventional torque receiver synchro devices 16 and 17 in accordance with the bearings from the aircraft of two fixed radio stations. The synchros 16 and 17 are respectively connected to torque transmitter synchro incorporated in the directional radio equipment of the aircraft. The instrument enables an aircraft to be navigated in relation to the two fixed radio stations so that it follows a path on a constant bearing from the first station until it is at a selected bearing from the second and thereafter follows a path on the selected bearing from the second station. The heading selector knob 11 (and consequently marker 7) is adjusted so that the selected bearing appears on counter 12 and while on the constant bearing from the first station the pointer 15 will be directed towards the point on scale 1 corresponding to the bearing of the station from the aircraft. The angle between pointer 14 and the datum marker 7 is that between the actual bearing of the second radio station from the aircraft and the selected bearing. Thus, when pointer 14 reaches datum marker 7 it is known that the selected bearing from the second station has been reached and the angle between datum marker 7 and fixed mark 2 indicates the angle by which the heading must be changed to bring the craft on to the selected track. An embodiment is described, Fig. 4, (not shown), in which the instrument may be adapted to produce an output signal in accordance with the angular displacement of the aircraft from the selected bearing from the second station, which signal after demodulation, may be applied to an automatic pilot or steering indicator. Specifications 586,506 [Group XXXVI] and 763,121 are referred to.