Patent GB-758810-A (GB)
Title: Improved simulated flight and radio navigation apparatus
IPC: G09B9/26
Filed: 1954-12-08
Abstract: 758,810. Electric indicating systems. DEHMEL, R. C. Dec. 8, 1954, No. 35600/54. Class 40(1) [Also in Groups XXXIII and XL(c)] Relates to ground-based apparatus for training aircraft pilots in the use of a "zero-reader" flight instrument having movable horizontal and vertical pointers 7 and 8 normally intersecting at a centre zero 6, the vertical pointer 8 being displaced horizontally by a control signal proportional to the algebraic sum of the heading error and the roll angle and when required, the lateral displacement of the craft from a radio defined track and the horizontal pointer being displaced vertically by a control signal proportional to the algebraic sum of the pitch error and the vertical displacement of the craft from either a desired altitude or from a radio defined glide path. In such apparatus the heading error and roll angle are proportional respectively to the first and second time derivatives of the lateral displacement and the pitch error is proportional to the first derivative of the vertical displacement. According to the present invention the apparatus comprises a flight simulator having four units 24, 17, 60 and 73 with output shafts whose angular positions are proportional respectively to the simulated heading, roll, pitch and altitude and a unit (not shown) providing A.C. voltages ex and ey representing the cartesian coordinates of the craft. When the simulated radio track corresponds to that produced by a localizer beacon or by a visual-aural range beacon the voltages ex and ey are applied to a resolver 43 producing a voltage e1b proportional to the simulated lateral deviation of the craft from the track and a voltage er proportional to the simulated radial distance of the craft from the beacon as described in Specification 650,757 [Group XL(c)] and when the simulated is off-set from an omni-range beacon a deviation voltage elb may be produced as described in Specification 693,821. The output shaft of the heading simulator 24 controls the angular position of the rotor 22 of a selsyn transmitter 22. 25 coupled to a selsyn receiver 20. 26 whose rotor 20 is set to the heading of the desired track by a dial 28 and the A.C. output from rotor 20 which is proportional to the heading error is combined with the displacement voltage elb in summing amplifier 34 and applied through limiter 35 to one input of summing amplifier 14. The output shaft of the roll simulator 17 controls the wiper 16 of a centre-tapped potentiometer 15 giving an A.C. output proportional to roll which is applied to the other input of amplifier 14 whose output is applied through a phase-sensitive rectifier 13 to control the horizontal position of pointer 8. The output shaft of the altitude simulator 73 controls directly the wiper 87 of a first potentiometer 85 (one end earthed) and via step-up gearing 75 and magnetic clutch 76 a shaft 77 controlling the angular position of the spring-centred wiper 71 of a centre-tapped potentiometer 72. For simulated constant altitude flight, switch 80 is closed to energize clutch 76 when the altitude simulator 73 represents the desired altitude and the A.C. output from potentiometer 72 which is thereafter proportional to altitude error is applied through contact 66 of switch 65 and limiter 69 to one input of summing amplifier 57, the other input thereto being taken from a centretapped potentiometer 58 whose wiper 59 is controlled by the pitch simulator 60; the pitch datum is set by manual control of the potentiometer card 63. The output from amplifier 57 is applied through phase sensitive rectifier 56 to control the position of the horizontal pointer 7. To simulate a radio glide-path landing, switch 65 is thrown to contact 67. An A.C. voltage from potentiometer 85 proportional to altitude is subtracted in amplifier 82 from the A.C. range voltage er from resolver 43 to give a resultant voltage proportional to deviation from the glide path as described in Specification 650,757 which is applied to limiter 69. A curved glide path may be simulated by using a non-linear potentiometer 85. Switching. The dispacement voltage elb is applied to amplifier 34 through switch 38 which has four contacts 39 ... 42, contacts 40, 41, 42 having inputs corresponding respectively to displacements from a localizer track, a range track and a track off-set from an omni-range beacon and contact 39 being kept blank so that in this position no displacement voltage is applied to amplifier 34 and pointer 8 then indicates deviations from the heading selected by dial 28. Switches 38, 65 and 80 are preferably ganged, Fig. 2 (not shown), so that localizer and glide path control is effected simultaneously.