Patent GB-807512-A (GB)
Title: Aircraft navigation instruments
IPC: G01S1/02
Filed: 1955-07-15
Abstract: 807,512. Aircraft navigation instruments. SPERRY RAND CORPORATION. July 15, 1955 [July 30, 1954], No. 20545/55. Class 4. [Also in Group XL(c)] In an aircraft navigation instrument the heading of the craft relative to the direction of a radio-defined track, i.e. the heading error, and the deviation of the craft from the track are indicated respectively by the relative angular and lateral displacements of an index 5 representing the aircraft and a V-shaped pointer 6 representing the track. The track may be one passing through a V.O.R. beacon, the direction of the track being selectable by the pilot, or it may be a fixed track defined by a localiser beacon. Means are also provided such that when the track is defined by a V.O.R. beacon, the V-shaped pointer 6 is directed upwards or down wards according to whether the aircraft is flying towards or away from the beacon. Further means are also provided for indicating the deviation of the craft from a predetermined altitude or from a radio-defined glide slope. In the preferred embodiment Fig. 1, the index 5 is fixed and the pointer 6 is rotated and displaced transversely to itself in accordance with the heading error and track deviation respectively. In a first modification, Fig. 9, the index 5 is rotated in accordance with the craft's magnetic heading and the pointer 6 is rotated in accordance with the direction of the track and displaced transversely to itself in accordance with the craft deviation. In a second modification, Fig. 10, the index 5 is rotated in accordance with the heading error and the pointer 6 is maintained vertical and displaced horizontally in accordance with the craft deviation. In the preferred embodiment, Figs. 1 and 2 and Figs. 3-6 (not shown), the index 5 is marked on the inner surfaces of the fixed instrument bezel glass 4 and the pointer 6 is attached by an arm 19 to the rotor 20 of the displacement meter movement 18 which is mounted in a gimbal frame 7 pivoted by coaxial shafts 8 and 9 whose angular position is controlled through gears 16, 17 by a heading servo motor 14. A part spherical background member 11 is secured to the end of the shaft 8 and the arm 19 projects through a slot 21 in the member 11 ; the extent of lateral displacement of the pointer 6 is indicated by the dotted. scale 22 on the member 11. When operating with a V.O.R. beacon producing at the craft receiver 23, Fig. 2b, reference and direction signals of relative phase proportional to the bearing of the craft from the beacon, the bearing of the desired track is set in by a knob 12, Fig. 2a, which controls a phase shifter 74 and the angular position of the stator 53 of a control selsyn 13 whose rotor 54 is geared to the shaft 9. The stator 53 is connected to a selsyn transmitter 51, Fig. 2b, actuated by a gyro magnetic compass 50 and the output from the rotor 54 is applied through an amplifier 15, Fig. 6 (not shown), to actuate the servo motor 14 to set the angular position of pointer 6 in accordance with the heading error of the craft such that when the craft is approaching the beacon the apex of pointer 6 is directed upwards. The beacon direction signal and the phase-shifted reference signal are also applied to a Flag circuit 71 and a To-From circuit 73. The output from circuit 71 energises a warning flag actuating device 72, Fig. 2a, when the beacon signal is unreliable. The To-From circuit 73 may operate as described in United States Civil Aeronautics Administration Technical Development Report No. 113 to produce a D.C. control signal which changes polarity when the aircraft passes over the beacon. This signal is applied through an amplifier 77, Fig. 5 (not shown) to energise a relay 78 which energizes a To-From relay 57 to reverse the phase of the output from the heading control selsyn 13 thereby rotating the shaft 9 and pointer 6 through 180 degrees so that when the aircraft is flying away from the beacon the pointer 6 is directed downwards ; alternatively relay 57 may be energized directly by the output from the amplifier 77. The above operation also inverts the displacement movement 18 and in order to preserve the correct displacement sense, relay 57 also reverses the polarity of the displacement signal from comparator 70. If the craft is not on the track an asymptotic approach thereto can be effected by controlling the craft to maintain the apex of the pointer 6 at an index 6<SP>1</SP> at the top centre of the instrument dial. When the track is flown in the reciprocal direction, the outputs from the heading selsyn 13 and the bearing phase shifter 74 must be reversed and this is effected by a relay 56, Fig 2b, energized through a switch 43, Fig. 2a, actuated by a lever 42 which is operated by the pilot when executing the 180 degrees turn onto the reciprocal course. The bearing selector 12 also controls a counter 24, Figs. 3 and 4 (not shown), which displays the bearing and reciprocal bearing of the selected track, the display being viewed through a shutter 40 controlled by the lever 42 so that only the appropriate one of the two bearings is visible. The bearing selector 12 and relay 56 may also control a selsyn 150 associated with an auto pilot 152. Figs. 7 and 8 (not shown) illustrate the appearance of the instrument during various stages of a flight. When operating with a Localiser beacon whose frequency is selected by a switch 74<SP>1</SP>, the output from the localiser section of the receiver is applied to the displacement movement 18 and the ganged switch 100 is opened thereby de-energizing a relay 81 to de-energize the To-From amplifier 77 and also apply the output from the Glide-slope receiver to a meter movement 75 to produce a vertical deflection of the horizontal pointer 76; during V.O.R. operation the pointer 76 is either deflected out of sight by a steady voltage or deflected by an altitude error signal. In the modifications, Figs. 9 and 10, the bezel glass carrying the index 5 is rotatable by a peripheral gear. In the first modification, Fig. 9, this gear is driven by an additional servo motor controlled directly by the compass selsyn 51 and the servo motor controlling the angular position of the pointer 6 and background member 11 is now controlled by the bearing selsyn 13 only. The selected track bearing is indicated on a fixed compass scale 117 by an index 118 on the rotatable background member 11 and the craft heading error is indicated by the angular position of the index 5 relative to a scale on the background member 11. In the second modification, Fig. 10, the heading servo motor is controlled as in Fig. 2 but it now drives the rotatable bezel glass and the gimbal 7 is stabilized by an additional servo to maintain the pointer 6 vertical. In each modification the polarity of the displacement signal is controlled by the To-From relay 57 as in Fig. 2 but in Figs. 9 and 10 the other contacts of relay 57 control the track bearing signal and vertical stabilisation signal respectively and these signals are also controlled by the reciprocal bearing relay 56 which also controls the output from phase shifter 74 and auto pilot selsyn as in Fig. 2.