Patent GB-871926-A (GB)
Title: Improvements in or relating to aircraft navigational apparatus
IPC: G05D1/04
Filed: 1957-12-23
Abstract: 871,926. Signalling apparatus for aerial navigation. VIELLE, E. E. Dec. 12, 1958 [Dec. 23, 1957], No. 39928/57. Class 118. [Also in Group XL (b)] A navigational apparatus enabling an aircraft to fly at a preselected height above the ground, e.g. contour fly, comprises a map marked to show height, means to derive automatically from the map the marked height at the actual or computed position of the aircraft and also the marked height at a second position a predetermined distance in advance along the aircraft course. As shown, a conventional strip map 1 showing the course to be followed is driven at a speed in accordance with computed ground speed and direction as derived from a standard navigational aid, the aircraft position being denoted by the crossing point of wires 2, 3. A map 6, driven in synchronism with the map 1, has marked on it the ground height along the course to be taken by the aircraft and this height is continuously sensed at a position 9, corresponding to the present position of the aircraft and at a further position 11 corresponding to a position which will be reached by the aircraft at a known time in the future. As shown, the map 6 is marked by a silver image of a density corresponding to the ground height and light units are stationed at the positions 9, 11, the light being directed through the map to affect photo-cells placed at the other side whereby voltages are generated corresponding to the height at which the aircraft should be flying both at the present time and at the known time in the future, Fig. 2 (not shown), and these heights may be indicated on meters. Thus by comparing these heights with the height recorded by a pressure altimeter-the pilot may determine any necessary action. In a modification, the map 6 comprises a magnetic tape. To enable the apparatus to be linked to an automatic pilot a belt 13 with pins 14 extends between the positions 9, 11 and is driven in synchronism with the maps 1, 6. The pins are adjustably mounted in the belt by spring clamps 22 so that their height above the belt may be varied, this adjustment being performed by a cam 21 situated at the position 11 and rotated on a shaft 20 driven through an angle corresponding to the output of the photo-cell responsive to the light unit at that position. In the vicinity of the cam 21 a fixed cam 23 opens the clamp' 22 to enable a roller 24 biased by springs 25 to set the pin 14 against the surface of cam 21 whereby each pin 14 is set in turn to extend above the belt by an amount corresponding to the height at which the aircraft should fly at the position 11. An arm 26 pivoted at the lefthand end of the row of pins corresponding to the present position of the aircraft, Fig. 4, is biased against the pins whereby the angle of the arm as determined by an angle measuring device 27 shows the angle at which the aircraft should fly in the immediate future. In the control circuit, Fig. 5, signals from the pressure altimeter 28 and photo-cell 16 associated with the light unit at position 9 are fed to a comparator 31 the output from 3] being fed to an adder 34 which also receives signals from the angle measurer 27, the output from 34 being fed directly to an automatic pilot. The apparatus may also be used to enable an aircraft to make a blind approach to an airfield by marking on the map 6 the height which the aircraft must follow.