Patent GB-1206694-A (GB)
Title: Navigation director system
Inventor: RICHARDSON DONALD WILFRED
IPC: G01C21/22
Filed: 1969-04-28
Abstract: 1,206,694. Navigation: indicating apparatus. HUGHES AIRCRAFT CO. April 28, 1969, No.21499/69. Headings G1F and G1J. A navigation system for displaying data useful in the navigation of a craft along a particular route comprises a plurality of navigation maps covering the route stored on a film in the form of frames each covering a particular area and overlapping with adjacent maps, information relating to each map and the co-ordinates of its centre point being coded on the film adjacent the map, means for setting the co-ordinates of a start point and at least a first destination point into a computer which then computes a great circle route between the two points, which is then displayed as a line 26 on the face of a display unit 20, the computer also being responsive to supplied navigation signals from a compass controlling the altitude of an aircraft symbol 28 in relation to a compass rose 70 to indicate heading, and to signals received from radio stations such as VORTAC stations to compute craft positions which is then displayed as a point 30 at the centre of the display unit a portion of the desired map (outlined by lines 15) being optically projected on to the face of the unit 20 and being moved so that the point 30 indicates the correct craft position, and the crafts off route error being indicated by displacement of the line 26 from the centre point 30. Selection and change of the maps is effected manually by the pilot by setting of a code number corresponding to the desired map in a control unit. The line 26 is provided with a middle part 32 acting as a vernier deviation indicator which exaggerates the crafts off route error by movement an integral number of times greater than the movement of the line 26, when the craft is on course the lines 26, 32 form a single straight line passing through the point 30. Provision is also made for the system to operate in a north-up or a breaking-up mode as selected by a switch 72. In the north-up mode indicated the compass rose 70 remains stationary as shown and the aircraft symbol 28 and an associated aircraft heading pointer 380 are rotated to indicate craft heading, whereas in the breaking-up mode the symbol 28 remains stationary, and the compass rose is rotated in accordance with signals received from the computer. In use the craft pilot first selects the map on which the known start point is located and this map will be projected on to the face of the unit 20 with the co-ordinates if its centre point at the point 30. Manual controls are provided by means of which the pilot can then move this map to locate the start point on the map at the point 30 and the co-ordinates of this point are then stored in the computer. This process is repeated with the desired destination point and further destination points may also be set the computer substituting each destination point as it is reached for the start point and then computing a route to the next destination point. The route indicator line 26 and associated line 32 are then projected on to the display unit 20 to indicate the computed circle route. During flight as a result of received VORTAC signals and from the craft compass the point 30 continuously indicates craft position on the map and the symbol 28 and pointer 380 the craft heading. Off-course error is indicated by displacement of the line 26 and is command heading symbol 68 controlled by the computer indicates the desired heading of the craft to return it to the desired route. The computer also computes wind speed, so that in the event that VORTAC stations cannot be received the position of the craft can be found by dead reckoning from wind speed and air speed values. When this occurs a plaque 86 is illuminated on the unit 20. If the craft position is such that it is off the edge of the map in use then a plaque 24 is illuminated warning that the map should be changed. During this time the lines 26, 32 and the symbol 28 are not projected on to or illuminated in the unit 20. A readout panel 84 in conjunction with a multiposition switch 82 can be used to indicate ground speed, estimated time en route and distance from destination as desired, and a flashing lamp (not shown) is illuminated when the craft is five minutes from its destination. At one minute from the destination the line 26 also flashes. Provision is also made in the computer for flying along routes 3, 5 and 10 miles displaced to left or right of and parallel to the computed route for use in congested traffic lanes. The optical map projection system is more clearly described in Specification 1,206,691 and the projection system for the lines 26, 32 in Specification 1,206,692. The processes carried out by the computer and the programming thereof are described in some detail in the Specification.