Patent GB-590771-A (GB)
Title: Improvements in and relating to apparatus for course steering on aircraft
IPC: G01C21/20
Filed: 1942-12-15
Abstract: 590,771. Course-recording apparatus for aircraft. MAY, W. J. Dec. 15, 1942, Nos. 17784/42 and 1906/43. [Class 97 (ii)] Relates to improvements in the bomb sighting and course steering or recording apparatus described in Specifications 145,810, [Class 97 (ii)], and 542,792, [Group XIX]. As shown, the apparatus includes the vector triangle comprising the airspeed bar, wind-speed bar 30 and ground-speed bar 8 carried by a disc 5 operated by the knob 6 which also operates the air- and windspeed bars, the disc 5 being mounted concentrically above a relatively fixed disc 4. The orientation of the groundspeed bar 8 causes a similar orientation of a bar 9 mounted above the course-marked disc 7a which in this case is mounted on the casing A away from the disc 5 and is rotated in coincidence with the shaft operated by the shaft 24 of the knob 6. The marking style 37 marks the course on the map or chart by being traversed along the rod 9 by a slide operated at a speed appropriate to the ground speed by a motor 53, alteration of the ground speed effecting an alteration of the motor speed by means of an electric resistance on the end of the bar 8 being affected by the length of the bar'8. The rod 9 is carried by U-shaped end members 41 having electromagnets 56, Fig. 3, whereby the members 41 are normally held against the metal face of the course marked disc 7a permitting the style 37 to traverse the rod to mark the course. If the knob is operated to alter the vector triangle' and consequently the orientation of the bar 8 in accordance with a new bearing of the aircraft, the electromagnets 56 are automatically deenergized and an electromagnet 57 on the style 37 is energized so that the rod 9 is permitted to be oriented on the course marked disc 7a about the style 37 as a centre, which style in traversing the bar marks the new bearing on the chart. As shown for night work, a starmarked disc 61 having months and days marked on its periphery is driven by clockwork and rotates once every 24 hours above a disc 70, having longitude graduations 71 on its periphery against which is aligned a clip 72 adjustable around the table carrying the star chart 61, the clip being set to the appropriate day before being aligned with the appropriate longitude. The zero longitude marked by an arrow 74 is set opposite the time of the day graduation so that the star chart now revolves according to the time of the day so that it is always oriented correctly with the heavens. A mask 75 is mounted above the star chart so as to expose that area of the star chart which would be visible if the north star were the zenith. The mask 75 is mounted on transverse guide rods 76 so that it can be adjusted according to latitude. In addition, a pointer 84 located above a repeater compass 85 rotates in sympathy with the driven disc 5 of the bomb sight and course steering apparatus and also the course chart so that the pilot steers a course in which the north on the usual oscillating disc of the'compass 85 is indicated under the pointer 84. A calculating device is provided to enable measurements of time and distance to be ascertained by the navigator and comprises a window 89, Fig. 1, in the casing having a fixed strip 90 graduated in units of time and opposite to it an adjustable strip 91 graduated in hours of the day and suitable subdivisions thereof. Parallel bars 98 carry tension wires 97 which may be seen through the window and means for moving the bars by a knob 96 along an arcuate slot to indicate different ground speeds. The varying distance between successive wires 97 is regarded as a function of a distance of travel so that the time of travel of any distance at any selected ground speed will be indicated against the appropriate wire or wires as also will the time the journey should be completed. Specification 560,706 also is referred to.