Patent GB-709107-A (GB)
Title: Improvements relating to aircraft navigational computors
Inventor: STEWART JOHN
IPC: G06G3/10
Filed: 1951-02-10
Abstract: 709,107. Calculating-apparatus; indicating- apparatus. FERRANTI, Ltd. April 18, 1952 [Feb. 10, 1951], No. 3305/51. Classes 106 (1) and 106 (4) A navigational computor comprises two vector members mounted to rotate about parallel axes respectively and each carrying a cursor which, together with the angular position of the member, is adjustable by corresponding vector-adjusting means, a linkage joining the cursors arranged to derive the point midway between them, and indicating means for deriving from the position of the said point relative to a reference point midway between the axes of the vector members the components of the means of the two vectors represented in perpendicular reference directions. The apparatus is for use in an aircraft receiving from a responder beacon its range r and bearing # therefrom. The range S and bearing α of the destinat on from the beacon and Ï, the bearing of a predetermined course leading to the destination, are known. The vector members are adjusted to magnitudes S and r and to directions α-Ï and #-Ï + # respectively and it is shown that the components of the mean vector (i.e. half the resultant) represented by the line joining the said points are equal to half the distance of the craft from the destinat on d and half the deviation of the craft from its course x. Normally, the constants for the flight, S, α and Ï are manually set and the variables r and # are automatically and continuously entered. The stud defining the midpoint of the linkage, which may be in the form of a pantograph or lazy tongs, operates two indexes constrained to slide against calibrated scales in the perpendicular reference directions so as continuously to indicate the values d and x and the sense of x. If a remote indication is required or if the apparatus is to be used in an automatic control system, the movement of the indicating point may vary electrical resistances or control other transducers. Suitable means for adjusting one of the vectors, e.g. that of magnitude r, comprises a threaded rod 40 mounted in an arm 43 and driving radially of the arm a nut 47 on which one end of the linkage is pivoted. The magnitude r is set by rotation of an annulus 53 of epicyclic gearing comprising planet wheels 52 and a sun wheel 51 fast with a bevel wheel 50 meshing with a bevel wheel 49 secured to the rod 40. Bevel wheels 60, 61 of a differential gear are set according to 2# and 20 so that the driven shaft 44 on which the arm 43 is mounted is moved according to #-Ï. A sun wheel 54 fast on the shaft 44 forms part of further epicyclic gearing including a fixed annulus 56 and planet wheels 55 carried by the same spider 58 as are the planet wheels 52. Thus when the shaft 44 is rotated, the sun wheel 51 and bevel wheel 50 will rotate with it. In this way the two adjustments are made independently of each other. In an alternative arrangement, the differential gear 60, 61 is replaced by further epicyclic gearing. It is suggested that the apparatus may be used to assist a pilot to fly his craft in an orbit.