GB581906A - True wind calculator for use on aircraft - Google Patents

Abstract

581,906. Calculating - apparatus. BURT, F. S., and WRIGHT, C. S. July 20, 1943, No. 11822. [Class 106 (i)] A device for use on aircraft for evaluating the speed W and bearing # of the true wind from the equations W Cos # =V (1 - T1/T2) and W (Cos # + Sin #) =V (1 - T1/T3), where V is true air speed and T1, T2 and T3 are times determined by the known four-point bearing method comprises relatively movable elements graduated logarithmically and trigonometrically. As shown in Fig. 3, the calculating element comprises an inner scale 1 and a relatively movable outer scale 2 and the trigonometric element is constituted by the scale 4 and a rotatable plate 5. On the plate are sets of grid lines A and B for the values A = V1 (1 - T1/T2) and B=V1 (1 - T1/T3), where V1 =100. A pointer 6 is rotatable about the ceiitre of the plate 5. The scale 1 is for values A and B, the scale 2 is a time scale and scale 4 is for bearing angle. In operation, the time scale 2 is rotated until the value T1 is set against the index on scale 1 and opposite the values T2 and T3 are read the values A and B. Next the plate 5 is rotated until the aircraft's course is set against the index C and the pointer 6 is rotated to the point of intersection of the grid lines corresponding to the A and B values, the pointer showing on the scale 6<1> the wind speed and its direction on the scale 4. If the actual airspeed, say V, differs from V1, the reading on the scale must be V. multiplied by - to give the true wind speed. V1 In the form of the instrument described in the Provisional Specification, the logarithmic scales are arranged on the opposite side to the trigonometry scales and an additional movable scale is provided for the multiplication factor.