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Aviation History
1947
1947 - 0084.PDF
FLIG HI JANUARY IOTH, 1947 Ingenious New Calculator The Watts B«B. Computor Described : An Alkin-One Instrument for Air Navigation : " Stretchable" Scale for Corrections THE Watts Computor is a newd.r. instrument employing thevector system of computation for air navigation. It has been de- signed to simplify and speed up cal- culation for location-finding prior to and during flight, and to increase the accuracy of these calculations. With it, and a standard flying map, may be calculated the degree of track, course and ground-speed, the distance along any track on standard topo- graphical maps and mercator charts, the time required for distance, true airspeed with change of tempera- ture and/or height, as well as the conversion of knots and kilometres and the plotting of a radio bearing. It is light, being mainly of plastic, and small enough to slip into a pocket. Basically, the computor consists of a rigid base-bar of transparent and opaque plastic having fixed and elastic scales, with, pivoted to it, a transparent plastic bar, also scaled, having a circular head in the centre of which is pivoted a rotating circu- lar dial and a straight " wind-bar." These parts are moved in relation to solve the vector triangle, formed by the lower edge of the top scale on the base-bar, the centre-line of the pivot-bar and the scale of velocities on the wind-bar. The rigid base-bar is like a slide- rule and is fitted with a cursor. On the top and bottom of the front surface are provided two On the back surface of the bar are different scales for corrections and con- versions. On the top half is a scale with arrows for nautical miles and kilometres, the rubber carrying a corresponding scale with an arrow for statute miles, while on the lower half are scales for height and temperature corrections of indicated airspeed, with corresponding arrows and temperature graduations on the rubber scale. . Pivoted at zero on the base-bar, and sliding longitudinally in relation to it, is the oivot-bar. This is a transparent diametrically opposed to the arrow is an index mark, also red, both being on the centre-line of the pivot-bar. The pivot-bar slides longitudinally in relation to the base-bar along its" centre slot, and can be removed easily from the base-bar by an upward pull on the pivot-knob. Attached at this point, and between the two bars, is a flat piece of transparent plastic carrying a red arrow. The accuracy of all scales is con- stant for all except those on the rubber band, and any inaccuracy on this is RED INDEX ARROW ^•1 T I DRfFT'SCALE CORRECTION SCALEFOR MERCATOR CHART z_ BASEBAR' scales in statute miles, and on the left is a drift scale which is struck from the centre of the pivot. Recessed be- tween the upper and lower scales, and protected by transparent plastic, is a '' stretchable '' scale anchored at the zero point, its other end carried on a roller in a housing attached to the bar. The roller is rotated by a knurled knob and has a ratchet by which the scale is held in any position to which it is adjusted. The rubber scale is pro- vided with a ground-speed indicator, with minutes scales working in con- junction with the upper and lower scales on the rigid part of the bar, and with a scale of correction for mer- cator charts. ruler with a circular head and a slot cut along the centre-line, along which is engraved a scale 1:2,000,000. Set in the circular head and pivoted in the centre is a circular dial with a 360-deg graduation. Also attached at this point is a wind-bar graduated with a scale 6f wind velocities, starting at the pivot of the wind-bar and extending along a projecting portion which is used as a lever to rotate the dial" a small knob on the circular head locks the dial to the fixed head and enables the wind-bar to be moved indepen- dently. A true index is graduated on the fixed head, extending to plus and minus 30 deg either side of zero, which is. marked with a red arrow, while Front and rear views of the Watts B.B. Computor. The shaded area in the centre of the "base-bar" is the flexible correction scale. very easily determined and, if necessary, the band can be replaced. The life is estimated to be about two years. The following few examples are given as illustrations in methods of use, to emphasize the^fect that probi-Jj lems can be solved by this instrument very quickly. Flying from "A" to " B " : — .;•' Given:—T.A.S.: 175 m.p.h. ._.: Wind: 330 deg at 25 m.p.h. Track: 39 deg. Distance : iqo st. miles. -v Required:—Drift. -; True course. •;? Ground speed. s Flying time. J The circular dial is rotated by tire wind-bar and 39 deg (track) set against the red arrow at " O" on tb$
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