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Aviation History
1938
1938 - 0367.PDF
FEBRUARY IO, 1938. FLIGHT. STILL SIMPLER D/R The Operation of the Dalton Model G Computer Described : One-Handed Accuracy EVER since my ab initio attempts at air navigationtwenty years years ago I have lived in the hope thatone day some heaven-sent genius would devote a part of his time to producing, the ideal course and distance calculator (C.D.C. to you). During those (too many) years I have handled many types of calcula- tors, but they all possess numerous and varied drawbacks. Some attain near-perfection in certain directions, but only at the expense of serious imperfections in others. Some require at least three or four hands for their manipulation, while others would have required an extra cockpit in the aircraft to accommodate them. Some were so complicated that the rules of chess were simple by comparison. One at least cost (but not to me) £50. Some . . . but need I continue ? You know them as well as, or better than, I do. Whatever disadvantages they may have, most have one disadvantage in common. They are either difficult or im- possible to use in the air, the one place where they are really wanted. Above all, they are all nearly impossible for use in the air by the pilot-navigator because they cannot be manipu- lated with one hand. Very few machines will stay on an even keel in bad weather whilst the pilot leaves the controls to wrestle with the usual C.D.C. This great disadvantage has been overcome by Mr. Philip Dalton, of the U.S.A., with his "Model G. Dead Reckoning Computer." I have been the proud possessor of one of these ingenious instruments for a week, and if I were a film critic I would certainly award it * * * *. [The Dalton Mark VII Computer was described in last werk's issue.—ED.] Simple, Quick and Accurate I have certain minor criticisms to offer, but they are more than outweighed by my appreciation of this instrument's good qualities. It is robust, and at the same time light and com- pact, simple, quick and accurate to use in the solution of the various problems encountered in dead reckoning air navigation, and, above all, the most difficult problems can be solved both on the ground and in the air bjr the use of one hand only. To those navigators who have anxiously wrestled with "inter- ception " problems it seems almost impossible that these can be solved by two or three pencil marks on the face of the instrument together with the manipulation of two operative knobs, all done with one hand (and nothing up the sleeve). The instrument consists of a flat box 5111. wide by Gin. long and iin. thick, with a hinged cover on top and two operative knobs on the right-hand side. Two leather straps enable the instrument to be fastened to the operator's leg above the knee. As an alternative the straps can be removed and the instrument permanently installed in some suitable position in the machine. On the instrument cover is a circular "time and distance" slide-rule, and when this cover is hinged back a note pad 133 Commercial Aviation Fig. 1.—The Model G Dalton Computer with case closed, showing the time-and-distance calculator. At the side are the operating knobs for the "compass ring" and "polar co-ordinate " chart inside. fastened to its under-side is made available and the face of the wind calculator is exposed. This consists of a transparent plotting disc mounted on a rotatable "compass" ring, i.e., a ring engraved 0-3600 at i° intervals, which is rotated by one of the operating knobs (A in Fig. 1). Underneath the trans- parent disc is a section of a "polar co-ordinate" chart, in the form of an endless belt mounted on rollers. This simple device has overcome the bugbear of all C.D.C. designers—how to obtain a reasonably large scale and at the same time to keep the size of the instrument within reasonable bounds. This scale covers speeds of 30 to 290 m.p.h. (or knots). This chari is moved up or down by means of the other operating knob (B in Fig. 1). Above the compass ring is a "True Heading Index" on which is engraved a scale 45°-o°-45° (at i° intervals) with a lubber mark in the centre. This scale can be used to apply the magnetic variation, and thus entirely eliminates the necessity of dealing with true courses. This scale is also used to apply drift angles in order to read the track, etc. Space will not permit a full description of the methods of solving all the possible navigation problems by this instrument, but the following three problems, together with a description of the solution, will serve to show that my rather extravagant praise is fully justified. Note: Figures are given in the three problems to allow Fig. 2 Fig 3- Fi&- 4 Three demonstration problems, worked out in the accompanying description.
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