STARS AND AVIATORS

Otago Daily Times, Issue 23335, 29 October 1937, Page 20

STARS AND AVIATORS

THE AIR ALMANAC

(From Our Own Correspondent) (By Air Mail) . . LONDON, Oct. 6.

Astronomical navigation is being increasingly used-as the ranges of aircraft are extended and as ocean flying becomes more common. In recognition of this trend the Nautical Almanac Office has undertaken the computation of "The Air Almanac," and the first compilation has been issued, as an official Air Ministry publication. It is arranged in two parts, one designed to have a certain permanence and to be replaced at intervals of two, three, or four years, the other being ephemeral and containing the astronomical data for the dates given. This part will be issued at first quarterly, later biannually, and, finally, annually. The first issue covers the period from October 1 to December 31. The almanac is being issued to all Royal Air Force bomber and general reconnaissance squadrons as well t as to appropriate service headquarters, schools, and libraries. ... ■ ; - • , Hitherto, the air navigator has had to adapt the Nautical Almanac to his particular needs, and the Air Almanac is designed to fit those needs more pxactly, so as to save time and trouble during flight. One difference between the two almanacs is that the nautical one shows the variations of the stars in hours, minutes, and seconds, while the air one shows them in degrees and minutes of an arc. This difference saves some of the processes of calculation. The book itself is bound between stiff board covers in blue, and the ephemeral sheets are punched so as to be easily attached to the loose hinge of the cover. Royal Air Force officers have been ordered to regard the present form of the almanac as experimental and to send to the Air Ministry any suggestions they may have for its improvement. , ' USE OF RADIO

The increasing prominence ,of astronomical methods in air navigation is a reminder of the progress that has been made in long-range air travel. Present-day flying-boats, like those or the Short Empire class which have been making the experimental Atlantic flights, must to some extent -be 'selfcontained in their navigational methods and must not have to rely upon outside aids. And this will-apply with yet greater force .to the larger flying boats now being built. . ■■ .• In this self-containe#«avigatjon a great change has since the parly days of flying. Jfhe pioneers followed railway linesfpi England and roads on the Continent. Without either railway line or road, the air pilot of that time was usually lost in every sense of the word. But with the increase in the trustworthiness and range of aeroplanes and in the accuracy of instruments, "Bradshaw." as following the railway lines was called, was abandoned in favour of dead reckoning, or the combined use of calculation, compass, and clock. The first step towards genuine navigation, as apart from map reading, had been taken. But it was a small step, for the success of dead reckoning depends, in the intervals between the opportunities for drift observations, upon constant conditions, and, therefore, as flight times increased, the risks of inaccuracy became greater. "Blind" flying, the habitual overweather flying of the commercial air lines, and finally ocean flying over the Atlantic, demanded more certain methods. The final result has been the full system of aerial navigation and the use of radio. Some predict that radio will eventually oust all other navigational aids, but at present it seems that self-contained methods which can be practised by the crew of the aircraft armed with the appropriate instruments and astronomical tables, and without outside help, are essential to long-distance commercial aircraft operation.