SAFETY IN FLYING

Hawke's Bay Tribune, Volume XXIV, Issue 94, 4 April 1934, Page 5

SAFETY IN FLYING

• « Effects of Topography INFLUENCE. OF WINDS Safety in flying, says ‘‘Airman,” in the Sydney ‘‘Morning Herald,” has been tho aim of all interested in aeronautics since the Wright brothers demonstrated the possibilities of the aeroplane at the beginning of this century. Since the Great War, aeronautical experts have been attacking, with increased vigour, the multitudinous problems attached to aviation. In recent years, with the develop- I ment of high speeds and the universal use of aircraft for commercial purposes, the influence of topographical and meteorological disturbances has become of almost paramount importance to the safety of the machines. It is significant that in the British Air Minslry’s estimates for 1933 provision has been made for the opening of a nieteorolog - cal station at Manchester civil aerodrome, whereas cuts have been made in other directions. Topographical effects are localised, every country having its own peculiar set of conditions. Aware of this, extensive research and investigation have been carried out by aeronautical experts in practically every country in the world. Professor. W. Georgii and H. von Ficker, of Germany, Idrae of France, Sir Napier Shaw of England, and Richard V. Rhode of the United States of America, and numerous others have carried out extensive investigations on .the effect of topography upon wind distribution in tho neighbourhood of obstacles, and, .in some cases, the loads induced in aircraft in the neighbourhood of these obstacles. In regard to the actual effects of loads induced in aircraft owing to air disturbances, an Australian) investigator, Mr T. D. J. Leech, lecturer in civil engineering at Sydney University, ha s anticipated tho work of the European and American authorities by some three years. In 1925, Mr Leech conducted mathematical and experimental investigations, and established a formula which has since been established and proved independently by the other research workers, the results of whose investigations in this direction have only just reached Australia. A paper on Mr Leech’s investigations has been published in the official journal of the Institution of Engineers, Australia. Mr Leech has made a number of calculations, based upon experiments, into the probable loads experienced by the aeroplane which featured in the accident at Myocum, north of Lismore, on September 18, 1932. The investigations and calculations indicated that owing tr topographical influences, the wind was deflected upwards, and that the aeroplane flew into this region where it could possibly experience loads for which it was not designed. The results of similar calculations have been compared with those of a machine of another type flying in the same district, where actual measurements were taken, and a very close agreement between th two eases bad been found. This afforded evidence of the validity of the calculations in connection with the machine which featured in the accident. It has been found, assuming that the air speed, before the accident, was between a cruising speed of the aeroplane (105 miles per hour) and its top speed (127 miles per hour), that the load on the machine at the point where structural failure commenced, might readily be between 3.7 and 4.2 times the normal load in calm air. The British Air Ministry specifications for normal civil aircraft called for a breaking load of four times the load on the wings in horizontal high speed flight. If the machine as loaded in this flight was in the normal category it would be seen that, the most probable load experienced would exceed the designed breaking load. This fact brought out into relief the conclusion that flying conditions in Australia were very much more severe than those in England, for the Air Ministry specifications bad, according to reports, been found satisfactory in England. There was ample technical evidence to support the existence of unfavourable conditions in Australia. The summary of the calculations is shown in a chart, where points within the curved shaded band indicate the range of loads that would be experienced by aeroplanes of the types for which calculations were made, flying at varying heights above the ridge at Myocum, for weather conditions similar I to those on the day of tho accident. Further evidence of tho peculiar conditions which may be experienced was ' given quite recently by observations i made in a large aeroplane flying in this vicinilv On crossing ’he range. th" i mucliii,,. sudden!' i n’ghl in a

downward air current and it was estimated that the load induced on the machine was at least five times the normal load in calm air. The great lesson to be learnt from these provisional investigations is that flying over hills and ridges at low altitudes in ba,] weather is attended by a serious risk of structural failure. A reasonable safe rule can be deduced from a study of Ihe 'chart mentioned, namely, that, the flight path of an aeroplane over hills and ridges during periods of high winds should be at an altitude which is greater than twice the heighi nf the hills or ridges above the menu Ic'd of the surrounding country.