FLYING HAZARDS

Evening Post, Volume CXXIII, Issue 124, 27 May 1937, Page 10

FLYING HAZARDS

DUE TO WEATHER

WIND, CLOUD, AND FOG

AVIATION IN N.Z,

Flying conditions in New Zealand, and the general effect of the Dominion's weather on flying, were described by Dr. M. A. F. Barnett last night in the course of a lecture on meteorology in connection with aviation, to a meeting of the Wellington Philosophical Society. The atmosphere in New Zealand, he said, was exceptionally clear, with the consequence that visibility was generally considerably better than that experienced in Europe, for instance; but the topographical layout of New Zealand had an important and in some respects an adverse, effect on the climate as it affects aviation.

' "The fact that' New Zealand is a I relatively long and narrow country traversed by a high mountain chain rather cramps the flying room, available and makes the part played. by! low cloud a very important one. 'Fur-: ther. the mountain chain has a very marked effect on the distribution of pressures and the velocity and direction of the wind. Not only are conditions bumpy on the lee side of the mountains, but rapid pressure changes, under certain conditions, make altimeter readings unreliable, and unexpected changes in the direction and speed of the wind, both horizontally and vertically, may of ten be experienced. These facts must always make blind flying in New Zealand more diffi-cult-and dangerous than in many other countries. Special aids such as radio direction finders will reduce these hazards, but the mountainous nature of the country must always remain a formidable handicap/ "Strong winds, in themselves, do not constitut- any special danger to a machine in the air. An, aeroplane moves at a certain definite speed relative to the air through which it flies, so that a steady wind simply modifies the velocity of the machine relative to the ground. A steady wind may, in fact, be just as often an advantage as a disadvantage. However, a wind is very seldom steady, arid strong winds in the lee: side of our mountains can be extremely turbulent. This, of course, gives rise to excessive, bumpiness, and may make smooth landings at unfav-1 ourably plaqed aerodromes extremely difficult or impossible. While not causing any danger of actual failure, severe bu.npiness places a considerable mechanical strain on the framework of an aeroplane* and must represent an important factor in the general wear and tear. Violent bumpiness is also very uncomfortable for the passengers. AVOIDING THE CLOUDS. "When low cloud envelops the mountains, a pilot may often be faced with ith-: alternative either of abandoning his flight (or taking a different1 low-level route) or of rising thfough the cloud layer arid flying above it. Should he know.that, at a point nearer his destination, the cloud becomes broken so that he can pick tip landmarks below, the ■latter alternative is usually the obvious one. If, however, the cloud sheet extends unbroken over the point at. which h? has to land, the problem takes on a different complexion. The wind above a cloud layer may often differ in both direction and strength from that below, and unless some radio aid is available, a pilot may be carried a considerable distance off his course. If s the cloud is low and the aerodrome not far from hills there is obviously considerable risk involved in coming down again through it. Apart from other considerations, however, there is a peculiar satisfaction in leaving an aerodrome in dull and overcast conditions, perhaps with. rain, and rising through a cloud layer into brilliant sunshine. Furthermore, many cloud formations are extremely beautiful when viewed from an aeroplane. DANGERS OF FOG. Fog, said Dr. Barnett, was one of the most serious obstacles in flying. When thick fog enveloped an aerodrome it was impossible for an aeroplane to make a safe approach and landing, and widespread fog could present very serious dangers to flying, and in many cases was the cause of delays or the actual postponement of a journey. The suggestion had been made that some means should be devised for dispersing the fog above an aerodrome. While the dispersion or precipitation of fog on a small scale was by no means an impossibility, the enormous amount of fog-saturated air which, would have to be dealt with to keep an aerodrome clear was evidently not appreciated. There was not only the fog immediately over the aerodrome to be removed, but new fog which would all the time be drifting in from the sides. A solution of the fog difficulty did not appear to lie in the direction of some dispersing device, but rather in the perfection of radio aids in the form of short-wave wireless beams by which a pilot can be directed very accurately along the required course. Fortunately fogs were not so prevalent in New Zealand as they were at many aerodromes in other parts of the world, but they formed, nevertheless, one of the more serious sources of interruption to regular flying. Rain, apart from the reduced visibility, . was not in itself a particular hindrance to flying, but hail, especially if the hailstones were large, might be a very real danger. Severe thunderstorms might form a real menace. They were accompanied by exceptionally strong vertical air currents and often by \jiail, while electrical discharges made it impossible or dangerous to use the wireless equipment, and might even disable it completely. Furthermore, a lightning stroke might upset a magnetic compass. ■ . ICE FORMATION. The final serious hazard in flying mentioned by Dr. Barnett was the formation of ice on an aeroplane. "Here again we are fortunate in New Zealand," he remarked, "in that our meteorological conditions are such that serious ice accretion can generally be avoided. • In some, countries it has been the cause of a number of accidents. When flying in cloud or rain where the temperature is slightly below freezing point, very large accumulations of ice sometimes form on the wings, and interfere with their aerodynamic properties to such an extent that control of the aeroplane cannot be maintained. If the adverse conditions persist to low levels, a forced landing may become inevitable. Generally, however, ice formation can be avoided by flying either above or below the critical layer. Various devices have been suggested for preventing the formation of ice on an aeroplane, such as heating the wings or treating them with some chemical, but no really satisfactory solution of the difficulty has yet been found."