VOYAGING BY AIR

Otago Daily Times, Issue 17636, 28 May 1919, Page 8

VOYAGING BY AIR

THE WEATHER FACTOR. Now that private enterprise is to have full scope in aerial traffic, as in other natters, it -will be opportune to review the effect which weather conditions are likely to exert upon the progress of this new means of transport. Although we are told by experts in aviation that it will not be long before there will be an hourly service of passen-ger-carrying aircraft between London and I ans, and when in need of a change we can ny off do Norway or spend the weekend in Cairo, the weather will still be the factor in .all aerial travel. There has been much said lately about . usefulness of the Zeppelin, type of airship m peace time, as now that there is no possibility of such a vessel bein* attacked by an enemy it will be perfectly immune from accident. That this is a fallacy is shown by the number of accidents that have occurred to vessels - of this class from meteorological conditions alone. A ZeppeHn was wrecked some years ago by a storm in the Black Forest, and It the beginning of the war two more met with a similar fate off the coast of Jutland. There seems to bo little doubt that in the long run it will be the heavier-than-air machine that will be found best to combat the varying weather conditions met with in a prolonged flight. — Testing Air Currents.— It is a well-known experience of air pilots to leave the ground in a calm and at a height of about 1000 ft to find a 40-roile-an-hour gale blowing. Another ex•erietiee_ may be that at a. comparatively low altitude the wind may be blowing in exactly the opposite direction to that of the surface wind. During the last 20 years the Meteorological Office has used kites, balloons, ballon-sondes, and pilot-balloons; for the study of ,the upper air. By means of the ballons-sondes the temperature of the air up to a height of 22 miles above the earth's surface has been determined, while the pilot-balloon' has enabled observers to note the direction and velocity of the wind, when there were no clouds, available for the purpose, up to a height of six iriiles. These are now in use every day for the guidance of aircraft pilots. With regard to kites and ordinary balloons, they have enabled observations of wind temperature, and humidity to bt taken'up to a height of 10,000 ft. 'The results of these continuous observations point to the fact that our local weather is manufactured " so to speak, at a very Mgh level-. the atmosphere. It remains to be found out if possible what causes tie changes in air _ pressure in the "stratosphere," or region of unchanging temperature,, and. what exactly produces the «ondtt,iona which express themselves to us in clouds, ' rain, snow, ..or hail. It would: appear that this will require the greatest ingenuity in carrying out and ample intellectual equipment for their subsequent study. — Conquering the Weather.— Vast strides have already been mad© by airmen in conquest of their chief enemy —tiie weather.' In the Globe of November 27, 1918, there'appeared 'a paragraph giving the experience of 18 passengers in two aeroplanes which landed in a dense fog. It seems that after crossing the and visiting the Independent Air Force Headquarters in France, th6y returned to London.- They , crossed the Channel again, amd made their way through Kent in fair weather, but on rtearing London ran into a fog. They were due to arrive at 4.30 p-m., and some anxiety was felt about that time as to their safety. But the pilots, who made tljis journey several times a week, with the aid of compasses, "felt" . their way through the fog, and at 4.35 their machines were heard approaching. Within the nett five minutes a perfect landing was made at the spot from which they had started, and within a few seconds of each other, about 300 ft 'apart. So far as the comfort of passengers is concerned, the weather seems likely soon, to become a negligible factor, as aircraft made for the purpose of carrying persona from one place to another will have absolutely enclosed cars, being quite proof against any meteorological conditions which may prevail on the journey. Their safety will further be ensured by duplicate sets of engines running quite independently I of one another, so that in case of a breakdown repairs can be executed en route. If through some unforeseen contingency the craft is forced to descend while over the ocean by means of floats it will rest comfortably on the surface of the sea-for several hours until picked ut> by some passing steamer. This is the theory; but an aircraft forced to descend in mid-Atlantic in a storm would experience an extremely rough time. — Where the Germans Led.— That the Germans very early recognised the great importance of meteorological ob- , serrations in the upper atmosphere in connection with aviation is shown by the steps taken by their scientists early in the war, for on August 20, 1914, they set up a "Field Weather Station" in the neighbourhood of Brussels, where continuous observations at six-hour intervals were taken by four meteorologists, who filled small indkrubber balloons with hydrogen under pressure. These balloons were launched and "followed" with a iheoflolite. By also observing the same balloon with, another' theodolite from a different point they were able to obtain useful idras about tha direction and force of the wind in the upper air. During the hours of darkness someyhat larger balloons were used' carrying an electric pocket lamp, and so forming an artificial star quite easily seen. They telegraphed the information thug collated with Dutch and Scandinavian observations, and thus became expert *in forecasting suitable weather for possible air raids. Somewhat more tardily our own Meteorological Office also recognised the fact that predictions of weather were helpful to enemy airmen, and on April 27, 1915, an announcement appeared in the press as follows: —"The Meteorological Office announces that from May 1 weather forecasts for the several districts of the British Isles will not be issued to newspapers." From almost the beginning of the war wind directions were not published, and it was no doubt partly to these precautions that the • disasters to the Zeppelins already mentioned were at anyrate m part due. —Some Remarkable Fads.— We have seen the importance of the weather in connection with the science of aeronautics, and its practical application to aerial traffic. A few of the best-known results of the researches of the meteorologist in this direction may now bo referred to. Temperature falls about lOdeg F. for evmy kilometre up to the height erf 10 kilometres. Here is the isothermal layer, or region where temperature remains almost the same throughout up.to 37 kilometres. The height of the barometer also affects the aviator, as according to this so does' the density of the air vary—m other words, the weight of the atmosphere; and according as this changes so does the lift exerted on the wings of an aeroplane. This factor also affects the running of tha engine and the speed indicator* An aeroplane is not so greatly affected by wind force as would at first appear, as when once the machine has left the ground it is immaterial from which quarter, or with what force the wind mary blow. It was fairly safe to infer, however, that at a height of a few thousand feet the wind would roughly have twice the speed as at ground-level, and have veered a few points in direction. Taking everything into consideration, it would seem that soon meteorology will be an essential study for arr-jalots, 'as it has already quite recently become for ship's officers in the merchant service.