VOYAGING BY AIR.

Otago Witness, Issue 3400, 14 May 1919, Page 59

VOYAGING BY AIR.

THE WEATHER FACTOR, Now that private enterprise is to have full scope in aerial trafiic, as in other matters, 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 Paris, and when in need of a change we can fly off co Norway or spend the weekend in Cairo, the weather will still be the predominating factor in all aerial travel. There has been much said lately about the usefulness of the Zeppelin type of airship in peace time, as now that there is no possibility of such a vessel being 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 Zeppelin was wrecked some years ago by a storm in the Black Forest, and at tha beginning of the war two more met with a similar fate off the coast of Jutland. There seems to be 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-milo-an-hour gale blowing. Another experience 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. iij means of the ballons-sondes the temperatui'e 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 miles. 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 high level of the atmosphere. It remains to be found out if possible what causes the changes in air pressure in the "stratosphere," or region of unchanging temperature, and what exactly produces the conditions which express themselves to us in clouds, rain, snow, or hail.

It would appear that this will require the greatest ingenuity in carrying out observations, and ample intellectual equipment for their subsequent study. Conquering the Weather.—

Vast strides have already been made by airmen in conquest of their chief enemy —the 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 Channel and visiting the Independent Air Force Headquarters In France, they returned to London. They crossed the Channel again and made their way through Kent in fair

weather, but on nearing 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 this 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 next five minutes a perfect landing was made at the spot from which they had started, and within a few seconds of each other, about 3Coft 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 persons 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 sete of engines running quite independently 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 uv> 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 observations 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, Avhere continuous observations at six-hour intervals were taken by four meteorologists, who filled small hidiarubber balloons with hydrogen under pressure. These balloons were launched and "followed" with a Hieoctolite. By also observing the same balloon with another theodolite from a different point they were able to obtain useful ideas about the direction and force of the wind in the upper air. During the hours of darkness somewhat larger balloons were used carrying an electric pocket lamp, and so forming an artificial star quite easily seen. They telegraphed the information thus 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 in part due. Some Remarkable' Facts.— 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 be referred to. Temperature falls about lOdeg F. for every kilometre up to the height of 10 kilometres. Here is the isothermal layer, or 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—in 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 the 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 may 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 air-pilots, as it has already quite recently become for ship's officers in the merchant service.