HEIGHT IN FLYING.

Wanganui Chronicle, Volume LXVI, Issue 17571, 15 May 1919, Page 5

HEIGHT IN FLYING.

By Lieut. William A. Robson; R.A.F

(British), Author or "Aircraft in War and Peace."

LONDON, Jan. 16

Learned mathematicians discourse obscurely on the fourth Dimension; hnd nobody takes much notice of them. But with the coming of aviation the world nas suddenly awakened to the fact that the Third Dimension, of which we all learn a little* and forget a good deal more, has become a factor which to a larger extent governs the life and safety of almost all the European nations. .

For the question of height is one of supreme importance m aerial warfare ; and on the solution of the variouß problems connected with it depended the success or failure of the blows that the Aliies struck at Germany from above, and the effectiveness of the defences which were planned to repel the air raiders. who attacked Great Britain.

Many people are unaware of the factor that determines the height reached by aircraft. Rarity of the atmospheric air is the factor. The higher one goes the thinner becomes the air, until at about 25,Cv/o'feet (near1/ 5 miles) it "fi *o rarefied that ther cis hardly sufficient "body" in it to support the planes of an aeroplane. For it miist bo remembered that, although it is invisible, air supports a Hying machine in almost1, the; same way as water buoys up a ship. No contrivance could tje maintained aloft in a vacuum.

The greatest altitude to-which a machine can ascend is termed its "absoli to ceiling, and it 4 s significant to note so great are the difficulties to be overcome' in the vpper regions, that no higher flights have been made since the commencement of the War, with a few trifling exceptions, than were carried out in the summer of 1914. (Tfeia was written just before' the six mile high flight illustrated in "The Weekly Press" of April 2nd ) . The records for altitude were hpld for a iong time by German pilots, and remained unbeaten until comparatively recently. Altitude alone, however, is o? little importance in air warfare. What ts wanted is a fast rate of climb, anil 1; is in this direction that the most remarkable developments have taken piace. An aeroplane that could ascend to 30,000 feet would possess but small military value if it were going t.O take all day doing so. It would not be nearly -•I useful as a machine capable of rising only to 20,000 feet, but of doing it >n half the time. Tins argument, however only holds good within certain limits. Most aerial work over the lines was carried out towards the end of the War "t a height or round about 15,000 feet— as compared to 3000 feet at the beginning of the War—because at this altitude an aircraft, although not actually out of range of anti-aircraft gunfire, ?s pii exceedingly difficult target. Every service machine must, therefore fa able to make at least this height as a first consideration.

As almost any modem machine can put up a reasonably good performance up to 10,000 feetj it is between the heights of 10,000 and 20,000 that climbing power is most vitally needed, and proves most effective. A machine which goes up like a rocket to 5000 feet in 3 minutes, but takes 18 minute* io get to 15,000 feet is not so usef'il as one that, though tlimbing slower : t the start, has a f>t-eadier average an<l v akes 15,000 feet in 15 minutes. An J here we come to quite another factor ; namely, level flying at great heights. For the higher an aeroplane or airship ascends the slower becomes its forward. sp«ad.

This arises from the fact that the engine is giving less power, the reason again being paucity of the atmosphere. The mot.:ve power of all present-day aircraft is the internal-combustion petrol engine; and the petrol motor must \\j fed with a. mixture of petrol vapour and air, which is compressed in the cylinder into a highiy inflammable gas find then exploded hi an electric spark. When the flow of air is weak tiie mixture becomes too " rich" and the power the explosion is considerably lessened. Certain British devices have overcome this difficulty in a degree, but the falling off in power is still enormous at