SCIENCE OF FLYING

Otago Daily Times, Issue 21784, 25 October 1932, Page 8

SCIENCE OF FLYING

THE SPEED LIMIT

(From Our Own Correspondent.) LONDON, .September 9. An interesting address on the subject of "Speed in Flight" was given by Mr H. E. Wimperis before the British Association. ... The faster a body moved, he said, the more curved was its path, the greater was the amount of the centrifugal force. So, too, in the case of an aeroplane, when it was flying in a circular path or looping the loop; that centrifugal force was balanced by the increased fift on the aeroplane wings, while the centrifugal force on the pilot's body was balanced by the greater reaction exerted by the floor or his seat. His body appeared to him to weigh much more than usual, and he might find it almost, if not quite, impossible to lift his arms or stand up. What was still more embarrassing was that owing to his blood weighing many times its normal weight it might gradually leave his brain in favour of a lower and more distensible part of the body. The immediate effect of the loss of blood in the head, though fortunately a temporary one, was the loss of sight. This was so common a feature of the fast flying of to-day that it was familiarly known as "blacking out." It was commonly claimed by aircraft pilots that this "blacking out" was not accompanied by any lack of mental clarity, and that control, a blind control, of course, could still be maintained on the flying of the. aircraft. Speaking of the future, the lecturer asked where was one to look for a limit to the range of possible speeds. To fly near the ground at speeds much above the present record- of 407 m.p.h. must be almost impossible without a drastic change in aeroplane construction. The relationship of air speed to horse power on a typical aeroplane was such as to give a ratio of the highest speed to the lowest approaching three to one. Suppose they could get a ratio of four to one. Then if the limit to safe landing speed were 120 m.p.h., a top speed exceeding 480 m.p.h. could only be obtained by the introduction of some such device as changing the wing area while in flight or using flaps or slots to reduce the landing speed. NOSE DIVES AT 650 MILES PER HOUR. Mr Wimperis was referring only to horizontal speeds. By diving vertically, even with the aircraft normally used by the R.A.F., speeds as great as the greatest he had named could be, and had been, attained. Such manoeuvres were, called terminal velocity nose dives— Schneider Trophy aircraft were not put into such dives, but if they were the terminal velocity would, he supposed, approach, the enormous speed of 650 m.p.h.! which was just about the velocity of sound. The drag of any body-through the air increased with the square of the speed and went on doing So until the velocity of sound, some 700 m.p.h., was reached. Then there was a great change; the drag suddenly more than doubled. Once this barrier was passed the xesi6tance law became again proportional to the square of the speed, 7 but with a higher, multiplying co-efficient. So he would not care to pTedict that passage beyond that barrier would ever be possible to aircraft as they knew tbem. If ever it wast done, it would seem, from the work of Stanton and Taylor, that it would be by making use of exceedingly thin, sharpedged aerofoils. PROBLEM OF HIGH ALTITUDES.

Without going so far as to exceed the velocity of sound, if one nevertheless sought speeds very mueh higher than those now usual one could find them by deserting the levels in which Schneider Trophy winners flew and by ascending to altitudes of 20,000 ft, 50,000 ft, and even 100,000 ft. There one would find so greatly reduced air density (about one-ninth at 50,000 ft for example) that the resistance to motion would be vastly reduced. It is unfortunate for our flying machine that the air supply for the engiue would be drawn from an equally attenuated atmosphere, and compressors, known as superchargers, would be needed. They took a power,to drive, and an allowance must be made' in our power outfit. Moreover, one must not forget the magneto, nor even the passengers who would be no : more contented with such tenuous air than was the engine. It was true that the supercharger which fed the engine could also feed the passengers, but the electric ignition spark would certainly pass elsewhere than through the compressed gases in' the cylinder if it could possibly do so. He did not suggest that these difficulties were prohibitive, but they were certainly formidable. LOW SPEED FLYING.

Referring to the low speed end of the range, he said there the addition of slots and flaps were of great advantage. But the application was not as simple as might be thought—the extra weight had to be considered; that would tend to put up the speed—and in particular the attitude of the aeroplane on landipg must not be such as to touch tail first. Such landings were not popular! The most direct solution of the low speed flying was. to maintain a high wing speed while keeping in low body speed, in other words, to use a rotating wing as in Gierva's wellknown autogiro. No' present-day fixedwing aeroplane could competed with the autogiro tor slow flying. If that aircraft could be made equally efficient when flying fast it would have an Unrivalled range of "speed" in flight.

ing our cultural heritage with a determination to do as science bids—issue purchasing power to consumers,, clearing the shelves of surplus goods, satisfying wants, and, above all, making the road to prosperity an assured success. Just let us have a look at bur business before it crashes. Our population is 1,500,000, including 800,000 males. Of the number 290,000 are boys; 70,000 are unemployed, and 10,000 in institutions. This makes the available number of citizens 430,000, and among them three-quarters of the Dominion's private wealth (£734,000,000) is divided. Against these resources of about half a million people stands the public debt of £275,000,000, upon which £13,000,000 of t interest falls due every year. The net indebtedness of the country per head is £lßl. Who pays?' As the unemployed numbers increase and businesses smash the indebtedness rate per head increases by the transference of the amount from the shoulders of thosfc who cannot pay on to the shoulders of those who can; but we still think "export," because interest must be paid. The position under our present system is impossible. If New Zealand would only take the lead our surplus could always be exported and sold for what it will fetch (that is what we do now); but who knows? With a lead in improved conditions and an eye-opener 4o the world, we may have no surplus. People would want to settle in New Zealand. We could comfortably accommodate 30,000,000 people here. Let this be our objective and let us strive for progress. Before we can expect this we need as leaders men with courage, men who know that strain reveals strength and, above all. the value of analysis lor boldness lias a genius, power, and magic in it. Not until people clear their minds of false ideas will our position improve.—I am,

etc., Poverty Amidst Plenty October 24.