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Aviation History
1913
1913 - 0065.PDF
JANUARY 18, 1913. so that x (on p. 128) = o, the complete set of resistance derivatives becomes : (jpycHT] Zw = KTU Lw = KTUv Mv- o z? = k'Tiy . za Lp = KU (2 /cosr a +• 7yJ) . L?=o M,= a i . Mt=4/trU/aw** if we assume A'to have the same value for planes and fin as sug gested by Professor Bryan on p. 130. Assuming also as he does that the product of inertia F = o, the complete set of functions becomes : « =WAB KU\ABT* fF 4^/sin2o+^(2/cos-« + Tr)) (.< —. = A'2U2 ^AT/tia3 a + 2/>'7Ycos2a + 4 PCIsin"0(2 /cos- a " + Ty3) % (v = 8 A^U3!']- sin2 0 cos2 a — BKUTy cos 0„ IV -4— K'lU-TIy sin2 a cos fl 0 As long as.r is - T", that is the centre of lateral pressure is above the centre of gravity these are all 4 '•'' as is needed for stability. But in practice r must be very small to prevent heeling over to a full side gust. If y =0 then (y would = o, and the aeroplane would cease to be stable, but apparently not dangerously so, since it would only indicate a condition of neutral equilibrium, i.e., no tendency to recover itself, but also none to upset further, that is as long as the further condition 1 + -'-' holds. Puttingy = o in the above func tions, § comes out so thoroughly •- "', that as there is no sign of a discontinuity one can be satisfied that it will also be + •'•' for ;> small negative value of y. Further calculation indicates that it will be ^2/,ir(.4r+ 2^/cos* a) + «• at least as long as y < TT/TcS slnJa and probably further and stability is assured. Without the negative tips it is impossible to obtain stability with a single vertical fin, as Prof. Bryan states clearly on p. 128. He shows later, on p. 137 how stability may be obtained by two liiiN, and the addition of negative tips in such a case would still further increase the stability. To conclude : negative lips shoull render an aeroplane immune, as far as lateral balance is concerned, to the effects of all partial horizontal gusts, while at the same time they should greatly improve the lateral stability, using the word in its strict sense. In the Dunne machine, the negative tips being at the ends of bent back wings, have doubtless some effect also on longitudinal stability, but this investigation shows they should have a very good effect if placed at the ends of ordinary wing-. To fit a couple of light spars (say steel tubes) into the ends of the main spars of the wings, and attach negative tips, ought to present no difficulty, and would be well worth trying. Their precipe size would be a matter of experiment, the correct size being obtained when the aeroplane showed no tendency to bank itself on putting over the rudder and leaving the warp loose. For safety it would be well to start with tips of a small area—say 2 or 3 square feet—that would produce a less effect than this, in case any unforeseen bad resul: should show itself, and then increase them to the proper siz; if the small ones proved harmless. It should be noted that the downward pressure of the tips would somewhat lessen the strain on the lift wires. ® ® ® © THE THAMES DISASTER. THE Thames, in the neighbourhood of Erith, was, on Monday last, the 13th inst., the scene of a double aviation fatality. Shortly after half-past three in the afternoon, Leslie F. Macdonald, flying a 70-h. p. Gnome-engined Vickers tractor biplane, with Harold England, a mechanic, as passenger, had, by reason of engine trouble, to descend on to the river. Both men were unhippily drowned. The machine on which the accident occurred was a tractor biplane of a new type, on which Macdonald had been flying at Erith for the past two or three weeks. They had started out from the private flying grounds adjacent to the Erith works of Messrs. Vickers, Ltd., for the purpose of carrying out a practice flight. It appears that the machine rose, keeping very low, and headed for the opposite bank of the river. Before it reached the opposite shore, however, it was seen to descend suddenly upon the water. Two minutes elapsed before the machine sank, and during that time it was observed through a telescope that one of the occu- pmts, probably England, the passenger, had got free from the cockpit and had succeeded in getting on to the upper plane of the machine. Shortly afterwards the machine sank, and he struck out for the Kent shore, from which two boats had put off to his assistance. Unfor tunately, before they could reach him, in fact, even before he could swim a dozen yards, he disappeared. The other occupant of the machine, apparently made no attempt to extricate himself, and so sank with it. In starting away they had both strapped them selves in with safety belts, which were both provided with quick release fastenings. The River Police and a party of men from the training ship " Worcester " were soon upon the scene of the accident, but although they have conducted an arduous search, dragging the river bed in the neighbourhood, they have not, up till the time of writing, succeeded in finding the bodies of the unfortunate men, or in locating the position of the sunken biplane. As for the cause of the accident, Cant. H. F. Wood, manager of the Aviation Department of Messrs. Vickers, Ltd., holds the theory that the catastrophe may be directly attributable to a badly running engine. It has been ascertained that at the time Macdonald left the ground at Erith the engine was misfiring, although perhaps the trouble, at that time, might have been so slight that it gave the pilot cause to think that the engine, after running a little while, would pick up its normal number of revolutions. From the reports of eye-witnesses, working men for the most part, but who are never theless used to seeing machines in the air, it has been learnt that the biplane was travelling at a much less speed than its normal flying speed of 60 miles per hour. Furthermore, some of those who watched the machine have said that instead of the propeller running smoothly, it appeared to flicker, a point which in itself points to the fact that the engine was running far from satisfactorily. At the time when the machine commenced its flight over the river, it had only attained an altitude of 40 to 80 ft. The pilot continued on, it is thought, in the hops that his engine would pick up. He could hardly have done otherwise, for, with such a poorly running engine, and having such little altitude, it would have Ijsen unsafe to attempt a sharp turn in order to get back to his starling point. As the engine showed no signs of regaining its normal number of revolution,, the pilot had three courses open to him. He could have landed on the opposite bank, he could have made a very gradual turn and so got back to his starting point, or he could have come down in the river. The opposite bank was sleep and unsuitable as a landing ground, and as Macdonald had oflen told Capt. Wood that should he al any time become forced to descend he would prefer to land in the river than to land on any ground the surface of which he was not acquainted with, it is conceivable, therefore, that he intentionally brought the machine down on to the water. On the other hand it may be that the engine power fell off so rapidly that the pilot could not prevent the machine dropping. This latter theory is rather supported by the fact that the engine was running when the machine dropped into the water. Had the pilot intended to come down in the river, he would most probably have switchjd off and allowed the machine to " pancake." Such is, at any rate, the cause assigned to the fatality formulated from the evidence that is available at the present time. For the rest, we must await the findings of the Accidents Committee of the Royal Aero Club, whose self-imposed duty it is to examine all evidence relating to serious accidents, and to publish recommenda tions which will assist in preventing recurrences of a similar niture. Leslie F. Macdonald, although only 22 years of age, was one of our earliest pilots. He obtained his certificate, numbered 28, on a Bristol biplane, at Brooklands on November 15th, 1910. It is a noticeable point, since more certificates have been won on Bristol machines than any other make of aeroplane in Great Britain, that Mr. Macdonald was the first to obtain his flying licence on a Bristol. In the January following he went out to Australia with Mr. J. J. Ham mond to demonstrate Bristol biplanes to the Government there. While in Australia he made many notable flights including one with General Gordon, Commandant of the New South Wales military forces, as passenger. He took the General up 10 3,000 ft., and at that altitude flew over Sydney Harbour, Government House, Botany Bay and the military barracks. Returning to England he was engaged, about 12 months ago, by Messrs. Vickers, Ltd., to test their machines, and he has held that position ever since. He did some remarkably good flying on the Vickers monoplane, fitted with a 70 h. p. Viale motor, that was present at Salisbury Plain during the Military Trials there. His companion, Harold England, was an engineer in the employ of the aviation department of Messrs. Vickers, Ltd. Our heartfelt sympathies go out to the families of the two unfortunite men in the sad bereavement they have sustained.
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