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Aviation History
1920
1920 - 1134.PDF
It was largely owing to war requirements,that is of rendering i:he petrol system still workable when parts of it might be out of action due to gunfire, that petrol systems became complicated. Peace requirements demand a return to the simplest kind of system, and one that imposes the least possible strain on the pilot. The above remarks simply emphasise the necessity for making the pilot as comfortable as possible, for giving him a simple, accessible and easily understood mechanism for •controlling the engines and petrol system so that he may- have attention left for appreciating correctly the effect of the engines on the aeroplane and using his aeroplane controls in the best way. Practical Flving Notes on Twin -Engined Aeroplanes These notes are based on flying experience with the Handley Page o 400 fitted with twin Rolls Eagle VIII. engines ; an experimental one fitted with four 200 h.p. Hispano engines mounted in tandem pairs ; the Vickers Vimy with twin Fiat and twin Rolls engines ; the German A.E.G. Bomber, and the D.H. 10 with twin Liberty engines. The Handley Page o 400 was introduced and flown for a considerable time on service without any serious troubles being reported due to turning tendency caused by engine failure on twins. This was mainly due to the fact that relative to the pawer of its engines the aeroplane was of large dimen- sions. If one engine dropped revolutions the turning tendency was not violent, the whole aeroplane being comparatively sluggish due to its large moment of inertia. Nowadays Handley Page aeroplanes have the propellers both of the same hand ; some earlier examples had propellers of opposite hand, and the difference between the two arrange- ments was felt by pilots. There is a turning tendency due to slipstream, which though not very marked, can be detected when both propellers revolve trie same way. Where the propellers revolved opposite ways the turning tendency entirely disappeared. It was when aeroplanes of smaller dimensions for the same power were flown that the first serious trouble arose due to the failure of one engine. The Vickers Vimy and the D.H. 10 both swung violently round if one engine failed, the latter more quickly than the former owing to its small size. If the pilot is taking off the ground and has not had time to gain sufficient airspeed to fly straight on one engine, the obvious thing to do if one engine fails is to throttle the other right down, and if he cannot, by putting the nose down, attain this speed before being compelled to land, he must land wherever he is. There is no other alternative. Not only is this the •case, but he must be very alert in throttling down the engine that is still running, or otherwise he will find that the aero- plane is swinging round flat, and thus his longitudinal control has lost much of its power ; in fact, on an aeroplane like a D.H. 10 the safest thing is undoubtedly to switch the engine off. This course immediately deprives the pilot of the assistance of any engine power, and if he can afford to control the aeroplane with the engine throttled down and not switched off, his glide is flattened and he has more chance of landing •on a good piece of ground. Before attempting to taxi out on a twin that has not been tested the pilot should take all preparatory measures that are possible on the ground to ensure that his petrol system will be satisiactory in the air. If the petrol is pumped up to a gravity tank which feeds the engines, he should make sure that the delivery from the gravity tank is considerably in excess of the amount required by both engines by taking the petrol flow at both carburettors simultaneously, both with the tail skid on the ground and the aeroplane in flying posi- tion. If he is sure of an adequate flow from his gravity tank. OCTOBER 28, 1920 then he is sure of enough petrol to tide him over the first few hundred feet of his climb, which is the difficult period from the aeroplane point of view. He should run up each engine separately so that he may listen to it without being confused by the noise of both running at once. He should make sure that his throttles work easily and do not slip back-. wards or forwards when the hand is removed from them. It is always wise to taxi for a certain distance before taking off (even though it is possible to take off from the position of running up) so as to give the petrol pumps (if the petrol system includes them) a chance to work a little. It is then possible while taxying to give one or two bursts with each engine to see how it opens out, allowing the aeroplane to swing round either way. Unless the pilot is not only accustomed to the type, but is also familiar with the particular aeroplane, it is unwise to attempt a fancy take-off, such as a cross wind with one wing down, or by opening the throttles violently and pulling the aeroplane off the ground at a low airspeed. This may be done on a single-engined aeroplane without involving much risk if the engine fails. The pilot should open the throttles gently and take a good run over the ground if it is smooth enough to permit of this, and even when he has left the ground should hold the nose down near the ground until he has attained an airspeed of 60 m.p.h. If one engine fails and he is 15 ft. off the ground doing 45 to 50 m.p.h., he has no chance whatsoever of controlling the swing of the aero- plane. He has only to try this at a safe height by switching oft one engine at various airspeeds from 50 m.p.h. upwards and he will soon find out his power of controlling a swing. A D.H. 10 will swing through 90 degs. in about 3 sees, if one engine is switched off at 50 m.p.h. The safest way to take off is with one hand on the throttles so that if one engine fails the throttles may both be pulled back. If the pilot puts the nose of the aeroplane down it will then commence to elide, and if he has sufficient height to attain the airspeed at which he can fly reasonably straight on one engine, assisted by a judicious use of bank, he can then again open out his sound engine and use it to carry him on and effect a landing on good ground. If he is very near the ground and an engine fails, even before he can throttle down the other engine the aeroplane will have swung through a certain angle and thereby considerable drift will have been set up, which if there be no room to sideslip, it will be impossible to eliminate before touching the ground. Thus he is almost certain to dam3ge his undercarriage, though probably nothing of a more serious nature will occur. When taking off in bumpy weather the aeroplane is slewed about in the bumps, and the sound of the engines is always less regular than in calm weather. This adds to the pilot's difficulties in detecting a faulty engine as he can only tell it by the feel of the aeroplane, the sound of tlje engines or by the revolution indicators. His first method of knowing is impaired by the bumps, as a bad bump sometimes feels similar to a swing under the influence of engine, his second method by the irregularity of the sound of the engines in gusty weather and by the fact that both engines are running together and the sound of the good one obscures the sound of the bad one, his third method by the fact that it is very awkward to look round at the revolution indicators, especially when he cannot tell by other means which is the defective engine. As laid out in detail, these difficulties appear of the gravest nature. In practice an intelligent pilot has always his flying instinct to help him, which is a very difficult thing to define, but it is clear that the greatest caution should be exercised due to the special characteristics of this type of aeroplane. Air Work in Mesopotamia THE communiquB issued by the War Office on October 22 stated :— Aeroplanes bombed a hostile band which had gathered in neighbourhood of Samawa. '• Aeroplanes have carried out effective attacks on hostile •concentrations near Abu Sukhair and Uwal Barur." The communique issued on October 23 stated :— " Our aeroplanes have been active, bombing hostile gather- ings in the vicinity of Ur and Nasirieh. Strong hostile •concentrations in the former area are reported." A French Variable Wing THE recent speed range competitions in France have inspired M. Levavasseur and M. Robert Gastambide, the pioneers who produced the Antoinette monoplane, to tackle the problem of variable wings. They have produced a "biplane fitted with a wing, the area of which can be increased from 30 to 50 sq. m. This is accomplished by two sliding portions, one moving forward and the other rearward, the latter varying the camber of the plane. During trials carried out at Etampes with Grandjean as pilot, the machine showed a top speed of 200 k.p.h., but this was reduced to 60 k.p.h. for landing. Trials are shortly to be made for the prizes offered by the Union pour la securitt en a-non. The Joy-Stick Litigation THE French Court of Cassation on October 20 rejected the appeal of Farman Brothers against the writ of attachment on moneys owing by the French Government obtained by M. Esnault Pelterie, in respect of royalties on his control lever patent. This appeal was regarded as a test case, and the result will affect a number of other firms, against whom M. Pelterie has obtained writs. New Speed Record FLYING the 13-sq. m. Nieuport(3oo-h.p. Hispano), piloted by Kirsch in the Gordon Bennett race, Sadi-Lecointe has achieved his ambition of being first to officially attain a speed of over 300 k.p.h. He covered the kilometre in one direction in 12-n, sees., and coming back did the distance in the reverse direction in n-y^ sees., making his average time 11-nj sees., the speed working out to 302-525 k.p.h., or 189 m.p.h. 1136
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