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Aviation History
1940
1940 - 1908.PDF
JULY 4, 1940 ASSISTING TAKE-OFF AND ALIGHTING (CONTINUED) the water-line. Excessive loads on the hull due to high alighting speeds may be avoided by replacing the plan- ing bottom and steps by a sharp Vee down to the keel. This would give shockless entry on alighting and so per- mit higher rates of vertical descent. In flight it would provide extra vertical fin area which is aerodynamically desirable. A factor which causes present flying boat hulls to be larger than aerodynamic considerations render desirable is the necessity for adequate airscrew clearance. Damage to the screws through striking the water only occurs The adoption of this technique for launching and alighting would extend the field for assisted take-off. The great advantages of being able to operate from costless aerodromes without the expensive incubus of an undercarriage and without v.p. airscrews would outweigh many times over the capital cost of the launch- ing device, and so recommend the technique for ordi- nary operation. Here, where wing and power loading is not carried to extremes, a high thrust / weight ratio for the launching device is not so important and it may be constructed very robustly. Launching gear approaches aircraft from rear. Vacuum plates applied. Commencement of take-off run. Flying speed—about to release. . •"•'<• 'Aircraft released. Fig. 2. Stages in operations of mounting and launching aircraft. during the take-oft run, it does not happen during alight- ing when the engines are idling. For this reason, a hull designed for alighting only may be much lower in the water. This would give increased stability and sea- worthiness and reduce the size of wing-floats. "Aerodromes" so assiduously by the Bomb Proof The objection, urged s pro- tagonists of auxiliary aircraft against any surface device for assisting take-oft, that in the event of engine failure soon after take-off, disaster would ensue, has obviously less force hi the case of an aircraft operating from a water base and capable of alighting at very high speeds. For trans-ocean aircraft where high wing and power loading would be used together, the launching device would need to exert a considerable accelerating force during the take-off. This means that its thrust / weight ratio must be more favourable than that of the aircraft. To secure the greatest effect, it must be much more favourable. Fortunately, with the hydroplane launch- ing gear, this result is easily secured. The Schneider Trophy seaplane had a power /weight ratio of 2.89 lb. per h.p. If a complete seaplane can be built within this figure, then obviously a device which consists of the flotation gear and power units of a seaplane should weigh no more. There appear advantages from the military stand- point. Water bases are obviously bomb-proof. The aircraft would be cheap in first cost and maintenance and, owing to its simple structure, less vulnerable to gunfire than land types. The launching device simi- larly would be cheap, robust and mobile, and would appear well adapted for naval co-operation work. Here it would enable shore-based aircraft to alight on the sea and be refuelled, thus doubling the effective range of interceptor types. No specially constructed ship would be necessary as the launching device is readily dismantled for deck-stowage and its great -in- herent stability would enable towing. High perform- ance aircraft capable of being operated from water might have been very useful in Norway recently. [While complimenting Mr. King on the originality of his idea we feel it is necessary to give serious thought to two points involved in this method. We wonder if length on the water-line will prevent a stepless flying boat from porpoising, which, if it occurred in the alighting run at about 100 m.p.h., would be a highly dangerous thing. And v.p. airscrews would certainly be necessary for the climb, for the boat would presumably leave the floats at about 100 m.p.h. As any flying boat of the future will have to cruise at not less than 250 m.p.h. it seems that a v.p. air- screw would be needed to give reasonable efficiency at these widely different speeds.—ED.J
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