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Aviation History
1931
1931 - 0467.PDF
FLIGHT, MAY 15. 1931 Fig. 9. Fuel Jettison Arrangement. the whole engine is to be accessible. If the engines are fitted in the wing or in nacelles large enough for access to all parts, then trouble will be experienced in cooling the exhaust manifolds. Any solution to this problem will be unsatisfactory from the weight and reliability point of view. In the former case, in addition to the above, pro- peller shafts and housings have to be fitted, which entails a furtner increase in weight and may lead to serious torsional vibration. What is really required, as the best compromise for the present, is that the engine makers should fit all engine accessories, such as water and oil pumps, filters, carburettors and magnetos at the rear end of the engine where they would be readily accessible. Between the hull deck and the lower surface of the wing, and directly below the pilot's bridge, is situated the navi- gation bridge. This position gives an unrestricted all- round view, and, with the protection available, should satisfy all navigational requirements. The officers' and crew's quarters and all general equip- ment are arranged inside the hull, from which a com- panionway leads to'both bridges. The fuel tanks are placed inside the wing and fitted with jettison valves operated by the engineer. On the whole, the lay-out obtained would appear to result in a sound practical design of quite a pleasing appearance. We will now proceed to treat briefly several of the more important detail design considerations, which contribute largely to the efficiency and ease of operation. These are 'TheFuel Jettison Arrangement," "The Flight Con- trols," "The Arrangement of Fuel Tanks," and, lastly, Fuel Economy." The Fuel Jettison Arrangement The argument, which is sound and practical, in favour of the ability to jettison fuel in emergency, is that the hoat can then take-off with the maximum load possible under the conditions prevailing, and, all being well, will complete the flight as arranged. On the other hand, in the event of engine failure, sufficient fuel may be jetti- soned to lighten the aircraft in order that flight may be continued either to the specified destination or to the nearest base. yg- 9 shows an arrangement as applied to wing tanks, and mset, the type of jettison valve used. The arrange-e 'it shows that once the valve is opened, the escaping ei :s blown clear of the aircraft by the propeller slip- f and hence all risk of fire is eliminated. The valve fn-arigenient consists of a stainless steel flanged circular Im ° 4 in- to 6 in- internal diameter, bolted to the~\Part °f the tank bottom she11- On this base is l a circular corrugated seat. An outer flanged ring, similar seating, is bolted to the base ring, the corru- S^tlngS .forminS the Joint for a s4 S.W.G. soft w^ic^ 's the valve proper. In this outer ring a stee* circular ring on which are formed • given an upward and rotating motion by means of a lever operated from any convenient position. The cutter, there- fore, pierces and cuts round the disc, which then falls clear and allows the fuel to escape. A new disc would require to be fitted prior to re-fuelling. It will be seen that the arrangement shown is light, simple, safe and effective. The Flight Controls It is fundamental to the success of a flying boat of the size contemplated that it should not be tiring to fly for lengthy periods. It is, therefore, necessary that the con- trols should be light to operate and well matched. There is no valid reason why, with increase in size, the controls should become heavier to operate, as analogous to the case of the rudder operation of large ships in which lightness of control is obtained by the use of Flettner-type serves or some form of mechanically-operated servo-motor, mainly the latter, we have at our disposal similar means of opera- tion in the now well-known aerodynamic servo-control system and the mechanically-operated gyro-controlled " Assister Pilot." In conjunction with the above systems of control opera- tion, the control surfaces would be balanced aerodynami- cally by, preferably, some form of the backward hinge method by means of which static balance of the control surfaces (of importance with regard to the avoidance of flutter) presents little difficulty. In the multi-engined aircraft, the rudder control is prob- ably the most important, as, in the event of an outboard engine failure, rudder has to be carried to balance the loss in thrust moment. In the design proposed, there are three all-moving rudders an arrangement which has been successfully tested on the " Sydney." The centre, or trimming rudder, is operated by means of a lever in the pilot's cockpit, and is used for adjusting the directional trim in the case of engine failure, etc., while the outer, or control, rudders are connected to the rudder bars in the usual manner. With this arrangement, and it is a point is f Ati *'tria ' i a • 'lar-shaped stepped cutters. This cutter may be M/fc 30 000 GROSS WEIGHT Or M/C. La> 28, 000 26.000 24.000 22.000 20.000 IDEAL POSITIONS 0? FUEL C. G ASSUMED IN TRIM WITH FULL T WT. Of f -760C-7000 -600C -5000 -4000 •3000 -2000 - 1000 - 0 UEL L» ^- DIS 2 TANCE < / ALONk 5' ^ h- 1 / / J'TOP M.P (5' t ANKS f7'^- '(- L_i_ N X HORD IN F.1 '' (, • ~) J - j' id 0-1 0? 0-5 0-4 05 0-6 0-7 DISTANCES IN TERMS OF CHORD 435
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