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Aviation History
1951
1951 - 2076.PDF
12 .October 1951 489 FUTURE STRUCTURAL PROBLEMS . . . on the basis of strength data obtained at high temperatures would need to include the effects of creep. It was unavoidable that much higher rates of creep would have to be tolerated in structural elements of supersonic aircraft, and for this reason the study of creep phenomena would have to be extended. In aeronautics the safety factor, usually denned as the ratio of the failing load of the structure to the expected maximum load imposed upon the structure, had little physical significance. Replacement of the safety factor concept by a more rational measure of safety was, however, not an easy task. The lecturer referred to the determined effort made in France to introduce probability calculations into the evalua- tion of the safety of civil engineering structures. Civil engineers were trying to establish probability curves for the stresses induced in a structure by dead and live loads and, at the same time, to establish the strength of the structural materials by means of curves of probability. On the basis of this information the probability of the actual stress exceeding the strength of the structure could be calculated rationally. An interesting feature of this approach was that the proba- bility of failure could not be zero, but should, nevertheless, be a very small number. In conclusion, the lecturer reviewed the proposition that future, aircraft could be classified into three categories from the standpoint of safety, namely Class A, not expendable; Class B, semi-expendable; and Class C, expendable. All aircraft flying at present belonged to Class A, while the guided missile, obviously an expendable article, belonged to Class C. The phenomenon of creep, which became increas- ingly noticeable as the structure was heated, necessitates the introduction of a Class B for piloted aircraft. Mr. Hoff stated unequivocally that it would not be possible to design aircraft to fly efficiently for an indefinitely long period of time at M = 3 or 4. Inelastic deformations were bound to take place and a thorough understanding of the phenomena would be needed in order to determine just how long a particular aircraft would remain safe. He believed, however, that when a consistent theory corroborated by experiment was available, the passengers and crew would trust the supersonic semi- expendable aircraft just as much as, today, they trusted the non-expendable subsonic aircraft. FOR REFUELLING THE COMET THE refuelling of aircraft both on the ground and in the air has,in recent years, developed into one of the more specialized branches of the industry dealing with aircraft auxiliary equipment.In parallel with the gradual acceptance of certain operational advantages associated with pressure refuelling, the Shell PetroleumCo., Ltd., has developed a general-purpose airport refuelling truck which will be known as the "Dorset." A fleet of 60 of thesevehicles has been ordered by B.O.A.C. to refuel, among other aircraft, the Comet at its calling points next year on the Johannes-burg and Sydney routes. Designed by Shell in close collaboration with Thompson Bros.(Bilston) Ltd., and Leyland Motors, Ltd., the "Dorset" has a capacity of 3,000 Imperial gallons and is capable of pumping fuelat pressures of up to 100 Ib/sq in, though only 30 lb/sq in will be required in the case of the Comet. An engine-driven single high-capacity pump and pressure control valve permit two-hose pressure delivery at 350 gal/min which, with two trucks at eachrefuelling point, will mean that 6,000 Imp. gal can be supplied to the Comet within 15-20 min. At a recent demonstration atLondon Airport, incidentally, it was possible to deliver con- tinuously at 208 gal/min on one hose only. Another feature of the "Dorset" is the pressure-control valvedesigned by Shell. This unit allows any desired fuel delivery pressure to be pre-selected beforehand, and, what is moreimportant, shuts off the supply immediately the pre-selected pressure is exceeded. This automatic closure is important in viewof the pressure build-up when the aircraft tanks are full. The valve, which may be located at any convenient point inthe system, consists of a combined reducing and shut-off valve The central control panel is seen in this view of the new Dorset refueller, 60 of which have been ordered by B.O.A.C. coupled to and controlled by two pistons working in oppositionto each other. The effective pressure areas of the pistons and valve member are equal; thus the whole moving assembly is instatic balance. One piston operates in a cylinder which terminates in an air chamber connected to a pressure gauge and hand-operatedpump, while the other operates against the fuel pressure, which is bled, in this case, from the delivery-hose coupling. By increasingthe air pressure on the piston, the valve is opened and a propor- tional quantity of fuel is delivered at a controlled pressure tothe aircraft tanks. Immediately the tanks are full, the correspond- ing pressure increase of fuel in the hose offsets the air pressureon the piston and closes the valve. HIGH, WIDE AND HANDSOME ultra-modern factory forms part of the development and expansion ramme planned by Aero Research, Ltd., Duxford, the synthetic- -adhesives specialists. The production area has a floor-tO'Ceiling 'it of 50ft and is supervised by the "cantilevered" offices and laboratory. Ove Arup and Partners were the architects. FOR THE LAST TIME (Cont. from page 481) the carrier Eagle on the China Station and later becoming FleetAviation Officer, Mediterranean Fleet. Reference has already been made to his third period at C.F.S.,as Commandant, and it was while he was in this appointment that he went to Canada to plan with the Canadian authorities thehuge scheme to train pilots for the R.A.F. As a result of this scheme 360 schools and ancillary units were formed and over 130,000 air-crew trained in them. Sir James' next command was No. 2 Group, Bomber Command,which in 1940 was the only day-bomber group and from here he went to Coastal Command as A.O.C. No. 15 Group. In 1942,as A. V-M. Robb, he was deputy chief to Lord Louis Mount- batten and took over the Air Command of Gibraltar at the time ofthe invasion of North Africa. For this operation he assembled no fewer than 367 Spitfires and Hurricanes. By the end of that year he was Air Adviser to GeneralEisenhower and became the Deputy Commander of the joint R.A.F. and U.S.A.A.F. in North Africa. Returning to Europefor the invasion, he became Deputy Chief of Staff (Air) to General Eisenhower and remained in that capacity to the end of the war,taking over in addition the duties of C-in-C. Allied Expeditionary Air Forces from the late Air Chief Marshal Leigh-Mallory. Since then the Air Chief Marshal has been A.O.C.-in-C.Fighter Command, Vice-Chief of Air Staff, and, finally, C-in-C. Air Forces, Western Europe. J. Y.
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