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Aviation History
1951
1951 - 0880.PDF
u May 1951 551 achieved 84:1 pressure ratio with an efficiency of 72 per cent. Somewhat similar difficulty was encountered with the turbine. Whittle's calculations could not be reconciled with the best established practice. Both sides re^becked their calculations and both were reassured they were correct. Whittle explained his were based on the aerodynamic theory of the free vortex, giving a pressure difference along the radial length of the turbine blade. This was regarded as sheer heresy, as turbines had always been designed on the assumption of a uniform pressure along the blade. Whittle, however, proved his case and revolutionized design.. Despite the necessity to surpass all previous engineering experience in the compressor, the combustion equipment and the turbine, the highly desirable individual development of com- ponents was precluded as too lengthy and costly a process in view of the company's limited resources. The decision had to be made to build a complete proving engine. While work proceeded on the compressor and turbine, experiments were conducted at the B.T.H. works with combustion apparatus supplied by Laidlaw, Drew and Co., and testing of the complete unit began on April 12th, 1937. It continued until August of that year when, the lessons having been learned, modification and reconstruction were decided upon. An element of danger was involved in testing and accordingly it was deemed advisable to discontinue running at Rugby and B.T.H. leased premises at Lutterworth for the purpose. Initial Success By this time the Air Ministry, on the advice of the Aero- nautical Research Council, awarded contracts to Power Jets, Ltd., for further research as a "long-term" project. This changed the course of events, as strict secrecy was then imposed, in accordance with established practice in such matters. Tests on the recon- structed engine were commenced at Lutterworth in April, 1938, but difficulties were encountered with combustion and in May the unit was damaged by failure of a turbine blade. Once again it was modified and rebuilt. The third version was under test intermittently from October, 1938, to February, 1941, when it was wrecked by turbine failure. (This actual unit, in its wrecked condition, is a prominent exhibit in the aircraft engine lection at the Festival of Britain.) During this period the ccm- bustion difficulties were resolved, mainly by means of assistance from the Shell Petroleum Company's Technical Department under I. Lubbock—whose retirement, incidentally, was announced three weeks ago. He developed an atcmized-spray burner— earlier efforts had been with vaporizing burners—and also a more satisfactory sheet-metal combustion chamber. Shell also loaned to Power Jets for two years J. R. Joyce (now prominent at Thornton Laboratory) to assist with burner and fuel problems. The relative success of these trials caused the Air Ministry to change its view and to regard the project as the basis of a practic- able propulsion unit. Accordingly, it awarded contracts to Power Jets for a flight engine on July 12th, 1939, and to the Gloster Aircraft Co. for an experimental jet aircraft on August 30th, 1939. The power unit, designated the Wi, was sub-contracted to B.T.H., but during building certain of the components were deemed to fall short of specified requirements. These pans formed the basis of the first experimental flight engine WiX, which was assembled and tested while the Wi was being completed. When Wi was delivered some modifications arising from experi- ence with WiX were embodied, and after a few preliminary runs it successfully passed a 25-hour special-category test on April 12th, 1941, clearing it lor flight. By this time the Gloster £.28/39 aircraft had been completed and the WiX unit was installed lor taxying trials. During one of these trials the aircraft actually left the ground in a brief, straight hop. 1 he W1 engine was passed for ten hours flying and was duly installed. Commencing en May 14th, 1941, the lull programme of flight trials by test pilot P. E. G. iayer was completed in a fort- night without incident. 1 hat fact speaks volumes lor the elaborate care and foresight lavished on the project prior to the trials. 1 he method used was on the following toes. A series of informal "post- mortems" was held, at which a combination of possible circum- stances was envisaged and the probable efiects investigated and discussed. An example will illustrate the procedure. 1 he question was posed as to what would happen if, alter a run at high speed, the power unit was voluntarily or involuntarily cut. As the strength of the long, sheet-metal tailpipe was materially lowered at the operating temperature could it then support the 5lb-sq. in pressure in the fuselage? (This point is explained in the next paragraph.) Doubts were expressed, a test was made, and the tail- pipe collapsed. A redesigned pipe with peripheral stiffening ribs withstood the test and was installed. It is not generally appreciated what an outstanding aircraft the Gloster E.28/39 was, and how brilliantly W. G. Carter and his team solved the problems presented by this entirely new type. It was the first turbine-driven aircraft and also the first to be jet- propelled. Lacking an airscrew, there was obviously no slip- stream for the control surfaces. As the jet unit was enclosed in the fuselage due allowance had to be made for a not inconsiderable extension of fuselage length, resulting frcm expansion under operating thermal conditions. It was the first British single-seater aircraft to be equipped with a tricycle undercarriage, and this was the first occasion on which the single-leg undercarriage was used. The Dowty Equipment Company of Cheltenham had a hand in this. It can well be claimed to be the first pressurized British aircraft, since the after half of the fuselage served as a plenum chamber for the power unit and was therefore under about 5 lb-sq in pressure when in flight. It was the first British aircraft to be equipped with an automatic observer; i.e., built-in photo- graphic-recording appararus_ with push-button control. Finally, although specified for a maximum speed of 450 m.p.h. it exceeded that figure by more than 50 m.p.h. The successful trials metamorphosed the situation. The Ministry of Aircraft Production decided to plan the production of a Whittle turbojet and the Gloster F9/40, the Meteor, a new fighter with twin jet units in wing nacelles. In July, 1941, under the wartime technical collaboration arrangements, a full disclosure was made to Gen. Arnold of the U.S. Air Force. He arranged for a Liberator bomber to be sent from America and the WiX unit, a full set of drawings of a later version, the W2B, and a small team of engineers were f own over. The Americans are fast workers. In September, 1941, the WiX was delivered to the General Electric Co., and an order was placed with the Bell Aircraft Co. for a twin-jet aircraft. Only twelve months later, on October 1st, 1942, the first American-built turbojet made its maiden flight. Typical of the measures taken to preserve secrecy at the time is the stratagem used when the B " The WI unit with reverse-flow combustion chambers was the first flight engine. Jt is now preserved in the Science Museum, South Kensington t
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