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Aviation History
1947
1947 - 1201.PDF
JULY 24TH, 1947. FLIGHT J 79- The Trent is basically a Dement II modified to drive an airscrew. The reduction gear built into the access- ory casing is seen to be extremely compact, and the ratio is 0.141 : I. The power output is 750 s.hp plus 1,000 Ib jet thrust Two important characteristics of the Meteor with Trent airscrew turbines are its rapid acceleration should it be com- pelled to overshoot when about to land, and its good single-engine performance. In this new aerial view the five-blade Rotol airscrew of the starboard engine is seen to be feathered. Rolls-Royce Airscrew Turbine Development: Flight- Tesling the Trent-Meteor * KNOW-HOW FROM THE TRENT ALMOST two years have now passed since W/C. Hay-worth, Rolls-Royce assistant chief test pilot, madeL the first flight in the Trent-Meteor, and since then this interesting experimental aircraft has provided the Rolls- Royce Company with a great deal of invaluable information on airscrew-driving turbines generally, and, in particular, on reduction gear and airscrew problems. It was, in fact, the investigation of these matters without the delay which would have been occasioned by awaiting the production of an entirely new engine that led to the development of the purely experimental 1 rent airscrew-turbine combination. Investigation first began when the Welland was tested for shaft-horse-power. The tests are of historic interest in being the first b.h.p. tests ever made with an aircraft gas feurbine. The Trent engine, which represents the next stage, is '5. Derwent II redesigned at the front end to take a reduc- tion gear, and this hybrid unit which originally gave 2,200 lb thrust was first tested with reduction gear but without airscrew in May, 1944 In March of the following year it was hangar-tested with a five-blade Rotol airscrew, and the first historic flight, mentioned above, was made in September, 1945. Its first public appearance after many hours of flight development was at the Derby International Air Rally on June 21st last. Of the 1,000-plus hours of test running to date over 400 have been completed with Rotol airscrews fitted, and the tffect of an airscrew hub on air intake efficiency and the suitability of various reduction gear designs, are two typical examples of the development work undertaken. The reduc- tion gear of the Trent consists of three layshafts arranged to form a double train of gears driven from the compressor and having a final simple spur reduction gear to the air- screw. The overall reduction ratio is 0.141:1. Plain spur- type gears were used in the early designs, but due to vibrations set up as a result of the high contact speed of the gear teeth coinciding with the natural frequency of the tab washers in the gear-locking ^devices, fatigue of the washers occurred followed by failure of the gear. Redesign to provide additional strength and special balancing of the drive seems to have overcome this trouble, and the present gear has proved entirely dependable after many hours of test-bed running. Two Treats were fitted in a slightly modified Afeteor Mk I for flight trials. The undercarriage was stiffened up and the legs lengthened to give an additional six inches of ground clearance for the 7ft 7m five-bladed airscrews. The .proportion of the shaft power to the jet thrust is now 750 h.p. to 1,000 1b. Airscrew and "Throttle" Controls The first flight trials were made with independent con- trols for the throttles and constant-speed units, the inten- tion being to find out what degree of co-ordination would be required between their respective movements. How- ever, it was found that a very great degree of skill was required to operate the separate controls and that very rapid changes in thrust were encountered amounting in extreme cases to negative thrust. As a result of these unsatisfactory qualities the Trent-Meteor was temporarily grounded, and upon resumption of development very small airscrews 4ft io^in in diameter absorbing only 350 h.p. (Concluded on page 82.)
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