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Aviation History
1948
1948 - 1928.PDF
594 FLIGHT .NOVEMBER I8TH, 1948 The Gas Turbine in Service Aviation .... equivalent cruising fuel consumption of the order of0.42 lb/s.h.p./hr. Although the compounded piston engine would probably have a lower cruising fuel consumption(about 0.38 lb/b.h.p./hr.), it would be heavier and have a much higher installed drag because of cooling requirements.The propjet bomber would probably cruise at a higher per- centage of its maximum power and speed than its piston-angined rival. The problem of building an aircraft for a still-air range of12,000 miles was still formidable. Calculations showed that for such a range, to fly at 40,000ft and 500 m.p.h., with auseful bomb load, the machine would be about twice the all- up weight of the Brabazon I (about 500,000 lb). This assumedan airscrew efficiency of plus 80 per cent, which might be difficult to attain. As a matter of interest, the Air Com-modore recalled that, towards the end of the recent war, a power plant was considered for a reconnaissance aircraft oflong duration (25 hours; 7,500-10,000 miles range). Calcula- tions showed that there would be a difference of 60,000 lbin the all-up weight in favour of a compounded piston engine giving a specific cruising fuel consumption of0.34 lb/b.h.p./hr., compared with 0.44 lb/b.h.p./hr. offered by a conventional piston engine. A. Cdre. Banks did not think that the tailless aircraftwould persist in the military sphere. One of the disadvan- tages he mentioned was that if the control surfaces were shotaway or suffered Battle damage, there was little hope of getting the aircraft safely back. The c of g limitations would pre-judice modification. There was, however, one type of tail- less aircraft which would undoubtedly have a place in mili-tary aviation because of the really high performance it offered —the Delta wing. This would not, however, be developedfor service use within the next 15 years. As might have been expected, the lecturer had some interest-ing observations to make on the subject of fuel. At the moment, kerosene - (paraffin) was used in gas turbines, butturbojets were usually cleared for emergency operation on normal 100-130 grade leaded fuel. Turbojets for the U.S. Navy were tested on kerosene, but used aviation gasoline onshore and in carriers because of the problems involved in storing two different fuels. It was more than doubtful whetherkerosene would be available in time of war. Since gasoline remained the product in greatest demand from crude oil, andbecause the refining charging stock to make gasoline com- prised a large proportion of the "middle of the barrel" pro-ducts of the crude (which included kerosene), it was not diffi- cult to see that anything taken from "the middle of thebarrel" would tend to reduce gasoline supplies. The demands of surface transport would, said A. Cdre. Banks, still begreater in war than those of aviation. If he remembered trightly, twelve U.S. gallons of petroleum products were used "on the ground in the recent war for one U.S. gallon used inthe air. Although the turbine would undoubtedly be de- veloped to use higher flash point fuels, which would reducethe fire hazard, military demands for gas turbine fuels in time of war would be so great that it would not be possibleto supply these special fuels. ^ Another three to five years would be needed for proper 'anti-icing systems to be evolved which could be incorporated as an integral part of the engine.In his closing remarks the lecturer observed that it looked as if future advances in aerodynamics, and consequently inaircraft design, would eventually bring us to a stage where all the world's first-class military aircraft would have verymuch the same performance, particularly as the gas turbine could provide all the power needed. This state, however,would never come about in our lifetime. Britain should be able to retain indefinitely her lead in the gas turbine field.The U.S.A. was certainly ahead at present in aerodynamic progress, and it would be difficult for us to level up withthem in this respect. "But this country," concluded the lecturer, "has alwaysbeen blessed with practical thinkers and men of imagina- tion, so there is every reason to hope that we willnot be too far behind, if we are behind at all, in ten or fifteen vears' time." TWO SWEDISH TURBOJETS "PRELIMINARY information concerning two quite differentX Swedish gas turbine power units was released for the first time last week, although the existence of one of them wasmentioned in our article dealing with the work of the manu- facturing company earlier in the year. This company, theSvenska Flygmotor AB of Trollhattan, have produced and are testing a development unit to the design of Mr. Alf Lysholm andMr. G. A. Dalhammar. It has a two-stage centrifugal com- pressor and four-stage turbine, the layout being somewhatsimilar to that illustrated on page 217 of the August 19th issue of Flight. This unit is in the 2,000-3,000 lb thrust class. It will be remembered that S.F.A. are preparing to build D.H.Goblins under licence and later on may also produce. Ghosts. An axial-flow design, the work of designers Curt Nicolinand Eric Ostmar, has been built by Svenska Turbinfabriks AB Ljungstrom of Finspang. This is on test and the only datareleased is that it has shown an efficiency of 87 per cent, and has been tested at a working pressure of 3.2 atmospheres. The only other turbine running with two-stage centrifugalcompressor is the Rolls-Royce Dart turboprop. The SFA design, however, has reverse-flow annular combustion, thechamber being arranged around the multi-stage turbine. Newly announced turbojets from Sweden here illustrated for the first time are (/eft) the STAL Sweden's first axial-flow straight-through design, and (right) the SFA two-stage centrifugal type. Both are under active development. 3 18
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