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Aviation History
1941
1941 - 0607.PDF
and AIRCRAFT ENGINEER FIRST AERONAUTICAL WEEKLY IN THE WORLD •• FOUNDED 1909 Editor C. M. POULSEN Managing Editor G. GEOFFREY SMITH Chief Photogmp'er JOHN YOXALL Editorial, Advertising and Publishing Offices: DORSET HOUSE, STAMFORD STREET, LONDON, S.E.1 Telegrams : Truditur, Sedist, London. Telephone : Waterloo 3333 (35 lines). 8-10. CORPORATION ST., COV E NT R Y. Telegrams : Autocar, Coventry. Telephone: Coventry 5210. GUILDHALL BUILDINGS, NAVIGATION ST., BIRMINGHAM, 2. Telegrams: Autopress, Birmingham. Telephone: Midland 2 97 1 (5 lines). 260, DEANSGATE, MANCHESTER, 3. Telegrams : Iliffe, Manchester. Telephone: Blackfriars 4412. 26B. RENFIELD ST., GLASGOW, C.2 Telegrams : Iliffe, Glasgow. Telephone: Central 4857. SUBSCRIPTION RATES: No. 1681: Vol. XXXIX. Home and Abroad : Year, £3 10. 6 months, Registered at the C.P.O. as a Newspaper. MARCH 13th, 1941 £1 10 6. 3 months, ISs. 3d. Thursdays, One Shilling. The Outlooks Direct or Indirect Cooling ?D URING the first years of its evolution the air- cooled aero engine struggled against many difficul- ties. It gradually overcame most of its early teething troubles, and its low specific weight and general sim- plicity were always points in its favour. For some years the problem of cooling was imperfectly understood, and it cannot be denied that both on the score of form drag and that of cooling drag the air-cooled engine showed up to disadvantage. Then came the Townend ring, a sort of Handley-Page circular slat, which kept the exuber- ance of the air flow somewhat in check. This cowling ; '~lTring did much to give the radial air-cooled a new lease r ' of life. In America the N.A.C.A. evolved the long-chord cowling, and the system of baffles. In the meantime, research in England led to an appre- ciation of the possibilities of low-drag liquid cooling, and a Farnborough technician, Mr. Meredith, called attention to the ability of so-called ducted cooling to reduce drag, and even to convert it into a positive thrust. It was natural that this discovery, plus the known low form drag of the liquid-cooled engine, should stimulate the development of that class of engine. How well it ^ncceeded is shown by the speeds obtained by such British fighters as the Hurricane and Spitfire. The United States, on the other hand, to all intents and purposes dropped the liquid-cooled engine, with the iestrit that to-day America has but a single high-power •ngine of this type, the Allison. But she did pursue a vigorous research policy, and recently the N.A.C.A. iipears to have evolved a system of ducting and cowling : radial air-cooled engines which brings the drag down -i that of the liquid-cooled of the same power. Thus our ' usins on the other side claim to have caught up with; -- in air cooling against our liquid cooling, or, as we1 nuld rather express it, direct cooling against indirect for both forms are air cooling in the end. Some American ViewsL ITTLE has been heard of the details—ways and ^ means—of this American research, but in a paper presented to the Engineers' Club of Philadelphia at the end of last year Mr. J. C. Hunsaker, of the Massa- chusetts Institute of Technology, world-famous as the M.I.T., referred in no uncertain terms to the benefits that have accrued from the results of the N.A.C.A. research. " In its Langley Field wind tunnel;" Mr. Hunsaker said, " the National Advisory Committee has developed means of streamlining (ducting and cowling) the American radial air-cooled engine so that its drag can be made as low as that of the best liquid-cooled engine installation. Thus, recent technical progress has enabled American airplane builders to demonstrate airplanes with larger air-cooled engines at speeds exceeding 400 m.p.h. There now appears to be nothing to choose, as to speed, between the two types of engine when each is properly installed. This statement could have been true several years ago, but the results of research were available cnly recently." About a month after Jerome Hunsaker's paper, the assistant director of research of the United Aircraft Corporation presented a paper to the Airplane Design Section of the Institute of the Aeronautical Sciences (the American equivalent of our Royal Aeronautical Society) on the subject of air-cooled versus liquid-cooled engines. The first part of that paper is published in Flight this week. Mr. Lee finds that the air-cooled is slightly better than the liquid-cooled engine on fuel consumption at cruising speed, although at full throttle the latter is more economical. He also refers to the N.A.C.A. low-drag cowling, and having demonstrated, to his own satisfac- tion at least, the equality of the two classes in the matter of cooling drag and fuel consumption, proceeds to set off the low form drag of the liquid-cooled against the low specific weight of the air-cooled. He finds that on
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