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Aviation History
1941
1941 - 0881.PDF
(tnJ 'AIRCRAFT ENGINEER FIRST AERONAUTICAL WEEKLY IN THE WORLD •• FOUNDED mo9 Editor C. M. POULSEN Managing Editor G. GEOFFREY SMITH Chief Photographer JOHN YOXALL Editorial, Advertising and Publishing Offices: DORSET HOUSE, STAMFORD STREET, LONDON, S.E.I Telegrams : Truditur, Sedist, London. Telephone : Waterloo 3333 (35 lines). 8-K>, CORPORATION ST., COVENTRY. Telegrams : Autocar, Coventry. Telephone: Coventry 5210. GUILDHALL BUILDINGS, NAVIGATION ST., BIRMINGHAM, 2. Telegrams: Autopress, Birmingham. Telephone: Midland 297 1 (5 lines). 260, D E A NS G ATE. MANCHESTER, 3. Telegrams : Iliffe, Manchester. Telephone : Blackfriars 4412. 26B, RENFIELD ST., GLASGOW, C.2. Telegrams : Iliffe, Glasgow. Telephone: Central 4857. SUBSCRIPTION RATES: Home and Abroad : Year, £3 10. 6 months, Registered at the C.P.O. as a Newspaper. £1 10 6. 3 months, 15s. 3d. No. 1686 Vol. XXXIX. APRIL 17th, 1941 Thursdays, One Shilling. The Outlooks Contrd'props '•;I ^HE knowledge, now officially released, that engines iM have come into service which develop somewhere around 2,000 b.h.p. revives the associated problems of how best to convert that tremendous power into thrust. That three-bladed and four-bladed variable- pitch airscrews are in existence which absorb this high power with good efficiency is known, but it does appear likely that it will become necessary to look even farther than that. In this connection one is reminded that many years ago the Italians employed two co-axial airscrews run- i.ning in opposite directions. The outfit was used on the Macchi-Castoldi seaplanes of the Italian High-speed Flight and a world's speed record was established. The great advantage, in this particular application, was that there was not the "swing" associated with orthodox airscrew arrangements, as the opposite rotations took the twist out of the slipstream and did away with that enormous torque-reaction which caused our Schneider Trophy seaplanes to start their take-off runs at right angles to the wind. On single-engined landpianes the problem is not quite so serious. For one thing, the torque-reaction does not cause one wheel to dig in, in the way it caused one float of a Schneider seaplane to dig in, but the tendency to swing is still there. Even in twin-engined aircraft such a tendency exists, and with the powers now available, the forces to be met are greatly increased. Thus there would seem to be good cause not to overlook the claims of double airscrews. There are other aspects of the problem which come into the picture, airscrew size and diameter among them. Obviously, if one uses two airscrews to absorb the power, each is called upon to deal with only one-half the power, and a small diameter and lighter airscrew can be em- ployed. It should not be necessary to go abroad for ideas in this direction, for it is now many years since the Fairey firm began development work, and the Fairey "contra-props ". were on view at more than one R.Ae.S. garden party. Presumably the firm would, if requested to do so, design double airscrews to absorb the greater power of the modern engines. Gearing would, of course, have to be provided on the engines. In the BalkansT HE Germans have started their operations in the Balkans in typical fashion by heavy air raids on Belgrade. It had been declared an open town, but when the enemy are Germans such a declaration has no value. The wireless from the Yugoslav capital has made the statement, "In the ruins of Belgrade a greater capital of all Southern Slavs is to be erected." This suggests that the devastation must be of a very widespread nature, and it is probable that in this first experience of German air attacks the preparations in the city for dealing with fire bombs were not highly organised. The first serious raid by fire bombs on the City of London found our own preparations far from perfect, although the Luftwaffe had been showing its hand over Britain for many months ; so we may con- clude that Belgrade suffered badly. On the other hand, the R.A.F. has begun its Balkans campaign in heartening fashion. The raid on Belgrade was promptly answered by an attack OH Sofia, the capital of Bulgaria, in which the main railway station and other military objectives were heavily bombed. R.A.F. fighters, too, soon gave the advancing Germans a taste of their quality. A small formation of Hurri- canes found thirty Messerschmitt 109s over the im- portant Rupel pass on the Struma river in Bulgaria. The Hurricanes promptly attacked and definitely shot
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