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Aviation History
1942
1942 - 0702.PDF
306 FLIGHT APRIL 2ND 1942 MAINTAINING THE AMERICANS craft or engine on, which they are working. These are, of course, fully trained in their trade and it is only differences of practice which have to be taught. When they return to their units they are able to supervise periodic overhauls and remedy snags peculiar to their machines. The fortnightly intake is completed by the attendance of a number of engineer officers, civilians from maintenance units and some flight engineers from squadrons who fly such aircraft as Consolidated Catalinas or Cyclone-engined Stirlings. Main Differences Many are the differences between American and home- produced aircraft and engines. In the same way that every different brand of car requires some different technique for starting, so the American engines have a temperameut all their own. Such differences are, however, small, and it is only in a few instances that the divergence of practice assumes major proportions. Ttiese major differences come under six heads: It has been our standard practice to test- sparking plugs under a pressure of 120 lb./sq. in. ; the Americans employ a pressure of 180 lb./sq. in. Automatic boost control is not yet fitted to any of the U.S. engines, either to the air-cooled radials or to the liquid-cooled Allisons. This is shortly to be corrected, but at the moment it looms as one of the biggest differences in engine opera tion. Then there are the principles of the Stromberg in-- jection carburettor to be learnt. This carburettor is fundamentally different from standard types in that the fuel is pumped directly into the intake air stream instead of being sucked in by the passage of air through venturi tubes. The fuel injection carburettor is of very great use to the operational fighter pilot because there is no cutting out by the effect of negative "g" if the aircraft is put into a steep dive. In addition, it gives the smooth running of an ordinary aircraft engine which cannot be obtained by the Germans with their system oi injecting microscopic amounts of fuel into each cylinder separately. The German engines are invariably rough owing to slight variations in the quantity of fuel injected. Another type of carburettor which is fitted to some of the lease/lend radials is the Holley. It works on the The Boston hydraulic system being demonstrated by an instructor. Mr. E. R. Collins, the chief instructor, is looking on. The Stinson O-49, which is a tully slotted and flapped observa tion type. Maximum speed 133 m.p.h., minimum speed in !evel flight 31 m.p.h. Take-off over 50ft. obstacle—130 yds. normal venturi principle but it has variable jets and vari able choke tubes, both of which are automatically operated by the throttle. Tricycle undercarriages—steerable or non-steerable—are (Above) A Curtiss electric airscrew class. (Below) An instructor explaining to pupils how the blades of the exhaust- driven turbine are each made separately and keyed into the rotor.
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