The Aviation World

New Zealand Herald, Volume LXVII, Issue 20620, 19 July 1930, Page 8 (Supplement)

The Aviation World

AIRCRAFT DIESELS. * A SUPPLEMENTARY TYPE. The progress of Diesel engines in aviation lias reached a transitory stage, where its advocates, gratified to sec a Dieselengine aeroplane actually in flight, are inclining to over-enthusiasm in prophesying (he scope of its immediate application. The basic problems of high-speed Diesels have been solved, but a tremendous amount of detailed development work must still be done to ensure the future of the aeroplane Diesel. There arc metallurgical, production arid theoretical design problems to solve. In its present form the aviation Diesel can undoubtedly become, in a few years, an important supplement to the ordinary typo of aeroplane engine, especially in largo machines, sea planes and dirigibles. Weight-Economy Ratio. The aviation Diesel is now considerably heavier than an ordinary petrol engine, and this increased weight offsets most of its other advantages. However, as the weight is reduced, the fuel economy will help to make up for what weight handicap is left, and the Diesel will first become an important supplementary form of power to be used in large aircraft for Jong flights. A Diesel engine costs more than an ordinary petrol engine, and will continue to do so until (juantity production is attained. The fuel cost, however, is considerably less than that of a petrol engine. This, however, is not the main argument for the economy of the Diesel. For a given combined weight of fuel supply and engine, provided that the weight of the Diesel is somewhere near that of the petrol engine, the flying range or carrying capacity of a Dieselengined aeioplane is greater than that of a machine with the conventional type of motor. 'J'iiis factor is specially noticeable for flights of 500 miles and more, when fuel economy becomes an important consideration. At a conservative estimate the cruising radius or the weight-carrving capacity of the Deisel-engined machine would be from 20 to 30 per cent, greater than that of an aeroplane powered with (he conventional type d%air-cooled petrol engine, such as is most popular to day. Advantage of " Cold Starting."

It is not necessary for the Diesel engine to l)c wanned up before commencing a flight, as is ihe practice with petrol engines. All aircraft Diesels are " cokl starting." The heat of the first compression is enough to ignite the fuel, and a Diesel aeroplane can take off immediately the engine begins to turn over, although, if this is not necessary, it is just as well to let it " tick over" on the ground for a short lime. However, in cold-weather operation, in an emergency, or in military service, this " cold starting" is a factor to lie considered. Jt is difficult 1o foresee what would happen if a Diesel wore produced as light as the present types of air-cooled petrol engines, but, in view of the high degree of refinement of the types in most common use to-day, it is iiardiv likely that the Diesel will ever replace them entirely. It will, however, assume a position of ever-increasing importance where long-range reliability, weight-carrying capacity, mechanical simplicity and super" safety are desired.