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Aviation History
1927
1927 - 0168.PDF
20 MARCH 10, 1927 ARMSTRONG - SIDDELEY "JAGUAR" BRISTOL 'JUPITER IV" Supepchapqed BRITISH ENGINES IN SERVICE : The ,radial air-cooled engines in use are primarily represented by the two shown above. On the left, the Armstrong- Siddeley "Jaguar," and on the right the Bristol "Jupiter" (Series IV, Supercharged) " Horsley " (the machine with which the attempt is to be made) is the Rolls-Royce " Condor." As Rolls-Royce aero engines have ever had a reputation for reliability and low fuel consumption, it is permissible to be optimistic as regards the success of the attempt. The 450 Napier " Lion " Probably no other aero engine has ever enjoyed such world- wide popularity as the Napier " Lion." First produced towards the end of the war, 1914-18, this engine arrived too late to take an active part in the war, but during the years following the war, the " Lion " very quickly established a reputation, and during the last few years a greater number by far of " Lions " have been produced than of any other British aero engine. In fact, except for the " Liberty," it is doubtful whether any aero engine has been produced in such large numbers as has the " Lion." The Napier " Lion " was the first aero engine of the " W," or " broad arrow " type to be produced. The arrangement of the twelve cylinders in three banks of four each makes for a very short and compact power unit. Not only so, but the specific or unit weight of this type of engine is very low, a fact of the utmost importance in service aircraft. The Napier " Lion " has reached at least the Series VIII stage, among which variations it may be of interest to state that the Series V and VI include supercharged engines, as does also the " Lioness " type, in which the crankcase is on top, the three cylinder banks hanging down below it. The object of the " inverted " engine, as it is called, is mainly to provide a better view for the pilot. The standard type of Napier " Lion " is a geared engine, but direct-drive types of 600 h.p. are also produced, both for service purposes and for racing. Thus, two of the three machines built for the Schneider Trophy seaplane race are fitted with direct-drive Napier engines. The 400 h.p. Arm strong-Siddeley "Jaguar " One of the most remarkable features of recent years has been the remarkable progress made with the radial air- cooled engine, a type that may be said to be a post-war development. In the early davs of the radial engine the type was looked upon rather with distrust, and for a time the development work was slow and difficult. By now, however, it can definitely be said that the radial engine has proved its worth, and is in every way the equal of the water-cooled type in power and reliability. The Armstrong-Siddeley " Jaguar " is a radial in which the 14 cylinders are arranged in two rows of seven each, the cylinders of the back row being placed opposite the gaps between the cylinders of the front row. This makes for a very compact arrangement and relatively small overall diameter. The engine is used in a number of service types of machines, as will be gathered from a perusal of the pages dealing with aircraft. The " Jaguar " has reached at least the Series IV stage, which is produced both as a normal naturally-aspirated type and as a supercharged engine. Our photograph shows the normal type. Finally, it will be recollected that it was the " Jaguar " which was used by Sir Alan Cobham in his famous flights to Cape Town and back (and to Australia and back, so that apart from its work in the R.A.F., the engine has proved itself in flying of a different character. The 450 h.p. Bristol "Jupiter " As already indicated, the Bristol " Jupiter," which has reached the Series VI stage, is a nine-cylinder radial air- cooled engine, with its cylinders arranged in a single row. As there are but nine cylinders, each of these develops 50 h.p. or so, and it is a remarkable testimony to the skill of Mr. Fedden, its designer, and to the workmanship of the Bristol company that, in spite of these powerful impulses, the engine runs smoothly and stands up to its work remark- ably well. The small number of cylinders has the natural advantage that there are relatively few moving parts, and the engine is, therefore, exceptionally easy to overhaul. The " Jupiter " is fitted in a large number of service types of aircraft, and, in addition, it was the type of engine fitted in the three-engined de Havilland " Hercules " on which Sir Samuel and Lady Maud Hoare made their successful flight from London to India. The " Jupiter " is produced both as a normal engine and as a supercharged. The photograph of it shown on this page illustrates the supercharged type. As supercharging has been mentioned repeatedly in these notes, it may be as well to explain to the non-technical that supercharging consists in forcing into the cylinders a greater quantity of explosive mixture than the engine would naturally draw in. Usually this charge is forced in by means of a blower placed in the induction system, and driven by a fan rotated by the escaping exhaust gases. The object of supercharging an engine is to enable it to maintain its -power at great altitudes. 148
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