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Aviation History
1928
1928 - 0803.PDF
AUGUST 30, 1928 THE A.D.C. "CIRRUS" MARK III ENGINE Rated at 85 B.H.P. at 1900 R.P.M. So excellent is the reputation for reliability which the "Cirrus"Marks I and II have established that one is justified in expect- ing that the latest of the series, the Mark III, recently pro-duced, and which like the earlier models passed tlie Air Ministry type tests at the first attempt, will worthily upholdthat reputation. The " Cirrus " Mark III has been produced not to take theplace of the " Cirrus " Mark II, but as an alternative engine for use in cases where slightly greater power is desirable,such as, for instance, for seaplane work, for flying in hot climates, or from aerodromes situated at a considerablealtitude above sea level, when the performances as regards take-off and climb is to be retained. The " Cirrus " Mark III, it may be recollected, made itsfirst appearance in public in the King's Cup Race this year, when two engines were entered in standard " Moth " and Avian " light 'planes. The course for this race was oneof 1,096 miles around Britain, and both " Cirrus " III engines completed the course flying at full throttle all the way. Onits second public appearance the ' Cirrus " III won first prize and a challenge cup at the Halton Air Pageant, so thatit will be seen that the engine has started its career very well. Incidentally, it may be mentioned that A.D.C. Aircraft, Ltd.,are in a position to commence deliveries of the Mark III " Cirrus " at once. Lest it should be thought that the " Cirrus "III is anentirely new engine, we would point out that this is not so, and that in point of fact those wishing to do so can havetheir Mark II engines converted, the main changes being different cylinder heads giving better cooling, larger valves,and a higher compression ratio. The Mark III engine, although developing greater power, is of the same weight asthe Mark II, and the price is the same. Thus prospective customers are able to choose whichever model is likely to suitthem best, knowing that the question of price does not arise, while the fact that the two models are of the same weightmeans that either can be installed in a machine, without necessitating any changes to bring the trim of the machineright. The two views of the engine show the clean appearance withvery low frontal area, and in the side view the new cylinder heads and valve gear are clearly visible. The power andconsumption curves give the majority of the information required by aircraft designers, so that it should be unnecessary 95 90 85 a. LJ S. 80 CO a. 70 65 ; / A ' LBS PE q L- 5Q IM , / /I : : ; \; 121 Sa. _i 74 a 70 § r UJ •5ft % 1500 1600 1700 1600 1900 2000 2100 "• R.P M. The " Cirrus " Mark III Engine : Power, consumption and M.E.P. curves. THE NEW " CIRRUS " MARK III ENGINE : Exhaust side and front views. Note the new type of cylinder heads, etc. 747 D
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