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Aviation History
1937
1937 - 1525.PDF
JUNE IO, 1937. FLIGHT. The first Daggers in the Service : 200 m.p.h. Hawker Hec tors of No. 13 (A.C.) Squadron, which are fitted with Dagger III engines. (Flight photograph.) Some Glimpses of Napier " H"- shaped Engines in Production : Britain's Lead in a Modern Trend ACCENT on the ASPIRATE M ORE and smaller cylinders will characterise high-powered aero engines of the near future, if we are to believe the dicta of experts; the limit of cylinder size, according to these worthies, has already been reached. The arrangement of comparatively large num bers of small cylinders is a question not readily to be dis missed and must be approached in sympathy with the problems of aircraft designers over whom the spectre of power-plant drag looms larger as speeds increase. Napiers were never parochial on questions of engine lay out. For many years past they have been in production with the outstandingly successful Lion and Sea Lion water- cooled units of broad-arrow formation; in the 1,000 h.p. water-cooled Cub (circa 1926) they gained valuable data with an engine of irregular cruciform section; and in their Culverin compression-ignition unit constructed under Junkers' licence they have studied problems associated with vertically opposed arrangements. When Napiers embarked on their current "air-cooled" programme, they did not hesitate, on the recommendation of Major F. B. Halford, to set about developing two engines with their cylinders (sixteen and twenty-four in number on the respective models) disposed in four banks, two vertical and two inverted, arranged in H formation. The sixteen-cylinder unit eventually became the Rapier and the larger model the Dagger. Under these designa tions both engines have been in large-scale production for some months, while abroad, engines on similar lines are still " on the boards " or are being prepared for initial tests. Incidentally, examples of the Dagger engines have already been exported. Flight was lately privileged to see something of the work in progress at Napier's Acton works, where moderately super charged Dagger Ill's are going through for installation in Hawker Hector Army co-opera tion machines and Rapier VI's for Fairey light reconnaissance biplanes. A batch of fully super charged Rapier V's has lately been delivered to power the upper component of the Short- Mayo composite aircraft for ex perimental Atlantic crossings. On the occasion of our visit, news had just come to hand that a standard Dagger III had been put through a drastic hundred- hours' run on the dynamometer brake at maximum speed (4,000 Sqn. Ldr.. S. H. C. Gray, O.C. No. 13 (A.C.) Squadron, in his Dagger-engined Hector. This view shows the countersunk ex hausts, which act as admirable flame-dampers (Flight photograph.)
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