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Aviation History
1925
1925 - 0269.PDF
MAY 7, 1925 THE BLACKBURN TWIN-FLOAT SEAPLANE Napier " Lion" Engine IN" our issue of April 16, 1925, we published a number of photographs of the new Blackburn twin-float seaplane used at the Blackburn flying school at Brough. This machine is a development of the Blackburn " Dart " torpedo-plane, to which it has a strong family resemblance, and it is thought purposes in the ordinary " Dart," and they have been retainedin the seaplane. Although not shown in the general arrangement drawings,the " Dart " seaplane is equipped, for school work, with landing wheels which form a permanent part of i O o o o o o o o o o o o o o o o o o o The Blackburn "Dart" Sea- plane: The machine just leaving the slip- way, the wheels not yet having been raised. O O O O O O 0 that a slightly more detailed description may be of interest to our readers. The Blackburn " Dart " seaplane has been designed as a dual-control school machine for more advanced pupils, and the fact that it is almost identical with the service machines which pilots will be called upon to fly should make it a verv valuable part of the Brough equipment. At the same time, the machine can, of course, be used for other than school work, as its high-power engine naturally enables it to carry quite a considerable load. In general design the " Dart " seaplane is a tractor biplane with two floats of boat-built construction extending aft sufficiently far to do away with the need for a tail float. The recent demonstrations at Brough showed that the machine gets on to its step very easily and that it is particu- larly " clean " in running, while showing no tendency to " porpoise." In fact, it is claimed that the machine is so well trimmed at taking-ofi speed that the pilot can take his in that they are not dropped on taking the water. These wheels are not,'however, intended as an amphibian gear in the ordinary sense of the word, and the machine is not designed to alight on land, the wheels merely being a form of trolley on which the machine is transported down the slipway into the sea, and back again on its return from a flight. It would appear that with very little modification, and not a great increase in weight, the trolley gear might be elaborated and extended to turn the " Dart " seaplane into an amphibian. The fairly small wings, the use of a medium-lift section (T. 64), and the general concentration of all heavy weights were, of course, results of considerations connected with the original machine, but are found no less useful for school work, the more so as the general behaviour of the seaplane is more or less identical with that of the torpedo-plane. Constructionally the " Dart " seaplane follows standard Blackburn lines in that it has wood wing structure and partly o o o o o o o The Blackburn "Dart" Sea- plane: Front view of the machine at the top of the slip- way. o o o o o o o o o o o o o o o o o o hands off the controls. The float volume is ample for the weight of the machine, so that not only would one float be sufficient for keeping the machine from sinking in case of puncture of the other, but the seaworthiness is, naturally, Kreatly increased. As regards general design, perhaps the only slightly unusual feature is the back-swept wings, which, although very popular in the early days of flying as a means <>f obtaining stability, are not so frequently seen on modern machines, and when they are, the object is usually connected with questions of fore-and-aft trim for a given disposition of main loads rather than with aerodynamic stability. The somewhat unusual lines of the fuselage are, of course, con- nected with the object of good visibility for deck-landing wood and partly metal fuselage. The latter is built in three sections : the engine mounting with cowling, etc., shown in a set of photographs ; the fuselage centre portion, taking the cockpits, undercarriage attachments, etc., and the tail portion. The-first two sections are of steel-tube construc- tion, while the rear part of the fuselage is the usual wood- girder structure braced with tie-rods. Some of the accompanying photographs show the steel- tube centre section of the fuselage and some of its details. The fittings, it should be pointed out, are machined from the solid, and ha've been so designed that all struts and wires meet on the centre lines, or neutral axes, thus avoiding off-set moments. The Blackburn designers consider this arrange- 269
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