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Aviation History
1939
1939 - 0410.PDF
154 FLIGHT. FEBRUARY 16, 1939 half engine speed, means that the full available power for take-off may be efficiently converted into thrust, while the use of constant-speed airscrews—later to be full-feathering Hydromatics—means that this thrust efficiency is available during the initial climb as well as at the take-off. Large airscrews mean also that the engine diameter is small in relation to the airscrew disc, so that little power is wasted through slipstream interference. A high-wing arrangement was chosen for a number of reasons. Those normally considered by the operator are fairly straightforward : the passengers obtain a better view, while the fuselage may be both deeper and so near the ground that there are few personal or freight-loading problems. Aerodynamically, the high-wing type has the benefit of an unbroken upper wing surface between the two engines. In this particular machine the latter are carried well below the chord line, so that there is little disturbance of airflow. This unbroken surface shows its advantages at low speeds and high angles of incidence, when the even distribution of lift over the span reduces the likelihood of vicious tendencies at or near the stall. During the take-off and the approach the characteristics are further improved by the use of Handley Page slotted flaps which increase the lift quite considerably even when they are in the fully- down (53 deg.) position. For the take-off, when they are lowered to the 25-degree position, extra lift is available with little of the usually attendant drag. it is worth noting here that with a full load the 95 can take off in 250 yd., and be at a height of 170ft. after a "run" of 650 yards. Within two miles of the start of the take-off (at a climbing speed of 100 m.p.h.), the machine can be at 1,800ft. if full take-off power is used for the period. While on the subject of safety, two other little points should be mentioned. Either one of the two engine pumps is capable of supplying sufficient fuel to both engines for maximum power. Even if both the pumps fail, the posi tion of the tanks means that gravity would still be available to provide the necessary flow. The retractable undercarriage, too, has three alter native methods of operation. If the hydraulic pumps fail there is an emer gency supply of compressed air with separate pipe-lines, while there is a stand-by hand-pump system which is independent of either. Very briefly, the structure of the Flamingo - might be described as an interesting example of the translation of wood into metal. The designers have used many of the best features of normal wood construction—at least where the fuselage is concerned—and have obviously not felt themselves bound to follow previous ideas in metal stressed-skin layout. The details are described later, but it should be said, by way of an intro duction, that one of the most im portant features in the design is the way in which accessibility and inter- changeability have been considered. For instance, the two halves of the tailplane may be reversed, while the wing, excluding the continuation of the main spar across the fuselage, is in four pieces, so that, when necessary for packing purposes, the machine's width can be reduced to a matter of 9 feet when the engine-carrying How the seating is arranged in the four different versions of the D.H.95. It will be seen that only in the twenty-seater is any structural change necessary, the rear bulkhead being moved farther aft. stub wings and the outer sections have been removed. The fuselage is built in two separate parts largely for reasons of ease of production, though the fact would reduce rebuilding time in the event of a minor ground mishap. The wing tips, too, are detachable; and these ate un doubtedly the most vulnerable parts of an aircraft. Operators who are endeavouring to make a small fleet do the maximum amount of work will be interested in the way in which the two Perseus engines are not only quickly removable but interchangeable. When one is taken out the various leads are merely detached at the bulkhead, while the accessory gear box remains mounted on the spar. An engine can, in fact, be changed in rather less than an hour. In the works the necessary jigs have been split up so that the maximum amount of work can be done on each section of the machine without the hold-ups caused by the fact that only a certain number of men can work together in one place. This splitting-up also economises floor space. At the moment several 95's are in course of construction, and the production plans are well advanced for the quan tity manufacture of the type. Passenger Accommodation .There are four different cabin arrangements for the 95. Those for twelve, fourteen or seventeen passengers may be had without extensive alterations, though the twenty-passenger arrangement involves certain structural modifications, which must be incorporated at an early stage in the manufacture of the machine. Figures by themselves do not convey any real idea of cabin size, but for what they are worth here are the main cabin dimen sions of the Flamingo: Maximum width, 7ft. 6in. (2.29 m.); height, 6ft. 7m. (2 m.) ; width of seats inside armrests, igin. (0.48 m.); and width of gangway, 14m. (0.356 m.). The length of the cabin varies with the seating arrangements, that for the twelve-seater being 15ft. nin. (4.85 m.) ; for the four- v J p—-—ri '' 1 '1 n •' • • i< V U. . . \y V ' v v v \J Ki 17 SEATS f "| fi r\ jC _)• f<1 _>. (-, r>\ ( 1 U y Luggage jd Lavatory — 1 y I * 1—t rrr*! L— v—W~\l—L H 20S c ,-h 1 1 X. pV U—U EATS f \ h—r* U 1 ' L i y pX v Lavatory and/or Luggage
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