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Aviation History
1947
1947 - 1436.PDF
224 FLIGHT August 28th, 1947 Aerofoil flap and aileron. The latter can be drooped to give flap effect whilst leaving their normal function unaffected. trimming "rudders" are displaced, say, to port, the central rudder .will take up a " no-load'' position also dis- placed to port, albeit slightly, or whether it will remain centred on the fuselage axis. In any case, the consequent displacement of the rudder proper—if any—would be so slight as to be unnoticeable to the pilot, in precisely similar a fashion as obtains with the conventional trailing-edge trim tab. The trimming surfaces are independ- ently yet simultaneously operated by Miles elec- tric actuators carried in the tailplane, such units also serving a similar purpose for elevator trim- ming; they are controlled .by operation of a rocking and rotating switch behind the throttle box in the cockpit. Normally the Merchantman has provision for an aircrew of one, the pilot, but should it be desired, dual control could easily be furnished or, alternatively, provision made for a navigator/ radio operator; there is plenty of room. Cockpit layout is good and very convenient. There is but • one novel feature here and it is surprising that it has not occurred before. Quite simply, it is uniting under ^ne control the fuel cocks and the idler cut-outs; when the cut-outs are operated to stop the engines, the fuel cocks are closed—simple, effective, and so far as we can see, without snags. Of the field, of view, it is sufficient to say that it is of the same high order as that provided in the Aerovan. Before going on to consider structural features of the aircraft, space may be devoted to an ap- praisal of the undercarriage. It is in the Aerovan class for simplicity and, in fact, is broadly simi- lar although differing in detail. The nosewheel is pivoted on a-cantilever axle from an overhung fork-arm, lie oleo strut being anchored in a box formation integral with the nose structure. It is steerable through a mechanical linkage from the rudder pedals or, at will, may be unlocked for operation as a castering, self-centring unit. Port and star- board main units are duplex, each pair of wheels being mounted on a swinging arm supported in three plain bear- Everything is convenient// arranged in the wefMaid-out cockpftv ings in the fuselage floor structure. The bearings are carried in the wall and in division members of a box structure which, additionally, houses the twin oleo-pneumatic shock absorber units. Since these are below floor level no useful stowage space is sacrificed, yet access for maintenance is very good. Wheel braking is of the single-idisc type, and a duplicated system of pneumatic operation is provided; that is to say, outboard wheels can be braked together, inboard wheels together, or all together. Wheels and tyres are interchangeable. As stated at the beginning of this survey, structurally the Merchantman is very simple, this applying particularly to the fuselage. This is built up in the form of separate sub-assemblies comprising the floor, the two sides, the nose, the forward roof, and the door-cum-tail fairing. The slab sides are fabricated on vertical channel-section frames in- terspersed by drawn Z-section stiffeners, thus forming, in conjunction with channel longerons at top and bottom and bounding the lintel and sill lines of the windows, a g Ijj framework to which the skin is attached. Each vertii frame is joined to the longerons by fish plates. The floor structure is relatively massive and is composed of Warren Fuelling-up prior to maiden fight. girder transverse main beams and longitudinal pressed channel-section intercostals. It is, of course, stressed for heavy point-loads. Wing-fuselage attachment seems at first sight to be fairly complicated but in actual fact this is not so. The upper sides of the fuselage walls are separate sub-assemblies, which can be likened to diaphragm closure members to the wing roots, and are bounded along bottom edges with channel members which pick up the top longerons of the side panels proper. At about i\ per cent chord the "root diaphragm'' carries a vertical top-hat section post, into the base of which registers an eyebolt anchored in the fuselag1" frame at this station; this forms the forward attachm '" point. . The main spar, unlike the rear spar, spans the fuselage roof, and from its web depend two box struts, port and starboard, which extend down to connect, by means of pin joints, with built-up triangulated box frames integral with the fuselage sides. This attachment has to contend with side loads, a fact which decided its form. The third point of wing-fuselage pick-up occurs well behind the wing trailing-edge—actually at the tail boom joint. The rear edge of the " root rib " is bounded by a channel post with its web locally reinforced at the base. This is drilled for accepting the pin which anchors to it an up-projecting *ug in the fuselage frame beneath. The Merchantman wing has many points in common with that of the Marathon, apart from being of the same span and using the same basic aerofoil section. It is virtually a
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