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Aviation History
1928
1928 - 0502.PDF
JUNE 21, 1926 THE WESTLAND "WAPITI Bristol " Jupiter VI " Engine THE " Wapiti," designed and constructed by the WestlandAircraft Works of Yeovil, is of the type known as a " General Purpose " machine, i.e., suitable for bombing, reconnaissance,photography, wireless and advanced training. It can be supplied either in composite timber and metal constructionor as an all-metal machine. In both cases the wing covering, and that of control surfaces, fuselage rear portion, etc., is fabric. In its general design the " Wapiti " is a normal two-baywire-braced biplane, and in view of the ample stowage accom- modation which its function as a general purpose machinerequires, it is of remarkably small dimensions and " clean " design, with a very good performance. The amount of gearthat has to be carried in a machine of this type is prodigious, and it is to the credit of the Westland designers that they havemanaged to provide all the space required while still retaining such a good performance. In the lay-out of the " WTapiti " a great deal of attentionhas been paid to the subject of view. Thus it will be seen that the deck of the fuselage is raised considerably, bringing thepilot's head up to a level where he can look either over or under the top centre-section, the cockpit being so far aft that and longerons is by means of flitch plates, so that repairs are arelatively simple matter and require no very careful fitting by hand. At the joints the stresses are not taken on the buttends but on the rivets, which are designed with sufficient bearing area to take the loads. As already mentioned, the rear portion of the fuselage is,in the composite machine, a wooden structure braced by tie rods. The top and bottom portions are covered with plywood,thus forming rigid members. The front portion of the fuselage is covered with aluminium sheet, with longitudinal corru-gations to give stiffness. Where it is necessary to gain access to the interior of the fuselage or to the engine components,cowling panels are arranged to be detached by means of special flush-fitting clips. The wings of the composite type of machine are ofnormal construction, with spars spindled out to an I section and built-up wooden ribs of normal type. The inter-plane struts are of spruce, and streamline in section. If desired, the " Wapiti " can be supplied fitted with the newHandley Page automatic wing tip slots, which enable lateral control to be maintained in the stalled condition. THE JWESTLAND " WAPITI " : This side .view gives^a good idea of the general lines of the machine,which is a General-Purpose aircraft, fitted with Bristol " Jupiter VI " engine. It can also be supplied with " the Jupiter VIII," when the performance is considerably improved. the small cut-out in the trailing edge provides an unobstructedview upwards. The gunner, being placed relatively far aft, has an excellent view in all directions. Features such asthese, coupled with the good performance, ample stowage space and general simplicity of construction and reduction inmaintenance cost, were doubtless instrumental in securing the order for "Wapitis" which the Air Ministry has placedwith the Westland firm. At the moment it is rumoured that one of these machines is to be placed at the disposal of HisRoyal Highness the Prince of Wales, and it would probably be difficult to find a machine better suited to the carrying of apassenger whose life is so valuable to the Empire. Constructional Features [' The fuselage of the Westland " Wapiti " is built up of threeunits, comprising the engine plate and first bay, the portion from the first bay to aft of the pilot's cockpit, and thence tothe stern post. In the composite machine the first two units are of metal construction, the rear section having woodmembers and being braced by tie rods and, in places, by the plywood covering. In the all-metal machine the rear portionis also of metal construction. The first two fuselage units are built up of square-sectiondrawn Duralumin and steel tubes, steel being employed for the most highly stressed members. The assembly of struts The ailerons are of the Bristol-Frise type, in which thebalance is obtained by locating the hinges some distance back from the leading edge of the aileron. This type of aileron isbecoming very popular indeed, and is to be seen nowadays on a large number of British aircraft. In the " Wapiti " theailerons are balanced statically as well as aerodynamically. In the all-metal type of machine, the wings and ailerons are ofmetal construction, but no details are available concerning the forms of construction employed. The tail units of the composite and all-metal types areinterchangeable, and in both the front spar forms the hinge while the rear spar is actuated by the trimming gear, whichgives a range of angular movement of 7 degrees. The rudder is of large area, and has a horn balance making it very light inoperation. The undercarriage is of V-type, with the front legs acting asradius members and the rear legs telescopic. The front legs are circular section steel tubes with wood fairings, while theoleo legs are faired in by ribbed aluminium casings. Of the patented Westland oleo-pneumatic type, the telescopic legsare capable of having their capacity for absorbing shock varied according to the weight of the machine. Owing to therelatively low air pressures employed; this type of oleo leg has proved very satisfactory in use. There is no difficulty inkeeping the legs airtight, and little attention is needed. 458
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