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Aviation History
1944
1944 - 0127.PDF
JANUARY 20TH, 1944 FLIGHT 65 THE HAWKER TYPHOON Hawker designers are not '' wedded''. to any one system of construction. Rather does one form the impression that any particular component part of the primary structure is of the type of construction best suited to its special function. There is thus what might appear superficially to be an apparent lack of homogeneity in the structure, but always, if one looks deep enough, there is a very -good 'reason for every change in structural methods. No better example of such design considerations could be found than the fuselage. The front portion, from en gine bulkhead to behind the pilot, is of girder construction, while the rear portion of the fuselage is a stressed- skin shell with flush riveting and a smooth surface. Even the front por tion, when covered, is as nearly smooth as possible, although some slight roughness is inevitably intro duced by the removable panels which give access to the maze of equipment stowed inside. Fuselage Accessibility From the aerodynamic point of view the ideal would probably be stressed- skin construction throughout, but there are very excellent reasons for not using it in the front part of the fuselage, where all, or nearly all, the equipment is located. In an aircraft of the size of the Typhoon it would be well-nigh impossible to install all the "plumbing." There simply would not be room for the men to move. It might be argued that one of the several forms of '' split'' construction used in larger aircraft types would get over this difficulty. While that is probably true to some extent, during the process of manu- «. facture and assembly in the shops there is the subse quent service life of the air craft to be considered. Any defect in a piece of equip ment, either through break down or through enemy action, would be exceedingly difficult, not to say impos sible, to put right because of the inaccessibility of the part in question. Doubtless it was such considerations that led the designers to choose girder construction for the front part of the fuselage and to cover it, when all equipment has been installed, with sheet metal panels, some fixed and others detachable. During installation of equipment the men can reach through the girder work from the outside, and in service there is access by removing the detachable panels. Use is made in the primary structure of the front part of ^fhe fuselage of steel and light-alloy tubes, some of cir- (Above) Part-sectioned view of the Dowty tail-wheel strut. (Below) The undercarriage ex tended and retracted. The hinge 10th in the horizontal wheel cular section with flats formed where other structure members are attached to them (in the time-honoured Hawker way), and some of square section with rounded corners. The Typhoon is no light aircraft (the loaded weight goes up to somewhere in the neighbourhood of 12,000 lb. when two 500 lb. bombs are carried), and conse quently the concentration of stresses in this part of the fuselage is considerable. Some of the main tubes of the structure are of about 3m. diameter, and in the case of those on which the wing spar attachments pick up, the ends are housed in even, larger forgings which terminate at their outer ends in fork ends for the reception of the tapered' bolts which secure the wing spars to the fuselage. The rear fuselage portion (it is actually built in two units, the rearmost of which has the fin built integrally with it) is, as already mentioned, of stressed-skin construction. The main frames are of box section, with channel-section walls, a covering strip on the inside, and the skin forming the covering on the outside of the frame. Light inter mediate frames are of " figure 2 " sec tion, with the foot of the " 2 " riveted to the skin. The stringers are of '' rounded vee'' section and are notched into the frames. An excep tion to this scheme is found in the main frame by which the concentrated loads from the girder portion are spread into the shell of the rear por tion. This frame is not notched, the stringers being cut here. A system of triangulating tubes, secured at their rear ends to points on the main monocoque frame, converges on four points, which pick up on the
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