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Aviation History
1950
1950 - 0434.PDF
View forward from plenum chamber, showing duct bifurcation. Supermarine 510 aircraft, like the Seafire and Seafang complements of Spit- ?fire and Spiteful, was destined to be developed into a Naval type and, in fact, production is now being geared up at the Vickers-Supermarine factory at South Marston. The first batch of production Attackers can, therefore, be expected to be delivered to squadrons within the next few months. So excellent a body design and power installation was obviously an extremely convenient, as well as an appro-" priate, foundation upon which to base full-scale experi- mentation with swept wings, and in 1945, when the need for flight investigation into high-speed phenomena was re- cognized as a matter of no inconsiderable urgency, the Supermarine company started on a design study for an Attacker fuselage equipped with swept wings and tail sur- faces. This led to the issue of an official specification and a development contract for two aircraft and, just one yeas and nine months later (on December 29th, 1948) the 510, as the new aircraft was designated, made its maiden flight in the hands of Lt.-Cdr. Michael Lithgow, the company's chief experimental test pilot. A fully detailed description of the Attacker was pub-» lished in the May 15th, 1947, issue of Flight, but in order to refresh readers' memories as well as to serve those who did not read the original article, a brief recapitulation of the salient features of the fuselage structure and layout—» as it exists in the 510—may be of value. In fundamental shape, the fuselage is a solid of revolu- tion in the form of an ellipsoid with a fineness ratio of 7.8:1. The basic shape is, however, modified by the neces- sity to provide intakes for the Nene, a canopy for the cockpit and a hole for the jet efflux, but despite these imperatives—or, rather, as a result of the excellence of their design—the deformation of the ideal is slight. The fact that the fuselage tail is cut short for the jet-pipe outlet puts the fineness ration of the body up to 7.5:1, but this is in part compensated by an addition which modifies the basic shape in rather a startling way—namely, the "needle" nosecap. Probosces of this type in greater or lesser exaggerated forms were introduced in the U.S.A., but we believe we are right in stating that the primary pur- pose was the root fairing—and strengthening—of a pitot- head extension. At the present time, the 510 carries its pitot-head on the port wing-tip but that this may be trans- ferred some time in the future to the nose extension is not impossible. For the moment, however, the nose point of the aircraft is put to no definite purpose, although its intrinsic shape may well provide some aerodynamic advan- tage ; this is a matter of some uncertainty but, aero- dynamically advantageous or not, the 510's detachable beak is aesthetically arresting and certainly does not de- tract from the very beautiful lines of the aircraft. The way in which the fuselage form was actually de- cided is rather interesting. In the initial instance, a maximum diameter of 6oin was fixed as being the smallest dimension which would accommodate the Nene. In con- nection with this, the position of the wing spars was then ietermined, which in tunr dictated the requisite position of the tail surfaces and the cockpit. Hie result was a general determination of fuselage length in relation to diameter, and the actual curvature of body form was selected on this basis from a survey of the rjppt data relat- ing to form drag available at the time. Structurally, one of the more unusual features of the 510 (and the Attacker) is the transition between cockpit and fuselage proper. In side elevation, there is nothing unusual in appearance, but in plan it at once becomes evident that the cockpit is, in fact, virtually a separate little nacelle, cantilevered from the main fuselage body. This, of course, arises from the presence of the intake trunks which, passing behind the cockpit, necessitate a break in structural continuity. The space between and on each side of the inlet ducts is devoted to fuel-tank stowage and, therefore, the top skinning of the fuselage immediately aft of the cockpit is fashioned as a tank- access door. In view of the cantilevered cockpit, however, this door had to be designed as a stressed member, for which reason it is fastened to the bounding frames and longerons by healthy-sized screws which accommodate the shear loads involved. The skin plating of the cockpit / fuselage underbelly is continuous and, therefore, helps in some measure in the accommodation of the cantilever moment, but the very size of the intake orifices means that the degree of cockpit load-transfer shared by the skinning around the inlets is relatively small. In view of the contemporary interest in flush intakes, a certain amount of argument has arisen as to whether the intakes used on the Attacker and 510 can justifiably be regarded as being of flush type. Certainly, if the maximum- beam line of body curvature in plan form is continued across the intakes, it is seen to support the " pro" side of the argument; there is, in fact, little doubt that, if the top and bottom fillets of the intake orifices were extended forward in conformity with the curvature of the body, the intakes would undeniably become flush. Whatever the merits of the intake form may be in deserving one or other appellation, the fact remains that they are admirably suited to the duty required of them; that the intake efficiency at the plenum chamber entry is well over 90 per cent is well worthy of note. The cockpit nacelle is itself unusual in being of '' lobster- claw " construction, in light alloy sheet 0.56m thick. The nose volume ahead of the rudder pedals provides ample stowage space for the (relatively) very large automatic observer and variety of test instrumentation. As to cock- pit layout, there is not a great deal to be said beyond remarking on the neatness and care which have patently been exercised in its planning.; a Martin-Baker ejector seat is fitted. The screen and canopy arrangement is, however, somewhat unconventional. To take the screen first, this is a Jin-thick multi-ply glass sandwich which is, of course, optically flat and bullet-resistant, but in front of it is fixed a fin-thick compound-curved glass fairing-panel, by means of which the aerodynamic properties of the cockpit cover- ing are usefully enhanced. The flanking screens and the jettisonable canopy proper are all fabricated in blown Perspex and, equally, are all of double-cavity-wall con- struction. The purpose of this elaboration is to mitigate the effects of misting, and toward this end the inter- Perspex cavities breathe into flexible reservoirs through silica-gel desiccant packs. Anti-misting qualities are also Gantry in rear fuselage to facilitate jet-pipe installation
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