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Aviation History
1955
1955 - 1623.PDF
740 FLIGHT, 11 November 1955 RECONNAISSANCE SYMPOSIUM ... and — latest of all — the Vickers-Supermarine Swift F.R.5.Also apparent is a new trend in P.R. methods. Pilots, it is disclosed, are no longer always instructed to let their cameras"run free" while they are over enemy territory, but rather to photograph the target area only. This, together with increasedselectivity in the processing units, considerably reduces the time delay between the landing of the aircraft and the arrival of targetinformation at the intelligence centre of the striking force. The principle of reconnaissance is now such that in the face of modernweapons a few photographs of the right area at the right time can be worth more than the 120,000 required for the launching ofthe final offensive in Italy. The official statement continues: "Progress is also being madein the problem of bad weather. It has been worked out that daylight photography is limited to one-sixth of the month becauseof bad weather, but that the period for night photography is considerably longer. There is, therefore, a new emphasis on thedevelopment of night reconnaissance and the subsequent use of flares." The chairman of the conference, A. Cdre. P. G. Wykeham-Barnes, Assistant Chief of Staff, Operations, at Headquarters, AAFCE, Fontainebleau, commented on the excellent co-operationof members of the symposium, and the enthusiasm which was indicated by observers from other countries. He added that ithighlighted the conception of NATO's success in all fields. The statement earlier referred to is the first official intimationthat Swift F.R.5s are now in service. Powered with a reheat Rolls- Royce Avon, this mark of Swift carries nose-mounted cameras andis armed with two Aden guns. Internal fuel capacity is supple- mented by a 220-gal tank beneath the fuselage. Another view of the composite reconnaissance formation wherein the plan farm of each aircraft (particularly of the Swift F.R.5) is seen to advantage. The RT-33A is a comparatively little known type and has only recently been introduced into Europe. It carries four cameras and a wire recorder and is a direct development of the T-33 trainer. THE ELECTRA'S STRUCTURE CINCE the description of the Lockheed L.188 Electra which we^ published last week went to press, certain additional details of the structure of this aircraft have become available. Accordingto Aviation Week, Lockheed have taken great pains to evolve an airframe with fail-safe characteristics, i.e. so to design the struc-ture that, if any member were to fail, the remaining local structure would be capable of carrying all normal flight loads.It is stated that this principal has been "fostered and encouraged in a personal crusade by a few men in the industry. Most of thecredit for leading the crusade goes to Richard V. Rhode, of the executive staff of the N.A.C.A." As described last week, the Electra wing is a relatively straight-forward box, with two main spars which are machined, extruded webs stiffened by vertical sections riveted on at frequent intervals(see inset diagram). Both upper and lower skins are machined from large slabs of high-strength light alloy to form integrallystiffened panels. In conformity with the fail-safe precept, these panels are limited to a chord of 20 inches; adjacent panels are lap-jointed and attached by a double row of flush rivets, the panel depth being sufficient for proper machined countersinking. Asa result, any crack appearing in a skin panel is confined to that panel, the remaining skins being quite capable of handling theflight loads alone (upper skin in compression, lower in tension). Even the spars are not continuous over the full depth of thewing, although it will be noted from the sketch that the caps Detail of the Electra wing, showing the manner in which both spars and skin are made in sections separated by crack-stoppers. of the spars do form the local wing surface, so making for a sectionmodulus of high efficiency. Each spar consists of upper and lower portions, riveted together along a lap joint. It seems to beLockheed's intention to enable either the upper or the lower half of the spars to function independently (at least in lg flight)in the event of failure of the other half. This would seem to be a difficult target, bearing in mind the wing loading of up to85 lb/sq ft and the very restricted depth of the high-speed section employed. In the fuselage an even more unusual formula has been chosen.The basic structure of the pressure hull is a fairly conventional circular-section assembly of transverse rings (of 136in outsidediameter) and longitudinal stiffeners, but on to this is riveted an over-all grid of sheet metal, inside the final skin. This grid isriveted to the skin over the entire area of the latter (except for regions of insignificant stress, such as the nose) and formsa crack-stopping network. It also carries some of the flight and pressure loads and thus reduces the stresses borne by the skin. In our description we commented on the fact that the 12-stepintegral stairway was housed in an unpressurized box, the outer door (the lower portion of which is part of the stairway) takingonly aerodynamic and inertia loads. The box is formed by a pair of structural semi-bulkheads, and the inner wall incorporates astrong frame for the pressure-bearing entrance door (see large cut-away drawing published last week). The other doors, suchas those for emergency exit at the rear and to provide access to the underfloor holds, are structural and pressure-bearing. Curiously, the windows are not of the optimum form whichBristol have developed for a pressurized, circular-section hull; they are not even simple ellipses. On die other hand, Lockheedemphasize that the straight sides are joined by generous radii at the corners, and the resulting design is claimed to give a lowoperating stress and to fit in well with the general fail-safe precept. Although not directly connected with structural considerations,it is apposite to note a change in Lockheed thinking with regard to the flight-control system. Originally, the Electra was to haveused a manual, aerodynamically boosted system for all primary control surfaces. The latest reports on the aircraft speak of afully-powered system, with duplicated hydraulic actuation. If this is indeed so, it marks an unexpected failure on Lockheed'spart; on the other hand, it may be that powered controls will be required only for the C.A.A. tests.
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