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Aviation History
1964
1964 - 2019.PDF
44 FLIGHT International, 9 July 1% The big-door, heavy-floor con version of this ex-Transconti' nentat Britannia 308 took British Eagle six months to complete "Flight International" photograph EAGLE'S BRITANNIA CONVERSION WITHIN 24hr of being certificated by the ARB, BritishEagle's Britannia 308 G-ANCF was on its way to Australia on its first Ministry of Defence contract flight support- ing the weapons range at Woomera. Superficially it looked much like the 12 other long-range Britannias now operated by British Eagle, but closer inspection would have revealed that this is a unique aircraft—the one and only civil Britannia having the large freight door. It was a job which BOAC, with all their re- sources, said was impracticable, and the corporation asked Douglas to convert two DC-7Cs to DC-7F standard. Last year British Eagle bought two Britannia 308s from the Argentine independent Transcontinental, which went into liquida- tion. One aircraft had been at New York for nearly a year, im- pounded by the authorities, and the other had been lying for an even longer period at Buenos Aires. Both aircraft were flown over by Argentinian crews, and conversion of the first began in the Eagle base at London Heathrow on January 20. From an Air Ministry store, where they had long been gathering dust, were bought two spare Britannia 252 door panels, and the challenge was to convert this 308 aircraft to what in effect is a civil version of the RAPs Britannia 252. The size of the door (into which of course is incorporated the normal small crew door) is a standard 72in X 88in. With the full co-operation of the Bristol division of the British Aircraft Corporation, who provided full stress data and two struc- tures engineers to supervise the operation, the job took six months —January 20 to June 30—and a total of about 67,000 man-hours. Before the fuselage was cut the whole aircraft had to be mounted and loaded (primarily by means of a hydraulic jack on the nose leg) so that there would be no shear and no bending in the vast cut area depicted in the photograph. (The story goes that when the panel was lifted off a British Eagle mechanic called out to the man still stand- ing in the cutout: "What are you going to saw off next, Harry— the wings ?") In addition to the installation of the new door the floor beams were reinforced at their attachment points throughout the freight area so that a loading of 2001b per sq ft is permissible, with loads at the fore and aft ends of the aircraft of 1001b. Eagle carried out an investigation of the average density freight weight, coming to the conclusion that this varied between 5J-6kg per cu ft for general domestic type freight and 6£-7kg per cu ft for industrial freight. With a 6ft headroom and a density of say 131b per cu ft, loadings of no more than 801b per sq ft are likely to be experienced. Although the basic weight of the aircraft is increased by about 3001b as a result of the conversion, there are no changes in any of the manual operating weights, which remain as for the 308, and the cabin differential pressure of 7£lb per sq in also remains unchanged (the 308 Britannia differs from others in having a 19-gauge instead of an 18-gauge skin, and has always had a differential pressure lower than the normal 8.75 maximum). Of especial interest is the fact that the floor is made of ordinary marine plywood, which is much cheaper than V3 aircraft ply, and easier than a metal floor to repair. There is also the psychological thought that loaders tend to abuse metal floors, thinking they will 'Flight International" photograph Above, work on the second 308 is due to begin shortly and should be finished in October. Below, thanks to the accuracy ofBAC Bristol's stress calculations there was no "spring" when the large cutout was made in the fuselage. The aircraft was supported on five belly cradles take anything, whilst perhaps they may not be so brutal to what appears to be a floor out of a Mansion Polish advertisement. Both the Britannia 308s had very low hours, 5,600 in the case of G-ANCF (formerly LV-GJB) and only 4,337hr in the case of G-ANCG (LV-CJC). Although it had been standing out for a year, 'CF was virtually free of corrosion, and CG is only in need of moderate corrosion treatment. British Eagle have given 'CF a complete overhaul, assuming all components and equipment to be zero-life, and the whole job is estimated to have cost £150,000. With many lessons learned (for the job has not been without its. problems, particularly in the sequencing of operations) the cost of j the second conversion, including a major check, should be close to the £80,000-£ 100,000 originally estimated. British Eagle are warm in their praise for the co-operation given j by Bristol engineers. They are justified, however, in making the j proud boast that this was "one of the most significant engineering j achievements by any civil airline." I More photographs on page 46
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