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Aviation History
1964
1964 - 0717.PDF
414 FUCHT Internatioal, 19 March 1964 TESTING THE BAC *,.:- ONE-ELEVEN... Fig Ib Division of static test airframe: the tail unit strength and bird impact tests on the windscreen; crack-propagation tests on typical structural testpieces. The undercarriages of all Vickers aeroplanes (including the Spitfire, Wellington, Viscount, Valiant, and others) have for many years been designed and manufactured by the company, and— although not a Vickers aeroplane—the One-Eleven has a landing gear from Weybridge. Apart from the usual drop tests there is also a fatigue programme on a complete main-leg unit with its retraction gear and mounting pintles. (Like all the fatigue specimens, these parts are not the ones used for static testing, because there is an interaction between the stresses, whereby static stress may strengthen against fatigue, while fluctuating loads are likely to weaken a static- strength specimen.) The main undercarriage unit is intended to be taken to 240,000 cycles, or 180,000 flying hours—which is factored by six to cover the scatter pattern of fatigue, thereby equating it to the rest of the 30,000hr airframe. The overhaul period aimed at is 3,000hr, this being largely determined by wear in the smaller moving parts, glands, seals, etc. The undercarriage test rig (Fig 5) is a novel one, specially designed by BAC to apply landing loads and retraction actions automatically through an electronic control box. In all, there are 19 side, drag and vertical loads, the combination being applied 30 times in the landing cycle. For convenience, the loadings and retractions are done in groups of 4,000 at a time, starting with a sequence of 4,000 "land- Fig 3 Loading of the fatigue-test fuselage, showing the loading and, below, a dia- grammatic representation of the flight cycle Fig 2 Loading the strain-gauged tail into the fatigue test tank at Filton aea/uwn LO»ONG ON WING CENTRE SECTION LOADING ON NOSE UNOeRCAWUAGE FITTING LOADING CYCLE. ON FUSELAGE
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