pivot located at the centre of the slip table about which the combo could rotate. This enabled fast and easy plane changes to be accomplished whilst Extensive Quality maintaining the fuel pump drive in the same direction. CLose consultation between LDS and Dowty at the design Testing Required for stage enabled the necessary modifications to be made to the 964LS combo. The ABFCU was initially subjected Taiwan's Fighter to a structural resonance search on the vibration test rig in each of the three Project orthogonal planes. This search consisted of a sine sweep from 20 to 2000Hz at a maximum acceleration level of 2g, applied to the ABFCU at the mounting flange. Following the resonance searches, IN 1983, Dowty Fuel Systems tendered ments. They knew from their own the unit underwent random vibration for and won the contract for the design experience that the 964LS combo, with testing for our hour in each plane. The and manufacture of the after-burner fuel its 80kN (180001b) thrust capability, spectrum consisted of a broadband combined with a hydrostatic bearing contract unit (ABFCU) for the Garrett background vibration of 0.03g/Hz with slip table, could cope with the severe TFE 1042 turbofan, on the basis of their two superimposed narrowband spikes long experience in the development of random testing the project was going to of 1g/Hz centred around crutical engine hydromechanical aviation fuel metering demand. frequencies. During the testing the systems. Garrett Engine Division is a ABFCU was operating in a cycling leading US manufacturer of gas turbines mode with fuel operating temperatures Demanding tests for aircraft and helicopters and the held within a range of 107°C. Fuel TFE1042 turbofan was the designated The combination of such a demanding flows, pressures and temperature were propulsion system for Taiwan's new test and the complicated dynamics of all continuously monitored throughout Ching-Kuo fighter aircraft. the ABFCU, coupled with the need to the test. The ABFC for Garrett is far from drive the fuel system meant that a Finally the unit was subjected to six purpose built vibration fixture was being merely a fuel pump, it reacts to individual shock pulses per plane, three and meets the pilot's operational de necessary. The fixture needed to incor in the positive direction and three in a mands by metering additional fuel to porate a 6:1 ratio gearbox so that negative direction. Data showed the the je t pipe whilst simultaneously taking correct pumping speeds could be ob configuration for a terminal-peak saw into account rapid changes in the tained. This was driven by a variable tooth positive shock pulse with a peak speed DC motor via a flexible drive surrounding environment, such as air acceleration of 20g and a duration of pressure and temperature. shaft, capable of withstanding vibration 11ms. both radically and axially. Dowty's Vibration in the forms, sine, random The testing of the ABFCU for Garrett answer to the need for dynamic stability, and shock excitation, is a major contri is now complete, the design has been light weight and maxium internal damp butor to the operational environment of ratified and production is about to ing was to design a fixture as a the ABFCU, due to its location within begin. Ground based engine tests con magnesium casting, an effective solution the engine compartment of the aircraft. tinue at Garrett Engine Division and that finite element analysis predicted Vibration testing is therefore a crucial flight testing is being performed in would meet all the requirements. part of the design and development of Taiwan. complex systems of this kind. Testing at The specific requirements for shaking the design assurance stage is necessary along each of the three engine axes to ensure the mechanical integrity of the while the ABFCU was operating in a Ling Dynamic Systems, Royston, fuel system and its ability to function flight condition led to the design of a Herts. reliably and accurately under all working conditions. Test levels were defined by Garrett and were in line with standard US aerospace and defence specifications Lovaux win RAF Northolt contract (MIL STD 810D). It was clear from the outset that the development and qualification testing Lovaux has been awarded the contract for maintenance and support of RAF Andover, HS125 and Gazelle aircraft, based at RAF Northolt. This contract was required by this project was going to be won against substantial competition and is for a five year period commencing very demanding upon the test equipment. mid-1991. To fulfil this requirement Dowty speci This contract represents a significant step in the growth of Lovaux's outstation fied a 964LS vibration testing system engineering services in the support of the UK Ministry of Defence. from Ling Dynamic Systems (LDS) of Lovaux, based at Bournemouth International Airport, is a wholly owned Royston, Hertfordshire. subsidiary of FLS Aerospace (Holdings), the UK holding company of FLS Dowty needed the LDS 964LS Industries A/S. FLS Industries is the Danish multinational company which combo because its long-stroke configur recently acquired the business and operating assets of Dan Air Engineering. ation matched their stock pulse require Lovaux, Tel: 0202 570380; Fax: 0202 580567. AIRCRAFT ENGINEERING — March 1991 9
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Mar 1, 1991
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