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Aviation History
1997
1997 - 1995.PDF
INDUSTRY FAA approves composite repairs IAN SHEPPARD/LONDON AN AIRCRAFT-REPAIR technique developed by the Sandia National Laboratories in New Mexico together with com posites specialists from Textron Systems, has gained initial ap proval from die US Federal Avia tion Administration as an alterna tive to riveted aluminium. The bonded composite "doubler" is the result of a three-year FAA-spon- sored research and validation pro ject by Sandia's Airworthiness As surance Nondestructive-Inspec- tion/Validation Center (AANC). Traditional metal patches are relatively stiff, and riveting can fur ther magnify stresses, while mois ture can become trapped and lead to corrosion. The composite dou bler, however, is flexible and adheres evenly to the aircraft skin surrounding the damage, to form a watertight repair. A 0.2 5mm-thick tape of parallel boron fibre in an epoxy resin is repeatedly applied, pressed and heated to ensure adhesion as a multi-layer, laminated patch. Sandia claims that, with a uniform stress field, there is less risk of stress concentration, resulting in a repair three times tougher than an alu minium patch of equivalent thick ness. In addition, it can be easily formed into whatever shape the repair demands without machin ing, and can be applied according to the damage with more plies (lay ers) in a particular direction — per pendicular to a crack, for example. The composite doubler is still in the proof-of-concept stage, having undergone loading and harsh envi ronment tests at the Sandia labora tory. In December 1996 its appli cation to the door-corner of an in-service Delta Air Lines Lock heed L-1011 TriStar gained FAA approval following non-destruc tive testing(NDT), and the aircraft has since crossed the Atlantic sev eral times in a 45-day period with no flaws found. It continues to fly, to ensure integrity over time. According to the project team, the application took less than half the time of a conventional repair, and will bring many repairs within the overnight-stop timeframe for the first time, promising significant savings for airlines. The AANC hopes eventually to test the technique for repairs to fuselage joints, landing-gear bay- doors and cargo doors to build up a generic set of applications. Sandia project engineer Dennis Roach says that a further NDT inspection and a "tap" test to check for delam- ination will be conducted on the L-1011 at the end of this month. Lockheed Martin is planninga ser vice bulletin allowing other main tained to undertake the L-1011 repair shortly, says Roach. J Lucas eyes military power-by-wire applications GRAHAM WARWICK/WASHINGTON DC LUCAS AEROSPACE hopes to have identified an initial application for its power-by-wire technology by the time a 1,000h in- service evaluation of electric flight- control actuation on a US Air Force Lockheed C-141 StarLifter is completed early in 1998. The company is pursuing mili tary retrofit opportunities for its integrated actuation package (IAP) for the Rockwell B-1B and Lockheed C-5, as well as new com mercial-aircraft applications, such as the planned Airbus Industrie A3XX large airliner, says Steve Croke, director of technology at Lucas Aerospace Power Trans mission in Utica, New York. Lucas believes that its IAP is par ticularly suited to retrofit applica tions because it uses standard 115V AC aircraft power, whereas com peting electric-actuation technolo gies require 270V DC power. There are also safety concerns with using 270V DC power on com mercial aircraft, Croke says. The IAP consists of a constant- speed AC motor driving a variable- Electric actuation could make for lighter work on Lockheed C-5 Galaxy displacement hydraulic pump. Flow though the pump is con trolled by a swashplate, or tilt block, and is reversible to extend or retract the actuator. Croke says that the design results in more- constant electrical loads, without the peaks caused by stopping and starting a DC motor driving a fixed-displacement pump or ballscrew actuator. The hydraulic aileron-control system of the "Electric StarLifter" testbed has been removed and replaced with dual-channel electric actuation, driven off the existing aircraft power system. Signals from sensors attached to the C-141's mechanical flight-controls are sent to dual electronic control-units which drive two dual-channel LAPs, one for each aileron. Croke says that operation of the electrically actuated ailerons is "transparent" to the pilot. Some 52Oh have been accumulated since the first flight in June 1996. "Experience in the field has proved that the maintenance required to remove, install, troubleshoot and rig is very much less [than with the conventional hydraulic system]," he says. The Lucas system has health-monitoring capabilities. Electric actuation is attracting attention as a way to overcome reli ability problems with in-service aircraft, adds Croke. • NEWS IN BRIEF • AIRLINES ADOPT AMICOS Wideroe of Norway has ordered Danish firm Cimber Data's JAM/Prolifics AMI- COS system for managing its DHC Dash-8 fleet mainten ance. Meridiana has also selected the AMICOS for its maintenance base in Olbia with on-line connection to its base in Florence, Italy, where the AMICOS will be running on an HP9000 Unix comput er with an Informix database. • JAPANESE ENGINE SPARES Ishikawajima-Harima Heavy Industries (IHI) is construct- inga ¥10 billion (S87 million) jet-engine parts plant at Soma, Japan. IHI expects the plant, due to open in October 1998, to generate annual sales of around $300 million. • AYDINONJSFTEAM Lockheed Martin's Skunk Works has awarded AYDIN Telemetry a $6 million con tract to supply the flight-test instrumentation equipment for its two Joint Strike Fighter QSF) demonstrator aircraft. • TEST EQUIPMENT Sabena Technics is to design and produce test equipment for International Aero Eng ines V2 500 engines for Hong Kong Aero Engine Services (HAESL). The Belgian com pany has also signed similar contracts with Air France and Iberia for test equipment for CFM56-5Cs and CFM56-7s. • SPACE WEATHER The US Los Alamos labora tory has obtained its first ac curate readings of the polar wind which flows off the Earth. Its POLAR satellite's plasma-source instrument emits xenon ions to neu tralise the plasma flowing past the spacecraft. Monit oring interference caused by polar and solar winds, major factors in "space weather", is increasingly important for satellite communications. FLIGHT INTERNATIONAL 6 - 12 August 1997 25
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