P. Lequeu, R. DIF, ALCAN Pechiney Rhenalu, Issoire, France; T. Warner, Alcan, Voreppe, France; D. Dumont, ALCAN CRV, Voreppe, France; P. A. Wood, Airbus, Bristol, United Kingdom

Summary:

Large commercial aircraft wing structures are submitted during normal level flight to heavy loads coming from the aircraft weight (aircraft structure, engines, fuel, passengers…) and to the airload or wing lift. Some other main forces also apply, such as torque due to the engine thrust. Wing covers are primarily designed to react against the end loads caused by wing bending associated with wing lift; this normally leads to compression in the top covers. This is the reason why upper wing materials have been long selected among the higher strength 7xxx alloys, such as 7150 or 7449, in order to accommodate as much as possible the compression loads at a reasonable low weight. In some cases however, damage tolerance becomes also important particularly for upper wing inboard structures, because of the position and weight of the engines and/or because of the specific missions and thus loads of the aircraft.

A new alloy called 7056 has been specially developed by Alcan Aerospace to answer such requirements of high strength and very high damage tolerance for upper wing panels, such as those observed on A380 Freighter. With a typical R-curve improvement of about 50% versus the original alloys and with an associated limited static decrease of about 5% versus 7449, this new alloy developed in a T7x over-aged temper allows significant weight saving in the load configurations described above.

The presentation will highlight the fundamentals of the alloy as well as its main mechanical properties derived from the design requirements and its manufacturing behaviour. 7056 has been developed as a low residual stress and age-formable plate material, thanks to a standard 2-step age practice, and can be produced in an intermediate TAF temper (dedicated to age-forming) or in the final T7x over-aged temper. 7056 has been selected to fly on A380 Freighter as upper wing panels and details.