Boeing 787: composites make a successful landing
On July 22, at Everett (Washington State) where the Boeing factories are located, a B787 Dreamliner underwent its first test flight with its main landing gear assemblies equipped with braces made of composite materials. "It's the first time that a commercial aircraft ever took off and landed with landing gear featuring this technology," says an enthusiastic Patrick Dunleavy, Mechanics & Composites expert at Messier-Dowty. The braces are the two leg struts that hold the main landing gear in place during the landing and taxiing phases. On today's airlines, these parts are predominantly made of steel. The use of composite materials enables the mass of the aircraft to be reduced significantly. Bearing in mind that a main landing gear assembly has two braces and that the Boeing 787 is equipped with two such assemblies, the weight savings are anything but negligible! Composite materials also offer better corrosion resistance, which keeps maintenance work to a minimum and reduces servicing costs.
The highly sophisticated technology chosen by Messier-Dowty to produce these landing gear braces is 3D weaving, a specialty of Albany International, a company with which Safran has been in partnership for over ten years, adapting this technique to aeronautical applications. The fibers are consolidated using RTM (Resin Transfer Moulding) injection. This application for the landing gear braces was developed by the Messier-Dowty engineering department, in particular with respect to the transition between the yoke joint (the eye-shaped section) and the cylindrical section.
The matrix is first of all flat-woven using carbon fibers then shaped prior to injection of the resin under pressure. As designed and managed by Messier-Dowty, with the technical support of Boeing, the development of the material for the braces is the fruit of collaboration between several companies of the Safran group. "We were able to benefit from the methodological support of Snecma for the modeling of the materials and from the experience of Aircelle which already produces RTM parts for its nacelles. We have also worked in close collaboration with Boeing and the FAA for the certification of this first ever structural part made of composites on a landing gear assembly," explains Patrick Dunleavy.
Aircelle is also responsible for the manufacturing of the braces in its Le Havre plant.
The test flight on July 22 of this year marks a major stage in the introduction of composite technologies into the structural elements of landing gears.
For Messier, this first collaboration on a commercial program with Boeing is of particular significance, since this program should ultimately come to represent a major proportion of the company's activity.