Messier-Dowty completed on July 20 what it says is the first successful takeoff and landing of a commercial flight test aircraft equipped with composite braces on the main landing gear.
The test flight, which took place on Airplane ZA001 over Boeing Field, is the culmination of major design and development efforts to introduce composite technologies on key structural landing gear components for the Boeing 787 program.
Braces (or side stays) were chosen for the composite application for two main reasons. They are simpler load path structures, only working in tension/compression; they do not twist or bend, generally. And the parts have relatively simple interfaces, the company notes, being joined by two pins at each extremity.
Messier-Dowty is using organic matrix composites—a mixture of high-strength carbon fiber and resin, which holds the fibers together—for the application. Woven carbon fibers are placed in a mold in which epoxy resin is injected, a process called Resin Transfer Molding (RTM).
Besides offering a better strength/weight ratio compared to high-strength steels, composites provide higher resistance to corrosion and fatigue than ultrahigh tensile strength (UHTS) steel parts. The result, according to Messier-Dowty, is better in-service reliability and longer intervals between overhauls.
The use of composite materials, along with the expanded use of titanium on other major structural components such as the inner cylinder, “significantly reduces” the weight of the landing gear vs. previous-generation steel gears, Messier-Dowty claims.
A spokesperson said the company is not able to comment further at this stage in regard to specific mass figures or the cost of the composite braces vs. previous parts.
The composite development work for the braces—designed, certified, and managed by Messier-Dowty, a Safran Group company—included technical expertise from The Boeing Co. as well as Snecma and Aircelle, which have experience in the use of woven composite technologies and RTM.
Aircelle is responsible for series production of the braces, which began in 2008 in its Le Havre facility in France.
Messier-Dowty—responsible for the main and nose landing gears for the 787 program since 2004—says it will continue to develop this technology for other large commercial aircraft programs. The company is also working to broaden the technology’s application for other simple load path structures, such as bars, rods, and other internal parts.