'Fastenerless' design improves inlet duct

Fort Worth, TX -Lockheed Martin has successfully tested a fastenerless aircraft engine inlet duct system. The Joint Strike Fighter (JSF) team completed pressure testing of a minimal fastener inlet duct system that offers several cost and operational advantages.

The design incorporates a combination of composite material and process technologies for fabrication of the one-piece duct segment. The key to the success of the design was primarily due to advances in fiber reinforced preform technology for resin transfer molding (RTM). To achieve the goal of 100% fiber placement, a 3D wire-mesh graphite mandrel was used. Additionally, the use of integral attach flanges reduced the number of through-the-duct fasteners by 80%. Elimination of fastener penetrations through the inlet creates a smooth inner surface that produces better aerodynamic performance for air feeding the engine. Reducing the number of fasteners also eliminates corrosion and fuel-leak repair maintenance. "Compared to inlet ducts in today's operational aircraft, we estimate the new duct can be produced in half the time span and at two-thirds the cost," says Frank J. Cappuccio, vice president and program manager of the Lockheed Martin JSF.

The recent step towards validating the use of integral composite attach flanges was achieved through pressure test qualification. During testing, the duct resisted failure at 120-140 psi (twice the ultimate design load), approaching the limits of the test fixture. Visual inspection confirmed no visible evidence of failure after completing the test. "Not only did this duct test article contain all the features we expect to see in production, but these details were fabricated using production processes and tooling," notes Bill Coleman, Inlet Integration Demonstration team lead.

Flight evaluation of the JSF demonstrator aircraft is scheduled to take place this year, with government selection of a single contractor for the Engineering and Manufacturing Development phase set for 2001.