A 1/15-scale JSF model was tested in Lockheed Martin Aeronautical Systems' low-speed wind tunnel in Marietta, GA.

Approximately 200 h of low-speed testing was conducted in August 1999 in the 16 x 23-ft low-speed wind tunnel at Lockheed Martin Aeronautical Systems in Marietta, GA. Testing was performed in both takeoff/landing and "up-and-away" configurations at speeds up to 200 kt.

High-speed testing in the range of Mach 0.6-1.6 was conducted at the wind tunnel facilities of Veridian Engineering (formerly Calspan) in Buffalo, NY, and the USAF 16-ft transonic wind tunnel at Arnold Engineering Development Center in Tullahoma, TN. More than 200 h of testing were completed in the high-speed series through early October 1999.

According to Lockheed Martin, its JSF aerodynamic configuration resembles the F-22 Raptor's and, as such, benefits from much of the wind tunnel testing that has already been conducted in that program. The F-22's handling qualities are now being verified in flight testing conducted from Edwards Air Force Base, CA.

A quality-assurance inspector uses a handheld light pen to validate the assembly process on a JSF bulkhead.

Lockheed Martin Tactical Aircraft Systems (LMTAS) is also searching for ways to improve affordability in the company's JSF program. LMTAS is finishing up a one-year development project to evaluate the measurement capabilities of a system that will be used to measure parts and parts assemblies in the JSF manufacturing process.

Historically, manufacturers have used Coordinate Measuring Machines (CMMs) to perform these tasks. A disadvantage of using these machines is that both parts and assemblies have to be brought to the CMM, which is in a fixed location in a temperature-controlled room. For small parts and assemblies this may just be a minor inconvenience, but for larger parts it could be a very labor-intensive project, requiring up to three workers for an entire shift's worth of time. In addition, it could also take anywhere from 6 to 30 h to write a measurement program on a CMM.

JSF aerodynamic testing was also conducted in the USAF's 16-ft transonic wind tunnel at Arnold Engineering Development Center in Tullahoma, TN.

The Metronor system, which was developed and manufactured in Norway, is portable and can be set up for part or assembly measurement in a few minutes. Measurement programs on the Metronor can be written in about one and one-half hours. Lockheed Martin is currently evaluating the system for its JSF program.

The system works by using infrared light-sensing digital cameras to see light emitting diodes (LEDs) in a handheld "Light Pen." The system's computer synchronizes LED with camera exposure, and using LED and camera positioning, triangulates the Light Pen's probe tip position, which is in contact with the object being measured.

According to LMTAS, inspection time for a typical machined part using the Metronor vs. a CMM has been reduced by 56% for a large part and up to 64% for a small part. These time savings do not include the significant potential of transportation savings due to the system's portability.

LMTAS has also expanded its search for improving affordability to 3-D woven-composite materials. This approach to composites provides adequate strength with significantly less weight. It was selected by the company to overcome the limited ability of traditional composite structures to effectively handle complex, out-of-plane loads. This shortcoming was identified in the 1998 annual report of the Composites Affordability Initiative (CAI), a government and industry consortium dedicated to the advancement of composite materials technology.

Lockheed Martin is using 3-D woven-composite, preformed structural parts in its JSF design to efficiently carry out-of-plane structural loads and improve affordability. The engine air inlet duct shown here features integral stiffeners and no fasteners.

Lockheed Martin and Northrop Grumman, its JSF partner, are using 3-D woven-composite preforms on the JSF inlet duct and other structural components of the aircraft. Bally Ribbon Mills in Bally, PA, fabricated the preforms using conventional weaving machines.

The engine air inlet of the company's JSF production design consists of a seamless fiber-placed duct stiffened with 3-D woven-composite preforms. The use of these preforms for stiffening eliminates 95% of the fasteners through the duct, improving aerodynamic and signature performance, eliminating fuel leak paths, and simplifying manufacturing assembly. "The application of 3-D preforms to the JSF inlet duct reduces the cost of the duct by at least $200,000 and saves more than 80 lb of weight," said Northrop Grumman's Martin McLaughlin, leader of the JSF Airframe Demonstrations Integrated Product Team.

Another contributor to the affordability of the Lockheed Martin JSF is Fokker Aerostructures, B.V., a division of Stork Aerospace in the Netherlands. Fokker completed a thermoplastic composite engine-access cover, one of several demonstration articles being built for the company's JSF Advanced Affordability Initiative (AAI). According to Lockheed Martin, Fokker achieved a 30% cost savings in producing the part compared to the baseline manufacturing method.

Fokker Aerostructures recently completed its first demonstration article, an engine access cover panel, for Lockheed Martin's JSF Airframe Affordability Initiative. The panel measures 7.5 x 2 ft and is made from composite material.

The thermoplastic process for producing carbon-fiber composite structures is an evolving technology that requires fewer steps and is less expensive compared to the more traditional thermoset and other processes. The process also allows reheating and reforming of the component in case of unacceptable flaws; flawed thermosets cannot be reformed and must be scrapped.

In addition to the engine access panel, Fokker is designing and building three other major JSF structural components for the AAI program: the horizontal tail, weapons bay sidewall, and a wing box. Another Stork subsidiary, Fokker Elmo, is also participating and will demonstrate the latest electrical-component technology with a wing harness assembly, electrical power panels, and a modular electrical systems assembly.

Lockheed Martin received one of two JSF demonstration contracts from the U.S. Department of Defense in 1996. Flight evaluation of the demonstrator aircraft is scheduled to take place this year, with government selection of a single contractor for the Engineering and Manufacturing Development (E&MD) phase set for next year.

Frank Bokulich