AGATE Program Helps Streamline Material Certification Process

Airplane manufacturers are responsible for time-consuming and expensive FAA certification testing to qualify every composite combination for use in each aircraft design. The high cost of testing tends to limit composite use to large commercial aircraft, leaving non-FAA-certified experimental kit planes on the cutting edge of design in the general aviation arena. As a Boeing engineer pointed out, one widely used carbon/epoxy composite sold by a single company has 34 different procurement specification databases governing its sale.

The certification process will become considerably easier thanks to the AGATE (Advanced General Aviation Transport Experiments) program. Begun in 1995, AGATE is a wide-ranging public/private consortium effort aimed at making U.S. general aviation more affordable and safer. AGATE involves more than 70 entities, including the National Aeronautics and Space Administration (NASA), the FAA, aircraft manufacturers, universities and composites suppliers. The endeavor encompasses training, safe ways to utilize air space and improvements in ground infrastructure systems, in addition to promoting wide use of composite materials. According to John Turiello, director of marketing and sales at FiberCote Industries Inc. (Waterbury, Conn.), AGATE includes a streamlined material certification program with preapproved supplier databases that will enable composite aircraft parts and assemblies to be designed and built in as little as one-half the time currently required.

The physical properties of traditional materials like aluminum and steel have long been acepted by the FAA in the design of airframes. These "allowables" mean the designer does not have to test every part to failure - an expensive, time - consuming process - but may substintiate the design using various forms of analysis, according to John Tomblin of the National Institute for Aviation Research (NIAR) laboratory at Wichita State Universitey and chairman of the AGATE Materials Group.

In the case of composites, the allowables vary rom company to company, an inevitable result of different manufacturers making composite products with the same raw materials. Further, composite allowablesare often cosidered proprietary and generally are not shared with other airframers, which causes a repetition of qualification testing, often for identical products. Under AGATE, the material suppliers will characterize their composite materials and produce FAA-approved prodcut-specific databases, with design allowables defined. Manufacturers, in turn, will be able to use the preapproved design allowables after executing an abbreviated material - equivalence test plan.

According to FiberCote's Tauriello, after a reported investment of $1 million, three FiberCote products are now approved: E-765, a 3K plain-weave carbon/epoxy prepreg fabric; Uni-carbon, a carbon/epoxy unidirectional tape; and a 7781 fiberglass/epoxy prepreg fabric. A 6K five-harness satin weave epoxy/carbon prepreg fabric is currently being tested for lamina properties, and approval is expected soon. Tauriello reports that several FiberCote customers have already demonstrated savings of pu to 80 percent on material qualification costs and significant time savings. " A radome skirt fairing designed by Flight Structures ( Arlington, Wash. ) and built by Nova Composites ( Mukilteo, Wash. )is the first part to our knowledge approved by the FAA that uses suplier - generated allowables", says Tauriello.

Toray Composites America Inc. ( TCA, Tacoma, Wash. ) is another supplier involved in the AGATE material certification program. According to Leslie Cooke, aircraft business development manager at TCA, AGATE is a good fit with his company's philosophy. "We produce large volumes of consistent and reproducible prepreg, which is in line with AGATE's goals of tested and standardized airframe materials", says Cooke. " Our approved materials will be able to be used across the board in the aviation industry." TCA expects final certification by the end of May for three products, including a Torayca T700G 12K unidirectoinal carbon tape, a 7781 glass-fiber eight-harness weave fabric prepreg and a T700S 12K carbon fiber plain weave, non-crimp fabric. the non-crimp12K fabric is ideal for the kit plane market, because it produces a superior surface finish with few "pinholes" and reduces the time and labor to prepare aircraft parts for painting.