A commercial aircraft industry group wants the Federal Aviation Administration to have a common process to certify repair materials. Now, the FAA's five regional offices certify polymer-matrix-composite materials. However, the Commercial Aircraft Com-posite Repairs Committee seeks to standardize terms, procedures and technician qualifications and to educate airline workers on how to work with composites.
``There are definitely differences between how certification offices work,'' said Timothy Harris, maintenance training instructor with Boeing Co. and a spokesman for the CACRC.
Aligned with FAA regions, five aircraft certification offices have responsibility for original approval of procedures for commercial repair work, wherever performed, of certain original-equipment manufacturers.
Work at airframers Gulfstream, Embraer and Lockheed, for example, is assigned to the Atlanta regional office; Mitsubishi, Beech, British Aerospace, Lear Jet, Cessna and Sabreliner, to Wichita, Kan.; DeHaviland, Canadair and Fairchild, to New York; Boeing, to Seattle; and McDonnell Douglas, to Los Angeles.
``We have found the use of five [aircraft certification offices] provides economy along with the best support for the customers,'' said Mitch Barker, an FAA public affairs specialist in Seattle. ``However, the setup is being reviewed now so it is possible changes may be made in the future.''
The Joint Airworthiness Authority certifies repair work in Europe.
Qualifying a new composite material system can take up to six years, and the regional interpretations can complicate the process, Harris said. OEM, airline, supplier and regulatory members of the CACRC are writing specifications for repair materials.
Gary Oakes, an aircraft structures engineer with Boeing's 777 Division, said, ``We at Boeing are working on a certification plan to present to the other OEMs on the [CACRC] repair materials task group, and then the CACRC will present it to the FAA,'' perhaps in June. A common process would allow individual OEMs to obtain approval to use a material without a separate certification plan.
``It's a complex situation to address,'' Oakes said. ``We don't know what the response will be.''
If the FAA agrees, such a plan would allow the OEMs to better coordinate material specifications and international test methods for polymer composite repairs, said Mark Rodekuhr, group engineer in the Riverside, Calif., facility of Rohr Inc. and chairman of the CACRC's repair materials task group.
Now, OEMs specify various resin systems with different shelf lives, mixing ratios and curing temperatures. CACRC's goal: eliminate duplication, simplify procedures and reduce repair costs through common materials.
After years of incremental steps, CACRC seeks a ``national [certification] approach to handling wet-layup specifications,'' Oakes said. Most aircraft shops turn to wet layup for repairs although the manufacturers use preimpregnated materials for original flight articles.
Prepreg is next. ``Now that CACRC has learned how to get tasks done with OEMs on carbon wet-layup repairs, it should go faster on prepreg specifications for repair,'' said Peter Oberg, group design engineer at Chula Vista, Calif.-based Rohr and a member of the CACRC executive committee.
Sections of the Air Transport Association, the International Air Transport Association and the Society of Automotive Engineers merged in 1991 to form CACRC, which met May 8-9 in Belfast, Northern Ireland, to discuss repair and material issues.