The rules neither talk about what kinds of retardants are to be used in making materials flame-resistant, nor what materials or fabrics are to be used, but they do specify which kinds of burn tests the materials have to pass to be acceptable.
The FAA, basically, has established two kinds of tests for interior materials; the vertical test and the horizontal test. Three samples of the fabric are tested and the three results are averaged to reach a pass-fail mark.
Both tests have specifications as to the time that flame is applied to the material, depending on the type of aircraft, and thus the rule being applied, but fundamentally, the test determines the material's ability to resist flaming. In the vertical test, the flame is applied with the specimen held in a vertical position; in the horizontal, it is applied with the specimen in a horizontal position.
Knowing the requirements
Where does this leave the technicians who are installing or otherwise working with fabric in the interior of an aircraft? First, they must understand that some form of fire protection of aircraft interiors is absolutely required, regardless of the size or type of the aircraft. Other than that, what is required of technicians depends on the fabric, the source of the fabric, the type of work being done, and the aircraft. If, for instance, a technician is dealing with fabric that has arrived with no documentation or is known to be non-aviation certified, the A&P, to be risk-free, should get the fabric tested for flammability at an FAA-certified repair station or lab. If it passes, it is safe to install. The DER (Designated Engineering Representative) at the testing site will send it back with the necessary documentation. If it doesn't pass, it has to be treated with a flame retardant, tested again, and certified. The treatment can take place in-house, but the test and the test results have to be certified.
"If there is some question about some fabric," says Walker, "for example, if you get material that doesn't come from one of the companies that make stuff for aircraft, then you have to test it. We send it out for testing. If it fails we treat it and have it re-tested. I have several fabric vendors and all of them certify their materials."
O'Brien cautions that unknowns, in any form, are bad for aviation — "but I would just get the fabric tested and certified by a lab or repair station that is certified to do the testing."
In practice, even if fabric arrives with the necessary certification, it does not necessarily get a stamp of approval from the FAA. It depends on the region, according to Judy Boggs, a DER with Skandia Inc., a testing lab in Rockford, IL.
"In some regions of the FAA," Boggs says, "even if it (fabric) comes with manufacturer's certification, you still have to have it re-tested. Not all the regions interpret the rule that way, but some do. You can't take anybody's word for it."
Installations and STCs
Installing interiors has the potential for becoming an STC issue when the work takes on "major" proportions, according to O'Brien at the FAA. "Assuming we are talking about replacing the fabric on the seats, headliner, and side walls only, no other modifications," O'Brien says, "then no STC is required as long as the fabric meets the type design of the aircraft. If the fabric that meets the type design also now has flame resistant properties, and that is the only change, then it is a minor alteration. So, the job is a minor repair (replacing the fabric) with a minor alteration (flame resistance)."
"The retardant comes in many chemical forms," according to Drew Clabough, flame treatment manager at Skandia, who uses "seven or eight" different compounds.
"Everything we use is water based," Clabough says. "They're non-corrosive, non-hygroscopic (don't draw moisture from the air). There's no problem with corrosion or skin irritation or anything like that in the future."
Clabough warns, however, that some materials are difficult to treat. "Sometimes we receive materials to treat that have previously been Scotch Guarded® or waterproofed. This makes it difficult for the material to absorb a treatment. 100-percent nylons and synthetics are difficult to treat."
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