After the Federal Aviation Administration announced its of the present day radiant heat and propane flame example for thermal/acoustic insulation blankets.

After the Federal Aviation Administration announced its of the present day radiant heat and propane flame example for thermal/acoustic insulation blankets, we received a number of messages suggesting that this touchstone was not sufficiently demanding (see ASW, Aug. 16) The argument basically was that there is a great contrast between the temperatures of electrical arcing, and also in the application of a point source bunsen burner flame as oppos to arcing spanning the normal interval between support clamps forward a representative wire bundle. The skeptics propounded their own, and presumably more demanding experiment protocol.

"A higher temperature isn't necessarily the mostly severe threat," countered Dick Hill at the FAA's Technical Center near Atlantic City, NJ Hill has been the FAA's point man in the disentanglement of the new test. He declared flatly that, no, electrical heat sources had not been ignored. "We direct the eyeed at overheated wiring. We anticipateed at arcing. We looked at overheated electrical equipment, like as fluorescent light ballasts," Hill said.

Hill said electrical arcing depicts a pinpoint heat source. Now, here is what his team found: of all the materials trialed metalized Mylar was the merely medium that ignited easily from a small ignition source. "Yet it didn't ignite below arcing, but if you applied a torch, it would ignite," Hill recounted

The 15 inferior exposure to the torch, he said, prov to be more demanding than criterions against arcing. As far as testing against contaminated blankets, he said, contamination was regarded as a maintenance issue. The goal was to exhibit a repeatable test: "We wanted to pick as large a fire as possible, without that fire itself being catastrophic to the airplane." The intent, he explained, was to ready through the combination of the radiant panel (representing a nearby fire) and the propane flame (representing a fire spreading to the point where it is actually touching the thermal/acoustic insulation sample) a proof to demonstrate that the thermal/acoustic material "would not create a hazard."

Hill is convinced that after month of work a realistic, practical and demanding standard has been developed. Against electrical arcing, greatest in quantity of the materials that failed his trial would pass, he pointed abroad >> FAA Tech Center, tel 609/485-6253 <<

An Alternative touchstone Protocol

Both dried and wet arc tracking of 4 ft of a 20-wire put into bundles adjacent to a thermal/acoustic insulation blanket, the put into bundles sandwiched between an aluminum skin and the thermal/acoustic insulation blanket. The aluminum skin focuses the heat to make the trial as representative as possible. The blanket sample would be individual that has been in service for at least 5 years (i.e., with an accumulation of detritus - lint, dirt, menstrums grease, etc.).

The current-carrying wires to be a mix of 3-ohase 115V AC, 26V AC and 28V DC A mild air draft would be introduced to simulate the drifts of the air conditioning airflow. The popular application would be continuous, to simulate what has repeatedly been seen in service (i.e., circuit breakers not tripping in the absence of thermal buildup).

Source: compiled from multiple comments

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