The Federal Aviation Administration (FAA), as part of its hidden in-flight fire mitigation program, developed an improved flammability test method for aircraft electrical wiring insulation materials (including jackets and other wire protective materials). A comprehensive fire test research and development (R&D) project was conducted on aircraft electrical wiring insulation materials in an effort to continue mitigating the threat of in-flight fires. Previous work at the FAA and the National Fire Protection Association have indicated that the current FAA-required 60-degree Bunsen burner test for electric wire was inadequate to qualify wire when bundled and subjected to a severe ignition source. A literature search and in-house fire tests were conducted during this effort. The results of the literature search indicated that there was no small-scale flammability test standard available that considered radiant heat and wire bundling in its specifications or acceptance criteria that included burn length and after-flame extinguishing time; therefore, an improved flammability test standard for aircraft wiring was required. In-house fire tests were conducted to develop an improved flammability test and provide support data; tests included the current FAA-required 60-degree Bunsen burner test, the microscale combustion calorimetry test (ASTM D 7309-07), the thermogravimetric analysis (ASTM E 2550-07), the intermediate-scale fire test, and the radiant heat panel test. From this R&D effort, an alternative radiant heat panel test method was developed. This method was effective in evaluating the in-flight fire resistance qualities of aircraft electrical wiring insulation.

Thermoplastics and composites made from hydrocarbon polymers can improve the affordability, strength-to-weight ratio, and durability of manufactured products. Unfortunately, the use of these materials in aircraft and other vehicles is limited because of their inherent flammability. An alternative, lower-cost strategy is to develop environmentally benign additives that significantly reduce the flammability of commodity polymers. In this study, polymers blended with graphite oxide (GO) and its functionalized analogs were evaluated as cost-effective, fire-resistant materials for aircraft and other forms of mass transportation. GO polymer nanocomposites were prepared by dispersing 1, 2.5, 5, and 10 weight % GO in polycarbonate (PC), acrylonitrile butadiene styrene (ABS), and high-impact polystyrene (HIPS) for the purpose of evaluating the flammability and materials properties of the resulting systems. The overall morphology and dispersion of the GO within the polymer nanocomposites were studied by scanning electron microscopy and optical microscopy; the GO was found to be well-dispersed throughout the matrix without formation of large aggregates. Mechanical tests were performed using dynamic mechanical analysis to measure the storage modulus, which increased with GO loading for all polymer systems. Microscale oxygen consumption calorimetry revealed that GO could reduce the total heat release and heat release capacity of HIPS and ABS. Nanocomposites of GO with PC demonstrated very fast self-extinguishing times in vertical open flame tests. Heat release rate of the 2.5 weight percent GO nanocomposites measured in a cone calorimeter in flaming combustion was reduced 25% and a surface energy balance was used to explain the results in terms of enhanced radiant energy losses by the GO.

The processes that take place in the condensed phase of a burning polymer play an important role in the overall combustion. Quantitative understanding of these processes is critical for prediction of ignition and growth of fires. During the past decade, a significant effort has been made to develop mathematical models of polymer pyrolysis. In the current study, a model of burning of two widely used charring polymers, bisphenol A polycarbonate and poly(vinyl chloride), was developed and validated. The modeling was performed using a flexible computational framework called ThermaKin, which was developed in the Federal Aviation Administration laboratory. ThermaKin solves time-resolved energy and mass conservation equations describing a one-dimensional material object subjected to external heat. Most of the model parameters were obtained from the results of direct property measurements, which is a key distinguishing aspect of this work. The model was employed to simulate cone calorimetry experiments performed under a broad range of conditions. Possible sources of error in the model parameterization were analyzed. The results of this study demonstrate that a one-dimensional numerical pyrolysis model can be used to predict the outcome of cone calorimetry experiments performed on a charring and intumescing polymer. A simple submodel based on the properties of graphite and a single adjustable heat transfer parameter provides a reasonable approximation to the carbonaceous char description.

Thermal acoustic insulation blankets are widely used in commercial aircraft to provide thermal insulation and acoustic damping. This report examines the burning effects on the thermal acoustic insulation blankets retrieved from the EVA Airways Flight BR67 fire event. On February 23, 2008, passengers disembarking from EVA Airways Flight BR67 reported smoke in the cabin of the Boeing 747-400 after landing at Suvamabhumi International Airport in Bangkok, Thailand. An investigation of the incident revealed burned thermal acoustic insulation blankets. The level of contamination on the encapsulating films of the as-received insulation blankets varied greatly. Samples of the contaminated film from different locations were weighed to determine the areal weight of contamination, were ranked by visual inspection, and were characterized by microscale combustion calorimetry to determine the thermal combustion properties. Thermal acoustic insulation blankets were also tested for flammability as prescribed by Title 14 Code of Federal Regulations 25.853 and 25.855. It was found that the visible contamination ranged in areal weight up to 167 grams per square meter of film surface and had a heat of combustion of 13 kJ/g, which is half that of the underlying insulation bag film. All in-service blankets and film samples passed the required 12-second vertical Bunsen burner test for flame resistance. The contaminated blankets did not pass the voluntary guideline for flame spread. Numerical modeling of the burning rate of contaminated blankets was conducted to help explain the flame spread results.

Tests were performed at the Federal Aviation Administration William J. Hughes Technical Center by the Fire Safety Team of the Airport and Aircraft Research and Development Division to examine the fire safety hazards that cylindrical- and polymer-type lithium-ion batteries may pose onboard aircraft. Tests were conducted on individual, manufacturer-supplied battery cells to determine how the cells would react in a fire situation, as well as what potential fire hazard the battery cells themselves may pose and the effectiveness of a typical hand held extinguisher on a fire involving the battery cells. The battery cells that were tested were all commercial off-the-shelf products that are being considered by manufacturers for aircraft power-related usage.

The results of the tests showed that the lithium-ion and lithium-ion polymer battery cells can react violently when exposed to an external fire. Under test conditions, when the battery cells failed, flammable electrolyte was released and ignited, which further fueled the existing fire. This release and ignition of the electrolyte resulted in significant temperature and pressure increases within the test fixtures.

Tests conducted with a hand-held Halon 1211 fire extinguisher showed that the halon was able to extinguish all three battery-type fires. However, even after several attempts, the halon extinguishing agent was not able to prevent the lithium-ion polymer battery cells, which are of a different chemistry, as well as a much higher energy density and power capacity, from reigniting.