The evacuation of aircraft is very different from that expected in a building or residence and those differences need to be incorporated into hazard models.

As the fire resistance of interior materials improves, toxicity models may need to be expanded to determine the effects on accident survivors of gases likely to be generated if the new fire-safe materials thermally decompose. Other potential effects that should be evaluated are releases of hot water vapor, particulates, and free radicals; the adverse effects of heat on the human body; and the effects of simultaneous exposure to toxic gases and heat. In the long term, the effects of factors such as physical exertion and alcohol may also be incorporated. Instead of test animals (e.g., rats, mice), increased use of in vitro endpoints should also be investigated. Long-term health effects, such as mutagenicity and carcinogenicity, from short-term exposures need to be studied.

Finally, the models under development must be validated to gain the confidence of the design community. This requires a closely coordinated research effort between theoretical model development and intermediate and large-scale validation testing. More emphasis needs to be placed on requiring intermediate and large-scale testing to verify small-scale data and to refine the understanding of the effects of size and configuration of interior components on the fire performance.

Recommendations:

  • Develop basic thermal degradation models that are applicable to engineering and specialty polymers and include crosslinking, cyclization, aromatization, and network formation to aid the understanding of polymer stability and char formation. Include both char characteristics and evolved gaseous product properties as key model parameters.

  • Develop intumescent char models based on the formation and growth of bubbles, swelling, polymer melt behavior, and carbonization.

  • Develop an integrated modeling capability that will allow the estimation of the performance benefit of various choices of fire-resistant materials and components in aircraft interior applications. Work is needed to develop fire-growth, toxicity, and hazard assessment models relating to aircraft fire scenarios.

Long-Term Research Program

The committee believes that the goals of the FAA's research program to develop significant order-of-magnitude improvements in materials fire performance cannot be met with incremental advances or near-term regulatory activity. Rather, substantial advances based on a fundamental understanding of polymer combustion, on accurate aircraft fire scenarios, and on the systematic development of materials technology improvements are required. These advancements require a long-term commitment on the part of the FAA working with the aircraft and materials industries and research laboratories.

The uncertainty of new commercial programs, the cost of qualification and certification, and the long time-to-market for new materials tends to discourage suppliers from embarking on materials development efforts. The size of the potential market for materials for use in aircraft interior components often does not justify the expense to the suppliers of development and qualification. Thus, it is important to develop alternate markets for new materials and to apply technology developments from other industries.

Many of the developments that arise from this research will be unique to the issue of commercial aircraft interior fire safety. However, advances in the understanding of polymer combustion, new materials and additive technology, and testing and modeling methods may have applicability to fire safety in other transportation systems such as submarines, ships, mass-transportation systems, automobiles, and buses, as well as commercial and residential buildings. If this long-term research effort is sustained and a coordinated, parallel effort persists in these related areas, significant advances will be made in the understanding of materials fire safety not only for commercial aircraft interiors but also in many other areas where fire safety is a concern.

Recommendations:

  • Sustain the effort to develop significantly improved fire-resistant materials as a long-term research program, with clearly stated goals, plans for systematic technology development, and stable financial commitment.

  • Continue to follow developments in fire safety in the materials and aerospace industries, as well as in related industries. Coordinate within the U.S. Department of Transportation and with other federal agencies conducting related research, including the National Aeronautics and Space Administration, the departments of Defense, Energy, Transportation, Commerce, and the National Science Foundation.



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