structural shell of the aircraft, including cabin furnishings; ceiling, wall, and floor panels; cargo compartment and containers; insulation; wiring; lighting; ducts; windows; and lavatories. Payload items, such as luggage, items, other cargo, newspapers, magazines, the clothing of passengers, and food-related items are important to such fire-related issues as ignitability and generation of smoke and toxic products, but the fire resistance of these items is not considered in this study because they would be very difficult to control. However, the impact of such items as sources of heat in aircraft interiors during crashes should be assessed when evaluating and modeling the fire-resistance qualification and testing conditions. Fire safety systems such as water mist, hoods, vents, and fire suppression systems may affect the criteria used to establish performance goals for the development of fire-resistant materials. These systems, while providing additional benefits in fire safety, were not within the scope of this study.
Aircraft interior materials must be lightweight and meet engineering, wear, and cosmetic requirements, in addition to having desirable fire-safety characteristics. In meeting all of these requirements, it is important to recognize that there are not likely to be optimal materials that will, under all possible circumstances, be completely nonflammable and incapable of generating smoke and toxic products. Furthermore, materials processing requirements may limit the application of materials technologies that are otherwise preferred in terms of fire safety. These considerations dictate an approach to the principal study objectives set forth above that begins with defining the most likely fire scenarios to be experienced and how long the aircraft interior must remain safe once a fire occurs.
Although there have been some in-flight fires, catastrophic fires are generally post-crash related. In the past, in-flight fires have caused only a very small fraction of fire deaths. For example, according to FAA data, there has been only one in-flight fire death in U.S.-registered commercial transport aircraft (and that death was a suicide). In non-U.S.-registered aircraft, the few catastrophic in-flight fires were initiated in inaccessible areas.
The committee considered both in-flight and crash fire categories. However, in-flight fires in accessible areas within the aircraft interior were not considered. These fires have traditionally been extinguished quickly by properly trained flight personnel aided by early detection and warning systems and suitable portable extinguishing equipment. In-flight fires in inaccessible areas are more problematic because of the potentially long periods before passengers can be evacuated and the fire extinguished. Long-term fireworthiness and materials that produce extremely low levels of smoke and toxic products are required for such inaccessible aircraft interior components. In-flight fires in inaccessible areas were therefore one focus of this study.
For post-crash fire scenarios, the imperative is to provide passengers who survive the crash sufficient time to leave the aircraft without fatal exposure to heat and smoke and toxic fire products. Smoke and toxic products can result in visual obscuration and partial mental and physical impairment, thus indirectly increasing the required evacuation time. Post-crash fire scenarios are extremely varied; however, the committee defined several general categories for such fires in order to better classify typical fire exposures. Both post-crash and in-flight fire scenarios are described in Chapter 3.
Finally, this study emphasizes long-term innovation leading to assessments of the fireworthiness of aircraft interiors 10–20 years hence (see Chapter 4). Thus this report addresses the issue of aircraft interiors more than 10 years in the future, including possible high-speed civil transports and large subsonic transports.