A compre hensive systems-level approach in cabin design minimizes fire potential and helps ensure passenger safety. 18 AERO QUARTERLY QTR_04 | 11 Fire Protection: Passenger Cabin The cabins on all Boeing airplanes incorporate comprehensive fire-protective features and materials to minimize the potential for a fire and help ensure the safety of passengers. By Arthur L. Tutson, Boeing Organization Designation Authorization, Authorized Representative, Fire Protection; Douglas E. Ferguson, Technical Safety Chief, Fire Protection, Technical Services and modifications; and Mike Madden, Deputy Pressurized Compartment Fire Marshal, Payloads Design This article is the third in a series exploring approach that goes beyond ensuring This article describes how Boeing the implementation of fire protection on individual parts meet fire property require- incorporates fire protection features and transport category airplanes. ments by looking at the integration of all materials into the airplane cabin that meet those parts on the airplane. This approach or exceed fire protection standards defined Two types of fires can affect an airplane uses the principles of material selection, by U.S. Federal Aviation Regulations (FAR). and its occupants: in-flight and post-crash. separation, isolation, detection, and control. an in-flight fire usually occurs as a result of These principles involve separating the a system or component failure or mainte- FIRE-PROTECTIVE MATERIALS three contributory factors to a fire (fuel, nance issue. A post-crash fire usually ignition source, and oxygen), isolating results from ignition of fuel released during Most materials used in the construction potential fires from spreading to other parts a crash landing. Boeing considers both of passenger compartment interiors are of the airplane, and controlling a fire should types of fires when designing for airplane required by the U.S. Federal Aviation one occur. Boeing uses both passive sys- cabin fire protection. Fire protection is one Administration (FAA) to be self-extinguishing tems (such as the use of noncombustible of the highest considerations at Boeing in (i.e., stop burning after the flame source or self-extinguishing materials) and active airplane design, testing, and certification. has been removed) or better. For example, systems (such as fire extinguishing systems). in designing an airplane’s fire protection electrical wire and cable insulation must be Fire protection features on Boeing airplanes features, Boeing uses a systems-level self-extinguishing. meet all aviation regulatory requirements as well as internal Boeing design requirements. 19 WWW.BOEING.COM/COMMERCIAL/AEROMAGAZINE Figure 1: Insulation blanket burn-through protection Fire-protective insulation blankets are designed to resist burn-through from a fuel fire next to the bottom half of the fuselage. 1 Halfway Line 1 3 2 Windows 3 Insulation 4 Steel Clip 2 2 2 2 2 2 5 Tape 6 Overframe Blanket 7 Between-Frame Blanket View looking outboard 4 5 4 5 6 7 View looking down Interior components of Boeing airplanes contribution of the insulation blankets to ■ Establish design features to minimize meet flammability requirements prescribed the propagation of a fire. Thermal/acoustic potential ignitions. in Title 14 Code of Federal Regulations insulation installed behind cabin interior ■ Establish design features to isolate poten- (CFR) Part 25. These components include: panels with the appropriate fire-resistant tial ignition sources from combus tibles properties can delay the onset of fire into the (e.g., electrical shutoff switches for ■■ Interior ceiling. cabin in the event of a crash (see fig. 1). in-flight entertainment systems). ■■ Interior sidewall panels. The insulation blankets, along with the ■ Establish design features to contain or ■■ Partitions. airplane skin, must be capable of resisting localize potential fires, including arrange- ■■ Galley surfaces and structure. burn-through from a fuel-fed post-crash ment, materials, and ventilation. Examples ■■ Exposed surfaces of stowed galley fire next to the bottom half of the fuselage include galley trash compartments, fire carts and standard galley containers. for a minimum of four minutes to allow stops behind monuments, and sidewalls. ■■ Large cabinets and cabin stowage passen gers to evacuate the airplane before compartments. burn-through can occur. ■■ Passenger seat material. FIRE DETECTION For materials in areas not covered by the ISOLATION AND SEPARATION Three types of smoke detectors are CFR requirements, Boeing design guidelines CONTROLS certified for use in the lavatories and crew are used to identify additional flammability, rest compartments, as well as in some smoke, and toxicity requirements. Boeing reviews the overall design of the galley complexes, purser work stations, The standards for flammability of insu- airplane at a systems level to further video control centers, and business lation blankets have improved over time. enhance airplane safety. This includes centers: ionization-area type, photoelectric- A recent requirement change calls for the the following based on established Boeing area type, and photoelectric-ducted type. enhancement of the fire-protective features design guidelines: A dedicated smoke detection system is not of insulation blankets in the event of an required in the occupied volumes of the in-flight or post-crash fire. The latest stan- ■ Identify potential ignition sources. main cabin due to the ability of passengers dard increases protection by minimizing the ■ Identify failure modes to ensure ignition and the cabin crew to recognize smoke. sources are minimized. 20 AERO QUARTERLY QTR_04 | 11 Figure 2: Ceiling-mounted smoke detectors Typical faceplate of a ceiling-mounted ionization smoke detector (left) and a photoelectric smoke detector (right). Ionization smoke detector Photoelectric smoke detector Ionization-area type. These detectors are Photoelectric-ducted type. These detectors CONTROL OF FIRES designed to detect the presence of ionized are similar to photoelectric-area type particles created by the combustion process detectors, but they are typically mounted Handheld fire extinguishers are provided as they are convectively carried through behind the walls of the protected space. throughout the airplane cabin for manual the lavatories or crew rest compartments They differ from the area detectors in that firefighting. boeing airplanes currently use in the event of a fire. They are typically fans draw air samples from the protected water or Halon 1211 fire extinguishers. mounted in the ceiling or upper sidewalls space into a series of air sampling ports in Boeing is working on a replacement for of the protected space (see fig. 2). the monument walls and ceiling, and then halon extinguishers, but it is not yet through an aluminum tube manifold to available. (For an in-depth discussion Photoelectric-area type. These detectors the detectors. Current production airplanes on halon, see page 13.) are designed to detect the presence of use the more advanced area detectors Halon 1211 fire extinguishers have a smoke particles in the air by reflection mentioned above, rather than ducted minimum Underwriters Laboratories rating of scattered light. They also rely on photoelectric detectors. of 5B:C. This type of extinguisher contains particles in the air being convectively Each smoke detection system has a approximately 2.5 pounds (1 kilogram) of carried into a sensing chamber where built-in electronic test capability switch. This Halon 1211, weighs about 4 pounds (1.8 kilo- light from a pilot lamp is transmitted allows for the system’s electrical and detector grams), and can be used on any fire likely to through a sensing chamber. If smoke is sensor integrity to be checked at any time. occur in the airplane, including paper, fabric, present, it will reflect light onto a photocell Detection of smoke is affected by electrical, or flammable fluids. Halon 1211 and trigger an alarm. Newer production compartment volume and contour, air extinguishers have also been successful in airplanes use photoelectric detectors based distribution, and the amount and buoyancy extinguishing fires behind the sidewall panels. on an advanced smoke sensor utilizing of the combustion particles. Boeing con- Water fire extinguishers haveFAA two discrete wavelengths to determine ducts extensive laboratory and flight testing technical standard order (TSO)-C19c the presence of smoke and to distinguish to determine the best location for the certification approval. These units are between smoke and nonsmoke aerosols. detector sensors to enable them to most intended to com bat fires involving combus- These are also mounted in the ceiling or effectively detect smoke under all conditions. tible materials such as paper and textiles. upper sidewalls of the protected space. 21 WWW.BOEING.COM/COMMERCIAL/AEROMAGAZINE Figure 3: Typical fire extinguisher locations Fire extinguishers are located throughout the passenger cabin with locations designed for easy access in an emergency. Halon Water Water For lavatory fire Halon extinguishers, see figure 5. Halon Halon Halon Halon Fire Extinguisher ■■ Halon [6] ■■ Water [2] Figure 4: Distribution of handheld Halon 1211 or equivalent fire extin- Crew/attendant rest compartments, purser fire extinguishers guishers are spaced throughout the cabin work stations, video control centers, and the number of handheld fire extinguishers and easily accessible from the aisle or business centers. at least one Halon 1211 on passenger