WARNING When approaching a battery that is in a thermal  runaway  condition,  aircraft  rescue fire-fighting personnel must work in teams of two and must be attired in full protective clothing, with extinguishing agent available for instant use. COMPOSITE MATERIALS The following text discusses the advantages and disadvantages of using composite materials in aircraft construction. WARNING Inhalation of composite fibers resulting from aircraft fires and/or aircraft material damage may be harmful to personnel. Respiratory protection must be worn when personnel are exposed to these potential hazards. Composite Materials Reinforced with Carbon/Graphite Fibers Composite materials that are reinforced with carbon/graphite fibers provide superior stiffness, a high strength-to-weight ratio, and ease of fabrication. As a result, this material is being used extensively in advanced aircraft, such as the AV-8  Harrier, to replace heavier metal components. Unfortunately, carbon or graphite fibers can be released into the atmosphere if their epoxy binder burns. Once free, these small lightweight fibers can be transported up to several miles by air currents and, because of their high electrical conductivity, can damage unprotected electrical/electronic equipment. Until such time as more information is known, aircraft crash and fire-fighting units must attempt to extinguish fires involving carbon-fiber-reinforced composites as quickly as possible and to provide maximum containment of the aircraft debris. The containment and cleanup function is extremely important and must be treated as a special hazard prevention measure. Accordingly, the practices for extinguishing, containment, and cleanup, as stated in paragraph  6.7  of NATOPS, U.S. Navy Aircraft Firefighting and Rescue Manual, NAVAIR 00-80R-14, should be observed when an aircraft crash/fire incident occurs that involves any aircraft that contain carbon-graphite  fiber  composites. Any  aircraft incident involving fire on these types of aircraft must be considered to have potential contamination hazards until positively identified to the contrary. Composite Materials Reinforced with Boron/Tungsten Fibers Composite materials reinforced with boron fibers also provide superior stiffness, a high strength-to-weight ratio, and ease of fabrication. This material is being used in advanced aircraft, such as the F-14, F-15, and F-16, to replace heavier metal components.  Unfortunately,  boron  fibers  can  be released if their epoxy binder burns. Boron fibers pose less of a problem to unprotected electrical equipment than carbon or graphite fibers, because boron fibers are much heavier and are less likely to become airborne. Also, boron fibers are much less electrically conductive. However, loose boron fibers are stiff and sharp, and thus pose handling problems. The extinguishing, containment, and cleanup practices for boron fibers are the same as those previously outlined for carbon or graphite fibers. AIRCRAFT FIRE AND PERSONNEL HAZARDS Not every crash results in fire. The responsibility of the crash fire fighter does not end when fire fails to occur. Serious actual and potential fire hazards may have been created, which must be eliminated or minimized without delay. The greater the damage to the aircraft, the greater the possibility of fuel spillage. A spark or a hot engine part could ignite fuel vapors and set off a full-fledged fire. You must take all precautions to prevent accidental ignition. Personal laxity or unfamiliarity with ordinary preventive measures can cause a delayed fire, which could  endanger  personnel  who  would  otherwise survive a disaster. Engine Accessory Section The most common source of crash fires is the engine compartment, particularly the accessory section. Take steps to prevent ignition of fuel vapors by hot exhaust stacks and collector rings. CO₂  discharged through the cooling flaps, air scoop, or inspection doors is an effective precaution. CO₂ will cause no damage to the engine or its accessories. 12-15