Learning Objective: Identify operating principles, components, and maintenance procedures for fire extinguishing utility systems.

As a general rule, fire extinguishing systems are incorporated only in multiengined aircraft. These systems are designed primarily for extinguishing engine fires; however, on some aircraft, provision is made for protecting the aircraft heater (or heaters), as well as the engines. The extinguishing agent is stored in cylinders mounted at various places within the fuselage, wings, nacelles, or landing gear wells, and is directed to the area of fire through a system of tubing and various control valves. A switch or pull' handle, located at the pilot's or flight engineer's station, is used in releasing the extinguishing agent when a fire occurs. The inspection and maintenance of aircraft fire extinguishing systems is an important responsibility of the AME.

TRIFLUOROBROMOMETHANE (CF3Br)

CF3Br (the chemical symbol for trifluoro-bromomethane) is a fluorinated hydrocarbon. It is the most common extinguishing agent used in aircraft fire extinguishing systems. It is a more efficient extinguishing agent than CO2, and under normal atmospheric pressure and temperature, it is a colorless, odorless, and tasteless gas. It exists as a liquid only when contained under pressure. CF3Br is nontoxic, noncorrosive, leaves no residue, does not deteriorate with age, is an electrical insulator, and goes farther than CO2.

NOTE: CF3Br is very volatile. It is nontoxic but a danger of suffocation exists because, like carbon dioxide, CF3Br replaces oxygen when breathed. Among the many fire extinguishing

Figure 1-22.- Rain repellent system.

agents, only CF3Br will be discussed in this chapter. The E-2 aircraft uses (fig. 1-23) a typical CF3Br fire extinguishing system. The system consists of a container assembly, distributing tube assemblies, discharge indicators, and necessary tubing and electrical equipment.