Fire protection systems on aircraft usually consist of two separate operating systems with associated controls and indicators. One system is for fire or overheat detection and the other is for fire suppression or extinguishing. In some cases the systems can be interconnected so extinguishing takes place automatically when a fire is detected whereas the extinguishing was manual in early days.
Followings are some main facts that a Fire Detection and Extinguishing system must ideally be capable of,
- The fire warning system must accurately indicate that a fire has been extinguished and indicate if a fire re-ignites even after the first attempts of extinguishing.
- Since the system is exposed to all the critical areas of aircraft that must be durable and resistant to damage from any oil, water or other fluids that may be present in the area where it is installed.
- The system must include an accurate and effective method of testing so that the flight crew and engineers can check the integrity of the system.
- The system must be easily inspected, removed and installed.
- The system and its components must be designed so that the possibility of false indications is unlikely.
- The system must require a minimum of electrical power and must operate from the aircraft electrical system without the use of inverters or other special equipment to ensure safe operation even in some electrical system failures.
Detection systems must be capable of providing rapid detection of fire or overheat conditions and warn the crew by means of a red light and an audible signal on the flight deck indicating the area where some corrective action is required. However Fire detection systems will not automatically operate the main power unit extinguishers which may cause the main power plants(engines) to shutdown all of a sudden . But, in some installations the fire detection system may shut down APU and may operate on APU fire extinguisher automatically.