Fire protection system is a set of equipment of fire alarm and fire extinguishing intended to notify air crew about the emergence and extinguishing of fire on board.
The possibility of a fire on board of aircraft is defined by several factors, including:
- the presence on board of a large amount of combustible materials;
- ignition of fuel and oil in case of getting them onto the hot surface of the engine;
- aviation accidents that cause degradation of aircraft units;
- damage of wiring;
- explosion in the space above fuel in fuel tank in case of fire.
Especially fire-hazardous parts of aircrafts are engines, fuel tanks and areas where there is a potential risk of the possibility of fire due to the breaking of individual parts of construction.
According to the principle of operation, fire systems of different aircraft are about the same and divided into the alarm system and fire extinguishing system.
Alarm system is designed to detect fire in-time, notify pilot of aircraft about it and automatically turn on the fire extinguishing systems.
Fire extinguishing systems require accommodation on board of aircraft of required number of extinguishing fluid and provides supply of i from cylinders to fire.
Fire protection equipment of aircraft:
- detection and extinguishing of an engine fire
- system smoke detection in the avionics equipment;
- system of smoke detection and fire extinguishing in cargo and passenger compartments of aircraft;
- Hand fire extinguishers.
Each fire alarm systems (Fire Detection Unit - FDU) contains at least two independent channels of fire detection, each of them contains group of sensors. Near each engine at least two tanks with ire exstinguishing liquid are placed. Summarised simplified structure scheme of fire protection is shown on Fig.188.
Fig. 188 . A simplified scheme of fire protection
Control of smoke presence in different parts of aircraft and avionics units is performed using a large number of smoke detectors connected to the unit of smoke detection (Smoke Detection Control Unit - SDCU). In case of presence of smoke SDCU notifies system of aircraft equipment and displays information about location of smoke source to the pilot through EFIS.
In addition, in the case of landing without landing gear extended, fire protection system is triggered by sensors of hitting the ground surface to reduce the possibility of fire.