Avionics Compartment Fire Extinguishing on the Commercial Airplanes

In all commercial and non-commercial airplanes, there is no fire detection or fire extinguishing system in the avionics bay. Racks, are cooled by ambient or conditioned air. Each rack will include several circuit boards, which in case of overheat, can burn with the risk of igniting the surrounding components and structures, thus jeopardizing flight safety. It becomes therefore important to provide fire detection and fire extinguishing capabilities in the aircraft avionics compartment. The approach proposed in this paper, extracts nitrogen from ambient air by mean of the Air Separator Module, then nitrogen is routed to the avionics compartment racks, and enters inside the component and extinguishes the fire. The temperature of the nitrogen is adjusted to be around 25°C to prevent thermal shock effects on the circuit boards before being injected in the avionics compartment. A series of experiments conducted, aimed at gathering information by using dry nitrogen under different pressure values to extinguish different size of fire. The analysis of the experiment research showed that increasing nitrogen pressure, resulted in quicker extinguishing time. This is because nitrogen under higher pressure, quickly decrease the oxygen concentration in the air for the fire already in the process of combustion. Nitrogen does not conduct electricity thus cause no short circuits during and after the extinguishing process, therefore, they are ideal for use in the electronic systems.