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The Aerospace Recommended Practices of this document are intended for nitrogen-based Flammability Reduction Means (FRM) implemented on transport category, turbine powered airplanes. The recommended practices herein, therefore, relate only to the transport category aircraft, and focus specifically on contemporary inerting systems equipment. Such systems are referred to a Fuel Tank Inerting Systems (FTIS) in this document. This document does not cover the following: Military aircraft applications Air separation technologies other than hollow fiber membrane (HFM) and pressure swing adsorption (PSA) Inerting of conventional unheated wing tanks or aircraft dry bays Expected future technology solutions for the generation of inert gas. The advice contained in this document is aimed towards providing aircraft manufacturers with guidance on the key issues associated with contemporary aircraft fuel tank inerting systems to supplement the guidance in FAA Advisory Circular AC 25.981-2.

An airplane fuel tank inerting system provides an inert atmosphere in a fuel tank to minimize explosive ignition of fuel vapor. This SAE Aerospace Information Report (AIR) deals with the three methods of fuel tank inerting systems currently used in operational aircraft: (1) on-board inert gas generation systems (OBIGGS), (2) liquid/gaseous nitrogen systems, and (3) halon systems. The OBIGGS and nitrogen systems generally are designed to provide full-time fuel tank fire protection; the halon systems generally are designed to provide only on-demand or combat-specific protection. This document also addresses other design considerations that affect fuel tank flammability such as fuel tank pressure and other methods for reducing fuel tank flammability. This AIR does not treat the subject of explosion suppression foam (ESF) that has been used for fuel tank explosion protection on some military aircraft. ESF is also available for retrofit for commercial airplanes.