Aircraft fire extinguishing systems: replacing the halon
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About the author
Maimuna Taal is the Technical Officer Airworthiness in the Air Navigation Bureau of ICAO. She is an Aerospace Engineer and a holder of an Airframe and Powerplant Engineer License from the US Federal Aviation Administration (FAA) with over 20 years experience in the field of Civil Aviation Safety oversight related to continuing airworthiness. Before joining ICAO, she held the position of Director General of the Gambia Civil Aviation Authority GCAA) where she was responsible for the full range of aviation regulatory activities. Maimuna is a recipient of the 2007 Flight Safety Foundation President’s Citation for her work in improving aviation safety in Africa.
Traditionally, halogenated hydrocarbons (halons) have been the only fire-extinguishing agents used in civil transport aircraft as fire extinguishers because they are effective on different kinds of fires and they are very lightweight. However, due to their high ozone depletion, the Montreal Protocol on Substances that Deplete the Ozone Layer called for an end to their production by 1994 in developed countries and by 2010 in developing countries.
As a result of this international agreement, production of halon is prohibited, and halon supplies are diminishing. The updated breakout of Global Inventories of Halon 1301 from the United Nations Environment Programme (UNEP) Halons Technical Options Committee (HTOC) 2018 Assessment Report is shown below.
ICAO has mandated the use of Halon replacements in fire extinguishers used on civil transport aircraft. Several ICAO Provisions already exist in Annex 6 — Operation of Aircraft and Annex 8 — Airworthiness of Aircraft that stipulate requirements for the use of a non–halon alternate agent for fire suppression.
The Halon replacement cut off dates in ICAO SARPs contained in Annex 6 and 8:
Extinguishing systems in civil aircraft
ICAO SARP Cut-off date
Lavatory fire extinguishing systems
31 Dec 2011
|Portable fire extinguishers||31 Dec 2018|
|Engine and APU fire extinguishing systems||31 Dec 2014|
|Cargo compartment fire extinguishing systems||
28 Nov 2024
At present, halons are used for fire suppression on civil aircraft in four extinguishing applications as shown above. Worldwide, there are many States and organizations testing alternatives to halon. Unfortunately, there is no single substance which can be used for all of the extinguishing applications. Therefore, aviation will have to use different types of extinguishers for each application.
The aviation industry continues to use halon today under an exemption to the international agreement because of its unique situation. This cannot and should not continue indefinitely.Halon is currently available for aircraft use by recycling existing supplies; Although ICAO member States have taken measures to mitigate contamination, the potential risk of contamination of the reserves remains. In recognition of these issues and their potential impact on safety, transitioning promptly from halon to safe and effective halon alternatives now become urgent.