Increasing Flight Safety and Survivability by inerting fuel tanks: OBIGGS using Membrane Technology applied to Helicopters, Fighters and Cargo.
Nicolas SCHMUTZ
Studies about inerting fuel tanks were launched after the American government realized that 50% of aircraft losses during Viet Nam Conflict were due to riffle bullets igniting the fuel tanks.
The goal of inerting is to add components to the ullage (ullage is the mixture of gas and fuel vapour present inside the tank) that absorb energy and do not release energy by reacting. Hence inerting will avoid the explosion of the fuel tank.
Many components were tested. Unfortunately, Halon is not viable any longer because of its damaging effect on the ozone layer. CO2 or Liquid Nitrogen have also been tried. Nevertheless, due to problems as availability and logistics, these components will not be selected for new applications.
Today the strategy in the aeronautical field is a On Board production, using directly bleed air generated by the aircraft to produce Nitrogen. On Board Inert Gas Generating System (OBIGGS) use either the PSA or the Membrane technology. Today, technological breakthroughs performed by Air Liquide Research Centers place the Membrane as the best way to produce Nitrogen On Board. Indeed, its recovery, its productivity, its mass of air separator per flowrate unit, its MTBF overbeat any competitor.
Equipment based on the Membrane technology are already installed since the early 90's On Board Fighters, Helicopters and Cargo aircraft. Furthermore, as a consequence of TWA 800 mishap, Aeronautical Authorities consider inerting Commercial Airliners.
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