Fuel tank inerting is the process of replacing the flammable gas space above the fuel tank (ullage) with a non-flammable atmosphere. Fuel Tank inerting systems in aircraft displace the oxygen in the tank with nitrogen. A Cobham On-Board Inert Gas Generating System (OBIGGS) provides an unlimited nitrogen supply, is low weight, has a low life-cycle cost and negligible logistics impact.
There are two technologies available for OBIGGS systems; Hollow Fiber Membranes (HFM).and Pressure swing adsorption (PSA). Cobham offers both types of technology.
Pressure swing adsorption (PSA) processes rely on the fact that under pressure, gases tend to be attracted and adhere to solid surfaces, or "adsorbed“. The higher the pressure, the more gas is adsorbed. This is the same technology that is used in Cobham On-Board Oxygen Systems (OBOGS). Pressure swing adsorption technology:
• Performs well over broad range of inlet pressures & temperatures
• Excellent response time from a cold soak start-up condition
• Requires inlet air filtration to remove water and large particulates
• Not susceptible to hydrocarbons or ozone
• PSA approximately 50% heavier for a given volume
• Routes waste gas overboard
Cobham PSA platforms include rotorcraft (AH-64, AH-1Z, UH-1Y, MH-47E, MH-60K, RAH-66) and fixed-wing aircraft (C-17 OBIGGS I, V-22).
Hollow Fiber Membranes (HFM) use the 
permeation of oxygen through the walls of
the membrane to ensure that nitrogen
enriched air (NEA) is provided to the fuel tanks. Hollow fiber membrane technology
• Performs best with high pressures (>40 psig)
• Performs best with high operating temperatures (160 – 210°F)
• Relatively slow responding to changes in temperature (large thermal mass)
• For optimal performance, tight temperature control is needed
• HEPA filtration required
• Susceptible to hydrocarbons and ozone in bleed air
• Routes waste gas overboard
Cobham HFM platforms include commercial aircraft such as the 787, MRJ. Cobham HFM OBIGGS are also installed on military platforms like the CH-53K Sea Stallion and fixed wing platforms C-17 OBIGGS II.
Cobham has been developing OBIGGS technology since 1985. More than 3,000 aircraft (over 5 million hours!) are flying today with Cobham OBIGGS technology. Wide platform options along with Cobham’s extensive experience and capabilities will ensure that the appropriately sized and configured system is designed for the program.