O2 Sensor for the Ullage of an Aircraft Fuel Tank

Aircraft fuel tanks still remain a survivability concern because of the possibility of accidental or intentional ignition which can cause a fuel tank fire/explosion. As a result of the TWA 800 incident and in response to potential fuel tank threats, the National Transportation and Safety Board (NTSB) and Federal Aviation Administration (FAA) had issued a safety recommendation, specifically to reduce the risk of ignition of flammable vapors present in aircraft fuel tanks. Currently, the best method for reducing ignition vulnerability in a fuel tank is to displace the oxygen (O2) in the fuel tank ullage with nitrogen-enriched air (NEA) that can be produced by the Onboard Inerting Gas Generation Systems (OBIGGS).  Optical sensing technologies, i.e., absorption spectroscopy and chemical fluorescence were two seemly competing O2 techniques. ESI is proposing “A Real Time O2 Measurement System” for aircraft ullage monitoring using an optical concept based on absorption spectroscopy, this approach works on multiple wavelengths and can account for fuel films/wetting of the optics, thereby correcting for the unrelated attenuated signals during aircraft maneuvers.