On-Line Aircraft Fuel Tank Oxygen Sensor

Military aircraft protect fuel tanks from explosion following ballistic impact by reducing the O2 content of the gases in the head space above the fuel, conventionally known as ullage, from typical ambient levels of 21% to about 9%. Reliable sensors are needed to monitor and control the ullage O2 under the widely variable aircraft operating conditions. To meet this need cost-effectively, Physical Sciences Inc. (PSI) proposes to build on our previously installed F-18 sensor by adapting a 3 kg battery-powered near-infrared Tunable Diode Laser Absorption Spectroscopy (TDLAS) platform technology. With this optical technique, only passive materials contact the fuel. A few low-power intrinsically-safe opto-electronic components mount externally to the fuel tank. These components communicate electrically with a compact control unit, installed in the aircraft electronics stack, which provides outputs to the O2 control system and to a cockpit indicator. The Phase I effort will demonstrate the feasibility of implementing the necessary innovations and the ability to measure O2 throughout the ranges of temperature and pressure associated with military aircraft flight envelopes. Phase II will result in a deliverable prototype.