OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Sustainment
OBJECTIVE: Develop an accurate oxygen sensor that can continuously operate in a fuel tank ullage environment with minimal maintenance required.
DESCRIPTION: On-Board Inert Gas Generator System (OBIGGS) is used to inert areas of the aircraft to reduce the risk of fire or explosions. Fuel tanks may utilize OBIGGS for both survivability and lightning protection, which require below 9% and 12% oxygen by volume, respectively. Feedback of the fuel tank ullage oxygen percentage would allow aircrew to select the proper oxygen concentration set-point for the situation, and receive feedback that the threshold has been reached. Due to requiring clean working environments, currently available oxygen sensors are not suitable for a fuel tank application. The desired oxygen sensor would be able survive in a fuel tank environment, accurately and continuously measure the oxygen concentration, maintain a small form factor, and require infrequent maintenance or repairs. The designed sensor would need to withstand the vibration loads and environmental requirements of a typical fighter aircraft flight profile, and meet the appropriate electrical criteria of a fuel tank environment. The oxygen sensor should be usable on any aircraft that is inerting fuel cells.
PHASE I: Identify the mechanism for the oxygen sensor that can withstand jet fuel and vapor. Develop an experimental bench top design to show the basic functionality and compatibility with the environment. Verify that the oxygen concentration readings are accurate in a lab setting. Develop a plan to address any technical hurdles with the design. The Phase I effort will include prototype plans to be developed under Phase II.
PHASE II: Produce an on-aircraft prototype of the oxygen sensor. Verify that size, power, and interface requirements are met. Perform appropriate environmental testing. Validate and demonstrate the sensor in a testing environment representative of a fuel tank.
PHASE III DUAL USE APPLICATIONS: Produce a final design that is ready for flight test. Provide documentation regarding sensor accuracy, operational limits, and failure analysis. Provide appropriate qualification documentation, including (a) environmental testing, (b) electrical testing/analysis, and (c) explosive atmosphere qualification.
Commercial aircraft fuel tanks could use oxygen sensor technology to ensure the tanks are inert. Additional applications may exist for storing commercial flammable liquids.
- Cavage, W. (2009). Measuring oxygen concentration in a fuel tank ullage. U.S. Air Force T&E Days 2009. https://doi.org/10.2514/6.2009-1743
- Goswami, K., Sampathkumaran, U., Alam, M., Tseng, D., Majumdar, A. K., & Kazemi, A. A. (2006). Ormosil coating-based oxygen sensor for Aircraft Ullage. SPIE Proceedings. https://doi.org/10.1117/12.684769
KEYWORDS: Oxygen sensor; On-Board Inert Gas Generator System; OBIGGS; fuel tank; inert; oxygen; sensor