Possibilities of COTS ultrasonic fuel quantity measurement

The article deals with possibilities of utilization of modern industrial sensors for aircraft fuel quantity measurement. The purpose of the fuel quantity measurement in aircraft with either stationary or rotary wings is to provide information about the total amount of fuel and fuel variations under all aircraft attitudes and with all types of fuel. In aircraft technology, there are especially two basic methods of fuel quantity measurement used that are based on measurement of fuel level. Both methods are contact measurement methods and the fuel gauge is always in contact with fuel. The older, easier and cheaper method is based on float level sensors. Modern and more precise method is based on capacitance level sensors. The measured fuel level is then converted to volume or weight of the fuel and displayed on a fuel indicator in the cockpit. Both methods have some limitations and for that reason another fuel level measurement methods have been introduced onboard. Our practical experiments deal with possibilities of COTS ultrasonic sensors utilization for fuel gauging inside small aircraft fuel tank. Ultrasonic fuel level measurement is based on reflecting sound energy at an interface of liquid and air. Tested operating conditions include influence of aircraft attitude changes, mechanical forces changes and temperature changes on whole measuring systems. Fuel volume is also measured by reference capacitance fuel gauge during practical experiments. Experimental results lead to error quantification of COTS ultrasonic fluid level measurement and following technical measures to minimization of systematic errors.