How New Optical-Based Systems Will Transform Aircraft Fuel Management

When the gas turbine engine first released to the aviation market, aircraft capabilities as we knew them were drastically changed. With such engines, aircraft could produce massive amounts of thrust from fuel combustion, allowing airliners to travel great distances with high speeds. Nevertheless, these aircraft and their respective engines require vast amounts of fuel, often ranging from 35,000 to 85,000 gallons. While aircraft may be filled with a little more fuel each trip than they need to successfully carry out a flight operation, it is still paramount that pilots precisely monitor and log fuel consumption rates for safety, weight and balance efficiency, and more. As accurately monitoring fuel is critical for flight operations, companies across the world strive to constantly improve our abilities to conduct such measurements. In recent years, the Fluid Systems Division of Parker Aerospace has partnered with Oxsensis Ltd. to create an optical-based system that is set to transform how pilots perform in-flight fuel monitoring.

Currently, a majority of aircraft utilize capacitance-based technology which has proven to be a reliable and safe method of fuel gauging. Capacitance-based fuel measurement consists of 20 to 30 capacitance probes placed in an array, mounted throughout fuel tanks vertically to serve as variable capacitors. Meanwhile, the fuel is the dielectric, causing the fuel-to-air ratio in contact with the probe to adjust as fuel levels change. This results in the probe’s capacitance level to adjust, permitting a system measurement of the probe in regards to its “wetted length”. Wetted length of probes is a useful measurement, as a full tank will present higher values of probe wetted length as compared to an empty tank. This data can then be combined with other information, including fuel density and temperature, resulting in a computed fuel quantity for the pilot to perform in-flight fuel monitoring. Such aircraft fuel measurement systems prove to be very reliable, but they can be highly time consuming and expensive to initially install within fuel tanks on top of the required wiring for data transfers.

Through the joint venture between Parker Aerospace and Oxsensis, the two companies intend to design a silica-based optical high-accuracy pressure sensor (SOHAPS) system that could fully replace the capacitance probes of current systems. In lieu of such probes, the SOHAPS system would require three non-electric, electromagnetic interference (EMI) immune optical sensors that would be in place to gauge fuel system pressure. Currently still under development, the technology is slated to provide the next generation of aircraft with next-gen solutions for fuel gauging.

As compared to current capacitance based fuel measurement, SOHAPS systems prove to be just as accurate, all while providing a number of improvements. Among its various advantages, the SOHAPS system touts a much more simplistic design, a lower amount of fuel system sensors, shorter installation time requirements, lower maintenance costs for upkeep, is immune to electromagnetic interference, and is intrinsically safe. Such technology has undergone endurance testing in land based gas turbine applications, proving to be a successful endeavor thus far. Such technology also proves to provide benefit to a wider range of systems outside of fuel tanks, possibly being able to be used for hydraulic systems, landing gear, lubrication pumps, and other similar systems. As the technology continues to be developed, Parker Hannifin has made their intention to investigate such possibilities clear.

As compared to other initiatives to improve aircraft fuel measurement systems, the SOHAPS fuel measurement system proves to be different from the rest through the joint expertise of Parker Hannifin and Oxsensis. As compared to others, Parker Hannifin has proven their ability in regards to the engineering and design of fuel systems, integration, and qualification capabilities. Meanwhile, Oxsensis brings their one-of-a-kind optical pressure sensor abilities to the table. To further separate their developing technology from the rest of the herd, SOHAPS also provides remaining fuel amounts with the measurement of fuel tank pressure. Coupled with fiber optic cable technology and a single onboard computer, the data may be relayed to the pilot with ease.

The fuel system sensors developed under the SOHAPS project also prove to operate with much more precision as compared to current electrical pressure sensors. On top of that, they also may provide efficient results while under conditions such as low-temperatures and high amounts of vibration. With their use of fiber optic cable technologies, the SOHAP system can conduct its pressure readings and fuel volume data transmissions without the fear of electromagnetic interference, also being devoid of any conductive or metal materials. This proves to be beneficial for concerns of electricity conduction due to strikes of lightning, due to the lack of any metal wires being present within aircraft fuel tanks.

Perhaps one of the most important advantages, as discussed previously, is SOHAPS’ ability to provide in-flight fuel monitoring with much more simplistic hardware and configurations. With a decrease in needed parts and systems to successfully set up such aircraft fuel measurement systems, the SOHAPS system reduces costs, manufacturing, part numbers, and general complexity. Relay electronics devices that are needed by the current systems for the transmission of data for interpretation are also removed, replaced with a single onboard computer with accompanying fiber optics technology. With the fact that SOHAPS can possibly extend its use to other systems and components as well, the total weight of the aircraft may also be reduced, thus further increasing cost saving capabilities.

When it comes time to begin sourcing the aircraft fuel measurement systems and other equipment that you need for your operations, Aviation Orbit has you covered with everything you are searching for. Aviation Orbit is owned and operated by ASAP Semiconductor, and we can help you find the aviation, NSN, and electronic parts that you are searching for, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we're always available and ready to help you find all the parts and equipment you need, 24/7x365. ASAP Semiconductor is an FAA AC 00-56B, AS9120B, and ISO 9001:2015 certified enterprise. For a quick and competitive quote, email us at or call us at +1-509-449-7700.


December 7, 2023
June 30, 2022

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