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Measuring at the Speed of Light

Fuel makes up 19% of airline operating cost. With global spend at $124b in 2016, cutting fuel load, even by 1%, means substantial savings.

When it comes to accurately measuring fluids in a rapidly changing extreme environment, there are plenty of variables to contend with. Aviation fuel is primarily stored in the wings so as the aircraft climbs, banks or experiences turbulence, the levels are always shifting. Furthermore, not only do
changing temperatures affect fuel density but as fuel is consumed, air enters the tank introducing moisture. It condenses at low temperature, gathering as water at the bottom of the tank.

The Meggitt solution is classic smart engineering. Our breakthrough digital gauging system bounces electromagnetic pulses off the fuel surface to provide the most accurate fluid reading available in aerospace today.
The waves last just a few trillionths of a second,€ says Sam Sher, Business Development Manager at Meggitt Sensing Systems Orange County. €œWe were the first company to use this technology for fluid measurement in aerospace.

Thanks to a smart network of sensors and software which constantly compensates for aircraft attitude as well as fuel density, moisture content and temperature, the gauge can measure fluid level variations by timing the electromagnetic pulse reflections propagating at nearly the speed of light. €œThat means we can determine the quantity of fuel in tanks to within 2.5mm and keep the pilot informed of how much fuel they have on board at all times.

Saving money on fuel and maintenance

Unlike traditional gauges which use capacitance probes or float switches, the electromagnetic waves used in Time Domain Reflectometry (TDR), carry additional information that can be processed and utilised for Integrated Vehicle Health Management (IVHM) applications. We can even see and measure if there are multiple layers of liquids. Distinguishing between fuel and water helps operators optimise the schedule for draining water from the tanks, ensuring no extra weight is carried during the flight thereby improving fuel burn,€ explains Sher.

Maintenance on condition instead of on schedule also saves time when no action is required.
Further, TDR is not fluid specific: it can be used beyond the fuel tank to determine quality and quantity of fluids in engine, gearbox, or hydraulic fluid. When contamination occurs, it does not impact measurement accuracy, increasing aircraft dispatch reliability.

Read more about TDR and fluid sensors

Did you know?

Our first TDR fuel gauges were installed in Cessna piston engine aircraft in 2008. Over 10,000 sensors have been sold since, operating in over 4,000 aircraft.

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