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quantity. Over time, and even from initial installation, the components deteriorate and are notorious for caus- ing inaccurate readings. I’ve owned some piston aircraft, including my 2005 SR22, that read very accurately for over 5,000 hours, while other airplanes were notoriously inaccurate. The variability could be frustrating, and a potential safety issue for pilots. Scott Philiben and his team at CiES in Bend, Oregon, sought to change that.
Scott, president of CiES and engineer by training, has former experience designing aircraft oxygen systems and other components. He was approached by Cirrus Aircraft in 2010 to see if he could develop a “better mousetrap” – in this case, fuel senders. Cirrus, being very technically focused, wanted to provide more accurate fuel level in- formation since many owners were noticing annoying quantity variations similarly seen in other piston aircraft.
CiES worked on a very novel design that, while it may appear simple, actually involves a significant amount of engineering innovation. Scott believed that one of the design problems was using a resistive element sloshing around in the fuel (at extremely low voltages and not a fire hazard) that was prone to errors. The new sender design they created has no electrical components within the tank. CiES has developed a magnetic-resistive fuel sender with the sensor external to the fluid it is measuring. As the float moves with the fuel level, a corresponding change in the magnetic field is sensed by an external electronic circuit. This extremely slight change in the magnetic field as the float arm changes position can be used to indirectly sense the fuel level.
Cirrus implemented the new design from CiES in its 2012 aircraft, and soon after, it was available as a popu- lar retrofit for the existing SR20 and SR22 fleet. Scott didn’t stop there. He then expanded to other OEMs in 2014 when Tecnam and Vulcan Air used the senders in their production aircraft. One of their next projects was the Piper Malibu and Mirage aircraft, which have a float placement design that complicates even the traditional inaccurate senders. Piper Malibu and Mirage owners
would occasionally cringe at the inaccurate fuel read- ings, sometimes trying to solve the problem by replacing the senders with new ones of the same design. This solution often didn’t work well. The CiES engineers came up with a de- sign, working with several aircraft owners, to offer a better solution. It took several attempts, however, the resulting fuel sender design has proven
to be an effective alternative to the previous design. Now available on over 600 airframes, more than 100,000 fuel senders have been produced. I have them in one of my aircraft, a Cessna T206H, and I can attest to their accuracy compared with the original factory probes. While I also have a fuel totalizer in the Garmin G1000 NXi, it is impor- tant for me to also have accurate fuel tank information. The totalizer will tell you how much fuel you have burned and indirectly what you have remaining. Fuel gauges inform the pilot of the actual fuel in the tanks, which can be very important in the case of a potential fuel leak or inaccurate initial information provided to the totalizer at engine start.
December 2022 / TWIN & TURBINE • 9