Improved fuel level sensors

Effectivity: Challenger 604/605/650 aircraft

ATA: 28-41

By: Marc Cadotte - Technical Services

An investigation of returned fuel level sensor units (fuel level sensors 722610 and 722599, Bombardier part numbers 601R62304-3 and -5) confirmed an internal failure at the component level of the solder weld on various electrical parts. One of the failure causes was linked to the thermal expansion of the compound used in the sensor to seal the unit.

The original compound has since been banned due to its environmental effects and has been replaced by a new compound. Additional characteristics and advantages of the new compound are a better dielectric strength and a lower thermal expansion coefficient.

This new, more efficient compound lowers the stress on the internal components caused by thermal expansion during the phases of aircraft flight. The production of the modified sensors with the new compound starts at serial number 11000. The part numbers of the new sensors have not been changed, but an amendment letter will be added on the identification plate of the sensor showing the upgrade.

Service Information Letters (SILs) 722610-28-002 and 722599-28-003 from Safran have further details and are available on the Bombardier Customer Portal. The new level sensors will be available via attrition once the existing stock is depleted.