A major fractional business jet operator found that one particular type of aircraft seemed very susceptible to jet fuel fungus contamination. The maintenance engineers reported that they could not detect the jet fuel fungus using the FUELSTAT® resinae test kits which gave accurate readings on all other aircraft types. A study into the problem found two causes. The first problem was that this type of aircraft had a refuelling point on top of the wing. This resulted in much larger volumes of water finding its way into the tank than aircraft with under-wing refuelling points.
The extra water gave the jet fuel fungus a much better chance of establishing itself and creating a problem. The second issue was that the engineers were draining the water out of the tanks prior to testing and then using the fuel in the FUELSTAT® resinae test. Unfortunately, all evidence of jet fuel fungus contamination was drained away with the water and an incorrect reading was obtained. The airline introduced more frequent water drains on this type of aircraft and started using the water phase for the FUELSTAT® resinae tests. The number of cases of jet fuel fungus contamination dropped significantly and the results obtained from the FUELSTAT® resinae tests gave accurate results from then on.