Foggy Fuel Befuddles Some

A warm welcome to NATA Safety Net guest blogger Michael Mooney, VP & Chief Risk Officer with EPIC. This blog is part one of two.

Periodically in winter months we receive reports of cloudy jet fuel and/or free water in samples taken during truck transport deliveries at airports. The root cause of many of these reports is the fact that all fuel holds water in a dissolved invisible state and when it is cooled the water becomes “free” and visible to the naked eye. Water will fall out of suspension at the bottom of the sample bucket or remain suspended in the fuel like a haze or fog.

This temperature drop and release of water could be the result of the tanker truck driving from a warmer area into an area of colder temperatures, driving over a mountain pass, driving long distances at night, or parking overnight exposed to wind and cold. One customer located in a mountain resort area was supplied directly from a refinery located in the valley where the fuel was still relatively warm and was loaded into transport trucks and driven to an airport where it was much colder. Once the truck arrived the operator sees the hazy fuel in several samples and wants to reject the load, failing to consider the fact that what they were seeing was perfectly normal although admittedly frustrating. The reality is that in these extreme cases involving major temperature changes you will not be able to draw clear samples after just ten minutes of settling time.


FAA Advisory Circular AC 150 5230-4 states “as fuel is cooled, water comes out of solution at a rate of about one part per million per degree Fahrenheit (1 ppm/degree F).”  This has nothing to do with the quality of the aviation fuel. Water is present in all fuel in a dissolved state and some will remain no matter how many times it is filtered, settled, or sumped. Based on the FAA ratio, an 8,000 gallon truck load of jet fuel that drops 30 degrees Fahrenheit would produce as much as 31 ounces, or over 2 pints of free water. At a recent IATA Fuel Forum an airline reported that a wide body aircraft loaded with approximately 53,000 gallons of jet fuel that departs from an airport in a hot humid climate on a long haul flight can create as much as 5 gallons of water in the fuel tanks. The warm humid fuel is exposed to extremely cold temperatures present at high cruise altitudes and the water precipitates from the fuel. They could sump the tanks upon arrival, if the water was not a solid chuck of ice, and begin to question the quality of the fuel loaded when the facts are the fuel was of a perfectly acceptable quality when it was loaded onto the plane before departure.

However, as a line service technician, you cannot just assume the appearance of free water is caused by extreme temperature changes. You must conduct a thorough investigation to ensure that you are not facing gross water contamination from another source. If you find free water in a tanker truck sample I would tell you to call your fuel supplier. Ask them to walk you through the investigation protocol to ensure only clean, dry fuel is received into storage per industry standards.

My thanks to Steve Anderson, Global Fuels Quality Manager at Air BP for his help in editing this article. In the next blog Steve will write “Part 2” of water in fuel and share some great pictures.

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