How Does Water Get Into Aircraft Fuel Tanks?

Water in fuel tanks

If any of you figure out a way to make water burn, please call us. We'd be happy to help you make use of this knowledge. Until then, I think we can all agree that it is not a good idea to put it into aircraft fuel tanks.

Many people just do not understand how water can get into an aircraft and therefore do not understand what they can do to prevent such contamination. Some do not realize how often it happens, and that it can happen to them. We are not talking about a drop or two, we are talking about gallons or even hundreds of gallons.

In our industry we have procedures for checking certain things, but many people do not know why they are performing these checks or what can happen if they do not. Unfortunately, a lack of understanding often leads to complacency, and this can lead to disaster.

In case you are not getting the point, EVERY YEAR LIVES ARE PUT AT RISK BECAUSE REFUELING COMPANIES LIKE YOURS DON'T THINK IT CAN HAPPEN TO THEM! In every case, after the event the operator is shocked and disbelieving. The common comment is, "I thought it couldn't happen here; we have a good QC program, do all the tests and use a good fuel supplier." The same thing CAN happen to you, no matter how good you think your quality control is.

Water, water everywhere

The following are examples of how water has gotten to aircraft. Surely there are other additional ways for this to happen; this is not a complete list of every possible cause.

1. On top of virtually all truck tanks, there is what we call "roll-over protection." This amounts to a dike or dam around the vents and manways. The idea is to prevent damage to these items if the truck rolls over upside down. To drain rain water (or melting snow) from this area, hoses are run down from the corners of the enclosure. Unfortunately, inspection of these drain hoses is often ignored as "no big deal," and they plug with debris (or even ice).

Well it is a very big deal. This has caused many incidents where gross amounts of water (up to 250 gallons) were put into aircraft. I personally spoke to a man who drained 150 gallons of water from an airliner. How did it get into the tank? If the water can't drain off, it "pools" up to 8 inch (or even more) deep. If the manway or vent seals fail, it goes directly into the storage tank. Even if the seals do not leak, when you engage the PTO to pump, the vent (which is submerged in water) opens allowing the water to enter the tank.

Check the drain hoses and manway gaskets and the filter separator water controls as well as checking tank and vessel sumps.

2. The snow had accumulated at an airport, and due to warm days and cool nights, the snow melted during the days and refroze at night. This allowed several inches of water to cover the area where the underground tank was buried. The gauging hatch or the test cable port gasket for the floating suction leaked. Water went directly into the storage tank. The filter separator water controls at the fuel farm and refueler truck both failed. An aircraft crashed.

This has also happened in warm climates during strong rains or floods. In one case, all of the fuel floated out of the tank and the tank was completely filled with water.

Check your tank top connections for a tight fit and proper gaskets; sump your tanks and vessels. Make sure the sample is fuel and not pure water. Check water controls periodically, tank sumps and vessel sumps daily.

3. The ground-water level was high and a structural problem caused a leak in the underground storage tank. Fuel did not leak out, water leaked in. The pilot or engineer of an aircraft being fueled later happened to notice that a fuel tank level indicator suddenly went from almost empty to full in the blink of an eye. If he had not noticed this, caused by an electronic gauge not calibrated for the high conductivity and mass of water, a catastrophe would certainly have occurred Still, more than 300 gallons of water was drained from the aircraft.

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