Fuel Checks

Detecting Water Contamination

Detecting water in Jet A-1 can be difficult, because Jet A-1 isn’t tinted. If the sample has a cloudy appearance, there could be a lot of water suspended in the fuel.

Make sure your drain vessel is clean before taking a sample. Hold it to the light and against a white background, and look at it side-on, rather than from above. You should be able to detect any debris, and you can also see if the contents are tinted.


Then smell it. But again, be cautious. Water can carry a fuel odour if the two have been in contact. Also be aware that plastic fuel testers can retain the odour of fuel.

If the sample does test positive for water or other contaminants, empty the tester and continue draining until a clean sample
is obtained. Be sure to empty the sample into a fuel disposal container. Don’t dispose of the sample fuel on the tarmac because it can degrade bitumen, and don’t dispose of it on grass, because it can ‘burn’ it killing it off.

Don’t tip the sample back into the aircraft tank, even if it is ‘clean’.

After you finish sampling, ensure that each drain valve closes securely, to avoid inadvertent fuel loss.

If you’re using a portable fuel source, such as a jerrycan, check a sample from that source before fuelling the aircraft. Truck mounted tanks also need to be checked regularly for water or other contaminants.

When sampling with reduced natural light, check the sample under bright lighting
and against a white background, such as a fuselage. That will make it easier to detect the colour and any debris or contaminants.

Water often collects in wrinkles and low points within fuel bladders. If the aircraft is not on a level surface and water/other contamination is suspected, move the aircraft to a level surface, and allow the fuel to settle. Then carry out water/other contamination checks. Keep checking until a clean sample is obtained.

In cold winter conditions, small amounts of water can freeze the drain plug, rendering it inoperative. It will need to be warmed to drain any water, for example, by moving your aircraft into the hangar.

Consult an aircraft engineer if there is an unusually large amount of water in the fuel.

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