How long after a move should you wait to take fuel samples?

The correct choice of waiting 2 hours after a move to take fuel samples is based on the principle of allowing any disturbance caused by the movement to settle. When an aircraft is moved, it can stir up sediment and contaminants that may have settled at the bottom of the fuel tank. Waiting for 2 hours ensures that these particulates have had sufficient time to settle back down to the bottom of the tank, thus providing a more accurate assessment of the fuel quality when samples are drawn.

This timeframe helps minimize the likelihood of collecting a sample that may contain particulates that were stirred up during the move, which could lead to a false interpretation of fuel contamination. Other timeframes, such as 30 minutes or 1 hour, may not allow for enough settling time, potentially compromising the integrity of the fuel sample. The 4-hour wait, while perhaps seeming cautious, is excessively long and could delay operational processes without significantly improving the accuracy of the sample results.