What is the fuel settling time?

• A. 2 hours
• B. 6 hours
• C. 4 hours
• D. 8 hours

Answer: (C)

Fuel settling time is the period allowed for fuel to stand undisturbed so water and particulates can separate from the fuel by gravity. In UH-60S fuel procedures, you let the fuel settle to ensure any water in the tanks coalesces and sinks to the bottom, so you can accurately drain water from the sump or take a representative fuel sample. Water is denser than the fuel, so with regular ambient conditions four hours gives enough time for droplets to separate and for sediment to settle, yielding a clear layer for testing or draining. Longer or shorter times can lead to improper readings or unnecessary downtime, so four hours is used as the standard settling period.