What are common signs of water contamination in aircraft fuel?

• A. Clear amber color with no sediment
• B. Fuel smells like gasoline
• C. Milky or cloudy appearance, sediment, or water at the drain or filter; abnormal fuel gauge hints
• D. Strong diesel-like odor

Answer: (C)

Water in aircraft fuel often shows up visually and through the fuel system. A milky or cloudy appearance indicates an emulsion or suspension of water in the fuel, and sediment can be present from water settling out or from contaminants carried with the water. Water is heavier than fuel, so it tends to collect at the bottom of tanks or at the fuel drain and in filters, making water at the drain or in the filter a direct, clear sign of contamination. Abnormal fuel gauge readings can also occur when water is present, since the gauge or system behavior may be affected by the water, signaling an issue that needs attention before flight.

Clean, clear amber fuel without sediment suggests no water contamination. If the fuel smells like gasoline or has a strong diesel-like odor, that points to different contamination or issues beyond water in the fuel, not the typical signs of water contamination.