What hazard does water in fuel pose to aircraft systems?

• A. Steam formation
• B. Ice formation
• C. Humidity increase
• D. Color change

Answer: (B)

Water in fuel can freeze at typical operating temperatures, forming ice crystals that can clog fuel lines, filters, and metering devices. When these ice chunks block passages, fuel flow is restricted or shut off, leading to fuel starvation and potential engine power loss or flameout. This freezing risk is especially a concern in cold weather or at high altitudes where temps are low and water separation is less effective.

Steam formation would require temperatures well above what fuel experiences in flight, so it isn’t the issue here. Humidity increase isn’t a direct, discrete hazard to the fuel system once water has already mixed with the fuel. Color change isn’t a reliable indicator of the blockage or icing risk and doesn’t reflect the functional threat to fuel flow.