What is the purpose of a water separator in aviation fuel systems?

• A. To remove free water from fuel before it reaches the engine.
• B. To filter particulates from fuel after the engine.
• C. To measure fuel temperature before injection.
• D. To blend additives into fuel.

Answer: (A)

The main idea is to remove free water before it can reach the engine. Free water in aviation fuel can come from condensation or handling and, if it gets into the fuel system, can freeze in cold conditions, clog fuel nozzles, damage pumps, promote corrosion, and encourage microbial growth. A water separator takes advantage of the density difference between water and fuel, causing water droplets to coalesce and settle out into a drainable bowl. The accumulated water is purged through a drain, keeping the fuel that reaches the engine dry. This function is distinct from measuring fuel temperature, blending additives, or filtering particulates after the engine.