SEAL Aviation

WHAT IS DEF FUEL CONTAMINATION?

DEF is a urea-based chemical that is not approved for use in jet fuel. When mixed with jet fuel,
DEF will react with certain jet fuel chemical components to form crystalline deposits in the fuel
system. These deposits will flow through the aircraft fuel system and may accumulate on filters,
fuel metering components, other fuel system components, or engine fuel nozzles. The deposits may
also settle in the fuel tanks or other areas of the aircraft fuel system where they may potentially
become dislodged over time and accumulate downstream in the fuel system as described above.