Diesel Exhaust Fluid (DEF) is a colorless additive used with diesel engines to reduce emissions. It has mistakenly been added to jet fuel on three occasions over the past 18 months. Presumably, operators have mistaken DEF for fuel system icing inhibitors (FSII), which are also colorless. The latest DEF contamination incident caused engine flameouts at altitude in two Cessna 550 jets, one of which experienced dual-engine flameout resulting in a total engine failure landing at a Savannah, GA airport.
Talk with your fuel providers and ask if they use DEF in ground equipment. If so, inquire about procedures to confirm correct additives are used for jet fuel. This should include separate storage, clear labeling, confirmation of correct additives at the time of insertion, and training for personnel.
DEF crystallizes in jet fuel and clogs fuel filters, which can result in fuel starvation. If engine failure occurs due to turbine flameout, be cognizant of the potential for DEF contamination. Follow emergency checklist procedures for engine failure and realize if DEF contamination is the cause, successful restart is unlikely.
If a turbine engine flameout occurs in a multi engine aircraft, follow emergency checklist procedures and expect loss of the remaining engine(s). Consider preserving altitude for as long as possible to maximize potential of a safe glide to a suitable runway.
If you encounter or suspect any DEF contamination, notify the Fixed Base Operator where fuel was obtained as soon as possible. Document the incident and report it to the local FAA FSDO office immediately.
There are no known pre-flight procedures pilots can use to identify the presence of DEF in jet fuel.
An industry working group, which includes AOPA is working to understand causes of contamination and provide recommendations for prevention.
To increase safety awareness and help reduce accidents, the AOPA Air Safety Institute periodically issues Safety Notices to remind pilots of significant safety topics.