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Photo from AOPAFuel is a crucial component in aviation and without proper fueling or the right amount of fuel, the results could be catastrophic. Fuel System Icing Inhibitor (FSII) contamination with Diesel Exhaust Fluid (DEF) has led to at least four incidents in recent years, causing partial and complete engine failures, nine emergency landings and at least one instance of a dead-stick landing. With proper training and procedures, this type of contamination is entirely preventable. The National Air Transportation Association is pushing for members and refueling operators to implement an operational best practice to prevent possible tragedies.RELATED STORY:Preventing faulty fueling- the best practices for proper fuel planning
NATA brought to light a series of incidents in recent years, all due to FSII and DEF contamination. After an incident in 2017, NATA reviewed the risk of jet fuel contamination with DEF and formed a free DEF Contamination Prevention training course. In November 2017 seven aircraft were serviced with contaminated fuel and another six were serviced using the same refueling equipment exposed to DEF.NTSB Safety Alert
AOPA reported that a similar incident occurred in 2018, when five planes were given contaminated fuel from Aug. 12-16. Of those five, a Dassault Falcon 900EX made a forced return to the airport after two of its three engines had been disabled. Nine other aircraft were fueled with equipment that had been exposed to DEF. The FAA issued a special airworthiness bulletin in response, giving three recommendations of best practices to prevent contamination and report it.
In May 2019, two Cessna Citation II twinjets fueled at Punta Gorda Airport were given contaminated fuel. The two jets experienced engine failure and landed safely. The two jets flew as air ambulances, one experienced flameout in Georgia and landed in Savannah, the other experienced engine failure and landed in Louisville, Kentucky. While all the aircraft have landed safely and without a serious crash, contaminated fuel runs the risk of resulting in problems like engine failure or flameout, which could result in a deadly accident. DEF crystallization in an aircraft fuel tank (left) and DEF crystallization on an aircraft fuel filter (right)
DEF is a colorless additive used in diesel engines to reduce emissions. When mistakenly added to jet fuel, it can cause issues that could result in a deadly crash. The belief is that this colorless additive is mistaken for FSII, which is also colorless. DEF is not a fuel additive but rather a clear liquid containing urea and demineralized water used to reduce emissions in some diesel engine vehicles. This liquid is designed to be used in 2010- or later vehicles with Selective Catalytic Reduction systems. DEF can react to certain chemicals in jet fuel, forming crystalline deposits in the aircraft fuel system.
Most of the incidents have been found or are believed to be due to a mistake, like when DEF is used in place of a different clear substance. NATA issued a Safety 1st Alert over the critical issue of DEF contamination. Another recent event occurred in the southwestern U.S. and the impacted aircraft lost both engines before making a dead-stick landing nearly 280 miles away. This marks five major incidents since 2017.
NATA outlines the best practices to avoid and deal with contamination, urging any FBO or fuel provider to take important steps to prevent fuel contamination and complete training on what to do if fuel has been contaminated. Any fuel believed to be contaminated should be discarded and the mobile refueler should be quarantined. NATA recommends that all FBOs and aviation fuel providers work with their fuel providers to develop a response protocol to contaminated fuel incidents. This should be an important step in training for FBO staff.
FBOs are urged to follow NATAs Safety 1st Operational Best Practice Preventing Contamination of FSII with DEF or any Other Product and the Energy Institute's EI 1538 Handling of fuel system icing inhibitor and aviation fuel containing fuel system icing inhibitor at airports. Companies using the best practices can also implement training on preventing fuel contamination. DEF in FSII test kits are available and serve as another cautionary option to prevent disaster.
DEF contamination is a concern for many members of the industry, with organizations like NATA, the FAA, the NBAA and the AOPA making public statements to draw attention and raise awareness. If you are refueling your plane or watching someone else refuel it, keep contamination in mind and ensure your plane is running on clean, uncontaminated fuel.