The National Transportation Safety Board (NTSB) has warned of the dangers of contamination of jet fuel with diesel exhaust fluid (DEF).
The board has issued a new safety alert and accompanying poster, following several incidents where aircraft experienced severe difficulties and even engine failure due to such cross-contamination.
“DEF is not designed, nor approved, for use in jet fuel,” said the Safety Board. “If it is inadvertently added to jet fuel, as has happened in several incidents over the last two years, DEF will react with certain chemical components to form crystalline deposits in the fuel system. The crystalline deposits can then accumulate on filters, engine fuel nozzles, and fuel metering components and result in a loss of engine power.”
DEF can be mistaken for other liquids if not properly labelled, such as fuel system icing inhibitors (FSII). This has become more of an issues since the fluid became more widespread as the fuel for on- and off-road diesel-powered vehicles.
“The NTSB wants fuel providers to ensure they store all chemicals in labeled containers and that they add a ‘NOT FOR AVIATION USE’ label to all DEF containers,” the safety agency said.
A recent incident caused to Cessna Citation 550s to lose engine power in May, although the crews were able to divert and land safely. It was later discovered a lineman had combined containers of FSII and the DEF, as they both looked similar.
“Analysis of fuel samples, fuel system filters, and fuel screens from the airplane indicated the presence of urea, the primary chemical found in DEF,” NTSB said.
Similar incidents occurred in Omaha, Nebraska in November 2017 and in Miami in August 2018, causing severe difficulties, although the crew were able to land in both cases.