Diamond Aircraft officials reacted with surprise to ExxonMobil’s statement that it “does not support or endorse the supply of jet fuel [for] aircraft powered by diesel engines.” The Diamond DA42 Twin Star is powered by Thielert diesel engines.
A letter from Diamond to its customers said they are unaware of the reason for ExxonMobile’s position, and equally unaware of any jet-fuel related service difficulties in any Thielert-powered Diamond airplane.
“While the technical arguments given by ExxonMobil Aviation are valid general concerns for operation of diesel engine powered aircraft, in the case of TAE and Diamond, all listed reasons, specifically ignition quality, freezing point and lubricity, have been addressed as part of the engine and aircraft certification process and approved by the responsible airworthiness authorities,” the Diamond letter stated.
“For North American customers specifically, the DA42 is certified by the FAA for operation with Jet A and Jet A-1 (ASTM 1655) exclusively, vs allowing operation with diesel fuels,” the letter adds.
AOPA Government Affairs representatives will be in Tampa in mid-December to attend an industry meeting on diesel fuel standards. Establishing industry-agreed-upon testing standards for diesel fuel may address ExxonMobile’s concerns in the future, but AOPA officials caution that establishment of standards is, in general, a lengthy process.
Diamond Aircraft plans to discuss the issue further with ExxonMobile.