Photo courtesy of Byerly Aviation In October 2023 Embraer announced it had successfully flown a Praetor 600 on 100 percent sustainable aviation fuel. This was the first test of a Honeywell engine on full SAF, and marks a turning point in the future of a transition to SAF-based fuels. Operating in the transition period can be confusing, so it helps to go back to Honeywell’s guidance to know what fuels are approved.
Fuels
In 2012 Honeywell issued a Service Information Letter (D201208000096), which details the full range of approved fuels and additives for TPE331-1 through -12 series engines. Obviously, Jet A and Jet A-1 are approved, but so are French kerosene, military JP-8 and JP-4, and a number of other Chinese and smaller-batch fuels.
Surprisingly, even 100LL is approved for emergency use. The bulletin restricts it to 250 gallons (946 liters) per 100 hours of operation. Total usage must be limited to 7,000 gallons (26,498 liters) during any 3,000 hour period.
Anti-ice
Many operators recommend or require anti-ice fuel additives to prevent the formation of icing in the fuel lines and nozzles under extreme temperatures. Jet A has a freezing point of minus 40 degrees C, and Jet A-1 freezes at minus 47 degrees C. Even so, anti-ice additives can be nice insurance. According to the Honeywell bulletin, EGME and DiEGME are automatically added to military fuels such as JP-4, JP-5, and JP-8. But for civilian fuels, Prist remains optional at a concentration of up to .15 percent by volume. If you do opt for Prist, Honeywell recommends sumping the tanks daily for water.
Fungicide
Adding a fungicide or pesticide to fuel can help with long-term nozzle health. But Honeywell cautions that its use must be carefully monitored to avoid hot section or fuel system damage. The manufacturer says continuous use isn’t approved, but that an occasional kill treatment is allowed. In this case, 270 ppmw, or one gallon of Biobor JF per 5,000 gallons of fuel. For smaller quantities, that’s equivalent to one ounce per 40 gallons of fuel.
Although Biobor says that a lower concentration can be used on a continuous basis for the prevention of biomass, Honeywell says that isn’t approved. They offer that Prist, used continuously, has been shown to retard microbiological growth. If an operator decides to undergo a treatment of Biobor JF, Honeywell recommends:
- Follow the manufacturer’s recommendations on mixing. Failure to properly mix biocides can result in engine fuel – system and/or hot-section – damage.
- Monitor fuel low pressure warning signals and/or fuel pressure differential signals. Fuel filter life may have to be reestablished by the operator.
- Intermittent use is defined as a single application to sterilize jet fuel suspected or found to be contaminated with microbiological debris.
- The treated fuel may be burned off in the engine provided the concentrations listed are not exceeded and the fuel is not visually contaminated with microbiological debris. Heavily contaminated fuel may need to be downgraded or discarded.
