Testing on a viable unleaded replacement for leaded aviation gasoline is set to resume this fall under the FAA/industry Piston Aviation Fuels Initiative (PAFI), but only one of the original Phase II two participants, Shell, is moving forward in that effort, according to the Aircraft Owners and Pilots Association. Swift Fuels, the second participant, late last week announced it is suspending its Phase II PAFI activities and instead focusing on a high-octane unleaded avgas replacement that is not part of the PAFI program.
Citing a need to evaluate “impacts and mitigations” of the differences between the PAFI fuels and 100LL, the FAA last spring suspended flight-testing and certain engine trials of the Swift and Shell drop-in unleaded fuel options under evaluation through PAFI program. At the same time, the agency extended the target completion date of the program by one year to the end of 2019. The flight-test program was about one-third complete and the engine test program was about halfway through the trials when the testing halted, the agency estimated.
The decision to move forward with testing of the Shell fuel was discussed at a PAFI Steering Group quarterly meeting held last week at AOPA’s Frederick, Maryland headquarters.
During that meeting, the FAA confirmed that Shell continues to work on mitigations of the issues, AOPA reported. David Oord, AOPA senior director of regulatory affairs, added that the recent Shell work has shown promise. “Significantly, testing to date has revealed important knowledge about the effects of different fuel formulations on engine durability and hot-weather operations,” the association reported.
Once testing is complete, PAFI will turn its attention to a plan to transition away from leaded avgas to an unleaded fuel.
As PAFI continues, so too are independent efforts to develop leaded avgas replacements. Swift said it is working privately with the FAA and manufacturers on an alternative pathway to certification and that engine and flight testing of its new higher-octane unleaded fuel has been ongoing. “[Swift] wants to maintain the momentum that we’ve started,” said CEO Chris D’Acosta, adding its unleaded fuels are “premium quality, reliable, intermixable for transition, and low toxicity—with no plug fouling or oil contamination—resulting in longer engine life and lower operating costs.” Swift currently produces UL94 unleaded avgas that it is in use by lower-octane aircraft.
While efforts such as Swift and PAFI are running concurrently, the focus of PAFI will be to develop a fleetwide authorized fuel, Oord said, adding that STCs will be necessary for makes and models using fuels outside of the PAFI effort.
