After over a decade of research and development (and governmental foot-dragging), small piston-engine airplanes finally have an unleaded gas to use. General Aviation Modifications Inc. (GAMI) has developed an unleaded 100-octane AV gas that was finally approved for general use in piston airplanes by the FAA on Thursday.
Despite leaded fuel having been banned in the U.S. for more than two decades in automobiles, every small piston-engined aircraft has continued to use solely leaded AV gas. This is despite the well-documented and serious health effects leaded gas has, and though there are unleaded AV gas alternatives in development for years, none were given an official FAA supplemental type certification until Thursday. GAMI's unleaded fuel is the first in the U.S. that is approved for all spark ignition engines and airframes.
The main sticking points keeping small planes using leaded fuel have been twofold. One is basic physics: most piston aircraft cannot transition to unleaded gasoline without a specifically formulated alternative, as lead additives reduce knock and allow for more power to be made from small engines. Attempting to run an unmodified small airplane on unleaded fuel—by pulling timing to eliminate knock—would make the engines so underpowered most planes wouldn't be able to get off the ground. The second reason, however, has been regulatory: unleaded AV gas has been in development for over a decade, and the government has largely slowed efforts to mainstream it.
Indeed, GAMI's fuel has been in development for 13 years, with research starting around the same time that the EPA began looking into the health effects of leaded aviation gasoline on communities surrounding small airports. But the EPA has never released findings from that study (which would trigger mandatory regulatory change), and while the FAA started an initiative earlier this year to help develop unleaded AV gas alternatives, it's also sued local governments that attempted to eliminate leaded fuel from small airports in their cities. Additionally, GAMI's unleaded fuel passed all of the FAA regulations and testing requirements earlier this year and was awaiting final approval for months, with no clear reason for the delay. However, the approval of the unleaded gas at long last means the FAA's goal to transition the aviation industry entirely to unleaded AV gas by 2030 is vastly more doable.
It will still likely be a while until widespread adoption, however, as GAMI cofounder George Braly told the Aircraft Owners and Pilots Association that scaling from small batches to millions of gallons will take time due to supply chain constraints, and prices won't drop to leaded-fuel levels until production has scaled up. Despite this, there will likely be overall benefits that will entice aircraft owners to switch, even before GAMI's fuel prices reach parity with leaded gasoline, as Braly noted the unleaded fuel will allow for lower-maintenance operation, saying, “I think the days of cleaning spark plugs every 50 hours are going to be behind us for good.”