The Daily Parker

Politics, Weather, Photography, and the Dog

Yes, AVGAS still has lead in it

MSNBC is scandalized that 100-octane low-lead aviation fuel (AVGAS) still exists, but as usual for general stories about technical topics, they miss a few important details:

While leaded gasoline was fully phased out in 1996 with the passage of the Clean Air Act, it still fuels a fleet of 170,000 piston-engine airplanes and helicopters. Leaded aviation fuel, or avgas, now makes up “the largest remaining aggregate source of lead emissions to air in the U.S.,” according to the Environmental Protection Agency.

For now, leaded aviation gas appears to be caught in a bureaucratic limbo: stuck between not meeting the environmental demands of the EPA and the commercial realities of the aviation community. It is the primary viable option for this type of aircraft, as the general aviation community argues it remains critical given the needs of the current fleet.

“Fuel and emissions are governed by the federal government,” said Eric Peterson, county airports director with the County of Santa Clara, which owns Reid-Hillview. “So until they come up with an alternative fuel, there is a limited amount the county can do to address that.”

But why, oh why, do piston airplanes still use leaded gas? MSNBC doesn't spend a lot of their article explaining that it's so the airplane engines don't just stop suddenly during flight. Lead reduces "knock," which can annoy you if it happens to your car's engine, but which can kill you if it happens to your plane's.

Also, lead boosts octane, and for high-performance aviation piston engines, nothing less than 100 octane will work.

Alternatives are coming, soon, but it will take some time. The FAA explains what needs to happen before they can approve 100-octane unleaded fuel:

The FAA requires the fuel producers to complete the following "pre-screening" tests prior to a candidate fuel formulation entering into more extensive testing through the PAFI (Piston Aviation Fuels Initiative) program:

  1. Successful completion of a 150 hr. engine endurance test on a turbocharged engine using PAFI test protocols or other procedure coordinated with the FAA;
  2. Successful completion of an engine detonation screening test using the PAFI test protocols or other procedures coordinated with the FAA
  3. Successful completion of a subset of the material compatibility tests using the PAFI test protocol or other procedures coordinated with the FAA.

Development and pre-screening testing is taking place at both private and public testing facilities across the country. The FAA's William J. Hughes Technical Center is providing engine-testing services through Cooperative Research and Development Agreements (CRADA) with the individual fuel companies. While COVID-19 has delayed the completion of the pre-screening tests, the tentative schedule is to re-start formal PAFI testing in 2021.

So, yes, I and every other private pilot out there wants to use unleaded fuel—or, really, a completely different power source. But as long as the consequences of sudden power loss remain different for aircraft than for any other type of vehicle, we have to keep using the only safe (for the airplane, anyway) fuel that remains widely available.

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