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Two Cessna 172s sitting on the ramp awaiting a fuel truck. Photography courtesy of Nicole Lund.
California and Colorado are two states leading the country in proposals on banning leaded aviation fuels. Colorado has proposed a bill to tax users of leaded fuel in an attempt to counter the damage of leaded fuel on local communities and to phase out the sale of leaded fuel by 2026. Airlines and other jet operators do not contribute to the leaded fuel use. Jet aircraft use jet fuel, which is a form of kerosene and does not contain lead. Smaller, piston aircraft still heavily use leaded fuel for operation. Leaded fuel has been phased out for automobile use; however, aviation still widely depends on leaded fuel. Here are three reasons why.
Dependability
The most common leaded fuel found in aviation is 100LL. The lead added to the fuel helps it achieve a higher octane level. High-octane fuel is preferred for general aviation because it is more stable and prevents detonation in the aircraft's cylinders. Over time, detonation can take a toll on aircraft engines and cause undue wear and tear. This could adversely affect the safety of the occupants if a mechanical incident were to occur.
Difficulty in permitting other fuel use
Most general aviation aircraft need a supplemental type certificate (STC) to operate on unleaded fuel. A STC is a certificate granted by the Federal Aviation Administration (FAA) for any modifications to an aircraft. Since most general aviation aircraft were not permitted to use fuel besides 100LL at the time of manufacturing, the STC is required to legally operate an aircraft on unleaded fuel. These certificates can be pricey. A STC for unleaded fuel can cost $500-1,000. In addition, there are very few fuels approved for use with the STCs and they are hard to come by.
Widely available
100LL can be found at most airports across the country. Most airports do not carry unleaded aviation fuel. The select few airports that do have unleaded fuel, the supply is low compared to the large storage and supply of 100LL.
Most airports have large storage tanks for jet fuel and 100LL. Few airports have the storage capacity for additional fuel. Photography courtesy of Nicole Lund.
The General Aviation Modifications, Inc (GAMI) is leading the industry in a high octane, unleaded, fuel option that is safe on aircraft. Availability is the biggest struggle for GAMI. There is not a large enough demand from aircraft operators and airports to have widespread availability of the fuel. Airports rely on the demand of fuel for profits. If pilots do not have STCs for unleaded fuel, they can't make the change from 100LL. For pilots to pay for the STC and regularly fuel with unleaded fuel, it needs to make financial sense. The unleaded fuel needs to cost roughly the same if not less than 100LL for pilots to justify the change as well as the investment in the STC.