The Federal Aviation Administration has revealed broad strokes of a plan to eliminate leaded aviation petrol starting by end-2030, though it warns the transition could cause operational issues and says availability of replacement fuels could affect its strategy.
“There is potential for in-service challenges to arise due to the breadth of aircraft and engine designs, materials and operations,” the FAA says in its newly released 77-page “Draft Transitional Plan to Unleaded Aviation Gasoline”.
“The decisions made by private individuals and companies could have a significant influence on the ultimate transition,” the document adds. “The process of the transition will continue to evolve as 2030 approaches.”
The agency and industry partners have for years been working toward eliminating 100LL, a widely used 100-octane low-lead petrol containing tetraethyl lead, a liquid additive used to boost octane and prevent engine knocking and damage. But tetraethyl lead also causes air pollution and is suspected of posing health risks to humans, which is why aviation petrol is the only US transportation fuel still containing the substance.
Technical challenges make the aviation industry’s transition to unleaded gasoline tricky.
“Finding replacement unleaded fuel involves in-depth testing and evaluation of many fuel characteristics such as performance, detonation resistance, materials compatibility, durability, maintenance impacts and the potential need for related aircraft alterations,” the FAA’s plan says. “Critical market considerations such as fuel availability and quality control of the fuel make the task even more complex.”
The FAA’s task involves ensuring that aircraft currently approved to burn 100LL – there are some 175,000 of them flying in the USA – can safely burn an unleaded alternative.
The new roadmap lays out four stages for the transition, the first involving “fuel authorisations and comparisons”. The FAA notes three possible unleaded options are now in various stages of obtaining FAA authorisations.
The second stage – “gaining market experience” – will involve evaluating cost and learning from the experiences of operators who transitioned early to unleaded fuels.
“Cost is one of the main concerns expressed by aircraft owners, who would prefer that the transition to unleaded avgas does not increase their operating costs,” the FAA says.
The plan’s third phase calls for eliminating leaded aviation petrol in all US states (except Alaska) by end-2030. The fourth phase will see Alaska make the transition two years later.
