Last December, Shell Aviation revealed that it was the first major oil company to develop a lead-free replacement for 100LL.
The lead-free formulation is the result of 10 years of “exhaustive R&D,” according to company officials.
While some worry that large companies will forsake GA as it is such as small segment of the fuels market, Shell officials say that’s not true for them.
“General aviation is an important segment for Shell Aviation,” said Rob Midgley, Shell Aviation’s Global Technical & Quality Manager Aviation Fuels. “We recognize that it is a critical resource for remote communities and an enabler of a number of important activities, such as flight instruction, business travel, agricultural applications and emergency medical services. It is also one of the key building blocks of our industry, as almost all pilots begin their journey in a general aviation aircraft cockpit.”
Midgley noted that the company has a “strong and proud history of firsts in piston aviation, including fueling the first trans-Atlantic flight in 1919, being the first to commercialize 100 Octane fuel in the 1930s, being the first to produce a semi-synthetic multi-grade piston engine oil, and the first to produce dedicated lubricants for both aviation diesel engines and light sport engines.”
He noted that the company’s aim is to “continue leveraging Shell’s extensive technological expertise to support this industry.”
He added that while the company’s new fuel undergoes testing by the FAA, it continues to work with ASTM, OEMs, the industry and consumers “to develop the body of data necessary to achieve this fleet-wide certification as soon as possible.”
Over the past decade, Shell conducted a range of screening tests on more than 3,000 formulations, according to Midgley.
“We also developed a modular engine test stand to aid understanding of both engine and fuel performance and testing in this engine and this, along with full ASTM D910 property testing, has helped narrow this formulation space,” he explained. “This has led to some formulations progressing to full-scale engine testing and flight testing.”
Working alliances were formed to evaluate the new fuel in laboratory engine bench tests by Lycoming Engines and in a flight test by Piper Aircraft.
Shell’s experience over the last 10 years highlights the complexity of approving a new unleaded fuel for general aviation.
“Achieving 100 Motor Octane without the presence of lead is far from trivial,” he said. “This octane rating is substantially higher than that used in the automotive market, perhaps 10 octane points higher than the very best road fuels.”
“Simply achieving octane rating without lead is, in itself, very challenging, however, octane is not the only safety parameter in the fuel specification,” he continued. “There are many other properties and limitations in the specification that have been adopted as a result of our historic experience and so these are also important parameters when considering how to maintain flight safety.”
On top of all that, he noted, is the need to “balance this with the need to use components that are available worldwide at a reasonable cost.”
He noted that it is no accident that the composition of leaded avgas has not changed in decades.
“Despite the challenges for needing dedicated production and distribution facilities to handle leaded fuels, the use of lead has been the most efficient way to meet all of the demands of this fuel,” he said. “Removing lead with as little impact on performance, flight safety and cost is a more complex challenge than many might realize.”
Midgley added that it is too early to tell whether the fuel will be a drop-in replacement for 100LL.
“Further testing will help determine this, but it is certainly Shell’s intent,” he said. “The intent is that the transition would be made such that any unleaded fuel would be introduced to the supply chain in a way that would allow mixing with current 100LL. There is work ongoing with various mixtures of Shell’s unleaded fuel with leaded fuel to determine the performance of these fuel mixtures.”
One perceived cost savings with an unleaded fuel is that it will be able to be distributed through regular supply lines — 100LL, as the only leaded fuel, must be transported separately, which increases costs.
But Midgley cautions that pilots and aircraft owners must remember that the retail price of fuel is dependent on a number of factors and a number of entities, from component manufacturing sources, blending, trading, supply and, ultimately, the airport FBO.
“We are hopeful that some synergies with the movement to unleaded fuels would reduce the cost to supply, however, Shell is not in control of the whole value chain,” he said. “For that reason, it is not possible to give a statement on how this cost saving will be reflected in an end-user price. What does affect the end user price more frequently in the energy market is price elasticity and supply and demand balance, so our objective is to manage the end-user price by working to ensure adequate supply capability and also capitalize on all opportunities to minimize supply side costs.”