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Speak with an Aviation Gasoline Specialist
Speak with an Aviation Gasoline Specialist
The history of aviation fuel is closely tied to the early days of flight. Originally, aircraft utilized the same fuel as motor gasoline (mogas). As aircraft engines developed, planes needed more specialized fuel to generate enough power for engines while not combusting too quickly at higher altitudes. Therefore, the race to create avgas 100LL started in the late 1930s.
The development of higher-performance aircraft engines created the need for higher octane avgas. One primary struggle of early avgas was the extremely high production cost, such as charging $20 per gallon of avgas compared to $0.20 per gallon of mogas. In 1936, French engineer Eugene J. Houdry produced much cheaper production methods by helping to create two refining processes capable of producing higher octane number components: catalytic cracking and alkylation. High-octane fuels were developed to prevent knocking (pre-ignition), which can severely damage engines. These fuels allowed engines to run at higher compression ratios and power outputs.
One of the significant breakthroughs in aviation fuel came with the introduction of tetraethyl lead (TEL) in the 1920s. For fuels, the primary challenge was to improve antiknock properties so that the engines’ power output would not be knock-limited. The major developments were the use of lead antiknock additive (tetraethyl lead), the identification of petroleum crudes with the best lead response, and the identification and production of specific hydrocarbons with good antiknock properties.TEL was added to gasoline to increase its octane rating, thus preventing knocking. However, the health and environmental impacts of lead were not fully understood at the time.
Because the need for high-performance avgas became a critical part for the Allied countries during World War II, both catalytically cracked gasoline and alkylate were used extensively in avgas during production. Military aircraft required fuel that could support the demands of high-altitude and high-speed flight. This led to the development of 100-octane fuel, which became the standard for military aviation. The performance benefits of 100 octane fuel were so significant that it gave Allied aircraft a distinct advantage in aerial combat. Air power was critical to the outcome of World War II, and toward its end, the Allies’ production of avgas peaked at more than 25 million gallons per day.
Two years after the war, demand for avgas decreased sharply to about 5 million gallons per day. The growth of commercial aviation together with military use resulted in a gradual increase to about 14 million gallons per day in 1957. Then production began to decrease again as turbine engines replaced piston engines, first in the military and later in commercial applications, returning to about 5 million gallons per day in 1970.
Beginning in the 1970s, the EPA tried to ban lead in products such as paint and motor oil. Lead is a toxic substance that poses significant risks to both human health and the environment. In response to growing concerns, efforts were made to reduce the lead content in gasoline. For the aviation industry, this led to the development of 100LL (low lead) aviation fuel.
100LL was introduced in the 1970s as a replacement for the higher leaded avgas. 100LL had a lower lead amount than traditional Avgas 100 but still enough to effectively produce more power and antiknock properties for piston engines. The blue-colored 100LL fuel became the new standard for general aviation, balancing performance needs with a reduced environmental impact. However, controversy over avgas 100LL still exists due to the edition of lead in the fuel.
Despite the reduction in lead content, 100LL still contains lead, which remains a concern. The aviation industry has been actively seeking alternatives to leaded avgas for many years. Various unleaded aviation fuels have been developed and tested, but finding a suitable replacement that meets the performance requirements of 100LL has proven challenging.
An unleaded fuel that would satisfy the most critical piston engines in the existing aircraft fleet would need the same anti-knock performance as Grade 100LL. The Coordinating Research Council is testing potential blend components for such fuel. However, the challenge is daunting because the antiknock properties of tetraethyl lead are truly unique.
One of the significant efforts in this regard is the Piston Aviation Fuels Initiative (PAFI), a collaborative effort between the FAA, industry stakeholders, and environmental organizations. PAFI aims to develop and certify unleaded aviation fuels that can serve as direct replacements for 100LL, ensuring the safety and performance of piston-engine aircraft while eliminating lead emissions.
The history of 100LL aviation fuel is a testament to the continuous evolution and innovation in the aviation industry. From the early days of flight to the present, aviation fuel has undergone significant changes to meet the demands of advancing technology and growing environmental awareness. 100LL has been a critical component in this journey, providing the necessary performance for piston-engine aircraft while addressing some of the environmental concerns associated with leaded gasoline.
Although turbine engines become more and more popular, demanding more use of jet fuel as opposed to avgas 100LL, the legacy of 100LL will be remembered as a pivotal chapter in the history of aviation fuel. The efforts to develop safe, efficient, and environmentally friendly fuels will ensure that aviation continues to thrive while minimizing its impact on the planet.
