Aviation Fuel – Fuel for Aircraft: Comprehensive Glossary & Explainer

Aviation fuel is the lifeblood of powered flight, enabling everything from small training aircraft to intercontinental airliners to operate safely, efficiently, and reliably. Unlike automotive or marine fuels, aviation fuel is engineered and regulated to perform in the harshest conditions—freezing high-altitude temperatures, low pressures, and rapid changes in power demand. This glossary provides a comprehensive technical reference for aviation fuels, exploring their types, chemistry, properties, handling, safety, environmental impact, and future developments.

What is Aviation Fuel?

Aviation fuel refers to any combustible liquid formulated and certified specifically for use in aircraft propulsion systems. Its primary function is to deliver reliable, high-energy output to aircraft engines—whether piston, turboprop, or jet—across a vast range of environmental and operational conditions. Stringent standards such as ASTM D910 (for avgas) and ASTM D1655 (for jet fuel), along with ICAO Annex 6 and Annex 14, govern its formulation, testing, and distribution.

Aviation fuels must resist hazards like vapor lock, freezing, detonation, and microbial contamination at altitudes where temperatures can fall below -50°C and pressure drops dramatically. Strict controls on sulfur, aromatics, water, and particulates ensure clean combustion and engine longevity. The integrity of aviation fuel is vital for flight safety, and its supply chain is among the most tightly controlled in any industry.

Typical characteristics:

Major Types of Aviation Fuel

Aviation fuels are classified by engine compatibility, chemical composition, volatility, and regulatory approval. The main categories are avgas, jet fuel, mogas, sustainable aviation fuel (SAF), and emerging alternatives.

Avgas (Aviation Gasoline)

Avgas is a high-octane, leaded or unleaded gasoline used in spark-ignition piston aircraft engines. Governed by ASTM D910 and DEF STAN 91-90, avgas’s tight purity and volatility controls make it suitable for high-compression engines operating in extreme environments.

Avgas is dyed for easy identification and misfueling prevention—blue for 100LL, green for 100/130, and red for 80/87. The environmental drive to eliminate lead is accelerating the transition to unleaded grades such as G100UL and UL94.

Applications:

• Piston-engine training and private aircraft
• Agricultural and aerobatic aircraft
• Vintage and classic planes

Jet Fuel (Jet A, Jet A-1, Jet B)

Jet fuel is a kerosene-based blend for turbine-powered aircraft (jet, turboprop). Strict standards (ASTM D1655, DEF STAN 91-91) guarantee performance in high-altitude, long-haul operations.

Jet A-1 is the global civil standard; Jet A is used mainly in the US. Jet B, with a lower freezing point and higher volatility, serves in extreme cold (northern Canada, Alaska) and some military roles.

Military grades (JP-4, JP-5, JP-8) are based on these but include extra additives for anti-icing, corrosion inhibition, and stability.

Mogas (Motor Gasoline)

Mogas is conventional motor gasoline (per EN 228, ASTM D4814) sometimes approved for certified aircraft via Supplemental Type Certificate (STC). Only engines and systems explicitly approved can use it, as aviation requirements differ from automotive.

Mogas often contains ethanol, which is problematic for many aircraft (absorbs water, increases vapor lock, degrades seals). Only ethanol-free mogas is typically approved.

Applications:

• Light sport and experimental aircraft
• Ultralights
• Select certified piston engines

Sustainable Aviation Fuels (SAF) and Biofuels

SAF are derived from renewable feedstocks—used cooking oil, algae, waste biomass—offering up to 80% lower net CO₂ emissions. SAF are “drop-in” replacements, certified under ASTM D7566, and compatible with existing jet engines and infrastructure. They are typically blended up to 50% with Jet A/A-1.

Production pathways include:

• HEFA (Hydroprocessed Esters and Fatty Acids)
• FT-SPK (Fischer-Tropsch Synthetic Paraffinic Kerosene)
• SIP (Synthesized Iso-Paraffins)
• ATJ-SPK (Alcohol-to-Jet)

Major airlines now operate SAF-powered flights, and ICAO’s CORSIA scheme is driving wider adoption.

Other and Emerging Fuels

• Diesel-based aviation fuels for modern compression-ignition piston engines offer improved efficiency and use widely available Jet A/Jet A-1.
• Hydrogen and electric propulsion are in development, promising zero-emission flight but facing challenges in storage, infrastructure, and energy density.
• Biokerosene and hybrid blends are in early-stage testing.

Key Properties of Aviation Fuels

Aviation fuels are defined by exacting chemical and physical properties to guarantee safety and performance.

Octane and Cetane Rating

• Octane rating (avgas): Resistance to engine knock, measured as lean/rich (e.g., 100/130 for Avgas 100LL).
• Cetane rating (jet fuels): Ignition quality in compression (diesel/turbine) engines; jet fuel typically 40–50 cetane.

Energy Density

High energy density allows for greater range and payload:

Jet fuels’ higher density favors large commercial and military aircraft.

Volatility

Volatility affects starting, vapor lock risk, and evaporation:

• Avgas: High volatility for cold starts, but vapor lock risk in heat/altitude.
• Jet fuel: Lower volatility for safety and high-altitude performance.

Flash Point

Minimum temperature for vapor ignition; a key safety metric.

Jet fuels’ higher flash point increases fire safety during storage/transfer.

Freezing Point

Temperature where fuel components solidify, risking blockage:

Additives and Color Coding

• Antioxidants, metal deactivators, static dissipators, biocides, anti-icing agents, corrosion inhibitors are common additives.
• Avgas color coding: 100LL (blue), 100/130 (green), 80/87 (red).
• Jet fuels: undyed (clear/straw).

Application & Use Cases

General Aviation

Mostly uses Avgas 100LL. Newer aircraft may use unleaded avgas, diesel/Jet A-1, or mogas with appropriate certification.

Commercial Aviation

Relies on Jet A-1 (global) and Jet A (US) for all turbine-powered airliners and most business jets. SAF blends are increasingly used for emissions reduction.

Military Aviation

Uses Jet A-1, Jet B, and military-specific grades (JP-8, JP-5). Additives support extreme performance and environmental conditions.

Experimental & Specialized Aviation

Includes research, UAVs, and demonstration flights using alternative fuels (SAF, hydrogen, electric) and mogas for approved light aircraft.

Safety Considerations

Aviation fuels are handled under rigorous safety and environmental protocols:

• Storage: Dedicated, certified tanks; floating roofs; grounding/bonding; fire suppression.
• Transfer: Strict documentation, regular testing for contamination/water.
• Handling: Trained personnel, PPE, emergency response plans.

Regulatory frameworks (ICAO, FAA, EASA) require ongoing inspection, testing, and traceability through the entire fuel supply chain to prevent cross-contamination and misfueling.

Environmental Impact & Future Trajectories

The environmental footprint of aviation fuel is substantial, driving innovation and regulation:

• Lead phase-out: Global efforts to replace leaded avgas with unleaded alternatives.
• SAF adoption: Reduces lifecycle CO₂ and particulate emissions.
• Hydrogen/electric: Long-term solutions for zero-emission flight, with ongoing R&D.

ICAO’s CORSIA and national mandates support sustainable aviation, while the industry invests in next-generation fuels and propulsion systems.

Summary

Aviation fuel is a cornerstone of safe, reliable, and efficient flight. Its production, certification, and handling are governed by the world’s strictest technical and regulatory standards, with ongoing innovation to address environmental, operational, and safety challenges. From avgas powering training aircraft to SAF fueling the future of global airlines, the evolution of aviation fuel is inseparable from the progress of aviation itself.

For technical guidance, regulatory updates, or support with sustainable fuel adoption, contact our aviation fuel experts.

Glossary last reviewed: June 2024