Standards & Tests

ASTM

The American Society for Testing and Materials (ASTM) has established specific standards for Sustainable Aviation Fuel (SAF) to ensure its safety, performance, and compatibility with existing jet engines and infrastructure. The key standard for SAF is ASTM D7566.

ASTM D7566: This is the primary standard that specifies the criteria for aviation turbine fuels containing synthesized hydrocarbons. It outlines the specifications and requirements that SAF must meet to be considered safe and effective for use in commercial aviation. Once SAF meets these criteria, it is re-identified as ASTM D1655 (the standard for conventional jet fuel), enabling it to be used interchangeably with traditional jet fuels.

ASTM D7566

To see the international standards formulated and guided by ASTM for testing in the various stages for sustainable aviation fuel, we add here the reference to official ASTM D4054-23 document:

ASTM D4054-23

Testing Tiers for SAF

SAF undergoes a rigorous certification process to ensure it meets performance and safety standards. This process is divided into several testing tiers:

Tier 1: Fuel Specification Properties
– Focuses on properties related to engine safety, performance, and durability.
– Standards referenced: ASTM D1655, DEF STAN 91-091, MIL-DTL-83133, MIL-DTL-5624.

Tier 2: Fit-for-Purpose Properties
– Bulk Physical and Performance Properties: Includes boiling point distribution, vapor/liquid ratio, thermal stability breakpoint, lubricity, viscosity, specific heat, density, surface tension, bulk modulus, thermal conductivity, water solubility, solubility of air.
– Electrical Properties: Dielectric constant, electrical conductivity, response to static dissipator.
– Ground Handling/Safety: Effect on clay filtration, filtration (coalescers & monitors), storage stability, toxicity, flammability limits, autoignition temperature, hot surface ignition temperature.
– Compatibility: Preliminary materials compatibility, additive compatibility & performance.

Tier 3: OEM Potential Test Requirements
– Compatibility: With engine and airframe seals, coatings, and metallics.
– Additive Compatibility: For new fuels only.
– Turbine Hot Section: Tests for oxidative or corrosive attack on turbine blade metallurgy and coatings.
– Component Tests: These include the fuel system, fuel control, fuel pump, fuel nozzle, APU cold filter, fuel gauging, and airframe fuel system.
– Combustor Rig Tests: Cold starting, lean blowout, aerial restarting, turbine inlet temperature distribution, combustor efficiency, flow path carboning/plating, emissions, APU altitude starting.

Tier 4: Engine Testing

– Endurance: Long-term performance and reliability.
– Performance: Efficiency and output.
– Operability: Functionality under various conditions.
– Aircraft Flight Testing: Real-world performance validation.
The process flow shows that if fuel or additive properties are acceptable after OEM review, it proceeds to further testing and validation. If the results validate suitability for engine/aircraft use, it advances to ASTM ballot. If not, the fuel or additive is rejected.

Where Tests Can Be Performed

The Technion team is working collaboratively with the Chemical Testing Laboratory and the Israeli Airforce Laboratories to enable national abilities to perform Tier 1-3 testing. Tier 1-2 are available at the CT-Lab and a Tier 3 testing facility is currently Under construction at the Aerospace Engineering Faculty – Technion.

In general – tests can be performed at —>

Many universities and research institutions have advanced laboratories capable of conducting Tier 1 and some Tier 2 testing. These facilities are equipped with state-of-the-art equipment to analyze the physical and chemical properties of fuels.
Companies like Rolls-Royce, GE Aviation, and Pratt & Whitney have the expertise and facilities to conduct Tier 2 and Tier 3 testing. These manufacturers often collaborate with fuel producers to test SAF in real-world conditions.
Organizations such as the National Aeronautics and Space Administration (NASA) and specialized aerospace testing centers have the infrastructure to conduct comprehensive Tier 3 and Tier 4 testing, including full-scale engine and flight tests.

A state-of-the-art testing facility with Tier 3 capabilities is currently being established by the Aerospace Engineering team at the Technion, as part of the Boeing–Technion SAF Innovation Center. Once completed, it will be only the second facility of its kind in the world in terms of testing capabilities.
Airlines, in partnership with aircraft manufacturers like Boeing and Airbus, often participate in Tier 4 testing. They conduct flight trials to ensure SAF performs adequately under various flight conditions.