The bulletin
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FAA Aviation Safety
SPECIAL AIRWORTHINESS
INFORMATION BULLETIN SUBJ: Engine Fuel and Control – Jet Fuel Aromatic Hydrocarbon Limits SAIB: HQ-18-30 Date: November 14, 2018 This is information only. Recommendations aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) advises airplane operators, fixed base operators (FBOs), FAA repair stations, Flight Standards District Offices (FSDOs), and foreign civil aviation authorities of jet fuel supplies for which the concentration of aromatic hydrocarbons and the net heat of combustion may not have been measured in accordance with methods specified by the type certificate (TC) holder. These jet fuel supplies would not be compliant with the FAA approved jet fuel operating limitations and should not be used on the TC holders’ products. The TC holders’ jet fuel operating limitations specify the maximum allowable aromatic hydrocarbon concentrations, the minimum net heat of combustion, and the test methods used to measure those values. Typically, the ASTM International Standard Test Method D1319, “Standard Test Method for Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption” is specified as the required test method for aromatics measurement. However, a dye necessary to conduct that test is currently unavailable. In addition, previously delivered supplies of that dye with lot numbers 3000000975, and above were produced with an incorrect dye and will not provide accurate measurements of aromatic concentration. Therefore, jet fuel that has not been tested for aromatics concentration in accordance with ASTM D1319, or in accordance with alternative test methods ASTM D6379 or ASTM D5186 (with TC holder approval), or was tested in accordance with ASTM D1319 with a dye from lot number 3000000975 and above, no longer meets the aviation fuel operating limitations of airplanes certificated to operate on Jet A fuel and cannot be used on those airplanes.
At this time, the airworthiness concern is not considered an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Aviation Regulations (14 CFR) part 39.
Background
The FAA relies on ASTM International to develop aviation fuel specifications and test methods that TC holders may designate as operating limitations for their approved products. The TC holders may also use these ASTM specifications and test methods to develop their own documents, such as company specifications, service bulletins and instructions, or other company documents, they designate as jet fuel operating limitations. These aviation fuel operating limitations may be listed in the product’s type certificate data sheet (TCDS), installation manual, service instructions, or as limitations associated with a supplemental type certificate (STC).
Aircraft and jet engine TC holders almost exclusively designate ASTM Standard Specification D1655, “Standard Specification for Aviation Turbine Fuels”, or company documents based on this specification, as a jet fuel operating limitation. ASTM D1655, and the associated company documents, specify a maximum allowable concentration of aromatics of 25 volume percent
2 measured by the ASTM Standard Test Method D13191. ASTM D63792, “Standard Test Method for Determination of Aromatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates—High Performance Liquid Chromatography Method with Refractive Index Detection” is also specified in D1655 with a maximum allowable concentration of 26.5 volume percent, but this method is rarely used, is not widely available, and is expensive to run.
ASTM D5186, “Standard Test Method for Determination of the Aromatic Content and Polynuclear Aromatic Content of Diesel Fuels and Aviation Turbine Fuels by Supercritical Fluid Chromatography” is another test method available from ASTM to measure the aromatic concentration of jet fuel. However, the D5186 test method was not incorporated into the D1655 jet fuel specification, nor the TC holder’s company documents based on D1655, because it reports aromatics in mass percent, not volume percent. At present, the D5186 test method cannot be used for compliance with the jet fuel operating limitations, unless approved by the TC holder as a change to their FAA approved operating limitations. This change would need to either specify a new limit in terms of mass percent, or include a method to convert mass percent to volume percent for comparison with the current limit.
Aromatic hydrocarbons are limited in jet fuel because they emit more radiant energy during combustion than paraffinic hydrocarbons. At high concentrations, this can have an adverse effect on turbine engine combustor durability. They also produce more smoke and harmful particulate emissions than paraffinic hydrocarbons and are limited due to environmental concerns.
ASTM D1655, and the associated company documents, also specify a minimum allowable net heat of combustion requirement of 42.8 MJ/kg as calculated by one of two methods; ASTM D3338, “Standard Test Method for Estimation of Net Heat of Combustion of Aviation Fuels”, or ASTM D4529, “Standard Test Method for Estimation of Net Heat of Combustion of Aviation Fuels”, or obtained by testing using ASTM D4809, “Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter (Precision Method)”. A minimum value for net heat of combustion is required in jet fuel to ensure the fuel has sufficient energy content to meet the aircraft’s range requirements. The calculation of net heat of combustion utilizing the ASTM D3338 test method cannot be accomplished without the aromatics concentration. Fuel suppliers will need to either use the alternative calculation method, ASTM D4529, or need to conduct the bomb calorimeter test in accordance with ASTM D4809. Jet fuel for which the net heat of combustion has not been determined by calculation using ASTM D3338 or ASTM D4529, or by test using ASTM D4809, no longer meets the aviation fuel operating limitations of airplanes certificated to operate on Jet A fuel, and therefore, cannot be used on those airplanes.
1 The information and recommendations of this SAIB also apply to test method IP 156, “Determination of Hydrocarbon Types in Petroleum Products - Fluorescent indicator adsorption method”, available from the Energy Institute, 61 New Cavendish Street, London, W1G 7AR, UK. IP 156 is specified in ASTM D1655 as an equivalent test method for measurement of aromatics.
2 The information and recommendations of this SAIB also apply to test method IP 436, “Determination of Aromatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates - High Performance Liquid Chromatography Method with Refractive Index Detection”, available from the Energy Institute, 61 New Cavendish Street, London, W1G 7AR, UK. IP 436 is specified in ASTM D1655 as an equivalent test method for measurement of aromatics.
3 Recommendations
The FAA recommends the following:
1. Owners and operators of turbine engine-powered aircraft verify the aromatics concentration of jet fuel supplied to their aircraft is within the limits specified in the aircraft’s operating limitations, and that jet fuel has been tested for aromatics concentration in accordance with the following:
a. ASTM D1319 with a dye from lot number lower than 3000000975, or
b. ASTM D6379, or
c. ASTM D5186, but only if the TC holder has approved use of that method, and the aromatic concentration complies with the specified limit in the operating limitations.
2. Owners and operators of turbine engine-powered aircraft verify the net heat of combustion of jet fuel supplied to their aircraft is within the limits specified in the aircraft’s operating limitations, and it has been determined using one of the following methods:
a. ASTM D3338, or
b. ASTM D4529, or
c. ASTM D4809.
3. Owners and operators of turbine engine-powered aircraft advise fuel suppliers that operators cannot use jet fuel that has not been tested for aromatics concentration in accordance with one of the following methods:
a. ASTM D1319 with a dye from lot number lower than 3000000975, or
b. ASTM D6379, or
c. ASTM 5186, but only if the TC holder has approved use of that method, and the aromatic concentration complies with the specified limit in the operating limitations.
4. Owners and operators of turbine engine-powered aircraft advise fuel suppliers that operators cannot use jet fuel that has not had the net heat of combustion determined using one of the following methods:
a. ASTM D3338, or
b. ASTM D4529, or
c. ASTM D4809.
For Further Information Contact
Mark Rumizen, Senior Technical Specialist, FAA, 1200 District Avenue, Burlington, MA 01803;
phone: (781) 238-7113; mobile: (781) 402-4609; fax: (781) 238-7199; email:
mark.rumizen@faa.gov.