Advisory Circular Subject: Approval of Propulsion Fuels, Additives, and Lubricating Oils Date: February 20, 2018 Initiated By: AIR–20 AC No: 20-24D Change 1
1. Purpose. This advisory circular (AC) change updates the references provided in the original document. This advisory circular (AC) provides guidance applicable to adding fuels and oils as engine, aircraft, or auxiliary power unit (APU) operating limitations. It also provides guidance on fuel and lubricating oil specifications and standards, and on propulsion fuel and/or lubricating oil certification plans.
2. Principal Changes.
a. Paragraphs 4.f, 4.k, 5.b.19, 6.e, 6.f, 7.d.1, 8.c.(2)(b)1, 8.f.(7)(a), 8.f.(7)(d), 9.a.(3)(a) are changed to add related regulations.
b. The AC change number and the date of the change is shown at the top of each applicable page. The change bar in the right or left margin indicates where the change is located. The changes described may shift the original text.
Page Control Chart Changed Pages Dated 2 2/20/18 4 2/20/18 5 2/20/18 6 2/20/18 10 2/20/18 15 2/20/18 16 2/20/18 17 2/20/18
3. Website Availability. To access this AC electronically, go to the AC library at http://www.faa.gov/regulations_policies/advisory_circulars/.
Peter A. White Manager, Alternative Fuels Program Staff Aircraft Certification Service
U.S. Department of Transportation Federal Aviation Administration Advisory Circular
Subject: Approval of Propulsion Fuels, Additives, and Lubricating Oils Date: 6/30/14 Initiated by: AIR-20 AC No: 20-24D
1. Purpose. This advisory circular (AC) provides guidance applicable to adding fuels and oils as engine, aircraft, or auxiliary power unit (APU) operating limitations. It also provides guidance on fuel and lubricating oil specifications and standards, and on propulsion fuel and/or lubricating oil certification plans. This AC provides acceptable methods, but not the only methods, that may be used to approve aircraft, engines, or APUs to operate with specified propulsion fuels and lubricating oils.
2. Applicability.
a. The guidance provided in this document is directed to engine and APU manufacturers, airplane manufacturers, rotorcraft manufacturers, modifiers, and foreign regulatory authorities. This guidance also applies to manufacturers of aviation fuels and lubricating oils.
b. This material is neither mandatory nor regulatory in nature and does not constitute a regulation. It describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulations. The FAA (Federal Aviation Administration) will consider other methods an applicant may present to demonstrate compliance. Terms such as “should,” “may,” and “must” are used only in the sense of ensuring applicability of this particular method of compliance when the method in this document is used. While these guidelines are not mandatory, they are derived from extensive FAA and industry experience in determining compliance with the relevant regulations. If we find that following this AC would not result in compliance with the applicable regulations, we will not be bound by this AC, and we may require additional substantiation as the basis for finding compliance.
c. This material does not change, create any additional, authorize changes in, or permit deviations from existing regulatory requirements.
3. Cancellation. AC 20-24C, Approval of Propulsion Fuels and Lubricating Oils, dated July 29, 2011, is cancelled.
4. Related Regulations. The following regulations from Title 14 of the Code of Federal Regulations (14 CFR) are some of the regulations that apply (see appendices 2 and 3 of this AC for additional applicable regulations):
a. Section 33.7(b)(2) and (3), Engine ratings and operating limitations (Fuel, Oil).
b. Section 23.1521(d), Fuel grade or designation.
c. Section 23.1522, Auxiliary power unit limitations.
d. Section 23.1583(b)(1), Operating limitations.
e. Section 25.1521, Powerplant limitations.
f. Section 25.1522, Auxiliary power unit limitations.
g. Section 25.1583(b)(1), Operating limitations.
h. Section 27.1521(d), Powerplant limitations.
i. Section 27.1583(b)(1), Operating limitations.
j. Section 29.1521(d), Powerplant limitations.
k. Section 29.1522, Auxiliary power unit limitations.
l. Section 29.1583(b)(1), Operating limitations.
m. Section 91.9, Civil aircraft flight manual, marking, and placard requirements.
n. Appendix G23.3(a)(4), Instructions for continued airworthiness, servicing information.
o. Appendix H25.3(a)(4), Instructions for continued airworthiness, servicing information.
p. Appendix A27.3(a)(4), Instructions for continued airworthiness, servicing information.
q. Appendix A29.3(a)(4), Instructions for continued airworthiness, servicing information.
5. References and Related Reading.
a. FAA Guidance. The following materials are referenced in this document. Unless otherwise dated, you should use the current edition.
(1) Policy Memorandum ANE-2006-33.7-4-1, “Policy for Diesel (Compression Ignition) Engine Certification,”.
(2) Policy Memorandum ANE-2010-33.7-5A, “Policy for Aviation Fuel and Oil Operating Limitations, § 33.7,”
(3) AC 23.1521-1, “Type Certification of Automobile Gasoline in Part 23 Airplanes with Reciprocating Engines,”.
(4) AC 23.1521-2, “Type Certification of Oxygenates and Oxygenated Gasoline Fuels in Part 23 Airplanes with Reciprocating Engines,”.
(5) AC 33.47-1, “Detonation Testing in Reciprocating Aircraft Engines,” dated June 27, 1988.
(6) AC 91-33A, “Use of Alternate Grades of Aviation Gasoline for Grade 80/87, and Use of Automotive Gasoline,” dated July 18, 1984.
b. Industry Guidance.
(1) ASTM International Subcommittee D.02.J Operating Procedures, Annex A6, “Guidelines for the Development and Acceptance of a New Aviation Fuel Specification For Spark-Ignition Reciprocating Engines.”
(2) ASTM International Standard D910, “Standard Specification for Aviation Gasolines.”
(3) ASTM International Standard D1655, “Standard Specification for Aviation Turbine Fuels.”
(4) ASTM International Standard Practice D4054, “Standard Practice for Qualification and Approval of New Aviation Turbine Fuels and Fuel Additives.”
(5) ASTM International Standard D6227, “Standard Specification for Grade UL82 and UL87 Unleaded Aviation Gasoline.”
(6) ASTM International Standard Practice D6424, “Standard Practice for Octane Rating Naturally Aspirated Spark Ignition Aircraft Engines.”
(7) ASTM International Standard D6615, “Standard Specification for Jet B Wide-Cut Aviation Turbine Fuels.”
(8) ASTM International Standard Practice D6812, “Standard Practice for Ground-Based Octane Rating Procedures for Turbocharged/Supercharged Spark Ignition Aircraft Engines.”
(9) ASTM International Standard D7223, “Standard Specification for Aviation Certification Turbine Fuel.”
(10) ASTM International Standard D7566, “Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons.”
(11) ASTM International Standard D7547, “Standard Specification for Unleaded Aviation Gasoline.”
(12) CRC Report No. 635, “Handbook Of Aviation Fuel Properties,” 2004 Third Edition, Coordinating Research Council, Inc.
(13) Defence Standard 91-86, “Turbine Fuel, Aviation KerosineType: High Flash Type, Containing Fuel System Icing Inhibitor,” issued by the United Kingdom (U.K.) Ministry of Defence.
(14) Defence Standard 91-87, “Turbine Fuel, Aviation Kerosine Type, Containing Fuel System Icing Inhibitor,” issued by the U.K. Ministry of Defence.
(15) Defence Standard 91-90, “Gasoline, Aviation: Grades 80/87, 100/130 and 100/130 Low Lead. Joint Service Designation: AVGAS 80, AVGAS 100 and AVGAS 100LL.”
(16) Defence Standard 91-91, “Turbine Fuel, Aviation Kerosine Type, Jet A-1 NATO Code: F-35, Joint Service Designation: AVTUR.”
(17) MIL-DTL-5624, Detail Specification, Turbine Fuel, Aviation, Grades JP-4 and JP-5, issued by the U.S. DOD.
(18) MIL-DTL-83133, Detail Specification, Turbine Fuel, Aviation Kerosene Type, JP-8, and JP-8+100 issued by the U.S. Department of Defense (DOD).
(19) MIL-HDBK-510, “Department of Defense Handbook, Aerospace Fuels Certification.”
(20) RTCA Document No. (RTCA/DO)-160G, “Environmental Conditions and Test Procedures for Airborne Equipment,” dated December 8, 2010.
(21) SAE International Surface Vehicle Standard J1899, “Lubricating Oil, Aircraft Piston Engine (Ashless Dispersant).”
(22) SAE International Surface Vehicle Standard J1966, “Lubricating Oils, Aircraft Piston Engine (Non-Dispersant Mineral Oil).”
(23) SAE International Aerospace Standard AS5780, “Specification for Aero and Aero Derived Gas Turbine Engine Lubricants.”
6. Definitions. The following definitions apply for the purposes of this AC.
a. Consensus. A general agreement, but not necessarily unanimity, that includes a process for attempting to resolve objections by interested parties. This process is a comment resolution process, which requires fair consideration of all comments, and each objector is advised of the disposition of his or her objection(s) and the reasons why. In addition, consensus body members may change their votes after reviewing the comments.
b. Fuel or Oil Grade or Designation. A descriptive term used to identify a fuel or oil that meets certain performance requirements and other characteristics defined in an industry, governmental, or military specification.
c. Voluntary Consensus Standards. Standards developed or adopted by voluntary consensus standards bodies, both domestic and international. ‘‘Technical standards that are developed or adopted by voluntary consensus standard bodies,’’ is an equivalent term.
d. Voluntary Consensus Standards Bodies. Domestic or international organizations that plan, develop, establish, or coordinate voluntary consensus standards using agreed-upon procedures.
‘‘Voluntary, private sector, consensus standards bodies’’ is equivalent to voluntary consensus standards bodies. Federal law encourages the participation of federal representatives in these bodies to increase the likelihood that the standards they develop will meet public and private sector needs. A voluntary consensus standards body has the following attributes:
(1) Openness,
(2) Balanced interests,
(3) An appeals process, and
(4) Consensus.
e. Independent Specifications. These specifications define new fuels not addressed by existing government, military, or industry voluntary consensus-based specifications. The Independent Specifications are developed and issued by an independent organization, company, or individual that are not sanctioned, issued, or approved by a government, military, or industry voluntary consensus-based organization. This excludes company specifications, service bulletins or other documents that are issued to communicate the acceptability of existing aviation fuels that reference the fuel properties or other criteria for those existing fuels.
f. Original Equipment Manufacturers (OEM) Fuel Operating Limitation Documents.
Specifications, service bulletins, or other documents that are issued by aircraft and engine OEMs that encompass fuel properties and other criteria from widely accepted government, military, or industry voluntary consensus-based aviation fuel specifications. These are typically listed as aviation fuel operating limitations in lieu of listing multiple aviation fuel specifications from each separate government, military, or industry voluntary consensus-based organizations.
7. Background.
a. 14 CFR requires that type certificate (TC) applicants identify the fuel and oil grade, designation, and/or specifications that are used in their products during certification. Once compliance with the airworthiness certification regulations is demonstrated, the grade, designation, and/or specification becomes part of the airplane, rotorcraft, and engine operating limitations. These operating limitations are specified in the type certificate data sheet (TCDS) and in the airplane flight manual (AFM) or rotorcraft flight manual (RFM).
Aircraft operators are required by § 91.9 to comply with the AFM or RFM. Operators must use only those fuels and oils listed in the AFM and RFM. The operating limitations, therefore, must be precise ensuring the fuel and oil is controlled enabling the engine and aircraft to continue to meet their airworthiness certification basis during service.
b. Historically, the FAA used the voluntary consensus standards from ASTM or SAE to identify fuel and oil grades, designations, brand name designations, or specifications to be identified on a TCDS. Applicants demonstrated that the product (for example, the engine or airplane) operated as designed over its complete operating range using the proposed fuel or oil.
Applicants demonstrated this during a TC, amended TC, supplemental TC (STC), or amended STC (ASTC) program. Once demonstrated, the FAA issued the TC, amended TC, STC, or ASTC with the fuel or oil identified as an operating limitation. Thereafter, when applicants proposed adding new fuels or oils to an existing TC or STC, those new fuels or oils were also identified by grade designations, brand name designations, and/or ASTM or SAE industrybased consensus specifications. As with the original demonstration, applicants then demonstrated that the aircraft or engine complied with the certification basis. See appendices of this AC for a list (not all-inclusive list) of regulations. After the demonstration, the FAA identified the new fuel or oil grade, designation, or specification, as an operating limitation.
c. Historically, the FAA recognized the MIL-STD process and the controls in place by the U.S.
military. Accordingly, the FAA has accepted their grades, designations, and/or specifications as sufficient to meet its regulatory needs related to identifying fuels and oils as operating limitations on a TCDS.
d. The FAA continues to accept this historical approach in identifying new fuels and oils through a consensus-based industry organization, governmental, or military standard. After the proper regulatory demonstration, the fuel or oil can be identified as an operating limitation on a TC.
(1) Accordingly, fuels identified by an ASTM, governmental or military specification, or other industry-based consensus organization specification, are considered to be identified in sufficient detail to be accepted by the FAA as fuel operating limitations on a TC, amended TC, STC, or ASTC. It is also acceptable to specify the operating limitation as an OEM Fuel Operating Limitation Document that encompasses fuel properties and other criteria from widely accepted government, military, or industry voluntary consensus-based aviation fuel specifications.
(2) Oils identified by an SAE oil standard or a brand name that meets an SAE standard, governmental or military specification, or other industry-based consensus organization specification, are considered to be identified in sufficient detail to be accepted by the FAA as oil operating limitations on a TC, amended TC, STC, or ASTC.
e. The FAA will also accept fuels identified by independent specifications, provided the specification meets the criteria specified in paragraph 8.e. of this AC.
f. Applicants proposing to add a fuel to a product’s TC, or as an STC, should first contact the FAA and provide either:
(1) An industry voluntary consensus, governmental, or military organization standard or specification they intend to use, or
(2) An independent specification that meets the criteria specified in paragraph 8.e. of this AC that they intend to use.
g. Applicants proposing an oil for a product should first contact the FAA and provide the industry voluntary consensus, governmental, or military organization standard or specification they propose to add to a TC, STC, or ASTC.
h. The applicant should then coordinate with the FAA to develop compliance plans and conduct the engine, airplane, or APU certification programs. The applicant may proceed with the certification program with a preliminary version of the submitted specification, but must substantiate that the tested fuel or oil meets the final issued version of the specification before the FAA issues the final design approval.
i. Once the applicant successfully completes the demonstration of compliance, the proposed fuel, as identified by specification number, and any other information necessary to define the fuel, may be included as an operating limitation on the product’s TCDS by the FAA. For example, the fuel could be identified by specification number and octane requirement or grade.
Oil could be identified by a specification number, or any other information necessary, such as brand name or grade. These operating limitations will also be identified by the applicant in the operating and installation instructions, flight manuals, and other service documents. Further, a successful completion of the compliance plan means an applicant successfully demonstrates that the product, when operated with the proposed fuel or oil, continues to meet the certification requirements of the specific engine, APU, and aircraft, for example, 14 CFR parts 21, 23, 25, 27, 29, 33 and 35, technical standard order (TSO), TSO-C77, etc.
(1) Approved fuels are described in the operating limitations (located in the TCDS and AFM, or STC and aircraft flight manual supplement (AFMS), whichever is applicable), engine installation and operating instructions, and the engine and aircraft maintenance manuals in a manner consistent with the examples below:
(a) Jet A or Jet A1, meeting ASTM D1655.
(b) Grade 100LL, meeting ASTM D910.
(2) Approved oils are described in the operating limitations (located in the TCDS and AFM, or STC and AFMS, whichever is applicable), engine installation and operating instructions, and the engine and aircraft maintenance manuals in a manner consistent with the example below:
(a) Aeroshell Oil W 15W-50, meeting SAE International Standard, SAE J1899.
8. Aviation Fuel.
a. Historically Accepted Aviation Fuel Specifications.
(1) The primary specification for Jet A and Jet A-1 turbine engine aviation fuel is ASTM International Standard D1655, “Standard Specification for Aviation Turbine Fuels.” This specification describes acceptable materials for producing turbine engine fuel, required properties that the fuel must meet, and test methods to measure those properties.
(2) U.S. Military fuel specifications. The following are examples of military aviation fuel specifications, which are operating limitations on some U.S. products:
(a) MIL-DTL-83133, Detail Specification, Turbine Fuel, Aviation Kerosene Type, JP- 8, and JP-8+100, issued by the U.S. Department of Defense (DoD).
(b) MIL-DTL-5624, Detail Specification, Turbine Fuel, Aviation, Grades JP-4 and JP- 5, issued by the U.S. DoD.
(3) Turbine engine international fuel specifications. The following are examples of international aviation fuel specifications, which are operating limitations on some U.S. products:
(a) Defence Standards 91-91, “Turbine Fuel, Aviation Kerosine Type, Jet A-1” and 91-87, “Turbine Fuel, Aviation Kerosine Type, Containing Fuel System Icing Inhibitor” issued by the United Kingdom (U.K.) Ministry of Defence. These standards are produced for the U.K.’s Defence Fuels and Lubricants Committee (DFLC) in collaboration with the Aviation Fuels Committee (AFC).
(b) CAN/CGSB-3.23, “Aviation Turbine Fuel, Kerosene Type,” which includes grades Jet A and Jet A-1, and CGSB 3.24, “Aviation Turbine Fuel (Military Grades F-34 and F-44),” issued by the Canadian General Standards Board (CGSB).
(c) GOST (Gosudarstvennyy Standart) 10227, “Jet Fuels Specification,” including grades TS-1 and RT, issued by the Russia State Standard Committee. These are the predominant fuels used in Russia, the Commonwealth of Independent States, and some Eastern European countries.
(d) GB 6537, “No. 3 Jet Fuel,” issued by China’s National Technology Supervisory Bureau. This specification describes the fuel predominately offered at major international airports in China.
(4) Reciprocating spark ignition (SI) fuel specification(s). ASTM International Standard D910, “Standard Specification for Aviation Gasolines,” is the primary specification for reciprocating SI engine aviation fuel. This specification describes acceptable materials for producing leaded aviation gasoline, required properties that the fuel must meet, and test methods to measure those properties. Other specifications for reciprocating SI engine aviation fuel include:
(a) ASTM D6227, “Standard Specification for Grade UL82 and UL87 Unleaded Aviation Gasoline.”
(b) ASTM D7547, “Standard Specification for Unleaded Aviation Gasoline.”
(c) ASTM D7592, “Standard Specification for Specification for Grade 94 Unleaded Aviation Gasoline Certification and Test Fuel.”
(d) Defence Standard 91-90, “Gasoline, Aviation: Grades 80/87, 100/130 and 100/130 Low Lead,” issued by the U.K. Ministry of Defence. This standard is produced for the U.K.’s DFLC in collaboration with the AFC.
(e) Russian GOST 1012-72, “Aviation petrols - Specifications,” issued by the Russia State Standard Committee.
(f) GB/T1787-79(88), issued by China’s National Technology Supervisory Bureau.
b. Operating Limitations for Aviation Fuel.
(1) Operating limitations are part of the type certificate for each certificated product. The following are some of the regulations that apply to fuel operating limitations:
(a) Engine operating limitations for fuel are required by § 33.7(b)(2) (reciprocating engine) and § 33.7(c)(2) (turbine engine).
(b) Airplane operating limitations for fuel are required by § 23.1521(d), and §§
25.1521(b)(2) and (c)(2) (transport category).
(c) APU operating limitations for fuel are required by § 23.1522, § 25.1522, and § 29.1522.
(d) Rotorcraft operating limitations for fuel are required by § 27.1521(d) (normal category) and § 29.1521(d) (transport category).
c. ASTM Aviation Fuel Specifications as Operating Limitations for Aviation Fuel.
(1) The FAA has determined that ASTM aviation fuel specifications are acceptable specifications, and may be identified as operating limitations for fuel. The root number of the ASTM fuel specification (e.g., D1655; except as noted in paragraph 8.c.(2)(c) of this AC) and any other information necessary to define the fuel, such as octane requirement or grade used to successfully complete the compliance demonstration, will be listed in the engine and aircraft TCDS. Manufacturers will also list the specifications in the documents referenced in the TCDS.
For STC projects, the fuel specification root number (except as noted in paragraph 8.c.(2)(c) of this AC) and any other information necessary to define the fuel, such as octane requirement or grade, will be listed in the limitations section of the STC. When applicants present a fuel specification from another industry-based consensus organization or a governmental or military specification, they should present sufficient information regarding how the specification is identified, allowing for adequate reference as an operating limitation.
(2) Special Considerations Applicable to ASTM Aviation Fuel Specifications.
(a) Minor Revisions to ASTM Aviation Fuel Specifications. Revisions to fuel specifications that are not significant enough to impact the suitability of the fuel for its intended use are incorporated as minor revisions under the existing specification root number. Each minor revision of the specification is then identified by a new suffix number, which is typically
issued on an annual basis. These minor revisions consist of editorial changes, wording clarifications, or changes in criteria, materials, or processes. These changes are not extensive enough to require the issuance of a new specification.
1 Operating limitations that specify an ASTM fuel specification root number only does not require an amendment to that approval when minor revisions are incorporated into that ASTM fuel specification.
2 Operating limitations that specify an ASTM fuel specification root number and suffix number do require an amendment to that approval when minor revisions are incorporated into that ASTM fuel specification (see paragraph 8.c.(2)(c) of this AC).
(b) Synthetic Jet Fuels. ASTM D1655, “Standard Specification for Aviation Turbine Fuels,” defines specification criteria for conventional jet fuel. This specification requires that the jet fuel be produced from conventional raw materials, such as petroleum, tar sands, or shale oil.
However, new processing techniques are emerging that will allow jet fuel to be produced from other raw materials, such as biomass, natural gas, or coal. ASTM has issued two standards intended to facilitate the evaluation of synthetic jet fuel produced from non-conventional sources, and the integration of these fuels into the existing supply system and onto existing aircraft.
1 ASTM D4054, “Standard Practice for Qualification and Approval of New Aviation Turbine Fuels and Fuel Additives,” provides a procedure for evaluating new jet fuels or significant modifications to existing fuels to determine if the new fuel is suitable for aviation use.
Seemingly, minor changes to specification properties or criteria may result in changes in a fuel’s performance, but the laboratory, rig, and engine tests specified in D4054 are sufficient to fully evaluate the fit for purpose or suitability of new fuels with engine and airframe fuel systems.
The D4054 evaluation is conducted for both new fuels and revisions to existing fuel properties to verify that the resulting fuel is suitable for aviation use, based on its performance characteristics and chemical compositions. The U.S. DoD has developed a similar document, MIL-HDBK-510A, for the evaluation of fuels to be used on military aircraft.
2 ASTM D7566, “Aviation Turbine Fuel Containing Synthesized Hydrocarbons.”
This specification defines criteria for synthetic jet fuels that have been qualified to ASTM D4054. Because D7566 fuels meet or exceed the requirements of D1655 fuels, both of these specifications are cross-referenced to allow D7566 fuels to be redesignated as D1655 fuels. A redesignated fuel can move seamlessly through the ground distribution infrastructure without separate tracking. The redesignated fuel can also be used in aircraft without amending the operating limitations of those aircraft.
3 If the fuel type is incorporated in D7566 and current specified operating limitations are adequate to accommodate D1655 fuels, then further FAA testing is not required.
4 TC/STC holders do not need to revise aviation fuel operating limitations to use D7566 fuels that have been redesignated to D1655 fuels, if the existing operating limitations include D1655 fuels.
(c) ASTM Non-Applicable Fuel Specifications. Non-applicable ASTM fuel specifications are those ASTM specifications in which the scope does not include aircraft engines, or does not explicitly include the intended type of aircraft or aircraft