§§ 23.603, 25.603, 27.603, and 29.603). This may require testing of both used and unused non-metallic parts, such as elastomers and seals, if the fuel is to be used on aircraft previously operated with other types of fuel.
(d) Applicants should evaluate the e ffect of differences in fuel properties such as density, energy content and combustion characteristics on installed engine and APU performance, including in-flight restarting (see §§ 25.901(d), 25.903(a), 25.903(e),
25.903(f), 25.939, 23.901(d), 23.903, 23.903(d), 23.939, 27.903, 27.903(d), 27.939,
29.903, 29.903(e), 29.923(p), and 29.939).
(e) Fuel performance in high temperature conditions can be influenced by fuel properties such as vapor pressure, liquid/vapor ratio, and thermal conductivity.
Applicants should therefore, evaluate fuel system hot weather and engine cooling performance when operating with the new fuel (see §§ 23.961, 25.961, 27.961, 29.961,
25.1041, 25.1043, 25.1045, 23.1041, 23.1043, 23.1045, 23.1047, 27.1041, 27.1043,
27.1045, 29.1041, 29.1043, 29.1045, 29.1047, and 29.1049).
(f) Applicants should show the fuel is compatible with the aircraft fuel system components and that the fuel does not have any adverse effect on fuel system performance. This demonstration should include an evaluation of fuel properties such as flash point or vapor pressure for their effect on the fuel in the fuel tank, including flammability.
1 Fuel properties such as the dielectric/density relationship can change the gauging system function since some gauging systems do not have densitometers and are based on an assumed relationship for typical kerosene fuels.
2 Some fuel types can also cause corrosion and adversely affect material properties and durability of engine fuel system components as discussed in paragraph 8c.(8)(a) above.
3 Some fuel types can also have an affinity for water retention and icing, which could lead to stoppage of fuel flow or corrosion.
4 A comprehensive compliance plan should also include an analysis of the effect of fuel properties such as viscosity on fuel system pressure drop and fuel pump performance
5 See §§ 25.951, 25.952, 25.955, 25.959, 25.969, 25.975, 25.979,
25.981, 25.997, 25.1001, 25.1305, 25.1337, 23.951, 23.955, 23.959, 23.969, 23.973(e)(f),
23.975, 23.979, 23.997, 23.1001, 23.1305, 23.1337, 27.951, 27.955, 27.959, 27.965,
27.969, 27.997, 29.951, 29.955, 29.959, 29.969, 29.975, 29.979, 29.997, 29.1001,
29.1305, and 29.1337.
9. Lubricating Oil.
a. Historically A ccepted Oil Standards.
(1) Commercial turbine engine t ype design holders traditionally used performance standard MIL-PRF-23699 to qualify engine oil. Today, SAE International Aerospace Standard AS5780, “Specification for Aero and Aero Derived Gas Turbine Engine Lubricants,” replaces MIL-PRF-23699 for commercial turbine engines.
(2) SAE AS5780 defines physical, chemical, and performance limits for gas turbine engine oils along with standard test methods and requirements. It includes specialized laboratory and rig testing to determine if the oil is suitable for aircraft turbine engines. It also defines quality control requirements to ensure batch conformance and materials traceability, and it includes procedures to manage and communicate changes in oil formulation and brand.
(a) SAE AS5780 is maintained by SAE Technical Committee E-34, Propulsion Lubricants. The SAE E-34 Propulsion Lubricants committee addresses all facets of aerospace propulsion lubricants—development, maintenance, and in-service experience. This work includes lubricants used for gas turbine engines, aircraft gearboxes and accessories.
(3) Similarly, commercial and military engine type design holders used MIL-L- 6082 (Non-Dispersant Mineral Oil) and MIL-L-22851 (Ashless Dispersant) for conventional spark ignition reciprocating engines. However, SAE Surface Vehicle Standard J1899, “Lubricating Oil, Aircraft Piston Engine (Ashless Dispersant)” and SAE Surface Vehicle Standard J1966, “Lubricating Oils, Aircraft Piston Engine (Non- Dispersant Mineral Oil),” replaced the military specifications as the primary standards for conventional spark ignition reciprocating engine oil. These specifications define physical, chemical, and performance limits for conventional spark ignition reciprocating engine oils along with standard test methods and requirements. They include specialized laboratory and rig testing to determine if the oil is suitable for aircraft conventional spark ignition reciprocating engines. They also define quality control requirements to assure batch conformance and materials traceability. SAE Standards J1899 and J1966 are maintained by the SAE Fuels and Lubricants Technical Committee 8 (TC-8) Aviation Piston Engine Lubricants.
b. Operating Limitations for Lubricating Oil .
(1) FAA regulations also require th at the Administrator establish engine operating limitations related to oil. These operating limitations are also included in the engine TCDS for each type certificated design. Operating limitations for oil are related to oil grade or specifications for reciprocating and turbine engines.
(2) The FAA determined that SAE grade or specification known as an SAE standard, or oil formulation brand designation(s) based on SAE standards are acceptable to include as engine operating limitations related to oil. Once the compliance plan is successfully completed, the oil formulation brand designation or the standard number will
be listed in the engine TCDS or in manufacturers’ documents referenced in the TCDS.
For STC projects, the oil formulation brand designation or the standard number will be listed in the limitations section of the STC.
(3) Special Considerations.
(a) Oil Formulation Brand Name Designation. Turbine engines generally require lubricating oils that meet SAE AS5780 standard, but the operating limitation specified in the engine TC is most often listed as the brand name(s) of specific oil formulations. Similarly, conventional spark ignition piston engine lubricating oil typically meets SAE J1899 or J1966 standards with the operating limitations listed as brand name(s) of specific oil formulations. This is a more specific means of identification than simply referencing SAE AS5780, J1899 or J1966, and therefore, specifying the brand name is generally acceptable for establishing an operating limitation related to oil, as required by §§ 33.7(b)(3) and (c)(3). Specifying AS5780, J1899 or J1966 is also acceptable if the engine manufacturer has demonstrated that any oil with properties that fall within the range of criteria in the specification is acceptable for use in the subject engine.
(b) Changes to SAE Approved O il Formulation. Oil manufacturers may change oil formulation, base stock composition, additive composition, or manufacturing plant location. SAE requires brand re-identification when these changes are shown to affect oil performance, as defined by AS5780. This brand re-identification will result in applicants requesting a change to the TC or STC to add the new brand as an operating limitation.
1 If SAE determines the change does not require a change to the brand name, then the specified operating limitation is still valid, and accordingly, no change to the TC or STC is required. This is because operating limitations relative to oil are typically defined in terms of the brand name.
2 If SAE determines the change requires a brand name reidentification, then the SAE industry oversight group generally evaluates the change in parallel with the engine manufacturer’s FAA design change control process. The industry oversight group’s report and associated evidence can be used to support the FAA’s review process.
(c) Other governmental military or industry voluntary consensus-based standards or specifications. If an applicant proposes to specify an aviation oil identified by another governmental, military or industry voluntary consensus-based standard, or specification, then the applicant should present sufficient information to show that the oil grade, brand name or specification provides an equivalent level of property, performance, and quality control.
c. Operating Limitations for Oil: Certification Compliance Plans .
(1) The E&PD is the FAA’s technical focal point for identifying the applicable airworthiness certification requirements involving aviation oil. Applicable airworthiness requirements are those FAA regulatory standards for which the showing of compliance is contingent on oil properties. Once applicants present the industry consensus-based, governmental, or military oil brand, standard, grade, or specification to the E&PD, the Directorate will aid applicants as they develop their compliance plan.
(2) An applicant’s compliance plan should address all applicable airworthiness certification standards, some of which are discussed below. Sound testing techniques and thorough data analysis should also be well documented in the compliance plan.
Accordingly, close contact and frequent coordination are recommended to ensure the plan is developed with minimal delay.
(3) An applicant’s compliance plan s hould also address the effects of mixing the proposed new oil with other types of oil, such as mixing a new brand with an existing brand. Data generated during the development of the industry consensus-based, military, or governmental oil specification may be used to support this task.
(4) Applicants using engine oil for airplane or rotorcraft systems must demonstrate that the engine and the airplane or rotorcraft in which the engine is installed continue to meet all certification standards. If a qualification project for a new operating limitation for oil for an APU is required for a new TSO, major change, or STC, then the compliance plan should include the applicable requirements and performance standards from the latest revision of TSO C77.
d. Applicable Regulatio ns for Engines and APUs. See appendix 2 of this AC, paragraphs 4, 5, and 6 for a list of some of the regulations that may apply to oil projects.
Additional guidance on some airworthiness standards follows. The following list is by no means exclusive, and is provided as a recommended starting point only. Applicants should therefore, obtain from the E&PD, as the FAA’s lubricating oil focal point, guidance on regulations with which they will need to show compliance.
(1) Applicants should review the design of the turbine engine oil system and provide data that shows that the new turbine engine oil will not result in harmful build-up of carbon deposits for compliance with §§ 33.19 and 33.71. This can be accomplished by any combination of engine test, rig test, and analysis based on prior service experience or testing. Applicants who propose a longer, mature engine maintenance interval or TBO for a new turbine or reciprocating engine, or propose to maintain the TBO or other major maintenance interval of an existing, mature turbine or reciprocating engine, may need to perform a long duration engine test beyond that specified in §§ 33.49 or 33.87 to show compliance with §§ 33.15 and 33.19 (see §§ 33.19 33.39, and 33.71).
(2) Applicants should also include in the Instructions for Continued Airworthiness if applicable, instructions for inspections, repair, and cleaning of turbine
engine areas or components shown to be susceptible to carbon deposits build-up. These instructions should be derived from the review of the oil system design accomplished during compliance with § 33.71 and 33.19.
(3) If all oil-wetted materials on the specific engine model under review were not evaluated during the SAE qualification process, additional materials compatibility testing will be necessary (see § 33.15).
e. Applicable Regulations for Airplanes and Rotorcraft. See appendix 3 of this AC, paragraph 2 for a list of some of the regulations that may be applicable for oil projects. Additional guidance on some airworthiness standards follow. The following list is by no means exclusive, and is provided as a recommended starting point only.
Applicants should therefore, obtain from the E&PD as the FAA’s lubricating oil focal point, and the appropriate airplane directorate, guidance on regulations with which they will need to show compliance.
(1) Applicants should show that the oil is compatible with aircraft or propeller systems that use the oil (see §§ 25.901(d), 25.903, 25.903(f), 25.905, 25.943, 25.1011(b),
25.1019, 23.901(e), 23.901(f), 23.903(b)(2), 23.905(d), 23.909, 27.903, and 29.903).
(2) Applicants should show that the oi l has no adverse effect on engine cooling (see §§ 25.1041, 25.1043, 25.1045, 23.1041, 23.1043, 23.1045, 23.1047, 27.1041,
27.1043, 27.1045, 29.1041, 29.1043, 29.1045, 29.1047, and 29.1049).
Peter A. White Acting Manager, Engine and Propeller Directorate
Appendix 1 A1-1 APPENDIX 1
HORIZONTALLY OPPOSED RECIPROCATING ENGINE OIL APPROVALS:
THE SAE J1899 PROGRAM
1. Introduction . This appendix provides guidance for oil qualification programs performed in accordance with SAE standard J1899, “Lubricating Oil, Aircraft Piston Engine (Ashless Dispersant).” This appendix provides guidance specific to SAE J1899 qualified piston engine lubricating oils. It applies only to Teledyne Continental Motors (TCM) and Lycoming Engines (LE) horizontally opposed reciprocating engines.
2. Background.
a. This appendix applies to a single engine model or a family of engine models if the applicant can show that the tested engine represents the most severe case. The costs associated with such a substantiation program are prohibitive for single reciprocating engine models; therefore, a broader applicability for lubricating oil approvals is required for these engines.
b. The Naval Air Warfare Center (NAWC) developed a standardized procedure to qualify a particular engine oil across engine models, based on similarities of materials and design operating parameters. Today, this procedure applies only to horizontally opposed reciprocating engines manufactured by TCM and LE.
c. The NAWC’s procedure is captured in SAE standard J1899. It provides specific requirements for laboratory testing, engine bench testing, and engine flight testing. It represents an acceptable method of showing the FAA that applicable airworthiness certification standards are retained when the oil is used.
3. FAA Oversight of SAE J1899 Qualification Program . The SAE J1899 qualification program consists of: Step 1—all laboratory analysis and testing and engine endurance testing; and Step 2—flight testing of the oil using the specified engine model.
The SAE technical team, comprised of the oil manufacturer, engine manufacturers, the FAA, and the U.S. Navy, oversees both steps. Under Step 1, applicants conduct sufficient testing and analysis to obtain an STC which approves the use of the oil for flight testing on designated TCM and LE engines in Step 2. Step 1 requires direct FAA participation. Step 2 relies on delegated oversight performed by the engine manufacturers under their design change approval system. An overview of each step is provided below.
a. Step 1: Preliminary Data and Ground Testing .
(1) The objective of this step is to provide proof of compliance to obtain a supplemental type certificate that authorizes flight testing of the LE and TCM engine models specified in SAE J1899. For this step, applicants should submit a compliance plan to the E&PD which identifies the applicable regulations from part 33 (or Civil Air
Appendix 1 A1-2 Regulation (CAR) 13). The applicant should also provide the FAA with analyses, data, test plans and test reports to demonstrate compliance with each regulation.
(2) The first step consists of providi ng all preliminary data, laboratory testing, and evaluation; the L-38 engine test; and the 150-hour engine endurance test of a Lycoming TIO-540 engine. The applicant must perform these tests in accordance with SAE J1899.
(3) The compliance plan should reference the applicable J1899 sections. The following table summarizes the relationship between J1899 and part 33; applicants can use it to aid in developing their compliance plan.
Table A-1. Relationship between J1899 and Part 33
CFR Section Subject Comments J1899 Reference
33.7 Engine operating limitations Oil specification reference defined.
3.
33.15 Materials Data from L-38 engine test, and any other laboratory data related to materials compatibility.
3.8.1
33.39 Lubrication system Anal yses and test data to confirm the lube system operates properly with the new oil.
3.
33.42 General (block tests) Break-in, oil consumption, and pre-and post-test calibration runs, 150 hour endurance test.
3.8.2, appendix B
33.45 Calibration tests Break-in, oil consumption, and pre-and post-test calibration runs.
3.8.2, B6.2, B6.3, B6.4, B6.6
33.49 Endurance test 150 hour endurance test. 3.8.2, B6.5
33.55 Teardown inspection Post-test inspection requirements.
3.8.2, B7
For engines certified under CAR 13, applicants should reference the equivalent requirement from that regulation.
(4) Some differences exist between § 33.49 and the J1899 endurance test of section B6.5. For example, J1899 B6.5 does not require that the engine be operated at critical and 8000 ft. altitudes, as required by § 33.49(e)(1)(ii), and does not require that accessories be loaded, as required by § 33.49(a). Also, the turbo supercharger 50-hour test specified in § 33.49(e)(1)(iii) is not included in the J1899 test. However, the J1899
Appendix 1 A1-3 B6.5 test is acceptable to show that the engine oil or additive is acceptable for the limited flight test to be performed in Step 2.
(5) The 150-hour endurance test spec ified in J1899 B6.5 is considered an official FAA test and, therefore, subject to FAA certification test requirements. These include conformity of the test lubricant or additive, conformity of the test hardware and apparatus, and FAA testing oversight. Applicants should submit a test plan for approval, and the cognizant FAA ACO should issue a Test Inspection Authorization, prior to conducting the tests.
(6) Upon completion of the above requ irements, the FAA will issue an STC to authorize flight testing of the specified LE and TCM engine models in accordance with appendix C of SAE J1899.
b. Step 2: Flight Testing .
(1) Flight evaluation is the second st ep, using the specified LE and TCM engine models, as described in SAE J1899, appendix C. In this step, the applicant should conduct a long duration flight test of 500 hours on both LE and TCM engines.
(2) The FAA has delegated oversight of these tests to the engine manufacturers under their design approval holder (DAH) authority. Test conformity and procedure requirements need only meet the engine manufacturer’s requirements for a design change. Although the company designated engineering representative is responsible for FAA oversight, the FAA retains the authority to observe the testing or review the engine manufacturer’s approval of the product, if necessary. The applicant should ensure that the engine manufacturer is participating in the evaluation of the oil and has access to sufficient data to assess the acceptability of the product.
(3) Step 2 allows the SAE technical team to complete the evaluation of the oil.
Once completed, the team will determine if the oil should be added to the U.S. Navy’s QPL. Engine manufacturer approval of the product is accomplished by reference to the QPL in LE and TCM service documents.
Appendix 2 A2-1 APPENDIX 2
APPLICABLE AIRWORTHINESS STANDARDS - ENGINES
The following sections from 14 CFR part 33 and TSO C77b may aid applicants in developing their compliance plans. This list is by no means all inclusive. Applicants should, therefore, work with their assigned ACOs and the E&PD to develop their individual compliance plans.
1. Fuel Approval for Turbine Engines.
§ 33.4 Instructions for Continued Airworthiness § 33.5 Instruction manual for inst alling and operating the engine § 33.7 Engine ratings and operating limitations § 33.15 Materials § 33.17 Fire prevention § 33.19 Durability § 33.21 Engine cooling § 33.28 Engine control systems § 33.65 Surge and stall characteristics § 33.67 Fuel system § 33.72 Hydraulic actuating systems § 33.73 Power or thrust response § 33.82 General § 33.85 Calibration tests § 33.87 Endurance test § 33.89 Operation test § 33.91 Engine component test § 33.93 Teardown inspection § 33.99 General conduct of block tests
2. Fuel Approval for APUs (from TSO C77b).
a. Paragraph 4. MARKING, subparagraph b.(2), “Fuel type and specification.”
b. Paragraph 5, DATA RE QUIREMENTS, subparagraph (b), “TSO Technical Data.” including the following statements from this paragraph:
(1) “(4) A model specification that specifies the APU ratings and operating limitations established when demonstrating compliance with the requirements of this TSO.”
(2) “(5) Manual(s) that contain inst ructions for installing and operating the APU.”
Appendix 2 A2-2
(3) “(6) Manual(s) containing instruct ions for continued airworthiness of the APU.”
c. Appendix 1 (Performance Standards). The following sections apply:
4.2 Materials
4.4 Operating characteristics
4.5 APU Control System
5.2 Fire prevention
5.5 Fuel system
5.7 Cooling
6.1 General (Block Tests)
6.2 Calibration tests
6.3 Endurance test
6.4 Teardown Inspection
6.9 Electronic Control Components
3. Fuel Approval for Reciprocating Engines.
§ 33.4 Instructions for Continued Airworthiness § 33.5 Instruction manual for inst alling and operating the engine § 33.7 Engine ratings and operating limitations § 33.15 Materials § 33.17 Fire prevention § 33.19 Durability § 33.21 Engine cooling § 33.28 Engine control systems § 33.35 Fuel and induction system § 33.43 Vibration test § 33.45 Calibration test § 33.47 Detonation test § 33.49 Endurance test § 33.51 Operation test § 33.53 Engine component test § 33.55 Teardown inspection § 33.57 General conduct of block tests
4. Oil Approval for Turbine Engines.
§ 33.4 Instructions for C ontinued Airworthiness § 33.5 Instruction manual for inst alling and operating the engine § 33.7 Engine ratings and operating limitations § 33.15 Materials § 33.17 Fire prevention
Appendix 2 A2-3
§ 33.19 Durability § 33.21 Engine cooling § 33.71 Lubrication system § 33.72 Hydraulic actuating systems § 33.82 General § 33.85 Calibration tests § 33.87 Endurance test § 33.91 Engine component test § 33.93 Teardown inspection § 33.99 General conduct of block tests
5. Oil Approval for APUs (from TSO C77b).
a. Paragraph 4. MARKING, subparagraph (b ), including “(3) Lubricating oil type and specification.”
b. Paragraph 5, DATA RE QUIREMENTS, subparagraph (b), “TSO Technical Data,” including the following statements from this paragraph:
(1) “(4) A model specification that specifies the APU ratings and operating limitations established when demonstrating compliance with the requirements of this TSO.”
(2) “(5) Manual(s) that contain inst ructions for installing and operating the APU.”
(3) “(6) Manual(s) containing instruct ions for continued airworthiness of the APU.”
c. Appendix 1 (Performance Standards). The following sections apply:
4.2 Materials
4.4 Operating characteristics
4.7 Extreme attitude operation
5.2 Fire prevention
5.4 Lubrication system
5.7 Cooling
6.1 General (Block Tests)
6.2 Calibration tests
6.3 Endurance test
6.4 Teardown Inspection
6.9 Electronic Control Components
Appendix 2 A2-4
6. Oil Approval for Reciprocating Engines.
§ 33.4 Instructions for Continued Airworthiness § 33.5 Instruction manual for inst alling and operating the engine § 33.7 Engine ratings and operating limitations § 33.15 Materials § 33.17 Fire prevention § 33.19 Durability § 33.21 Engine cooling § 33.39 Lubrication system § 33.42 General § 33.45 Calibration tests § 33.49 Endurance test § 33.53 Engine component test § 33.55 Teardown inspection § 33.57 General conduct of block tests