(a) Overview of standards. Standards apply to different types and sizes of aircraft engines as described in §§ 1031.40 through 1031.90. All new engines and some in-use engines are subject to smoke standards (either based on smoke number or nvPM mass concentration). Some new engines are also subject to standards for gaseous emissions (HC, CO, and NOX) and nvPM (mass and number).

(1) Where there are multiple tiers of standards for a given pollutant, the named tier generally corresponds to the meeting of the International Civil Aviation Organization's (ICAO's) Committee on Aviation Environmental Protection (CAEP) at which the standards were agreed to internationally. Other standards are named Tier 0, Tier 1, or have names that describe the standards.

(2) Where a standard is specified by a formula, determine the level of the standard as follows:

(i) For smoke number standards, calculate and round the standard to the nearest 0.1 smoke number.

(ii) For maximum nvPM mass concentration standards, calculate and round the standard to the nearest 1 µg/m 3.

(iii) For LTO nvPM mass standards, calculate and round the standard to three significant figures.

(iv) For LTO nvPM number standards calculate and round the standard to three significant figures.

(v) For gaseous emission standards, calculate and round the standard to three significant figures, or to the nearest 0.1 g/kN for turbojet and turbofan standards at or above 100 g/kN.

(3) Perform tests using the procedures specified in § 1031.140 to measure emissions for comparing to the standard. Engines comply with an applicable standard if test results show that the engine type certificate family's characteristic level does not exceed the numerical level of that standard.

(4) Engines that are covered by the same type certificate and are determined to be derivative engines for emissions certification purposes under the requirements of § 1031.130 are subject to the emission standards of the previously certified engine. Otherwise, the engine is subject to the emission standards that apply to a new engine type.

(b) Fuel venting. (1) The fuel venting standard in paragraph (b)(2) of this section applies to new subsonic and supersonic aircraft engines subject to this part. This fuel venting standard also applies to the following in-use engines:

(i) Turbojet and turbofan engines with rated output at or above 36 kN thrust manufactured after February 1, 1974.

(ii) Turbojet and turbofan engines with rated output below 36 kN thrust manufactured after January 1, 1975.

(iii) Turboprop engines manufactured after January 1, 1975.

(2) Engines may not discharge liquid fuel emissions into the atmosphere. This standard is directed at eliminating intentional discharge of liquid fuel drained from fuel nozzle manifolds after engines are shut down and does not apply to normal fuel seepage from shaft seals, joints, and fittings. Certification for the fuel venting standard will be based on an inspection of the method designed to eliminate these emissions.

The following standards apply to turboprop engines with rated output at or above 1,000 kW:

(a) Smoke. Engines of a type or model for which the date of manufacture of the individual engine is on or after January 1, 1984, may not have a characteristic level for smoke number exceeding the following value:

(b) [Reserved]

The following standards apply to new turbofan or turbojet aircraft engines with rated output at or below 26.7 kN thrust that are installed in subsonic aircraft:

(a) Smoke. Engines of a type or model for which the date of manufacture of the individual engine is on or after August 9, 1985 may not have a characteristic level for smoke number exceeding the lesser of 50 or the following value:

(b) [Reserved]

The following standards apply to new turbofan or turbojet aircraft engines with rated output above 26.7 kN thrust that are installed in subsonic aircraft:

(a) Smoke. (1) Tier 0. Except as specified in (a)(2) of this section, engines of a type or model with rated output at or above 129 kN, and for which the date of manufacture of the individual engine after January 1, 1976 and is before January 1, 1984 may not have a characteristic level for smoke number exceeding the following emission standard:

(2) JT8D and JT3D engines. (i) Engines of the type JT8D for which the date of manufacture of the individual engine is on or after February 1, 1974, and before January 1, 1984 may not have a characteristic level for smoke number exceeding an emission standard of 30.

(ii) Engines of the type JT3D for which the date of manufacture of the individual engine is on or after January 1, 1978 and before January 1, 1984 may not have a characteristic level for smoke number exceeding an emission standard of 25.

(3) Tier 0 in-use. Except for engines of the type JT8D and JT3D, in-use engines with rated output at or above 129 kN thrust may not exceed the following smoke number standard:

(4) JT8D in-use. In-use aircraft engines of the type JT8D may not exceed a smoke number standard of 30.

(5) Tier 1. Engines of a type or model for which the date of manufacture of the individual engine is on or after January 1, 1984 and before January 1, 2023 may not have a characteristic level for smoke number exceeding an emission standard that is the lesser of 50 or the following:

(6) Tier 10. Engines of a type or model for which the date of manufacture of the individual engine is on or after January 1, 2023 may not have a characteristic level for the maximum nvPM mass concentration in µg/m 3 exceeding the following emission standard:

(b) LTO nvPM mass and number. An engine's characteristic level for nvPM mass and nvPM number may not exceed emission standards as follows:

(1) Tier 11 new type. The following emission standards apply to engines of a type or model for which an application for original type certification is submitted on or after January 1, 2023 and for engines covered by an earlier type certificate if they do not qualify as derivative engines for emission purposes as described in § 1031.130:

(2) Tier 11 in-production. The following emission standards apply to engines of a type or model for which the date of manufacture of the individual engine is on or after January 1, 2023:

(c) HC. Engines of a type or model for which the date of manufacture of the individual engine is on or after January 1, 1984, may not have a characteristic level for HC exceeding an emission standard of 19.6 g/kN.

(d) CO. Engines of a type or model for which the date of manufacture of the individual engine is on or after July 7, 1997, may not have a characteristic level for CO exceeding an emission standard of 118 g/kN.

(e) NOX. An engine's characteristic level for NOX may not exceed emission standards as follows:

(1) Tier 0. The following NOX emission standards apply to engines of a type or model for which the date of manufacture of the first individual production model was on or before December 31, 1995, and for which the date of manufacture of the individual engine was on or after December 31, 1999, and before December 31, 2003:

(2) Tier 2. The following NOX emission standards apply to engines of a type or model for which the date of manufacture of the first individual production model was after December 31, 1995, or for which the date of manufacture of the individual engine was on or after December 31, 1999, and before December 31, 2003:

(3) Tier 4 new type. The following NOX emission standards apply to engines of a type or model for which the date of manufacture of the first individual production model was after December 31, 2003, and before July 18, 2012:

(4) Tier 6 in-production. The following NOX emission standards apply to engines of a type or model for which the date of manufacture of the individual engine is on or after July 18, 2012:

(5) Tier 8 new type. The following NOX standards apply to engines of a type or model for which the date of manufacture of the first individual production model was on or after January 1, 2014; or for which an application for original type certification is submitted on or after January 1, 2023; or for engines covered by an earlier type certificate if they do not qualify as derivative engines for emission purposes as described in § 1031.130:

The following standards apply to new engines installed in supersonic airplanes:

(a) Smoke. Engines of a type or model for which the date of manufacture was on or after January 1, 1984, may not have a characteristic level for smoke number exceeding an emission standard that is the lesser of 50 or the following:

(b) [Reserved]

(c) HC. Engines of a type or model for which the date of manufacture was on or after January 1, 1984, may not have a characteristic level for HC exceeding the following emission standard in g/kN rated output:

(d) CO. Engines of a type or model for which the date of manufacture was on or after July 18, 2012, may not have a characteristic level for CO exceeding the following emission standard in g/kN rated output:

(e) NOX Engines of a type or model for which the date of manufacture was on or after July 18, 2012, may not have a characteristic level for NOX engines exceeding the following emission standard in g/kN rated output:

(a) Overview. For purposes of compliance with exhaust emission standards of this part, a type certificate applicant may request from the FAA a determination that an engine configuration be considered a derivative engine for emissions certification purposes. The applicant must demonstrate that the configuration is derived from and similar in type design to an engine that has a type certificate issued in accordance with 14 CFR part 33, and at least one of the following circumstances applies:

(1) The FAA determines that a safety issue requires an engine modification.

(2) All regulated emissions from the proposed derivative engine are lower than the corresponding emissions from the previously certificated engine.

(3) The FAA determines that the proposed derivative engine's emissions are similar to the previously certificated engine's emissions as described in paragraph (c) of this section.

(b) Determining emission rates. To determine new emission rates for a derivative engine for demonstrating compliance with emission standards under § 1031.30(a)(4) and for showing emissions similarity in paragraph (c) of this section, testing may not be required in all situations. If the previously certificated engine model or any associated sub-models have a characteristic level before modification that is at or above 95% of any applicable standard for smoke number, HC, CO, or NOX or at or above 80% of any applicable nvPM standard, you must test the proposed derivative engine. Otherwise, you may use engineering analysis to determine the new emission rates, consistent with good engineering judgment. The engineering analysis must address all modifications from the previously certificated engine, including those approved for previous derivative engines.

(c) Emissions similarity. (1) A proposed derivative engine's emissions are similar to the previously certificated engine's emissions if the type certificate applicant demonstrates that the engine meets the applicable emission standards and differ from the previously certificated engine's emissions only within the following ranges:

(i) ±3.0 g/kN for NOX.

(ii) ±1.0 g/kN for HC.

(iii) ±5.0 g/kN for CO.

(iv) ±2.0 SN for smoke number.

(v) The following values apply for nvPMMC:

(A) ±200 µg/m 3 if the characteristic level of maximum nvPMMC is below 1,000 µg/m 3.

(B) ±20% of the characteristic level if the characteristic level for maximum nvPMMC is at or above 1,000 µg/m 3.

(vi) The following values apply for nvPMmass:

(A) 80 mg/kN if the characteristic level for nvPMmass emissions is below 400 mg/kN.

(B) ±20% of the characteristic level if the characteristic level for nvPMmass emissions is greater than or equal to 400 mg/kN.

(vii) The following values apply for nvPMnum:

(A) 4 × 10 14 particles/kN if the characteristic level for nvPMnum emissions is below 2 × 10 15 particles/kN.

(B) ±20% of the characteristic level if the characteristic level for nvPMnum emissions is greater than or equal to 2×10 15 particles/kN.

(2) In unusual circumstances, the FAA may, for individual certification applications, adjust the ranges beyond those specified in paragraph (c)(1) of this section to evaluate a proposed derivative engine, consistent with good engineering judgment.

(a) Overview. Measure emissions using the equipment, procedures, and test fuel specified in Appendices 1 through 8 of ICAO Annex 16 (incorporated by reference, see § 1031.210) as described in this section (referenced in this section as “ICAO Appendix #”). For turboprop engines, use the procedures specified in ICAO Annex 16 for turbofan engines, consistent with good engineering judgment.

(b) Test fuel specifications. Use a test fuel meeting the specifications described in ICAO Appendix 4. The test fuel must not have additives whose purpose is to suppress smoke, such as organometallic compounds.

(c) Test conditions. Prepare test engines by including accessories that are available with production engines if they can reasonably be expected to influence emissions.

(1) The test engine may not extract shaft power or bleed service air to provide power to auxiliary gearbox-mounted components required to drive aircraft systems.

(2) Test engines must reach a steady operating temperature before the start of emission measurements.

(d) Alternate procedures. In consultation with the EPA, the FAA may approve alternate procedures for measuring emissions. This might include testing and sampling methods, analytical techniques, and equipment specifications that differ from those specified in this part. An applicant for type certification may request this approval by sending a written request with supporting justification to the FAA and to the Designated EPA Program Officer. Such a request may be approved only in the following circumstances:

(1) The engine cannot be tested using the specified procedures.

(2) The alternate procedure is shown to be equivalent to or better (e.g., more accurate or precise) than the specified procedure.

(e) LTO cycles. The following landing and take-off (LTO) cycles apply for emission testing and calculating weighted LTO values:

(f) Pollutant-specific test provisions. Use the following provisions to demonstrate whether engines meet the applicable standards:

(1) Smoke number. Use the equipment and procedures specified in ICAO Appendix 2 and ICAO Appendix 6. Test the engine at sufficient thrust settings to determine and compute the maximum smoke number across the engine operating thrust range.

(2) nvPM. Use the equipment and procedures specified in ICAO Appendix 7 and ICAO Appendix 6, as applicable:

(i) Maximum nvPM mass concentration. Test the engine at sufficient thrust settings to determine and compute the maximum nvPM mass concentration produced by the engine across the engine operating thrust range, according to the procedures of ICAO Appendix 7.

(ii) LTO nvPM mass and number. Test the engine at sufficient thrust settings to determine the engine's nvPM mass and nvPM number at the percent of rated output identified in table 1 to paragraph (e) of this section.

(3) HC, CO, and NOX. Use the equipment and procedures specified in ICAO Appendix 3, ICAO Appendix 5, and ICAO Appendix 6, as applicable. Test the engine at sufficient thrust settings to determine the engine's HC, CO, and NOX emissions at the percent of rated output identified in table 1 to paragraph (e) of this section.

(4) CO2. Calculate CO2 emission values from fuel mass flow rate measurements in ICAO Appendix 3 and ICAO Appendix 5 or, alternatively, according to the CO2 measurement criteria in ICAO Appendix 3 and ICAO Appendix 5.

(g) Characteristic level. The compliance demonstration consists of establishing a mean value from testing some number of engines, then calculating a “characteristic level” by applying a set of statistical factors in ICAO Appendix 6 that take into account the number of engines tested. Round each characteristic level to the same number of decimal places as the corresponding standard. Engines comply with an applicable standard if the testing results show that the engine type certificate family's characteristic level does not exceed the numerical level of that standard.

(h) System loss corrected nvPM emission indices. Use the equipment and procedures specified in ICAO Appendix 8, as applicable, to determine system loss corrected nvPM emission indices.