(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.