#### § 34.23 Exhaust Emission Standards for Engines Manufactured on and after July 18, 2012.

The standards of this section apply to aircraft engines manufactured on and after July 18, 2012, unless otherwise exempted or excepted. Where a gaseous emission standard is specified by a formula, calculate and round the standard to three significant figures or to the nearest 0.1 g/kN (for standards at or above 100 g/kN). Where a smoke standard is specified by a formula, calculate and round the standard to the nearest 0.1 SN. 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, as described in [§ 34.60](/on/2024-09-19/title-14/section-34.60).

(a) Gaseous exhaust emissions from each new aircraft gas turbine engine shall not exceed:

(1) [Reserved]

(2) Except as provided in [§§ 34.9(b)](/on/2024-09-19/title-14/section-34.9#p-34.9(b)) and [34.21(c)](/on/2024-09-19/title-14/section-34.21#p-34.21(c)), for Classes TF, T3 and T8 engines manufactured on and after July 18, 2012, and for which the first individual production model was manufactured on or before December 31, 2013 (Tier 6):

Tier 6 Oxides of Nitrogen Emission Standards for Subsonic Engines

| Class | Rated pressure ratio—rPR | Rated output rO (kN) | NOX (g/kN) |
| --- | --- | --- | --- |
| TF, T3, T8 | rPR ≤ 30 | 26.7 < rO ≤ 89.0 | 38.5486 + 1.6823 (rPR) − 0.2453 (rO) − (0.00308 (rPR) (rO)). |
| | | rO > 89.0 | 16.72 + 1.4080 (rPR). |
| | 30 < rPR < 82.6 | 26.7 < rO ≤ 89.0 | 46.1600 + 1.4286 (rPR) − 0.5303 (rO) + (0.00642 (rPR) (rO)). |
| | | rO > 89.0 | −1.04 + 2.0 (rPR). |
| | rPR ≥ 82.6 | rO *≥* 26.7 | 32 + 1.6 (rPR). |

(3) Engines exempted from [paragraph (a)(2)](/on/2024-09-19/title-14/section-34.23#p-34.23(a)(2)) of this section produced on or before December 31, 2016 must be labeled “EXEMPT NEW” in accordance with [§ 45.13 of this chapter](/on/2024-09-19/title-14/section-45.13). No exemptions to the requirements of [paragraph (a)(2)](/on/2024-09-19/title-14/section-34.23#p-34.23(a)(2)) of this section will be granted after December 31, 2016.

(4) For Class TSS Engines manufactured on and after July 18, 2012:

Gaseous Emission Standards for Supersonic Engines

| Class | Rated output rO1 (kN) | NOX (g/kN) | CO (g/kN) |
| --- | --- | --- | --- |
| TSS | All | 36 + 2.42 (rPR) | 4,550 (rPR)−1.03 |
| | | | |
| --- | --- | --- | --- |
| 1 rO is the rated output with afterburning applied. | | | |

(b) Gaseous exhaust emissions from each new aircraft gas turbine engine shall not exceed:

(1) For Classes TF, T3 and T8 engines of a type or model of which the first individual production model was manufactured after December 31, 2013 (Tier 8):

Tier 8 Oxides of Nitrogen Emission Standards for Subsonic Engines

| Class | Rated pressure ratio—rPR | Rated output rO (kN) | NOX (g/kN) |
| --- | --- | --- | --- |
| TF, T3, T8 | rPR ≤ 30 | 26.7 < rO ≤ 89.0 | 40.052 + 1.5681 (rPR) − 0.3615 (rO) − (0.0018 (rPR) (rO)). |
| | | rO > 89.0 | 7.88 + 1.4080 (rPR). |
| | 30 < rPR < 104.7 | 26.7 < rO ≤ 89.0 | 41.9435 + 1.505 (rPR) − 0.5823 (rO) + (0.005562 (rPR) (rO)). |
| | | rO > 89.0 | −9.88 + 2.0 (rPR). |
| | rPR ≥ 104.7 | rO ≥ 26.7 | 32 + 1.6 (rPR). |

(c) Engines (including engines that are determined to be derivative engines for the purposes of emission certification) type certificated with characteristic levels at or below the NOX standards of [§ 34.21(d)(1)(vi) of this part](/on/2024-09-19/title-14/part-34/section-34.21#p-34.21(d)(1)(vi)) (as applicable based on rated output and rated pressure ratio) and introduced before July 18, 2012, may be produced through December 31, 2012, without meeting the NOX standard of [paragraph (a)(2)](/on/2024-09-19/title-14/section-34.23#p-34.23(a)(2)) of this section.

[Doc. No. 34-5, [77 FR 76851](https://www.federalregister.gov/citation/77-FR-76851), Dec. 31, 2012, as amended by Amdt. 34-5A, [78 FR 63017](https://www.federalregister.gov/citation/78-FR-63017), Oct. 23, 2013; [78 FR 65554](https://www.federalregister.gov/citation/78-FR-65554), Nov. 1, 2013; Amdt. No. 34-7, [89 FR 31087](https://www.federalregister.gov/citation/89-FR-31087), Apr. 24, 2024]