40 CFR § 1031.90 - Supersonic engines.

---
identifier: "/us/cfr/t40/s1031.90"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 1031.90 - Supersonic engines."
title_number: 40
title_name: "Protection of Environment"
section_number: "1031.90"
section_name: "Supersonic engines."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "U"
subchapter_name: "AIR POLLUTION CONTROLS"
part_number: "1031"
part_name: "CONTROL OF AIR POLLUTION FROM AIRCRAFT ENGINES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401-7671q."
regulatory_source: "87 FR 72351, Nov. 23, 2022, unless otherwise noted."
cfr_part: "1031"
---


# 1031.90 Supersonic engines.

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:

SN = 83.6·rO<sub>−</sub>
<sup>0.274</sup>

(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:

HC = 140·0.92
<sup>rPR</sup>

(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:

CO = 4550·rPR<sub>−1.03</sub>

(e) *NO*<sub>X</sub> 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 NO<sub>X</sub> engines exceeding the following emission standard in g/kN rated output:

NO<sub>X</sub> = 36+2.42·rPR