---
kind: "section"
citation: "40 C.F.R. § 1031.90"
title: "40"
number: "1031.90"
heading: "Supersonic engines."
url: "https://uscodex.org/cfr/40/1031.90"
---

# §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:
- (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) **NO—** X 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:

## Notes

### Authority

Authority: 42 U.S.C. 7401-7671q.

### Source

Source: 87 FR 72351, Nov. 23, 2022, unless otherwise noted.