Subsonic turbojet and turbofan engines at or below 26.7 kN thrust.

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: SN = 83.6·rO − 0.274 (b) [Reserved]