Regulation Text
For an airplane subject to § 91.801(c) of this subpart and otherwise prohibited from operation to or from an airport in the contiguous United States by § 91.855, any person may apply for a special flight authorization for that airplane to operate in the contiguous United States for the purpose of obtaining modifications to meet Stage 3, Stage 4, or Stage 5 noise levels.
[Docket FAA-2015-3782, Amdt. 91-349, 82 FR 46132, Oct. 4, 2017]
Research Notes
Section 91.859 — Modification to meet Stage 3 noise levels — addressed the engineering modifications (hush kits, engine replacements) used to bring Stage 2 aircraft into Stage 3 compliance during the phase-out.
Hush kits: Acoustic modifications applied to older engines (notably JT8D on 727/737 and DC-9) to reduce takeoff and approach noise. Hush-kitted aircraft achieved Stage 3 compliance and remained in service. Many cargo operators used hush-kitted 727s into the 2010s.
Reference: AC 25-7 on noise certification; specific TC supplements for hush-kit modifications.
Amendment History
Amendment History Coming Soon
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