14 CFR § 25.1517 - Rough air speed, V

---
identifier: "/us/cfr/t14/s25.1517"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "14 CFR § 25.1517 - Rough air speed, V"
title_number: 14
title_name: "Aeronautics and Space"
section_number: "25.1517"
section_name: "Rough air speed, V"
chapter_name: "FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION"
subchapter_number: "C"
subchapter_name: "AIRCRAFT"
part_number: "25"
part_name: "AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "49 U.S.C. 106(f), 106(g), 40113, 44701, 44702 and 44704; Pub. L. 115-254, 132 Stat 3281 (49 U.S.C. 44903 note)."
regulatory_source: "Docket No. 5066, 29 FR 18291, Dec. 24, 1964, unless otherwise noted."
cfr_part: "25"
---


# 25.1517 Rough air speed, V

(a) A rough air speed, V<sub>RA,</sub> for use as the recommended turbulence penetration airspeed, and a rough air Mach number, M<sub>RA</sub>, for use as the recommended turbulence penetration Mach number, must be established. V<sub>RA</sub>/M<sub>RA</sub> must be sufficiently less than V<sub>MO</sub>/M<sub>MO</sub> to ensure that likely speed variation during rough air encounters will not cause the overspeed warning to operate too frequently.

(b) At altitudes where V<sub>MO</sub> is not limited by Mach number, in the absence of a rational investigation substantiating the use of other values, V<sub>RA</sub> must be less than V<sub>MO</sub> minus 35 KTAS.

(c) At altitudes where V<sub>MO</sub> is limited by Mach number, M<sub>RA</sub> may be chosen to provide an optimum margin between low and high speed buffet boundaries.

[Amdt. 25-141, 79 FR 73469, Dec. 11, 2014, as amended by FAA-2022-1355; Amdt. No. 25-148, 87 FR 75710, Dec. 9, 2022; 88 FR 2813, Jan. 18, 2023]