Regulation Text
(a) Notwithstanding § 91.119, and except as provided in paragraph (b) of this section, no person may operate an airplane under VFR at less than—
(1) One thousand feet above the surface, or 1,000 feet from any mountain, hill, or other obstruction to flight, for day operations; and
(2) The altitudes prescribed in § 91.177, for night operations.
(b) This section does not apply—
(1) During takeoff or landing;
(2) When a different altitude is authorized by a waiver to this section under subpart J of this part; or
(3) When a flight is conducted under the special VFR weather minimums of § 91.157 with an appropriate clearance from ATC.
Research Notes
Section 91.515 — Flight altitude rules — establishes specific minimum altitude rules for large and turbine multiengine airplanes under Subpart F.
The driftdown rule: For two-engine turbine aircraft, the flight must be planned so that with one engine inoperative the aircraft can: (1) continue at an altitude at which it can comply with terrain/obstacle clearance for the route; OR (2) reach a suitable alternate at a safe altitude.
The 'engine-inoperative' planning concept: Two-engine jet operations over mountainous terrain require planning for the worst-case driftdown scenario. The aircraft might not be able to maintain cruise altitude on one engine, but it must be able to maintain enough altitude to clear terrain along an escape route to a suitable airport.
Reference: AC 25-7C; AFM Section 5 (Performance) for specific aircraft driftdown calculations.
Amendment History
Amendment History Coming Soon
Every time this regulation changes, we'll record it here — the date, what was amended, and a plain-English summary of what shifted.