Airplanes: Reciprocating engine-powered: En route limitations: One engine inoperative

This regulation sets minimum climb performance requirements for Part 121 reciprocating engine airplanes when one engine fails en route.

The standard rule requires the airplane to maintain a specific rate of climb with one engine inoperative, considering normal fuel and oil consumption. However, the regulation's text appears incomplete—paragraph (a) references a climb rate formula but doesn't provide it.

Alternatively, operators may use an approved procedure (paragraph (b)) that allows flight at an altitude where, after engine failure, the aircraft can continue to an alternate airport. The flight path must clear terrain and obstructions by at least 2,000 feet within five miles of track. This procedure requires:

• Reduced climb performance calculations
• Sufficient altitude to reach a predetermined alternate
• Meeting standard climb requirements at 1,000 feet above the alternate
• Accounting for adverse winds and temperatures
• An approved alternate airport specified in the dispatch release

This regulation doesn't apply to large nontransport category airplanes under §121.173(c).

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*