Definition
A flight condition in a multi-engine airplane in which one engine has failed or has been intentionally shut down, while the remaining engine or engines continue to produce power. Many multi-engine performance figures and V-speeds (such as VMC, VYSE, and VXSE) are defined specifically for this condition.
Plain English
One of the airplane's engines has stopped working, and the airplane is flying on the engine or engines that are still running.
Context Anchor
Seen in multiengine training, emergency procedures, and V-speed discussions about how the airplane performs and handles after one engine stops helping.
Derivation
Plain English: 'inoperative' comes from the Latin 'operari' (to work) with the prefix 'in-' meaning 'not.' So one-engine-inoperative literally means 'one engine not working.' The hyphenated form is used as a single descriptor for a specific flight condition.
Why Pilots Care
Determines critical speeds and climb capability that pilots must know to maintain control and reach a safe altitude after an engine failure.
Grounding Statement
Picture a twin-engine airplane after one engine quits: the airplane can still fly, but it no longer has equal help from both sides.
Intuition Check
Do not assume one-engine-inoperative always means the engine is physically stopped. It means one engine is not providing usable power for flight.
Example Sentence 1
The pilot reviewed the one-engine-inoperative climb performance before departing from the high-altitude airport.
Example Sentence 2
The takeoff briefing always includes the one-engine-inoperative procedure for runway 27.