Definition
Not working or not functioning. In aviation, the term refers to an instrument, system, or piece of equipment that is unserviceable, failed, or otherwise not available for use during flight or ground operations.
Plain English
It isn't working. The instrument or system is broken, failed, or out of service and cannot be relied on.
Context Anchor
Seen in preflight checks, equipment lists, instrument failure discussions, and training for flying when one or more cockpit instruments are not usable.
Derivation
From Latin 'in-' meaning 'not' and 'operari' meaning 'to work.' Literally 'not working.' The aviation use stays close to the everyday meaning but carries specific regulatory weight: an inoperative item often has rules attached about whether the aircraft can legally fly with it that way.
Why Pilots Care
Pilots must recognize inoperative instruments immediately to transition to backup references or partial-panel techniques and maintain control.
Intuition Check
Do not assume inoperative means the item is removed or unimportant. In aviation, it usually means the item is present, but it is not working or must not be used.
Example Sentence 1
The attitude indicator was inoperative, so the pilot flew the approach using partial panel techniques.
Example Sentence 2
The pilot continued the approach using backup instruments after declaring the heading indicator inoperative.