Definition
A condition in which one or more flight or engine instruments stop providing accurate information, either by ceasing to function entirely or by displaying erroneous indications. Failures may be caused by loss of power, blocked sensing ports, gyro spin-down, electrical or vacuum system problems, or internal mechanical faults. In instrument flight, a failure can be partial (one instrument affected) or total (a whole system, such as the pitot-static or vacuum system, lost), and recognizing the failure quickly is essential to maintaining control by reference to remaining reliable instruments.
Plain English
When a cockpit instrument stops working or starts giving wrong readings, so the pilot can't trust what it shows.
Context Anchor
Seen in instrument flying and unusual attitude recovery discussions, where the pilot may need to control the airplane using the remaining reliable instruments.
Why Pilots Care
An undetected instrument failure can lead the pilot to make control inputs based on false information, which in cloud or at night can quickly result in loss of control. Recognizing the failure, identifying which instruments are still reliable, and flying partial panel are core instrument-rated skills.
Intuition Check
Do not assume instrument failure always means a blank or broken display. An instrument can fail by giving information that looks normal but is wrong.
Example Sentence 1
When the attitude indicator began drifting during the climb, the pilot suspected a vacuum-driven instrument failure and cross-checked with the turn coordinator and altimeter.
Example Sentence 2
Training for instrument failure helps the pilot maintain control using backup instruments and outside references when available.