Definition
Failures or abnormal behavior of an aircraft system, instrument, or component that prevents it from operating as designed. Malfunctions can be partial (a system performing poorly or intermittently) or complete (a system failing entirely), and they may involve engines, flight controls, electrical systems, avionics, landing gear, or any other installed equipment.
Plain English
Something on the airplane stops working properly. It might quit altogether, or it might still work but not the way it should.
Context Anchor
A pilot may encounter equipment malfunctions during preflight, engine run-up, flight, landing, or while following emergency procedures.
Derivation
From Latin 'mal' (bad) and 'functio' (performance or working). A malfunction is literally a 'bad working' — the equipment is doing something, but not what it should.
Why Pilots Care
Proper recognition and response to equipment malfunctions prevents loss of control and supports safe outcomes in both training and real-world flights.
Intuition Check
Do not assume a malfunction means something has completely failed. In aviation, weak, intermittent, abnormal, or unreliable operation can also be an equipment malfunction.
Example Sentence 1
The pilot ran the appropriate checklist after noticing an equipment malfunction in the electrical system.
Example Sentence 2
Chapter 5 covers how to handle common equipment malfunctions like engine roughness or instrument failure.