Definition
Failures or abnormal operation of an airplane's mechanical, electrical, hydraulic, fuel, powerplant, pressurization, or avionics systems that prevent the system from functioning as designed and may require pilot action to maintain safe flight.
Plain English
Something on the airplane stops working properly, or works in a way it shouldn't. The pilot has to recognize it, decide what to do, and handle it so the flight stays safe.
Context Anchor
Seen in emergency and abnormal procedures, aircraft manuals, checklists, and training scenarios for equipment problems.
Derivation
From Latin 'mal' meaning bad and 'functio' meaning performance. A malfunction is literally a 'bad performance' -- the system is doing something, but not what it should.
Why Pilots Care
Unrecognized or mishandled system malfunctions can lead to loss of control, forced landings, or emergencies.
Intuition Check
Do not assume a system malfunction always means a complete failure or an immediate emergency. It means a system is not working normally; the seriousness depends on the system, the situation, and the pilot’s response.
Example Sentence 1
During cruise, the pilot noticed a system malfunction when the alternator warning light came on and the ammeter showed a discharge.
Example Sentence 2
Training scenarios often simulate system malfunctions during instrument approaches to build proper response habits.