Definition
A failure of the landing gear system to operate as designed, including failure to extend, failure to retract, partial extension, asymmetric extension, unsafe indication, or collapse on touchdown. Causes can be mechanical (broken linkages, hydraulic loss, electrical failure), procedural (mis-selected position, circuit breaker tripped), or environmental (ice, debris in the wells).
Plain English
Something has gone wrong with the wheels-and-struts system that lowers and locks the gear for landing. The gear may not come down, may not lock down, may not retract, or may not show a safe indication in the cockpit.
Context Anchor
Encountered during gear extension or retraction, especially before landing when the pilot checks that the landing gear is down and locked.
Derivation
Malfunction comes from mal-, meaning bad or improper, and function, meaning to work or perform. That matters here because a landing gear malfunction does not always mean the gear has completely failed; it means some part of the system is not working as it should.
Why Pilots Care
A landing gear malfunction forces an emergency landing procedure that can damage the airplane and increase the risk of injury if not handled with the correct checklist.
Grounding Statement
If the pilot selects the gear down and does not get a normal down-and-locked indication, the situation must be treated as a possible landing gear malfunction until resolved.
Intuition Check
Do not assume a landing gear malfunction means the gear has collapsed or is completely broken. It can also be a warning light problem, a gear door problem, or gear that is down but not confirmed locked.
Example Sentence 1
After selecting gear down on final, the pilot saw two green lights and one red, indicating a landing gear malfunction on the right main.
Example Sentence 2
The instructor simulated a landing gear malfunction by disabling the gear motor so the student could practice the emergency procedure.