Definition
A partial or complete loss of normal flight control function caused by a mechanical, structural, or system problem in the airplane's control linkages, cables, hydraulics, or electronic flight control components. The pilot can no longer move one or more flight controls in the usual way, or the controls move but the corresponding control surface does not respond as expected.
Plain English
Something has broken or jammed in the system that connects the pilot's controls to the moving parts of the airplane. The pilot pushes, pulls, or turns a control and the airplane does not respond the way it should.
Context Anchor
Encountered in emergency discussions when an airplane does not respond normally to control inputs, or when a control feels stuck, loose, limited, or abnormal.
Derivation
“Control” comes from older words meaning to check or govern something. “Failure” means not performing the required function. In aviation, the phrase points to a system that is supposed to let the pilot govern the airplane’s movement but is no longer doing that normally.
Why Pilots Care
It reduces or removes the pilot's ability to maneuver the aircraft, requiring immediate use of emergency procedures to maintain control and land safely.
Intuition Check
Do not assume a control system failure always means all controls are lost. It may affect only one control, or it may make a control stiff, loose, jammed, or only partly effective.
Example Sentence 1
After hearing a snap in the tail, the pilot suspected a control system failure when the elevator went slack and the airplane pitched without input.
Example Sentence 2
After takeoff the instructor simulated a control system failure to practice the emergency checklist and return to the airport.