Definition
External or internal devices fitted to the rudder to hold it stationary while the airplane is parked, preventing wind gusts from slamming the control surface back and forth and damaging the rudder, hinges, or linked control system components.
Plain English
Clamps or pins that stop the rudder from flapping in the wind when the airplane is sitting on the ground.
Context Anchor
Encountered during shutdown, parking, tie-down, and preflight inspection, especially when checking that all control locks have been removed before flight.
Derivation
A 'gust' is a sudden burst of wind, and a 'lock' here means a device that holds something in place. Together the term describes a lock that protects against gusts. Knowing this makes the purpose obvious: it locks the rudder so a gust cannot move it.
Why Pilots Care
Unsecured rudders can be damaged or cause stress to the tail structure during high winds or gusty conditions on the ground.
Intuition Check
Do not think of rudder gust locks as flight-control help. They are parking and securing devices, and they must be removed or released before flight.
Example Sentence 1
After shutdown, the pilot installed the rudder gust locks before walking away from the airplane.
Example Sentence 2
During the preflight walk-around, the pilot removed all gust locks including the one on the rudder before starting the engine.