A gust lock is a mechanical ground safety system that prevents control surface movement while the aircraft is stationary. The device blocks wind-induced motion in ailerons, rudder and elevator linkages when the aircraft is parked. Because the control column is unpowered on the ground, a gust keeps surfaces neutral and trailing-edge-down, shielding them from jet blast, propeller wash or any gust. In doing so, it stops swinging back and avoids damage to both the surfaces and the control system.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is a gust lock on an airplane?
A gust lock on an airplane is a mechanical ground safety system that locks the flight controls as their linkages reach the locking position and locks the door in place when it is fully opened. The device prevents damage to the control surfaces and the control system from gusts striking the airplane while it is on the ground or water. It protects unpowered flight control surfaces from movement by wind gusts while the aircraft is on the ground, and keeps open aircraft doors in place while the aircraft is parked and non-operational.
The system neither affects the flight performance of the aircraft nor receives any flight loads. A small metal bar fixes the yoke so the yoke cannot move left/right or forward/back; by association the ailerons and elevator cannot move either. External gust locks use leverage between a fixed surface and the movable control surface. The device is a strap, a tensioner of some type, a loop, and a hook, while many internal locks on commercial aircraft use a pin on the yoke.
The gust lock for the Gulfstream IV provides a means for the flight crew to manually protect the unpowered flight control surfaces and is effective in protecting the flight controls in wind gusts up to 60 knots. Moving the ailerons and rudder to the neutral position and the elevator to the trailing-edge-down position allows the lock to engage. A gust lock lever located on the cockpit center pedestal operates mechanical latches that lock the ailerons, elevators, and rudder against gust loads. The lever is routinely set whenever the aircraft is parked.
The device must automatically disengage when the pilot operates the primary flight controls in a normal manner and must limit the operation of the airplane so that the pilot receives a warning at the start of takeoff. It must have means to preclude inadvertent engagement in flight. The FAA regulation requires such devices to prevent damage to the control surfaces and control system when the airplane is on the ground or water. When no gust lock is fitted the door opens with such force that it swings straight back and blocks the exit, preventing people from evacuating.
