Definition
Mechanical safety devices, typically pins or sleeves, installed into the landing gear of a parked aircraft to physically prevent the gear from retracting or collapsing while the airplane is on the ground. Each ground lock carries a brightly colored streamer marked 'Remove Before Flight' so it cannot be overlooked during preflight.
Plain English
Removable pins you slide into the landing gear of a parked airplane to lock it in the down position so it can't accidentally fold up while the airplane is on the ground.
Context Anchor
Seen during preflight, postflight, maintenance, and landing gear safety checks, especially on airplanes with retractable landing gear.
Why Pilots Care
They stop the gear from accidentally retracting on the ground, which could damage the aircraft or injure people nearby.
Intuition Check
Do not think of ground locks as parking brakes, wheel chocks, or tie-downs. They do not keep the airplane from rolling; they keep the landing gear from moving when it should stay down.
Example Sentence 1
During the preflight walkaround, the pilot pulled the ground locks from each main gear and stowed them with their red streamers in the cockpit.
Example Sentence 2
During the walk-around, the mechanic confirmed both main gear ground locks were securely in place.