Definition
The configuration in which the airplane's wheels are extended and locked into the down-and-locked position, ready to support the airplane during landing, taxi, or takeoff. In retractable-gear airplanes, this is the position selected by moving the gear handle to the down position and confirmed by indicator lights or other visual and mechanical checks.
Plain English
The wheels are out and locked in place, ready for the airplane to touch down on the runway.
Context Anchor
Seen in before-landing checklists, cockpit callouts, landing-gear indications, and discussions of retractable landing gear operation.
Derivation
Gear originally meant equipment or apparatus. In aviation, landing gear means the equipment that supports the aircraft on the ground, usually wheels and their supporting parts. Down describes the extended position, as opposed to retracted or up.
Why Pilots Care
Ensures the aircraft can safely land without damaging the fuselage or propeller.
Intuition Check
Do not assume “down” always means safe for landing. For a retractable-gear aircraft, the important condition is landing gear down and locked, confirmed by the proper indication or checklist step.
Example Sentence 1
On final approach, the pilot verified landing gear down and locked by checking the three green indicator lights.
Example Sentence 2
With the landing gear down and locked, the aircraft touched down smoothly on the main wheels.