Definition
An audible alert in retractable-gear airplanes that sounds when the landing gear is not down and locked while the airplane is configured for landing. It is typically triggered by a combination of low throttle setting, low airspeed, or extension of the wing flaps when the gear handle is in the up position.
Plain English
A loud warning sound in the cockpit that tells the pilot the wheels are still up when it looks like they are getting ready to land.
Context Anchor
Encountered in retractable landing gear airplanes during approach, landing checks, and landing gear system training.
Derivation
“Gear” originally meant equipment or apparatus; in aviation, landing gear means the wheel and support system used for takeoff and landing. “Horn” comes from early signaling devices made from animal horns, and later came to mean a loud warning sound. Together, the phrase means a warning sound for the landing gear.
Why Pilots Care
It prevents gear-up landings that can damage the aircraft, cause loss of directional control, and result in expensive repairs or injuries.
Intuition Check
Do not think of “horn” as a hand-operated horn the pilot chooses to sound. In this term, it means an automatic warning sound triggered by the airplane when the landing gear condition does not match the landing situation.
Example Sentence 1
As he reduced power on final, the gear warning horn sounded, reminding him that the landing gear was still up.
Example Sentence 2
In the traffic pattern the gear warning horn activated after the flaps were lowered with the landing gear still up.