Definition
Mechanical latches in a retractable landing gear system that hold each gear leg securely in the up (retracted) position after retraction, preventing the gear from falling out of its wheel well due to gravity, airloads, or loss of hydraulic pressure.
Plain English
Small locks inside the wheel well that grab the landing gear once it's tucked up and hold it there until the pilot commands it down again.
Context Anchor
Encountered in retractable-gear airplanes, especially in landing gear system descriptions and emergency gear extension procedures.
Derivation
A compound of 'up' (the retracted position) and 'lock' (a device that secures something in place). The name describes exactly what it does: locks the gear up.
Why Pilots Care
If the uplocks do not release, the gear cannot extend; emergency systems are designed to unlock them so the gear can free-fall or be pumped down.
Intuition Check
Do not read uplocks as locks that make the gear safe for landing. Uplocks hold the gear up; they must release before the gear can come down.
Example Sentence 1
After the gear retracted, the green lights extinguished and the uplocks engaged, holding the wheels firmly in the wells.
Example Sentence 2
When the hydraulic system failed, the pilot used the emergency handle to release the uplocks and let the gear drop.