Definition
On a retractable-gear airplane, a green indicator light on the instrument panel that illuminates to confirm the landing gear is fully extended and locked down in position for landing. Most installations use a separate green light for each gear leg, and all must be illuminated before landing.
Plain English
A small green lamp on the panel that turns on when the landing gear is all the way down and locked. If you see green, the gear is ready for landing.
Context Anchor
Seen on cockpit position indicators, especially during landing gear checks before landing.
Derivation
Green has long been used as a signal color for permission, normal condition, or safety. Light means a visible signal. In this cockpit use, green is not just a color; it is a status message.
Why Pilots Care
Allows pilots to instantly determine the direction and attitude of other aircraft at night, directly reducing mid-air collision risk during night operations.
Intuition Check
Do not read green light as merely a lamp that happens to be green. In this context, it means a cockpit indication that the gear or another system has reached the intended safe position.
Example Sentence 1
After lowering the gear handle on downwind, the pilot waited for three green lights before continuing the approach.
Example Sentence 2
The pilot recognized the other aircraft was flying toward him because its green light appeared on the right side of the oncoming plane.