Definition
A set of standardized colored light signals directed at an aircraft from the control tower, used to communicate clearances and instructions when normal two-way radio communication is not available. The signals use steady or flashing green, red, or white light, with specific meanings depending on whether the aircraft is in flight or on the ground.
Plain English
When a pilot can't use the radio, the tower can shine a colored light at the aircraft to tell the pilot what to do. The color of the light, and whether it is steady or flashing, tells the pilot whether to land, hold, give way, or return to the airport.
Context Anchor
Seen in lost communication procedures and at airports with an operating control tower.
Derivation
Called a 'light gun' because the device used by controllers is a hand-held, gun-shaped projector that aims a focused beam of light at a specific aircraft. The pilot in that aircraft sees the light, but other aircraft in the area do not.
Why Pilots Care
Provides a reliable backup method for receiving ATC instructions, clearances, and safety directives, preventing runway incursions and enabling continued safe flight operations.
Intuition Check
Do not assume these signals work exactly like road traffic lights. In aviation, the color, steady-or-flashing pattern, and whether you are airborne or on the ground determine the instruction.
Example Sentence 1
After the radio failed on downwind, the pilot watched the tower for light gun signals and received a steady green, clearing the aircraft to land.
Example Sentence 2
The controller responded with a steady green light gun signal, indicating the aircraft could taxi to the ramp.