What is indicated by a green light on the SGSI?

A green light on the SGSI (Simplified Glide Slope Indicator) indicates that an aircraft is on the proper glide slope during its approach for landing. This visual guidance is crucial for pilots, providing an instant means of checking their alignment with the glide path without needing to rely solely on instruments or other situational indicators.

Maintaining the correct glide slope is essential for ensuring a safe and efficient landing; being on the glide path means the aircraft maintains an optimal descent angle towards the runway. The use of green as a color code is widely accepted in aviation and other fields as signifying “good” or “proceed,” thereby reinforcing that the aircraft is in the right position for landing. This clear visual cue helps to reduce the chances of accidents caused by misjudgment of altitude or approach angle.