Definition
A VASI (Visual Approach Slope Indicator) signal in which both the near and far light bars appear red to the pilot, indicating the aircraft is below the proper glide path on final approach.
Plain English
When you look at the runway's two-bar approach lights and see red on top and red on the bottom, you are flying too low and need to climb to get back on the correct descent path.
Context Anchor
Seen while using a VASI during final approach to a runway.
Why Pilots Care
Being below the glide path increases the risk of striking obstacles or terrain short of the runway.
Grounding Statement
On final approach, red over red means the airplane needs to be brought back up to the normal descent path before continuing.
Intuition Check
Do not read red over red as just a color description. In a VASI, it is a specific approach-path warning: both bars red means you are below the glide path.
Example Sentence 1
Halfway down final, the pilot saw red over red on the VASI and added power to regain the glide path.
Example Sentence 2
During the night approach the student recognized red over red and initiated a go-around.