Definition
An aircraft position lower than the optimum descent path to the runway touchdown zone, as indicated by a visual or electronic glideslope guidance system. On a standard two-bar VASI, this condition is shown by both light bars appearing red.
Plain English
The airplane is lower than it should be on its approach to the runway, meaning it needs to climb a little or reduce its descent rate to get back onto the correct descent path.
Context Anchor
Seen during approaches and landings, especially when using visual approach slope lights near the runway.
Why Pilots Care
Being below glidepath risks landing short of the runway or colliding with obstacles.
Grounding Statement
Picture the normal path to the runway as a gentle downhill line; below glidepath means the airplane has dropped under that line.
Intuition Check
Do not read “below” as simply “low altitude.” In this phrase, it means lower than the desired approach path to the runway.
Example Sentence 1
Both VASI bars turned red, indicating the aircraft was below glidepath, so the pilot added power to regain the correct descent angle.
Example Sentence 2
On short final the instructor called for power because the airplane had drifted below glidepath.