Definition
Ground-based light systems installed near the runway that show a pilot, by colored light signals, whether the aircraft is on, above, or below the correct approach path to the runway. Common types include VASI (Visual Approach Slope Indicator), PAPI (Precision Approach Path Indicator), tri-color systems, pulsating systems, and alignment-of-elements systems.
Plain English
Lights beside the runway that tell you, just by their color, whether you are too high, too low, or on the right path as you come in to land.
Context Anchor
You encounter visual glideslope indicators while approaching a runway to land, especially during the final part of the approach.
Derivation
‘Glideslope’ combines ‘glide’ (a steady descent without engine power adding altitude) and ‘slope’ (an angled path). ‘Visual’ distinguishes these ground lights from electronic glideslope signals used in instrument approaches — these you see with your eyes, not on an instrument.
Why Pilots Care
They allow precise descent control without instruments, reducing the chance of landing short or floating long.
Intuition Check
Do not assume “glideslope” here means only an instrument signal. In this term, it means a visual descent path shown by runway lights.
Example Sentence 1
On final approach, the pilot checked the visual glideslope indicators and saw two white and two red lights, confirming the aircraft was on the correct path.
Example Sentence 2
At night the visual glideslope indicators gave clear guidance for a stable final approach to the runway.