Definition
A display element on an electronic flight display that shows the aircraft's vertical position relative to a desired descent path during an instrument approach. It typically appears as a moving pointer or diamond on a fixed vertical scale next to the attitude indicator, deflecting up when the aircraft is below the path and down when above. It receives signals from a precision approach aid (such as an ILS glideslope) or from a vertical guidance source generated by the navigation system (such as LPV or LNAV/VNAV).
Plain English
A small indicator on the cockpit display that tells the pilot whether the airplane is on, above, or below the correct downward path to the runway during an approach.
Context Anchor
Seen on an electronic flight display while flying an instrument approach to a runway.
Derivation
Glideslope' combines 'glide' (a controlled descent without added power) with 'slope' (an inclined line). 'Vertical guidance indicator' is the broader term used because modern systems provide a descent path from sources other than a traditional ILS glideslope, such as satellite-based approaches.
Why Pilots Care
It allows the pilot to make small pitch corrections to stay on the proper descent path for a safe landing.
Grounding Statement
On approach, the indicator gives a quick visual check of whether the aircraft is lined up vertically with the intended path down to the runway.
Intuition Check
This does not show the aircraft’s pitch attitude or rate of descent by itself. It shows the aircraft’s position compared with the desired vertical path.
Example Sentence 1
As the aircraft intercepted the final approach course, the pilot watched the glideslope/vertical guidance indicator center and began the descent.
Example Sentence 2
When the indicator moved below center, the airplane was flying above the glideslope.