Definition
A type of visual glide slope indicator used at some airports, classified by the FAA as a non-standard visual approach aid. APAP systems use the alignment of two or more visual elements (such as bars, panels, or markers) to show the pilot whether the aircraft is on, above, or below the correct approach path to the runway. APAP is listed in FAA approach lighting legends as a recognized but non-standard glide slope reference.
Plain English
A simple visual aid beside the runway that tells you if you are too high, too low, or on the right path as you come in to land. It works by lining up two visible markers — when they line up correctly, you are on the right glide path.
Context Anchor
Seen in approach lighting legends and runway information, especially when identifying what visual guidance is available for landing.
Derivation
The name describes how the system works: it uses the alignment of physical elements (bars or panels) as the cue. The pilot lines up the elements visually, and that alignment tells them their position relative to the correct approach path.
Why Pilots Care
Ensures accurate lateral positioning on final approach, reducing the chance of drifting off the runway centerline in low visibility.
Analogy
Think of the iron sights on a rifle: when the front and rear sights line up, you are aimed correctly. APAP works the same way visually — when the elements line up, your approach path is correct.
Grounding Statement
On approach to landing, APAP gives the pilot a simple visual check: if the elements line up as intended, the descent path is about right.
Intuition Check
APAP is not a system that aligns the airplane with the runway centerline. It is a visual aid for judging the descent path down to the runway.
Example Sentence 1
The chart legend showed APAP at the destination airport, so the pilot reviewed how to read the alignment before starting the approach.
Example Sentence 2
During the night approach the APAP provided clear lateral guidance when the runway edge lights were still too far to discern.