Definition
A secondary glideslope indication produced by the ILS glideslope antenna at an angle steeper than the published glide path, typically near twice the normal glide slope angle. It results from the way the glideslope signal pattern radiates and is not a usable approach reference. Pilots can avoid capturing it by intercepting the glideslope from below at the published intercept altitude.
Plain English
A fake glideslope reading that appears higher up than the real one. The instrument shows you're on the glideslope when you're actually on a much steeper, false beam that won't bring you safely to the runway.
Context Anchor
Seen during instrument approach procedures, especially when a glideslope indication appears while flying a localizer back course approach.
Derivation
False' here means deceptive or misleading -- the signal looks like a real glideslope on the instrument but isn't the one you're meant to follow. The word comes from Latin 'falsus,' meaning deceived or mistaken.
Why Pilots Care
Following a false glideslope can produce an unstable or dangerously steep descent and risk landing short of the runway.
Analogy
It is like a road sign that points toward the right destination but is posted on the wrong road. It may look helpful, but following it can take you somewhere unsafe.
Grounding Statement
If the procedure does not authorize glideslope guidance, a glideslope-looking indication is not permission to descend.
Intuition Check
Do not assume that a centered glideslope needle means the descent path is valid. For this term, “false” means the signal may appear real but is not approved guidance for that approach.
Example Sentence 1
The instructor reminded the student to intercept the glideslope from below to avoid locking onto a false glideslope signal.
Example Sentence 2
Always cross-check altitude against distance to avoid following a false glideslope signal during the final segment.