Definition
In an ILS (Instrument Landing System) context, reflection is the bouncing of localizer or glideslope radio signals off nearby surfaces — such as buildings, terrain, vehicles, or other aircraft — which can distort the guidance signal received in the cockpit and cause the course or glidepath needle to fluctuate or give a false indication.
Plain English
The ILS signal is a radio beam. When that beam bounces off something near the runway — like a hangar, a taxiing aircraft, or a hill — the bounced signal can mix with the real one and confuse the cockpit instrument, making the needle wobble or point slightly wrong.
Context Anchor
Seen in ILS error discussions, especially when explaining why the left-right or up-down approach guidance may move unexpectedly or appear inaccurate.
Derivation
From Latin reflectere, meaning 'to bend back.' The aviation use is literal: radio waves bend back off a surface instead of traveling straight to the aircraft.
Why Pilots Care
Reflections can produce false localizer or glideslope indications, potentially guiding the aircraft off the safe path during an instrument approach.
Analogy
It is similar to seeing sunlight bounce off a window. The light is real, but it did not come to your eyes by the direct path, so it can create a misleading impression of where the source is.
Grounding Statement
Picture a guidance signal reaching the aircraft directly while a bounced copy arrives from another direction and slightly confuses the instrument display.
Intuition Check
Reflection does not mean only a mirror-like visual effect. In this context, it means a radio guidance signal bouncing off a surface and possibly creating a false or unstable cockpit indication.
Example Sentence 1
Tower held the departing aircraft short of the runway to prevent reflection of the ILS signal during the inbound traffic's Category II approach.
Example Sentence 2
Terrain reflection can create false courses on the localizer during an ILS approach.