Instrument Landing System (ILS) components – relative siting In a standard ILS arrangement for a runway, how are the Localizer (LOC) antenna and the marker beacons (Outer Marker, OM, and Middle Marker, MM) typically sited relative to each other?

Introduction / Context:
The Instrument Landing System (ILS) guides aircraft laterally and vertically to the runway. Understanding where its components are located helps with both design and pilot situational awareness.

Given Data / Assumptions:

• Localizer (LOC) provides lateral guidance, normally located beyond the far end of the runway on the extended centreline.
• Outer Marker (OM) and Middle Marker (MM) are approach-side beacons sited along the extended centreline before the threshold.

Concept / Approach:
Since OM and MM lie along the approach path on the approach side, and the LOC antenna is typically placed beyond the departure end to radiate down the runway centreline, they end up on opposite sides of the landing threshold.

Step-by-Step Solution:
Identify approach-side elements: OM and MM.Identify far-end element: Localizer antenna beyond the runway end.Conclude they are on opposite sides of the runway.

Verification / Alternative check:
Standard ILS layout diagrams show marker beacons on approach and the LOC installation beyond the far end.

Why Other Options Are Wrong:
They misplace one or more components relative to the approach and far ends.

Common Pitfalls:
Confusing Locator beacons (NDBs) with Marker beacons; mixing Glide Slope (near the touchdown zone) with the Localizer location.

Final Answer:
OM and MM on one side of the runway; Localizer antenna on the opposite side