What is the purpose of a marker beacon test?

• A. To verify outer, middle, and inner marker signals are present and correct.
• B. To calibrate the ILS localizer.
• C. To measure wind speed.
• D. To test radio communications.

Answer: (A)

Marker beacons provide location cues on an ILS through three distinct beacons that transmit at 75 MHz and present different in-cockpit indicators: outer marker, middle marker, and inner marker. The test for marker beacons specifically verifies that each of these marker signals is present and correct, including the corresponding audio tones and the cockpit marker lights lighting up as expected. This ensures the approach system is functioning properly so pilots can rely on the markers to identify where they are along the approach path and to confirm the aircraft is positioned correctly for descent.

The other options aren’t what the test checks: calibrating the ILS localizer involves a different part of the runway guidance system, wind speed is unrelated to marker beacons, and testing radio communications covers a separate system entirely.