What is the ILS critical area?

• A. The protected airspace around the ILS localizer where aircraft must not enter during approach
• B. The airspace segment used for holding while awaiting ILS availability
• C. The range at which ILS glideslope must be stabilized
• D. The area where ILS data is transmitted

Answer: (A)

The ILS critical area is the protected zone around the ILS localizer and glideslope antennas that must be kept clear when the ILS is operating. This area exists to shield the navigation signals from interference or multipath reflections caused by aircraft or vehicles on the surface, so the localizer and glideslope provide accurate guidance to pilots on approach. It’s not about holding for ILS availability, nor about the range where the glideslope must be stabilized, nor about where ILS data is transmitted. The critical area is specifically the surface area around the transmitter(s) that requires clearance during ILS use, often marked by ILS hold lines on taxiways.