An airport ILS (Instrument Landing System) Critical Area is protected by ATC

Choices

• at all times, regardless of weather conditions.

  Incorrect. The protection is applied when the weather is low and an aircraft is on the approach, not continuously.

• ✓ when the weather is below an 800-foot ceiling and/or 2 miles visibility and an arriving aircraft is on approach.correct

  ATC holds aircraft and vehicles clear of the ILS critical area when the official weather is below a ceiling of 800 feet and/or visibility less than 2 miles and an arriving aircraft is between the ILS outer marker (or the final approach fix) and the runway — that is ordinary CAT I weather, not only CAT II/III. Metal structures inside the area reflect and distort the localizer and glideslope signals. CAT II/III operations protect a larger area still. Comply with hold-short instructions for the ILS critical area holding position markings.

• only during Category III autoland airline operations.

  Incorrect. CAT II/III operations expand the protected areas, but the basic trigger applies to ordinary CAT I approaches that GA pilots meet routinely.

• exclusively when the runway is closed to departures.

  Incorrect. Runway closure has nothing to do with ILS signal protection.