ILS critical area

ILS (instrument landing system) critical area

An area of defined dimensions in the vicinity of localizer and glide-path antenna arrays within which vehicle operations may interfere with the radio signal transmitted by the NAVAIDs (navigational aids).
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
This is why you'll sometimes see ILS critical area markings on taxiways to avoid impact on ILS system signals, depending upon the location and type of antenna, the location of taxiways, and the types of expected operations.
Similar to the RSA sign above, this symbology also is located on the back side of a sign; in this case, the ILS critical area sign.
You could be on a coupled approach with a reported ceiling of 900 feet, and at 1200 feet AGL experience distortions as a Citation Jet taxies up to the hold-short line through an unprotected ILS critical area. It's entirely possible something like this happened to us at O'Hare.
A pilot can request that ATC protect the ILS critical area (although I wouldn't try it at O'Hare).
If you're taxiing out at an airport that's uncontrolled (due to a closed tower or otherwise) and you notice an ILS critical area, pause and think before you taxi past.
ILS critical areas are established to mitigate exactly this kind of interference.
"Unmonitored" and the construction equipment being in the ILS critical area (we're guessing) had nothing to do with each other.
Because other aircraft or vehicles can skew the signal, ground control may ask you to observe the ILS critical area hold short lines when the weather is lower than 800 feet and two miles or 200 feet and RVR 2000 (when an inbound is inside the MM).
For this reason, ILS Critical Areas are established and when weather is below 800-2, towers keep these areas clear.