ILS critical area holding position sign

What the ILS critical area holding position sign is

The ILS critical area holding position sign is a mandatory instruction sign — a white inscription on a red background — that marks the runway-holding position which protects the ILS (or MLS) critical and sensitive areas. An aircraft or vehicle parked inside those areas can reflect or disturb the guidance signal, so during an approach in low visibility traffic must hold here rather than continue toward the runway.

It is closely related to the ordinary runway-holding position sign: both are red signs that tell you to stop and hold, but this one is specifically about keeping the instrument landing system's signal clean for the aircraft on final approach.

ICAO and FAA names

The protection of the ILS/MLS critical and sensitive areas is set out under ICAO Annex 14 Volume I and, in Europe, under EASA CS-ADR-DSN. The red hold sign that carries the literal "ILS" legend at this position is FAA-specific, named the ILS hold sign in its airport sign guidance and advisory circulars (AC 150/5340-18); crews commonly call it the "ILS hold". Under ICAO Annex 14 and EASA the equivalent low-visibility protection is signed via the CAT I/II/III holding position signs rather than an "ILS"-legend sign.

There is an important pairing to keep straight. The red ILS critical area holding position sign tells you where to stop and hold. The yellow-and-black ILS critical area boundary sign, on the far side, marks where you have cleared the critical area on the way out — see the ILS critical area boundary sign. The two are opposites in both colour and purpose: do not confuse the red holding position sign with the yellow boundary sign.

What it displays

The FAA ILS hold sign carries the literal "ILS" legend as a white inscription on the red field, oriented to the crew or driver approaching the hold, and it stands alongside the painted holding-position markings on the pavement. Under ICAO Annex 14 Volume I and EASA CS-ADR-DSN the equivalent low-visibility protection is signed instead via the CAT I/II/III holding position signs — a runway designator with a CAT annotation — not an "ILS"-legend sign.

The FAA advisory circulars govern how the "ILS" inscription is composed and how the sign is sized and positioned, so this page states the rule and leaves the exact figures to that specification.

Draw it accurately in Wingframe

The "ILS" inscription, the character height and the red field of the ILS critical area holding position sign are all fixed by the standard you work to. Wingframe draws the sign to FAA geometry for you, so the artwork you hand to the sign manufacturer is right the first time. See what Wingframe can do.