The ILS critical areas must be maintained in order to provide CAT III beam quality to ILS point D, a point 3,000 feet down the runway from the threshold toward the LOC.
3-7-5. PRECISION APPROACH CRITICAL AREA
a. ILS critical area dimensions are described in FAAO 6750.16, Siting Criteria for Instrument Landing Systems. Aircraft and vehicle access to the ILS/MLS critical area must be controlled to ensure the integrity of ILS/MLS course signals whenever conditions are less than reported ceiling 800 feet or visibility less than 2 miles. Do not authorize vehicles/aircraft to operate in or over the critical area, except as specified in subpara a1, whenever an arriving aircraft is inside the ILS outer marker (OM) or the fix used in lieu of the OM unless the arriving aircraft has reported the runway in sight or is circling to land on another runway.
PHRASEOLOGY-
HOLD SHORT OF (runway) ILS/MLS CRITICAL AREA.
1. LOCALIZER CRITICAL AREA
(a) Do not authorize vehicle or aircraft operations in or over the area when an arriving aircraft is inside the ILS OM or the fix used in lieu of the OM when conditions are less than reported ceiling 800 feet or visibility less than 2 miles, except:
(1) A preceding arriving aircraft on the same or another runway that passes over or through the area while landing or exiting the runway.
(2) A preceding departing aircraft or missed approach on the same or another runway that passes through or over the area.
(b) In addition to subpara a1(a), do not authorize vehicles or aircraft operations in or over the area when an arriving aircraft is inside the middle marker when conditions are less than reported ceiling 200 feet or RVR 2,000 feet.
2. GLIDESLOPE CRITICAL AREA. Do not authorize vehicles or aircraft operations in or over the area when an arriving aircraft is inside the ILS OM or the fix used in lieu of the OM unless the arriving aircraft has reported the runway in sight or is circling to land on another runway when conditions are less than reported ceiling 800 feet or visibility less than 2 miles.
b. Air carriers commonly conduct “coupled” or “autoland” operations to satisfy maintenance, training, or reliability program requirements. Promptly issue an advisory if the critical area will not be protected when an arriving aircraft advises that a “coupled,” “CATIII,” “autoland,” or similar type approach will be conducted and the weather is reported ceiling of 800 feet or more, and the visibility is 2 miles or more.
PHRASEOLOGY-
ILS/MLS CRITICAL AREA NOT PROTECTED.
c. The Department of Defense (DOD) is authorized to define criteria for protection of precision approach critical areas at military controlled airports. This protection is provided to all aircraft operating at that military controlled airport. Waiver authority for DOD precision approach critical area criteria rests with the appropriate military authority.
NOTE-
Signs and markings are installed by the airport operator to define the ILS/MLS critical area. No point along the longitudinal axis of the aircraft is permitted past the hold line for holding purposes. The operator is responsible to properly position the aircraft, vehicle, or equipment at the appropriate hold line/sign or designated point. The requirements in para 3-1-12, Visually Scanning Runways, remain valid as appropriate.
REFERENCE-
AC150/5340-1, Standards for Airport Markings.
LOCALIZER CRITICAL AREAS. The latest edition of Order
6750.16, Siting Criteria for Instrument Landing Systems,
describes localizer and glide slope critical areas which shall be
marked and protected from parking and the unlimited movement of
surface and air traffic, to ensure the continuous integrity of
the signal received by the user aircraft.
a. The entire length of the longitudinal axis of the
aircraft shall be clear of the critical area when conditions are
such that the area must be protected. An aircraft with its
longitudinal axis aligned with the edge of a critical area is not
considered to be violating the critical area.
b. The worst case alignment of an aircraft for critical
area considerations is with its longitudinal axis perpendicular
to the runway (e.g., an aircraft departing the runway after
landing or taxiing across the runway).
c. The airport authority which controls ground traffic
movements must assure that appropriate controls and devices are
correctly located, and specific holding instructions implemented
when necessary, to protect the critical areas from ground traffic
approaching or departing an active runway if the critical area
dimension exceeds the distance of the normal runway holding
position marking from the runway centerline. Also, procedures
must be implemented to determine when an aircraft is clear of the
critical area when exiting the runway. Taxiway centerline
lead-off lights, where installed, shall be color-coded as
alternating green and yellow to denote the critical area. For
taxiways not equipped with centerline lights, a "Critical Area
Boundary" sign may be installed on the back side of the ILS sign
to indicate the critical area boundary.
d. Where the standard critical area has a significant
adverse impact on a specific taxi route, etc., it may be possible
through operational constraints to provide relief on a case-by-
case basis (e.g., considering the varying size of aircraft).
Mathematical modeling techniques are readily available to
facilitate this consideration.
REFERENCE-
FAAO 6750.24D
Looks like the controller definitely didn't protect the critical area.
Any bets as to who gets hammered with the mistake?
Jurassic Jet