The aim of this chapter is to present a summary view of the typical CAT II or CAT III airfield requirements.
5.2 RUNWAY CHARACTERISTICS
5.2.1 RUNWAY LENGTH
There is no specific requirement concerning runway length for an aerodrome to be CAT II or III approved. The runway length is only an operational limitation.
5.2.2 RUNWAY WIDTH
The runway width should be normally not less than 45m.
5.2.3 RUNWAY SLOPE
For CAT II or CAT III, disregarding normal standards, it is recommended that for the first and the last quarter of the length of the runway the slope does not exceed
0.8%.
To permit the use of the automatic landing system, ICAO also recommends thatslope changes must be avoided or, when it is not possible, kept to a maximum of 2% per 30m (i.e. a minimum radius of curvature of 1500m) in the area located just before the threshold (60m wide, 200m long). This limitation is due to the fact that automatic landing systems use radio altimeter and a rapid slope change could disturb the landing.
During airworthiness certification, it must be demonstrated that the automatic landing system works on a particular runway profile (see aircraft requirements).
5.2.4 OBJECTS ON RUNWAY STRIPS
It is recommended that for runways intended for use for CAT II or CAT III approaches, no fixed object (other than frangible visual aids) are installed on a runway strip within 60m of the centerline. During landing, no mobile objects are permitted in the same area.
5.2.5 TAXI-HOLDING POSITION
A taxi-holding position is established at each intersection of a taxiway and therunway. The distance between the holding position and the centerline of the runway is not less than 90m (greater if the runway elevation exceeds 700m).
5.3 VISUAL AIDS-RUNWAY MARKS
5.3.1 RUNWAY CENTRELINE MARKS
For CAT II or CAT III operations, the runway centerline marks, as shown in Figure 5.2, must have a width not less than 0.90m (or not less than 0.45m for CAT I).
5.3.2 TOUCHDOWN ZONE MARKS
Touchdown zone marks, as shown in Figure 5.2, are required for all precision
approaches, unless the authority declares that they are unnecessary.
They are painted in the touchdown zone (the zone beginning at the threshold and
extending to a distance of 900m).

5.3.3 TAXIWAY MARKS
Taxiway marks are not a specific CAT II or CAT III requirement, but experience has shown that they are an efficient means of guiding aircraft in low visibility conditions during the day.
5.3.4 TAXI-HOLDING POSITION MARKINGS
The taxi-holding positions must be as shown in pattern A for the closest marks to the runway and pattern B for the other markings (see Figure 5.3). Either CAT II or CAT III is written on the surface when the area exceeds 60m width. CAT II or CAT III signs are also placed on either edge of the taxiway at the holding-position and the sign CAT III must be accompanied with flashing lights. These markings or signs are an efficient means to avoid aircraft intruding into the obstacle-free zone or in the critical/sensitive area.
　
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