Page 244 - Planning and Design of Airports

208 Airp o r t D e sign

2. If the distance from the intersection of the two runway cen-
terlines is greater than 750 ft but less than 1500 ft, the visibil-
ity point is on the centerline 750 ft from the intersection of the
centerlines designated by point b in Fig. 6-21.
3. If the distance from the intersection of the two runway cen-
terlines is equal to or greater than 1500 ft, the visibility point
is on the centerline equidistant from the runway end and the
intersection of the centerlines designated by points c and d in
Fig. 6-21.
The ICAO requirement for sight distance on individual runways
requires that the runway profile permit an unobstructed view
between any two points at a specified height above the runway cen-
terline to be mutually visible for a distance equal to at least one-half
the runway length. ICAO specifies that the height of these two points
be 1.5 m (5 ft) above the runway for aerodrome code letter A run-
ways, 2 m (7 ft) above the runway for aerodrome code letter B run-
ways, and 3 m (10 ft) above the runway for aerodrome code letter C,
D, or E runways.
It is desirable to minimize longitudinal grade changes as much as
possible. However, it is recognized that this may not be possible for
reasons of economy. Therefore both the ICAO and FAA allow changes

a

A

d x
1 750'
2 D 225 m b
D B
WHEN C
1 2
A ≤ 750' (225 m) RUNWAY VISIBILITY
B < 1500' (450 m) ZONE
BUT > 750' (225 m)
C ≥ 1500' (450 m) C c
D ≥ 1500' (450 m)
THEN
xa = DISTANCE TO
END OF RUNWAY
xb = 750' (225 m)
xc = ½ C
xd = ½ D

FIGURE 6-21 Runway visibility zone for intersecting runways (Federal Aviation
Administration).