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The FAA requirement for sight distance on individual runways requires that the runway profile permit any two points 5 ft above the runway centerline to be mutually visible for the entire runway length.

**Sight Distance and Longitudinal Profile**

The FAA requirement for
sight distance on individual runways requires that the runway profile permit
any two points 5 ft above the runway centerline to be mutually visible for the
entire runway length. If, however, the runway has a full length parallel
taxiway, the runway profile may be such that an unobstructed line of sight will
exist from any point 5 ft above the runway centerline to any other point 5 ft
above the runway centerline for one-half the runway length.

The FAA recommends a
clear line of sight between the ends of intersecting runways. The terrain must
be graded and permanent objects designed and sited so that there will be an
unobstructed line of sight from any point 5 ft above one runway centerline to
any point 5 ft above an intersecting runway centerline within the runway
visibility zone. The runway visibility zone is the area formed by imaginary
lines connecting the visibility points of the two intersecting runways. The
runway visibility zone for intersecting runways is shown in Fig. 6-21. The
visibility points are defined as follows:

1.
If the distance from the intersection of
the two runway centerlines is 750 ft or less, the visibility point is on the
centerline at the runway end designated by point .

2.
If the distance from the intersection of
the two runway centerlines is greater than 750 ft but less than 1500 ft, the
visibility 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 centerlines 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.

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 centerline 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 runways, 2 m (7
ft) above the runway for aerodrome code letter B runways, 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*Applies
also to runway safety area adjacent to sides of the runway.* b*May not
exceed 0.8 percent in the first and last quarter of runway.* c*A minimum
of 3 percent for turf.

*d*A
slope of 5 percent is recommended for a 10 ft width adjacent to the pavement
areas to* *promote drainage.

*e*For
the first 200 ft from the end of the runway and if it slopes it must be
downward. For* *the remainder of the runway safety area the slope must be
such that any upward slope does not penetrate the approach surface or clearway
plane and any downward slope does not exceed 5 percent.

*f*For each 1 percent
change in grade.

*g*No
vertical curve is required if the grade change is less than 0.4 percent.* h*Distance
is multiplied by the sum of the absolute grade grade changes in percent.*
Source: *Federal Aviation Administration [6].

longitudinal gradient
and longitudinal grade changes to 2 percent for runways serving approach
category A and B aircraft and 1.5 percent for runways serving approach category
C, D, and E aircraft. ICAO limits both longitudinal gradient and longitudinal
grade changes to

2 percent for aerodrome
code number 1 and 2 runways and 1.5 percent for aerodrome code number 3
runways. For aerodrome code number 4 runways the maximum longitudinal gradient
is 1.25 percent and the maximum change in longitudinal gradient is 1.5 percent.
In addition, for runways that are equipped to be used in bad weather, the
gradient of the first and last quarter of the length of the runway must be very
flat for reasons of safety. Both the ICAO and the FAA require that this
gradient not exceed 0.8 percent. In all cases it is desirable to keep both
longitudinal grades and grade changes to a minimum.

Longitudinal slope
changes are accomplished by means of vertical curves. The length of a vertical
curve is determined by the magnitude of the changes in slope and the maximum
allowable change in the slope of the runway.

*May not exceed 0.8
percent in the first and last quarter of runway for aerodrome code number 4 or
for a category II or III precision instrument runway for aerodrome code number
3.

†Difference in
elevation between high and lo ‡For each 1 percent change in grade.

§Distance is multiplied by sum of absolute grade
changes in percent minimum length is 45 m.

The number of slope changes along the runway is also
limited.

The FAA requires that
the distance between the points of intersection of two successive curves should
not be less than the sum of the absolute percentage values of change in slope
multiplied by the 250 ft for airports serving aircraft approach category A and
B aircraft and 1000 ft for airports serving aircraft approach category C, D,
and E aircraft.

The ICAO requires that
the distance between the points of intersection of two successive curves should
not be less than the sum of the absolute percentage values of change in slope
multiplied by 50 m (165 ft) for aerodrome code number 1 and 2 runways, 150 m
(500 ft) for aerodrome code number 3 runways, and 300 m (1000 ft) for aerodrome
code number 4 runways. ICAO also specifies that the minimum distance in all
cases is 45 m (150 ft).

For example, for an FAA
runway serving transport aircraft, that is, approach category C, D, or E
aircraft, if the change in slope was 1.5 percent, the required length of
vertical curve would be 1500 ft. Vertical curves are normally not necessary if
the change in slope is not more than 0.4 percent. The FAA specifies a minimum
length of vertical transition curve of 300 for each 1 percent change in grade
for runways

*For facilities for small aircraft only.

†Satisfies the
requirement that no part of a separations may be needed to achieve this result.

‡Forealevelsup to
elevation 6000 ft. Increase by 1 ft for each 100 ft of airport elevation above
6000 ft.

serving approach
category A and B aircraft and 1000 ft for each 1 percent change in grade for
airport serving approach category C, D, and E aircraft. ICAO specifies a
minimum length of vertical transition curve

of 75 m for each 1
percent change in grade for aerodrome code number 1 runways, 150 m for each 1
percent change in grade aerodrome code number 2 runways, and 300 m for each 1
percent change in grade for aerodrome code number 4 runways.

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