Page 258 - Planning and Design of Airports

Geometric Design of the Airfield 221

6. Except for traverse ways on or near an airport with an opera-
tive ground traffic control service furnished by the air traffic
control tower or by airport management and coordinated
with the air traffic control service, the heights of traverse
ways must be increased by 17 ft for interstate highways, 15 ft
for any other public roadway, 10 ft or the height of the highest
mobile object that would normally traverse the road, which-
ever is greater, for a private road, 23 ft or an amount equal to
the height of the highest mobile object that would normally
traverse it for railroads, waterways, or any other thorough-
fare not previously mentioned.
Subpart B of FAR Part 77 identifies circumstances where notice is
required to be given to the FAA when certain construction or altera-
tion activities are proposed. These include the circumstances associ-
ated with the standards given above and also any construction or
alteration of greater height than an imaginary surface extending out-
ward and upward at one of the following slopes [9]:

1. A slope of 100 horizontal to 1 vertical for a horizontal dis-
tance of 20,000 ft from the nearest point of the nearest runway
at an airport or seaplane base with at least one runway more
than 3200 ft in actual length.
2. A slope of 50 horizontal to 1 vertical for a horizontal distance
of 10,000 ft from the nearest point of the nearest runway at an
airport or seaplane base with its longest runway no more
than 3200 ft in actual length.
3. A slope of 25 horizontal to 1 vertical for a horizontal distance
of 5000 ft from the nearest point of the nearest takeoff and
landing area for a heliport.
FAR Part 77 imposes strict requirements on both airport sponsors
and others associated with construction activities in the vicinity of
airports which should be referenced prior to initiating construction
activities.

ICAO Annex 14
The ICAO requirements are similar to FAR Part 77 with the following
exceptions. ICAO separates arrivals and departures and specifies
dimensions for approach surfaces and takeoff climb surfaces for
departures. The horizontal surface specified by ICAO is a circle whose
center is at the airport reference point, whereas in FAR Part 77 it is not a
circle nor is the airport reference point used to determine the horizon-
tal surface. The airport reference point is the geometric centroid of the
runway system at the airport based upon the lengths of the runways.
The height of this surface is 150 ft above the airport elevation, the
same as in Part 77. In FAR Part 77 the conical surface extends horizon-
tally 4000 ft at a slope of 20 to 1 irrespective of the type of runway and