Page 259 - Planning and Design of Airports

222 Airp o r t D e sign

visibility. In ICAO Annex 14 [1, 2, 3] the slope of the conical surface is
the same, but the horizontal distance varies depending upon the
aerodrome reference code.
In FAR Part 77 the slope of the transitional surface is a constant 7
to 1, whereas in ICAO Annex 14 this slope is specified for runway
reference codes 3 and 4. For other runways the slope is 5 to 1.

TERPS
As defined in FAA Order 8260.3b, TERPS (which stands for terminal
instrument approach procedures) is a compilation of criteria used to
design published standard procedures for aircraft using instrument-
based navigation to depart and approach to airport facilities. These
procedures are designed based primarily on the performance charac-
teristics of aircraft, the various types of instrument navigational aids
that may be present at or around an airport, and currently existing
natural and man-made objects surrounding the airport. As part of
these procedures, minimum climb-out gradients for aircraft depar-
tures, and minimum descent gradients and safe operating altitudes
for aircraft approaches are defined. While TERPS contain standards
for creating such procedures, for any given runway at any given air-
port, one or more approach and departure procedures may be defined,
each of which may be entirely unique, based on the airport environ-
ment.
With respect to airport design, TERPS defines a “required obsta-
cle clearance” (ROC) value. For aircraft operating within the airport
environment, this value is typically as low as 250 ft above the highest
object near the runway. The required obstacle clearance values for a
published procedure in turn define the TERPS obstacle clearance sur-
face (OCS), as illustrated in Fig. 6-27. The typical slopes for obstacle
clearance surfaces for aircraft on approach is on the order of 318 ft/nmi
and for departures approximately 200 ft/nmi.
A typical TERPS procedure consists of a series of segments,
including climb, en route, initial approach, intermediate approach,
final approach, and missed approach segments, that are created based

ROC
Glidepath

OCS
ASBL

FIGURE 6-27 TERPS obstacle clearance surface.