Section 171.313

14 CFR Ch. I (1-1-19 Edition)

the coverage requirement is reduced to
14 nm beyond Section40Section.
(2) Vertically between:
(i) A conical surface originating 2.5
meters (8 feet) above the runway centerline at threshold inclined at 0.9 degree above the horizontal.
(ii) A conical surface originating at
the azimuth ground equipment antenna
inclined at 15 degrees above the horizontal to a height of 6,000 meters (20,000
feet).
(iii) Where intervening obstacles penetrate the lower surface, coverage need
be provided only to the minimum line
of sight.
(3) Runway region:
(i)
Proportional
guidance
horizontally within a sector 45 meters (150
feet) each side of the runway centerline
beginning at the stop end and extending parallel with the runway centerline
in the direction of the approach to join

the approach region. This requirement
does not apply to offset azimuth installations.
(ii) Vertically between a horizontal
surface which is 2.5 meters (8 feet)
above the farthest point of runway centerline which is in line of sight of the
azimuth antenna, and in a conical surface originating at the azimuth ground
equipment antenna inclined at 20 degrees above the horizontal up to a
height to 600 meters (2,000 feet). This
requirement does not apply to offset
azimuth installations.
(4) Within the approach azimuth coverage sector defined in paragraphs (a)
(1), and (2) and (3) of this section, the
power densities must not be less than
those shown in Table 9 but the equipment design must also allow for:
(i) Transmitter power degradation
from normal by Section1.5 dB;

TABLE 9 - MINIMUM POWER DENSITY WITHIN COVERAGE BOUNDARIES(DBW/M 2)
Data
signals

Function

Angle signals for various antenna
beamwidths
1Section

Approach azimuth .......................................................................
High rate approach azimuth ........................................................
Back azimuth ...............................................................................
Approach elevation .....................................................................

(ii) Rain loss of Section2.2 dB at the longitudinal coverage extremes.
(b) Siting requirements. The approach
azimuth antenna system must, except
as allowed in paragraph (c) of this section:
(1) Be located on the extension of the
centerline of the runway beyond the
stop end;
(2) Be adjusted so that the zero degree azimuth plane will be a vertical
plane which contains the centerline of
the runway served;
(3) Have the minimum height necessary to comply with the coverage requirements prescribed in paragraph (a)
of this section;
(4) Be located at a distance from the
stop end of the runway that is consistent with safe obstruction clearance
practices;
(5) Not obscure any light of an approach lighting system; and

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(6) Be installed on frangible mounts
or beyond the 300 meter (1,000 feet)
light bar.
(c) On runways where limited terrain
prevents the azimuth antenna from
being positioned on the runway centerline extended, and the cost of the land
fill or a tall tower antenna support is
prohibitive, the azimuth antenna may
be offset.
(d) Antenna coordinates. The scanning
beams transmitted by the approach
azimuth equipment within Section40Section of the
centerline may be either conical or
planar.
(e) Approach azimuth accuracy. (1) The
system and subsystem errors shall not
exceed those listed in Table 10 at the
approach reference datum.
At the approach reference datum,
temporal sinusoidal noise components
shall not exceed 0.025 degree peak in
the frequency band 0.01 Hz to 1.6 Hz,
and the CMN shall not exceed 0.10 degree. From the approach reference

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