Section 4. Lateral Separation
8-4-1. APPLICATION
Separate aircraft by assigning different flight paths
whose widths or protected airspace do not overlap.
Within that portion of the Gulf of Mexico Low
Offshore airspace controlled by Houston ARTCC,
use 12 NM between aircraft whose flight paths are
defined by published Grid System waypoints.
NOTE-
1. The Grid System is defined as those waypoints
contained within the Gulf of Mexico Low Offshore airspace
and published on the IFR Vertical Flight Reference Chart.
2. Lateral separation minima is contained in:
Section 7, North Atlantic ICAO
Region.
Section 8, Caribbean ICAO Region.
Section 9, Pacific ICAO Region.
Section 10, North American
ICAO Region-
Arctic CTA.
8-4-2. SEPARATION METHODS
Lateral separation exists for:
a. Nonintersecting flight paths:
1. When the required distance is maintained
between the flight paths; or (See FIG 8-4-1.)
FIG 8-4-1
Separation Methods
2. When reduced route protected airspace is
applicable, and the protected airspace of the flight
paths do not overlap; or (See FIG 8-4-2.)
FIG 8-4-2
Separation Methods
3. When aircraft are crossing an oceanic
boundary and are entering an airspace with a larger
lateral minimum than the airspace being exited; and
(a) The smaller separation exists at the
boundary; and
(b) Flight paths diverge by 15° or more until
the larger minimum is established. (See FIG 8-4-3.)
FIG 8-4-3
Separation Methods
b. Intersecting flight paths with constant and same
width protected airspace when either aircraft is at or
beyond a distance equal to the applicable lateral
separation minimum measured perpendicular to the
flight path of the other aircraft. (See FIG 8-4-4.)
FIG 8-4-4
Separation Methods
c. Intersecting flight paths with constant but
different width protected airspace when either
aircraft is at or beyond a distance equal to the sum of
the protected airspace of both flight paths measured
perpendicular to the flight path of the other aircraft.
(See FIG 8-4-5.)
FIG 8-4-5
Separation Methods
d. Intersecting flight paths with variable width
protected airspace when either aircraft is at or beyond
a distance equal to the sum of the protected airspace
of both flight paths measured perpendicular to the
flight path of the other aircraft. Measure protected
airspace for each aircraft perpendicular to its flight
path at the first point or the last point, as applicable,
of protected airspace overlap.
NOTE-
In FIG 8-4-5, the protected airspace for westbound
flight A is distance "a" (50 miles), and for southwestbound
flight B, distance "b" (10 miles). Therefore, the sum of
distances "a" and "b"; i.e., the protected airspace of
Aircrafts A and B, establishes the lateral separation
minimum (60 miles) applicable for either flight relevant to
the other.
FIG 8-4-6
Separation Methods
NOTE-
(See FIG 8-4-6.) At the first point of protected airspace
overlap, the protected airspace for westbound flight A is
distance "a" (50 miles), and for southbound flight B,
distance "b" (40 miles). The sum of distances "a" and "b"
(90 miles) establishes the lateral separation minimum
applicable in this example for either flight as it approaches
the intersection. For example, Aircraft B should be
vertically separated from Aircraft A by the time it reaches
point "p."
FIG 8-4-7
Separation Methods
NOTE-
(See FIG 8-4-7.) Distance "a" (50 miles) and "b"
(30 miles) are determined at the last point of protected
airspace overlap. The sum of the distances "a" and "b"
(80 miles) establishes the lateral separation minima
applicable for either flight after it passes beyond the
intersection. For example, Aircraft B could be cleared to,
or through, Aircraft A's altitude after passing point "r."
8-4-3. REDUCTION OF ROUTE
PROTECTED AIRSPACE
When routes have been satisfactorily flight checked
and notice has been given to users, reduction in route
protected airspace may be made as follows:
a. Below FL 240, reduce the width of the protected
airspace to 5 miles on each side of the route centerline
to a distance of 57.14 miles from the NAVAID, then
increasing in width on a 5° angle from the route
centerline, measured at the NAVAID, to the
maximum width allowable within the lateral minima;
for example, 50 miles of protected airspace on each
side of centerline; i.e., a lateral minimum of
100 miles. (See FIG 8-4-8.)
FIG 8-4-8
Reduction of Route Protected Airspace
b. At and above FL 240, reduce the width of the
protected airspace to 10 miles on each side of the
route centerline to a distance of 114.29 miles from the
NAVAID, then increasing in width on a 5° angle from
the route centerline, as measured at the NAVAID, to
the maximum width allowable within the lateral
minima; for example, 60 miles of protected airspace
on each side of the centerline; i.e., a lateral separation
minimum of 120 miles. (See FIG 8-4-9.)
FIG 8-4-9
Reduction of Route Protected Airspace
8-4-4. TRACK SEPARATION
Apply track separation between aircraft by requiring
aircraft to fly specified tracks or radials and with
specified spacings as follows:
a. Same NAVAID:
1. VOR/VORTAC/TACAN. Consider separation to exist between aircraft established on radials of
the same NAVAID that diverge by at least 15 degrees
when either aircraft is clear of the airspace to be
protected for the other aircraft. Use TBL 8-4-1 to
determine the flight distance required for various
divergence angles and altitudes to clear the airspace
to be protected. (See FIG 8-4-10.)
TBL 8-4-1
Divergence-Distance Minima
VOR/VORTAC/TACAN
|
Distance (mile)
|
Divergence (degrees)
|
FL 230 and
below
|
Fl 240
through
FL 450
|
15-25
|
17
|
18
|
26-35
|
11
|
13
|
36-90
|
8
|
11
|
Note: This table compensates for DME slant range
error.
|
FIG 8-4-10
Track Separation VOR
2. NDB:
(a) Consider separation to exist between
aircraft established on tracks of the same NAVAID
that diverge by at least 30 degrees and one aircraft is
at least 15 miles from the NAVAID. This separation
shall not be used when one or both aircraft are
inbound to the aid unless the distance of the aircraft
from the facility can be readily determined by
reference to the NAVAID. Use TBL 8-4-2 to
determine the flight distance required for various
divergence angles to clear the airspace to be
protected. For divergence that falls between
two values, use the lesser value to obtain the distance.
(See FIG 8-4-11.)
TBL 8-4-2
Divergence-Distance Minima (NDB)
|
Distance (mile)
|
Divergence (degrees)
|
FL 230 and
below
|
FL 240
through
FL 450
|
30
|
16
|
17
|
45
|
13
|
14
|
60
|
9
|
10
|
75
|
7
|
8
|
90
|
6
|
7
|
Note: This table compensates for DME slant range
error.
|
FIG 8-4-11
Track Separation NDB
(b) Clear aircraft navigating on NDB facilities in accordance with para 2-5-2, NAVAID
Terms.
b. Different NAVAIDs:
Separate aircraft using different navigation aids by assigning tracks so that
their protected airspace does not overlap. (See FIG 8-4-12.)
FIG 8-4-12
Track Separation
Different NAVAIDs
c. Dead Reckoning (DR):
1. Consider separation to exist between aircraft
established on tracks that diverge by at least
45 degrees when one aircraft is at least 15 miles from
the point of intersection of the tracks. This point may
be determined either visually or by reference to a
ground-based navigation aid. (See FIG 8-4-13.)
FIG 8-4-13
Track Separation
Dead Reckoning
|