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2.4.2 RF Segment.
See figure 2-4, and calculate the descent gradient using formula 2-1 where d is
calculated using formula 2-2.
Figure 2-4. RF Segment Descent Gradient
Track Distance (d)
Terminating
Fix
Initial
Fix
Turn
Center
R
α
Formula 2-2
180
where = degrees of arc
R = turn radius
d R
α
α × × π
=
Example
=55° R=6.0
55 60 576
180
d . .
α
× ×π
= =
2.5 RNP SEGMENT ROC.
Minimum ROC requirements are listed by segment type in table 2-2.
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Par 2.5 Page 2-5
Table 2-2. Minimum ROC Values
Segment ROC Value
Feeder 2000/1000
Initial 1000
Intermediate 500 or VEB Value
Final VEB
2.6 TF LEG SEGMENT.
A TF leg is a geodesic flight path between two fixes. The first fix is either the
previous leg termination fix or the initial (first) fix of a TF leg (see figure 2-5).
Figure 2-5. TF Leg
2.6.1 OEA Construction of Turns at Fly-By Waypoints that Join Two TF Legs.
This construction is the standard for fly-by turn construction. Limit turns at a flyby
fix to a maximum of 70° where aircraft are expected to cross (fly-by) the fix at
altitudes above FL 190, 120° at and below FL 190. When obstructions prevent
use of this construction, consider using an RF leg construction to accomplish the
course change (see paragraph 2.7). Construct fly-by turning OEAs using the
following steps:
STEP 1: Construct the turning flight path. Determine the turn radius (R) as
described in paragraph 1.11.2 (formula 1-2). Placing the origin on the angle
bisector line, scribe an arc of radius R tangent to the inbound and outbound legs
(see figure 2-4).
STEP 2: Construct the outer OEA boundary line. Using the turn fix as the origin,
scribe an arc of radius 2RNP tangent to the inbound (or preceding) and
outbound (or succeeding) TF legs.
STEP 3: Construct inner turn expansion boundary line. Placing the origin on the
angle bisector line, scribe an arc of radius R+1RNP from the tangent point on
the inbound (or preceding) leg inner boundary to the tangent point on the
outbound (or succeeding) leg inner boundary.
The evaluation for the succeeding segment begins 1 RNP from the turn fix
(example in figure 2-6A) or the angle bisector line (example in figure 2-6B),
whichever is encountered first.
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Page 2-6 Par 2.6.1
Figure 2-6A. Small Turn at a Fly-by Fix
STEP 1
STEP 2
STEP 3
Evaluate 1 RNP
distance from angle
bisector as both segments
±
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Par 2.6.1 Page 2-7
Figure 2-6B. Large Turn at a Fly-by Fix
STEP 1
STEP 2
STEP 3
Evaluate 1 RNP
distance from angle
bisector as both segments
±
2.7 RF LEG SEGMENT.
An RF leg may be designed to accommodate a course change where
obstructions prevent the design of a fly-by turn at a fix, or to accommodate other
operational requirements. RF legs are used to control the ground track of a turn.
The curved leg begins tangent to the previous segment course at its terminating
fix and ends tangent to the follow-on course at its beginning fix (see figure 2-7).
OEA construction limits turn radius to ≥2×RNP. The obstruction evaluation area
boundaries are parallel arcs.
STEP 1. Determine the turn radius (R) necessary to avoid obstructions. Apply
paragraph 1.11.3 to verify the bank angle associated with R is within the
table 1-4 specified values.
STEP 2. Locate the turn center at a perpendicular distance “R” from the
preceding and following segments.
STEP 3. Construct flight path. Scribe an arc of radius “R” from the tangent point
on the preceding course to the tangent point on the following course.
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Page 2-8 Par 2.7
STEP 4. Construct outer OEA boundary. Scribe an arc of radius R+2RNP from
the tangent point on the preceding segment outer boundary to the tangent point
on the following course outer boundary.
STEP 5. Construct inner OEA boundary. Scribe an arc of radius R-2RNP from
the tangent point on the preceding segment inner boundary to the tangent point
on the following course inner boundary.
Figure 2-7. RF Turn Construction
R
R
2 RNP
2 RNP
2 RNP
2 RNP
STEP 2:
Locate Turn Center
STEP 1: Apply para 2.2.
Segment
Initial
Fix
a=R
b=R+(2xRNP)
c=R-(2xRNP)
Segment
Terminating
Fix
Evaluate 1 RNP
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