Aircraft Operations. Volume II - Construction of Visual and Instrument ...

III-3-2-4 Procedures — Aircraft Operations — Volume II
2.3.2.2 Turn outer boundary
2.3.2.2.1 On the outside of the turn, turn construction starts from the limits of the primary area at the following
distance before the waypoint:
a) r tan (A/2) – ATT – c for turn angles less than or equal to 90 degrees; and
b) r – ATT – c for turn angles more than 90 degrees
where: c is a distance corresponding to a 6-second pilot reaction time
r is the radius of the turn
2.3.2.2.2 From these points wind spirals or bounding circles are constructed as described in Section 2, Chapter 3,
“Turn area construction”, to define the primary area associated with the turn.
2.3.2.2.3 Additionally, in order to protect the aircraft within the required range of speeds, the outer limit of the
primary area is extended until it intersects with that tangent of the wind spiral (or bounding circle) which is parallel to
the nominal track after the turn. After the turn, the primary area is connected to the primary area of the subsequent
segment by a line converging at an angle of 30° with the nominal track after the turn.
2.3.2.2.4 The secondary area has a constant width during the turn.
2.3.2.2.5 If the boundary of the primary or the secondary area associated with the turn remains inside the
corresponding protection area associated with the subsequent segment, then the boundary splays at an angle of 15°
from the nominal track after the turn.
2.3.2.3 Turn inner boundary
On the inner edge of the turn, the primary and the secondary area boundaries start at the K-Line. The edges of the
primary and secondary areas are connected to their counterparts in the subsequent section.
For these connections the following principles apply:
a) if the point to connect is outside the protection area associated with the subsequent segment, then the boundary
converges at an angle of half the angle of turn (A/2) with the nominal track after the turn; and
b) if the point to connect is inside the protection area associated with the subsequent segment then the boundary
diverges from the nominal track at an angle of 15 degrees.
2.3.2.4 Obstacle assessment when descent fix is used
2.3.2.4.1 To assess an obstacle, reference is made to the earliest descent fix.
2.3.2.4.2 Fly-by waypoint. The earliest descent fix is not co-located with the earliest turning point (the K-line).
The earliest descent fix is defined by the intersection of the following two lines:
a) Line N-N’. This line is perpendicular to the inbound track, displaced by a distance ATT before point D (see
Figure III-3-2-5), where
23/11/06
D = the intersection of the bisector of the turn with the nominal track; and
Note.— The perpendicular distance from WP to Line N-N’ is equal to: ATT + r[tan(A/2) – sin(A/2)].