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

I-4-3-2 Procedures — Aircraft Operations — Volume II
23/11/06
3.3 INITIAL APPROACH SEGMENTS (OTHER THAN RADAR VECTORS)
UTILIZING STRAIGHT TRACKS AND DME ARCS
3.3.1 Tracks
The angle of intersection between the initial approach track and the intermediate track should not exceed 120°. When
the angle exceeds 70°, a radial, bearing, radar vector or DME information providing at least 4 km (2 NM) of lead
(Cat H, 1.9 km (1 NM)) shall be identified to assist in leading the turn onto the intermediate track (see Figure I-4-3-1).
When the angle exceeds 120°, the use of a racetrack or reversal procedure or dead reckoning (DR) track should be
considered. Criteria for such procedures are in 3.4, “Initial approach segment using a racetrack procedure”, 3.5, “Initial
approach segment using a reversal procedure” and 3.3.3.3, “Area associated with dead reckoning (DR) track
procedures”.
3.3.2 DME arcs
An arc may provide track guidance for all or for a portion of an initial approach. The minimum arc radius shall be
13 km (7 NM) (Cat H, 9.3 km (5 NM)). An arc may join a track at or before the intermediate fix. When joining a track,
the angle of intersection of the arc and the track should not exceed 120°. When the angle exceeds 70°, a radial which
provides at least 4 km (2 NM) (Cat H, 1.9 km (1 NM)) of lead shall be identified to assist in leading the turn onto the
intermediate track.
3.3.3 Area
3.3.3.1 The initial approach segment has no standard length. The length shall be sufficient to permit the altitude
change required by the procedure. The width is divided into:
a) a primary area which extends laterally 4.6 km (2.5 NM) on each side of the track; and
b) a secondary area which adds an additional 4.6 km (2.5 NM) on each side of the primary area.
(See Figure I-4-3-2.)
3.3.3.2 Area splay
Where, because of an operational requirement, any portion of the initial approach is more than 69 km (37 NM) from the
VOR or 52 km (28 NM) from the NDB providing track guidance, the area will start splaying at these distances at an
angle of 7.8° for VOR or 10.3° for NDB. Within this splayed area, the width of the primary area shall remain one half
of the total width of the area. (See Figure I-4-3-3.) For calculating secondary area width at a given point, see Section 2,
Chapter 1, 1.2.1, “Calculating secondary area width at a given point”.
Note.— See also Appendix B, “Reduction of the width of a straight initial approach area after the IAF and interface
between straight initial approach area and reversal procedure areas” for possible reduction of the width of straight
initial approach area.
3.3.3.3 Area associated with dead reckoning (DR) track procedures
Where DR track procedures are utilized, the area allocated for the turning portions of the dead reckoning segment shall
be calculated to accommodate omnidirectional wind speed (w) derived by the following equation: