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

Part II — Section 1, Chapter 3 II-1-3-17
3.5.3.2.3 Areas
3.5.3.2.3.1 Turn initiation area (See Figure II-1-3-18). The turn initiation area is bounded by the 300 m
Category I Y surface contour, and terminates at the TP.
Note.— The earliest TP is considered to be at the beginning of the 300 m Category I Y surface contour (point D”)
unless a fix is specified to limit early turns (see 3.5.3.2.4.2), “Safeguarding of early turns”).
3.5.3.2.3.2 Turn boundary construction. Turn boundaries are constructed as specified in Part I, Section 2,
Chapter 3, “Turn area construction”
3.5.3.2.4 Obstacle clearance
a) Obstacle clearance in the turn initiation area. Obstacle elevation/height in the turn initiation area shall be less
than:
1) turn altitude/height – 50 m (164 ft) for turns more than 15°; and
2) turn altitude/height – 30 m (98 ft) for turns 15° or less,
except that obstacles located under the Y surface on the outer side of the turn need not be considered when
calculating turn altitude/height.
b) Obstacle clearance in the turn area. Obstacle elevation/height in the turn area and subsequently shall be less
than:
turn altitude/height + do tan Z – MOC
where do is measured from the obstacle to the nearest point on the turn initiation area boundary and MOC is:
1) 50 m (164 ft) for turns more than 15°; and
2) 30 m (98 ft) for turns 15° or less,
reducing linearly to zero at the outer edge of the secondary areas, if any.
3.5.3.2.4.1 Turn altitude/height adjustments. If the criteria specified in 3.5.3.2.4, “Obstacle clearance”, above
cannot be met, the turn altitude/height shall be adjusted. This can be done in two ways:
a) adjust turn altitude/height without changing OCA/H: this means that the TP will be moved and the areas
redrawn accordingly; and
b) raise turn altitude/height by increasing OCA/H: this results in a higher turn altitude over the same TP. The turn
areas remain unchanged.
3.5.3.2.4.2 Safeguarding of early turns. Where the published procedure does not specify a fix to limit turns for
aircraft executing a missed approach from above the designated turn altitude/height, an additional check of obstacles
shall be made The general criteria of Part I, Section 4, Chapter 6, 6.4.5.6, “Safeguarding of early turns” and general
principles of Part I, Section 4, Chapter 6, Figure I-4-6-14 apply with the following modifications:
a) the limit of the final approach area is replaced by the line DD” of the OAS surfaces and its extension;
b) the FAF is replaced by the FAP;
23/11/06