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

Part II — Section 1, Chapter 1 II-1-1-17
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) (Cat H, 40 m (132 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.
1.5.3.2.5 Turn altitude/height adjustments. If the criteria specified in 1.5.3.2.4, “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.
1.5.3.2.6 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;
c) the earliest MAPt is replaced by the line D”D” (earliest limit of the turn initiation area); and
d) if the criterion cannot be met, then the procedure must prohibit turns before a point equivalent to the MAPt and
a note must be added on the profile view of the approach chart.
1.5.3.3 Turn at a designated TP with earliest TP before normal termination of precision segment
1.5.3.3.1 Where a turn is specified at a designated TP, and the earliest TP is before the normal termination range
of the precision segment, the precision segment terminates at the earliest TP. This allows the calculation of OCA/Hps
and (OCA/Hps – HL); SOC is then determined.
1.5.3.3.2 Turn area. The turn area is constructed as specified in Part I, Section 4, Chapter 6, 6.4.6.3, “Construction
of the turn area” except that it is based on the width of the 300 m OAS Y surface contours at the earliest and latest TP
(see Figure II-1-1-18).
1.5.3.3.3 Obstacle clearance. Obstacle elevation/height shall be less than:
(OCA/Hps –HL)+do tan Z – MOC
where: do = dz + shortest distance from obstacle to line K-K,
dz = horizontal distance from SOC to the earliest TP,
23/11/06