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

Part II — Section 1, Chapter 1 II-1-1-15
1.5.1.3 If obstacles identified in the final missed approach segment result in an increase in any of the OCA/H
calculated for the precision segment, a higher gradient of the missed approach surface (Z) may be specified in addition
if this will provide clearance over those obstacles at a specified lower OCA/H (see Part I, Section 4, Chapter 6, 6.2.3.1,
“Climb gradient in the final phase”).
1.5.2 Straight missed approach
1.5.2.1 General. The precision segment terminates at the point where the Z surface reaches a height 300 m above
threshold. The width of the Z surface at that distance defines the initial width of the final missed approach area which
splays at an angle of 15 degrees from that point, as shown in Figure II-1-1-15. There are no secondary areas.
1.5.2.2 Straight missed approach obstacle clearance. (See Figure II-1-1-16.) Obstacle elevation/height in this
final missed approach area shall be less than
where:
(OCA/Hps –HL)+do tan Z
a) OCA/H of the precision segment (OCA/Hps) and HL (Table II-1-1-2 value) both relate to the same aircraft
category.
b) do is measured from SOC parallel to the straight missed approach track; and
c) Z is the angle of the missed approach surface with the horizontal plane.
If this requirement cannot be met, a turn shall be prescribed to avoid the obstacle in question. If a turn is not practical,
the OCA/H shall be raised.
1.5.3 Turning missed approach
1.5.3.1 General. Turns may be prescribed at a designated turning point (TP), at a designated altitude/height, or “as
soon as practicable”. The criteria used depend on the location of the turn relative to the normal termination of the
precision segment (see 1.4.6, “Termination”) and are as follows:
a) turn after normal termination of the precision segment. If a turn is prescribed after normal termination of the
precision segment, the general criteria of Part I, Section 4, Chapter 6, 6.4.5, “Turn initiated at a designated
altitude/height” and Part I, Section 4, Chapter 6, 6.4.6, “Turn initiated at a designated turning point” apply with
the following exceptions:
1) OCA/H is replaced by (OCA/H – HL) as in 1.5.2.2, “Straight missed approach obstacle clearance”; and
2) because SOC is related to OCA/H, it is not possible to obtain obstacle clearance by the means used in nonprecision
approaches (that is, by independent adjustment of OCA/H or MAPt); and
b) turn before normal termination of the precision segment. If a turn is prescribed at a designated altitude/height
which is less than 300 m above threshold, or at a designated TP such that the earliest TP is within the normal
termination range, the criteria specified in 1.5.3.2 and 1.5.3.3 below shall be applied.
Note.— Adjustments to designated TP location or to the designated turn altitude may involve redrawing the
associated areas and recalculating the clearances. This can exclude some obstacles or introduce new ones. Thus, when
it is necessary to obtain the minimum value of OCA/H – particularly when constraints due to obstacles are very high —
it may be necessary to adjust the designated TP or turn altitude by trial and error. (See Appendix A).
23/11/06