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

Part II — Section 1, Chapter 1, Appendix A II-1-1-App A-3
MOC is the margin applicable to turns (in metres) and
d (in metres) = distance (threshold to TP) + do
In the case of a turn at an altitude:
do is the shortest distance from obstacle to the turn initiation area boundary and
d = distance (threshold to earliest TP) + do
InthecaseofturnatadesignatedTP:
do is the shortest distance from the obstacle to the earliest TP (line K-K).
3.2 Calculation of OCH from an amount of
altitude missing above an obstacle
This method is applicable whenever it has been established that one obstacle is a problem. This means that the nominal
altitude above the obstacle will not be adequate for an airplane climbing at the SOC from the previously calculated
OCH. If we express the difference in altitude as dif (alt), the necessary increase of OCH (dif (OCH)) will be obtained
by the formula:
dif (OCH) =
dif (alt) cot Z
cot Z + cot θ
This method may also be applied for turns at altitude, when an obstacle in the turn initiation area is higher than (turn
altitude – MOC). Then the necessary increase of OCH (see 2.1.3, “Obstacle in the turn initiation area”, item b)) will be
obtained by the formula above where:
dif (alt) = obstacle elevation + MOC – previous turn altitude.
4. TECHNIQUE FOR REDUCTION OF THE TURN AREA FOR A TURN AT
AN ALTITUDE FROM INSIDE THE PRECISION SEGMENT
4.1 Turn initiation area
The turn initiation area can be more precisely defined by plotting an area which consists of two parts. The first part is
the area enclosed by the turn altitude OAS contour truncated at the turn point as described in Chapter 1, 1.5.3.2.1. The
second part of the area is bounded by:
a) the 300 m OAS contour truncated by the line joining the D” points; and
b) two lines DTL defined as follows:
DT = (HL – RDH) cot θ + 900 m SI units
where DT is the distance from a missed approach point on GP to the corresponding SOC on GP'.
23/11/06