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

I-4-5-10 Procedures — Aircraft Operations — Volume II
Margin
or
lower limit
Based on operational consideration of:
– category of operation
– ground/airborne equipment characteristics
–crewqualifications
– aircraft performance
– meteorological conditions
– aerodrome characteristics
– terrain profile/radio altimeter
– pressure error/pressure altimeter
– etc. For details see Annex 6.
Margin. The margin is dependent on aircraft
approach speed, height loss and altimetry and is
adjustable for the steep glide paths and high level
aerodromes.
The height of the highest approach obstacle
or of the highest equivalent missed approach
obstacle, whichever is greater.
Note.— Identification of obstacles is dependent
on:
– category of operation
– ILS geometry (glide path angle, distance
from localizer antenna to runway threshold,
reference datum height and localizer course
width)
– aircraft dimensions
– missed approach climb gradient
– missed approach turnpoint
– use of autopilot (CAT II operations only).
23/11/06
PRECISION APPROACH
Decision altitude (DA)
or
Decision height (DH)
Obstacle clearance
altitude (OCA)
or
Obstacle clearance
height (OCH)
Threshold
elevation
Mean sea level
Figure I-4-5-3 a). Relationship of obstacle clearance altitude/height (OCA/H)
to decision altitude/height (DA/H) for precision approaches
This figure does not apply to Category H. See Section 4, Chapter 7.
DH
OCA
OCH
DA
Altitude