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

Chapter 5
DF
5.1 GENERAL
This chapter deals with the specifics of procedures based on a very high frequency direction-finding (VDF) station
located on or close to an aerodrome, that is, within 2 km (1 NM) of the nearest portion of the usable landing surface.
These procedures must incorporate a base turn (see Part I, Section 4, Chapter 3, 3.5.4, “Types of reversal procedures”).
The general criteria in Part I, Sections 1, 2 and 4 apply, as amplified or modified herein.
5.2 DESCENT GRADIENT
The rates of descent in the initial and final approach segments shall be as specified in Part I, Section 4, Chapter 3,
Table I-4-3-1.
5.3 INITIAL APPROACH SEGMENT
5.3.1 General
5.3.1.1 The initial approach fix (IAF) is received by overheading the navigation facility. The initial approach is a
base turn.
5.3.1.2 Time of flight outbound. The time of flight outbound should be limited to the period sufficient to ensure that
the base turn is completed at a distance which permits descent from the base turn altitude/height to the MDA/H
specified.
Note.— The angle between the outbound and inbound tracks is determined by the formula 36/t for Category A and
B and 54/t for Category C, D, and E aircraft, where t is the outbound specified time expressed in minutes. The
outbound track should be sufficient to ensure that at least 2 minutes are allowed inbound to permit proper
establishment of track.
5.3.2 Area
The area is a sector of a circle centred on the navigation facility, symmetrical about the bisector of the inbound and
outbound tracks, with an angle of:
a) 20° + 36/t for Category A and B; and
b) 20° + 54/t for Category C, D and E aircraft,
having a radius D for all aircraft.
II-2-5-1 23/11/06