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

Chapter 3
RNAV T- or Y-BAR PROCEDURE CONSTRUCTION
3.1 GENERAL CONCEPT
3.1.1 Introduction. An RNAV non-precision approach procedure or APV incorporating a T- or Y-bar arrangement
is based on a runway aligned final segment preceded by an intermediate segment and up to three initial segments
arranged either side of and along the final approach track to form a T or a Y (see Figure III-2-3-1 and Figure III-2-3-2).
3.1.2 Capture region. A T- or Y-bar arrangement permits direct entry to the procedure from any direction,
provided entry is made from within the capture region associated with an IAF. A capture region is defined in terms of
an included angle at the IAF (see Figure III-2-3-1 and Figure III-2-3-2).
3.1.3 The lateral initial segments are based on course differences of 70° to 90° from the intermediate segment
track. This arrangement ensures that entry from within a capture region requires a change of course at the IAF not
greater than 110°.
3.1.4 The central initial segment may commence at the IF.
3.1.5 Where one or both offset IAFs are not provided, a direct entry will not be available from all directions. In
such cases a holding pattern may be provided at the IAF to enable entry to the procedure via a procedure turn.
3.1.6 Terminal Arrival Altitudes (TAAs) may be provided to facilitate descent and entry to the procedure. (See
Chapter 4.)
3.1.7 The IAF, IF and FAF are defined by fly-by waypoints. The missed approach segment starts with a flyover
waypoint (MAPt) and ends at a missed approach holding fix (MAHF). For turning missed approaches a missed
approach turning fix (MATF) may also be established to define the turn point.
3.1.8 Area widths are determined in accordance with the tolerances applicable to the navigation system associated
with the procedure.
3.2 INITIAL APPROACH SEGMENT
3.2.1 Alignment. Offset IAFs are located such that a course change of 70° to 90° is required at the IF. The capture
region for tracks inbound to the offset IAF extends 180° about the IAFs, providing a direct entry when the course
change at the IF is 70° or more. The central IAF is normally aligned with the intermediate segment. Its capture region is
70° to 90° either side of the initial segment track, the angle being identical to the course change at the IF for the
corresponding offset IAF. (See Figure III-2-3-1 and Figure III-2-3-2). For turns greater than 110° at the IAFs, Sector 1
or 2 entries should be used (see Figure III-2-3-3).
3.2.2 Length. The initial approach segments have no maximum length. The optimum length is 9.3 km (5.0 NM)
(Cat H, 5.5 km (3.0 NM)). The minimum segment length shall be not less than the distance required by the highest
initial approach speed (see Tables III-2-3-1 and III-2-3-2) for the fastest category of aircraft for which the approach is
III-2-3-1 23/11/06