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

Chapter 3
TURN AREA CONSTRUCTION
3.1 GENERAL
3.1.1 This chapter describes the general criteria for the construction of turn areas for use in the different segments
of instrument flight procedures. The methodologies presented — wind spiral and bounding circle — apply to the phases
of flight shown below. All other turns are constructed by means of arcs (see the appropriate chapters).
a) Departure.
b) Missed approach.
c) Final approach fix (turns > 10 degrees).
d) RNAV turns at the IAF and IF (turns > 30 degrees).
3.1.2 Turn parameters
3.1.2.1 This section shows the parameters on which the turn areas are based, together with the variables which
represent them in the drawings. The values for the following parameters vary according to the phase of flight. Their
values are listed in Table I-2-3-1, “Turn construction parameter summary”. For the specific application of the
parameters in the table, see the applicable chapters. Tables I-2-3-2 and I-2-3-3 show example calculations of various
turning parameters for a selection of IAS.
a) Altitude.
b) Indicated airspeed (IAS).
c) Wind.
d) Bank angle.
e) Flight technical tolerances.
3.1.2.2 Other turn factors and calculations used in turn construction
a) Fix tolerance. As appropriate for the type of fix. See Section 2, Chapter 2, “Terminal area fixes”. See also
Part II, Section 3, “En-route criteria”.
b) Rate of turn (R) in degrees/second. This is calculated as follows:
1) R = (6 355 tan α)/π V, where V is the TAS in km/h; and
I-2-3-1 23/11/06