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

Chapter 1
MINIMUM LENGTH OF A SEGMENT LIMITED BY
TWO TURNING WAYPOINTS
1.1 GENERAL
1.1.1 To prevent turning waypoints being placed so close that RNAV systems are forced to bypass them, a
minimum distance between successive turning waypoints must be taken into account. Two types of waypoints are
considered:
a) fly-by waypoint; and
b) flyover waypoint.
1.1.2 Four sequences are possible for a segment limited by two waypoints:
a) two fly-by waypoints;
b) fly-by waypoint, then flyover waypoint;
c) two flyover waypoints; and
d) flyover waypoint, then fly-by waypoint.
In addition, the particular case of the segment “DER — first waypoint” must also be considered.
1.1.3 The following method is based on theoretical studies combined with the results of simulations. Some
differences may exist between RNAV systems; algorithms used by these systems are complex. For these reasons,
simplifications were made when establishing theoretical formulae.
1.1.4 The aim of the method is not to determine a protection area, but to determine a minimum distance between
two waypoints on a nominal trajectory. For this reason, wind effect and waypoint tolerances are not taken into account
in the theoretical calculations. When it is necessary, greater values may be chosen.
1.2 DETERMINATION OF THE MINIMUM LENGTH OF THE RNAV SEGMENT
1.2.1 General
For each waypoint a minimum stabilization distance is determined. This is the distance between the waypoint and the
point where the trajectory joins tangentially with the nominal track (Figure III-2-1-1). For successive waypoints, the
minimum distance between them is the sum of both minimum stabilization distances. The tables in this chapter show
minimum stabilization distances for various values of true airspeed and course change (at the waypoint).
III-2-1-1 23/11/06