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aids or within the limits of the capability of
self−contained aids, or a combination of these. In the
future, there will be an increased dependence on the
use of RNAV in lieu of routes defined by
ground−based navigation aids.
1.2RNAV routes and terminal procedures, including
departure procedures (DPs) and standard terminal
arrivals (STARs), are designed with RNAV systems
in mind. There are several potential advantages of
RNAV routes and procedures:
1.2.1Time and fuel savings,
1.2.2Reduced dependence on radar vectoring,
altitude, and speed assignments allowing a reduction
in required ATC radio transmissions, and
1.2.3More efficient use of airspace.
1.3In addition to information found in this manual,
guidance for domestic RNAV DPs, STARs, and
routes may also be found in Advisory Circular
90−100, U.S. Terminal and En Route Area
Navigation (RNAV) Operations.
1.4RNAV Operations.RNAV procedures, such as
DPs and STARs, demand strict pilot awareness and
maintenance of the procedure centerline. Pilots
should possess a working knowledge of their aircraft
navigation system to ensure RNAV procedures are
flown in an appropriate manner. In addition, pilots
should have an understanding of the various
waypoint and leg types used in RNAV procedures;
these are discussed in more detail below.
1.4.1Waypoints.A waypoint is a predetermined
geographical position that is defined in terms of
latitude/longitude coordinates. Waypoints may be a
simple named point in space or associated with
existing navaids, intersections, or fixes. A waypoint
is most often used to indicate a change in direction,
speed, or altitude along the desired path. RNAV
procedures make use of both fly−over and fly−by
waypoints.
1.4.1.1Fly−by waypoints.Fly−by waypoints are
used when an aircraft should begin a turn to the next
course prior to reaching the waypoint separating the
two route segments. This is known as turn
anticipation.
1.4.1.2Fly−over waypoints.Fly−over waypoints
are used when the aircraft must fly over the point prior
to starting a turn.
NOTE−
FIG ENR 1.18−1 illustrates several differences between a
fly−by and a fly−over waypoint.
FIG ENR 1.18−1
Fly−by and Fly−over Waypoints
1.4.2RNAV Leg Types.A leg type describes the
desired path proceeding, following, or between
waypoints on an RNAV procedure. Leg types are
identified by a two−letter code that describes the path
(e.g., heading, course, track, etc.) and the termination
point (e.g., the path terminates at an altitude, distance,
fix, etc.). Leg types used for procedure design are
included in the aircraft navigation database, but not
normally provided on the procedure chart. The
narrative depiction of the RNAV chart describes how
a procedure is flown. The path and terminator
concept" defines that every leg of a procedure has a
termination point and some kind of path into that
termination point. Some of the available leg types are
described below.
ENR 1.18−2 AIP
15 MAR 07 United States of America
Nineteenth Edition Federal Aviation Administration
1.4.2.1Track to Fix.A Track to Fix (TF) leg is
intercepted and acquired as the flight track to the
following waypoint. Track to a Fix legs are
sometimes called point−to−point legs for this reason.
Narrative:via 087 track to CHEZZ WP."
SeeFIG ENR 1.18−2.
1.4.2.2Direct to Fix.A Direct to Fix (DF) leg is a
path described by an aircraft’s track from an initial
area direct to the next waypoint. Narrative:left
turn direct BARGN WP." See FIG ENR 1.18−3.
NOTE−
FIG ENR 1.18−2, FIG ENR 1.18−3 and FIG ENR 1.18−4
illustrate TF, DF, CF and RF leg types.
FIG ENR 1.18−2
Track to Fix Leg Type
FIG ENR 1.18−3
Direct to Fix Leg Type
AIP ENR 1.18−3
United States of America 15 MAR 07
Federal Aviation Administration Nineteenth Edition
1.4.2.3Course to Fix.A Course to Fix (CF) leg is
a path that terminates at a fix with a specified course
at that fix. Narrative:via 078 course to PRIMY
WP." See FIG ENR 1.18−4.
FIG ENR 1.18−4
Course to Fix Leg Type
1.4.2.4Radius to Fix.A Radius to Fix (RF) leg is
defined as a constant radius circular path around a
defined turn center that terminates at a fix.
See FIG ENR 1.18−5.
FIG ENR 1.18−5
Radius to Fix Leg Type
1.4.2.5Heading.A Heading leg may be defined as,
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