AIM

8/15/19

1

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2

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2

Performance

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Based Navigation (PBN) and Area Navigation (RNAV)

b. Area Navigation (RNAV)

1. General. 

RNAV is a method of navigation

that permits aircraft operation on any desired flight
path within the coverage of ground

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 or space

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based

navigation aids or within the limits of the capability
of self

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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

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based navigation aids. RNAV 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:

(a)

Time and fuel savings;

(b)

Reduced dependence on radar vectoring,

altitude, and speed assignments allowing a reduction
in required ATC radio transmissions; and

(c)

More efficient use of airspace.

In addition to information found in this manual,
guidance for domestic RNAV DPs, STARs, and
routes may also be found in AC 90

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100, U.S.

Terminal and En Route Area Navigation (RNAV)
Operations.

2. RNAV 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.

(a) Waypoints.

A waypoint is a predeter-

mined 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

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over and fly

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by

waypoints.

(1) Fly

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by waypoints.

Fly

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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.

(2) Fly

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over waypoints.

Fly

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over way-

points are used when the aircraft must fly over the
point prior to starting a turn.

NOTE

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FIG 1

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2

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2 illustrates several differences between a fly

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by

and a fly

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over waypoint.

FIG 1

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2

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2

Fly

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by and Fly

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over Waypoints

(b) RNAV 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

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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.

(1) Track 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

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to

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point legs for this reason.

Narrative:

“direct ALPHA, then on course to

BRAVO WP.”

 See FIG 1

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2

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3.