AIM 

4/20/23

 

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2

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2

Performance

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Based Navigation (PBN) and Area Navigation (RNAV)

(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 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

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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 waypoints 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.