Section 2. Area Navigation (RNAV) and Required
Navigation Performance (RNP)
1-2-1. Area Navigation (RNAV)
a. General. RNAV is a method of navigation that
permits aircraft operation on any desired flight path
within the coverage of ground or space based
navigation 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.
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:
1. Time and fuel savings,
2. Reduced dependence on radar vectoring,
altitude, and speed assignments allowing a reduction
in required ATC radio transmissions, and
3. 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 Advisory Circular 90-100A, U.S. Terminal and En Route Area
Navigation (RNAV) Operations.
b. 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.
1. 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-over and fly-by
(a) Fly-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
(b) Fly-over waypoints. Fly-over waypoints are used when the aircraft must fly over the
point prior to starting a turn.
FIG 1-2-1 illustrates several differences between a fly-by
and a fly-over waypoint.
Fly-by and Fly-over Waypoints
2. 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-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
(a) 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-to-point legs for this reason.
Narrative: “on track 087 to CHEZZ WP.” See
(b) Direct 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 1-2-3.
Track to Fix Leg Type
Direct to Fix Leg Type
(c) Course to Fix. A Course to Fix (CF) leg
is a path that terminates at a fix with a specified course
at that fix. Narrative: “on course 078 to PRIMY
WP.” See FIG 1-2-4.
Course to Fix Leg Type
(d) Radius 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
Radius to Fix Leg Type
(e) Heading. A Heading leg may be defined
as, but not limited to, a Heading to Altitude (VA),
Heading to DME range (VD), and Heading to Manual
Termination, i.e., Vector (VM). Narrative: “climb
heading 350 to 1500”, “heading 265, at 9 DME west
of PXR VORTAC, right turn heading 360”, “fly
heading 090, expect radar vectors to DRYHT INT.”
3. Navigation Issues. Pilots should be aware
of their navigation system inputs, alerts, and
annunciations in order to make better-informed
decisions. In addition, the availability and suitability
of particular sensors/systems should be considered.
(a) GPS. Operators using TSO-C129 systems should ensure departure and arrival airports are
entered to ensure proper RAIM availability and CDI
(b) DME/DME. Operators should be aware
that DME/DME position updating is dependent on
FMS logic and DME facility proximity, availability,
geometry, and signal masking.
(c) VOR/DME. Unique VOR characteristics may result in less accurate values from
VOR/DME position updating than from GPS or
DME/DME position updating.
(d) Inertial Navigation. Inertial reference
units and inertial navigation systems are often
coupled with other types of navigation inputs,
e.g., DME/DME or GPS, to improve overall
navigation system performance.
Specific inertial position updating requirements may
4. Flight Management System (FMS). An
FMS is an integrated suite of sensors, receivers, and
computers, coupled with a navigation database.
These systems generally provide performance and
RNAV guidance to displays and automatic flight
Inputs can be accepted from multiple sources such as
GPS, DME, VOR, LOC and IRU. These inputs may
be applied to a navigation solution one at a time or in
combination. Some FMSs provide for the detection
and isolation of faulty navigation information.
When appropriate navigation signals are available,
FMSs will normally rely on GPS and/or DME/DME
(that is, the use of distance information from two or
more DME stations) for position updates. Other
inputs may also be incorporated based on FMS
system architecture and navigation source geometry.
DME/DME inputs coupled with one or more IRU(s) are
often abbreviated as DME/DME/IRU or D/D/I.
1-2-2. Required Navigation Performance
a. General. RNP is RNAV with on-board
navigation monitoring and alerting, RNP is also a
statement of navigation performance necessary for
operation within a defined airspace. A critical
component of RNP is the ability of the aircraft
navigation system to monitor its achieved navigation
performance, and to identify for the pilot whether the
operational requirement is, or is not being met during
an operation. This on-board performance monitoring and alerting capability therefore allows a lessened
reliance on air traffic control intervention (via radar
monitoring, automatic dependent surveillance
(ADS), multilateration, communications), and/or
route separation to achieve the overall safety of the
operation. RNP capability of the aircraft is a major
component in determining the separation criteria to
ensure that the overall containment of the operation
The RNP capability of an aircraft will vary depending
upon the aircraft equipment and the navigation
infrastructure. For example, an aircraft may be
equipped and certified for RNP 1.0, but may not be
capable of RNP 1.0 operations due to limited navaid
b. RNP Operations.
1. RNP Levels. An RNP “level” or “type” is
applicable to a selected airspace, route, or procedure.
As defined in the Pilot/Controller Glossary, the RNP
Level or Type is a value typically expressed as a
distance in nautical miles from the intended
centerline of a procedure, route, or path. RNP
applications also account for potential errors at some
multiple of RNP level (e.g., twice the RNP level).
(a) Standard RNP Levels. U.S. standard
values supporting typical RNP airspace are as
specified in TBL 1-2-1 below. Other RNP levels as
identified by ICAO, other states and the FAA may
also be used.
(b) Application of Standard RNP Levels. U.S. standard levels of RNP typically used for
various routes and procedures supporting RNAV
operations may be based on use of a specific
navigational system or sensor such as GPS, or on
multi-sensor RNAV systems having suitable performance.
(c) Depiction of Standard RNP Levels. The
applicable RNP level will be depicted on affected
charts and procedures.
U.S. Standard RNP Levels
Primary Route Width (NM) -
Centerline to Boundary
0.1 to 1.0
RNP AR Approach Segments
0.1 to 1.0
0.3 to 1.0
RNP Approach Segments
0.3 to 1.0
Terminal and En Route
1. The “performance” of navigation in RNP refers not only to the level of accuracy of a particular sensor or aircraft
navigation system, but also to the degree of precision with which the aircraft will be flown.
2. Specific required flight procedures may vary for different RNP levels.
RNP Levels Supported for International Operations
Projected for oceanic/remote areas where 30 NM horizontal separation is applied
Oceanic/remote areas where 50 NM lateral separation is applied
c. Other RNP Applications Outside the U.S.
The FAA and ICAO member states have led
initiatives in implementing the RNP concept to
oceanic operations. For example, RNP-10 routes
have been established in the northern Pacific
(NOPAC) which has increased capacity and
efficiency by reducing the distance between tracks
to 50 NM. (See TBL 1-2-2.)
d. Aircraft and Airborne Equipment Eligibility
for RNP Operations. Aircraft meeting RNP criteria
will have an appropriate entry including special
conditions and limitations in its Aircraft Flight
Manual (AFM), or supplement. Operators of aircraft
not having specific AFM-RNP certification may be
issued operational approval including special conditions and limitations for specific RNP levels.
Some airborne systems use Estimated Position Uncertainty (EPU) as a measure of the current estimated
navigational performance. EPU may also be referred to as
Actual Navigation Performance (ANP) or Estimated
Position Error (EPE).
1-2-3. Use of Suitable Area Navigation
(RNAV) Systems on Conventional
Procedures and Routes
a. Discussion. This paragraph sets forth policy,
while providing operational and airworthiness
guidance regarding the suitability and use of RNAV
systems when operating on, or transitioning to,
conventional, non-RNAV routes and procedures
within the U.S. National Airspace System (NAS):
1. Use of a suitable RNAV system as a
Substitute Means of Navigation when a Very-High
Frequency (VHF) Omni-directional Range (VOR),
Distance Measuring Equipment (DME), Tactical Air
Navigation (TACAN), VOR/TACAN (VORTAC),
VOR/DME, Non-directional Beacon (NDB), or
compass locator facility including locator outer
marker and locator middle marker is out-of-service
(that is, the navigation aid (NAVAID) information is
not available); an aircraft is not equipped with an
Automatic Direction Finder (ADF) or DME; or the
installed ADF or DME on an aircraft is not
operational. For example, if equipped with a suitable
RNAV system, a pilot may hold over an out-of-service NDB.
2. Use of a suitable RNAV system as an
Alternate Means of Navigation when a VOR, DME,
VORTAC, VOR/DME, TACAN, NDB, or compass
locator facility including locator outer marker and
locator middle marker is operational and the
respective aircraft is equipped with operational
navigation equipment that is compatible with
conventional navaids. For example, if equipped with
a suitable RNAV system, a pilot may fly a procedure
or route based on operational VOR using that RNAV
system without monitoring the VOR.
1. Additional information and associated requirements
are available in Advisory Circular 90108 titled “Use of
Suitable RNAV Systems on Conventional Routes and
2. Good planning and knowledge of your RNAV system are
critical for safe and successful operations.
3. Pilots planning to use their RNAV system as a substitute
means of navigation guidance in lieu of an out-of-service
NAVAID may need to advise ATC of this intent and
4. The navigation database should be current for the
duration of the flight. If the AIRAC cycle will change
during flight, operators and pilots should establish
procedures to ensure the accuracy of navigation data,
including suitability of navigation facilities used to define
the routes and procedures for flight. To facilitate validating
database currency, the FAA has developed procedures for
publishing the amendment date that instrument approach
procedures were last revised. The amendment date follows
the amendment number, e.g., Amdt 4 14Jan10. Currency of
graphic departure procedures and STARs may be
ascertained by the numerical designation in the procedure
title. If an amended chart is published for the procedure, or
the procedure amendment date shown on the chart is on or
after the expiration date of the database, the operator must
not use the database to conduct the operation.
b. Types of RNAV Systems that Qualify as a
Suitable RNAV System. When installed in accordance with appropriate airworthiness installation
requirements and operated in accordance with
applicable operational guidance (e.g., aircraft flight
manual and Advisory Circular material), the
following systems qualify as a suitable RNAV
1. An RNAV system with TSO-C129/
-C145/-C146 equipment, installed in accordance
with AC 20-138, Airworthiness Approval of Global
Positioning System (GPS) Navigation Equipment for
Use as a VFR and IFR Supplemental Navigation
System, or AC 20-130A, Airworthiness Approval of
Navigation or Flight Management Systems Integrating Multiple Navigation Sensors, and authorized for
instrument flight rules (IFR) en route and terminal
operations (including those systems previously
qualified for “GPS in lieu of ADF or DME”
2. An RNAV system with DME/DME/IRU
inputs that is compliant with the equipment
provisions of AC 90-100A, U.S. Terminal and
En Route Area Navigation (RNAV) Operations, for
RNAV routes. A table of compliant equipment is
available at the following website:
Approved RNAV systems using DME/DME/IRU, without
GPS/WAAS position input, may only be used as a substitute
means of navigation when specifically authorized by a
Notice to Airmen (NOTAM) or other FAA guidance for a
specific procedure. The NOTAM or other FAA guidance
authorizing the use of DME/DME/IRU systems will also
identify any required DME facilities based on an FAA
assessment of the DME navigation infrastructure.
c. Uses of Suitable RNAV Systems. Subject to
the operating requirements, operators may use a
suitable RNAV system in the following ways.
1. Determine aircraft position relative to, or
distance from a VOR (see NOTE 5 below), TACAN,
NDB, compass locator, DME fix; or a named fix
defined by a VOR radial, TACAN course, NDB
bearing, or compass locator bearing intersecting a
VOR or localizer course.
2. Navigate to or from a VOR, TACAN, NDB,
or compass locator.
3. Hold over a VOR, TACAN, NDB, compass
locator, or DME fix.
4. Fly an arc based upon DME.
1. The allowances described in this section apply even
when a facility is identified as required on a procedure (for
example, “Note ADF required”).
2. These operations do not include lateral navigation on
localizer-based courses (including localizer back-course
guidance) without reference to raw localizer data.
3. Unless otherwise specified, a suitable RNAV system
cannot be used for navigation on procedures that are
identified as not authorized (“NA”) without exception by
a NOTAM. For example, an operator may not use a RNAV
system to navigate on a procedure affected by an expired or
unsatisfactory flight inspection, or a procedure that is
based upon a recently decommissioned NAVAID.
4. Pilots may not substitute for the NAVAID (for example,
a VOR or NDB) providing lateral guidance for the final
approach segment. This restriction does not refer to
instrument approach procedures with “or GPS” in the title
when using GPS or WAAS. These allowances do not apply
to procedures that are identified as not authorized (NA)
without exception by a NOTAM, as other conditions may
still exist and result in a procedure not being available. For
example, these allowances do not apply to a procedure
associated with an expired or unsatisfactory flight
inspection, or is based upon a recently decommissioned
5. For the purpose of paragraph c, “VOR” includes VOR,
VOR/DME, and VORTAC facilities and “compass
locator” includes locator outer marker and locator middle
d. Alternate Airport Considerations. For the
purposes of flight planning, any required alternate
airport must have an available instrument approach
procedure that does not require the use of GPS. This
restriction includes conducting a conventional
approach at the alternate airport using a substitute
means of navigation that is based upon the use of
GPS. For example, these restrictions would apply
when planning to use GPS equipment as a substitute
means of navigation for an out-of-service VOR that
supports an ILS missed approach procedure at an
alternate airport. In this case, some other approach
not reliant upon the use of GPS must be available.
This restriction does not apply to RNAV systems
using TSO-C145/-C146 WAAS equipment. For
further WAAS guidance see AIM 1-1-20.