Aeronautical Information Manual (AIM), page 92

Index   91 -- Page 92 -- 93

Specific inertial position updating requirements may

(d) Flight Management System
(FMS). An FMS is an integrated suite of sensors,
receivers, and computers, coupled with a navigation
database. These systems generally provide perfor-
mance and RNAV guidance to displays and automatic
flight control systems.
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.
(e) RNAV Navigation Specifications (Nav

Nav Specs are a set of aircraft and aircrew
requirements needed to support a navigation
application within a defined airspace concept. For
both RNP and RNAV designations, the numerical
designation refers to the lateral navigation accuracy
in nautical miles which is expected to be achieved at
least 95 percent of the flight time by the population of
aircraft operating within the airspace, route, or
procedure. (See FIG 1-2-1.)
(1) RNAV 1. Typically RNAV 1 is used for
DPs and STARs and appears on the charts. Aircraft
must maintain a total system error of not more than
1 NM for 95 percent of the total flight time.

(2) RNAV 2. Typically RNAV 2 is used for
en route operations unless otherwise specified.

T-routes and Q-routes are examples of this Nav Spec.

Aircraft must maintain a total system error of not

more than 2 NM for 95 percent of the total flight time.

(3) RNAV 10. Typically RNAV 10 is used
in oceanic operations. See paragraph 4-7-1 for
specifics and explanation of the relationship between
RNP 10 and RNAV 10 terminology.

1-2-2. Required Navigation Performance

a. General. RNP is RNAV with onboard naviga-
tion 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 onboard 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
is met.

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 coverage.

b. RNP Operations.
1. Lateral Accuracy Values. Lateral Accuracy
values are applicable to a selected airspace, route, or
procedure. The lateral accuracy value 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 lateral accuracy value (for
example, twice the RNP lateral accuracy values).
(a) Nav Specs and Standard Lateral
Accuracy Values. U.S. standard values supporting
typical RNP airspace are as specified below. Other
lateral accuracy values as identified by ICAO, other
states, and the FAA may also be used. (See
FIG 1-2-1.)

(1) RNP Approach (APCH). RNP APCH

procedures are titled RNAV (GPS) and offer several

lines of minima to accommodate varying levels of

aircraft equipage: either lateral navigation (LNAV),
LNAV/vertical navigation (LNAV/VNAV), and
Localizer Performance with Vertical Guidance
(LPV), or LNAV, and Localizer Performance (LP).
GPS or WAAS can provide the lateral information to

1-2-4 Performance-Based Navigation (PBN) and Area Navigation (RNAV)

Page 92 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

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