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−Based Navigation (PBN) and Area Navigation (RNAV)

(c) Navigation Issues.

Pilots should be

aware of their navigation system inputs, alerts, and
annunciations in order to make better


decisions. In addition, the availability and suitability
of particular sensors/systems should be considered.


Operators using TSO

C129(), TSO

−C196(), TSO−C145() or TSO−C146()

systems should ensure departure and arrival airports
are entered to ensure proper RAIM availability and
CDI sensitivity.

(2) DME/DME.

Operators should be

aware that DME/DME position updating is depen-
dent on navigation system logic and DME facility
proximity, availability, geometry, and signal mask-

(3) VOR/DME.

Unique VOR character-

istics may result in less accurate values from
VOR/DME position updating than from GPS or
DME/DME position updating.

(4) 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

(d) Flight Management System


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


(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.


−2−2. Required Navigation Performance


a. General.

While both RNAV navigation speci-

fications (NavSpecs) and RNP NavSpecs contain
specific performance requirements, RNP is RNAV
with the added requirement for onboard performance
monitoring and alerting (OBPMA). 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. OBPMA capability therefore allows a
lessened reliance on air traffic control intervention
and/or procedural 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 eligible for RNP 1, but may not be capable of
RNP 1 operations due to limited NAVAID coverage


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