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Performance−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−informed

decisions. In addition, the availability and suitability

of particular sensors/systems should be considered.

(1) GPS/WAAS. 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

(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. 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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