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AIM

10/12/17

1−2−4

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

NOTE−

Specific inertial position updating requirements may

apply.

(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.

NOTE−

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

Specs)

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

(RNP)

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