AIM 

4/20/23

 

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34

Navigation Aids

TBL 1

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1

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6

GPS Approval Required/Authorized Use

Equipment

Type

1

Installation

Approval

Required

Operational

Approval

Required

IFR

En Route

2

IFR

Terminal

2

IFR

Approach

3

Oceanic

Remote

In Lieu of

ADF and/or

DME

3

Hand held

4

X

5

VFR Panel Mount

4

X

IFR En Route

and Terminal

X

X

X

X

X

IFR Oceanic/

Remote

X

X

X

X

X

X

IFR En Route,

Terminal, and

Approach

X

X

X

X

X

X

NOTE

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1

To determine equipment approvals and limitations, refer to the AFM, AFM supplements, or pilot guides.

2

Requires verification of data for correctness if database is expired.

3

Requires current database or verification that the procedure has not been amended since the expiration of the database.

4

VFR and hand

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held GPS systems are not authorized for IFR navigation, instrument approaches, or as a primary instrument

flight reference. During IFR operations they may be considered only an aid to situational awareness.

5

Hand

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held receivers require no approval. However, any aircraft modification to support the hand

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held receiver;

i.e., installation of an external antenna or a permanent mounting bracket, does require approval.

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18. Wide Area Augmentation System (WAAS)

a. General

1.

The FAA developed the WAAS to improve the accuracy, integrity and availability of GPS signals. WAAS

will allow GPS to be used, as the aviation navigation system, from takeoff through approach when it is complete.
WAAS is a critical component of the FAA’s strategic objective for a seamless satellite navigation system for civil
aviation, improving capacity and safety.

2.

The International Civil Aviation Organization (ICAO) has defined Standards and Recommended

Practices (SARPs) for satellite

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based augmentation systems (SBAS) such as WAAS. India and Europe are

building similar systems: EGNOS, the European Geostationary Navigation Overlay System; and India’s GPS
and Geo

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Augmented Navigation (GAGAN) system. The merging of these systems will create an expansive

navigation capability similar to GPS, but with greater accuracy, availability, and integrity.

3.

Unlike traditional ground

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based navigation aids, WAAS will cover a more extensive service area.

Precisely surveyed wide

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area reference stations (WRS) are linked to form the U.S. WAAS network. Signals from

the GPS satellites are monitored by these WRSs to determine satellite clock and ephemeris corrections and to
model the propagation effects of the ionosphere. Each station in the network relays the data to a wide

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area master

station (WMS) where the correction information is computed. A correction message is prepared and uplinked
to a geostationary earth orbit satellite (GEO) via a GEO uplink subsystem (GUS) which is located at the ground
earth station (GES). The message is then broadcast on the same frequency as GPS (L1, 1575.42 MHz) to WAAS
receivers within the broadcast coverage area of the WAAS GEO.

4.

In addition to providing the correction signal, the WAAS GEO provides an additional pseudorange

measurement to the aircraft receiver, improving the availability of GPS by providing, in effect, an additional GPS
satellite in view. The integrity of GPS is improved through real

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time monitoring, and the accuracy is improved

by providing differential corrections to reduce errors. The performance improvement is sufficient to enable
approach procedures with GPS/WAAS glide paths (vertical guidance).

5.

The FAA has completed installation of 3 GEO satellite links, 38 WRSs, 3 WMSs, 6 GES, and the required

terrestrial communications to support the WAAS network including 2 operational control centers. Prior to the