AIM

8/15/19

1

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1

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29

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.

1

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1

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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 Organiza-

tion (ICAO) has defined Standards and
Recommended Practices (SARPs) for satellite

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based

augmentation systems (SBAS) such as WAAS.
Japan, India, and Europe are building similar
systems: EGNOS, the European Geostationary
Navigation Overlay System; India’s GPS and
Geo-Augmented Navigation (GAGAN) system; and
Japan’s Multi-functional Transport Satellite (MT-
SAT)-based Satellite Augmentation System
(MSAS). 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