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Navigation Aids

receivers use menus where the pilot selects the

airport, the runway, the specific approach procedure

and finally the IAF, there is also a channel number

selection method. The pilot enters a unique 5−digit

number provided on the approach chart, and the

receiver recalls the matching final approach segment

from the aircraft database. A list of information

including the available IAFs is displayed and the pilot

selects the appropriate IAF. The pilot should confirm

that the correct final approach segment was loaded by

cross checking the Approach ID, which is also

provided on the approach chart.

7. The Along−Track Distance (ATD) during the

final approach segment of an LNAV procedure (with

a minimum descent altitude) will be to the MAWP. On

LNAV/VNAV and LPV approaches to a decision

altitude, there is no missed approach waypoint so the

along−track distance is displayed to a point normally

located at the runway threshold. In most cases, the

MAWP for the LNAV approach is located on the

runway threshold at the centerline, so these distances

will be the same. This distance will always vary

slightly from any ILS DME that may be present, since

the ILS DME is located further down the runway.

Initiation of the missed approach on the LNAV/

VNAV and LPV approaches is still based on reaching

the decision altitude without any of the items listed in

14 CFR Section 91.175 being visible, and must not be

delayed while waiting for the ATD to reach zero. The

WAAS receiver, unlike a GPS receiver, will

automatically sequence past the MAWP if the missed

approach procedure has been designed for RNAV.

The pilot may also select missed approach prior to the

MAWP; however, navigation will continue to the

MAWP prior to waypoint sequencing taking place.

1−1−19. Ground Based Augmentation

System (GBAS) Landing System (GLS)

a. General

1. The GLS provides precision navigation

guidance for exact alignment and descent of aircraft

on approach to a runway. It provides differential

augmentation to the Global Navigation Satellite

System (GNSS).


GBAS is the ICAO term for Local Area Augmentation

System (LAAS).

2. LAAS was developed as an “ILS look−alike”

system from the pilot perspective. LAAS is based on

GPS signals augmented by ground equipment and has

been developed to provide GLS precision approaches

similar to ILS at airfields.

3. GLS provides guidance similar to ILS

approaches for the final approach segment; portions

of the GLS approach prior to and after the final

approach segment will be based on Area Navigation

(RNAV) or Required Navigation Performance


4. The equipment consists of a GBAS Ground

Facility (GGF), four reference stations, a VHF Data

Broadcast (VDB) uplink antenna, and an aircraft

GBAS receiver.

b. Procedure

1. Pilots will select the five digit GBAS channel

number of the associated approach within the Flight

Management System (FMS) menu or manually select

the five digits (system dependent). Selection of the

GBAS channel number also tunes the VDB.

2. Following procedure selection, confirmation

that the correct LAAS procedure is loaded can be

accomplished by cross checking the charted

Reference Path Indicator (RPI) or approach ID with

the cockpit displayed RPI or audio identification of

the RPI with Morse Code (for some systems).

3. The pilot will fly the GLS approach using the

same techniques as an ILS, once selected and


1−1−20. Precision Approach Systems other

than ILS and GLS

a. General

Approval and use of precision approach systems

other than ILS and GLS require the issuance of

special instrument approach procedures.

b. Special Instrument Approach Procedure

1. Special instrument approach procedures

must be issued to the aircraft operator if pilot training,

aircraft equipment, and/or aircraft performance is

different than published procedures. Special instru-

ment approach procedures are not distributed for

general public use. These procedures are issued to an

aircraft operator when the conditions for operations

approval are satisfied.