JEPPESEN GENERAL AIRWAY MANUAL (Issue Date 1 JUL 21)

d. Usable off-course indications are limited to 35 degrees either side of the course centerline.

Instrument indications received beyond 35 degrees should be disregarded.

e. The SDF antenna may be offset from the runway centerline. Because of this, the angle of

convergence between the final approach course and the runway bearing should be deter-
mined by reference to the instrument approach procedure chart. This angle is generally not
more than 3 degrees. However, it should be noted that inasmuch as the approach course
originates at the antenna site, an approach which is continued beyond the runway threshold
will lead the aircraft to the SDF offset position rather than along the runway centerline.

f. The SDF signal is fixed at either 6 degrees or 12 degrees as necessary to provide maximum

flyability and optimum course quality.

g. Identification consists of a three-letter identifier transmitted in Morse Code on the SDF fre-

quency. The appropriate instrument approach chart will indicate the identifier used at a par-
ticular airport.

NAVAID IDENTIFIER REMOVAL DURING MAINTENANCE

During periods of routine or emergency maintenance, coded identification (or code and voice,
where applicable) is removed from certain FAA NAVAIDs. Removal of identification serves as a
warning to pilots that the facility is officially off the air for tune-up or repair and may be unreliable
even though intermittent or constant signals are received.
NOTE: During periods of maintenance VHF ranges may radiate a T-E-S-T code (– • ••• –).
NOTE: DO NOT attempt to fly a procedure that is NOTAMed out of service even if the identifica-
tion is present. In certain cases, the identification may be transmitted for short periods as part of
the testing.

NAVAIDS WITH VOICE

a. Voice equipped en route radio navigational aids are under the operational control of either a

Flight Service Station (FSS) or an approach control facility. Facilities with two-way voice
communication available are indicated in the Chart Supplement U.S. and aeronautical
charts.

b. Unless otherwise noted on the chart, all radio navigation aids operate continuously except

during shutdowns for maintenance. Hours of operation of facilities not operating continuously
are annotated on charts and in the Chart Supplement U.S.

USER REPORTS REQUESTED ON NAVAID OR GLOBAL

NAVIGATION SATELLITE SYSTEM (GNSS) PERFORMANCE

OR INTERFERENCE

a. Users of the National Airspace System (NAS) can render valuable assistance in the early

correction of NAVAID malfunctions or GNSS problems and are encouraged to report their
observations of undesirable avionics performance. Although NAVAIDs are monitored by
electronic detectors, adverse effects of electronic interference, new obstructions, or changes
in terrain near the NAVAID can exist without detection by the ground monitors. Some of the

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characteristics of malfunction or deteriorating performance which should be reported are:
erratic course or bearing indications; intermittent, or full, flag alarm; garbled, missing or obvi-
ously improper coded identification; poor quality communications reception; or, in the case of
frequency interference, an audible hum or tone accompanying radio communications or
NAVAID identification. GNSS problems are often characterized by navigation degradation or
service loss indications. For instance, pilots conducting operations in areas where there is
GNSS interference may be unable to use GPS for navigation, and ADS-B may be unavaila-
ble for surveillance. Radio frequency interference may affect both navigation for the pilot and
surveillance by the air traffic controller. Depending on the equipment and integration, either
an advisory light or message may alert the pilot. Air traffic controllers monitoring ADS-B
reports may stop receiving ADS-B position messages and associated aircraft tracks.
In addition, malfunctioning, faulty, inappropriately installed, operated, or modified GPS re-
radiator systems, intended to be used for aircraft maintenance activities, have resulted in
unintentional disruption of aviation GNSS receivers. This type of disruption could result in un-
flagged, erroneous position information output to primary flight displays/indicators and to
other aircraft and air traffic control systems. Since receiver autonomous integrity monitoring
(RAIM) is only partially effective against this type of disruption (effectively a “signal spoof-
ing”), the pilot may not be aware of any erroneous navigation indications; ATC may be the
only means available for identification of these disruptions and detect unexpected aircraft
position while monitoring aircraft for IFR separation.

b. Pilots reporting potential interference should identify the NAVAID (for example, VOR) mal-

function or GNSS problem, location of the aircraft (that is, latitude, longitude or bearing/
distance from a reference NAVAID), magnetic heading, altitude, date and time of the obser-
vation, type of aircraft (make/model/call sign), and description of the condition observed, and
the type of receivers in use (that is, make/model/software revision). Reports should be made
in any of the following ways:

1. Immediately, by voice radio communication to the controlling ATC facility or FSS.
2. By telephone to the nearest ATC facility controlling the airspace where the disruption

was experienced.

3. Additionally, GNSS problems should be reported by Internet via the GPS Anomaly

Reporting Form at

http://www.faa.gov/air_traffic/nas/gps_reports/.

c. In aircraft equipped with more than one avionics receiver, there are many combinations of

potential interference between units that could cause erroneous navigation indications, or
complete or partial blanking out of the display.
NOTE: GPS interference or outages associated with known testing NOTAMs should not be
reported to ATC.

LORAN

NOTE: In accordance with the 2010 DHS Appropriations Act, the U.S. Coast Guard (USCG) ter-
minated the transmission of all U.S. LORAN-C signals on 08 Feb 2010. The USCG also termina-
ted the transmission of the Russian American signals on 01 Aug 2010, and the Canadian

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LORAN-C signals on 03 Aug 2010. For more information, visit

http://www.navcen.uscg.gov.

Operators should also note that TSO-C60b, AIRBORNE AREA NAVIGATION EQUIPMENT
USING LORAN-C INPUTS, has been canceled by the FAA.

INERTIAL REFERENCE UNIT (IRU), INERTIAL NAVIGATION

SYSTEM (INS), AND ATTITUDE HEADING REFERENCE

SYSTEM (AHRS)

a. IRUs are self-contained systems comprised of gyros and accelerometers that provide aircraft

attitude (pitch, roll, and heading), position, and velocity information in response to signals
resulting from inertial effects on system components. Once aligned with a known position,
IRUs continuously calculate position and velocity. IRU position accuracy decays with time.
This degradation is known as “drift.”

b. INSs combine the components of an IRU with an internal navigation computer. By program-

ming a series of waypoints, these systems will navigate along a predetermined track.

c. AHRSs are electronic devices that provide attitude information to aircraft systems such as

weather radar and autopilot, but do not directly compute position information.

d. Aircraft equipped with slaved compass systems may be susceptible to heading errors

caused by exposure to magnetic field disturbances (flux fields) found in materials that are
commonly located on the surface or buried under taxiways and ramps. These materials gen-
erate a magnetic flux field that can be sensed by the aircraft’s compass system flux detector
or “gate”, which can cause the aircraft’s system to align with the material’s magnetic field
rather than the earth’s natural magnetic field. The system’s erroneous heading may not self-
correct. Prior to take off pilots should be aware that a heading misalignment may have occur-
red during taxi. Pilots are encouraged to follow the manufacturer’s or other appropriate pro-
cedures to correct possible heading misalignment before take off is commenced.

DOPPLER RADAR

Doppler Radar is a semiautomatic self-contained dead reckoning navigation system (radar sensor
plus computer) which is not continuously dependent on information derived from ground based or
external aids. The system employs radar signals to detect and measure ground speed and drift
angle, using the aircraft compass system as its directional reference. Doppler is less accurate
than INS, however, and the use of an external reference is required for periodic updates if accept-
able position accuracy is to be achieved on long range flights.

GLOBAL POSITIONING SYSTEM (GPS)

System Overview

1. System Description. The Global Positioning System is a space-based radio navigation

system used to determine precise position anywhere in the world. The 24 satellite con-
stellation is designed to ensure at least five satellites are always visible to a user world-
wide. A minimum of four satellites is necessary for receivers to establish an accurate
three-dimensional position. The receiver uses data from satellites above the mask angle
(the lowest angle above the horizon at which a receiver can use a satellite). The Depart-

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ment of Defense (DOD) is responsible for operating the GPS satellite constellation and
monitors the GPS satellites to ensure proper operation. Each satellite’s orbital parame-
ters (ephemeris data) are sent to each satellite for broadcast as part of the data mes-
sage embedded in the GPS signal. The GPS coordinate system is the Cartesian earth-
centered, earth-fixed coordinates as specified in the World Geodetic System 1984
(WGS-84).

2. System Availability and Reliability

(a) The status of GPS satellites is broadcast as part of the data message transmitted

by the GPS satellites. GPS status information is also available by means of the
U.S. Coast Guard navigation information service: (703) 313-5907, Internet:

http://

www.navcen.uscg.gov/. Additionally, satellite status is available through the
Notice to Airmen (NOTAM) system.

(b) GNSS operational status depends on the type of equipment being used. For GPS-

only equipment TSO-C129 or TSO-C196(), the operational status of non-precision
approach capability for flight planning purposes is provided through a prediction
program that is embedded in the receiver or provided separately.

3. Receiver Autonomous Integrity Monitoring (RAIM). RAIM is the capability of a GPS

receiver to perform integrity monitoring on itself by ensuring available satellite signals
meet the integrity requirements for a given phase of flight. Without RAIM, the pilot has
no assurance of the GPS position integrity. RAIM provides immediate feedback to the
pilot. This fault detection is critical for performance-based navigation (PBN) (see Para-
graph 1-2-1, Performance-Based Navigation (PBN) and Area Navigation (RNAV), for an
introduction to PBN), because delays of up to two hours can occur before an erroneous
satellite transmission is detected and corrected by the satellite control segment.

(a) In order for RAIM to determine if a satellite is providing corrupted information, at

least one satellite, in addition to those required for navigation, must be in view for
the receiver to perform the RAIM function. RAIM requires a minimum of 5 satel-
lites, or 4 satellites and barometric altimeter input (baro-aiding), to detect an integ-
rity anomaly. Baro-aiding is a method of augmenting the GPS integrity solution by
using a non-satellite input source in lieu of the fifth satellite. Some GPS receivers
also have a RAIM capability, called fault detection and exclusion (FDE), that
excludes a failed satellite from the position solution; GPS receivers capable of FDE
require 6 satellites or 5 satellites with baro-aiding. This allows the GPS receiver to
isolate the corrupt satellite signal, remove it from the position solution, and still pro-
vide an integrity-assured position. To ensure that baro-aiding is available, enter the
current altimeter setting into the receiver as described in the operating manual. Do
not use the GPS derived altitude due to the large GPS vertical errors that will make
the integrity monitoring function invalid.

(b) There are generally two types of RAIM fault messages. The first type of message

indicates that there are not enough satellites available to provide RAIM integrity
monitoring. The GPS navigation solution may be acceptable, but the integrity of
the solution cannot be determined. The second type indicates that the RAIM integ-

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rity monitor has detected a potential error and that there is an inconsistency in the
navigation solution for the given phase of flight. Without RAIM capability, the pilot
has no assurance of the accuracy of the GPS position.

4. Selective Availability. Selective Availability (SA) is a method by which the accuracy of

GPS is intentionally degraded. This feature was designed to deny hostile use of precise
GPS positioning data. SA was discontinued on May 1, 2000, but many GPS receivers
are designed to assume that SA is still active. New receivers may take advantage of the
discontinuance of SA based on the performance values in ICAO Annex 10.

Operational Use of GPS U.S. civil operators may use approved GPS equipment in oceanic
airspace, certain remote areas, the National Airspace System and other States as authorized
(please consult the applicable Aeronautical Information Publication). Equipage other than
GPS may be required for the desired operation. GPS navigation is used for both Visual Flight
Rules (VFR) and Instrument Flight Rules (IFR) operations.

VFR Operations

(a) GPS navigation has become an asset to VFR pilots by providing increased naviga-

tional capabilities and enhanced situational awareness. Although GPS has provi-
ded many benefits to the VFR pilot, care must be exercised to ensure that system
capabilities are not exceeded. VFR pilots should integrate GPS navigation with
electronic navigation (when possible), as well as pilotage and dead reckoning.

(b) GPS receivers used for VFR navigation vary from fully integrated IFR/VFR installa-

tion used to support VFR operations to hand-held devices. Pilots must understand
the limitations of the receivers prior to using in flight to avoid misusing navigation
information. (See TBL 1-1-6.) Most receivers are not intuitive. The pilot must learn
the various keystrokes, knob functions, and displays that are used in the operation
of the receiver. Some manufacturers provide computer-based tutorials or simula-
tions of their receivers that pilots can use to become familiar with operating the
equipment.

antenna location are critical areas of concern.

(1) RAIM Capability. VFR GPS panel mount receivers and hand-held units have

no RAIM alerting capability. This prevents the pilot from being alerted to the
loss of the required number of satellites in view, or the detection of a position
error. Pilots should use a systematic cross-check with other navigation techni-
ques to verify position. Be suspicious of the GPS position if a disagreement
exists between the two positions.

(2) Database Currency. Check the currency of the database. Databases must be

updated for IFR operations and should be updated for all other operations.
However, there is no requirement for databases to be updated for VFR navi-
gation. It is not recommended to use a moving map with an outdated data-
base in and around critical airspace. Pilots using an outdated database

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should verify waypoints using current aeronautical products; for example,
Chart Supplement U.S., Sectional Chart, or En Route Chart.

(3) Antenna Location. The antenna location for GPS receivers used for IFR and

VFR operations may differ. VFR antennae are typically placed for conven-
ience more than performance, while IFR installations ensure a clear view is
provided with the satellites. Antennae not providing a clear view have a
greater opportunity to lose the satellite navigational signal. This is especially
true in the case of hand-held GPS receivers. Typically, suction cups are used
to place the GPS antennas on the inside of cockpit windows. While this
method has great utility, the antenna location is limited to the cockpit or cabin
which rarely provides a clear view of all available satellites. Consequently,
signal losses may occur due to aircraft structure blocking satellite signals,
causing a loss of navigation capability. These losses, coupled with a lack of
RAIM capability, could present erroneous position and navigation information
with no warning to the pilot. While the use of a hand-held GPS for VFR opera-
tions is not limited by regulation, modification of the aircraft, such as installing
a panel- or yoke-mounted holder, is governed by 14 CFR Part 43. Consult
with your mechanic to ensure compliance with the regulation and safe instal-
lation.

(d) Do not solely rely on GPS for VFR navigation. No design standard of accuracy or

integrity is used for a VFR GPS receiver. VFR GPS receivers should be used in
conjunction with other forms of navigation during VFR operations to ensure a cor-
rect route of flight is maintained. Minimize head-down time in the aircraft by being
familiar with your GPS receiver’s operation and by keeping eyes outside scanning
for traffic, terrain, and obstacles.

(e)

VFR Waypoints

(1) VFR waypoints provide VFR pilots with a supplementary tool to assist with

position awareness while navigating visually in aircraft equipped with area
navigation receivers. VFR waypoints should be used as a tool to supplement
current navigation procedures. The uses of VFR waypoints include providing
navigational aids for pilots unfamiliar with an area, waypoint definition of exist-
ing reporting points, enhanced navigation in and around Class B and Class C
airspace, and enhanced navigation around Special Use Airspace. VFR pilots
should rely on appropriate and current aeronautical charts published specifi-
cally for visual navigation. If operating in a terminal area, pilots should take
advantage of the Terminal Area Chart available for that area, if published.
The use of VFR waypoints does not relieve the pilot of any responsibility to
comply with the operational requirements of 14 CFR Part 91.

(2) VFR waypoint names (for computer-entry and flight plans) consist of five let-

ters beginning with the letters “VP” and are retrievable from navigation data-
bases. The VFR waypoint names are not intended to be pronounceable, and
they are not for use in ATC communications. On VFR charts, stand-alone

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VFR waypoints will be portrayed using the same four-point star symbol used
for IFR waypoints. VFR waypoints collocated with visual check points on the
chart will be identified by small magenta flag symbols. VFR waypoints collo-
cated with visual check points will be pronounceable based on the name of
the visual check point and may be used for ATC communications. Each VFR
waypoint name will appear in parentheses adjacent to the geographic location
on the chart. Latitude/longitude data for all established VFR waypoints may
be found in the appropriate regional Chart Supplement U.S.

(3) VFR waypoints may not be used on IFR flight plans. VFR waypoints are not

recognized by the IFR system and will be rejected for IFR routing purposes.

(4) Pilots may use the five-letter identifier as a waypoint in the route of flight sec-

tion on a VFR flight plan. Pilots may use the VFR waypoints only when oper-
ating under VFR conditions. The point may represent an intended course
change or describe the planned route of flight. This VFR filing would be simi-
lar to how a VOR would be used in a route of flight.

(5) VFR waypoints intended for use during flight should be loaded into the

receiver while on the ground. Once airborne, pilots should avoid programming
routes or VFR waypoint chains into their receivers.

(6) Pilots should be vigilant to see and avoid other traffic when near VFR way-

points. With the increased use of GPS navigation and accuracy, expect
increased traffic near VFR waypoints. Regardless of the class of airspace,
monitor the available ATC frequency for traffic information on other aircraft
operating in the vicinity. See Paragraph 7-5-2, VFR in Congested Areas, for
more information.

IFR Use of GPS

(a)

General Requirements. Authorization to conduct any GPS operation under IFR
requires:

(1) GPS navigation equipment used for IFR operations must be approved in

accordance with the requirements specified in Technical Standard Order
(TSO) TSO-C129(), TSO-C196(), TSO-C145(), or TSO-C146(), and the instal-
lation must be done in accordance with Advisory Circular AC 20-138, Airwor-
thiness Approval of Positioning and Navigation Systems. Equipment
approved in accordance with TSO-C115a does not meet the requirements of
TSO-C129. Visual flight rules (VFR) and hand-held GPS systems are not
authorized for IFR navigation, instrument approaches, or as a principal instru-
ment flight reference.

(2) Aircraft using un-augmented GPS (TSO-C129() or TSO-C196()) for naviga-

tion under IFR must be equipped with an alternate approved and operational
means of navigation suitable for navigating the proposed route of flight.
(Examples of alternate navigation equipment include VOR or DME/DME/IRU
capability). Active monitoring of alternative navigation equipment is not

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required when RAIM is available for integrity monitoring. Active monitoring of
an alternate means of navigation is required when the GPS RAIM capability is
lost.

(3) Procedures must be established for use in the event that the loss of RAIM

capability is predicted to occur. In situations where RAIM is predicted to be
unavailable, the flight must rely on other approved navigation equipment, re-
route to where RAIM is available, delay departure, or cancel the flight.

(4) The GPS operation must be conducted in accordance with the FAA-approved

aircraft flight manual (AFM) or flight manual supplement. Flight crew members
must be thoroughly familiar with the particular GPS equipment installed in the
aircraft, the receiver operation manual, and the AFM or flight manual supple-
ment. Operation, receiver presentation and capabilities of GPS equipment
vary. Due to these differences, operation of GPS receivers of different brands,
or even models of the same brand, under IFR should not be attempted with-
out thorough operational knowledge. Most receivers have a built-in simulator
mode, which allows the pilot to become familiar with operation prior to
attempting operation in the aircraft.

(5) Aircraft navigating by IFR-approved GPS are considered to be performance-

based navigation (PBN) aircraft and have special equipment suffixes. File the
appropriate equipment suffix in accordance with TBL 5-1-3 on the ATC flight
plan. If GPS avionics become inoperative, the pilot should advise ATC and
amend the equipment suffix.

(6) Prior to any GPS IFR operation, the pilot must review appropriate NOTAMs

and aeronautical information. (See GPS NOTAMs/Aeronautical Information).

(b)

Database Requirements. The onboard navigation data must be current and
appropriate for the region of intended operation and should include the navigation
aids, waypoints, and relevant coded terminal airspace procedures for the depar-
ture, arrival, and alternate airfields.

(1) Further database guidance for terminal and en route requirements may be

found in AC 90-100, U.S. Terminal and En Route Area Navigation (RNAV)
Operations.

(2) Further database guidance on Required Navigation Performance (RNP)

instrument approach operations, RNP terminal, and RNP en route require-
ments may be found in AC 90-105, Approval Guidance for RNP Operations
and Barometric Vertical Navigation in the U.S. National Airspace System.

(3) All approach procedures to be flown must be retrievable from the current air-

borne navigation database supplied by the equipment manufacturer or other
FAA-approved source. The system must be able to retrieve the procedure by
name from the aircraft navigation database, not just as a manually entered
series of waypoints. Manual entry of waypoints using latitude/longitude or
place/bearing is not permitted for approach procedures.

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(4) Prior to using a procedure or waypoint retrieved from the airborne navigation

database, the pilot should verify the validity of the database. This verification
should include the following preflight and inflight steps:

[a]

Preflight:

[1] Determine the date of database issuance, and verify that the date/

time of proposed use is before the expiration date/time.

[2] Verify that the database provider has not published a notice limiting

the use of the specific waypoint or procedure.

[b]

Inflight:

[1] Determine that the waypoints and transition names coincide with

names found on the procedure chart. Do not use waypoints which
do not exactly match the spelling shown on published procedure
charts.

[2] Determine that the waypoints are logical in location, in the correct

order, and their orientation to each other is as found on the proce-
dure chart, both laterally and vertically.
NOTE: There is no specific requirement to check each waypoint lat-
itude and longitude, type of waypoint and/or altitude constraint, only
the general relationship of waypoints in the procedure, or the logic
of an individual waypoint’s location.

[3] If the cursory check of procedure logic or individual waypoint loca-

tion, specified in [b] above, indicates a potential error, do not use
the retrieved procedure or waypoint until a verification of latitude
and longitude, waypoint type, and altitude constraints indicate full
conformity with the published data.

(5) Air carrier and commercial operators must meet the appropriate provisions of

their approved operations specifications.

[a] During domestic operations for commerce or for hire, operators must

have a second navigation system capable of reversion or contingency
operations.

[b] Operators must have two independent navigation systems appropriate to

the route to be flown, or one system that is suitable and a second, inde-
pendent backup capability that allows the operator to proceed safely and
land at a different airport, and the aircraft must have sufficient fuel (refer-
ence 14 CFR 121.349, 125.203, 129.17, and 135.165). These rules
ensure the safety of the operation by preventing a single point of failure.
NOTE: An aircraft approved for multi-sensor navigation and equipped
with a single navigation system must maintain an ability to navigate or
proceed safely in the event that any one component of the navigation

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system fails, including the flight management system (FMS). Retaining a
FMS-independent VOR capability would satisfy this requirement.

[c] The requirements for a second system apply to the entire set of equip-

ment needed to achieve the navigation capability, not just the individual
components of the system such as the radio navigation receiver. For
example, to use two RNAV systems (e.g., GPS and DME/DME/IRU) to
comply with the requirements, the aircraft must be equipped with two
independent radio navigation receivers and two independent navigation
computers (e.g., flight management systems (FMS)). Alternatively, to
comply with the requirements using a single RNAV system with an instal-
led and operable VOR capability, the VOR capability must be independ-
ent of the FMS.

[d] To satisfy the requirement for two independent navigation systems, if the

primary navigation system is GPS-based, the second system must be
independent of GPS (for example, VOR or DME/DME/IRU). This allows
continued navigation in case of failure of the GPS or WAAS services.
Recognizing that GPS interference and test events resulting in the loss
of GPS services have become more common, the FAA requires opera-
tors conducting IFR operations under 14 CFR 121.349, 125.203, 129.17
and 135.65 to retain a non-GPS navigation capability consisting of either
DME/DME, IRU, or VOR for en route and terminal operations, and VOR
and ILS for final approach. Since this system is to be used as a rever-
sionary capability, single equipage is sufficient.

Oceanic, Domestic, En Route, and Terminal Area Operations

(a) Conduct GPS IFR operations in oceanic areas only when approved avionics sys-

tems are installed. TSO-C196() users and TSO-C129() GPS users authorized for
Class A1, A2, B1, B2, C1, or C2 operations may use GPS in place of another
approved means of long-range navigation, such as dual INS. (See TBL 1-1-5 and
TBL 1-1-6.) Aircraft with a single installation GPS, meeting the above specifica-
tions, are authorized to operate on short oceanic routes requiring one means of
long-range navigation (reference AC 20-138, Appendix 1).

(b) Conduct GPS domestic, en route, and terminal IFR operations only when

approved avionics systems are installed. Pilots may use GPS via TSO-C129()
authorized for Class A1, B1, B3, C1, or C3 operations GPS via TSO-C196(); or
GPS/WAAS with either TSO-C145() or TSO-C146(). When using TSO-C129() or
TSO-C196() receivers, the avionics necessary to receive all of the ground-based
facilities appropriate for the route to the destination airport and any required alter-
nate airport must be installed and operational. Ground-based facilities necessary
for these routes must be operational.

(1) GPS en route IFR operations may be conducted in Alaska outside the opera-

tional service volume of ground-based navigation aids when a TSO-C145() or
TSO-C146() GPS/wide area augmentation system (WAAS) system is installed

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and operating. WAAS is the U.S. version of a satellite-based augmentation
system (SBAS).

[a] In Alaska, aircraft may operate on GNSS Q-routes with GPS (TSO-C129

() or TSO-C196 ()) equipment while the aircraft remains in Air Traffic
Control (ATC) radar surveillance or with GPS/WAAS (TSO-C145 () or
TSO-C146 ()) which does not require ATC radar surveillance.

[b] In Alaska, aircraft may only operate on GNSS T-routes with GPS/WAAS

(TSO-C145 () or TSO-C146 ()) equipment.

(2) Ground-based navigation equipment is not required to be installed and oper-

ating for en route IFR operations when using GPS/WAAS navigation systems.
All operators should ensure that an alternate means of navigation is available
in the unlikely event the GPS/WAAS navigation system becomes inoperative.

(3) Q-routes and T-routes outside Alaska. Q-routes require system performance

currently met by GPS, GPS/WAAS, or DME/DME/IRU RNAV systems that
satisfy the criteria discussed in AC 90-100, U.S. Terminal and En Route Area
Navigation (RNAV) Operations. T-routes require GPS or GPS/WAAS equip-
ment.

REFERENCE—AIM, Paragraph 5-3-4, Airways and Route Systems.

ics systems are installed and the following requirements are met:

(1) The aircraft is TSO-C145() or TSO-C146() or TSO-C196() or TSO-C129() in

Class A1, B1, B3, C1, or C3; and

(2) The approach/departure must be retrievable from the current airborne naviga-

tion database in the navigation computer. The system must be able to retrieve
the procedure by name from the aircraft navigation database. Manual entry of
waypoints using latitude/longitude or place/bearing is not permitted for
approach procedures.

(3) The authorization to fly instrument approaches/departures with GPS is limited

to U.S. airspace.

(4) The use of GPS in any other airspace must be expressly authorized by the

FAA Administrator.

(5) GPS instrument approach/departure operations outside the U.S. must be

authorized by the appropriate sovereign authority.

Departures and Instrument Departure Procedures (DPs)
The GPS receiver must be set to terminal (±1 NM) CDI sensitivity and the navigation
routes contained in the database in order to fly published IFR charted departures and
DPs. Terminal RAIM should be automatically provided by the receiver. (Terminal RAIM
for departure may not be available unless the waypoints are part of the active flight plan
rather than proceeding direct to the first destination.) Certain segments of a DP may

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require some manual intervention by the pilot, especially when radar vectored to a
course or required to intercept a specific course to a waypoint. The database may not
contain all of the transitions or departures from all runways and some GPS receivers do
not contain DPs in the database. It is necessary that helicopter procedures be flown at
70 knots or less since helicopter departure procedures and missed approaches use a
20:1 obstacle clearance surface (OCS), which is double the fixed-wing OCS, and turn-
ing areas are based on this speed as well.

GPS Instrument Approach Procedures

(a) GPS overlay approaches are designated non-precision instrument approach pro-

cedures that pilots are authorized to fly using GPS avionics. Localizer (LOC),
localizer type directional aid (LDA), and simplified directional facility (SDF) proce-
dures are not authorized. Overlay procedures are identified by the “name of the
procedure” and “or GPS” (e.g., VOR/DME or GPS RWY 15) in the title. Authorized
procedures must be retrievable from a current onboard navigation database. The
navigation database may also enhance position orientation by displaying a map
containing information on conventional NAVAID approaches. This approach infor-
mation should not be confused with a GPS overlay approach (see the receiver
operating manual, AFM, or AFM Supplement for details on how to identify these
approaches in the navigation database).
NOTE: Overlay approaches do not adhere to the design criteria described in
Paragraph 5-4-5m, Area Navigation (RNAV) Instrument Approach Charts, for
stand-alone GPS approaches. Overlay approach criteria is based on the design
criteria used for ground-based NAVAID approaches.

(b) Stand-alone approach procedures specifically designed for GPS systems have

replaced many of the original overlay approaches. All approaches that contain
“GPS” in the title (e.g., “VOR or GPS RWY 24,” “GPS RWY 24,” or “RNAV (GPS)
RWY 24”) can be flown using GPS. GPS-equipped aircraft do not need underlying
ground-based NAVAIDs or associated aircraft avionics to fly the approach. Moni-
toring the underlying approach with ground-based NAVAIDs is suggested when
able. Existing overlay approaches may be requested using the GPS title; for
example, the VOR or GPS RWY 24 may be requested as “GPS RWY 24.” Some
GPS procedures have a Terminal Arrival Area (TAA) with an underlining RNAV
approach.

users) whose navigation systems have fault detection and exclusion (FDE) capa-
bility, who perform a preflight RAIM prediction for the approach integrity at the air-
port where the RNAV (GPS) approach will be flown, and have proper knowledge
and any required training and/or approval to conduct a GPS-based IAP, may file
based on a GPS-based IAP at either the destination or the alternate airport, but
not at both locations. At the alternate airport, pilots may plan for:

(1) Lateral navigation (LNAV) or circling minimum descent altitude (MDA);

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SECTION 1. NAVIGATION AIDS

(2) LNAV/vertical navigation (LNAV/VNAV) DA, if equipped with and using

approved barometric vertical navigation (baro-VNAV) equipment;

(3) RNP 0.3 DA on an RNAV (RNP) IAP, if they are specifically authorized users

using approved baro-VNAV equipment and the pilot has verified required
navigation performance (RNP) availability through an approved prediction
program.

(d) If the above conditions cannot be met, any required alternate airport must have an

approved instrument approach procedure other than GPS-based that is anticipa-
ted to be operational and available at the estimated time of arrival, and which the
aircraft is equipped to fly.

(e)

Procedures for Accomplishing GPS Approaches

(1) An RNAV (GPS) procedure may be associated with a Terminal Arrival Area

(TAA). The basic design of the RNAV procedure is the “T” design or a modi-
fication of the “T” (See Paragraph 5-4-5d, Terminal Arrival Area (TAA), for
complete information).

(2) Pilots cleared by ATC for an RNAV (GPS) approach should fly the full

approach from an Initial Approach Waypoint (IAWP) or feeder fix. Randomly
joining an approach at an intermediate fix does not assure terrain clearance.

(3) When an approach has been loaded in the navigation system, GPS receiv-

ers will give an “arm” annunciation 30 NM straight line distance from the air-
port/heliport reference point. Pilots should arm the approach mode at this
time if not already armed (some receivers arm automatically). Without
arming, the receiver will not change from en route CDI and RAIM sensitivity
of ±5 NM either side of centerline to ±1 NM terminal sensitivity. Where the
IAWP is inside this 30 mile point, a CDI sensitivity change will occur once
the approach mode is armed and the aircraft is inside 30 NM. Where the
IAWP is beyond 30 NM from the airport/heliport reference point and the
approach is armed, the CDI sensitivity will not change until the aircraft is
within 30 miles of the airport/heliport reference point. Feeder route obstacle
clearance is predicated on the receiver being in terminal (±1 NM) CDI sensi-
tivity and RAIM within 30 NM of the airport/heliport reference point; there-
fore, the receiver should always be armed (if required) not later than the 30
NM annunciation.

(4) The pilot must be aware of what bank angle/turn rate the particular receiver

uses to compute turn anticipation, and whether wind and airspeed are inclu-
ded in the receiver’s calculations. This information should be in the receiver
operating manual. Over or under banking the turn onto the final approach
course may significantly delay getting on course and may result in high
descent rates to achieve the next segment altitude.

(5) When within 2 NM of the Final Approach Waypoint (FAWP) with the

approach mode armed, the approach mode will switch to active, which

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results in RAIM and CDI changing to approach sensitivity. Beginning 2 NM
prior to the FAWP, the full scale CDI sensitivity will smoothly change from ±1
NM to ±0.3 NM at the FAWP. As sensitivity changes from ±1 NM to ±0.3 NM
approaching the FAWP, with the CDI not centered, the corresponding
increase in CDI displacement may give the impression that the aircraft is
moving further away from the intended course even though it is on an
acceptable intercept heading. Referencing the digital track displacement
information (cross track error), if it is available in the approach mode, may
help the pilot remain position oriented in this situation. Being established on
the final approach course prior to the beginning of the sensitivity change at 2
NM will help prevent problems in interpreting the CDI display during ramp
down. Therefore, requesting or accepting vectors which will cause the air-
craft to intercept the final approach course within 2 NM of the FAWP is not
recommended.

(6) When receiving vectors to final, most receiver operating manuals suggest

placing the receiver in the non-sequencing mode on the FAWP and man-
ually setting the course. This provides an extended final approach course in
cases where the aircraft is vectored onto the final approach course outside
of any existing segment which is aligned with the runway. Assigned altitudes
must be maintained until established on a published segment of the
approach. Required altitudes at waypoints outside the FAWP or stepdown
fixes must be considered. Calculating the distance to the FAWP may be
required in order to descend at the proper location.

(7) Overriding an automatically selected sensitivity during an approach will

cancel the approach mode annunciation. If the approach mode is not armed
by 2 NM prior to the FAWP, the approach mode will not become active at 2
NM prior to the FAWP, and the equipment will flag. In these conditions, the
RAIM and CDI sensitivity will not ramp down, and the pilot should not
descend to MDA, but fly to the MAWP and execute a missed approach. The
approach active annunciator and/or the receiver should be checked to
ensure the approach mode is active prior to the FAWP.

(8) Do not attempt to fly an approach unless the procedure in the onboard data-

base is current and identified as “GPS” on the approach chart. The naviga-
tion database may contain information about non-overlay approach proce-
dures that enhances position orientation generally by providing a map, while
flying these approaches using conventional NAVAIDs. This approach infor-
mation should not be confused with a GPS overlay approach (see the
receiver operating manual, AFM, or AFM Supplement for details on how to
identify these procedures in the navigation database). Flying point to point
on the approach does not assure compliance with the published approach
procedure. The proper RAIM sensitivity will not be available and the CDI
sensitivity will not automatically change to ±0.3 NM. Manually setting CDI
sensitivity does not automatically change the RAIM sensitivity on some

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receivers. Some existing non-precision approach procedures cannot be
coded for use with GPS and will not be available as overlays.

(9) Pilots should pay particular attention to the exact operation of their GPS

receivers for performing holding patterns and in the case of overlay
approaches, operations such as procedure turns. These procedures may
require manual intervention by the pilot to stop the sequencing of waypoints
by the receiver and to resume automatic GPS navigation sequencing once
the maneuver is complete. The same waypoint may appear in the route of
flight more than once consecutively (for example, IAWP, FAWP, MAHWP on
a procedure turn). Care must be exercised to ensure that the receiver is
sequenced to the appropriate waypoint for the segment of the procedure
being flown, especially if one or more fly-overs are skipped (for example,
FAWP rather than IAWP if the procedure turn is not flown). The pilot may
have to sequence past one or more fly-overs of the same waypoint in order
to start GPS automatic sequencing at the proper place in the sequence of
waypoints.

(10) Incorrect inputs into the GPS receiver are especially critical during

approaches. In some cases, an incorrect entry can cause the receiver to
leave the approach mode.

(11) A fix on an overlay approach identified by a DME fix will not be in the way-

point sequence on the GPS receiver unless there is a published name
assigned to it. When a name is assigned, the along track distance (ATD) to
the waypoint may be zero rather than the DME stated on the approach
chart. The pilot should be alert for this on any overlay procedure where the
original approach used DME.

(12) If a visual descent point (VDP) is published, it will not be included in the

sequence of waypoints. Pilots are expected to use normal piloting techni-
ques for beginning the visual descent, such as ATD.

(13) Unnamed stepdown fixes in the final approach segment may or may not be

coded in the waypoint sequence of the aircraft’s navigation database and
must be identified using ATD. Stepdown fixes in the final approach segment
of RNAV (GPS) approaches are being named, in addition to being identified
by ATD. However, GPS avionics may or may not accommodate waypoints
between the FAF and MAP. Pilots must know the capabilities of their GPS
equipment and continue to identify stepdown fixes using ATD when neces-
sary.

(f)

Missed Approach

(1) A GPS missed approach requires pilot action to sequence the receiver past

the MAWP to the missed approach portion of the procedure. The pilot must
be thoroughly familiar with the activation procedure for the particular GPS
receiver installed in the aircraft and must initiate appropriate action after the

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SECTION 1. NAVIGATION AIDS

MAWP. Activating the missed approach prior to the MAWP will cause CDI
sensitivity to immediately change to terminal (±1NM) sensitivity and the
receiver will continue to navigate to the MAWP. The receiver will not
sequence past the MAWP. Turns should not begin prior to the MAWP. If the
missed approach is not activated, the GPS receiver will display an extension
of the inbound final approach course and the ATD will increase from the
MAWP until it is manually sequenced after crossing the MAWP.

(2) Missed approach routings in which the first track is via a course rather than

direct to the next waypoint require additional action by the pilot to set the
course. Being familiar with all of the inputs required is especially critical
during this phase of flight.

(g)

GPS NOTAMs/Aeronautical Information

(1) GPS satellite outages are issued as GPS NOTAMs both domestically and

internationally. However, the effect of an outage on the intended operation
cannot be determined unless the pilot has a RAIM availability prediction pro-
gram which allows excluding a satellite which is predicted to be out of service
based on the NOTAM information.

(2) The terms UNRELIABLE and MAY NOT BE AVAILABLE are used in con-

junction with GPS NOTAMs. Both UNRELIABLE and MAY NOT BE AVAILA-
BLE are advisories to pilots indicating the expected level of service may not
be available. UNRELIABLE does not mean there is a problem with GPS
signal integrity. If GPS service is available, pilots may continue operations. If
the LNAV or LNAV/VNAV service is available, pilots may use the displayed
level of service to fly the approach. GPS operation may be NOTAMed
UNRELIABLE or MAY NOT BE AVAILABLE due to testing or anomalies.
(Pilots are encouraged to report GPS anomalies, including degraded opera-
tion and/or loss of service, as soon as possible, reference paragraph 1-1-13.)
When GPS testing NOTAMS are published and testing is actually occurring,
Air Traffic Control will advise pilots requesting or cleared for a GPS or RNAV
(GPS) approach that GPS may not be available and request intentions. If
pilots have reported GPS anomalies, Air Traffic Control will request the pilot’s
intentions and/or clear the pilot for an alternate approach, if available and
operational.
EXAMPLE: The following is an example of a GPS testing NOTAM: !GPS
06/001 ZAB NAV GPS (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT
BE AVAILABLE WITHIN A 468NM RADIUS CENTERED AT
330702N1062540W (TCS 093044) FL400-UNL DECREASING IN AREA
WITH A DECREASE IN ALTITUDE DEFINED AS: 425NM RADIUS AT
FL250, 360NM RADIUS AT 10000FT, 354NM RADIUS AT 4000FT AGL,
327NM RADIUS AT 50FT AGL. 1406070300-1406071200.

(3) Civilian pilots may obtain GPS RAIM availability information for non-precision

approach procedures by using a manufacturer-supplied RAIM prediction tool,

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SECTION 1. NAVIGATION AIDS

or using the Service Availability Prediction Tool (SAPT) on the FAA en route
and terminal RAIM prediction website. Pilots can also request GPS RAIM
aeronautical information from a flight service station during preflight briefings.
GPS RAIM aeronautical information can be obtained for a period of 3 hours
(for example, if you are scheduled to arrive at 1215 hours, then the GPS
RAIM information is available from 1100 to 1400 hours) or a 24-hour time-
frame at a particular airport. FAA briefers will provide RAIM information for a
period of 1 hour before to 1 hour after the ETA hour, unless a specific time-
frame is requested by the pilot. If flying a published GPS departure, a RAIM
prediction should also be requested for the departure airport.

(4) The military provides airfield specific GPS RAIM NOTAMs for non-precision

approach procedures at military airfields. The RAIM outages are issued as
M-series NOTAMs and may be obtained for up to 24 hours from the time of
request.

(5) Receiver manufacturers and/or database suppliers may supply “NOTAM”

type information concerning database errors. Pilots should check these sour-
ces, when available, to ensure that they have the most current information
concerning their electronic database.

(h)

Receiver Autonomous Integrity Monitoring (RAIM)

(1) RAIM outages may occur due to an insufficient number of satellites or due to

unsuitable satellite geometry which causes the error in the position solution
to become too large. Loss of satellite reception and RAIM warnings may
occur due to aircraft dynamics (changes in pitch or bank angle). Antenna
location on the aircraft, satellite position relative to the horizon, and aircraft
attitude may affect reception of one or more satellites. Since the relative posi-
tions of the satellites are constantly changing, prior experience with the air-
port does not guarantee reception at all times, and RAIM availability should
always be checked.

(2) If RAIM is not available, use another type of navigation and approach

system, select another route or destination, or delay the trip until RAIM is
predicted to be available on arrival. On longer flights, pilots should consider
rechecking the RAIM prediction for the destination during the flight. This may
provide an early indication that an unscheduled satellite outage has occurred
since takeoff.

(3) If a RAIM failure/status annunciation occurs prior to the final approach way-

point (FAWP), the approach should not be completed since GPS no longer
provides the required integrity. The receiver performs a RAIM prediction by 2
NM prior to the FAWP to ensure that RAIM is available as a condition for
entering the approach mode. The pilot should ensure the receiver has
sequenced from “Armed” to “Approach” prior to the FAWP (normally occurs 2
NM prior). Failure to sequence may be an indication of the detection of a sat-

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ellite anomaly, failure to arm the receiver (if required), or other problems
which preclude flying the approach.

(4) If the receiver does not sequence into the approach mode or a RAIM failure/

status annunciation occurs prior to the FAWP, the pilot must not initiate the
approach or descend, but instead proceed to the missed approach waypoint
(MAWP) via the FAWP, perform a missed approach, and contact ATC as
soon as practical. The GPS receiver may continue to operate after a RAIM
flag/status annunciation appears, but the navigation information should be
considered advisory only. Refer to the receiver operating manual for specific
indications and instructions associated with loss of RAIM prior to the FAF.

(5) If the RAIM flag/status annunciation appears after the FAWP, the pilot should

initiate a climb and execute the missed approach. The GPS receiver may
continue to operate after a RAIM flag/status annunciation appears, but the
navigation information should be considered advisory only. Refer to the
receiver operating manual for operating mode information during a RAIM
annunciation.

(i)

Waypoints

(1) GPS receivers navigate from one defined point to another retrieved from the

aircraft’s onboard navigational database. These points are waypoints (5-letter
pronounceable name), existing VHF intersections, DME fixes with 5-letter
pronounceable names and 3-letter NAVAID IDs. Each waypoint is a geo-
graphical location defined by a latitude/longitude geographic coordinate.
These 5-letter waypoints, VHF intersections, 5-letter pronounceable DME
fixes and 3-letter NAVAID IDs are published on various FAA aeronautical
navigation products (IFR Enroute Charts, VFR Charts, Terminal Procedures
Publications, etc.).

(2) A Computer Navigation Fix (CNF) is also a point defined by a latitude/longi-

tude coordinate and is required to support Performance-Based Navigation
(PBN) operations. The GPS receiver uses CNFs in conjunction with way-
points to navigate from point to point. However, CNFs are not recognized by
ATC. ATC does not maintain CNFs in their database and they do not use
CNFs for any air traffic control purpose. CNFs may or may not be charted on
FAA aeronautical navigation products, are listed in the chart legends, and are
for advisory purposes only. Pilots are not to use CNFs for point to point navi-
gation (proceed direct), filing a flight plan, or in aircraft/ATC communications.
CNFs that do appear on aeronautical charts allow pilots increased situational
awareness by identifying points in the aircraft database route of flight with
points on the aeronautical chart. CNFs are random five-letter identifiers, not
pronounceable like waypoints and placed in parenthesis. Eventually, all
CNFs will begin with the letters “CF” followed by three consonants (for exam-
ple, CFWBG). This five-letter identifier will be found next to an “x” on enroute
charts and possibly on an approach chart. On instrument approach proce-

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SECTION 1. NAVIGATION AIDS

dures (charts) in the terminal procedures publication, CNFs may represent
unnamed DME fixes, beginning and ending points of DME arcs, and sensor
(ground-based signal i.e., VOR, NDB, ILS) final approach fixes on GPS over-
lay approaches. These CNFs provide the GPS with points on the procedure
that allow the overlay approach to mirror the ground-based sensor approach.
These points should only be used by the GPS system for navigation and
should not be used by pilots for any other purpose on the approach. The
CNF concept has not been adopted or recognized by the International Civil
Aviation Organization (ICAO).

(3) GPS approaches use fly-over and fly-by waypoints to join route segments on

an approach. Fly-by waypoints connect the two segments by allowing the air-
craft to turn prior to the current waypoint in order to roll out on course to the
next waypoint. This is known as turn anticipation and is compensated for in
the airspace and terrain clearances. The MAWP and the missed approach
holding waypoint (MAHWP) are normally the only two waypoints on the
approach that are not fly-by waypoints. Fly-over waypoints are used when
the aircraft must overfly the waypoint prior to starting a turn to the new
course. The symbol for a fly-over waypoint is a circled waypoint. Some way-
points may have dual use; for example, as a fly-by waypoint when used as
an IF for a NoPT route and as a fly-over waypoint when the same waypoint is
also used as an IAF/IF hold-in-lieu of PT. When this occurs, the less restric-
tive (fly-by) symbology will be charted. Overlay approach charts and some
early stand-alone GPS approach charts may not reflect this convention.

(4) Unnamed waypoints for each airport will be uniquely identified in the data-

base. Although the identifier may be used at different airports (for example,
RW36 will be the identifier at each airport with a runway 36), the actual point,
at each airport, is defined by a specific latitude/longitude coordinate.

(5) The runway threshold waypoint, normally the MAWP, may have a five-letter

identifier (for example, SNEEZ) or be coded as RW## (for example, RW36,
RW36L). MAWPs located at the runway threshold are being changed to the
RW## identifier, while MAWPs not located at the threshold will have a five-
letter identifier. This may cause the approach chart to differ from the aircraft
database until all changes are complete. The runway threshold waypoint is
also used as the center of the Minimum Safe Altitude (MSA) on most GPS
approaches.

(j)

Position Orientation
Pilots should pay particular attention to position orientation while using GPS. Dis-
tance and track information are provided to the next active waypoint, not to a fixed
navigation aid. Receivers may sequence when the pilot is not flying along an
active route, such as when being vectored or deviating for weather, due to the
proximity to another waypoint in the route. This can be prevented by placing the
receiver in the non-sequencing mode. When the receiver is in the non-sequencing

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mode, bearing and distance are provided to the selected waypoint and the
receiver will not sequence to the next waypoint in the route until placed back in
the auto sequence mode or the pilot selects a different waypoint. The pilot may
have to compute the ATD to stepdown fixes and other points on overlay
approaches, due to the receiver showing ATD to the next waypoint rather than
DME to the VOR or ILS ground station.

(k)

Impact of Magnetic Variation on PBN Systems

(1) Differences may exist between PBN systems and the charted magnetic cour-

ses on ground-based NAVAID instrument flight procedures (IFP), enroute
charts, approach charts, and Standard Instrument Departure/Standard Ter-
minal Arrival (SID/STAR) charts. These differences are due to the magnetic
variance used to calculate the magnetic course. Every leg of an instrument
procedure is first computed along a desired ground track with reference to
true north. A magnetic variation correction is then applied to the true course
in order to calculate a magnetic course for publication. The type of procedure
will determine what magnetic variation value is added to the true course. A
ground-based NAVAID IFP applies the facility magnetic variation of record to
the true course to get the charted magnetic course. Magnetic courses on
PBN procedures are calculated two different ways. SID/STAR procedures
use the airport magnetic variation of record, while IFR enroute charts use
magnetic reference bearing. PBN systems make a correction to true north by
adding a magnetic variation calculated with an algorithm based on aircraft
position, or by adding the magnetic variation coded in their navigational data-
base. This may result in the PBN system and the procedure designer using a
different magnetic variation, which causes the magnetic course

displayed by

the PBN system and the magnetic course

charted on the IFP plate to be dif-

ferent. It is important to understand, however, that PBN systems, (with the
exception of VOR/DME RNAV equipment) navigate by reference to true
north and display magnetic course only for pilot reference. As such, a

prop-

erly functioning PBN system, containing a current and accurate naviga-
tional database, should fly the correct ground track for any loaded instru-
ment procedure, despite differences in displayed magnetic course that may
be attributed to magnetic variation application. Should significant differences
between the approach chart and the PBN system avionics’ application of the
navigation database arise, the published approach chart, supplemented by
NOTAMs, holds precedence.

(2) The course into a waypoint may not always be 180 degrees different from the

course leaving the previous waypoint, due to the PBN system avionics’ com-
putation of geodesic paths, distance between waypoints, and differences in
magnetic variation application. Variations in distances may also occur since
PBN system distance-to-waypoint values are ATDs computed to the next
waypoint and the DME values published on underlying procedures are slant-

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range distances measured to the station. This difference increases with air-
craft altitude and proximity to the NAVAID.

(l)

GPS Familiarization
Pilots should practice GPS approaches in visual meteorological conditions (VMC)
until thoroughly proficient with all aspects of their equipment (receiver and installa-
tion) prior to attempting flight in instrument meteorological conditions (IMC). Pilots
should be proficient in the following areas:

(1) Using the receiver autonomous integrity monitoring (RAIM) prediction func-

tion;

(2) Inserting a DP into the flight plan, including setting terminal CDI sensitivity, if

required, and the conditions under which terminal RAIM is available for
departure;

(3) Programming the destination airport;
(4) Programming and flying the approaches (especially procedure turns and

arcs);

(5) Changing to another approach after selecting an approach;
(6) Programming and flying “direct” missed approaches;
(7) Programming and flying “routed” missed approaches;
(8) Entering, flying, and exiting holding patterns, particularly on approaches with

a second waypoint in the holding pattern;

(9) Programming and flying a “route” from a holding pattern;

(10) Programming and flying an approach with radar vectors to the intermediate

segment;

(11) Indication of the actions required for RAIM failure both before and after the

FAWP; and

(12) Programming a radial and distance from a VOR (often used in departure

instructions).

TABLE 1-1-5 GPS IFR Equipment Classes/Categories

TSO-C129

Equip-

ment

Class

RAIM

Int. Nav Sys.

to Prov.

RAIM Equiv.

Oceanic

En Route

Terminal

Non-precision

Approach Capa-

ble

Class A - GPS sensor and navigation capability.

yes

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SECTION 1. NAVIGATION AIDS

TABLE 1-1-5 GPS IFR Equipment Classes/Categories (continued)

TSO-C129

Equip-

ment

Class

RAIM

Int. Nav Sys.

to Prov.

RAIM Equiv.

Oceanic

En Route

Terminal

Non-precision

Approach Capa-

ble

Class B - GPS sensor data to an integrated navigation system (i.e. FMS, multi-sensor naviga-
tion system, etc.).

yes

Class C - GPS sensor data to an integrated navigation system (as in Class B) which provides
enhanced guidance to an autopilot, or flight director, to reduce flight tech. errors. Limited to 14
CFR Part 121 or equivalent criteria.

yes

TABLE 1-1-6 GPS Approval Required/Authorized Use

Equipment

Type

Installation

Approval
Required

Operational

Approval
Required

IFR

En Route

IFR

Terminal

IFR

Approach

Oceanic

Remote

In Lieu of

ADF and/or

DME

Hand

held

VFR Pan-

el Mount

IFR En

Route and

Terminal

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SECTION 1. NAVIGATION AIDS

TABLE 1-1-6 GPS Approval Required/Authorized Use (continued)

Equipment

Type

Installation

Approval
Required

Operational

Approval
Required

IFR

En Route

IFR

Terminal

IFR

Approach

Oceanic

Remote

In Lieu of

ADF and/or

DME

IFR Oce-

anic/

Remote

IFR En

Route,

Terminal,

and Ap-

proach

To determine equipment approvals and limitations, refer to the AFM, AFM supplements, or pilot
guides.
Requires verification of data for correctness if database is expired.
Requires current database or verification that the procedure has not been amended since the
expiration of the database.
VFR and hand-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.
Hand-held receivers require no approval. However, any aircraft modification to support the
hand-held receiver; i.e., installation of an external antenna or a permanent mounting bracket,
does require approval.

WIDE AREA AUGMENTATION SYSTEM (WAAS)

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 Recom-

mended Practices (SARPs) for satellite-based augmentation systems (SBAS) such as
WAAS. India and Europe are building similar systems: EGNOS, the European Geosta-
tionary Navigation Overlay System; and India’s GPS and Geo-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-based navigation aids, WAAS will cover a more extensive

service area. Precisely surveyed wide-area reference stations (WRS) are linked to form

1-1-18

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SECTION 1. NAVIGATION AIDS

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-area
master station (WMS) where the correction information is computed. A correction mes-
sage 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 mes-
sage 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-time monitoring, and the accuracy is improved by providing differential cor-
rections 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 commissioning of the WAAS for
public use, the FAA conducted a series of test and validation activities. Future dual fre-
quency operations are planned.

6. GNSS navigation, including GPS and WAAS, is referenced to the WGS-84 coordinate

system. It should only be used where the Aeronautical Information Publications (includ-
ing electronic data and aeronautical charts) conform to WGS-84 or equivalent. Other
countries’ civil aviation authorities may impose additional limitations on the use of their
SBAS systems.

Instrument Approach Capabilities

1. A class of approach procedures which provide vertical guidance, but which do not meet

the ICAO Annex 10 requirements for precision approaches has been developed to sup-
port satellite navigation use for aviation applications worldwide. These procedures are
not precision and are referred to as Approach with Vertical Guidance (APV), are defined
in ICAO Annex 6, and include approaches such as the LNAV/VNAV and localizer per-
formance with vertical guidance (LPV). These approaches provide vertical guidance,
but do not meet the more stringent standards of a precision approach. Properly certified
WAAS receivers will be able to fly to LPV minima and LNAV/VNAV minima, using a
WAAS electronic glide path, which eliminates the errors that can be introduced by using
Barometric altimetry.

2. LPV minima takes advantage of the high accuracy guidance and increased integrity

provided by WAAS. This WAAS generated angular guidance allows the use of the same
TERPS approach criteria used for ILS approaches. LPV minima may have a decision
altitude as low as 200 feet height above touchdown with visibility minimums as low as

mile, when the terrain and airport infrastructure support the lowest minima. LPV

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minima is published on the RNAV (GPS) approach charts (see Paragraph 5-4-5, Instru-
ment Approach Procedure Charts).

3. A different WAAS-based line of minima, called Localizer Performance (LP) is being

added in locations where the terrain or obstructions do not allow publication of vertically
guided LPV minima. LP takes advantage of the angular lateral guidance and smaller
position errors provided by WAAS to provide a lateral only procedure similar to an ILS
Localizer. LP procedures may provide lower minima than a LNAV procedure due to the
narrower obstacle clearance surface.
NOTE: WAAS receivers certified prior to TSO-C145b and TSO-C146b, even if they
have LPV capability, do not contain LP capability unless the receiver has been upgra-
ded. Receivers capable of flying LP procedures must contain a statement in the Aircraft
Flight Manual (AFM), AFM Supplement, or Approved Supplemental Flight Manual stat-
ing that the receiver has LP capability, as well as the capability for the other WAAS and
GPS approach procedure types.

4. WAAS provides a level of service that supports all phases of flight, including RNAV

(GPS) approaches to LNAV, LP, LNAV/VNAV and LPV lines of minima, within system
coverage. Some locations close to the edge of the coverage may have a lower availabil-
ity of vertical guidance.

General Requirements

1. WAAS avionics must be certified in accordance with Technical Standard Order (TSO)

TSO-C145(), Airborne Navigation Sensors Using the (GPS) Augmented by the Wide
Area Augmentation System (WAAS); or TSO-C146(), Stand-Alone Airborne Navigation
Equipment Using the Global Positioning System (GPS) Augmented by the Wide Area
Augmentation System (WAAS), and installed in accordance with AC 20-138, Airworthi-
ness Approval of Positioning and Navigation Systems.

2. GPS/WAAS operation must be conducted in accordance with the FAA-approved aircraft

flight manual (AFM) and flight manual supplements. Flight manual supplements will
state the level of approach procedure that the receiver supports. IFR approved WAAS
receivers support all GPS only operations as long as lateral capability at the appropriate
level is functional. WAAS monitors both GPS and WAAS satellites and provides integ-
rity.

3. GPS/WAAS equipment is inherently capable of supporting oceanic and remote opera-

tions if the operator obtains a fault detection and exclusion (FDE) prediction program.

4. Air carrier and commercial operators must meet the appropriate provisions of their

approved operations specifications.

5. Prior to GPS/WAAS IFR operation, the pilot must review appropriate Notices to Airmen

(NOTAMs) and aeronautical information. This information is available on request from a
Flight Service Station. The FAA will provide NOTAMs to advise pilots of the status of
the WAAS and level of service available.

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SECTION 1. NAVIGATION AIDS

(a) The term MAY NOT BE AVBL is used in conjunction with WAAS NOTAMs and

indicates that due to ionospheric conditions, lateral guidance may still be available
when vertical guidance is unavailable. Under certain conditions, both lateral and
vertical guidance may be unavailable. This NOTAM language is an advisory to
pilots indicating the expected level of WAAS service (LNAV/VNAV, LPV, LP) may
not be available.
EXAMPLE: !FDC FDC NAV WAAS VNAV/LPV/LP MINIMA MAY NOT BE AVBL
1306111330-1306141930EST
or
!FDC FDC NAV WAAS VNAV/LPV MINIMA NOT AVBL, WAAS LP MINIMA MAY
NOT BE AVBL 1306021200-1306031200EST
WAAS MAY NOT BE AVBL NOTAMs are predictive in nature and published for
flight planning purposes. Upon commencing an approach at locations NOTAMed
WAAS MAY NOT BE AVBL, if the WAAS avionics indicate LNAV/VNAV or LPV
service is available, then vertical guidance may be used to complete the approach
using the displayed level of service. Should an outage occur during the approach,
reversion to LNAV minima or an alternate instrument approach procedure may be
required. When GPS testing NOTAMS are published and testing is actually occur-
ring, Air Traffic Control will advise pilots requesting or cleared for a GPS or RNAV
(GPS) approach that GPS may not be available and request intentions. If pilots
have reported GPS anomalies, Air Traffic Control will request the pilot’s intentions
and/or clear the pilot for an alternate approach, if available and operational.

(b) WAAS area-wide NOTAMs are originated when WAAS assets are out of service

and impact the service area. Area-wide WAAS NOT AVAILABLE (AVBL) NOTAMs
indicate loss or malfunction of the WAAS system. In flight, Air Traffic Control will
advise pilots requesting a GPS or RNAV (GPS) approach of WAAS NOT AVBL
NOTAMs if not contained in the ATIS broadcast.
EXAMPLE: For unscheduled loss of signal or service, an example NOTAM is: !
FDC FDC NAV WAAS NOT AVBL 1311160600−1311191200EST.
For scheduled loss of signal or service, an example NOTAM is: !FDC FDC NAV
WAAS NOT AVBL 1312041015-1312082000EST.

service; for example, LNAV/VNAV, LP, or LPV may not be available. Pilots must
request site-specific WAAS NOTAMs during flight planning. In flight, Air Traffic
Control will not advise pilots of WAAS MAY NOT BE AVBL NOTAMs.
NOTE: Though currently unavailable, the FAA is updating its prediction tool soft-
ware to provide this site-service in the future.

(d) Most of North America has redundant coverage by two or more geostationary sat-

ellites. One exception is the northern slope of Alaska. If there is a problem with the

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satellite providing coverage to this area, a NOTAM similar to the following example
will be issued:
EXAMPLE: !FDC 4/3406 (PAZA A0173/14) ZAN NAV WAAS SIGNAL MAY NOT
BE AVBL NORTH OF LINE FROM 7000N150000W TO 6400N16400W. RMK
WAAS USERS SHOULD CONFIRM RAIM AVAILABILITY FOR IFR OPERA-
TIONS IN THIS AREA. T-ROUTES IN THIS SECTOR NOT AVBL. ANY
REQUIRED ALTERNATE AIRPORT IN THIS AREA MUST HAVE AN APPROVED
INSTRUMENT APPROACH PROCEDURE OTHER THAN GPS THAT IS ANTICI-
PATED TO BE OPERATIONAL AND AVAILABLE AT THE ESTIMATED TIME OF
ARRIVAL AND WHICH THE AIRCRAFT IS EQUIPPED TO FLY.
1406030812-1406050812EST.

6. When GPS-testing NOTAMS are published and testing is actually occurring, Air Traffic

Control will advise pilots requesting or cleared for a GPS or RNAV (GPS) approach that
GPS may not be available and request intentions. If pilots have reported GPS anoma-
lies, Air Traffic Control will request the pilot’s intentions and/or clear the pilot for an alter-
nate approach, if available and operational.
EXAMPLE: Here is an example of a GPS testing NOTAM:
!GPS

06/001 ZAB NAV GPS (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE

AVAILABLE WITHIN A 468NM RADIUS CENTERED AT 330702N1062540W (TCS
093044) FL400-UNL DECREASING IN AREA WITH A DECREASE IN ALTITUDE
DEFINED AS: 425NM RADIUS AT FL250, 360NM RADIUS AT 10000FT, 354NM
RADIUS AT 4000FT AGL, 327NM RADIUS AT 50FT AGL. 1406070300-1406071200.

7. When the approach chart is annotated with the symbol, site-specific WAAS MAY

NOT BE AVBL NOTAMs or Air Traffic advisories are not provided for outages in WAAS
LNAV/VNAV and LPV vertical service. Vertical outages may occur daily at these loca-
tions due to being close to the edge of WAAS system coverage. Use LNAV or circling
minima for flight planning at these locations, whether as a destination or alternate. For
flight operations at these locations, when the WAAS avionics indicate that LNAV/VNAV
or LPV service is available, then the vertical guidance may be used to complete the
approach using the displayed level of service. Should an outage occur during the proce-
dure, reversion to LNAV minima may be required.
NOTE: Area-wide WAAS NOT AVBL NOTAMs apply to all airports in the WAAS NOT
AVBL area designated in the NOTAM, including approaches at airports where an
approach chart is annotated with the symbol.

8. GPS/WAAS was developed to be used within GEO coverage over North America with-

out the need for other radio navigation equipment appropriate to the route of flight to be
flown. Outside the WAAS coverage or in the event of a WAAS failure, GPS/WAAS
equipment reverts to GPS-only operation and satisfies the requirements for basic GPS
equipment. (See paragraph 1-1-17 for these requirements).

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9. Unlike TSO-C129 avionics, which were certified as a supplement to other means of

navigation, WAAS avionics are evaluated without reliance on other navigation systems.
As such, installation of WAAS avionics does not require the aircraft to have other equip-
ment appropriate to the route to be flown. (See paragraph 1-1-17d for more information
on equipment requirements.)

(a) Pilots with WAAS receivers may flight plan to use any instrument approach proce-

dure authorized for use with their WAAS avionics as the planned approach at a
required alternate, with the following restrictions. When using WAAS at an alter-
nate airport, flight planning must be based on flying the RNAV (GPS) LNAV or cir-
cling minima line, or minima on a GPS approach procedure, or conventional
approach procedure with “or GPS” in the title. Code of Federal Regulation (CFR)
Part 91 non-precision weather requirements must be used for planning. Upon
arrival at an alternate, when the WAAS navigation system indicates that LNAV/
VNAV or LPV service is available, then vertical guidance may be used to complete
the approach using the displayed level of service. The FAA has begun removing
the

NA (Alternate Minimums Not Authorized) symbol from select RNAV (GPS)

and GPS approach procedures so they may be used by approach approved
WAAS receivers at alternate airports. Some approach procedures will still require
the

NA for other reasons, such as no weather reporting, so it cannot be

removed from all procedures. Since every procedure must be individually evalu-
ated, removal of the

NA from RNAV (GPS) and GPS procedures will take some

time.
NOTE: Properly trained and approved, as required, TSO-C145() and TSO-C146()
equipped users (WAAS users) with and using approved baro-VNAV equipment
may plan for LNAV/VNAV DA at an alternate airport. Specifically authorized WAAS
users with and using approved baro-VNAV equipment may also plan for RNP 0.3
DA at the alternate airport as long as the pilot has verified RNP availability through
an approved prediction program.

Flying Procedures with WAAS

1. WAAS receivers support all basic GPS approach functions and provide additional capa-

bilities. One of the major improvements is the ability to generate glide path guidance,
independent of ground equipment or barometric aiding. This eliminates several prob-
lems such as hot and cold temperature effects, incorrect altimeter setting, or lack of a
local altimeter source. It also allows approach procedures to be built without the cost of
installing ground stations at each airport or runway. Some approach certified receivers
may only generate a glide path with performance similar to Baro-VNAV and are only
approved to fly the LNAV/VNAV line of minima on the RNAV (GPS) approach charts.
Receivers with additional capability (including faster update rates and smaller integrity
limits) are approved to fly the LPV line of minima. The lateral integrity changes dramati-
cally from the 0.3 NM (556 meter) limit for GPS, LNAV, and LNAV/VNAV approach
mode, to 40 meters for LPV. It also provides vertical integrity monitoring, which bounds

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SECTION 1. NAVIGATION AIDS

the vertical error to 50 meters for LNAV/VNAV and LPVs with minima of 250' or above,
and bounds the vertical error to 35 meters for LPVs with minima below 250'.

2. When an approach procedure is selected and active, the receiver will notify the pilot of

the most accurate level of service supported by the combination of the WAAS signal,
the receiver, and the selected approach using the naming conventions on the minima
lines of the selected approach procedure. For example, if an approach is published with
LPV minima and the receiver is only certified for LNAV/VNAV, the equipment would
indicate “LNAV/VNAV available,” even though the WAAS signal would support LPV. If
flying an existing LNAV/VNAV procedure with no LPV minima, the receiver will notify
the pilot “LNAV/VNAV available,” even if the receiver is certified for LPV and the signal
supports LPV. If the signal does not support vertical guidance on procedures with LPV
and/or LNAV/VNAV minima, the receiver annunciation will read “LNAV available.” On
lateral only procedures with LP and LNAV minima the receiver will indicate “LP availa-
ble” or “LNAV available” based on the level of lateral service available. Once the level of
service notification has been given, the receiver will operate in this mode for the dura-
tion of the approach procedure, unless that level of service becomes unavailable. The
receiver cannot change back to a more accurate level of service until the next time an
approach is activated.
NOTE: Receivers do not “fail down” to lower levels of service once the approach has
been activated. If only the vertical off flag appears, the pilot may elect to use the LNAV
minima if the rules under which the flight is operating allow changing the type of
approach being flown after commencing the procedure. If the lateral integrity limit is
exceeded on an LP approach, a missed approach will be necessary since there is no
way to reset the lateral alarm limit while the approach is active.

3. Another additional feature of WAAS receivers is the ability to exclude a bad GPS signal

and continue operating normally. This is normally accomplished by the WAAS correc-
tion information. Outside WAAS coverage or when WAAS is not available, it is accom-
plished through a receiver algorithm called FDE. In most cases this operation will be
invisible to the pilot since the receiver will continue to operate with other available satel-
lites after excluding the “bad” signal. This capability increases the reliability of naviga-
tion.

4. Both lateral and vertical scaling for the LNAV/VNAV and LPV approach procedures are

different than the linear scaling of basic GPS. When the complete published procedure
is flown, ±1 NM linear scaling is provided until two (2) NM prior to the FAF, where the
sensitivity increases to be similar to the angular scaling of an ILS. There are two differ-
ences in the WAAS scaling and ILS: 1) on long final approach segments, the initial scal-
ing will be ±0.3 NM to achieve equivalent performance to GPS (and better than ILS,
which is less sensitive far from the runway); 2) close to the runway threshold, the scal-
ing changes to linear instead of continuing to become more sensitive. The width of the
final approach course is tailored so that the total width is usually 700 feet at the runway
threshold. Since the origin point of the lateral splay for the angular portion of the final is
not fixed due to antenna placement like localizer, the splay angle can remain fixed,

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SECTION 1. NAVIGATION AIDS

making a consistent width of final for aircraft being vectored onto the final approach
course on different length runways. When the complete published procedure is not
flown, and instead the aircraft needs to capture the extended final approach course sim-
ilar to ILS, the vector to final (VTF) mode is used. Under VTF, the scaling is linear at ±1
NM until the point where the ILS angular splay reaches a width of ±1 NM regardless of
the distance from the FAWP.

5. The WAAS scaling is also different than GPS TSO-C129() in the initial portion of the

missed approach. Two differences occur here. First, the scaling abruptly changes from
the approach scaling to the missed approach scaling, at approximately the departure
end of the runway or when the pilot selects missed approach guidance rather than
ramping as GPS does. Second, when the first leg of the missed approach is a Track to
Fix (TF) leg aligned within 3 degrees of the inbound course, the receiver will change to
0.3 NM linear sensitivity until the turn initiation point for the first waypoint in the missed
approach procedure, at which time it will abruptly change to terminal (±1 NM) sensitiv-
ity. This allows the elimination of close in obstacles in the early part of the missed
approach that may otherwise cause the DA to be raised.

6. There are two ways to select the final approach segment of an instrument approach.

Most 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 proce-

dure (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 cen-
terline, 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 con-
tinue to the MAWP prior to waypoint sequencing taking place.

GROUND BASED AUGMENTATION SYSTEM (GBAS)

LANDING SYSTEM (GLS)

General

1-1-19

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382

SECTION 1. NAVIGATION AIDS

1. The GLS provides precision navigation guidance for exact alignment and descent of air-

craft on approach to a runway. GBAS equipment provides localized differential augmen-
tation to the Global Positioning System (GPS).
NOTE: To remain consistent with international terminology, the FAA will use the term
GBAS in place of the former term Local Area Augmentation System (LAAS).

2. GLS displays three-dimension vertical and horizontal navigation guidance to the pilot

much like ILS. GLS navigation is based on GPS signals augmented by position correc-
tion, integrity parameters, and approach path definition information transmitted over
VHF from the local GBAS ground station. One GBAS station can support multiple GLS
precision approaches to nearby runways within the GBAS’s maximum use distance.

3. GLS provides guidance similar to ILS approaches for the final approach segment,

though the approach service volume has different dimensions (see FIG 1-1-8). The GLS
approach is constructed using the RNP approach (RNP APCH) navigation specification,
and may include vertically-guided turn(s) after the IAF or on the missed approach pro-
cedure. Portions of the approach prior to an IAF and after the final approach segment
may also require Area Navigation (RNAV) typically using the Required Navigation Per-
formance 1 (RNP 1) navigation specification. See paragraph 1-2-1 for more information
on navigation specifications.

4. GLS consists of a GBAS Ground Facility (GGF), at least four ground reference stations,

a corrections processor, a VHF Data Broadcast (VDB) uplink antenna, an aircraft GBAS
receiver, and a charted instrument approach procedure.

b. Procedure

1. Pilots will select the five digit GBAS channel number of the associated GLS 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 GLS 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). Distance to the runway threshold will be displayed to the pilot
once the aircraft is inside the approach service volume.

3. The pilot will fly the GLS approach using many of the same techniques as ILS including

using a heading or lateral steering mode to intercept the GLS final approach course and
then switching to the appropriate approach navigation mode once the aircraft is within
the approach service volume and prior to the glide path intercept point. See also the
Instrument Procedures Handbook for more information on GLS.

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383

SECTION 1. NAVIGATION AIDS

FIGURE 1-1-8

GLS Standard Approach Service Volume

PRECISION APPROACH SYSTEMS OTHER THAN ILS AND

GLS

General
Approval and use of precision approach systems other than ILS and GLS require the issu-
ance of special instrument approach procedures.

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 pro-
cedures. Special instrument approach procedures are not distributed for general public
use. These procedures are issued to an aircraft operator when the conditions for opera-
tions approval are satisfied.

2. General aviation operators requesting approval for special procedures should contact

the local Flight Standards District Office to obtain a letter of authorization. Air carrier

1-1-20

RADIO DATA - GENERAL

384

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JEPPESEN GENERAL AIRWAY MANUAL (Issue Date 1 JUL 21) - page 12