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Navigation Aids
locations close to the edge of the coverage may have
a lower availability of vertical guidance.
c. General Requirements
1.
WAAS avionics must be certified in
accordance with Technical Standard Order (TSO)
TSO−C145a, Airborne Navigation Sensors Using the
(GPS) Augmented by the Wide Area Augmentation
System (WAAS); or TSO−C146a, Stand−Alone
Airborne Navigation Equipment Using the Global
Positioning System (GPS) Augmented by the Wide
Area Augmentation System (WAAS), and installed in
accordance with Advisory Circular (AC) 20−130A,
Airworthiness Approval of Navigation or Flight
Management Systems Integrating Multiple Naviga-
tion Sensors, or AC 20−138A, Airworthiness
Approval of Global Positioning System (GPS)
Navigation Equipment for Use as a VFR and IFR
Navigation System.
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 integrity.
3.
GPS/WAAS equipment is inherently capable
of supporting oceanic and remote operations 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 (NOT-
AMs) 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.
(a)
The term UNRELIABLE is used in
conjunction with GPS and WAAS NOTAMs. The
term UNRELIABLE is an advisory to pilots
indicating the expected level of WAAS service
(LNAV/VNAV, LPV) may not be available;
e.g., !BOS BOS WAAS LPV AND LNAV/VNAV
MNM UNREL WEF 0305231700
− 0305231815.
WAAS UNRELIABLE NOTAMs are predictive in
nature and published for flight planning purposes.
Upon commencing an approach at locations
NOTAMed WAAS UNRELIABLE, 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 may be required.
(1)
Area−wide WAAS UNAVAILABLE
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 UNAVAILABLE NOTAMs if not contained
in the ATIS broadcast.
(2)
Site−specific WAAS UNRELIABLE
NOTAMs indicate an expected level of service,
e.g., LNAV/VNAV 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 UNRELIABLE
NOTAMs.
(3)
When the approach chart is annotated
with the symbol, site−specific WAAS UNRELI-
ABLE 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 locations 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 procedure, reversion to
LNAV minima may be required.
NOTE
−
Area
−wide WAAS UNAVAILABLE NOTAMs apply to all
airports in the WAAS UNAVAILABLE area designated inthe NOTAM, including approaches at airports where an
approach chart is annotated with the
symbol.
6.
GPS/WAAS was developed to be used within
SBAS GEO coverage (WAAS or other interoperable
system) without the need for other radio navigation
equipment appropriate to the route of flight to be
flown. Outside the SBAS coverage or in the event of
a WAAS failure, GPS/WAAS equipment reverts to
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Navigation Aids
GPS−only operation and satisfies the requirements
for basic GPS equipment.
7.
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 equipment appropriate to the
route to be flown.
(a)
Pilots with WAAS receivers may flight
plan to use any instrument approach procedure
authorized for use with their WAAS avionics as
the planned approach at a required alternate, with
the following restrictions. When using WAAS at
an alternate airport, flight planning must be based
on flying the RNAV (GPS) LNAV or circling 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
nonprecision 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 individu-
ally evaluated, 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 andusing approved baro-VNAV equipment may plan forLNAV/VNAV DA at an alternate airport. Specificallyauthorized WAAS users with and using approvedbaro-VNAV equipment may also plan for RNP 0.3 DA at thealternate airport as long as the pilot has verified RNP
availability through an approved prediction program.
d. Flying Procedures with WAAS
1.
WAAS receivers support all basic GPS
approach functions and provide additional capabilit-
ies. One of the major improvements is the ability to
generate glide path guidance, independent of ground
equipment or barometric aiding. This eliminates
several problems 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
dramatically 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 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 combina-
tion 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 annunci-
ation will read “LNAV available.” On lateral only
procedures with LP and LNAV minima the receiver
will indicate “LP available” 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 duration 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
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vertical off flag appears, the pilot may elect to use theLNAV minima if the rules under which the flight isoperating allow changing the type of approach being flownafter commencing the procedure. If the lateral integritylimit is exceeded on an LP approach, a missed approachwill be necessary since there is no way to reset the lateral
alarm limit while the approach is active.
3.
Another additional feature of WAAS receiv-
ers is the ability to exclude a bad GPS signal and
continue operating normally. This is normally
accomplished by the WAAS correction information.
Outside WAAS coverage or when WAAS is not
available, it is accomplished 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 satellites
after excluding the “bad” signal. This capability
increases the reliability of navigation.
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 scaling 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 scaling 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, 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 similar 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
requests 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) sensitivity. This allows
the elimination of close in obstacles in the early part
of the missed approach that may cause the DA to be
raised.
6.
A new method has been added for selecting
the final approach segment of an instrument
approach. Along with the current method used by
most receivers using 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 until the ATD reaches 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
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Navigation Aids
may also select missed approach prior to the MAWP,
however, navigation will continue to the MAWP prior
to waypoint sequencing taking place.
1
−
1
−
20. 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).
NOTE
−
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
(RNP).
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
identified.
1
−
1
−
21. Precision Approach Systems other
than ILS, GLS, and MLS
a. General
Approval and use of precision approach systems
other than ILS, GLS and MLS 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.
2.
General aviation operators requesting ap-
proval for special procedures should contact the local
Flight Standards District Office to obtain a letter of
authorization. Air carrier operators requesting
approval for use of special procedures should contact
their Certificate Holding District Office for authoriz-
ation through their Operations Specification.
c. Transponder Landing System (TLS)
1.
The TLS is designed to provide approach
guidance utilizing existing airborne ILS localizer,
glide slope, and transponder equipment.
2.
Ground equipment consists of a transponder
interrogator, sensor arrays to detect lateral and
vertical position, and ILS frequency transmitters. The
TLS detects the aircraft’s position by interrogating its
transponder. It then broadcasts ILS frequency signals
to guide the aircraft along the desired approach path.
3.
TLS instrument approach procedures are
designated Special Instrument Approach Procedures.
Special aircrew training is required. TLS ground
equipment provides approach guidance for only one
aircraft at a time. Even though the TLS signal is
received using the ILS receiver, no fixed course or
glidepath is generated. The concept of operation is
very similar to an air traffic controller providing radar
vectors, and just as with radar vectors, the guidance
is valid only for the intended aircraft. The TLS
ground equipment tracks one aircraft, based on its
transponder code, and provides correction signals to
course and glidepath based on the position of the
tracked aircraft. Flying the TLS corrections com-
puted for another aircraft will not provide guidance
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Navigation Aids
relative to the approach; therefore, aircrews must not
use the TLS signal for navigation unless they have
received approach clearance and completed the
required coordination with the TLS ground equip-
ment operator. Navigation fixes based on
conventional NAVAIDs or GPS are provided in the
special instrument approach procedure to allow
aircrews to verify the TLS guidance.
d. Special Category I Differential GPS (SCAT
−
I DGPS)
1.
The SCAT−I DGPS is designed to provide
approach guidance by broadcasting differential
correction to GPS.
2.
SCAT−I DGPS procedures require aircraft
equipment and pilot training.
3.
Ground equipment consists of GPS receivers
and a VHF digital radio transmitter. The SCAT−I
DGPS detects the position of GPS satellites relative
to GPS receiver equipment and broadcasts differen-
tial corrections over the VHF digital radio.
4.
Category I Ground Based Augmentation
System (GBAS) will displace SCAT−I DGPS as the
public use service.
REFERENCE
−
AIM, Para 5
−4−7f, Instrument Approach Procedures.
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Area Navigation (RNAV) and Required Navigation Performance (RNP)
Section 2. Area Navigation (RNAV) and Required
Navigation Performance (RNP)
1
−
2
−
1. Area Navigation (RNAV)
a. General.
RNAV is a method of navigation that
permits aircraft operation on any desired flight path
within the coverage of ground or space based
navigation aids or within the limits of the capability
of self−contained aids, or a combination of these. In
the future, there will be an increased dependence on
the use of RNAV in lieu of routes defined by
ground−based navigation aids.
RNAV routes and terminal procedures, including
departure procedures (DPs) and standard terminal
arrivals (STARs), are designed with RNAV systems
in mind. There are several potential advantages of
RNAV routes and procedures:
1.
Time and fuel savings,
2.
Reduced dependence on radar vectoring,
altitude, and speed assignments allowing a reduction
in required ATC radio transmissions, and
3.
More efficient use of airspace.
In addition to information found in this manual,
guidance for domestic RNAV DPs, STARs, and
routes may also be found in Advisory Circu-
lar 90−100A, U.S. Terminal and En Route Area
Navigation (RNAV) Operations.
b. RNAV Operations.
RNAV procedures, such
as DPs and STARs, demand strict pilot awareness and
maintenance of the procedure centerline. Pilots
should possess a working knowledge of their aircraft
navigation system to ensure RNAV procedures are
flown in an appropriate manner. In addition, pilots
should have an understanding of the various
waypoint and leg types used in RNAV procedures;
these are discussed in more detail below.
1. Waypoints.
A waypoint is a predetermined
geographical position that is defined in terms of
latitude/longitude coordinates. Waypoints may be a
simple named point in space or associated with
existing navaids, intersections, or fixes. A waypoint
is most often used to indicate a change in direction,
speed, or altitude along the desired path. RNAV
procedures make use of both fly−over and fly−by
waypoints.
(a) Fly
−by waypoints. Fly−by waypoints
are used when an aircraft should begin a turn to the
next course prior to reaching the waypoint separating
the two route segments. This is known as turn
anticipation.
(b) Fly
−over waypoints. Fly−over way-
points are used when the aircraft must fly over the
point prior to starting a turn.
NOTE
−
FIG 1
−2−1 illustrates several differences between a fly−by
and a fly
−over waypoint.
FIG 1
−2−1
Fly
−by and Fly−over Waypoints
2. RNAV Leg Types.
A leg type describes the
desired path proceeding, following, or between
waypoints on an RNAV procedure. Leg types are
identified by a two−letter code that describes the path
(e.g., heading, course, track, etc.) and the termination
point (e.g., the path terminates at an altitude, distance,
fix, etc.). Leg types used for procedure design are
included in the aircraft navigation database, but not
normally provided on the procedure chart. The
narrative depiction of the RNAV chart describes how
a procedure is flown. The “path and terminator
concept” defines that every leg of a procedure has a
termination point and some kind of path into that
termination point. Some of the available leg types are
described below.
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Area Navigation (RNAV) and Required Navigation Performance (RNP)
(a) Track to Fix.
A Track to Fix (TF) leg is
intercepted and acquired as the flight track to the
following waypoint. Track to a Fix legs are
sometimes called point−to−point legs for this reason.
Narrative: “on track 087 to CHEZZ WP.”
See
FIG 1−2−2.
(b) Direct to Fix.
A Direct to Fix (DF) leg is
a path described by an aircraft’s track from an initial
area direct to the next waypoint. Narrative: “left
turn direct BARGN WP.”
See FIG 1−2−3.
FIG 1
−2−2
Track to Fix Leg Type
FIG 1
−2−3
Direct to Fix Leg Type
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Area Navigation (RNAV) and Required Navigation Performance (RNP)
(c) Course to Fix.
A Course to Fix (CF) leg
is a path that terminates at a fix with a specified course
at that fix. Narrative: “on course 078 to PRIMY
WP.”
See FIG 1−2−4.
FIG 1
−2−4
Course to Fix Leg Type
(d) Radius to Fix.
A Radius to Fix (RF) leg
is defined as a constant radius circular path around a
defined turn center that terminates at a fix. See
FIG 1−2−5.
FIG 1
−2−5
Radius to Fix Leg Type
(e) Heading.
A Heading leg may be defined
as, but not limited to, a Heading to Altitude (VA),
Heading to DME range (VD), and Heading to Manual
Termination, i.e., Vector (VM). Narrative: “climb
heading 350 to 1500”, “heading 265, at 9 DME west
of PXR VORTAC, right turn heading 360”, “fly
heading 090, expect radar vectors to DRYHT INT.”
3. Navigation Issues.
Pilots should be aware
of their navigation system inputs, alerts, and
annunciations in order to make better−informed
decisions. In addition, the availability and suitability
of particular sensors/systems should be considered.
(a) GPS.
Operators using TSO−C129 sys-
tems should ensure departure and arrival airports are
entered to ensure proper RAIM availability and CDI
sensitivity.
(b) DME/DME.
Operators should be aware
that DME/DME position updating is dependent on
FMS logic and DME facility proximity, availability,
geometry, and signal masking.
(c) VOR/DME.
Unique VOR characteris-
tics may result in less accurate values from
VOR/DME position updating than from GPS or
DME/DME position updating.
(d) Inertial Navigation.
Inertial reference
units and inertial navigation systems are often
coupled with other types of navigation inputs,
e.g., DME/DME or GPS, to improve overall
navigation system performance.
NOTE
−
Specific inertial position updating requirements may
apply.
4. Flight Management System (FMS).
An
FMS is an integrated suite of sensors, receivers, and
computers, coupled with a navigation database.
These systems generally provide performance and
RNAV guidance to displays and automatic flight
control systems.
Inputs can be accepted from multiple sources such as
GPS, DME, VOR, LOC and IRU. These inputs may
be applied to a navigation solution one at a time or in
combination. Some FMSs provide for the detection
and isolation of faulty navigation information.
When appropriate navigation signals are available,
FMSs will normally rely on GPS and/or DME/DME
(that is, the use of distance information from two or
more DME stations) for position updates. Other
inputs may also be incorporated based on FMS
system architecture and navigation source geometry.
NOTE
−
DME/DME inputs coupled with one or more IRU(s) are
often abbreviated as DME/DME/IRU or D/D/I.
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Area Navigation (RNAV) and Required Navigation Performance (RNP)
1
−
2
−
2. Required Navigation Performance
(RNP)
a. General.
RNP is RNAV with on−board
navigation monitoring and alerting, RNP is also a
statement of navigation performance necessary for
operation within a defined airspace. A critical
component of RNP is the ability of the aircraftnavigation system to monitor its achieved navigationperformance, and to identify for the pilot whether theoperational requirement is, or is not being met during
an operation
. This on−board performance monitor-
ing and alerting capability therefore allows a lessened
reliance on air traffic control intervention (via radar
monitoring, automatic dependent surveillance
(ADS), multilateration, communications), and/or
route separation to achieve the overall safety of the
operation. RNP capability of the aircraft is a major
component in determining the separation criteria to
ensure that the overall containment of the operation
is met.
The RNP capability of an aircraft will vary depending
upon the aircraft equipment and the navigation
infrastructure. For example, an aircraft may be
equipped and certified for RNP 1.0, but may not be
capable of RNP 1.0 operations due to limited navaid
coverage.
b. RNP Operations.
1. RNP Levels.
An RNP “level” or “type” is
applicable to a selected airspace, route, or procedure.
As defined in the Pilot/Controller Glossary, the RNP
Level or Type is a value typically expressed as a
distance in nautical miles from the intended
centerline of a procedure, route, or path. RNP
applications also account for potential errors at some
multiple of RNP level (e.g., twice the RNP level).
(a) Standard RNP Levels.
U.S. standard
values supporting typical RNP airspace are as
specified in TBL 1−2−1 below. Other RNP levels as
identified by ICAO, other states and the FAA may
also be used.
(b) Application of Standard RNP Levels.
U.S. standard levels of RNP typically used for
various routes and procedures supporting RNAV
operations may be based on use of a specific
navigational system or sensor such as GPS, or on
multi−sensor RNAV systems having suitable perfor-
mance.
(c) Depiction of Standard RNP Levels.
The
applicable RNP level will be depicted on affected
charts and procedures.
TBL 1
−2−1
U.S. Standard RNP Levels
RNP Level
Typical Application
Primary Route Width (NM)
−
Centerline to Boundary
0.1 to 1.0
RNP AR Approach Segments
0.1 to 1.0
0.3 to 1.0
RNP Approach Segments
0.3 to 1.0
1
Terminal and En Route
1.0
2
En Route
2.0
NOTE
−
1. The “performance” of navigation in RNP refers not only to the level of accuracy of a particular sensor or aircraftnavigation system, but also to the degree of precision with which the aircraft will be flown. 2. Specific required flight procedures may vary for different RNP levels.
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Area Navigation (RNAV) and Required Navigation Performance (RNP)
TBL 1
−2−2
RNP Levels Supported for International Operations
RNP Level
Typical Application
4
Projected for oceanic/remote areas where 30 NM horizontal separation is applied
10
Oceanic/remote areas where 50 NM lateral separation is applied
c. Other RNP Applications Outside the U.S.
The FAA and ICAO member states have led
initiatives in implementing the RNP concept to
oceanic operations. For example, RNP−10 routes
have been established in the northern Pacific
(NOPAC) which has increased capacity and
efficiency by reducing the distance between tracks
to 50 NM. (See TBL 1−2−2.)
d. Aircraft and Airborne Equipment Eligibility
for RNP Operations.
Aircraft meeting RNP criteria
will have an appropriate entry including special
conditions and limitations in its Aircraft Flight
Manual (AFM), or supplement. Operators of aircraft
not having specific AFM−RNP certification may be
issued operational approval including special condi-
tions and limitations for specific RNP levels.
NOTE
−
Some airborne systems use Estimated Position Uncer-tainty (EPU) as a measure of the current estimatednavigational performance. EPU may also be referred to asActual Navigation Performance (ANP) or Estimated
Position Error (EPE).
1
−
2
−
3. Use of Suitable Area Navigation
(RNAV) Systems on Conventional
Procedures and Routes
a. Discussion.
This paragraph sets forth policy,
while providing operational and airworthiness
guidance regarding the suitability and use of RNAV
systems when operating on, or transitioning to,
conventional, non−RNAV routes and procedures
within the U.S. National Airspace System (NAS):
1.
Use of a suitable RNAV system as a
Substitute Means of Navigation when a Very−High
Frequency (VHF) Omni−directional Range (VOR),
Distance Measuring Equipment (DME), Tactical Air
Navigation (TACAN), VOR/TACAN (VORTAC),
VOR/DME, Non−directional Beacon (NDB), or
compass locator facility including locator outer
marker and locator middle marker is out−of−service
(that is, the navigation aid (NAVAID) information is
not available); an aircraft is not equipped with an
Automatic Direction Finder (ADF) or DME; or the
installed ADF or DME on an aircraft is not
operational. For example, if equipped with a suitable
RNAV system, a pilot may hold over an out−of−
service NDB.
2.
Use of a suitable RNAV system as an
Alternate Means of Navigation when a VOR, DME,
VORTAC, VOR/DME, TACAN, NDB, or compass
locator facility including locator outer marker and
locator middle marker is operational and the
respective aircraft is equipped with operational
navigation equipment that is compatible with
conventional navaids. For example, if equipped with
a suitable RNAV system, a pilot may fly a procedure
or route based on operational VOR using that RNAV
system without monitoring the VOR.
NOTE
−
1. Additional information and associated requirementsare available in Advisory Circular 90-108 titled “Use ofSuitable RNAV Systems on Conventional Routes and
Procedures.”
2. Good planning and knowledge of your RNAV system are
critical for safe and successful operations.
3. Pilots planning to use their RNAV system as a substitute
means of navigation guidance in lieu of an out
−of−service
NAVAID
may need to advise ATC of this intent and
capability.
4. The navigation database should be current for theduration of the flight. If the AIRAC cycle will changeduring flight, operators and pilots should establishprocedures to ensure the accuracy of navigation data,including suitability of navigation facilities used to definethe routes and procedures for flight. To facilitate validatingdatabase currency, the FAA has developed procedures forpublishing the amendment date that instrument approachprocedures were last revised. The amendment date followsthe amendment number, e.g., Amdt 4 14Jan10. Currency ofgraphic departure procedures and STARs may beascertained by the numerical designation in the proceduretitle. If an amended chart is published for the procedure, or
the procedure amendment date shown on the chart is on or
Page 12
AIM
4/3/14
1−2−6
Area Navigation (RNAV) and Required Navigation Performance (RNP)
after the expiration date of the database, the operator must
not use the database to conduct the operation.
b. Types of RNAV Systems that Qualify as a
Suitable RNAV System.
When installed in accord-
ance with appropriate airworthiness installation
requirements and operated in accordance with
applicable operational guidance (e.g., aircraft flight
manual and Advisory Circular material), the
following systems qualify as a suitable RNAV
system:
1.
An RNAV system with TSO−C129/
−C145/−C146 equipment, installed in accordance
with AC 20−138, Airworthiness Approval of Global
Positioning System (GPS) Navigation Equipment for
Use as a VFR and IFR Supplemental Navigation
System, or AC 20−130A, Airworthiness Approval of
Navigation or Flight Management Systems Integrat-
ing Multiple Navigation Sensors, and authorized for
instrument flight rules (IFR) en route and terminal
operations (including those systems previously
qualified for “GPS in lieu of ADF or DME”
operations), or
2.
An RNAV system with DME/DME/IRU
inputs that is compliant with the equipment
provisions of AC 90−100A, U.S. Terminal and
En Route Area Navigation (RNAV) Operations, for
RNAV routes. A table of compliant equipment is
available at the following website:
h t t p : / / w w w . f a a . g o v / a b o u t / o f f i c e _ o r g /headquarters_offices/avs/offices/afs/afs400/afs47
0/policy_guidance/
NOTE
−
Approved RNAV systems using DME/DME/IRU, withoutGPS/WAAS position input, may only be used as a substitutemeans of navigation when specifically authorized by aNotice to Airmen (NOTAM) or other FAA guidance for aspecific procedure. The NOTAM or other FAA guidanceauthorizing the use of DME/DME/IRU systems will alsoidentify any required DME facilities based on an FAA
assessment of the DME navigation infrastructure.
c. Uses of Suitable RNAV Systems.
Subject to
the operating requirements, operators may use a
suitable RNAV system in the following ways.
1.
Determine aircraft position relative to, or
distance from a VOR (see NOTE 5 below), TACAN,
NDB, compass locator, DME fix; or a named fix
defined by a VOR radial, TACAN course, NDB
bearing, or compass locator bearing intersecting a
VOR or localizer course.
2.
Navigate to or from a VOR, TACAN, NDB,
or compass locator.
3.
Hold over a VOR, TACAN, NDB, compass
locator, or DME fix.
4.
Fly an arc based upon DME.
NOTE
−
1. The allowances described in this section apply evenwhen a facility is identified as required on a procedure (for
example, “Note ADF required”).
2. These operations do not include lateral navigation on
localizer
−based courses (including localizer back−course
guidance) without reference to raw localizer data.
3. Unless otherwise specified, a suitable RNAV systemcannot be used for navigation on procedures that areidentified as not authorized (“NA”) without exception bya NOTAM. For example, an operator may not use a RNAVsystem to navigate on a procedure affected by an expired orunsatisfactory flight inspection, or a procedure that is
based upon a recently decommissioned NAVAID.
4. Pilots may not substitute for the NAVAID (for example,a VOR or NDB) providing lateral guidance for the finalapproach segment. This restriction does not refer toinstrument approach procedures with “or GPS” in the titlewhen using GPS or WAAS. These allowances do not applyto procedures that are identified as not authorized (NA)without exception by a NOTAM, as other conditions maystill exist and result in a procedure not being available. Forexample, these allowances do not apply to a procedureassociated with an expired or unsatisfactory flightinspection, or is based upon a recently decommissioned
NAVAID.
5. For the purpose of paragraph c, “VOR” includes VOR,VOR/DME, and VORTAC facilities and “compasslocator” includes locator outer marker and locator middle
marker.
Page 13
AIM
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1−2−7
Area Navigation (RNAV) and Required Navigation Performance (RNP)
d. Alternate Airport Considerations.
For the
purposes of flight planning, any required alternate
airport must have an available instrument approach
procedure that does not require the use of GPS. This
restriction includes conducting a conventional
approach at the alternate airport using a substitute
means of navigation that is based upon the use of
GPS. For example, these restrictions would apply
when planning to use GPS equipment as a substitute
means of navigation for an out−of−service VOR that
supports an ILS missed approach procedure at an
alternate airport. In this case, some other approach
not reliant upon the use of GPS must be available.
This restriction does not apply to RNAV systems
using TSO−C145/−C146 WAAS equipment. For
further WAAS guidance see AIM 1−1−19.
1.
For flight planning purposes, TSO-C129()
and TSO-C196() equipped users (GPS users) whose
navigation systems have fault detection and
exclusion (FDE) capability, who perform a preflight
RAIM prediction at the airport 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 applicable
alternate airport weather minimums using:
(a)
Lateral navigation (LNAV) or circling
minimum descent altitude (MDA);
(b)
LNAV/vertical navigation (LNAV/
VNAV) DA, if equipped with and using approved
barometric vertical navigation (baro-VNAV) equip-
ment;
(c)
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.
2.
If the above conditions cannot be met, any
required alternate airport must have an approved
instrument approach procedure other than GPS that is
anticipated to be operational and available at the
estimated time of arrival, and which the aircraft is
equipped to fly.
3.
This restriction does not apply to
TSO-C145() and TSO-C146() equipped users
(WAAS users). For further WAAS guidance see AIM
1−1−19.
Page 14
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Page 15
AIM
4/3/14
2−1−1
Airport Lighting Aids
Chapter 2. Aeronautical Lighting and
Other Airport Visual Aids
Section 1. Airport Lighting Aids
2
−
1
−
1. Approach Light Systems (ALS)
a.
ALS provide the basic means to transition from
instrument flight to visual flight for landing.
Operational requirements dictate the sophistication
and configuration of the approach light system for a
particular runway.
b.
ALS are a configuration of signal lights starting
at the landing threshold and extending into the
approach area a distance of 2400−3000 feet for
precision instrument runways and 1400−1500 feet for
nonprecision instrument runways. Some systems
include sequenced flashing lights which appear to the
pilot as a ball of light traveling towards the runway at
high speed (twice a second). (See FIG 2−1−1.)
2
−
1
−
2. Visual Glideslope Indicators
a. Visual Approach Slope Indicator (VASI)
1.
VASI installations may consist of either 2, 4,
6, 12, or 16 light units arranged in bars referred to as
near, middle, and far bars. Most VASI installations
consist of 2 bars, near and far, and may consist of 2,
4, or 12 light units. Some VASIs consist of three bars,
near, middle, and far, which provide an additional
visual glide path to accommodate high cockpit
aircraft. This installation may consist of either 6 or
16 light units. VASI installations consisting of 2, 4, or
6 light units are located on one side of the runway,
usually the left. Where the installation consists of
12 or 16 light units, the units are located on both sides
of the runway.
2.
Two−bar VASI installations provide one
visual glide path which is normally set at 3 degrees.
Three−bar VASI installations provide two visual
glide paths. The lower glide path is provided by the
near and middle bars and is normally set at 3 degrees
while the upper glide path, provided by the middle
and far bars, is normally
1
/
4
degree higher. This
higher glide path is intended for use only by high
cockpit aircraft to provide a sufficient threshold
crossing height. Although normal glide path angles
are three degrees, angles at some locations may be as
high as 4.5 degrees to give proper obstacle clearance.
Pilots of high performance aircraft are cautioned that
use of VASI angles in excess of 3.5 degrees may cause
an increase in runway length required for landing and
rollout.
3.
The basic principle of the VASI is that of color
differentiation between red and white. Each light unit
projects a beam of light having a white segment in the
upper part of the beam and red segment in the lower
part of the beam. The light units are arranged so that
the pilot using the VASIs during an approach will see
the combination of lights shown below.
4.
The VASI is a system of lights so arranged to
provide visual descent guidance information during
the approach to a runway. These lights are visible
from 3−5 miles during the day and up to 20 miles or
more at night. The visual glide path of the VASI
provides safe obstruction clearance within plus or
minus 10 degrees of the extended runway centerline
and to 4 NM from the runway threshold. Descent,
using the VASI, should not be initiated until the
aircraft is visually aligned with the runway. Lateral
course guidance is provided by the runway or runway
lights. In certain circumstances, the safe obstruction
clearance area may be reduced due to local
limitations, or the VASI may be offset from the
extended runway centerline. This will be noted in the
Airport/ Facility Directory.
Page 16
AIM
4/3/14
2−1−2
Airport Lighting Aids
FIG 2
−1−1
Precision & Nonprecision Configurations
NOTE
−
Civil ALSF
−2 may be operated as SSALR during favorable weather conditions.
Page 17
AIM
4/3/14
2−1−3
Airport Lighting Aids
5.
For 2−bar VASI (4 light units) see FIG 2−1−2.
FIG 2
−1−2
2
−Bar VASI
Far Bar
= Red
= White
Near Bar
Below Glide Path
On Glide Path
Above Glide Path
6.
For 3−bar VASI (6 light units) see FIG 2−1−3.
FIG 2
−1−3
3
−Bar VASI
Far Bar
Middle Bar
Near Bar
Below Both
Glide Paths
On Lower
Glide Path
On Upper
Glide Path
Above Both
Glide Paths
7.
For other VASI configurations see FIG 2−1−4.
FIG 2
−1−4
VASI Variations
2 Bar
2 Light Units
On Glide Path
2 Bar
12 Light Units
On Glide Path
3 Bar
16 Light Units
on Lower Glide Path
Page 18
AIM
4/3/14
2−1−4
Airport Lighting Aids
b. Precision Approach Path Indicator (PAPI).
The precision approach path indicator (PAPI) uses
light units similar to the VASI but are installed in a
single row of either two or four light units. These
lights are visible from about 5 miles during the day
and up to 20 miles at night. The visual glide path of
the PAPI typically provides safe obstruction
clearance within plus or minus 10 degrees of the
extended runway centerline and to 4 SM from the
runway threshold. Descent, using the PAPI, should
not be initiated until the aircraft is visually aligned
with the runway. The row of light units is normally
installed on the left side of the runway and the glide
path indications are as depicted. Lateral course
guidance is provided by the runway or runway lights.
In certain circumstances, the safe obstruction
clearance area may be reduced due to local
limitations, or the PAPI may be offset from the
extended runway centerline. This will be noted in the
Airport/ Facility Directory. (See FIG 2−1−5.)
FIG 2
−1−5
Precision Approach Path Indicator (PAPI)
Slightly High
(3.2 Degrees)
White
Red
High
(More Than
3,5 Degrees)
On Glide Path
(3 Degrees)
Slightly Low
(2.8 Degrees)
Low
(Less Than
2.5 Degrees)
c. Tri
−color Systems. Tri−color visual approach
slope indicators normally consist of a single light unit
projecting a three−color visual approach path into the
final approach area of the runway upon which the
indicator is installed. The below glide path indication
is red, the above glide path indication is amber, and
the on glide path indication is green. These types of
indicators have a useful range of approximately
one−half to one mile during the day and up to
five miles at night depending upon the visibility
conditions. (See FIG 2−1−6.)
FIG 2
−1−6
Tri
−Color Visual Approach Slope Indicator
Amber
Above Glide Path
On Glide Path
Below Glide Path
Amber
Green
Red
NOTE
−
1. Since the tri
−color VASI consists of a single light source which could possibly be confused with other light sources, pilots
should exercise care to properly locate and identify the light signal.
2. When the aircraft descends from green to red, the pilot may see a dark amber color during the transition from green to
red.
Page 19
AIM
4/3/14
2−1−5
Airport Lighting Aids
FIG 2
−1−7
Pulsating Visual Approach Slope Indicator
Above Glide Path
On Glide Path
Below Glide Path
Slightly Below Glide Path
Threshold
PULSATING WHITE
PULSATING RED
STEADY WHITE
STEADY RED
NOTE
−
Since the PVASI consists of a single light source which could possibly be confused with other light sources, pilots should
exercise care to properly locate and identify the light signal.
FIG 2
−1−8
Alignment of Elements
Below Glide Path
On Glide Path
Above Glide Path
d. Pulsating Systems.
Pulsating visual ap-
proach slope indicators normally consist of a single
light unit projecting a two−color visual approach
path into the final approach area of the runway upon
which the indicator is installed. The on glide path
indication is a steady white light. The slightly below
glide path indication is a steady red light. If the
aircraft descends further below the glide path, the red
light starts to pulsate. The above glide path indication
is a pulsating white light. The pulsating rate increases
as the aircraft gets further above or below the desired
glide slope. The useful range of the system is about
four miles during the day and up to ten miles at night.
(See FIG 2−1−7.)
e. Alignment of Elements Systems.
Alignment
of elements systems are installed on some small
general aviation airports and are a low−cost system
consisting of painted plywood panels, normally black
and white or fluorescent orange. Some of these
systems are lighted for night use. The useful range of
these systems is approximately three−quarter miles.
To use the system the pilot positions the aircraft so the
Page 20
AIM
4/3/14
2−1−6
Airport Lighting Aids
elements are in alignment. The glide path indications
are shown in FIG 2−1−8.
2
−
1
−
3. Runway End Identifier Lights (REIL)
REILs are installed at many airfields to provide rapid
and positive identification of the approach end of a
particular runway. The system consists of a pair of
synchronized flashing lights located laterally on each
side of the runway threshold. REILs may be either
omnidirectional or unidirectional facing the approach
area. They are effective for:
a.
Identification of a runway surrounded by a
preponderance of other lighting.
b.
Identification of a runway which lacks contrast
with surrounding terrain.
c.
Identification of a runway during reduced
visibility.
2
−
1
−
4. Runway Edge Light Systems
a.
Runway edge lights are used to outline the
edges of runways during periods of darkness or
restricted visibility conditions. These light systems
are classified according to the intensity or brightness
they are capable of producing: they are the High
Intensity Runway Lights (HIRL), Medium Intensity
Runway Lights (MIRL), and the Low Intensity
Runway Lights (LIRL). The HIRL and MIRL
systems have variable intensity controls, whereas the
LIRLs normally have one intensity setting.
b.
The runway edge lights are white, except on
instrument runways yellow replaces white on the last
2,000 feet or half the runway length, whichever is
less, to form a caution zone for landings.
c.
The lights marking the ends of the runway emit
red light toward the runway to indicate the end of
runway to a departing aircraft and emit green outward
from the runway end to indicate the threshold to
landing aircraft.
2
−
1
−
5. In
−
runway Lighting
a. Runway Centerline Lighting System
(RCLS).
Runway centerline lights are installed on
some precision approach runways to facilitate
landing under adverse visibility conditions. They are
located along the runway centerline and are spaced at
50−foot intervals. When viewed from the landing
threshold, the runway centerline lights are white until
the last 3,000 feet of the runway. The white lights
begin to alternate with red for the next 2,000 feet, and
for the last 1,000 feet of the runway, all centerline
lights are red.
b. Touchdown Zone Lights (TDZL).
Touch-
down zone lights are installed on some precision
approach runways to indicate the touchdown zone
when landing under adverse visibility conditions.
They consist of two rows of transverse light bars
disposed symmetrically about the runway centerline.
The system consists of steady−burning white lights
which start 100 feet beyond the landing threshold and
extend to 3,000 feet beyond the landing threshold or
to the midpoint of the runway, whichever is less.
c. Taxiway Centerline Lead
−Off Lights. Taxi-
way centerline lead−off lights provide visual
guidance to persons exiting the runway. They are
color−coded to warn pilots and vehicle drivers that
they are within the runway environment or
instrument landing system/microwave landing sys-
tem (ILS/MLS) critical area, whichever is more
restrictive. Alternate green and yellow lights are
installed, beginning with green, from the runway
centerline to one centerline light position beyond the
runway holding position or ILS/MLS critical area
holding position.
d. Taxiway Centerline Lead
−On Lights. Taxi-
way centerline lead−on lights provide visual
guidance to persons entering the runway. These
“lead−on” lights are also color−coded with the same
color pattern as lead−off lights to warn pilots and
vehicle drivers that they are within the runway
environment or instrument landing system/micro-
wave landing system (ILS/MLS) critical area,
whichever is more conservative. The fixtures used for
lead−on lights are bidirectional, i.e., one side emits
light for the lead−on function while the other side
emits light for the lead−off function. Any fixture that
emits yellow light for the lead−off function must also
emit yellow light for the lead−on function.
(See FIG 2−1−14.)
e. Land and Hold Short Lights.
Land and hold
short lights are used to indicate the hold short point on
certain runways which are approved for Land and
Hold Short Operations (LAHSO). Land and hold
short lights consist of a row of pulsing white lights
installed across the runway at the hold short point.
Where installed, the lights will be on anytime
Page 21
AIM
4/3/14
2−1−7
Airport Lighting Aids
LAHSO is in effect. These lights will be off when
LAHSO is not in effect.
REFERENCE
−
AIM, Pilot Responsibilities When Conducting Land and Hold Short
Operations (LAHSO), Paragraph 4
−3−11.
2
−
1
−
6. Runway Status Light (RWSL)
System
a.
Introduction.
RWSL is a fully automated system that provides
runway status information to pilots and surface
vehicle operators to clearly indicate when it is unsafe
to enter, cross, takeoff from, or land on a runway. The
RWSL system processes information from surveil-
lance systems and activates Runway Entrance Lights
(REL), Takeoff Hold Lights (THL), Runway
Intersection Lights (RIL), and Final Approach
Runway Occupancy Signal (FAROS) in accordance
with the position and velocity of the detected surface
traffic and approach traffic. REL, THL, and RIL are
in-pavement light fixtures that are directly visible to
pilots and surface vehicle operators. FAROS alerts
arriving pilots that the approaching runway is
occupied by flashing the Precision Approach Path
Indicator (PAPI). FAROS may be implemented as an
add-on to the RWSL system or implemented as a
stand-alone system at airports without a RWSL
system. RWSL is an independent safety enhancement
that does not substitute for or convey an ATC
clearance. Clearance to enter, cross, takeoff from,
land on, or operate on a runway must still be received
from ATC. Although ATC has limited control over
the system, personnel do not directly use and may not
be able to view light fixture activations and
deactivations during the conduct of daily ATC
operations.
b.
Runway Entrance Lights (REL): The REL
system is composed of flush mounted, in-pavement,
unidirectional light fixtures that are parallel to and
focused along the taxiway centerline and directed
toward the pilot at the hold line. An array of REL
lights include the first light at the hold line followed
by a series of evenly spaced lights to the runway edge;
one additional light at the runway centerline is in line
with the last two lights before the runway edge (see
FIG 2−1−9 and FIG 2−1−12). When activated, the
red lights indicate that there is high speed traffic on
the runway or there is an aircraft on final approach
within the activation area.
1.
REL Operating Characteristics − Departing
Aircraft:
When a departing aircraft reaches a site adaptable
speed of approximately 30 knots, all taxiway
intersections with REL arrays along the runway
ahead of the aircraft will illuminate (see FIG 2−1−9).
As the aircraft approaches an REL equipped taxiway
intersection, the lights at that intersection extinguish
approximately 3 to 4 seconds before the aircraft
reaches it. This allows controllers to apply
“anticipated separation” to permit ATC to move
traffic more expeditiously without compromising
safety. After the aircraft is declared “airborne” by the
system, all REL lights associated with this runway
will extinguish.
2.
REL Operating Characteristics − Arriving
Aircraft:
When an aircraft on final approach is approximately
1 mile from the runway threshold, all sets of taxiway
REL light arrays that intersect the runway illuminate.
The distance is adjustable and can be configured for
specific operations at particular airports. Lights
extinguish at each equipped taxiway intersection
approximately 3 to 4 seconds before the aircraft
reaches it to apply anticipated separation until the
aircraft has slowed to approximately 80 knots (site
adjustable parameter). Below 80 knots, all arrays that
are not within 30 seconds of the aircraft’s forward
path are extinguished. Once the arriving aircraft
slows to approximately 34 knots (site adjustable
parameter), it is declared to be in a taxi state, and all
lights extinguish.
3.
What a pilot would observe: A pilot at or
approaching the hold line to a runway will observe
RELs illuminate and extinguish in reaction to an
aircraft or vehicle operating on the runway, or an
arriving aircraft operating less than 1 mile from the
runway threshold.
4.
When a pilot observes the red lights of the
REL, that pilot will stop at the hold line or remain
stopped. The pilot will then contact ATC for
resolution if the clearance is in conflict with the
lights. Should pilots note illuminated lights under
circumstances when remaining clear of the runway is
impractical for safety reasons (for example, aircraft
is already on the runway), the crew should proceed
according to their best judgment while understanding
the illuminated lights indicate the runway is unsafe to
Page 22
AIM
4/3/14
2−1−8
Airport Lighting Aids
enter or cross. Contact ATC at the earliest possible
opportunity.
FIG 2
−1−9
Runway Status Light System
c.
Takeoff Hold Lights (THL) : The THL system
is composed of flush mounted, in-pavement,
unidirectional light fixtures in a double longitudinal
row aligned either side of the runway centerline
lighting. Fixtures are focused toward the arrival end
of the runway at the “line up and wait” point. THLs
extend for 1,500 feet in front of the holding aircraft
starting at a point 375 feet from the departure
threshold (see FIG 2−1−13). Illuminated red lights
provide a signal, to an aircraft in position for takeoff
or rolling, that it is unsafe to takeoff because the
runway is occupied or about to be occupied by
another aircraft or ground vehicle. Two aircraft, or a
surface vehicle and an aircraft, are required for the
lights to illuminate. The departing aircraft must be in
position for takeoff or beginning takeoff roll. Another
aircraft or a surface vehicle must be on or about to
cross the runway.
1.
THL Operating Characteristics − Departing
Aircraft:
THLs will illuminate for an aircraft in position for
departure or departing when there is another aircraft
or vehicle on the runway or about to enter the runway
(see FIG 2−1−9.) Once that aircraft or vehicle exits
the runway, the THLs extinguish. A pilot may notice
lights extinguish prior to the downfield aircraft or
vehicle being completely clear of the runway but still
moving. Like RELs, THLs have an “anticipated
separation” feature.
NOTE
−
When the THLs extinguish, this is not clearance to begin a
takeoff roll. All takeoff clearances will be issued by ATC.
2.
What a pilot would observe: A pilot in
position to depart from a runway, or has begun takeoff
roll, will observe THLs illuminate in reaction to an
aircraft or vehicle on the runway or entering or
crossing it. Lights will extinguish when the runway is
clear. A pilot may observe several cycles of
illumination and extinguishing depending on the
amount of crossing traffic.
3.
When a pilot observes the red light of the
THLs, the pilot should safely stop if it’s feasible or
remain stopped. The pilot must contact ATC for
resolution if any clearance is in conflict with the
lights. Should pilots note illuminated lights while in
takeoff roll and under circumstances when stopping
is impractical for safety reasons, the crew should
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proceed according to their best judgment while
understanding the illuminated lights indicate that
continuing the takeoff is unsafe. Contact ATC at the
earliest possible opportunity.
d.
Runway Intersection Lights (RIL): The RIL
system is composed of flush mounted, in−pavement,
unidirectional light fixtures in a double longitudinal
row aligned either side of the runway centerline
lighting in the same manner as THLs. Their
appearance to a pilot is similar to that of THLs.
Fixtures are focused toward the arrival end of the
runway, and they extend for 3,000 feet in front of an
aircraft that is approaching an intersecting runway.
They end at the Land and Hold Short Operation
(LASHO) light bar or the hold short line for the
intersecting runway.
1.
RIL Operating Characteristics − Departing
Aircraft:
RILs will illuminate for an aircraft departing or in
position to depart when there is high speed traffic
operating on the intersecting runway (see
FIG 2−1−9). Note that there must be an aircraft or
vehicle in a position to observe the RILs for them to
illuminate. Once the conflicting traffic passes
through the intersection, the RILs extinguish.
2.
RIL Operating Characteristics − Arriving
Aircraft:
RILs will illuminate for an aircraft that has landed and
is rolling out when there is high speed traffic on the
intersecting runway that is
$5 seconds of meeting at
the intersection. Once the conflicting traffic passes
through the intersection, the RILs extinguish.
3.
What a pilot would observe: A pilot departing
or arriving will observe RILs illuminate in reaction to
the high speed traffic operation on the intersecting
runway. The lights will extinguish when that traffic
has passed through the runway intersection.
4.
Whenever a pilot observes the red light of the
RIL array, the pilot will stop before the LAHSO stop
bar or the hold line for the intersecting runway. If a
departing aircraft is already at high speed in the
takeoff roll when the RILs illuminate, it may be
impractical to stop for safety reasons. The crew
should safely operate according to their best
judgment while understanding the illuminated lights
indicate that continuing the takeoff is unsafe. Contact
ATC at the earliest possible opportunity.
e.
The Final Approach Runway Occupancy Signal
(FAROS) is communicated by flashing of the
Precision Approach Path Indicator (PAPI) (see FIG
2-1-9). When activated, the light fixtures of the PAPI
flash or pulse to indicate to the pilot on an approach
that the runway is occupied and that it may be unsafe
to land.
NOTE
−
FAROS is an independent automatic alerting system that
does not rely on ATC control or input.
1.
FAROS Operating Characteristics:
If an aircraft or surface vehicle occupies a FAROS
equipped runway, the PAPI(s) on that runway will
flash. The glide path indication will not be affected,
and the allotment of red and white PAPI lights
observed by the pilot on approach will not change.
The FAROS system will flash the PAPI when traffic
enters the runway and there is an aircraft on approach
and within 1.5 nautical miles of the landing threshold.
2.
What a pilot would observe: A pilot on
approach to the runway will observe the PAPI flash if
there is traffic on the runway and will notice the PAPI
ceases to flash when the traffic moves outside the
hold short lines for the runway.
3.
When a pilot observes a flashing PAPI at 500
feet above ground level (AGL), the contact height,
the pilot must look for and acquire the traffic on the
runway. At 300 feet AGL, the pilot must contact ATC
for resolution if the FAROS indication is in conflict
with the clearance. If the PAPI continues to flash, the
pilot must execute an immediate “go around” and
contact ATC at the earliest possible opportunity.
f.
Pilot Actions:
1.
When operating at airports with RWSL, pilots
will operate with the transponder “On” when
departing the gate or parking area until it is shutdown
upon arrival at the gate or parking area. This ensures
interaction with the FAA surveillance systems such
as ASDE-X which provide information to the RWSL
system.
2.
Pilots must always inform the ATCT when
they have either stopped, are verifying a landing
clearance, or are executing a go-around due to RWSL
or FAROS indication that are in conflict with ATC
instructions. Pilots must request clarification of the
taxi, takeoff, or landing clearance.
3.
Never cross over illuminated red lights.
Under normal circumstances, RWSL will confirm the
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pilot’s taxi or takeoff clearance previously issued by
ATC. If RWSL indicates that it is unsafe to takeoff
from, land on, cross, or enter a runway, immediately
notify ATC of the conflict and re-confirm the
clearance.
4.
Do not proceed when lights have extin-
guished without an ATC clearance. RWSL verifies an
ATC clearance; it does not substitute for an ATC
clearance.
5.
Never land if PAPI continues to flash.
Execute a go around and notify ATC.
g.
ATC Control of RWSL System:
1.
Controllers can set in−pavement lights to one
of five (5) brightness levels to assure maximum
conspicuity under all visibility and lighting condi-
tions. REL, THL, and RIL subsystems may be
independently set.
2.
System lights can be disabled should RWSL
operations impact the efficient movement of air
traffic or contribute, in the opinion of the assigned
ATC Manager, to unsafe operations. REL, THL, RIL,
and FAROS light fixtures may be disabled separately.
Disabling of the FAROS subsystem does not
extinguish PAPI lights or impact its glide path
function. Whenever the system or a component is
disabled, a NOTAM must be issued, and the
Automatic Terminal Information System (ATIS)
must be updated.
2
−
1
−
7. Stand-Alone Final Approach
Runway Occupancy Signal (FAROS)
a.
Introduction:
The stand-alone FAROS system is a fully automated
system that provides runway occupancy status to
pilots on final approach to indicate whether it may be
unsafe to land. When an aircraft or vehicle is detected
on the runway, the Precision Approach Path Indicator
(PAPI) light fixtures flash as a signal to indicate that
the runway is occupied and that it may be unsafe to
land. The stand-alone FAROS system is activated by
localized or comprehensive sensors detecting aircraft
or ground vehicles occupying activation zones.
The stand-alone FAROS system monitors specific
areas of the runway, called activation zones, to
determine the presence of aircraft or ground vehicles
in the zone (see FIG 2−1−10). These activation zones
are defined as areas on the runway that are frequently
occupied by ground traffic during normal airport
operations and could present a hazard to landing
aircraft. Activation zones may include the full-length
departure position, the midfield departure position, a
frequently crossed intersection, or the entire runway.
Pilots can refer to the airport specific FAROS pilot
information sheet for activation zone configuration.
FIG 2
−1−10
FAROS Activation Zones
Clearance to land on a runway must be issued by Air
Traffic Control (ATC). ATC personnel have limited
control over the system and may not be able to view
the FAROS signal.
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b.
Operating Characteristics:
If an aircraft or ground vehicle occupies an activation
zone on the runway, the PAPI light fixtures on that
runway will flash. The glide path indication is not
affected, i.e. the configuration of red and white PAPI
lights observed by the pilot on approach does not
change. The stand-alone FAROS system flashes the
PAPI lights when traffic occupies an activation zone
whether or not there is an aircraft on approach.
c.
Pilot Observations:
A pilot on approach to the runway observes the PAPI
lights flashing if there is traffic on the runway
activation zones and notices the PAPI lights cease to
flash when the traffic moves outside the activation
zones.
A pilot on departure from the runway should
disregard any observations of flashing PAPI lights.
d.
Pilot Actions:
When a pilot observes a flashing PAPI at 500 feet
above ground level (AGL), the pilot must look for and
attempt to acquire the traffic on the runway. At 300
feet AGL, the pilot must contact ATC for resolution
if the FAROS indication is in conflict with the
clearance (see FIG 2−1−11). If the PAPI lights
continue to flash and the pilot cannot visually
determine that it is safe to land, the pilot must execute
an immediate “go around”. As with operations at
non-FAROS airports, it is always the pilot’s
responsibility to determine whether or not it is safe to
continue with the approach and to land on the runway.
FIG 2
−1−11
FAROS Glide Slope Action Points
Pilots should inform the ATCT when they have
executed a go around due to a FAROS indication that
is in conflict with ATC instructions.
NOTE
−
At this time, the stand-alone FAROS system is not widely
implemented and is used for evaluation purposes.
2
−
1
−
8. Control of Lighting Systems
a.
Operation of approach light systems and
runway lighting is controlled by the control tower
(ATCT). At some locations the FSS may control the
lights where there is no control tower in operation.
b.
Pilots may request that lights be turned on or off.
Runway edge lights, in−pavement lights and
approach lights also have intensity controls which
may be varied to meet the pilots request. Sequenced
flashing lights (SFL) may be turned on and off. Some
sequenced flashing light systems also have intensity
control.
2
−
1
−
9. Pilot Control of Airport Lighting
Radio control of lighting is available at selected
airports to provide airborne control of lights by
keying the aircraft’s microphone. Control of lighting
systems is often available at locations without
specified hours for lighting and where there is no
control tower or FSS or when the tower or FSS is
closed (locations with a part−time tower or FSS) or
specified hours. All lighting systems which are radio
controlled at an airport, whether on a single runway
or multiple runways, operate on the same radio
frequency. (See TBL 2−1−1 and TBL 2−1−2.)
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FIG 2
−1−12
Runway Entrance Lights
FIG 2
−1−13
Takeoff Hold Lights