Like flying any other IAP , the pilot must see and avoid any
obstacles in the visual segment during transition to landing.
A constant-rate descent has many safety advantages over
non-precision approaches that require multiple level-offs at
stepdown fixes or manually calculating rates of descent. A
stabilized approach can be maintained from the FAF to the
landing when a constant-rate descent is used. Additionally,
the use of an electronic vertical path produced by onboard
avionics can serve to reduce CFIT, and minimize the
effects of visual illusions on approach and landing. Some
countries even mandate the use of continuous descent
final approaches (CDFAs) on non-precision approaches.
Wide Area Augmentation System
The Wide Area Augmentation System (WAAS) offers
an opportunity for airports to gain ILS like approach
capability without the purchase or installation of any
ground-based navigation equipment at the airport.
Today, WAAS is already being used at more than 900
runways across the United States to achieve minimums
as low as 200 feet height above HAT/one-half mile
visibility.
Benefits Of WAAS In The Airport Environment
WAAS is a navigation service using a combination of GPS
satellites and the WAAS geostationary satellites to improve
the navigational service provided by GPS. WAAS achieved
initial operating capability (IOC) in 2003. The system is
owned and operated by the FAA and provided free of direct
user charges to users across the United States and most of
Canada and Mexico.
WAAS improves the navigational system accuracy for
en route, terminal, and approach operations over all the
continental United States and significant portions of Alaska,
Canada, and Mexico. This new navigational technology
supports vertically-guided instrument approaches to all
qualifying runways in the United States. Vertically-guided
approaches reduce pilot workload and provide safety
benefits compared to non-precision approaches. The WAAS
enabled vertically guided approach procedures are called
LPV, which stands for “localizer performance with vertical
guidance, ”and provide ILS equivalent approach minimums
as low as 200 feet at qualifying airports. Actual minimums
are based on an airport’s current infrastructure, as well as
an evaluation of any existing obstructions. The FAA plans to
publish 300 WAAS approach procedures per year to provide
service to all qualifying instrument runways within the NAS.
Advantages Of WAAS Enabled LPV Approaches
The advantages of WAAS enabled LPV approaches include:
• LPV procedures have no requirement for ground-
based transmitters at the airport.
• No consideration needs to be given to the placement
of navigation facility, maintenance of clear zones
Ranging sources
Status information
GBAS reference receivers
GBAS ground facility
Omnidirectional VHF data broadcast (VDB) signal
GPS satellites
Differential corrections, integrity
data and path definition
Figure 4-13. GBAS architecture.
around the facility, or access to the facility for
maintenance.
• LPV approaches eliminate the need for critical area
limitations associated with an ILS.
• From a pilot’s viewpoint, an LPV approach looks
and flies like an ILS, but the WAAS approach is more
stable than that of an ILS.
• WAAS equipped users can fly RNAV and basic
required navigation performance (RNP) procedures,
as well as LPV procedures, and the avionics costs
are relatively inexpensive considering the total
navigation solution provided.
RNAV (GPS) approach charts normally have four lines
of approach minimums: LPV, LNAV/VNAV, LNAV, and
Circling. Figure 4-12 shows how these minimums might
be presented on an approach chart, with the exception
of Ground Based Augmentation System (GBAS) Landing
System (GLS). This enables as many GPS equipped aircraft
to use the procedure as possible and provides operational
flexibility if WAAS becomes unavailable. Some aircraft may
only be equipped with GPS receivers so they can fly to the
LNAV MDA. Some aircraft equipped with GPS and FMS
(with approach-certified barometric vertical navigation, or
Baro-VNAV) can fly to the LNAV/VNAV MDA. Flying a WAAS
LPV approach requires an aircraft with WAAS-LPV avionics.
If for some reason the WAAS service becomes unavailable,
all GPS or WAAS equipped aircraft can revert to the LNAV
MDA and land safely using GPS only, which is available
nearly 100 percent of the time. Some locations will have
an LP line of minima on an RNAV (GPS) approach chart; but
the use of LP is being phased out. At locations with obstacle
penetrations in the missed approach segment, there might
be two lines of minima for the same type of navigation- one
line with higher approach minima without a specified climb
gradient and another line with lower approach minima with
a specified climb gradient in the event of missed approach.
LPV identifies WAAS approach with vertical guidance (APV)
approach minimums with electronic lateral and vertical
guidance capability. LPV is used for approaches constructed
with WAAS criteria where the value for the vertical alarm
limit is more than 12 meters and less than 50 meters.
WAAS avionics equipment approved for LPV approaches is
required for this type of approach. The lateral guidance is
equivalent to localizer accuracy, and the protected area is
considerably smaller than the protected area for the present
LNAV and LNAV/VNAV lateral protection. Aircraft can fly this
minima line with a statement in the AFM that the installed
equipment supports LPV approaches. In Figure 4-12, notice
the WAAS information shown in the top left corner of the
pilot briefing information on the chart depicted. Below the
term WAAS is the WAAS channel number (CH 56202), and
the WAAS approach identifier (W35A), indicating Runway
35L in this case, and then a letter to designate the first in a
series of procedures to that runway [Figure 4-12].
LNAV/VNAV identifies APV minimums developed to
accommodate an RNAV IAP with vertical guidance, usually
provided by approach certified Baro-VNAV, but with vertical
and lateral integrity limits larger than a precision approach
or LPV. Many RNAV systems that have RNP 0.3 or less
approach capability are specifically approved in the AFM.
Airplanes that are commonly approved in these types of
operations include Boeing 737NG, 767, and 777, as well as
the Airbus A300 series. Landing minimums are shown as
DAs because the approaches are flown using an electronic
glide path. Other RNAV systems require special approval. In
some cases, the visibility minimums for LNAV/VNAV might
be greater than those for LNAV only. This situation occurs
because DA on the LNAV/VNAV vertical descent path is
farther away from the runway threshold than the LNAV
MDA missed approach point.
Also shown in Figure 4-12, is the LNAV minimums line. This
minimum is for lateral navigation only, and the approach
minimum altitude is published as a MDA. LNAV provides
the same level of service as the present GPS stand alone
approaches. LNAV supports the following systems: WAAS,
when the navigation solution will not support vertical
navigation; and GPS navigation systems which are
presently authorized to conduct GPS approaches.
Circling minimums that may be used with any type of
approach approved RNAV equipment when publication of
straight-in approach minimums is not possible.
Ground-Based Augmentation System (GBAS)
The United States version of the Ground-Based
Augmentation System (GBAS) has traditionally been
referred to as the Local Area Augmentation System (LAAS).
The worldwide community has adopted GBAS as the official
term for this type of navigation system. To coincide with
international terminology, the FAA is also adopting the term
GBAS to be consistent with the international community.
GBAS is a ground-based augmentation to GPS that focuses
its service on the airport area (approximately a 20–30 mile
radius) for precision approach, DPs, and terminal area
operations. It broadcasts its correction message via a very
high frequency (VHF) radio data link from a ground-based
transmitter. GBAS yields the extremely high accuracy,
availability, and integrity necessary for Category I, II, and
III precision approachesand provides the ability for flexible,
curved approach paths. GBAS demonstrated accuracy is
less than one meter in both the horizontal and vertical
axis. [Figure 4-13]
Figure 4-14. GLS approach at Newark, New Jersey.
Figure 4-15. RNAV RNP approach procedure with curved flight tracks.
Figure 4-16. North Platte Regional (KLBF), North Platte, Nebraska, RNAV (GPS) RWY 30.
The GBAS augments the GPS to improve aircraft safety
during airport approaches and landings. It is expected
that the end state configuration will pinpoint the aircraft’s
position to within one meter or less with a significant
improvement in service flexibility and user operating costs.
GBAS is comprised of ground equipment and avionics.
The ground equipment includes four reference receivers, a
GBAS ground facility, and a VHF data broadcast transmitter.
This ground equipment is complemented by GBAS avionics
installed on the aircraft. Signals from GPS satellites are
received by the GBAS GPS reference receivers (four
receivers for each GBAS) at the GBAS equipped airport.
The reference receivers calculate their position using GPS.
The GPS reference receivers and GBAS ground facility work
together to measure errors in GPS provided position.
The GBAS ground facility produces a GBAS correction
message based on the difference between actual and GPS
calculated position. Included in this message is suitable
integrity parameters and approach path information.
This GBAS correction message is then sent to a VHF data
broadcast (VDB) transmitter. The VDB broadcasts the GBAS
signal throughout the GBAS coverage area to avionics in
GBAS equipped aircraft. GBAS provides its service to a
local area (approximately a 20–30 mile radius). The signal
coverage is designed support the aircraft’s transition from
en route airspace into and throughout the terminal area
airspace.
The GBAS equipment in the aircraft uses the corrections
provided on position, velocity, and time to guide the
aircraft safely to the runway. This signal provides ILS look
alike guidance as low as 200 feet above touchdown.
GBAS will eventually support landings all the way to the
runway surface. Figure 4-14 is an example of a GBAS (LAAS)
approach into Newark, New Jersey.
Required Navigation Performance (RNP)
The operational advantages of RNP include accuracy,
onboard performance monitoring and alerting which
provide increased navigation precision and lower
minimums than conventional RNAV. RNP DAs can be
as low as 250 feet with visibilities as low as 3/4 SM.
Besides lower minimums, the benefits of RNP include
improved obstacle clearance limits, as well as reduced
pilot workload. When RNP capable aircraft fly an accurate,
repeatable path, ATC can be confident that these aircraft
are at a specific position, thus maximizing safety and
increasing capacity.
To attain the benefits of RNP approach procedures, a key
component is curved flight tracks. Constant radius turns
around a fix are called “radius-to-fix legs (RF legs). ”These
turns, which are encoded into the navigation database,
allow the aircraft to avoid critical areas of terrain or
conflicting airspace while preserving positional accuracy
by maintaining precise, positive course guidance along
the curved track. The introduction of RF legs into the
design of terminal RNAV procedures results in improved
use of airspace and allows procedures to be developed to
and from runways that are otherwise limited to traditional
linear flight paths or, in some cases, not served by an IFR
procedure at all. Navigation systems with RF capability
are a prerequisite to flying a procedure that includes an
RF leg. Refer to the notes box of the pilot briefing portion
of the approach chart in Figure 4-15.
In the United States, operators who seek to take advantage
of RNP approach procedures must meet the special
RNP requirements outlined in FAA AC 90-101, Approval
Guidance for RNP Procedures with Authorization Required
(AR). Currently, most new transport category airplanes
receive an airworthiness approval for RNP operations.
However, differences can exist in the level of precision that
each system is qualified to meet. Each individual operator
is responsible for obtaining the necessary approval and
authorization to use these instrument flight procedures
with navigation databases.
RNAV Approach Authorization
Like any other authorization given to air carriers and Part 91
operators, the authorization to use VNAV on a conventional
non-precision approach, RNAV approaches, or LNAV/VNAV
approaches is found in that operator’s OpSpecs, AFM, or
other FAA-approved documents. There are many different
levels of authorizations when it comes to the use of RNAV
approach systems. The type of equipment installed in the
aircraft, the redundancy of that equipment, its operational
status, the level of flight crew training, and the level of the
operator’s FAA authorization are all factors that can affect
a pilot’s ability to use VNAV information on an approach.
Because most Part 121, 125, 135, and 91 flight departments
include RNAV approach information in their pilot training
programs, a flight crew considering an approach to
North Platte, Nebraska, using the RNAV (GPS) RWY 30
approach shown in Figure 4-16, would already know which
minimums they were authorized to use. The company’s
OpSpecs, FOM, and the AFM for the pilot’s aircraft would
dictate the specific operational conditions and procedures
by which this type of approach could be flown.
There are several items of note that are specific to this type
of approach that should be considered and briefed. One
is the terminal arrival area (TAA) that is displayed in the
approach planview. TAAs, discussed later in this chapter,
depict the boundaries of specific arrival areas, and the
MIA for those areas. The TAAs should be included in an
IAP briefing in the same manner as any other IFR transition
altitude. It is also important to note that the altitudes listed
in the TAAs should be referenced in place of the MSAs on
the approach chart for use in emergency situations.
In addition to the obvious differences contained in the
planview of Figure 4-16, RNAV (GPS) approach procedure
example, pilots should be aware of the issues related to
Baro-VNAV and RNP . The notes section of the procedure in
the example contains restrictions relating to these topics.
RNP values for each individual leg of the procedure, defined
by the procedure design criteria for containment purposes,
are encoded into the aircraft’s navigation database.
Applicable landing minimums are shown in a normal
manner along with the associated RNP value in the landing
minimums section.
RNP required sensors, FMS capabilities, and relevant
procedure notes are included in the Pilot Briefing
Information procedure notes section. [Figure 4-15] RNP
AR requirements are highlighted in large, bold print.
RNP procedures are sequenced in the same manner as
RNAV (GPS) procedures. Procedure title “RNAV” includes
parenthetical “(RNP)” terminology. RF legs can be used in
any segment of the procedure (transition, intermediate,
final, or missed approach). RF leg turn directions (left or
right) are not noted in the planview because the graphic
depiction of the flight tracks is intuitive. Likewise, the arc
center points, arc radius, and associated RF leg performance
limits, such as bank angles and speeds are not depicted
because these aircraft performance characteristics are
encoded in the navigation database. RNP values for each
individual leg of the procedure, defined by the procedure
design criteria for containment purposes, are encoded
into the aircraft's navigation database. Applicable landing
minimums are shown in a normal manner along with the
associated RNP value in the landing minimums section.
When more than one set of RNP landing minimums is
available and an aircrew is able to achieve lower RNP
through approved means, the available (multiple) sets of
RNP minimums are listed with the lowest set shown first;
remaining sets shown in ascending order, based on the
RNP value. On this particular procedure, lateral and vertical
course guidance from the DA to the Runway Waypoint (LTP)
is provided by the aircraft’s FMS and onboard navigation
database; however, any continued flight below the DA
to the landing threshold is to be conducted under VMC.
[Figure 4-15]
Baro-VNAV
Baro-VNAV is an RNAV system function that uses barometric
altitude information from the aircraft’s altimeter to
compute and present a vertical guidance path to the pilot.
The specified vertical path is computed as a geometric
path, typically computed between two waypoints or
an angle based computation from a single waypoint.
Operational approval must also be obtained for Baro−
VNAV systems to operate to the LNAV/VNAV minimums.
Baro−VNAV may not be authorized on some approaches
due to other factors, such as no local altimeter source being
available. Baro−VNAV is not authorized on LPV procedures.
For the RNAV (GPS) RWY 30 approach, the note “DME/
DME RNP-0.3 NA” prohibits aircraft that use only DME/
DME sensors for RNAV from conducting the approach.
[Figure 4-16]
Because these procedures can be flown with an approach
approved RNP system and “RNP” is not sensor specific, it
was necessary to add this note to make it clear that those
aircraft deriving RNP 0.3 using DME/DME only are not
authorized to conduct the procedure.
The least accurate sensor authorized for RNP navigation
Figure 4-17. Example of LNAV and Circling Minima lower than LNAV/VNAV
DA. Harrisburg International RNAV (GPS) Runway 13.
Figure 4-18. Explanation of Minima.
NOT FOR NAVIGATION
NOT FOR NAVIGATION
EC-3, 18 NOV 2010 to 16 DEC 2010
C-3, 18 NOV 2010 to 16 DEC 2010
EC-3, 18 NOV 2010 to 16 DEC 2010
Airport sketch
EC-3, 18 NOV 2010 to 16 DEC 2010
Figure 4-19. Airport sketch and diagram for Chicago O'Hare International.
is DME/DME. The necessary DME NAVAID ground
infrastructure may or may not be available at the airport of
intended landing. The procedure designer has a computer
program for determining the usability of DME based on
geometry and coverage. Where FAA flight inspection
successfully determines that the coverage and accuracy of
DME facilities support RNP , and that the DME signal meets
inspection tolerances, although there are none currently
published, the note “DME/DME RNP 0.3 Authorized” would
be charted. Where DME facility availability is a factor, the
note would read, “DME/DME RNP 0.3 Authorized; ABC and
XYZ required, ”meaning that ABC and XYZ DME facilities are
required to assure RNP 0.3.
Hot and Cold Temperature Limitations
A minimum and maximum temperature limitation is
published on procedures that authorize Baro−VNAV
operation. These temperatures represent the airport
temperature above or below which Baro−VNAV is not
authorized to LNAV/VNAV minimums unless temperature
compensation can be accomplished. As an example,
the limitation will read, uncompensated Baro−VNAV NA
below −11 °C (12 °F) or above 49 °C (120 °F). [Figure 4-15]
This information will be found in the upper left hand box
of the pilot briefing. When the temperature is above the
high temperature or below the low temperature limit,
Baro−VNAV may be used to provide a stabilized descent
to the LNAV MDA; however, extra caution should be used
in the visual segment to ensure a vertical correction is not
required. If the VGSI is aligned with the published glide
path, and the aircraft instruments indicate on glide path,
an above or below glide path indication on the VGSI may
indicate that temperature error is causing deviations to
the glide path. These deviations should be considered if
the approach is continued below the MDA.
Many systems which apply Baro−VNAV temperature
compensation only correct for cold temperature. In this
case, the high temperature limitation still applies. Also,
temperature compensation may require activation by
maintenance personnel during installation in order to be
functional, even though the system has the feature. Some
systems may have a temperature correction capability,
but correct the Baro−altimeter all the time, rather than
just on the final, which would create conflicts with other
aircraft if the feature were activated. Pilots should be
aware of compensation capabilities of the system prior to
disregarding the temperature limitations. The information
can be seen in the notes section in Figure 4-16.
In response to aviation industry concerns over cold weather
altimetry errors, the FAA conducted a risk analysis to
determine if current 14 CFR Part 97 instrument approach
procedures, in the NAS place aircraft at risk during cold
temperature operations. This study applied the coldest
recorded temperature at the given airports in the last five
years and specifically determined if there was a probability
that during these non-standard day operations, anticipated
altitude errors in a barometric altimetry system could
exceed the Required Obstacle Clearance (ROC) used on
procedure segment altitudes. If a probability of the ROC
being exceeded went above one percent on a segment
of the approach, a temperature restriction was applied to
that segment. In addition to the low probability that these
procedures will be required, the probability of the ROC
being exceeded precisely at an obstacle position is
extremely low, providing an even greater safety margin.
Pilots need to make an altitude correction to the published,
“at” , “at or above” and “at or below” altitudes on designated
segment(s) of IAPs listed at specific airports, on all
published procedures and runways, when the reported
airport temperature is at or below the published airport
cold temperature restriction.
This list may also be found at the bottom of the, “Terminal
Procedures Basic Search” page found at: http://www.faa.
gov/air_traffic/flight_info/aeronav/digital_products/dtpp/
search/
Pilots without temperature compensating aircraft
are responsible to calculate and make a manual cold-
temperature altitude correction to the designated
segment(s) of the approach using the AIM 7-2-3, ICAO Cold
Temperature Error Table.
No extrapolation above the 5000 ft column required. Pilots
should use the 5000 feet “height above airport in feet”
column for calculating corrections of greater than 5000
feet above reporting station. Pilots will add correction(s)
from the table to the segment altitude(s) and fly at the
new corrected altitude. PILOTS SHOULD NOT MAKE AN
ALTIMETER CHANGE to accomplish an altitude correction.
Pilots with temperature compensating aircraft must ensure
the system is on and operating for each segment requiring
an altitude correction. Pilots must ensure they are flying
at corrected altitude. If the system is not operating, the
pilot is responsible to calculate and apply a manual cold
weather altitude correction using the AIM 7-2-3 ICAO Cold
Temperature Error Table.
Pilots must report cold temperature corrected altitudes
to Air Traffic Control (ATC) whenever applying a cold
temperature correction on an intermediate segment and/
or a published missed approach final altitude. This should
be done on initial radio contact with the ATC issuing
approach clearance. ATC requires this information in
order to ensure appropriate vertical separation between
known traffic. ATC will not beproviding a cold temperature
correction to Minimum Vectoring Altitudes (MVA). Pilots
must not apply cold temperature compensation to ATC
assigned altitudes or when flying on radar vectors in lieu
of a published missed approach procedure unless cleared
by ATC.
Pilots should query ATC when vectors to an intermediate
segment are lower than the requested intermediate
segment altitude corrected for temperature. Pilots are
encouraged to self-announce corrected altitude when
flying into uncontrolled airfields.
The following are examples of appropriate pilot-to-ATC
communication when applying cold-temperature altitude
corrections:
On initial check-in with ATC providing approach clearance:
Hayden, CO (example below).
Intermediate segment: “Require 10600 ft. for cold
temperature operations until BEEAR” ,
Missed Approach segment: “Require final holding altitude,
10600 ft. on missed approach for cold temperature
operations”
Pilots cleared by ATC for an instrument approach
procedure; “Cleared the RNAV RWY 28 approach (from any
IAF)” . Hayden, CO (example below).
Intermediate Segment: “Level 10600 ft for cold temperature
operations inside HIPNA to BEEAR”
Pilots are not required to advise ATC if correcting on the
final segment only. Pilots must use the corrected MDA or
DA/DH as the minimum for an approach. Pilots must meet
the requirements in 14 CFR Part 91.175 in order to operate
below the corrected MDA or DA/DH. Pilots must see and
avoid obstacles when descending below the MDA.
The temperature restriction at a “Cold Temperature
Restricted Airport” is mutually exclusive from the charted
temperature restriction published for “uncompensated
baro-VNAV systems” on 14 CFR Part 97 RNAV (GPS) and
RNAV (RNP) approach charts. The charted temperature
restriction for uncompensated baro-VNAV systems is
applicable to the final segment LNAV/VNAV minima.
The charted temperature restriction must be followed
regardless of the cold temperature restricted airport
temperature.
Pilots are not required to calculate a cold temperature
altitude correction at any airport with a runway length of
2,500 feet or greater that is not included in the airports list
found at the URL above. Pilots operating into an airport
with a runway length less than 2,500 feet, may make a
cold temperature altitude correction in cold temperature
conditions.
Cold Temperature Restricted Airports: These airports are
listed in the FAA Notices To Airmen Publication (NTAP)
found here: https://www.faa.gov/air_traffic/publications/
notices/.
Airports are listed by ICAO code, Airport Name, Temperature
Restriction in Celsius/Fahrenheit and affected Segment.
One temperature may apply to multiple segments.
Italicized airports have two affected segments, each
with a different temperature restrictions. The warmest
temperature will be indicated on Airport IAPs next to a
snowflake symbol, in the United States Terminal
Procedure Publication. The ICON will be added to the TPPs
incrementally each charting cycle.
LNAV, LNAV/VNAV and Circling Minimums
There are some RNAV procedures with lower non-precision
LNAV minimums [Figure 4-17] than vertically-guided
LNAV/VNAV minimums. Circling procedures found on
the same approach chart may also have lower minimums
than the vertically-guided LNAV/VNAV procedure. Each
RNAV procedure is evaluated independently and different
approach segments have differing required obstacle
clearance (ROC) values, obstacle evaluation area (OEA)
dimensions and final segment types. Figure 4-18 explains
the differences.
Airport/Runway Information
Another important piece of a thorough approach briefing
is the discussion of the airport and runway environment.
A detailed examination of the runway length (this must
include the A/FD section of the CS for the landing distance
available), the intended turnoff taxiway, and the route of
taxi to the parking area, are all important briefing items.
In addition, runway conditions should be discussed. The
effect on the aircraft’s performance must be considered if
the runway is contaminated.
FAA approach charts include a runway sketch on each
approach chart to make important airport information
easily accessible to pilots. In addition, at airports that have
complex runway/taxiway configurations, a separate full-
page airport diagram is published.
The airport diagram also includes the latitude/longitude
information required for initial programming of FMS
equipment. The included latitude/longitude grid shows the
specific location of each parking area on the airport surface
for use in initializing FMS. Figure 4-19 shows the airport
sketch and diagram for Chicago-O’Hare International
Airport (KORD).
Pilots making approaches to airports that have this type of
complex runway and taxiway configuration must ensure
that they are familiar with the airport diagram prior to
initiating an instrument approach. A combination of poor
weather, high traffic volume, and high ground controller
workload makes the pilot’s job on the ground every bit as
critical as the one just performed in the air.
Instrument Approach Procedure (IAP) Briefing
A thorough instrument approach briefing greatly increases
the likelihood of a successful instrument approach. Most
Part 121, 125, and 135 operators designate specific items
to be included in an IAP briefing, as well as the order in
which those items are briefed.
Before an IAP briefing can begin, flight crews must decide
which procedure is most likely to be flown from the
information that is available to them. Most often, when
the flight is being conducted into an airport that has
ATIS information, the ATIS provides the pilots with the
approaches that are in use. If more than one approach
is in use, the flight crew may have to make an educated
guess as to which approach will be issued to them based
on the weather, direction of their arrival into the area, any
published airport NOTAMs, and previous contact with the
approach control facility. Aircrews can query ATC as to
which approach is to be expected from the controller. Pilots
may request specific approaches to meet the individual
needs of their equipment or regulatory restrictions at any
time and ATC will, in most cases, be able to accommodate
those requests, providing that workload and traffic permit.
If the flight is operating into an airport without a control
tower, the flight crew is occasionally given the choice of
any available instrument approach at the field. In these
cases, the flight crew must choose an appropriate approach
based on the expected weather, aircraft performance,
direction of arrival, airport NOTAMs, and previous
experience at the airport.
Navigation and Communication Radios
Once the anticipated approach and runway have been
selected, each crewmember sets up their side of the flight
deck. The pilots use information gathered from ATIS,
dispatch (if available), ATC, the specific approach chart
for the approach selected, and any other sources that
are available. Company regulations dictate how certain
things are set up and others are left up to pilot technique.
In general, the techniques used at most companies are
similar. This section addresses two-pilot operations. During
single-pilot IFR flights, the same items must be set up and
the pilot should still do an approach briefing to verify that
everything is set up correctly.
The number of items that can be set up ahead of time
depends on the level of automation of the aircraft and the
avionics available. In a conventional flight deck, the only
things that can be set up, in general, are the airspeed bugs
(based on performance calculations), altimeter bug (to DA,
DH, or MDA), go around thrust/power setting, the radio
altimeter bug (if installed and needed for the approach),
and the navigation/communication radios (if a standby
frequency selector is available). The standby side of the PF
navigation radio should be set to the primary NAVAID for
the approach and the PM navigation radio standby selector
should be set to any other NAVAIDs that are required or
available, and as dictated by company procedures, to
add to the overall situational awareness of the crew. The
ADF should also be tuned to an appropriate frequency
as required by the approach, or as selected by the crew.
Aircrews should, as much as possible, set up the instruments
for best success in the event of a vacuum or electrical failure.
For example, if the aircraft will only display Nav 1 on battery
or emergency power, aircrews should ensure that Nav 1 is
configured to the primary NAVAID for the final approach
to be flown.
Flight Management System (FMS)
In addition to the items that are available on a conventional
flight deck aircraft, glass flight deck aircraft, as well as
aircraft with an approved RNAV (GPS) system, usually
give the crew the ability to set the final approach course
for the approach selected and many other options to
increase situational awareness. Crews of FMS equipped
aircraft have many options available as far as setting up
the flight management computer (FMC), depending on
the type of approach and company procedures. The PF
usually programs the FMC for the approach and the PM
verifies the information. A menu of available approaches
is usually available to select from based on the destination
airport programmed at the beginning of the flight or a new
destination selected while en route.
The amount of information provided for the approach
varies from aircraft to aircraft, but the crew can make
modifications if something is not pre-programmed into the
computer, such as adding a MAP or even building an entire
approach for situational awareness purposes only. The PF
can also program a VNAV profile for the descent and LNAV
for segments that were not programmed during preflight,
such as a standard terminal arrival route (STAR) or expected
route to the planned approach. Any crossing restrictions
for the STAR might need to be programmed as well. The
most common crossing restrictions, whether mandatory
or “to be expected, ” are usually automatically programmed
when the STAR is selected, but can be changed by ATC at
any time. Other items that need to be set up are dictated
by aircraft-specific procedures, such as autopilot, auto-
throttles, auto-brakes, pressurization system, fuel system,
seat belt signs, anti-icing/ deicing equipment, and igniters.
Autopilot Modes
In general, an autopilot can be used to fly approaches
even if the FMC is inoperative (refer to the specific aircraft’s
minimum equipment list (MEL) to determine authorization
for operating with the FMC inoperative). Whether or not the
FMC is available, use of the autopilot should be discussed
during the approach briefing, especially regarding the use
of the altitude pre-selector and auto-throttles, if equipped.
The AFM for the specific aircraft outlines procedures and
limitations required for the use of the autopilot during an
instrument approach in that aircraft.
There are just as many different autopilot modes to climb
or descend the aircraft, as there are terms for these modes.
Some examples are level change (LVL CHG), vertical speed
(V/S), VNAV, and takeoff/go around (TO/GA). The pilot
controls the aircraft through the autopilot by selecting
pitch modes and/or roll modes, as well as the associated
auto-throttle modes. This panel, sometimes called a mode
control panel, is normally accessible to both pilots. Most
aircraft with sophisticated auto-flight systems and auto-
throttles have the capability to select modes that climb
with maximum climb thrust and descend with the throttles
at idle (LVL CHG, flight level change (FL CHG), and manage
level). They also have the capability to capture, or level
off at pre-selected altitudes, as well as track a LOC and
glideslope (G/S) or a VOR course. If the aircraft is RNAV-
equipped, the autopilot also tracks the RNAV-generated
course. Most of these modes are used at some point during
an instrument approach using the autopilot. Additionally,
these modes can be used to provide flight director (FD)
guidance to the pilot while hand-flying the aircraft.
For the purposes of this precision approach example, the
auto-throttles are engaged when the autopilot is engaged
and specific airspeed and configuration changes are not
discussed. The PF controls airspeed with the speed selector
on the mode control panel and calls for flaps and landing
gear as needed, which the PM selects. The example in
Figure 4-20 begins with the airplane 5 NM northwest of
KNUCK at 4,500 feet with the autopilot engaged, and the
flight has been cleared to track the Rwy 12 LOC inbound.
The current roll mode is LOC with the PF’s NAV radio tuned
to the LOC frequency of 109.3; and the current pitch mode
is altitude hold (ALT HOLD). Approach control clears the
aircraft for the approach. The PF makes no immediate
change to the autopilot mode to prevent the aircraft from
capturing a false glideslope; but the PM resets the altitude
selector to 1,700 feet. The aircraft remains level because
the pitch mode remains in ALT HOLD until another pitch
mode is selected. Upon reaching KNUCK, the PF selects
LVL CHG as the pitch mode. The auto-throttles retard to
idle as the airplane begins a descent. Approaching 1,700
feet, the pitch mode automatically changes to altitude
acquire (ALT ACQ) then to ALT HOLD as the aircraft levels
at 1,700 feet. In addition to slowing the aircraft and calling
for configuration changes, the PF selects approach mode
(APP). The roll mode continues to track the LOC and the
pitch mode remains in ALT HOLD; however, the G/S mode
arms. Selecting APP once the aircraft has leveled at the
FAF altitude is a suggested technique to ensure that the
aircraft captures the glideslope from below and that a false
glideslope is not being tracked.
The PF should have the aircraft fully configured for landing
before intercepting the glideslope to ensure a stabilized
approach. As the aircraft intercepts the glideslope the pitch
mode changes to G/S. Once the glideslope is captured
by the autopilot, the PM can select the missed approach
altitude in the altitude pre-selector, as requested by the PF.
The aircraft continues to track the glideslope. The minimum
altitude at which the PF is authorized to disconnect the
autopilot is aircraft specific. For example, 50 feet below
DA, DH, or MDA but not less than 50 feet AGL. The PF can
disconnect the autopilot at any time prior to reaching
this altitude during a CAT I approach. The initial missed
approach is normally hand flown with FD guidance unless
both autopilots are engaged for auto-land during a CAT II
or III approach.
The differences when flying the underlying non-precision
approach begin when the aircraft has leveled off at 1,700
feet. Once ALT HOLD is annunciated, the MDA is selected
by the PM as requested by the PF. It is extremely important
for both pilots to be absolutely sure that the correct
altitude is selected for the MDA so that the aircraft does not
inadvertently descend below the MDA. For aircraft that the
altitude pre-selector can only select 100 foot increments,
the MDA for this approach must be set at 700 feet instead
of 660 feet.
Vertical speed mode is used from the FAF inbound to
allow for more precise control of the descent. If the pilots
had not selected the MDA in the altitude pre-selector
window, the PF would not be able to input a V/S and the
aircraft would remain level. The autopilot mode changes
from ALT ACQ to ALT HOLD as the aircraft levels at 700 feet.
Once ALT HOLD is annunciated, the PF calls for the missed