er altitude without an approach clearance, request the
lower TAA altitude from ATC. Pilots not sure of the clear
ance should confirm their clearance with ATC or request a
specific clearance. Pilots entering the TAA with two−way
radio communications failure (14 CFR § 91.185, IFR Op
erations: Two−way Radio Communications Failure), must
maintain the highest altitude prescribed by 14 CFR §
91.185(c)(2) until arriving at the appropriate IAF.
Once cleared for the approach, pilots may descend in the
TAA sector to the minimum altitude depicted within the
defined area/subdivision, unless instructed otherwise by
air traffic control. Pilots should plan their descent within
the TAA to permit a normal descent from the IF/IAF to the
FAF.
U.S. Government charts depict TAAs using icons located
in the plan view outside the depiction of the actual ap
proach procedure. Use of icons is necessary to avoid ob
scuring any portion of the “T” procedure (altitudes, cours
es, minimum altitudes, etc.). The icon for each TAA area
will be located and oriented on the plan view with respect
to the direction of arrival to the approach procedure, and
will show all TAA minimum altitudes and sector/radius
subdivisions. The IAF for each area of the TAA is included
on the icon where it appears on the approach to help the
pilot orient the icon to the approach procedure. The IAF
name and the distance of the TAA area boundary from the
IAF are included on the outside arc of the TAA area icon.
TAAs may be modified from the standard size and shape
to accommodate operational or ATC requirements. Some
areas may be eliminated, while the other areas are ex
panded. The “T” design may be modified by the proce
dure designers where required by terrain or ATC consider
ations. For instance, the “T” design may appear more like
a regularly or irregularly shaped “Y, ” an upside down “L, ”
or an “I. ”
When an airway does not cross the lateral TAA boundar
ies, a feeder route will be established from an airway fix
or NAVAID to the TAA boundary to provide a transition
from the en route structure to the appropriate IAF. Each
feeder route will terminate at the TAA boundary and will
be aligned along a path pointing to the associated IAF.
Pilots should descend to the TAA altitude after crossing
the TAA boundary and cleared for the approach by ATC.
Each waypoint on the “T” is assigned a pronounceable 5−
letter name, except the missed approach waypoint. These
names are used for ATC communications, RNAV data
bases, and aeronautical navigation products. The missed
approach waypoint is assigned a pronounceable name
when it is not located at the runway threshold.
RNAV Approach Types
RNAV encompasses a variety of underlying navigation
systems and, therefore, approach criteria. This results in
different sets of criteria for the final approach segment
of various RNAV approaches. RNAV instrument approach
criteria address the following procedures:
• GPS overlay of pre-existing nonprecision approaches.
• VOR/DME based RNAV approaches.
• Stand-alone RNAV (GPS) approaches.
• RNAV (GPS) approaches with vertical guidance (APV).
• RNAV (GPS) precision approaches (WAAS and LAAS).
GPS Overlay of Nonprecision Approach
The original GPS approach procedures provided
authorization to fly non-precision approaches based
on conventional, ground-based NAVAIDs. Many of
these approaches have been converted to stand-alone
approaches, and the few that remain are identified by
the name of the procedure and “or GPS. ” These GPS non-
precision approaches are predicated upon the design
criteria of the ground-based NAVAID used as the basis of
the approach. As such, they do not adhere to the RNAV
design criteria for stand-alone GPS approaches, and are not
considered part of the RNAV (GPS) approach classification
for determining design criteria. [Figure 4-38]
GPS Stand-Alone/RNAV (GPS) Approach
The number of GPS stand-alone approaches continues to
decrease as they are replaced by RNAV approaches. RNAV
(GPS) approaches are named so that airborne navigation
databases can use either GPS or RNAV as the title of the
approach. This is required for non-GPS approach systems,
such as VOR/DME based RNAV systems. In the past,
these approaches were often referred to as "stand-alone
GPS" approaches. They are considered non-precision
approaches, offering only LNAV and circling minimums.
Precision minimums are not authorized, although LNAV/
VNAV minimums may be published and used as long as
the on-board system is capable of providing approach
approved VNAV. The RNAV (GPS) Runway 14 approach for
Lincoln, Nebraska, incorporates only LNAV and circling
minimums. [Figure 4-39]
For a non-vertically guided straight-in RNAV (GPS)
approach, the final approach course must be aligned within
15° of the extended runway centerline. The final approach
segment should not exceed 10 NM, and when it exceeds 6
NM, a stepdown fix is typically incorporated. A minimum
Figure 4-36. Terminal arrival area (TAA) design “basic T. ”
of 250 feet obstacle clearance is also incorporated into the
final approach segment for straight-in approaches, and a
maximum 400-ft/NM descent gradient is permitted.
The approach design criteria are different for approaches
that use vertical guidance provided by a Baro-VNAV
system. Because the Baro-VNAV guidance is advisory and
not primary, Baro-VNAV approaches are not authorized in
areas of hazardous terrain, nor are they authorized when
a remote altimeter setting is required. Due to the inherent
problems associated with barometric readings and cold
temperatures, these procedures are also temperature
limited. Additional approach design criteria for RNAV
Approach Construction Criteria can be found in the
appropriate FAA Order 8260-series orders.
Figure 4-37. RNAV approaches with and without TAAs.
RNAV (GPS) Approach Using WAAS
WAAS was commissioned in July 2003, with IOC. Although
precision approach capability is still in the future, WAAS
currently provides a type of APV known as LPV. WAAS can
support the following minima types: LPV, LNAV/VNAV,
LP , and LNAV. Approach minima as low as 200 feet HAT
and 1/2 SM visibility is possible, even though LPV is not
considered a precision approach. WAAS covers 95 percent
of the country 95 percent of the time.
Note: WAAS avionics receive an airworthiness approval
in accordance with Technical Standard Order (TSO)
C145, Airborne Navigation Sensors Using the Global
Positioning System (GPS) Augmented by the Satellite
Based Augmentation System (SBAS), or TSO-146, Stand-
Alone Airborne Navigation Equipment Using the Global
Positioning System (GPS) Augmented by the Satellite Based
Augmentation System (SBAS), and installed in accordance
with AC 20-138C, Airworthiness Approval of Positioning
and Navigation Systems.
Precision approach capability will become available as more
GBAS (LAAS) approach types become operational. GBAS
(LAAS) further increases the accuracy of GPS and improves
signal integrity warnings. Precision approach capability
requires obstruction planes and approach lighting systems
to meet Part 77 standards for ILS approaches. This delays
the implementation of RNAV (GPS) precision approach
capability due to the cost of certifying each runway.
ILS Approaches
Notwithstanding emerging RNAV technology, the ILS is the
most precise and accurate approach NAVAID currently in
use throughout the NAS. An ILS CAT I precision approach
allows approaches to be made to 200 feet above the TDZE
and with visibilities as low as 1,800 RVR; with CAT II and CAT
III approaches allowing descents and visibility minimums
that are even lower. Non-precision approach alternatives
cannot begin to offer the precision or flexibility offered by
an ILS. In order to further increase the approach capacity
of busy airports and exploit the maximum potential of ILS
technology, many different applications are in use.
An ILS system can accommodate up to 29 arrivals per hour
on a single runway. Two or three parallel runways operating
independently can double or triple the capacity of the
airport. For air commerce, this means greater flexibility
in scheduling passenger and cargo service. Capacity is
increased through the use of simultaneous or converging
ILS approaches, which are explained further in the
corresponding paragraphs below.
In order to successfully accomplish simultaneous or
converging ILS approaches, flight crews and ATC have
additional responsibilities. When simultaneous instrument
approaches are in use, ATC advises flight crews either
directly or through ATIS of the active runways. It is the
pilot’s responsibility to inform ATC if unable or unwilling
to execute a simultaneous approach. Pilots must comply
with all ATC requests in a timely manner and maintain
strict radio discipline, including using complete aircraft
call signs. It is also incumbent upon the flight crew to
notify ATC immediately of any problems relating to aircraft
communications or navigation systems. At the very least,
the approach procedure briefing should cover the entire
procedure including the approach name, runway number,
frequencies, final approach course, glideslope intercept
altitude, DA or DH, and the missed approach instructions.
The review of autopilot procedures is also appropriate
when making coupled ILS approaches.
As with all approaches, the primary navigation responsibility
falls upon the pilot in command. ATC instructions will be
limited to ensuring aircraft separation. Additionally, MAPs
are designed to diverge in order to protect all involved
aircraft. ILS approaches of all types are afforded the same
obstacle clearance protection and design criteria, no matter
how capacity is affected by simultaneous ILS approaches.
[Figure 4-40]
ILS Approach Categories
There are three general classifications of ILS approaches:
CAT I, CAT II, and CAT III (autoland). The basic ILS approach is
a CAT I approach and requires only that pilots be instrument
rated and current, and that the aircraft be equipped
appropriately. CAT II and CAT III ILS approaches have lower
minimums and require special certification for operators,
pilots, aircraft, and airborne/ground equipment. Because
of the complexity and high cost of the equipment, CAT III
ILS approaches are used primarily in air carrier and military
operations. [Figure 4-41]
CAT II and III Approaches
The primary authorization and minimum RVRs allowed
for an air carrier to conduct CAT II and III approaches
can be found in OpSpecs Part C. CAT II and III operations
allow authorized pilots to make instrument approaches in
weather that would otherwise be prohibitive.
While CAT I ILS operations permit substitution of midfield
RVR for TDZ RVR (when TDZ RVR is not available), CAT II ILS
operations do not permit any substitutions for TDZ RVR.
The TDZ RVR system is required and must be used. The TDZ
RVR is controlling for all CAT II ILS operations.
The weather conditions encountered in CAT III operations
range from an area where visual references are adequate for
manual rollout in CAT IIIa, to an area where visual references
are inadequate even for taxi operations in CAT IIIc. To
date, no U.S. operator has received approval for CAT IIIc
in OpSpecs. Depending on the auto-flight systems, some
aircraft require a DH to ensure that the aircraft is going to
land in the TDZ and some require an Alert Height as a final
cross-check of the performance of the auto-flight systems.
These heights are based on radio altitude (RA) and can be
found in the specific aircraft’s AFM. [Figure 4-42]
Both CAT II and III approaches require special ground and
airborne equipment to be installed and operational, as
well as special aircrew training and authorization. The
OpSpecs of individual air carriers detail the requirements
of these types of approaches, as well as their performance
criteria. Lists of locations where each operator is approved
to conduct CAT II and III approaches can also be found in
the OpSpecs.
Special Authorization approaches are designed to
take advantage of advances in flight deck avionics and
technologies like Head-Up Displays (HUD) and automatic
landings. There are extensive ground infrastructures and
lighting requirements for standard CAT II/III, and the
Special Authorization approaches mitigate the lack of some
lighting with the modern avionics found in many aircraft
today. Similar to standard CAT II/III, an air carrier must be
specifically authorized to conduct Special Authorization
CAT I/II in OpSpecs Part C.
Simultaneous Approaches To Parallel Runways
Airports that have two or more parallel runways may be
authorized to use simultaneous parallel approaches to
maximize the capacity of the airport. Depending on the
runway centerline separation and ATC procedures, there are
three classifications of simultaneous parallel approaches:
Simultaneous dependent approaches, simultaneous
independent approaches and simultaneous independent
close parallel approaches. A simultaneous dependent
approach differs from a simultaneous independent
approach in that the minimum distance between parallel
runway centerlines may be less. A staggered separation of
aircraft on the adjacent final approach course is required;
but there is no requirement for a No Transgression Zone
(NTZ) or Final Monitor Controllers. An independent
approach eliminates the need for staggered approaches
and aircraft may be side by side or pass if speeds are
different.
NOTE:
1. Simultaneous approaches involving an RNAV approach
may only be conducted when (GPS) appears in the
approach title or a chart note states that GPS is required.
See the “ILS Approaches” paragraph above for information
about pilot responsibilities when simultaneous approaches
are in use.
2. Flight Director or Autopilot requirements for simultaneous
operations will be annotated on the approach chart.
3. Simultaneous approaches may only be conducted
where instrument approach charts specifically authorize
simultaneous approaches.
Simultaneous Dependent Approaches [Figure
4-46]
When simultaneous dependent approaches are provided,
ATC applies specific minimum diagonal separation criteria,
depending on the runway separation, between aircraft on
adjacent final approach courses. Aircraft will be staggered
by a minimum of 1 NM diagonally on final, depending
on the distance between runway centerlines. Greater
separation standards are applied when the distance
between runway centerlines is greater. [Figure 4-43]
At some airports, simultaneous dependent instrument
approaches can be conducted with runways spaced less
than 2,500 feet with specific centerline separations and
threshold staggers. ATC is permitted to apply reduced
diagonal separation and special wake turbulence
procedures. The lead aircraft of the dependent pair is
restricted to being small or large aircraft weight type and is
cleared to the lower approach. The design of the approach,
aircraft weight type, and lateral separation between the two
approaches provide necessary wake turbulence avoidance
for this type of operation. An example of approach design
to help avoid wake turbulence is that some locations use
different glide slope angles on adjacent approaches; also,
if applicable, staggered thresholds help. An ATIS example
is: “Simultaneous ILS Runway 28 Left and ILS Runway 28
Right in use. ” For further information, see FAA Orders JO
7110.65 and JO 7110.308.
Where a simultaneous approach operation is approved,
sometimes each approach chart indicates the other
runway(s) with which simultaneous approaches can be
conducted. For example, “Simultaneous approaches
authorized with runway 12L ” . As procedures are revised,
the chart note will be modified to indicate “Simultaneous
approach authorized” but will not list the other runways or
approach types as that detailed information will normally
be transmitted in the ATIS or by ATC. For example, pilots
flying into Sacramento, California, may encounter parallel
approach procedures. [Figure 4-44] When there is no
chart note stating, “Simultaneous approaches authorized” ,
standard separation is used between aircraft on parallel
approaches.
Simultaneous Independent Approaches
Dual and triple simultaneous independent parallel
instrument approaches, are authorized at certain airports
with specified distances between parallel runway centerlines.
As a part of the simultaneous independent approach
approval, an NTZ must be established to ensure proper flight
track boundaries for all aircraft. Outside of the NTZ, normal
operating zones (NOZ) indicate the operating zone within
which aircraft remain during normal approach operations.
The NOZ between the final approach courses varies in
width depending on the runway centerline spacing. The
NTZ is defined as a 2,000-foot wide area located equidistant
between the final approach courses in which flight is not
allowed during the simultaneous operation. [Figure 4-46]
Any time an aircraft breaches or is anticipated to breach the
NTZ, ATC issues instructions for the threatened aircraft on the
adjacent final approach course to break off the approach to
avoid potential conflict.
A local controller for each runway is also required. Dedicated
final monitor controllers for each runway monitor separation,
track aircraft positions and issue instructions to pilots of
aircraft observed deviating from the final approach course.
[Figure 4-45] These operations are normally authorized
for ILS, LDA and RNAV approach procedures with vertical
guidance. For simultaneous parallel ILS approach operations,
pilots should review the chart notes to determine whether
the non-precision LOC procedure is authorized (in the
event of glide slope equipment failure either in the aircraft
or the ground). An example of a restriction on the use of a
LOC procedure is shown in the notes on Figure 4-24: “LOC
procedure NA during simultaneous operations” . Likewise, for
RNAV (GPS) approaches, use of LNAV procedures are often
restricted during simultaneous operations.
Triple simultaneous independent approaches are authorized
provided the runway centerlines are separated by at least
3900 feet for triple straight in approaches. If one or both
outside runways have an offset approach course of 2.5°
to 3.0°, the spacing between those outer runways and the
center runway may be reduced to 3000 feet.
Simultaneous Close Parallel Precision Runway
Monitor (PRM) Approaches
Simultaneous close parallel (independent) PRM approaches
are authorized for use at designated airports that have
parallel runways spaced less than 4,300 feet apart.
[Figure 4-47] Certain PRM approaches are referred to as
Simultaneous Offset Instrument Approaches (SOIA) and
are discussed in depth later in this chapter.
PRM procedures are the most efficient method of increasing
approach capacity at airports with closely spaced, parallel
runways. Use of PRM procedures increases airport
capacity during periods of low visibility by providing
ATC the capability to monitor simultaneous close parallel
(independent) approaches. These PRM operations reduce
delays and increase fuel savings. Traditionally the PRM
system included a high-update rate radar, a high resolution
ATC radar display, as well as software that can autonomously
track aircraft in close to real time, with visual and aural alerts
that depict the aircraft’s current position and velocity as
well as displaying a ten-second projected position to the
controllers. Today, most PRM operations are conducted
without the need for high update rate radar, so long as all
of the other requirements to conduct such approaches
are met.
There are also special communications and ATC
requirements for PRM approaches. PRM approaches
require a final NTZ monitor controller for each runway, a
separate tower controller for each runway, a PRM tower
frequency, and a runway-specific PRM frequency. Each final
monitor controller will have a dedicated PRM frequency,
and the tower controller will have a separate common PRM
frequency. Pilots transmit and receive on the common
tower PRM frequency, but maintain listening watch on the
final controller’s PRM frequency for their specified runway.
The final monitor controller has override capability on
their PRM frequency. In that way, if the common tower
frequency is blocked, the monitor controller’s instructions
will be heard by the pilot on the monitor controller’s PRM
frequency. Pilot training is prescribed and required for
pilots prior to using the PRM procedures. The FAA PRM
website (http://www.faa.gov/training_testing/ training/
prm/) contains training information for PRM approaches
and hosts PRM training materials for download or viewing
online. ”
When pilots or flight crews wish to decline a PRM approach,
ATC must be notified immediately and the flight will be
transitioned into the area at the convenience of ATC. Pilots
who are unable to accept a PRM approach may be subject
to delays.
The approach chart for the PRM approach requires review of
the accompanying AAUP page, which outlines pilot, aircraft,
and procedure requirements necessary to participate in
PRM operations. [Figure 4-48] Pilots need to be aware
of the differences associated with this type of approach.
Differences, as compared to other simultaneous approaches,
are listed below:
• Immediately follow break out instructions as soon
as safety permits.
• Use of the AAUP .
• Use of dual VHF communications.
• Completion of required PRM training.
• Handflying any breakout instruction. It is important
to note that descending breakouts, though rare, may
be issued. Flight crews will never be issued breakout
instructions that clear them to an altitude below the
MVA, and they are not required to descend at more
than 1,000 fpm.
• Traffic Alert and Collision Avoidance System (TCAS) is
not required to conduct a PRM approach. For aircraft
so equipped, if the controller’s climb/descend
instruction differs from the TCAS resolution advisory
(RA), pilots must follow the RA while continuing to
follow the controller’s turn instruction. Report this
deviation to ATC as soon as practical.
Simultaneous Offset Instrument Approaches
(SOIAs)
SOIAs allow simultaneous approaches to two parallel
runways spaced at least 750 feet apart, but less than 3,000
feet. Traditionally, the SOIA procedure has used an ILS/
PRM approach to one runway and an offset localizer-type
directional aid (LDA)/PRM approach with glideslope to
the adjacent runway. Now, RNAV (GPS) and RNAV (RNP)
approaches may also be used for SOIA. ” Approach charts
will include procedural notes, such as “Simultaneous Close
Parallel approach authorized with LDA PRM RWY 28R and
RNAV (GPS) PRM X RWY 28R. ” or “Simultaneous approach
authorized” . San Francisco had the first published SOIA
approach. [Figure 4-49]
The training, procedures, and system requirements for
SOIA ILS/PRM and LDA/PRM approaches are identical
with those used for simultaneous close parallel ILS/PRM
approaches until near the LDA/PRM approach MAP , where
visual acquisition of the ILS aircraft by the LDA aircraft must
be accomplished. If visual acquisition is not accomplished
prior to reaching the LDA MAP , a missed approach must
be executed. A visual segment for the LDA/PRM approach
is established between the LDA MAP and the runway
threshold. Aircraft transition in visual conditions from
the LDA course, beginning at the LDA MAP , to align with
the runway and can be stabilized by 500 feet AGL on the
extended runway centerline. Pilots are reminded that they
are responsible for collision avoidance and wake turbulence
mitigation between the LDA MAP and the runway.
The FAA website has additional information about PRM and
SOIA approaches, including an instructional PowerPoint
training presentation at http://www.faa.gov/training_
testing/training/prm/.
Converging ILS Approaches
Another method by which ILS approach capacity can be
increased is through the use of converging approaches.
Converging approaches may be established at airports
that have runways with an angle between 15° and 100°
and each runway must have an ILS. Additionally, separate
procedures must be established for each approach, and
each approach must have a MAP at least 3 NM apart with
no overlapping of the protected missed approach airspace.
Only straight-in approaches are approved for converging
ILS procedures. If the runways intersect, the controller must
be able to visually separate intersecting runway traffic.
Approaches to intersecting runways generally have higher
minimums, commonly with 600-foot ceiling and 1 1/4 to 2
mile visibility requirements. Pilots are informed of the use
of converging ILS approaches by the controller upon initial
contact or through ATIS. [Figure 4-50]
Dallas/Fort Worth International airport is one of the few
airports that makes use of converging ILS approaches
because its runway configuration has multiple parallel
runways and two offset runways. [Figure 4-51] The
approach chart title indicates the use of converging
approaches and the notes section highlights other runways
that are authorized for converging approach procedures.
Note the slight different in charting titles on the IAPs. Soon
all Converging ILS procedures will be charted in the newer
format shown in Figure 4-50, with the use of "V" in the title,
and "CONVERGING" in parenthesis.
VOR Approach
The VOR is one of the most widely used non-precision
approach types in the NAS. VOR approaches use VOR
facilities both on and off the airport to establish approaches
and include the use of a wide variety of equipment, such
as DME and TACAN. Due to the wide variety of options
included in a VOR approach, TERPS outlines design criteria
for both on and off airport VOR facilities, as well as VOR
approaches with and without a FAF. Despite the various
configurations, all VOR approaches are non-precision
approaches, require the presence of properly operating
VOR equipment, and can provide MDAs as low as 250 feet
above the runway. VOR also offers a flexible advantage in
that an approach can be made toward or away from the
navigational facility.
The VOR approach into Fort Rucker, Alabama, is an example
of a VOR approach where the VOR facility is on the airport
and there is no specified FAF. [Figure 4-52] For a straight-in
Figure 4-38. Traditional GPS approach overlay.
Figure 4-39. Lincoln Muni KLNK Lincoln, Nebraska, RNAV GPS RWY 14 approach.
approach, the final approach course is typically aligned
to intersect the extended runway centerline 3,000 feet
from the runway threshold, and the angle of convergence
between the two does not exceed 30°. This type of VOR
approach also includes a minimum of 300 feet of obstacle
clearance in the final approach area. The final approach
area criteria include a 2 NM wide primary area at the facility
that expands to 6 NM wide at a distance of 10 NM from
the facility. Additional approach criteria are established
for courses that require a high altitude teardrop approach
penetration.
When DME is included in the title of the VOR approach,
operable DME must be installed in the aircraft in order to
fly the approach from the FAF. The use of DME allows for an
accurate determination of position without timing, which
greatly increases situational awareness throughout the
approach. Alexandria, Louisiana, is an excellent example
of a VOR/DME approach in which the VOR is off the airport
and a FAF is depicted. [Figure 4-53] In this case, the final
approach course is a radial or straight-in final approach and
is designed to intersect the runway centerline at the runway
threshold with the angle of convergence not exceeding 30°.
The criteria for an arc final approach segment associated
with a VOR/DME approach is based on the arc being
beyond 7 NM and no farther than 30 NM from the VOR
and depends on the angle of convergence between the
runway centerline and the tangent of the arc. Obstacle
clearance in the primary area, which is considered the area
4 NM on either side of the arc centerline, is guaranteed by
at least 500 feet.
NDB Approach
Like the VOR approach, an NDB approach can be designed
using facilities both on and off the airport, with or without
a FAF, and with or without DME availability. At one time,
it was commonplace for an instrument student to learn
how to fly an NDB approach, but with the growing use of
GPS, many pilots no longer use the NDB for instrument
approaches. New RNAV approaches are also rapidly being
constructed into airports that are served only by NDB. The
long-term plan includes the gradual phase out of NDB
facilities, and eventually, the NDB approach becomes
nonexistent. Until that time, the NDB provides additional
availability for instrument pilots into many smaller, remotely
located airports.
The NDB Runway 35 approach at Carthage/Panola County
Sharpe Field is an example of an NDB approach established
with an on-airport NDB that does not incorporate a FAF.
[Figure 4-54] In this case, a procedure turn or penetration
turn is required to be a part of the approach design. For
the NDB to be considered an on-airport facility, the facility
must be located within one mile of any portion of the
landing runway for straight-in approaches and within one
mile of any portion of usable landing surface for circling
approaches. The final approach segment of the approach
is designed with a final approach area that is 2.5 NM wide
at the facility and increases to 8 NM wide at 10 NM from
the facility. Additionally, the final approach course and
the extended runway centerline angle of convergence
cannot exceed 30° for straight-in approaches. This type of
NDB approach is afforded a minimum of 350 feet obstacle
clearance.
When a FAF is established for an NDB approach, the
approach design criteria changes. It also takes into account
whether or not the NDB is located on or off the airport.
Additionally, this type of approach can be made both
moving toward or away from the NDB facility. The Tuscon
Ryan Field, NDB/DME RWY 6 is an approach with a FAF
using an on-airport NDB facility that also incorporates the
use of DME. [Figure 4-55] In this case, the NDB has DME
capabilities from the LOC approach system installed on the
airport. While the alignment criteria and obstacle clearance
remain the same as an NDB approach without a FAF, the
final approach segment area criteria changes to an area that
is 2.5 NM wide at the facility and increases to 5 NM wide,
15 NM from the NDB.
Radar Approaches
The two types of radar approaches available to pilots when
operating in the NAS are precision approach radar (PAR) and
airport surveillance radar (ASR). Radar approaches may be
given to any aircraft at the pilot’s request. ATC may also offer
radar approach options to aircraft in distress regardless of
the weather conditions or as necessary to expedite traffic.
Despite the control exercised by ATC in a radar approach
environment, it remains the pilot’s responsibility to ensure
the approach and landing minimums listed for the approach
are appropriate for the existing weather conditions
considering personal approach criteria certification and
company OpSpecs.
Perhaps the greatest benefit of either type of radar approach
is the ability to use radar to execute a no gyro approach.
Assuming standard rate turns, ATC can indicate when to
begin and end turns. If available, pilots should make use of
this approach when the heading indicator has failed and
partial panel instrument flying is required.
Information about radar approaches is published in tabular
form in the front of the TPP booklet. PAR, ASR, and circling
approach information including runway, DA, DH, or MDA,
height above airport (HAA), HAT, ceiling, and visibility criteria
Figure 4-40. ILS final approach segment design criteria.
CAT II
0 150 700
Runway visual range (feet)
1,200 1,800 2,400
Decision height (feet AGL)CAT IIIc
CAT IIIb CAT IIIa
CAT I
The lowest authorized ILS minimums, with all required ground and airborne systems components operative, are:
CAT I - decision height (DH) 200 feet and runway visual range
(RVR) 2,400 feet (with touchdown zone and centerline lighting.
RVR 1,800 feet).
CAT II - DH 100 feet and RVR 1,200 feet.
CAT IIIa - No DH or DH below 100 feet and RVR not less than
700 feet.
CAT IIIb - No DH or DH below 50 feet and RVR less than
700 feet but not less than 150 feet.
CAT IIIc - No DH and no RVR limitation.
NOTE: Special authorization and equipment are required
for CAT II and III.
Figure 4-41. ILS approach categories.