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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 above ground level
(AGL) on the extended runway centerline.
The FAA website has additional information about
PRM and SOIA, including instructional videos at:
http://www.faa.gov/education_research/training/prm/
CONVERGING
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 degrees 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 straightin 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 also have higher
minimums with a 700-foot minimum and no less than 2
SM visibility. Pilots are informed of the use of converging ILS approaches by the controller upon initial contact or through ATIS. [Figure 5-47 on page 5-58]
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 5-48 on page
5-58] The approach chart title indicates the use of con-
verging approaches and the notes section highlights
other runways that are authorized for converging
approach procedures.
MICROWAVE LANDING SYSTEM
The MLS is a precision instrument approach alternative to the ILS. It provides azimuth, elevation, and distance information, as well as a back azimuth capable of
providing guidance for missed approach procedures
and departures. In addition to straight-in approaches,
the MLS system can also provide three-dimensional
RNAV type approaches in both computed straight and
curved paths. It was initially designed to replace the
ILS system and it provided inherent flexibility and
broader reception range with the greatest limitation
being the capabilities of the airborne equipment
installed in individual aircraft.
The MLS has multiple advantages including an
increased number of frequencies, compact ground
equipment, and complex approach paths. For a variety
of reasons, particularly the advent of civil use GPS,
MLS installation was deferred, and by 1994 it was officially cancelled by the FAA. Today there are few MLS
installations in the U.S. and currently there are no plans
for further installations. Futhermore, the MLS
equipment required for an MLS approach was not
widely installed in aircraft, whereas most new
aircraft produced today come with GPS systems.
With the limited number of MLS installations
around the country, it is highly unlikely that most
pilots will ever encounter the MLS approach, and
if they do, it is even less likely that the proper
equipment would be installed in the aircraft.
Like the ILS, the basic MLS approach requires the
final approach course alignment to be within 3
degrees of the extended runway centerline. This type
of approach uses a glide slope between 3 and 6.40
degrees and provides precision landing minimums to
200 feet HAT. Obstacle clearance is based on the glide
slope angle used in the approach design. The design
criteria differ for each type of MLS approach and
incorporate numerous formulas for the derivation of
specific course criteria. This information is contained
in FAA Order 8260.3 Volume 3, Chapters 2 and 3.
In the front of the TPP, there is a page containing additional information pertaining to the use of an MLS system. The MLS Channeling and Frequency Pairing
Table cross references the appropriate MLS channel
with its paired VHF and TACAN frequencies. Ground
equipment associated with the MLS operates on the
MLS channels, while the MLS angle/data and DME is
required to operate using one of the paired VHF or
TACAN frequencies.
5-57
Figure 5-46. Simultaneous Offset Instrument Approach Procedure.
5-58
15° to
100°
Figure 5-47. Converging Approach Criteria.
Figure 5-48. Dallas/Fort Worth (KDFW), Dallas/Fort Worth, Texas, CONVERGING ILS RWY 35C.
5-59
VOR APPROACH
The VOR is one of the most widely used nonprecision
approach types in the NAS. VOR approaches use VOR
facilities both on and off the airport to establish
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Instrument Procedures Handbook (IPH)仪表程序手册上(139)
