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area augmentation system (LAAS) will be
charted separately under the GLS title as these
systems are implemented.
NOTE: On RNAV approach charts the GLS minima line has been used as a placeholder only. As
WAAS procedures are developed, LPV lines of
minima will replace the “GLS DA-NA” lines of
minima.
• LPV — APV minimums that take advantage of
WAAS to provide electronic lateral and vertical
guidance capability. The term “LPV” (localizer
performance with vertical guidance) 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 Aircraft Flight Manual that the installed
equipment supports LPV approaches. 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 50102), and the WAAS
approach identifier (W17A), indicating Runway
17R in this case, and then a letter to designate the
first in a series of procedures to that runway.
• LNAV/VNAV — APV minimums used by aircraft with RNAV equipment that provides both
Figure 5-15. VNAV Information.
5-22
lateral and vertical information in the approach
environment, including WAAS avionics approved
for LNAV/VNAV approaches, certified barometric-VNAV (Baro-VNAV) systems with an IFR
approach approved GPS, or certified Baro-VNAV
systems with an IFR approach approved WAAS
system (See RNAV APPROACH AUTHORIZA-
TION section for temperature limits on Baro-
VNAV). Many RNAV systems that have RNP 0.3
or less approach capability are specifically
approved in the Aircraft Flight Manual. 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 glidepath. Other
Figure 5-16. RNAV (GPS) Electronic Vertical Guidance Approach Minima.
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.
• LNAV — minimums provided for RNAV
systems that do not produce any VNAV
information. IFR approach approved GPS,
WAAS, or RNP 0.3 systems are required.
Because vertical guidance is not provided,
the procedure minimum altitude is published as an MDA. These minimums are
used in the same manner as conventional
nonprecision approach minimums. Other
RNAV systems require special approval.
• Circling — minimums that may be used with any
type of approach approved RNAV equipment
when publication of straight-in approach minimums is not possible.
REQUIRED NAVIGATION PERFORMANCE
The operational advantages of RNP include accuracy
and integrity monitoring, which provide more 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 will be 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,” or 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
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Instrument Procedures Handbook (IPH)仪表程序手册下(113)
