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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
to the notes box of the pilot briefing portion of the
approach chart in figure 5-17.
In the United States, all RNP procedures are in the category of Special Aircraft and Aircrew Authorization
Required (SAAAR). Operators who seek to take advan-
tage of RNP approach procedures must meet the special RNP requirements outlined in FAA AC 90-101,
Approval Guidance for RNP Procedures with SAAAR.
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 nonprecision approach, RNAV approaches, or
LNAV/VNAV approaches is found in that operator’s
OpsSpecs, 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
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Instrument Procedures Handbook (IPH)仪表程序手册上(118)
