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flow of traffic to an airport. It is authorized when the
ceiling is reported or expected to be at least 1,000 feet
AGL and the visibility is at least 3 SM. Pilots must
remain clear of the clouds at all times while conducting
a visual approach. At an airport with a control tower,
pilots may be cleared to fly a visual approach to one
runway while others are conducting VFR or IFR
approaches to another parallel, intersecting, or converging runway. Also, when radar service is provided, it is
automatically terminated when the controller advises
pilots to change to the tower or advisory frequency.
CONTACT APPROACHES
If conditions permit, pilots can request a contact
approach, which is then authorized by the controller. A
contact approach cannot be initiated by ATC. This procedure may be used instead of the published procedure
to expedite arrival, as long as the airport has a SIAP or
special instrument approach procedure (special IAPs
are approved by the FAA for individual operators, but
are not published in Part 97 for public use), the reported
ground visibility is at least 1 SM, and pilots are able to
remain clear of clouds with at least one statute mile flight
visibility throughout the approach. Some advantages of
a contact approach are that it usually requires less time
than the published instrument procedure, it allows pilots
to retain the IFR clearance, and provides separation from
IFR and SVFR traffic. On the other hand, obstruction
clearances and VFR traffic avoidance becomes the
pilot’s responsibility. Unless otherwise restricted, the
pilot may find it necessary to descend, climb, or fly a
circuitous route to the airport to maintain cloud
clearance or terrain/obstruction clearance.
The main differences between a visual approach and a
contact approach are: a pilot must request a contact
approach, while a visual approach may be assigned by
ATC or requested by the pilot; and, a contact approach
may be approved with 1 mile visibility if the flight can
remain clear of clouds, while a visual approach requires
the pilot to have the airport in sight, or a preceding aircraft to be followed, and the ceiling must be at least
1,000 feet AGL with at least 3 SM visibility.
CHARTED VISUAL FLIGHT PROCEDURES
A charted visual flight procedure (CVFP) may be
established at some airports with control towers for
environmental or noise considerations, as well as
when necessary for the safety and efficiency of air traffic operations. Designed primarily for turbojet aircraft,
CVFPs depict prominent landmarks, courses, and recommended altitudes to specific runways. When pilots
are flying the Roaring Fork Visual RWY 15 shown in
figure 5-32, mountains, rivers, and towns provide
guidance to Aspen, Colorado’s Sardy Field instead
of VORs, NDBs, and DME fixes.
Pilots must have a charted visual landmark or a preceding aircraft in sight, and weather must be at or above the
published minimums before ATC will issue a CVFP
clearance. ATC will clear pilots for a CVFP if the
reported ceiling at the airport of intended landing is at
least 500 feet above the MVA/MIA, and the visibility is
3 SM or more, unless higher minimums are published
for the particular CVFP. When accepting a clearance to
follow a preceding aircraft, pilots are responsible for
maintaining a safe approach interval and wake turbulence separation. Pilots must advise ATC if unable at any
point to continue a charted visual approach or if the pilot
loses sight of the preceding aircraft.
RNAV APPROACHES
Because of the complications with database coding,
naming conventions were changed in January 2001 to
accommodate all approaches using RNAV equipment
into one classification — RNAV. This classification
includes both ground-based and satellite dependent
systems. Eventually all approaches that use some type
of RNAV will reflect RNAV in the approach title. This
changeover is being made to reflect two shifts in
instrument approach technology. The first shift is the
use of the RNP concept outlined in Chapter 2 —
Departure Procedures, in which a single performance
standard concept is being implemented for approach
procedure design. Through the use of RNP, the underlying system of navigation may not be required, provided the aircraft can maintain the appropriate RNP
standard. The second shift is that advanced avionics
systems such as FMSs, used by most airlines, needed a
new navigation standard by which RNAV could be
fully integrated into the instrument approach system.
An FMS uses multi-sensor navigation inputs to produce a composite position. Essentially, the FMS navigation function automatically blends or selects position
　
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本文鏈接地址：Instrument Procedures Handbook (IPH)儀表程序手冊上(133)