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RNAV aircraft being vectored for a GPS or RNAV
approach:
• When the reported ceiling is at least 500 feet
above the MVA/MIA and the visibility is at least
3 SM (may be a pilot report [PIREP] if no
weather is reported for the airport), aircraft may
be vectored to intercept the final approach course
closer than 2 NM outside the approach gate but
no closer than the approach gate.
• If specifically requested by the pilot, aircraft
may be vectored to intercept the final
approach course inside the approach gate but
no closer than the FAF.
NONRADAR ENVIRONMENT
In the absence of radar vectors, an instrument
approach begins at an IAF. An aircraft that has been
cleared to a holding fix that, prior to reaching that
fix, is issued a clearance for an approach, but not
issued a revised routing, such as, “proceed direct
to…” is expected to proceed via the last assigned
route, a feeder route if one is published on the
approach chart, and then to commence the approach
as published. If, by following the route of flight to
the holding fix, the aircraft would overfly an IAF or
the fix associated with the beginning of a feeder
route to be used, the aircraft is expected to commence the approach using the published feeder route
to the IAF or from the IAF as appropriate. The aircraft would not be expected to overfly and return to
the IAF or feeder route.
For aircraft operating on unpublished routes, an
altitude is assigned to maintain until the aircraft is
established on a segment of a published route or
IAP. (Example: “maintain 2,000 until established
on the final approach course outbound, cleared
VOR/DME runway 12.”) The International Civil
Aviation Organization (ICAO) definition of established on course requires the aircraft to be within
half scale deflection for the ILS and VOR, or
within ±5° of the required bearing for the NDB.
Generally, the controller assigns an altitude compatible with glide slope intercept prior to being cleared
for the approach.
TYPES OF APPROACHES
In the NAS, there are approximately 1,033 VOR stations, 1,200 NDB stations, and 1,370 ILS installations,
including 25 LOC-Type Directional Aids (LDAs), 23
Simplified Directional Facilities (SDFs), and 242 LOC
only facilities. As time progresses, it is the intent of the
FAA to reduce navigational dependence on VOR,
NDB, and other ground-based NAVAIDs and, instead,
to increase the use of satellite-based navigation.
To expedite the use of RNAV procedures for all instrument pilots, the FAA has begun an aggressive schedule
to develop RNAV procedures. During 2002, the number
of RNAV/GPS approaches published in the NAS
exceeded 3,300, with additional procedures published
every revision cycle. While it had originally been the
plan of the FAA to begin decommissioning VORs,
NDBs, and other ground-based NAVAIDs, the overall
strategy has been changed to incorporate a majority
dependence on augmented satellite navigation while
maintaining a satisfactory backup system. This
backup system will include retaining all CAT II and
III ILS facilities and close to one-half of the existing
VOR network.
Each approach is provided obstacle clearance based on
the Order 8260.3 TERPS design criteria as appropriate
for the surrounding terrain, obstacles, and NAVAID
availability. Final approach obstacle clearance is different for every type of approach but is guaranteed from
the start of the final approach segment to the runway (not
below the MDA for nonprecision approaches) or MAP,
whichever occurs last within the final approach area.
Both pilots and ATC assume obstacle clearance responsibility, but it is dependent upon the pilot to maintain an
appropriate flight path within the boundaries of the final
approach area.
There are numerous types of instrument approaches
available for use in the NAS including RNAV (GPS),
ILS, MLS, LOC, VOR, NDB, SDF, and radar
approaches. Each approach has separate and individual
design criteria, equipment requirements, and system
capabilities.
VISUAL AND CONTACT APPROACHES
To expedite traffic, ATC may clear pilots for a visual
approach in lieu of the published approach procedure if
flight conditions permit. Requesting a contact
approach may be advantageous since it requires less
time than the published IAP and provides separation
from IFR and special visual flight rules (SVFR) traffic.
A contact or visual approach may be used in lieu of conducting a SIAP, and both allow the flight to continue as
an IFR flight to landing while increasing the efficiency
　
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本文鏈接地址：Instrument Procedures Handbook (IPH)儀表程序手冊下(127)