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waypoint.
There are circumstances when a waypoint may be
coded into the database as both a FB WP and a FO WP,
depending on how the waypoints are sequenced during
the approach procedure. For example, a waypoint that
serves as an IAF may be coded as a FB WP for the
approach and as a FO WP when it also serves as the
MAHWP for the missed approach procedure.
ALTITUDES
Prescribed altitudes may be depicted in four different
configurations: minimum, maximum, recommended,
and mandatory. The U.S. Government distributes
Figure 5-13. Fly-over and Fly-by Waypoints.
5-18
approach charts produced by the National Geospatial-
Intelligence Agency (NGA) and NACO. Altitudes are
depicted on these charts in the profile view with underscore, overscore, or both to identify them as minimum,
maximum, or mandatory, respectively.
• Minimum altitudes are depicted with the altitude
value underscored. Aircraft are required to maintain altitude at or above the depicted value.
• Maximum altitudes are depicted with the altitude
value overscored. Aircraft are required to maintain altitude at or below the depicted value.
• Mandatory altitudes are depicted with the altitude
value both underscored and overscored. Aircraft
are required to maintain altitude at the depicted
value.
• Recommended altitudes are depicted without an
underscore or overscore.
NOTE: The underscore and overscore used to
identify mandatory altitudes and overscore to
identify maximum altitudes are used almost
exclusively by the NGA for military charts.
Pilots are cautioned to adhere to altitudes as prescribed because, in certain instances, they may
be used as the basis for vertical separation of
aircraft by ATC. When a depicted altitude is
specified in the ATC clearance, that altitude
becomes mandatory as defined above.
MINIMUM SAFE ALTITUDE
Minimum safe altitudes (MSAs) are published for
emergency use on IAP charts. For conventional navigation systems, the MSA is normally based on the
primary omnidirectional facility on which the IAP is
predicated. The MSA depiction on the approach chart
contains the facility identifier of the NAVAID used to
determine the MSA. For RNAV approaches, the MSA is
based on either the runway waypoint (RWY WP) or the
missed approach waypoint (MAWP) for straight-in
approaches, or the airport waypoint (APT WP) for circling only approaches. For RNAV (GPS) approaches
with a terminal arrival area (TAA) the MSA is based on
the IAF waypoint.
MSAs are expressed in feet above MSL and normally
have a 25 NM radius. This radius may be expanded to
30 NM if necessary to encompass the airport landing
surfaces. Ideally, a single sector altitude is established
and depicted on the planview of approach charts. When
necessary to maintain clearance from obstructions, the
area may be further sectored and as many as four MSAs
established. When established, sectors may be no less
than 90°in spread. MSAs provide 1,000 feet clearance
over all obstructions but do not necessarily assure
acceptable navigation signal coverage.
FINAL APPROACH FIX ALTITUDE
Another important altitude that should be briefed
during an IAP briefing is the FAF altitude, designated
by the cross on a nonprecision approach, and the lightning bolt symbol designating the glide slope intercept
altitude on a precision approach. Adherence to and
crosscheck of this altitude can have a direct effect on
the success of an approach.
Proper airspeed, altitude, and configuration, when
crossing the FAF of a nonprecision approach, are
extremely important no matter what type of aircraft is
being flown. The stabilized approach concept, implemented by the FAA within the SOPs of each air carrier,
suggests that crossing the FAF at the published altitude
is often a critical component of a successful nonprecision approach, especially in a large turbojet
aircraft.
The glide slope intercept altitude of a precision
approach should also be included in the IAP briefing.
Awareness of this altitude when intercepting the glide
slope can ensure the flight crew that a “false glide
slope” or other erroneous indication is not inadvertently followed. Many air carriers include a standard
callout when the aircraft passes over the FAF of the
nonprecision approach underlying the ILS. The pilot
monitoring (PM) states the name of the fix and the
charted glide slope altitude, thus allowing both pilots to
crosscheck their respective altimeters and verify the
correct indications.
MINIMUM DESCENT ALTITUDE, DECISION ALTITUDE,
AND DECISION HEIGHT
　
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本文鏈接地址：Instrument Procedures Handbook (IPH)儀表程序手冊上(115)