曝光台 注意防骗
网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
instrument approach procedure. On nonprecision
approaches, these obstacles should be considered
when determining where to begin descent from the
MDA (see “Pilot Operational Considerations When
Flying Nonprecision Approaches” in this paragraph).
12.9 Vertical Descent Angle (VDA) on Nonprecision
Approaches. FAA policy is to publish VDAs
on all nonprecision approaches. Published along with
VDA is the threshold crossing height (TCH) that was
used to compute the angle. The descent angle may be
computed from either the final approach fix (FAF), or
a stepdown fix, to the runway threshold at the
published TCH. A stepdown fix is only used as the
start point when an angle computed from the FAF
would place the aircraft below the stepdown fix
altitude. The descent angle and TCH information are
charted on the profile view of the instrument
approach chart following the fix the angle was based
on. The optimum descent angle is 3.00 degrees; and
whenever possible the approach will be designed
using this angle.
12.9.1 The VDA provides the pilot with information
not previously available on nonprecision approaches.
It provides a means for the pilot to establish a
stabilized descent from the FAF or stepdown fix to the
MDA. Stabilized descent is a key factor in the
reduction of controlled flight into terrain (CFIT)
incidents. However, pilots should be aware that the
published angle is for information only − it is
strictly advisory in nature. There is no implicit
additional obstacle protection below the MDA. Pilots
must still respect the published minimum descent
altitude (MDA) unless the visual cues stated 14 CFR
Section 91.175 are present and they can visually
acquire and avoid obstacles once below the MDA.
The presence of a VDA does not guarantee obstacle
protection in the visual segment and does not change
any of the requirements for flying a nonprecision
approach.
12.9.2 Additional protection for the visual segment
below the MDA is provided if a VDP is published and
descent below the MDA is started at or after the VDP.
Protection is also provided, if a Visual Glide Slope
Indicator (VGSI); e.g., VASI or PAPI, is installed and
the aircraft remains on the VGSI glide path angle
from the MDA. In either case, a chart note will
indicate if the VDP or VGSI are not coincident with
the VDA. On RNAV approach charts, a small shaded
arrowhead shaped symbol (see the legend of the U.S.
Terminal Procedures books, page H1) from the end of
the VDA to the runway indicates that the 34:1 visual
surface is clear.
12.9.3 Pilots may use the published angle and
estimated/actual groundspeed to find a target rate of
descent from the rate of descent table published in the
back of the U.S. Terminal Procedures Publication.
This rate of descent can be flown with the Vertical
Velocity Indicator (VVI) in order to use the VDA as
an aid to flying a stabilized descent. No special
equipment is required.
12.9.4 Since one of the reasons for publishing a
circling only instrument landing procedures is that
the descent rate required exceeds the maximum
allowed for a straight in approach, circling only
procedures may have VDAs which are considerably
steeper than the standard 3 degree angle on final. In
this case, the VDA provides the crew with
information about the descent rate required to land
straight in from the FAF or step down fix to the
1314 JFUELBY 0 088
AIP ENR 1.5−35
United States of America 15 MAR 07
Federal Aviation Administration Nineteenth Edition
threshold. This is not intended to imply that landing
straight ahead is recommended, or even possible,
since the descent rate may exceed the capabilities of
many aircraft. The pilot must determine how to best
maneuver the aircraft within the circling obstacle
clearance area in order to land.
12.9.5 In rare cases the LNAV minima may have a
lower HAT than minima with a glide path due to the
location of the obstacles. This should be a clear
indication to the pilot that obstacles exist below the
MDA which the pilot must see in order to ensure
adequate clearance. In those cases, the glide path may
be treated as a VDA and used to descend to the LNAV
MDA as long as all the rules for a nonprecision
approach are applied at the MDA. However, the pilot
must keep in mind the information in this paragraph
and in paragraph 12.10.
12.10 Pilot Operational Considerations When
Flying Nonprecision Approaches. The missed
approach point (MAP) on a nonprecision approach is
not designed with any consideration to where the
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
AIP航行情报汇编2(87)
