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
descent below 5,000 feet above the airport elevation is
typically limited to the descent area where final
descent and glide slope intercept can be made without
exceeding specific obstacle clearance and other related
arrival, approach, and landing criteria. Your descent
should not be interrupted by controllers just to ensure
that you cross the boundaries of the descent area at precisely 5,000 feet above the airport elevation. A typical
descent area is shown in Figure 4-11 on page 4-12.
Arrival delays typically are absorbed at a metering fix.
This fix is established on a route prior to the terminal
airspace, 10,000 feet or more above the airport elevation. The metering fix facilitates profile descents, rather
than controllers using delaying vectors or a holding pattern at low altitudes. Descent restrictions normally are
applied prior to reaching the final approach phase to
preclude relatively high descent rates close in to the
destination airport. At least 10 NM from initial descent
from 10,000 feet above the airport elevation, the controller issues an advisory that details when to expect to
commence the descent. ATC typically uses the phraseology, “Expect descent in (number) miles.” If cleared
for a visual or contact approach, ATC usually restricts
4-12
you to at least 5,000 feet above the airport elevation
until entering the descent area. Standard ATC phraseology is, “Maintain (altitude) until (specified point; e.g.,
abeam landing runway end), cleared for visual
approach or expect visual or contact approach clearance in (number of miles, minutes or specified point).”
Once the determination is made regarding the instrument approach and landing runway you will use, with its
associated descent area, ATC will not permit a change to
another navigational aid that is not aligned with the landing runway. When altitude restrictions are required for
separation purposes, ATC avoids assigning an altitude
below 5,000 above the airport elevation.
There are numerous exceptions to the high performance
airplane arrival procedures previously outlined. For
example, in a nonradar environment, the controller may
clear the flight to use an approach based on a NAVAID
other than the one aligned with the landing runway,
such as a circling approach. In this case, the descent to
a lower altitude usually is limited to the descent area
with the circle-to-land maneuver confined to the traffic
pattern. Also in a nonradar environment, contact
approaches may be approved from 5,000 above the airport elevation while the flight is within a descent area,
regardless of landing direction.
Descent areas are established for all straight-in instrument approach procedures at an airport and may be
established for runways not served by an instrument
approach procedure to accommodate visual and contact
approaches. More than one runway (descent area) may
be used simultaneously for arriving high performance
airplanes if there is an operational advantage for the pilot
or ATC, provided that the descent area serves the runway of intended landing.
CONTROLLED FLIGHT INTO TERRAIN
Inappropriate descent planning and execution during
arrivals has been a contributing factor to many fatal aircraft accidents. Since the beginning of commercial jet
operations, more than 9,000 people have died worldwide
because of controlled flight into terrain (CFIT). CFIT is
described as an event in which a normally functioning
aircraft is inadvertently flown into the ground, water, or
an obstacle. Of all CFIT accidents, 7.2 percent occurred
during the descent phase of flight.
The basic causes of CFIT accidents involve poor flight
crew situational awareness. One definition of situational
awareness is an accurate perception by pilots of the factors and conditions currently affecting the safe operation
of the aircraft and the crew. The causes of CFIT are the
flight crews’ lack of vertical position awareness or their
lack of horizontal position awareness in relation to the
ground, water, or an obstacle. More than two-thirds of
all CFIT accidents are the result of an altitude error or
lack of vertical situational awareness. CFIT accidents
most often occur during reduced visibility associated
with instrument meteorological conditions (IMC), darkness, or a combination of both.
The inability of controllers and pilots to properly communicate has been a factor in many CFIT accidents.
Heavy workloads can lead to hurried communication
and the use of abbreviated or non-standard phraseology.
The importance of good communication during the
arrival phase of flight was made evident in a report by an
air traffic controller and the flight crew of an MD-80.
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
Instrument Procedures Handbook (IPH)仪表程序手册下(90)
