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vectoring required in the terminal area. When operating
a reciprocating engine or turboprop airplane within 20
NM from your destination airport, 150 knots is usually
the slowest airspeed you will be assigned. If your aircraft cannot maintain the assigned airspeed, you must
advise ATC. Controllers may ask you to maintain the
same speed as the aircraft ahead of or behind you on the
approach. You are expected to maintain the specified airspeed ±10 knots. At other times, ATC may ask you to
increase or decrease your speed by 10 knots, or multiples thereof. When the speed adjustment is no longer
needed, ATC will advise you to “…resume normal
speed.” Keep in mind that the maximum speeds specified in Title 14 of the Code of Federal Regulations (14
CFR) Part 91.117 still apply during speed adjustments.
It is your responsibility, as pilot in command, to advise
ATC if an assigned speed adjustment would cause you
to exceed these limits. For operations in Class C or D
airspace at or below 2,500 feet above ground level
(AGL), within 4 NM of the primary airport, ATC has the
authority to request or approve a faster speed than those
prescribed in Part 91.117.
Pilots operating at or above 10,000 feet MSL on an
assigned speed adjustment that is greater than 250 KIAS
are expected to reduce speed to 250 KIAS to comply
with Part 91.117(a) when cleared below 10,000 feet
MSL, within domestic airspace. This speed adjustment
is made without notifying ATC. Pilots are expected to
comply with the other provisions of Part 91.117 without
notifying ATC. For example, it is normal for faster aircraft to level off at 10,000 feet MSL while slowing to the
250 KIAS limit that applies below that altitude, and to
level off at 2,500 feet above airport elevation to slow to
the 200 KIAS limit that applies within the surface limits
of Class C or D airspace. Controllers anticipate this
action and plan accordingly.
Speed restrictions of 250 knots do not apply to aircraft operating beyond 12 NM from the coastline
within the United States (U.S.) Flight Information
Region, in offshore Class E airspace below 10,000
feet MSL. In airspace underlying a Class B airspace
area designated for an airport, pilots are expected to
comply with the 200 KIAS limit specified in Part
91.117(c). (See Parts 91.117(c) and 91.703.)
Approach clearances cancel any previously assigned
speed adjustment. Pilots are expected to make speed
adjustments to complete the approach unless the
adjustments are restated. Pilots complying with speed
adjustment instructions should maintain a speed within
plus or minus 10 knots or 0.02 Mach number of the
specified speed.
Although standardization of these procedures for terminal locations is subject to local considerations, specific
criteria apply in developing new or revised arrival procedures. Normally, high performance airplanes enter
the terminal area at or above 10,000 feet above the airport elevation and begin their descent 30 to 40 NM
from touchdown on the landing runway. Unless pilots
indicate an operational need for a lower altitude,
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).”
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Instrument Procedures Handbook (IPH)仪表程序手册上(94)
