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t Figure 4-2. Typical Air Carrier Descent Planning Chart
4-3
climb and cruise phases of flight, you should consult the
proper performance charts to compute your fuel requirements as well as the time and distance needed for your
descent. Figure 4-3 is an example of a descent-planning
chart. If you are descending from 17,000 feet to a final
(approach gate) altitude of 5,650, your time to descend
is 11 minutes and distance to descend is 40 NM.
During the cruise and descent phases of flight, you need
to monitor and manage the airplane according to the
appropriate manufacturer’s recommendations. The
flight manuals and operating handbooks contain cruise
and descent checklists, performance charts for specific
cruise configurations, and descent charts that provide
information regarding the fuel, time, and distance
required to descend. Review this information prior to
the departure of every flight so you have an understanding of how your airplane is supposed to perform at cruise
and during descent. A stabilized descent constitutes a
pre-planned maneuver in which the power is properly
set, and minimum control input is required to maintain
the appropriate descent path. Excessive corrections or
control inputs indicate the descent was improperly
planned. Plan your IFR descent from cruising altitude so
you arrive at the approach gate altitude or initial
approach fix altitude prior to beginning the instrument
approach. [Figure 4-4 on page 4-4]
Descending from cruise altitude and entering the
approach environment can be a busy time during the
flight. You are talking on the radio, changing radio frequencies, pulling out different charts, adjusting controls,
Figure 4-3. Descent Planning Chart.
Altitude Loss
Required
Approach Gate
Altitude
Determine the required altitude loss
by subtracting the approach gate
altitude from the cruise altitude.
Calculate the descent time by
dividing the total altitude loss by the
descent rate. This provides you with
the total time in minutes that it will
take to descend.
Using a flight computer, determine
the distance required for descent by
finding the distance traveled in the
total time found using the known
groundspeed. The resulting figure is
the distance from the destination
airport approach gate at which you
need to begin your descent.
4-4
reading checklists, all of which can be distracting. By
planning your descent in advance, you reduce the workload required during this phase of flight, which is smart
workload management. Pilots often stay as high as they
can as long as they can, so planning the descent prior to
arriving at the approach gate is necessary to achieve a
stabilized descent, and increases situational awareness.
Using the information given, calculate the distance
needed to descend to the approach gate.
• Cruise Altitude: 17,000 feet MSL
• Approach Gate Altitude: 2,100 feet MSL
• Descent Rate: 1,500 feet per minute
• Descent Groundspeed: 155 knots
Subtract 2,100 feet from 17,000 feet, which equals
14,900 feet. Divide this number by 1,500 feet per
minute, which equals 9.9 minutes, round this off to 10
minutes. Using your flight computer, find the distance
required for the descent by using the time of 10 minutes
and the groundspeed of 155 knots. This gives you a distance of 25.8 NM. You need to begin your descent
approximately 26 NM prior to arriving at your destination airport approach gate.
CRUISE CLEARANCE
The term "cruise" may be used instead of "maintain" to
assign a block of airspace to an aircraft. The block
extends from the minimum IFR altitude up to and
including the altitude that is specified in the cruise
clearance. On a cruise clearance, you may level off at
any intermediate altitude within this block of airspace.
You are allowed to climb or descend within the block at
your own discretion. However, once you start descent
and verbally report leaving an altitude in the block to
ATC, you may not return to that altitude without an
additional ATC clearance. A cruise clearance also
authorizes you to execute an approach at the destination
airport. When operating in uncontrolled airspace on a
cruise clearance, you are responsible for determining
the minimum IFR altitude. In addition, your descent
and landing at an airport in uncontrolled airspace are
governed by the applicable visual flight rules (VFR)
and/or Operations Specifications (OpsSpecs), i.e., CFR,
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Instrument Procedures Handbook (IPH)仪表程序手册上(89)
