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altimeter needle will move more slowly, and the airspeed will
show acceleration. [Figure 5-29] When the altimeter, attitude
indicator, and VSI show level flight, constant changes in
pitch and torque control will have to be made as the airspeed
increases. As the airspeed approaches cruising speed, reduce
power to the cruise setting. The amount of lead depends upon
the rate of acceleration of the airplane.
To level off at climbing airspeed, lower the nose to the pitch
attitude appropriate to that airspeed in level flight. Power
is simultaneously reduced to the setting for that airspeed
as the pitch attitude is lowered. If power reduction is at a
rate proportionate to the pitch change, airspeed will remain
constant.
Descents
A descent can be made at a variety of airspeeds and attitudes
by reducing power, adding drag, and lowering the nose
to a predetermined attitude. The airspeed will eventually
stabilize at a constant value. Meanwhile, the only flight
instrument providing a positive attitude reference, is the
attitude indicator. Without the attitude indicator (such as
during a partial panel descent), the ASI, the altimeter, and
the VSI will show varying rates of change until the airplane
decelerates to a constant airspeed at a constant attitude.
During the transition, changes in control pressure and trim,
as well as cross-check and interpretation, must be accurate
to maintain positive control.
5-17
Figure 5-29. Level Off at Cruising Speed.
Entry
The following method for entering descents is effective
with or without an attitude indicator. First, reduce airspeed
to a selected descent airspeed while maintaining straightand-
level flight, then make a further reduction in power
(to a predetermined setting). As the power is adjusted,
simultaneously lower the nose to maintain constant airspeed,
and trim off control pressures.
During a constant airspeed descent, any deviation from the
desired airspeed calls for a pitch adjustment. For a constant
rate descent, the entry is the same, but the VSI is primary for
pitch control (after it stabilizes near the desired rate), and the
ASI is primary for power control. Pitch and power must be
closely coordinated when corrections are made, as they are
in climbs. [Figure 5-30]
Leveling Off
The level off from a descent must be started before reaching
the desired altitude. The amount of lead depends upon the
rate of descent and control technique. With too little lead, the
airplane will tend to overshoot the selected altitude unless
technique is rapid. Assuming a 500 fpm rate of descent, lead
the altitude by 100–150 feet for a level off at an airspeed
higher than descending speed. At the lead point, add power to
the appropriate level flight cruise setting. [Figure 5-31] Since
the nose will tend to rise as the airspeed increases, hold
forward elevator pressure to maintain the vertical speed at
the descending rate until approximately 50 feet above the
altitude, and then smoothly adjust the pitch attitude to the
level flight attitude for the airspeed selected.
To level off from a descent at descent airspeed, lead the desired
altitude by approximately 50 feet, simultaneously adjusting
the pitch attitude to level flight and adding power to a setting
that will hold the airspeed constant. [Figure 5-32] Trim off
the control pressures and continue with the normal straightand-
level flight cross-check.
Common Errors in Straight Climbs and Descents
Common errors result from the following faults:
1. Overcontrolling pitch on climb entry. Until the pitch
attitudes related to specific power settings used in
climbs and descents are known, larger than necessary
pitch adjustments are made. One of the most difficult
habits to acquire during instrument training is to
restrain the impulse to disturb a flight attitude until
the result is known. Overcome the inclination to
make a large control movement for a pitch change,
and learn to apply small control pressures smoothly,
cross-checking rapidly for the results of the change,
and continuing with the pressures as instruments show
the desired results. Small pitch changes can be easily
controlled, stopped, and corrected; large changes are
more difficult to control.
5-18
Figure 5-31. Level Off Airspeed Higher Than Descent Airspeed.
Figure 5-30. Constant Airspeed Descent, Airspeed High—Reduce Power.
5-19
Figure 5-32. Level Off at Descent Airspeed.
2. Failure to vary the rate of cross-check during speed,
power, or attitude changes or climb or descent
entries.
3. Failure to maintain a new pitch attitude. For example,
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Instrument Flying Handbook仪表飞行手册上(87)
