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airplane, or by a stall warning device that will give a
clear distinguishable indication of the stall. Most
airplanes are equipped with a stall warning device.
The factors that affect the stalling characteristics of the
airplane are balance, bank, pitch attitude, coordination,
drag, and power. The pilot should learn the effect of the
stall characteristics of the airplane being flown and the
proper correction. It should be reemphasized that a stall
can occur at any airspeed, in any attitude, or at any
power setting, depending on the total number of factors
affecting the particular airplane.
A number of factors may be induced as the result of
other factors. For example, when the airplane is in a
nose-high turning attitude, the angle of bank has a
tendency to increase. This occurs because with the
airspeed decreasing, the airplane begins flying in a
smaller and smaller arc. Since the outer wing is
moving in a larger radius and traveling faster than the
inner wing, it has more lift and causes an overbanking
tendency. At the same time, because of the decreasing
airspeed and lift on both wings, the pitch attitude tends
to lower. In addition, since the airspeed is decreasing
while the power setting remains constant, the effect of
torque becomes more prominent, causing the airplane
to yaw.
During the practice of power-on turning stalls, to
compensate for these factors and to maintain a
constant flight attitude until the stall occurs, aileron
pressure must be continually adjusted to keep the bank
attitude constant. At the same time, back-elevator
pressure must be continually increased to maintain the
pitch attitude, as well as right rudder pressure
increased to keep the ball centered and to prevent
adverse yaw from changing the turn rate. If the bank is
allowed to become too steep, the vertical component
of lift decreases and makes it even more difficult to
maintain a constant pitch attitude.
Whenever practicing turning stalls, a constant pitch
and bank attitude should be maintained until the stall
occurs. Whatever control pressures are necessary
should be applied even though the controls appear to
be crossed (aileron pressure in one direction, rudder
pressure in the opposite direction). During the entry to
a power-on turning stall to the right, in particular, the
controls will be crossed to some extent. This is due to
right rudder pressure being used to overcome torque
and left aileron pressure being used to prevent the
bank from increasing.
APPROACHES TO STALLS (IMMINENT
STALLS)—POWER-ON OR POWER-OFF
An imminent stall is one in which the airplane is
approaching a stall but is not allowed to completely
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stall. This stall maneuver is primarily for practice in
retaining (or regaining) full control of the airplane
immediately upon recognizing that it is almost in a stall
or that a stall is likely to occur if timely preventive
action is not taken.
The practice of these stalls is of particular value in
developing the pilot’s sense of feel for executing
maneuvers in which maximum airplane performance
is required. These maneuvers require flight with the
airplane approaching a stall, and recovery initiated
before a stall occurs. As in all maneuvers that involve
significant changes in altitude or direction, the pilot
must ensure that the area is clear of other air traffic
before executing the maneuver.
These stalls may be entered and performed in the
attitudes and with the same configuration of the basic
full stalls or other maneuvers described in this chapter.
However, instead of allowing a complete stall, when
the first buffeting or decay of control effectiveness is
noted, the angle of attack must be reduced immediately
by releasing the back-elevator pressure and applying
whatever additional power is necessary. Since the
airplane will not be completely stalled, the pitch
attitude needs to be decreased only to a point where
minimum controllable airspeed is attained or until
adequate control effectiveness is regained.
The pilot must promptly recognize the indication of a
stall and take timely, positive control action to prevent
a full stall. Performance is unsatisfactory if a full stall
occurs, if an excessively low pitch attitude is attained,
or if the pilot fails to take timely action to avoid
excessive airspeed, excessive loss of altitude, or a spin.
FULL STALLS POWER-OFF
The practice of power-off stalls is usually performed
with normal landing approach conditions in simulation
of an accidental stall occurring during landing
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(43)
