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than usual be exerted on the rudder. In the recovery from
a gliding turn, the same rudder action takes place but
without as much pressure being necessary. The actual
displacement of the rudder is approximately the same,
but it seems to be less in a glide because the resistance to
pressure is so much less due to the absence of the propeller
slipstream. This often results in a much greater
application of rudder through a greater range than is realized,
resulting in an abrupt stoppage of the turn when the
rudder is applied for recovery. This factor is particularly
important during landing practice since the student
almost invariably recovers from the last turn too soon
and may enter a cross-control condition trying to correct
the landing with the rudder alone. This results in landing
from a skid that is too easily mistaken for drift.
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There is another danger in excessive rudder use during
gliding turns. As the airplane skids, the bank will
increase. This often alarms the beginning pilot when it
occurs close to the ground, and the pilot may respond
by applying aileron pressure toward the outside of the
turn to stop the bank. At the same time, the rudder
forces the nose down and the pilot may apply back-elevator
pressure to hold it up. If allowed to progress, this
situation may result in a fully developed cross-control
condition. A stall in this situation will almost certainly
result in a spin.
The level-off from a glide must be started before
reaching the desired altitude because of the airplane’s
downward inertia. The amount of lead depends on the
rate of descent and the pilot’s control technique. With
too little lead, there will be a tendency to descend
below the selected altitude. For example, assuming a
500-foot per minute rate of descent, the altitude must
be led by 100 – 150 feet to level off at an airspeed
higher than the glide speed. At the lead point, power
should be increased to the appropriate level flight
cruise setting so the desired airspeed will be attained
at the desired altitude. The nose tends to rise as both
airspeed and downwash on the tail section increase.
The pilot must be prepared for this and smoothly control
the pitch attitude to attain level flight attitude so
that the level-off is completed at the desired altitude.
Particular attention should be paid to the action of the
airplane’s nose when recovering (and entering) gliding
turns. The nose must not be allowed to describe an arc
with relation to the horizon, and particularly it must
not be allowed to come up during recovery from turns,
which require a constant variation of the relative pressures
on the different controls.
Common errors in the performance of descents and
descending turns are:
• Failure to adequately clear the area.
• Inadequate back-elevator control during glide
entry resulting in too steep a glide.
• Failure to slow the airplane to approximate glide
speed prior to lowering pitch attitude.
• Attempting to establish/maintain a normal glide
solely by reference to flight instruments.
• Inability to sense changes in airspeed through
sound and feel.
• Inability to stabilize the glide (chasing the airspeed
indicator).
• Attempting to “stretch” the glide by applying
back-elevator pressure.
• Skidding or slipping during gliding turns due to
inadequate appreciation of the difference in rudder
action as opposed to turns with power.
• Failure to lower pitch attitude during gliding turn
entry resulting in a decrease in airspeed.
• Excessive rudder pressure during recovery from
gliding turns.
• Inadequate pitch control during recovery from
straight glides.
• “Ground shyness”—resulting in cross-controlling
during gliding turns near the ground.
• Failure to maintain constant bank angle during
gliding turns.
PITCH AND POWER
No discussion of climbs and descents would be
complete without touching on the question of what
controls altitude and what controls airspeed. The
pilot must understand the effects of both power and
elevator control, working together, during different
conditions of flight. The closest one can come to a
formula for determining airspeed/altitude control
that is valid under all circumstances is a basic principle
of attitude flying which states:
“At any pitch attitude, the amount of power used
will determine whether the airplane will climb,
descend, or remain level at that attitude.”
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AIRPLANE FLYING HANDBOOK 飞机飞行手册上(37)
