曝光台 注意防骗
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This is a stall that is most likely to occur during a
poorly planned and executed base-to-final approach
turn, and often is the result of overshooting the centerline
of the runway during that turn. Normally, the
proper action to correct for overshooting the runway is
to increase the rate of turn by using coordinated aileron
and rudder. At the relatively low altitude of a base-tofinal
approach turn, improperly trained pilots may be
apprehensive of steeping the bank to increase the rate
of turn. Rather than steeping the bank, they hold the
bank constant and attempt to increase the rate of turn
by adding more rudder pressure in an effort to align
with the runway.
The addition of rudder pressure on the inside of the turn
causes the speed of the outer wing to increase, creating
Left Aileron
Deflected Up
Right Aileron
Deflected Down
Rudder
Deflected Right
Figure 7-30. Crossed-control approach to a stall.
7-31
may be impossible prior to ground contact due to the
low altitude.
COMMON ERRORS
• Improper pitch and bank control during
straight-ahead and turning stalls.
• Rough or uncoordinated control procedures.
• Failure to recognize the first indications of a
stall.
• Failure to achieve a stall.
• Poor recognition and recovery procedures.
• Excessive altitude loss or airspeed or encountering
a secondary stall during recovery.
SPINS
Aspin may be defined as an aggravated stall that results
in what is termed “autorotation” wherein the glider follows
a downward corkscrew path. As the glider rotates
around a vertical axis, the rising wing is less stalled
than the descending wing, creating a rolling, yawing,
and pitching motion. The glider is basically being
forced downward by rolling, yawing, and pitching in a
spiral path. [Figure 7-31]
The autorotation results from an unequal angle of
attack on the glider’s wings. The rising wing has a
decreasing angle of attack, in which the relative lift
increases and the drag decreases. In effect, this wing is
less stalled. Meanwhile, the descending wing has an
increasing angle of attack, past the wing’s critical angle
of attack (stall) where the relative lift decreases and
drag increases.
A spin is caused when the glider’s wing exceeds its
critical angle of attack (stall) with a side slip or yaw
acting on the glider at, or beyond, the actual stall.
During this uncoordinated maneuver, a pilot may not
be aware that a critical angle of attack has been
exceeded until the glider yaws out of control toward
the lowering wing. If stall recovery is not initiated
immediately, the glider may enter a spin.
If this stall occurs while the glider is in a slipping or
skidding turn, this can result in a spin entry and rotation
in the direction that the rudder is being applied,
regardless of which wingtip is raised.
Many gliders have to be forced to spin and require
good judgment and technique to get the spin started.
These same gliders may be put into a spin accidentally
by mishandling the controls in turns, stalls, and flight
at minimum controllable airspeeds. This fact is additional
evidence of the necessity for the practice of stalls
until the ability to recognize and recover from them is
developed.
Often a wing drops at the beginning of a stall. When
this happens, the nose will attempt to move (yaw) in
the direction of the low wing. This is when use of the
rudder is important during a stall. The correct amount
of opposite rudder must be applied to keep the nose
from yawing toward the low wing. By maintaining
directional control and not allowing the nose to yaw
toward the low wing before stall recovery is initiated,
a spin will be averted. If the nose is allowed to yaw
during the stall, the glider will begin to skid in the
direction of the lowered wing and will enter a spin.
A glider must be stalled in order to enter a spin; therefore,
continued practice of stall recognition will help
the pilot develop a more instinctive and prompt reaction
in recognizing an approaching spin. It is essential
to learn to apply immediate corrective action any time
it is apparent the glider is approaching spin conditions.
If it is impossible to avoid a spin, the pilot should
immediately execute spin recovery procedures.
The flight instructor should demonstrate spins and spin
recovery techniques with emphasis on any special spin
Figure 7-31. Autorotation of spinning glider. procedures or techniques required for a particular
DEVELOPED PHASE
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Glider Flying Handbook(79)
