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occur after a recovery from a preceding stall. It is
caused by attempting to hasten the completion of a stall
recovery before the glider has regained sufficient flying
speed and the critical angle of attack is again
exceeded. When this stall occurs, the back-elevator
pressure should again be released just as in a normal
stall recovery. When sufficient airspeed has been
regained, the glider can then be returned to wings-level,
straight flight. This stall usually occurs when the pilot
uses abrupt control input to return to wings-level,
straight flight after a stall or spin recovery.
ACCELERATED STALLS
Though the stalls already discussed normally occur at a
specific airspeed, the pilot must thoroughly understand
that all stalls result solely from attempts to fly at excessively
high angles of attack. During flight, the angle of
attack of a glider wing is determined by a number of
factors, the most important of which are the airspeed,
the gross weight of the glider, and the load factors
imposed by maneuvering.
At gross weight, the glider will consistently stall at the
same indicated airspeed if no acceleration is involved.
The glider will, however, stall at a higher indicated airspeed
when excessive maneuvering loads are imposed
by steep turns, pull-ups, or other abrupt changes in its
flight path. Stalls entered from such flight situations
are called “accelerated maneuver stalls,” a term that
has no reference to the airspeeds involved.
Stalls that result from abrupt maneuvers tend to be
more rapid or severe than the unaccelerated stalls, and
because they occur at higher-than-normal airspeeds,
they may be unexpected by pilots. Failure to take
immediate steps toward recovery when an accelerated
stall occurs may result in a complete loss of flight
control, possibly causing a spin.
Accelerated maneuver stalls should not be performed
in any glider in which the maneuver is prohibited in the
GFM/POH. If they are permitted, they should be performed
with a bank of approximately 45°, and in no
case at a speed greater than the glider manufacturer’s
recommended airspeeds or the design maneuvering
speed specified for the glider. The design maneuvering
speed is the maximum speed at which the glider can be
stalled or the application of full aerodynamic control
will not exceed the glider’s limit load factor. At or
below this speed, the glider is designed so that it stalls
before the limit load factor can be exceeded.
The objective of demonstrating accelerated stalls is not
to develop competency in setting up the stall, but
rather to learn how they may occur and to develop the
ability to recognize such stalls immediately, and to
take prompt, effective recovery action. It is important
that recoveries are made at the first indication of a
stall, or immediately after the stall has fully developed;
a prolonged stall condition should never be
allowed.
A glider will stall during a coordinated turn as it does
from straight flight except the pitching and rolling
actions tend to be more sudden. If the glider is slipping
toward the inside of the turn at the time the stall occurs,
it tends to roll rapidly toward the outside of the turn as
the nose pitches down because the outside wing stalls
before the inside wing. If the glider is skidding toward
the outside of the turn, it will have a tendency to roll to
the inside of the turn because the inside wing stalls
first. If the coordination of the turn at the time of the
stall is accurate, the glider’s nose will pitch away from
the pilot just as it does in a straight flight stall, since
both wings stall simultaneously.
Glider pilots enter an accelerated stall demonstration
by establishing the desired flight attitude, then
smoothly, firmly, and progressively increasing the
angle of attack until a stall occurs. Because of the rapidly
changing flight attitude, sudden stall entry, and
possible loss of altitude, it is extremely vital that the
area be clear of other aircraft and the entry altitude be
adequate for safe recovery.
Actual accelerated stalls most frequently occur during
turns in the traffic pattern close to the ground or while
maneuvering during soaring flight. The demonstration
of accelerated stalls is accomplished by exerting excessive
back-elevator pressure. Most frequently, it would
occur during improperly executed steep turns, stall and
spin recoveries, and pullouts from steep dives. The
objectives are to determine the stall characteristics of
the glider and develop the ability to instinctively
　
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本文鏈接地址：Glider Flying Handbook(77)