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control is maintained by timely application of coordinated
rudder pressure. Therefore, it is important that
the rudder be used properly during both the entry and
the recovery from a stall. The primary use of the rudder
in stall recoveries is to counteract any tendency of
the glider to yaw or slip. The correct recovery technique
would be to decrease the pitch attitude by applying
forward elevator pressure to reduce the angle of
attack and while simultaneously maintaining directional
control with coordinated use of the aileron and
rudder.
Due to engineering design variations, the stall characteristics
for all gliders cannot be specifically
described; however, the similarities found in gliders
are noteworthy enough to be considered. The factors
that affect the stalling characteristics of the glider are
weight and balance, bank and pitch attitude, coordination,
and drag. The pilot should learn the effect of the
stall characteristics of the glider 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 in the case of a self-launch glider,
depending on the total number of factors affecting the
particular glider.
Whenever practicing stalls while turning, a constant
bank angle should be maintained until the stall occurs.
After the stall occurs coordinated control inputs
should be made to return the glider to level flight.
ADVANCED STALLS
Advanced stalls include secondary, accelerated, and
crossed-control stalls. These stalls are extremely useful
for pilots to expand their knowledge of stall/spin
awareness.
7-28
If stalls are practiced or encountered in a self-launch
glider, the maximum allowable power should be
applied during the stall recovery to increase the selflaunch
glider’s speed and assist in reducing the wing’s
angle of attack. Generally, the throttle should be
promptly, but smoothly, advanced to the maximum
allowable power. Although stall recoveries should be
practiced without, as well as with the use of power, in
self-launch gliders during actual stalls the application
of power is an integral part of the stall recovery.
Usually, the greater the power applied, the less the loss
of altitude. Maximum allowable power applied at the
instant of a stall usually does not cause overspeeding
of an engine equipped with a fixed-pitch propeller,
due to the heavy air load imposed on the propeller at
slow airspeeds. However, it will be necessary to
reduce the power as airspeed is gained after the stall
recovery so the airspeed does not become excessive.
When performing intentional stalls, the tachometer
indication should never be allowed to exceed the red
radial line (maximum allowable RPM) as marked on
the instrument.
Whether in a glider or self-launched glider, wings
level, straight flight should be regained with coordinated
use of all controls. The first few practices should
consist of approaches to stalls, with recovery initiated
as soon as the first buffeting or partial loss of control is
noted. In this way, the pilot can become familiar with
the indications of an approaching stall without fully
stalling the glider.
Stall accidents usually result from an inadvertent stall
at a low altitude in which a recovery was not accomplished
prior to contact with the surface. As a preventive
measure, stalls should be practiced at an altitude
that allows recovery at no lower than 1,500 feet AGL.
Different types of gliders have different stall characteristics.
Most gliders are designed so the wings stall progressively
outward from the wing roots (where the
wing attaches to the fuselage) to the wingtips. This is
the result of designing the wings so the wingtips have a
smaller angle of incidence than the wing roots. Such a
design feature causes the wingtips to have a smaller
angle of attack than the wing roots during flight.
Exceeding the critical angle of attack causes a stall.
Since the wing roots will exceed the critical angle
before the wingtips, they will stall first. The wings are
designed in this manner so aileron control will be
available at high angles of attack (slow airspeed) and
give the glider more stable stalling characteristics.
When the glider is in a stalled condition, the wingtips
continue to provide some degree of lift, and the
ailerons still have some control effect. During recovery
from a stall, the return of lift begins at the tips and
7-29
SECONDARY STALL
This stall is called a secondary stall because it may
　
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本文鏈接地址：Glider Flying Handbook(76)