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techniques. In this phase, the aerodynamic and inertial
forces have not achieved a balance. As the incipient
spin develops, the indicated airspeed should be near or
below stall airspeed.
The incipient spin recovery procedure should be commenced
prior to the completion of 360° of rotation. The
pilot should apply full rudder opposite the direction of
rotation.
7-33
spin indefinitely, even with anti-spin inputs. A brisk
and positive technique, on the other hand, results in a
more positive spin recovery.
Step 5—Begin applying back-elevator pressure to
raise the nose to level flight. Caution must be used
not to apply excessive back-elevator pressure after the
rotation stops. Excessive back-elevator pressure can
cause a secondary stall and result in another spin. Care
should be taken not to exceed the “G” load limits and
airspeed limitations during recovery.
It is important to remember that the above-spin recovery
procedures are recommended for use only in the
absence of the manufacturer’s procedures. Before any
pilot attempts to begin spin training, the pilot must be
familiar with the procedures provided by the manufacturer
for spin recovery.
The most common problems in spin recovery include
pilot confusion in determining the direction of spin
rotation and whether the maneuver is a spin versus spiral.
If the airspeed is increasing, the glider is no longer
in a spin but in a spiral. In a spin, the glider is stalled
and the airspeed is at or below stalling speed.
COMMON ERRORS
• Failure to clear area before spins.
• Failure to establish proper configuration prior
to spin entry.
• Failure to recognize conditions leading to a
spin.
• Failure to achieve and maintain stall during
spin entry.
• Improper use of controls during spin entry,
rotation, and/or recovery.
• Disorientation during spin.
• Failure to distinguish a spiral dive and a spin.
• Excessive speed or secondary stall during spin
recovery.
• Failure to recovery with minimum loss of
altitude.
MINIMUM SINK AIRSPEED
Minimum sink airspeed is defined as the airspeed at
which the glider loses the least amount of altitude in a
given period of time. Minimum sink airspeed varies
with the weight of the glider. Glider manufacturers
publish the altitude loss in feet per minute or meters
per second (e.g. 122 ft/min or 0.62 m/sec) at a specified
weight. Flying at minimum sink airspeed results
in maximum duration in the absence of convection in
the atmosphere.
The minimum sink airspeed given in the GFM/POH is
based on the following conditions.
• The glider is wings-level and flying a straight
flight path; load factor is 1.0 G.
• The glider flight controls are perfectly
coordinated.
• Wing flaps are set to zero degrees and air
brakes are closed and locked.
• The wing is free of bugs or other
contaminants.
• The glider is at a manufacturer-specified
weight.
While flying in a thermalling turn, the proper airspeed
is the minimum sink airspeed appropriate to the load
factor, or G-load, that the glider is undergoing. The
glider’s stall speed increases with load factor. The minimum
sink speed needs to be increased with an
increase in load factor. For example, if a glider stall
speed is 34 knots and the wings-level minimum sink
airspeed is 40 knots, consider the following for thermalling.
• In a 30° banked turn, load factor is 1.2 Gs. The
approximate square root of 1.2 is 1.1. Thirtyfour
knots times 1.1 yields a 37 knots stall
speed. The minimum sink speed is still above
the stall speed but by only approximately 3
knots. The margin of safety is decreasing and
the pilot should consider increasing the minimum
sink speed by a factor proportionate to
the stall speed increase, in this case 44 knots.
• In a 45° banked turn, load factor is 1.4 Gs. The
approximate square root of 1.4 is 1.2. Thirtyfour
knots times 1.2 yields a 41 knots stall
speed. The minimum sink speed is now below
the stall speed. If the pilot increases the mini
mum sink speed proportionately to the stall
airspeed, the new speed would be 48 knots, a
7 knot safety factor.
• In a 60° banked turn, load factor is 2.0 Gs. The
approximate square root of 2.0 is 1.4. Thirtyfour
knots times 1.4 yields a 48 knots stall
speed. The minimum sink speed is now below
the stall speed. The pilot should increase the
minimum sink speed proportionately to 56
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Glider Flying Handbook(81)
