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the Cu. Often, only very weak lift, barely enough to
climb at all, is found in smooth air upwind of the cloud.
Once above cloud base and upwind of the Cu, climb
rates of a few hundred fpm can be found. Climbs can
be made by flying back and forth upwind of an individual
Cu, or by flying along cloud streets if they exist. If
no clouds are present, but waves are suspected, climb
to the top of the thermal and penetrate upwind in search
of smooth, weak lift. Without visual clues, thermal
waves are more difficult to work. Thermal waves are
most often stumbled upon as a pleasant surprise when
their presence is furthest from the pilot’s mind.
RIDGE AND SLOPE SOARING
Efficient slope soaring (also called ridge soaring) is
fairly easy; simply fly in the updraft along the upwind
side of the ridge (see Figure 9-20). The horizontal distance
from the ridge will vary with height above the
ridge, since the best lift zone tilts upwind with height
above the ridge. Even though the idea is simple, traps
exist for both new and expert glider pilots. Obtain
instruction when first learning to slope soar.
Avoid approaching from the upwind side perpendicularly
to the ridge. Instead, approach the ridge at a shallower
angle, so that a quick egress away from the ridge
is possible should lift not be contacted. While flying
along the ridge, a crab angle is necessary to avoid drifting
too close to the ridge or, if gliding above the ridge,
to avoid drifting over the top into the lee-side downdraft.
For the new glider pilot, crabbing along the ridge
may be a strange sensation, and it is easy to become
uncoordinated while trying to point the nose along the
ridge. This is both inefficient and dangerous, since it
leads to a skid toward the ridge. [Figure 10-14]
In theory, to obtain the best climb, it is best to slope
soar at minimum sink speed. However, flying that
slowly may be unwise for two reasons. First, minimum
sink speed is relatively close to stall speed, and flying
close to stall speed near terrain has obvious dangers.
Second, maneuverability at minimum sink speed may
be inadequate for proper control near terrain, especially
if the wind is gusty and/or thermals are present. When
gliding at or below ridge top height, fly faster than minimum
sink speed—how much faster depends on the
glider, terrain, and turbulence. When the glider is at
least several hundred feet above the ridge and shifting
upwind away from it in the best lift zone, reduce speed.
If in doubt, fly faster!
Slope soaring comes with several procedures to enable
safe flying and to allow many gliders on the same
ridge. The rules are:
1. make all turns away from the ridge;
2. do not fly directly above or below another glider;
3. pass another glider on the ridge side, anticipating
that the other pilot will make a turn away from
the ridge; and
4. the glider with its right side to the ridge has the
right of way. [Figure 10-15]
15 Kt 15 Kt
Increased Radius
of Turn With Wind
Ridge
Safer, Angled
Approach, Then
Set Crab Angle
Normal Radius
of Turn - No Wind
Strong Lee-side Sink
Figure 10-14. Flying with a wind increases the turn radius over the ground, so approach the ridge at a shallow angle.
10-10
These procedures deserve some comment.
Procedure #1: A turn toward the ridge is dangerous,
even if gliding seemingly well away from the ridge.
The ground speed on the downwind portion of the turn
will be difficult to judge properly, and striking the ridge
is a serious threat. Even if above the ridge, it will be
easy to finish the turn downwind of the ridge in heavy
sink.
Procedure #2: Gliders spaced closely together in the
vertical are in each other’s blind spots. A slight change
in climb-rate between the gliders can lead to a collision.
Procedure #3: Sometimes the glider to be passed is so
close to the ridge that there is inadequate space to pass
between the glider and the ridge. In that case, either
turn back in the other direction (away from the ridge) if
traffic permits, or fly upwind away from the ridge and
rejoin the slope lift as traffic allows. When soaring outside
of the United States, be aware that this rule may
differ.
Procedure #4: Federal Aviation Regulations call for aircraft
approaching head-on to both give way to the right.
A glider with the ridge to the right may not have room
to move in that direction. The glider with its left side to
the ridge should give way. When piloting the glider
with its right side to the ridge, make sure the approaching
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Glider Flying Handbook(141)
