Wills Wing Alpha 180 Owner's Service Manual page 32

Final proper adjustment of the bridles is determined by sighting the shadow of the bridles on the sail
in flight. With the glider in a 30 degree banked turn at Vms, shake the control bar sharply and observe
the shadow of the bridles according to the following criteria:
Tight No movement in the line, the line is straight and appears under tension.
Snug Minimal movement, no apparent curve in the line but no apparent tension.
Just Slack The center of the bow in the line moves one to two inches either side of its rest posi-
tion. Some apparent curve in the line may be seen without shaking the bar.
Slack The center of the bow in the line moves two to four inches either side of its rest posi-
tion. Definite slack in the line can be seen without shaking the bar.
Quite Slack The center of the bow in the line moves four or more inches either side of its rest
position. Slack in the line can be easily seen without shaking the bar.
The bridles are properly adjusted when they sight between just slack and slack in the above test. Ad-
justment of the bridles requires replacing the bridle pigtail with one of a shorter (to tighten) or longer
(to loosen) length, or shimming the bridles from underneath the trailing edge.
Improper adjustment of the bridles will affect the glider's pitch stability and flight characteristics in
the following ways:
Bridles too loose
If the bridles are adjusted too loose, it will not affect the glider in normal flight as the bridles are
always slack in this range anyway. At angles of attack below normal flight, there will be a reduction
in pitch stability proportional to the amount by which the bridles are looser than they are supposed to
be. This stability reduction could increase the probability of a turbulence induced tumble or other in-
flight stability related loss of control.
Bridles too tight
If the bridles are adjusted too tight, it will compromise the flight characteristics of the glider. The
effects of too tight bridles are to increase roll control pressures and reduce roll rate in circumstances
where maximum control input is applied.
Other factors of glider geometry which affect bridle adjustment and effectiveness
The effective adjustment of the bridles is also affected by other aspects of the glider geometry. For
example, if the bottom side wires are too long, it will allow the wings to rise and slacken the bridles
in normal flight. If they are too short, it will pull the wings down, and tighten the bridles in normal
flight.
If the top side wires are too short, it will reduce the amount the wings can "fold" downwards as the
glider unloads at low angles of attack, thereby reducing the effectiveness of the bridles.
Changes from proper length to the top or bottom side wires will also change the relative adjustment of
the inner and outer bridles to each other, and change the way they operate.
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