Wills Wing Ultra Sport 135, Owner'S Service Manual

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Flying Fast Without Oscillations
The Ultra Sport has some degree of susceptibility to high speed roll / yaw oscillations, as do all high
performance gliders. By using proper flying technique, these oscillations can be avoided or reduced.
They are not “pilot induced” as they are sometimes called, but they can be “pilot controlled.” Specifi-
cally, what is required is that you fly “ahead of the glider” instead of “behind the glider.” Flying ahead
of the glider means being able to sense, by feel, what the glider is about to do in the future rather than
observing what the glider has already done. You must be sensitive enough to the glider that you can feel
that the glider is about to begin veering to one side, and you must be sensitive enough to be able to feel
that the glider is beginning to respond to a correcting control input. Without this sensitivity, you will
instead only be able to respond to your observation that the glider has actually changed heading. By the
time the glider has actually changed heading, the control input to correct is too late.
For example, if the glider gives an indication through pressure in the control bar that it is about to veer
towards the right, the you should immediately respond by inputting a weight shift correction to the left.
The glider at this point hasn’t changed heading. By applying the proper left control input, you will
prevent the change in heading. Then, however, you must be able to feel the glider’s diminishing ten-
dency to veer right (experienced as a reduction of roll bar pressure as the glider begins to respond to
the left control input), and then immediately re-center on the control bar.What pilots tend to do instead
is to input the left correction only after the glider has actually veered to the right, and hold the correc-
tion until the glider’s heading has returned to the original desired heading. The glider in this case will
way overshoot the desired heading, and the oscillation process has begun, and will continue to get
worse as long as the pilot continues to input corrections in response to what the glider has already done
instead of what it is about to do. The other thing pilots often tend to do is to respond to any perception
of loss of control by gripping the bar more tightly and pulling in for more speed. Both of these will
only aggravate a roll/yaw oscillation, as the glider becomes more subject to oscillation the faster one
flies, and the pilot loses all feel for the glider by tightening his grip.There is no way to develop the
sensitivity required to execute these techniques properly, except by lots of experience. There is a set of
techniques that you can use, however, to achieve some measure of the same results. First, at any time
that oscillations are beginning to get out of control, immediately put the bar at the normal trim position
in pitch (slow down to trim speed) and center yourself on the bar. The glider will recover to normal
flight right away. Second, when flying fast, if the glider begins to veer to one side, make a quick, sharp
and deliberate weight shift in the opposite direction, and then immediately return to the center of the
bar (without waiting for the glider to respond). If the first correction of this type isn’t enough, do
another one, but don’t hold the correction longer. This technique approximates the proper technique of
flying ahead of the glider by feel, without requiring the same degree of sensitivity.
The use of optional winglets increases yaw stability and damping and reduces the tendency to oscillate
at all speeds. Winglets also slightly increase roll pressures and slow the roll rate. The use of a tighter
VG setting when flying fast reduces the roll sensitivity of the glider and reduces the tendency to
oscillate. Finally, there is an optional vertical stabilizer available for the Ultra Sport which significantly
increases yaw stability and damping, and is very effective at reducing oscillations.