Wills Wing Sport 2 155, Owner'S Service Manual

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To find the glider’s minimum sink speed, fly the glider in smooth air, early in the morning or late in the
afternoon. When you are well away from the terrain, and well clear of other aircraft, look up at the
wing tufts while you very gradually reduce the speed of the glider. Note the speed at which the tufts
indicate a partial spanwise flow - between 30 and 45 degrees of deflection. This is your speed for
minimum sink rate. Familiarize yourself with the position of the control bar relative to your body at this
speed, with the sound and feel of the wind, with the reading on your airspeed indicator, and with the
feel of the glider in terms of pitch and roll pressures. Most of the time when you are flying it will not
be practical to look up for extended periods of time at your tufts. Also, in active air, the tuft behavior
will be affected by transient changes in angle of attack due to gusts. That is why familiarization with
these other, more accessible indicators is important.
After finding your minimum sink speed, experiment with roll control response at speeds just above and
just below this speed to find the value of MCA and the corresponding bar position and other indicators
for this speed. Realize that your effective MCA is going to be higher and higher as the air becomes
more and more turbulent; control response that is perfectly adequate in smooth air will not be good
enough in rougher air. At VG 1/4 or looser, you can try flying the glider with the tufts indicating
spanwise flow or partially reversed. You will probably find that the glider is controllable, but only with
more than normal physical effort. Note that both MCA and MSA come well before the glider actually
“stalls” in the traditional sense, i.e. pitches uncontrollably nose down. You may also be able to sense,
or your vario may tell you that although the glider has not “stalled” (pitched nose down) your sink rate
has increased significantly. In this mode the glider is “mushing.”
The VG rope is marked in 25% increments - one mark indicates VG 1/4, two marks
VG 1/2 or VGM, three marks VG 3/4 and one long mark at the full pull of the rope
indicates VG tight (VGT). The stall and spin characteristics of the Sport 2 are
relatively benign at VG settings of VGM (50% or two marks) and looser. At tighter
VG settings, the stall becomes more abrupt, and the glider becomes easier to spin .
We recommend that flight at speeds less than three mph above minimum sink air-
speed be avoided at VG settings of tighter than 75%, except in relatively smooth air.
We recommend against deliberate spins, or aggressive full breaking stalls, (with the
exception of the landing flare).
Once you have familiarized yourself with the glider’s characteristics in the range of speeds near
minimum sink, you will not need to look at the tufts very often. You will know from bar position and
bar pressure, and from the sound and feel of the relative wind when you are at your minimum sink /
minimum controllable airspeed. In general, you should not fly your glider below this speed. Be aware,
however, that when you are flying at minimum sink in thermal gusts and turbulence, you will experi-
ence gust induced separation of the airflow which will periodically cause the tufts on your sail to
reverse.
Of course in a turn, your minimum sink speed goes up because you are banked, and the bank effec-
tively increases your wing loading which increases your flying speed for any angle of attack. But note
this: The tufts indicate angle of attack, without regard to airspeed! Therefore, if you practice
flying various bank angles in smooth air (while well away from any terrain or other gliders) and watch
your tufts (on the inside wing, which will be at the highest angle of attack) you will get a feel for the
way your minimum sink speed varies at varying bank angles.