21
more and more turbulent; control response that is perfectly adequate in smooth air will not be good
enough in rougher air. Try flying the glider with the tufts fully reversed; you will probably find that the
glider is somewhat controllable, but only with a lot of 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.
Once you have familiarized yourself with the gliders characteristics in this range of speeds, 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 air-
speed. 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 experience gust induced separa-
tion 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.
Also be aware that in some thermalling situations, such as when trying to maximize climb rate in a
thermal with a very strong and very small core, there may be an advantage in overall effective climb
performance to flying so slowly that some portion of the inside wing is partially stalled most of the
time. This is, however, an advanced and potentially dangerous technique - it is the beginning of a spin
entry, and if pushed just a little too far can result in a sudden and extreme loss of control and / or
altitude. In general, if the tufts are indicating flow reversal associated with the stall, you will improve
both performance and controllability by pulling in and speeding up a little.
One final caution: from time to time a tuft may to stick completely to the sail, and fail to properly
indicate the direction of local flow. This may result from static buildup, or from the fine threads of the
yarn becoming caught on a seam or some dirt or imperfection in the sail. The tuft may stick while
indicating normal flow, but most often it will stick after having reversed, such that the tuft will indicate
a stalled condition that does not exist. One clue in this situation is to note whether or not the tuft is
wiggling. Since flow reversal occurs during a turbulent separated flow, a reversed tuft should be
wiggling rapidly. If it is not, it is probably stuck. A tuft indicating normal flow will not usually wiggle.
An occasional application of silicone spray to the tufts, and making sure that they are positioned so
that they cannot catch on any seam will minimize the problem of sticking.
Summary of Contents for Fusion 141
Page 1: ...Fusion 141 and 150 Owner Service Manual October 15 1998 Third Edition ...
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Page 68: ...Wills Wing 500 West Blueridge Orange CA 92865 Page A 16 Fusion Assembly Diagrams October 1998 ...