UP Kantega XC, Owner'S Manual

Page: 33 / 66

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There are two reasons why flying with a
wet wing increases the risk of deep
stalling:
First reason is that the canopy cloth may
absorb water, making it much heavier and
moving the centre of gravity around in
unpredictable ways, increasing the risk
of a stall/deep stall. The more water a
wing can absorb the higher the risk,
which means that older wings with
damaged coating are more prone to these
deep stalls than new wings. It should also
be noted that a wing already flying close
to the edge due to line shrinkage or other
factors will deep stall sooner due to water
absorption.
Second reason has to do with the actual
rain drops on the top surface – if enough
large rain drops form that the entire top
surface is covered, but they don’t join
together to either flow off or become a
homogenous mass, the surface will
become so rugged that the airflow
separates and the wing stalls.
This phenomenon has been observed on
hang gliders and gliders for years but
only recently have we discovered that
paragliders may also be affected. It is
more likely to happen with new wings
where the cloth is still highly hydrophobic
and the drops thus do not penetrate but
remain on the surface.
We know from computer simulations and
practical tests that this is physically
possible but we also suspect that it occurs
very seldom in real life flying.
In both cases the brakeline travel
becomes very short and even small input
may suddenly induce an airflow
separation; in some cases even a gust or
a sudden thermal may change the angle
of incidence enough to cause the deep
stall.
If you find yourself flying in
unavoidable rain we strongly
recommend that you avoid any sudden
movements or radical brakeline input,
that you do not pull BigEars or B-stall,
and that you steer clear of turbulence
and avoid a deep flare on landing.
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Avoid flying in very
humid air or in rain. A wet
canopy may have very
unpredictable flying
characteristics, one of which is
a radically increased risk of deep
stall!
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Always make sure that your intended
logo will not in any way influence the
glider behaviour. If in doubt we
suggest avoiding the attachment of
advertising logos on the wing. UP
cannot be held responsible for any
mishaps caused by intentional after-
sales changes done to the wing.
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Attaching heavy
adhesive logos made out of
unsuited material to the wing
may result in the revocation
of the glider certification.