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Attention: Never pull the brake-lines during a parachutal stall, because the
glider would go into a full stall immediately.
Does the glider stay in a repetitively parachutal stall without any
noticeable reason the glider have to be checked before the next
flight.
Rain-induced Deep / Parachute Stall
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 Big
Ears or B-Line-Stall, and that you steer clear of turbulence and avoid a deep flare
on landing.
Attention:
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!
Asymmetric Collapse
While flying in turbulent conditions it may occur that a portion of your glider
deflates. This is normally not a critical situation and re-inflation occurs quickly
without any input from the pilot.
However, just like in flying in turbulences, please pull gently on both brakes. Re-
inflation is speeded up by counteracting the turning movement of the canopy until
normal forward flight return. Then pump the brake line on the collapsed side.
Attention: If the collapsed part of the canopy is very big, you have to break
the open side very dosed (not too much!) to avoid a stall.
