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Section 7
Dangerous situations and extreme flying
Collapsing the glider
Asymmetric collapse
Asymmetric collapses are caused by the
stagnation point moving to the trailing edge
of the glider. A negative angle of attack
makes part of the canopy collapse and tuck
under, and the glider may plunge down, turn
away or spin.
Recovery
Should an asymmetric collapse occur,
counter-brake slightly on the side of the
glider that is still inflated to stop it turning
away and to stabilise it, until the glider flies
straight ahead again. With large asymmetric
collapses, it is important to counter-steer
carefully so that the glider does not stall
completely and go into a full stall.
The part of the glider which has collapsed
generally re-inflates automatically but this
can be assisted by applying light brake
pressure on the collapsed side (but not
hectic “pumping”) while counter-steering on
the opposite side. Make use of the full
braking distance.
Following a very large collapse of more than
70%, the wing-tip of the collapsed side may
become trapped in the glider lines. Here too
counter-braking and weight-shifting must be
used to stop the glider from turning away.
The trapped end can generally be opened by
a short, fast pull on the brake lines or by
pulling on the separate stabilo lines.
Front stall
A negative angle of attack can also cause
part or all of the leading edge of the glider to
collapse.
Recovery
The TWIN RS will normally recover quickly
and automatically from a front stall, but re-
inflation can be assisted by light symmetrical
brake input. In the case of extreme front
stalls across the entire wing chord, the wing
tips may move forward making the glider
form a U-shape. Again, recovery is by light
symmetrical braking on both sides, but care
must be taken that both wing ends return to
normal flight evenly.
Types of stall
When a paraglider flies through the air, a
laminar and turbulent boundary layer is
created. Extremely dangerous flight
configurations can result if the laminar
boundary layer is interrupted, with practically
the entire airflow along the top surface
braking away. This happens in particular
when the angle of attack is too great.
There are three different types of stall in
paragliding.
Deep stall
Paragliders can go into a deep stall for a
variety of reasons: brake lines too short (no
slack), old or damaged glider material which
therefore has increased level of permeability,
altered trim/line length and changes to profile
characteristics caused by moisture (e.g.
flying in rain). Paragliders have a particular
tendency to stall if the wing-loading is too
low.
WARNING
Counter-steering too strongly on the
inflated side of the glider can result in a
stall and to further uncontrolled flight
manoeuvres (cascade of events).
WARNING
Full stall and spin are manoeuvres which
can be fatal if recovery is not correct.
These manoeuvres should therefore be
avoided. However, it is important to learn
how to recognise the indications that a
glider is about to stall so that you can take
immediate action to prevent it.
