Windtech serak - Manual (Page 11)

11
> Asymmetric stall (spin)
This is a very difficult situation for the pilot to provoke with the SERAK, given it's very
low stall speed, you have to really abuse the controls a lot to manage it. Even so, this
situation can be induced if, say, the pilot is turning very slowly in a thermal (near the
stall point), and wants to tighten the turn even more, and at the same time as smoothly
lifting the outside brake (which is the correct thing to do), if the pilot simultaneously
brakes more on the inside brake, this may stall the inside wing which will then go into
spin. One half of the wing flies forwards, whilst the other flies backwards (negative). In
this case to return to normal flight, one has to raise the inside brake, returning air speed
to the inside wing, which will cause the wing to surge and dive forwards. This dive can
be more or less violent, depending on what stage that the flat spin is in, how much the
spin had been allowed to develop, and the moment at which the brake is lifted. If the
pilot wants to intervene to dampen this dive, they will have to adopt a position (roughly)
of something more than half brake, which must then be released as soon as the dive is
stopped, or the wing may then go back into a stall or spin. Another option is to put the
glider directly into a full stall immediately that the spin is entered, and from this the exit
is more symmetric with less chance of a twist.
In turbulent air, it is easier to stall part or all of the wing, due to the already broken up
state of a turbulent airflow, and so induce a spin or even a full stall.
> landing
Choose a large field clear of all obstructions & in a
clean laminar airflow.
A different technique is needed for different wind
strengths. Every landing should be judged differently
even if it’s your local site.
On final approach the pilot should have hands up
(keeping a feel of the wing in case of unexpected
turbulence) so the glider has energy for a flare. In
light or nil winds the pilot will need a committed
symmetric flare at around 1 meter above the ground.
In stronger winds less of a flare is needed & the pilot
must judge this for himself through practice & trai-
ning from a qualified instructor.
The flight is not finished, and the pilot is never fully
safe, until the glider is safely controlled on the ground.
Avoid letting the glider land on the leading edge. If the glider lands with force on the
leading edge it is possible to burst the inner cells and walls of the wing and you should
carefully examine the wing for any damage to the joining of the ribs to the cells.