Windtech evo - Manual (Page 13)

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thrust, especially as you increase power. If the pilot encounters an area of turbulence just
as they apply power (they are pushed forward by the power of the engine and the angle
of attack of the wing therefore increases), one should be extremely careful as the con-
trol and flight behaviour of the wing is very different whilst under power.
In turbulent conditions, it is possible for your wing to suffer from either an “asymmetric” or
“symmetric” collapse. Also known as “tucks”, these are described in the following paragraphs,
along with a description of what to expect and the recovery techniques recommended.
-- asymmetrical tuck/collapse
An asymmetric collapse, is a longitudinal (lengthwise) collapse of a part of the wing (say
20 – 70%) which is normally caused by turbulence (although it is also possible to induce
collapses through poor pilot input). In un-powered flight, any tucks or collapses on the
EVO should sort themselves out automatically within 90 degrees. If you have a collapse
whilst under power, you should always ease off the thrust gradually, as the thrust of the
motor can considerably complicate the wing’s reactions and recovery behaviour. In any
case, and setting timmers to neutral position, the pilot should know how to first prevent
and, failing this, to deal with, an asymmetric collapse. They should also be familiar with
the required recovery procedures and techniques to return the glider to normal flight,
with the minimum loss of height or directional control.
If you have an asymmetric collapse, remember: “Course, then Correction”. First try to
maintain a SAFE course, WITHOUT STALLING THE WING BY OVER-CORRECTING, by first
weight shift towards the (still inflated) flying side of the wing (this will give a better wing
loading and augment the internal pressure of the wing) and apply around 20-40% brake
on the open side of the wing to try to minimise the turn induced by the collapse.
Remember that you should have gradually reduced the power of the engine.
BE CAREFUL when trying to stop the turn of the glider after a collapse not to use too
much brake and so stall the flying part of the wing, as this could cause more problems
than the collapse itself. Once you have maintained a safe course, and minimized the turn
induced by the collapse, you can apply CORRECTION to re-inflate the collapsed side of
the wing by giving smooth but firm pumps on the brake on the collapsed side, holding
down the brake until the glider re-inflates. Do not give small ‘panicky’ dabs of brake to
the collapsed side of the wing as this does not really help and will make the wing take
much longer to re-inflate. Once the wing re-inflates be careful not to hold down the
brake too much, for too long, as this could stall the wing, or induce a spin.
-- front/symmetrical tuck collapse
SET TRIMMERS TO NEUTRAL POSITION
T his is when the whole leading edge of the wing, from the centre to the tips, collapses.
It is possible to have a front tuck on exit from a strong thermal, when using the speed
system or trimmers in turbulent conditions, hitting a (wind) shear layer, etc. Generally,
this situation does not require any pilot intervention as the glider will re-inflate quickly,