The apparent cable offset was because we were using a retrieve winch.
However the cable always pulled approximately straight under tension as
the launch commenced. It was normal to place the launch queue on the
downwind side of the retrieve winch, so that any slight weather-cocking at
the start of the launch if anything further reduced the angle between the
cable and the glider, and also reduced the possibility of the wind getting
under the upwind wing. The gliders would have been set up to point at the
main winch, or just slightly upwind of it to reduce any yaw at the start.


IMHO the use of a retrieve winch actually reduces the possibility of a
wing drop, and was not a factor in either case. Particularly in the video,
the glider was running straight before the wing drop occured, and was
probably due to the student pilot failing to do anything positive to keep
the wings level in a slight cross wind from the right, plus a late
take-over by a very newly qualified (at the time) instructor.

Derek Copeland


At 01:00 25 June 2009, Don Johnstone wrote:
What is particularly interesting in both the video and the photographs
is
the direction the glider is pointing relative to the cable. In the video
the glider can be seen to yaw as the cable tightens and then further yaw
as the it starts to move.
In the photographs it is clear that the glider is pointing to the right
of
the direction of the cable AND stangely is pointed in the same direction
as
the K13 parked behind it, a co-incidence perhaps. In both cases it would
appear possible that the glider was not lined up with the cable prior to
launch so that as soon as the cable moved yaw was induced. With a CofG
hook the glider will be more unstable about the yaw axis than was the
case
with the more forward release on older gliders. Perhaps that might
explain
why this appears to be a "new" phenomenon.


At 21:45 24 June 2009, Derek Copeland wrote:
Once a wing drops onto the ground, the glider will almost inevitably
veer
off in the same direction due to ground friction, which is what you see
here and what you also see in my video of a wing drop. The photographer
didn't quite catch the start of this incident, and I am sure that the
glider would have been lined up correctly.

The wing tip runner for the K13 was a very experienced pilot and an ex
syndicate partner of mine. He told me that it was a cold, windy and
very
blustery day and that none of our runways lined up with the wind
direction, so there was about a 30 degree cross wind from the right.
The
chain of events started with a violent gust that caused the wing to
drop
as he let go. The instructor tried to pull off, but his gloved hand
slipped round the round release knob, twice in fact. He was successful
at
the third attempt, but reported that it took a lot more force than he
expected to release under tension. By this time he was airborne, so had
to
take over and fight the glider back onto the ground somehow. What was
interesting was the the eventual landing direction was at right angles
to
the start direction, once the rudder was taken off. The student pilot
may
not have dealt with the dropping wing very well, but there is no
evidence
that he contributed to it.

After this incident, our CFI wanted to fit T handle releases to our
K13s,
but EASA said no because it counted as a major modification and would
require full design approval (very expensive). Bureaucracy gone mad or
what!

Derek Copeland


At 18:54 24 June 2009, bildan wrote:
What I see in that K-13 sequence is the parachute disappearing off
the
left side of the frame after it was released. It gives the appearance
the glider was staged at least 30 degrees off the line of sight to the
winch. I also don't see any aileron or rudder applied in the first
frame with the wing on the ground indicating the pilot was WAAY behind
the glider.

Blaming this 100% on a gust seems a reach.