Many earlier gliders in the UK are not fitted with nose hooks, just
belly hooks, but we still don't get any cartwheel accidents on
aerotow. There is a slightly increased risk of tug upsets due to
the glider trying to 'winch launch' after take off if the pilot allows
the glider to get too high (so still a good case for keeping your
hand on the release knob during the early stages of an
aerotow). Likewise wire launching by autotow on the belly hook
did not cause cartwheel accidents, despite the slower ground run
acceleration. The difference with high powered winch launches
is that you are putting in much more energy much more quickly,
so the consequences of a wing drop are much more serious.
What happens is that the wingtip contacts the ground, drags,
causes the glider to yaw, so that the other wing speeds up and
produces more lift, adding roll to the yaw and the glider lifts off
with one wing still on the ground. Then the other wing gets up
into the wind gradient and produces even more lift, and at this
point you are history. The safety message is 'keep your wings
level and pull off immediately if you can't'.
Derek Copeland
At 02:09 14 October 2013, Bill D wrote:
I can't comment on why your experience is what it is, but the
BGA is
clearly concerned about "cartwheel" accidents.
Aero tow uses a nose hook so the consequences of a wing
drop are much less.
With the glider achieving flying speed in 3 - 4 seconds that's
not much to
distinguish why earlier or later drop is worse. It's bad
whenever it
happens.
On Sunday, October 13, 2013 1:35:38 PM UTC-6, Terry Walsh
wrote:
OK Bill, here is my problem with your argument that all our
problems are
basically due to too slow acceleration.
1. I have not seen or experienced these slow acceleration
launches and
they
are certainly not the norm at any site at which I have flown
recently.
2. I have also auto towed (some years ago) where the
acceleration is by
definition slow, I never saw a wing drop come close to an
accident.
3. The same applies to aerotows, slow acceleration, here I
have seen wing
drops and witnessed people releasing but no cartwheels.
4. The reason these wing drops have been fatal is that they
occur just
before the glider ls ready to fly. in my mind this implies that
the
acceleration was fast since the glider apparently goes from
insufficient
aileron control to flying speed too quickly for the pilot to
react. I
think perhaps , as Don said that the problem is actually yaw
induced
roll.
Based on what you say we in the UK have a much worse
safety record than
the
Germans, so accepting this I agree that we are apparently
not getting
something right. I do not agree with your analysis and you
have shown no
readiness to accept that there may be another different
problem. This is
what I mean by arrogance. If as you say everybody outside
UK agrees with
your argument why have none of them posted here to say
so.
I think it is a problem caused by individual pilot errors rather
than our
procedures. Why I am not sure although I do have some
thoughts
regarding
pilot currency.
Terry Walsh
At 17:47 13 October 2013, Bill D wrote:
On Thursday, October 10, 2013 4:05:22 AM UTC-6, Terry
Walsh wrote:
Fred,
=20
=20
=20
I did not intend this as a comment against Americans I
know equally
=20
arrogant people of many different national origins. I was
simply
commenti=
ng
=20
that if this indeed Bill Daniels then he could be
considered to be an
=20
expert on winch operations, but his apparent refusal to
accept any
other
=20
opinion than his own was more than a little arrogant.
I've let the UK "echo chamber" run a bit so they can all
congratulate
each
=
other for fuzzy thinking.
Arrogant? Indignant and angry are a better words. Every
time you screw
up=
, it has enormous impact outside the UK. When those
screw-ups are based
on=
institutionalized nonsense, and you try to export that
nonsense, it
makes
=
me angry. An example is the winch launch section in the
2013 Glider
Flying=
Handbook.
The main source of my guidance isn't from the US, or my
own imagination,
i=
t's the German SDO Segelflugbetriebsordnung. It contains
about the best
inf=
ormation on winch launch safety available.
The US stands accused of "doing few winch launches".
That's true.
Compare=
d to the roughly one million annual launches in Germany,
the UK doesn't
do
=
many either. That, and their superb safety record, makes
Germany a far
bet=
ter source of safety information.
If you want an educational approach, read my thoughts on
the
acceleration
p=
hase and acceleration induced uncommanded rotation.
https://dl.dropboxusercontent.com/u/...Acceleration.p
df