Keep your hand off the release handle during aero tows!

At 21:07 15 October 2013, Del Copeland wrote:
Bill D has gone remarkably quiet!

Damn! The rest of us were hoping you had gone into hibernation too.

At 08:12 16 October 2013, Z Goudie wrote:
At 21:07 15 October 2013, Del Copeland wrote:
Bill D has gone remarkably quiet!

Damn! The rest of us were hoping you had gone into hibernation too.


Well it is raining

Paul did allow for the greater number of glider pilots and winch
launches in Germany and his figures are for fatal and serious
injury accidents only. As I have pointed out to you before, the
BGA accident statistics include all minor accidents and incidents
that are even vaguely related to winch launching and which do
not cause death or serious injury. There are probably 10 such
incidents for every serious accident which probably explains the
difference. There are lies, damn lies, and your interpretation of
accident!

Derek Copeland


At 13:43 14 October 2013, Bill D wrote:
On Monday, October 14, 2013 3:43:07 AM UTC-6, Paul Ruskin
wrote:
On Monday, October 14, 2013 3:03:44 AM UTC+1, Bill D
wrote:

I don't get accident statistics from RAS comments.


Which would be an admirable position Bill, except that I took
the trouble
to go and find the accident reports from the BFU and BGA and
posted a list
of winch accidents in my comment, including sources and
accident report
numbers.



The data says that in the period 2006-12 a German pilot had
much the same
chance as a UK civilian pilot of being killed or injured in a
winch
accident.



Perhaps you'd let us know whether you now accept that
conclusion, rather
than claiming that UK winch launches are 10 times more
dangerous?





Paul

Yes, I read your ramble. The operable statistic is number of
accidents per
number of launches - very simple and not included in your
post.

For 2011 (The numbers just look worse for the UK the further
back one
goes.)
The Germans suffered one accident every 180,000 launches
The UK suffered one every 16,000 launches.

That's better than 10:1 and the number can't be twisted to
show parity.

At 02:03 14 October 2013, Bill D wrote:
I don't get accident statistics from RAS comments.

The Dropbox link has changed. See:
https://dl.dropboxusercontent.com/u/...Acceleration.p
df


Maybe the ancient Gehrlein winches you have in the US are not
powerful enough to cause uncontrollable pitch ups, but we did
have a problem with this when we first had powerful V8 Tost
winches. K8's and the like would rocket up almost vertically
before (usually) the weak link broke. Fortunately none of them
flicked and all the pilots involved were quite switched on and
managed to get the nose down and land safely. The problem
was largely solved by opening the throttle a bit more gently at
the start of the launch. The nice thing about the Skylaunch
winches we have now is that they deliver the right amount of
power for the glider type being launched, so you get the same
ground run time for all types. So one less type conversion issue.

The acceleration induced pitch up effect is only transitory by the
way. During the ground run it is constrained by the tailwheel,
and once the glider is safely established in the full climb the pull
line and the c of g become more closely aligned. The dangerous
bit is the rotation! If the mainwheel lifts off first, the glider
pitches up to a steep angle and then the tailwheel lifts off and no
longer constrains the pitch angle, it is at this point the wings may
stall, and if any yaw is present may flick roll. The safety
message is don't over-accelerate lightweight gliders and control
the rotation rate so that it is not more than 10 degrees per
second.

Derek Copeland