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Winch Launch Safety Study



 
 
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  #41  
Old March 22nd 09, 04:29 AM posted to rec.aviation.soaring
[email protected]
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Posts: 27
Default Winch Launch Safety Study

Bill,
I also wonder if you have considered gusts and turbulence on elevator
authority. The winch RPM speed is not affected by this and will
continue accelerating if that 's what you want, when gusts or
turbulence affect the elevator. Even Tension controlled winches may
not be able to reduce tension quickly enough if this happens. That's
why the initial tension should not be too high to begin with.

I would like to hear your description of how winch settings should be
with some metrics. I know you advocate high initial tow acceleration
launches. But that doesn't really tell me the specifics.
  #42  
Old March 22nd 09, 11:00 AM posted to rec.aviation.soaring
Del C[_2_]
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Posts: 53
Default Winch Launch Safety Study

As far I can find out, Bill has only done a few hundred launches on rather
underpowered and overgeared old US Gehrlein type winches, plus a couple of
launches on his 'US Superwinch' in a Grob G103 before the drum was
crushed by the synthetic cable, something else I warned him about! The
G103, being low winged and quite heavy, is not prone to over-rotation
accidents anyway, as identified in the Aerokourier report.

I have personally witnessed several vastly overpowered launches involving
K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard
Cirrus and a DG101. They really do go into a near vertical climb, often
despite the best efforts of the pilot to control the rotation.
Particularly in the DG case I was lucky not to join the accidents
statistics, as I slipped back up the seat as the glider rotated and was
only able to keep the stick just off the backstop with my fingertips.

Just about everyone in Europe, where we we have a lot of winch launching
experience, disagrees with Bill's views. As to engineering data, I have
seen none whatsoever from Bill, whereas I have supplied quite a lot plus
illustrative videos on the Yahoo Winch Design Group.

If you know the position of the belly hook and the centres of gravity and
pressure in a given glider, it should be possible to calculate the
rotational couple for various levels of pull, and at what level it will
overpower the elevator.

Derek Copeland

At 01:24 22 March 2009, bildan wrote:
On Mar 20, 7:00=A0am, Derek Copeland wrote:
As I have tried to explain to Bill on numerous occasions, and on

various
forums, the uncontrollable over-rotation you get from an over-powered
winch launch is caused by the pull line to the belly hook being below

the
glider's centre of gravity and centre of pressure. This causes a

rotation
for mechanical rather than aerodynamic control reasons. This is why

high
winged gliders, such as the K6 and K8 are most at risk.

If you get such a launch, even holding the stick hard forward all the

tim=
e
from 'take up slack' will not prevent the over-rotation, although it
might slightly reduce your chances of instant death from a flick spin.

Such events can be easily avoided by by controlling the winch so that

the
ground run acceleration is not more than about 1.0g (or less for the

type=
s
mentioned above). This will still get you airborne and climbing within
about 3-4 seconds, which most pilots find quite fast enough! It will

also
make very little difference to the achieved height.

Derek Copeland

At 22:41 19 March 2009, bildan wrote:

As the glider leaves the ground, the inertial rotation will begin but
if the acceleration continues, the elevator effectiveness will also
continue to increase with the square of the airspeed. =A0Rotation

can't
happen instantly because the glider has mass and rotational inertia.
In fact, the pilot has to start backing off the down elevator to

allow
the glider to rotate into the climb.


Now, contrast this with a slow acceleration. =A0The glider staggers

into
the air and the nose-up inertial couple starts the rotation but the
low speed and acceleration doesn't provide adequate control. =A0The

nose
rises as the pilot struggles to control it with inadequate
airspeed.....


I've collected stories on this type of accident for decades and they
ALWAYS happen with slow acceleration.


And just as often I've challenged you to produce ANY engineering data
to support your mere opinion. You have not and I believe you cannot.

  #43  
Old March 22nd 09, 07:22 PM posted to rec.aviation.soaring
Willy VINKEN[_2_]
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Posts: 1
Default Winch Launch Safety Study

Can anyone tell me more about how a Standard Cirrus handles when
winched?
We use a GMC V8 325 HP petrol engine with standard automatic gearbox.
No problems until now with K8, K6 and Astir Jeans.
I plan to fit my Cirrus with a CG hook. Cirruses imported to France
where all equipped with a nose hook.

Willy VINKEN OO-ZNY


On 22 Mar 2009 10:00:06 GMT, Del C wrote:

As far I can find out, Bill has only done a few hundred launches on rather
underpowered and overgeared old US Gehrlein type winches, plus a couple of
launches on his 'US Superwinch' in a Grob G103 before the drum was
crushed by the synthetic cable, something else I warned him about! The
G103, being low winged and quite heavy, is not prone to over-rotation
accidents anyway, as identified in the Aerokourier report.

I have personally witnessed several vastly overpowered launches involving
K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard
Cirrus and a DG101. They really do go into a near vertical climb, often
despite the best efforts of the pilot to control the rotation.
Particularly in the DG case I was lucky not to join the accidents
statistics, as I slipped back up the seat as the glider rotated and was
only able to keep the stick just off the backstop with my fingertips.

Just about everyone in Europe, where we we have a lot of winch launching
experience, disagrees with Bill's views. As to engineering data, I have
seen none whatsoever from Bill, whereas I have supplied quite a lot plus
illustrative videos on the Yahoo Winch Design Group.

If you know the position of the belly hook and the centres of gravity and
pressure in a given glider, it should be possible to calculate the
rotational couple for various levels of pull, and at what level it will
overpower the elevator.

Derek Copeland

  #44  
Old March 22nd 09, 08:30 PM posted to rec.aviation.soaring
Del C[_2_]
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Posts: 53
Default Winch Launch Safety Study

At 18:22 22 March 2009, Willy VINKEN wrote:
Can anyone tell me more about how a Standard Cirrus handles when
winched?
We use a GMC V8 325 HP petrol engine with standard automatic gearbox.
No problems until now with K8, K6 and Astir Jeans.
I plan to fit my Cirrus with a CG hook. Cirruses imported to France
where all equipped with a nose hook.

Willy VINKEN OO-ZNY

As long as you don't get an overpowered winch launch it's fine. The
ailerons are slightly ineffective at low speed, so try to choose a fit
looking wing runner if you can. If it's one of the all-flying tailplane
versions, just hold the stick about two-thirds forward and leave it there
until you are established in the full climb. Just concentrate on keeping
the wings level and the glider running straight during the ground run and
rotation. If there is any chance of dropping a wingtip onto the ground,
pull off immediately. It will naturally rotate quite enthusiatically after
lift off, but avoid ramming the stick hard forward to contain this, as this
is what can stall the tailplane.

Don't try to winch launch on a nose hook, because it will give a very
poor launch, and there is no back release mechanism on a the type of nose
hook fitted to this type.

The Standard Cirrus doesn't have the best positioned shoulder strap
mountings, so make sure you do your safety harness up as tightly as
possible to avoid slipping back up the seat, due to the acceleration.

Derek Copeland
  #45  
Old March 23rd 09, 12:15 PM posted to rec.aviation.soaring
John Vella Grech
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Posts: 1
Default Winch Launch Safety Study

At 18:22 22 March 2009, Willy VINKEN wrote:
Can anyone tell me more about how a Standard Cirrus handles when
winched?
We use a GMC V8 325 HP petrol engine with standard automatic gearbox.
No problems until now with K8, K6 and Astir Jeans.
I plan to fit my Cirrus with a CG hook. Cirruses imported to France
where all equipped with a nose hook.

Willy VINKEN OO-ZNY
We operated a Standard Cirrus for 3 years on the winch and found no

handling problems provided the elevator was moved progressively. The AMT
is quite powerfull and has been known to stall on full down deflection ,
but we never experienced it .

On 22 Mar 2009 10:00:06 GMT, Del C wrote:

As far I can find out, Bill has only done a few hundred launches on

rather
underpowered and overgeared old US Gehrlein type winches, plus a couple

of
launches on his 'US Superwinch' in a Grob G103 before the drum was
crushed by the synthetic cable, something else I warned him about! The
G103, being low winged and quite heavy, is not prone to over-rotation
accidents anyway, as identified in the Aerokourier report.

I have personally witnessed several vastly overpowered launches

involving
K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard
Cirrus and a DG101. They really do go into a near vertical climb, often
despite the best efforts of the pilot to control the rotation.
Particularly in the DG case I was lucky not to join the accidents
statistics, as I slipped back up the seat as the glider rotated and was
only able to keep the stick just off the backstop with my fingertips.

Just about everyone in Europe, where we we have a lot of winch

launching
experience, disagrees with Bill's views. As to engineering data, I

have
seen none whatsoever from Bill, whereas I have supplied quite a lot

plus
illustrative videos on the Yahoo Winch Design Group.

If you know the position of the belly hook and the centres of gravity

and
pressure in a given glider, it should be possible to calculate the
rotational couple for various levels of pull, and at what level it will
overpower the elevator.

Derek Copeland


  #46  
Old March 24th 09, 07:45 AM posted to rec.aviation.soaring
Gavin Short[_2_]
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Posts: 31
Default Winch Launch Safety Study

At 19:30 22 March 2009, Del C wrote:
At 18:22 22 March 2009, Willy VINKEN wrote:
Can anyone tell me more about how a Standard Cirrus handles when
winched?
We use a GMC V8 325 HP petrol engine with standard automatic gearbox.
No problems until now with K8, K6 and Astir Jeans.
I plan to fit my Cirrus with a CG hook. Cirruses imported to France
where all equipped with a nose hook.

Willy VINKEN OO-ZNY

As long as you don't get an overpowered winch launch it's fine. The
ailerons are slightly ineffective at low speed, so try to choose a fit
looking wing runner if you can. If it's one of the all-flying tailplane
versions, just hold the stick about two-thirds forward and leave it

there
until you are established in the full climb. Just concentrate on keeping
the wings level and the glider running straight during the ground run

and
rotation. If there is any chance of dropping a wingtip onto the ground,
pull off immediately. It will naturally rotate quite enthusiatically

after
lift off, but avoid ramming the stick hard forward to contain this, as
this
is what can stall the tailplane.

Don't try to winch launch on a nose hook, because it will give a very
poor launch, and there is no back release mechanism on a the type of

nose
hook fitted to this type.

The Standard Cirrus doesn't have the best positioned shoulder strap
mountings, so make sure you do your safety harness up as tightly as
possible to avoid slipping back up the seat, due to the acceleration.

Derek Copeland


I concur with Derek. I brace my right arm against my thigh and hold the
stick part way down so any bumps on the ground run will have much less
effect. (I learnt on a UK hill site). Mine has a all flying tail and I do
what Derek describes. I don't need to adjust the position of the stick
(in terms of pitch) until well into the climb and that is just fine
tuning.

Yes, tighten the straps before launch and press firmly back on the pedals
before launch to compress parachute/back rest arrangements (I have 50mm of
dynafoam behind me) to ensure you don't slip back on launch.

No problems with a V8 power Tost winch.

Fitting winglets last season made the ailerons more responsive at low
speed.

Read the flight manual about launching (which basically says what Derek
and I have). Also look at the Standard Cirrus website
http://www.standardcirrus.org
and also look at the Std Cirrus Forum. There is a search facility so look
for 'launch'.

The Std Cirrus hook is well protected by 2 parallel metal strips.
Practice getting the cable on yourself so you can describe to helpers how
they should fit the cable. They tend to get a bit confused because they
can't see the hook like K8s and Astirs etc.

As my first CFI says: Its a glider - go any fly it as you would a glider!





Gavin
Std Cirrus, CNN now G-SCNN, #173
LSV Viersen, Keiheuvel, Belgium
  #47  
Old March 24th 09, 01:45 PM posted to rec.aviation.soaring
MaD
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Posts: 46
Default Winch Launch Safety Study

In addition to what Gavin and Derek said I think it is also important
to know that the location of your Centre of Gravity has a significant
influence on the winch launch characterisitics of the Standard Cirrus.
Make sure it is no-where near the rear end of the allowable range. I
can't remember the figures but recall having it close to mid-range and
always felt comfortable.
To prevent sliding into the baggage compartment I always took the
pedals right back and trapped myself between pedals and rear canopy
rim during winch launch.

Marcel Dünner
  #48  
Old March 24th 09, 02:45 PM posted to rec.aviation.soaring
Derek Copeland[_2_]
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Posts: 146
Default Winch Launch Safety Study

Some of you might be interested in the latest British Gliding Association
(BGA) Winch Launching Safety Campaign, which includes some frightening
simulations of what can go wrong if you approach winching in a too
cavalier manner. Taking off with the stick hard back, possibly as a result
of sliding back up the seat, is one of them, and has been responsible for
several fatal accidents in the UK. See:

http://www.gliding.co.uk/bgainfo/saf...nch-safety.htm

Derek Copeland

At 12:45 24 March 2009, MaD wrote:
In addition to what Gavin and Derek said I think it is also important
to know that the location of your Centre of Gravity has a significant
influence on the winch launch characterisitics of the Standard Cirrus.
Make sure it is no-where near the rear end of the allowable range. I
can't remember the figures but recall having it close to mid-range and
always felt comfortable.
To prevent sliding into the baggage compartment I always took the
pedals right back and trapped myself between pedals and rear canopy
rim during winch launch.

Marcel D=FCnner

  #49  
Old March 24th 09, 05:17 PM posted to rec.aviation.soaring
ucsdcpc
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Posts: 10
Default Winch Launch Safety Study

...... and do the quiz .....

chris

On 24/03/2009 1:45 PM, Derek Copeland wrote:
Some of you might be interested in the latest British Gliding Association
(BGA) Winch Launching Safety Campaign, which includes some frightening
simulations of what can go wrong if you approach winching in a too
cavalier manner. Taking off with the stick hard back, possibly as a result
of sliding back up the seat, is one of them, and has been responsible for
several fatal accidents in the UK. See:

http://www.gliding.co.uk/bgainfo/saf...nch-safety.htm

Derek Copeland

At 12:45 24 March 2009, MaD wrote:
In addition to what Gavin and Derek said I think it is also important
to know that the location of your Centre of Gravity has a significant
influence on the winch launch characterisitics of the Standard Cirrus.
Make sure it is no-where near the rear end of the allowable range. I
can't remember the figures but recall having it close to mid-range and
always felt comfortable.
To prevent sliding into the baggage compartment I always took the
pedals right back and trapped myself between pedals and rear canopy
rim during winch launch.

Marcel D=FCnner

  #50  
Old March 24th 09, 05:18 PM posted to rec.aviation.soaring
bildan
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Posts: 646
Default Winch Launch Safety Study

On Mar 21, 9:00*pm, wrote:
Bill,
Aside from your rude remarks and your inability to admit your mistakes
on several points (an automatic transmissions do not operate like a
cruise control), etc.....


I didn't say anything remotely like that. I said they ASSIST the
driver in maintaining speed by increasing torque multipication when
climbing hills.


Now let me ask you a question for once: What rope tension, measured in
g do you recommend for the first seconds of the launch? Or do you
advocate RPM controlled winches over tension controlled ones?


I advocate tension controlled winches and the tension should be the
maximum safe value.

 




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