Winch Launch Safety Study

Originally Posted by

Bill said:
"... the tension should be the maximum safe value."

OK, let me try this again. Maybe you'll understand this question:

1. In your opinion, what is the maximum safe value expressed in g, for
he initial launch phase?
2. Who else agrees with your position that the initial launch phase
should be aggressive? In this thread alone, nobody agrees with you.
Where are all these people? Mr. George Moore has also said he
advocates a slower launch than you do on the Yahoo groups site.
"Bill has advocated higher ground acceleration rates than I am
generally comfortable with."

I haven't heard a single person support what you advocate. Whatever
you find, please with verifiable quotes.

- And I don't know were your get your sense of what rude is, but
publicly and falsely claiming I am misrepresenting my identity without
any proof on your part what so ever, certainly is rude behavior.

I would support a fair bit of what Bill says, which may be why my previos post has been ignored.

Many of our sports members fall into the old dogs and new tricks area, I have a feeling the more experience one has in anything, the more they push against change, especially as we grow older.

I must disagree with Dereks' statement on measuring tension as well, it is a simple thing to do. Perhaps it hasnt been done, sure, but its not hard. (Caveat- I sell loadcells and measurement equipment for a living)

As I have stated, If we can identify we have a problem (we do, people have died) why would we not change? Technology is allowing change, embrace it.
If, with respect of time, we see we were wrong and can change back, what harm? At least we tried.

We can set up winches to do any damn thing we like, every time, regardless of wind gusts, temperature changes, altitute differences, ballast, number of pilots, student requirements, winchperson ability, emergency airspace violations etc, etc. So lets!

If you dis-agree, dont fly off the new winch, simple!


Bagger

In the UK, Holland and Germany about two-thirds of glider launches are done
by winch, so we have a fair bit of experience in this technique. Prior to
about the early 1980s winches were fairly asthmatic things, but the sort
of ideas that Bill is advocating now where tried out as more powerful, big
engined winches such as the Tost and Van Gelder, became available, and
where quickly found to be somewhat dangerous! As the Americans are at last
starting to get into winching, I am just trying to stop them re-inventing a
rather dangerous wheel. All you have to do in reality is to slightly
restrict the power given to those types of glider that can't safely use
it!

Even a fully automated, computerised winch can fall foul of finger trouble
in inputing the launch data, so even there it is best to err slightly on
the size of caution.

Bill has suggested that slowly accelerated launches are more likely to
cause flick spins. That being the case we should have had plenty of these
when we autotowed, where the acceleration is very slow, but we didn't!

If you have a system or a gadget that you can clamp to a winch to directly
measure cable tension, I for one would like to know about it. RLTs seem to
be limited to about 40mph maximum cable speed, which is not enough. The
other approach is to mount a load cell in the glider's hook mount, or at
the glider end of the cable with a radio transmitter to transmit data back
to the winch. The former would be rather expensive for glider owners and
for clubs with a lot of gliders, while the latter would be prone to
breakages when dropped from 2000ft!

Derek Copeland


At 09:59 25 March 2009, bagmaker wrote:

I would support a fair bit of what Bill says, which may be why my
previos post has been ignored.

Many of our sports members fall into the old dogs and new tricks area,
I have a feeling the more experience one has in anything, the more they
push against change, especially as we grow older.

I must disagree with Dereks' statement on measuring tension as well, it
is a simple thing to do. Perhaps it hasnt been done, sure, but its not
hard. (Caveat- I sell loadcells and measurement equipment for a
living)

As I have stated, If we can identify we have a problem (we do, people
have died) why would we not change? Technology is allowing change,
embrace it.
If, with respect of time, we see we were wrong and can change back,
what harm? At least we tried.

We can set up winches to do any damn thing we like, every time,
regardless of wind gusts, temperature changes, altitute differences,
ballast, number of pilots, student requirements, winchperson ability,
emergency airspace violations etc, etc. So lets!

If you dis-agree, dont fly off the new winch, simple!


Bagger




--
bagmaker

On Mar 25, 3:59*am, bagmaker
wrote:
;687487 Wrote:





Bill said:
"... the tension should be the maximum safe value."

OK, let me try this again. Maybe you'll understand this question:

1. In your opinion, what is the maximum safe value expressed in g, for
he initial launch phase?
2. Who else agrees with your position that the initial launch phase
should be aggressive? In this thread alone, nobody agrees with you.
Where are all these people? Mr. George Moore has also said he
advocates a slower launch than you do on the Yahoo groups site.
"Bill has advocated higher ground acceleration rates than I am
generally comfortable with."

I haven't heard a single person support what you advocate. Whatever
you find, please with verifiable quotes.

- And I don't know were your get your sense of what rude is, but
publicly and falsely claiming I am misrepresenting my identity without
any proof on your part what so ever, certainly is rude behavior.

I would support a fair bit of what Bill says, which may be why my
previos post has been ignored.

Many of our sports members fall into the old dogs and new tricks area,
I have a feeling the more experience one has in anything, the more they
push against change, especially as we grow older.

I must disagree with Dereks' statement on measuring tension as well, it
is a simple thing to do. Perhaps it hasnt been done, sure, but its not
hard. (Caveat- I sell loadcells and measurement equipment for a
living)

As I have stated, If we can identify we have a problem (we do, people
have died) why would we not change? Technology is allowing change,
embrace it.
If, with respect of time, we see we were wrong and can change back,
what harm? At least we tried.

We can set up winches to do any damn thing we like, every time,
regardless of wind gusts, temperature changes, altitute differences,
ballast, number of pilots, student requirements, winchperson ability,
emergency airspace violations etc, etc. So lets!

If you dis-agree, dont fly off the new winch, simple!

Bagger

--
bagmaker

Thanks for that.

This discussion always gets the "Safety Nazis" wringing their hands
and wailing every time. ( But never, ever, producing any hard data.)
The thing is - it's mostly a trivial "tempest in a teapot".

To get the absolute maximum acceleration possible for a glider, just
divide a gliders flying weight into its specified weak link strength.
(Tost weak links are now calibrated to +or- 5%) That value is always
around 1.2G - if you don't believe it, read your manual. If you try
to accelerate the glider with more force than that, the link breaks in
the takeoff roll and the glider never gets airborne.

Since even the most conservative old fart thinks than .8 to .9 G is OK
for most gliders, this whole frightful affair is all about an
approximately .3G range which is buried in the 'noise'. Most pilots
can't detect the difference.

I've had brand new Tost weak links fail in the rotation phase on many
occasions as a result of too much cable tension from one of those
"underpowered US winches". I was nowhere near the limit of down
elevator authority. The most recent involved a 2-33 whose CG is at
least 3 feet above the hook and whose tiny horizontal tail severely
limits down elevator authority.

Again, the disclaimer, there are a very few mostly old gliders with a
problem which thankfully are very rare in the US. Pilots of these
should check with knowledgeable people for the special launching
technique required. Virtually all gliders in the US winch just fine.

I strongly suspect the problem is isolated to the UK, where they do
fly old gliders, and has to do with a particular new 'powerful winch'
which is capable of enormous force in first gear and which shifts to
second gear at some unknown and uncontrollable point during the
rotation phase. The tension data which IS available for this winch
looks pretty scary.

Dereks voluminous criticism of computer controlled automatic tension
winches stems from the fact that HIS favorite winch has no such
controls and he's afraid that US winch builders using Automatic
Tension Control will steal the market.

Everyone has experienced the imprecise surging when backing a car with
an automatic transmission to align a tow ball with a trailer hitch.
Imagine trying to control the acceleration a 1000 pound glider with a
drive train intended for a 6000 pound road vehicle.

Anyone who thinks any of this is not true, needs to produce some valid
measurements to the contrary. I believe validated data.

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.

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

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

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

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

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

On Mar 22, 4:00*am, 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

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.

Derek, I have more experience with ground launch than you are likely
to achieve in your lifetime.

No, Derek, Only YOU disagree. All you are doing is "Bible Pounding"
hoping that by repeating the same thing over and over ever more loudly
people will accept it on faith. I think people are smart enough to
demand proof. I accept nothing on faith. I want engineering
measurements to support each and every detail.

Furthermore you are the sales representative for a particularly bad
winch design seeking to discredit all other approaches any way you
can. If you aren't being paid for this, you should demand to be.