Winch Launch Safety Study

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.

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.

At 16:43 25 March 2009, bildan wrote:

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.

Bill,

I have been involved in a lot of discussion a debate here in Scotland abut
the merits or otherwise of Skylaunch winches and I have been launched by
one and have launched about 8 gliders with one. As you well know because
you have been told this on another forum the auto box is a complete
non-issue. It changes into third during the ground run and stays in fixed
ratio top gear throughout the launch - only exeptionally changing down
under very heavy loading during the main part of the launch. The early
upwards gear changes are undetectable to the glider pilot.

I don't know what you consider to be validated data if not 40 odd winches
over many years of use without problems with controllability related to the
auto box. I can understand your wish to promote the merits of tension
controlled winches but to do so by denigrating a clearly successful
alternative design reveals more about your mindset than the winch in
question. It is a shame that you have no practical experience of the
Skylaunch which in our club trials worked equally successfully for K8s to
Duo Disci

I am pretty sure that the long term future of winching will rest with much
more complex designs but there is none currently available that is proven
by experience in terms of time of use and numbers built. The Hydrostart
is certainly not yet convincing and is very expensive and, correct me if I
am wrong, the US version is not launching yet. Considering the cost of
winches, and the fact that once a club becomes winch orientated then
proven reliabilty is critical, then I would reckon that it will be 5-10
years before it becomes wise to risk the purchase of what is now an
experimental winch design. That is not to say that the the US tension
controlled winch will not be successful from the start - just that it is
better to let others act as the early adopters.

John Galloway

"This discussion always gets the "Safety Nazis" wringing their hands
and wailing every time. ( But never, ever, producing any hard data.)
"

Bill, for once, please, answer the simple question:

What the initial tension, measured in G that you consider ideal on
initial launch? Are you afraid to answer this question that I am now
asking of you for the third time already? You can't complain about
others not providing data (which is not true) if you refuse to even
begin to do so yourself. So put up already.

On 26 Mrz., 02:55, wrote:
What the initial tension, measured in G that you consider ideal on
initial launch? Are you afraid to answer this question that I am now
asking of you for the third time already? You can't complain about
others not providing data (which is not true) if you refuse to even
begin to do so yourself. So put up already.

Ahem... Tension is measured in Newton, not in G. G == acceleration,
or m/s^2. Yes, the forward acceleration of the glider in the initial
takeoff run
can be measured in G, but the connection between the cable tension and
acceleration involves glider and cable mass and wind, so there's no
one-to-one correspondence.

Best regards
--Gerhard Wesp

Can I add that after a very sucessful 6 month trial with a loaned
secondhand Skylaunch winch, Lasham Gliding Society has ordered 2 new ones
that will be arriving shortly.

Lasham is the largest and probably most professional gliding club in the
UK, so its Committee and Management would not have not have entered into
this major financial investment lightly or without considering the
alternatives. I am not a member of the Management or the Committee by the
way.

Can I further add that this winch will smoothly launch anything from
lightweight little vintage single seaters up to big and heavy DG1000Ts,
Duo Discus turbos, and ASH25 turbos. As John says below, the automatic
gearbox changes up into top very early during the ground run and normally
stays there for the rest of the launch. The gearchanges are imperceptable
to the pilot and we have not found a problem with weak links breaking
during the ground run, or at any other stage of the launch for that
matter.

Derek Copeland

P.S. I still want to know how many winch launches Bill Daniels has
actually taken? He demands exact data from others, but won't give out any
himself!

At 00:15 26 March 2009, John Galloway wrote:
At 16:43 25 March 2009, bildan wrote:

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.

Bill,

I have been involved in a lot of discussion a debate here in Scotland
abut
the merits or otherwise of Skylaunch winches and I have been launched by
one and have launched about 8 gliders with one. As you well know
because
you have been told this on another forum the auto box is a complete
non-issue. It changes into third during the ground run and stays in
fixed
ratio top gear throughout the launch - only exeptionally changing down
under very heavy loading during the main part of the launch. The early
upwards gear changes are undetectable to the glider pilot.

I don't know what you consider to be validated data if not 40 odd
winches
over many years of use without problems with controllability related to
the
auto box. I can understand your wish to promote the merits of tension
controlled winches but to do so by denigrating a clearly successful
alternative design reveals more about your mindset than the winch in
question. It is a shame that you have no practical experience of the
Skylaunch which in our club trials worked equally successfully for K8s
to
Duo Disci

I am pretty sure that the long term future of winching will rest with
much
more complex designs but there is none currently available that is
proven
by experience in terms of time of use and numbers built. The Hydrostart
is certainly not yet convincing and is very expensive and, correct me if
I
am wrong, the US version is not launching yet. Considering the cost of
winches, and the fact that once a club becomes winch orientated then
proven reliabilty is critical, then I would reckon that it will be 5-10
years before it becomes wise to risk the purchase of what is now an
experimental winch design. That is not to say that the the US tension
controlled winch will not be successful from the start - just that it is
better to let others act as the early adopters.

John Galloway

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.


Hmmm... Must really go and check the manuals. Or my maths.

IIRC mine (a newer AS model) says 750 or 800daN allowable, my flying
weight is normally around 390kg. So that's close to 2g.
We use 1000daN weak links for the ASK21 (empty 360kg according to AS
homepage), so with two occupants around 540kg. That's also around
1.9g!

Regards
Marcel Dünner

I think you may be missing the point here.
The weak link is to protect the glider airframe from exceeding maximum
loading ie towards the top of the launch, with the cable almost vertical
and the wing loading at its maximum. Using these calculations to determine
the best acceleration at the start of the launch is bad math(s).
The acceleration on the ground should be safe. Too high and the inertia of
the stick and the pilot's hand will cause backward movement, with
self-evident results. Too slow and aileron authority is not achieved
quickly enough to prevent wing drop and possible cartwheel!
Typically aileron authority is present just below the stall speed so the
acceleration should be sufficient to get to that speed before a wing can
drop, say 2 seconds or so. Now do the math(s) for your glider. Typical
stall speeds are below 35 kt (17 metres per second). This gives an
acceleration of less than 1g which will comfortably be tolerated by any
pilot. If continued the acceleration will have the glider fully flying and
high enough to begin the rotation into full climb in another second or
two.
Broken weak links at the start of the ground run are generally due to a
snatched All Out. The launch marshal must ensure that there is no slack in
the cable before giving All Out by waiting for a genuine movement of the
glider. The wing tip holder must move forward with the glider for as long
as possible. The wing tip holder should abort the launch if he or she has
to hold the wings level, they should do so naturally or the wing will drop
on release.

Best wishes

JohnR-K