Last weekend our club did some ground launching from a nearby dry
lake. I had two very successful launches using our "cheap" 1800'
rope. With the cheap rope we don't use a parachute on the cable.
When I tried to launch with the 3000' spectra rope, equipped with a
parachute, the chute at least partially opened when the glider was
going around 40 knots, and depsite full right rudder, the glider
ground looped to the left. All the pictures I've ever seen
(admittedly very few) of the cable chute used for winch or vehicle
tows seem to show the chute' is completely 'closed' when the rope is
still attached to the glider. I'm sure pilot error had a part in this,
but it really seemed that when the chute opened, I lost what little
rudder authority I had. It also occurred to me that the
Speed Astir verticle stab and rudder is one of the shortest
(vertically) around, and that may have been a contributing factor.
The dust cloud was quite impressive!
Jim

What's the distance between the crown of the parachute and the
attachment to the glider? Should be at least 30 feet.


Dan

On Oct 29, 10:10 am, Dan G > wrote:
> What's the distance between the crown of the parachute and the
> attachment to the glider? Should be at least 30 feet.
>
> Dan

Seemed more like 10 or 15, but certainly less than 30.

wrote:

>> What's the distance between the crown of the parachute and the
>> attachment to the glider? Should be at least 30 feet.
>
> Seemed more like 10 or 15, but certainly less than 30.

I winch launch a lot, but have never seen 30. 10 to 15 seems reasonable
to me.

On Oct 29, 7:07 pm, John Smith > wrote:
> I winch launch a lot, but have never seen 30. 10 to 15 seems reasonable
> to me.

That's the general recommendation from Tost (or rather, 10m is). We
used to use less but now use the correct length - it's a lot more
comfortable.


Dan

On Oct 29, 3:30 pm, Dan G > wrote:
> On Oct 29, 7:07 pm, John Smith > wrote:
>
> > I winch launch a lot, but have never seen 30. 10 to 15 seems reasonable
> > to me.
>
> That's the general recommendation from Tost (or rather, 10m is). We
> used to use less but now use the correct length - it's a lot more
> comfortable.
>
> Dan

Shouldn't the 'chute stay closed though? I'm sure I wasn't clear, but
that was the root of my question.

On Oct 29, 10:35 pm, wrote:
> Shouldn't the 'chute stay closed though? I'm sure I wasn't clear, but
> that was the root of my question.

Well yeah, it should! The tension through the shroud lines should keep
it closed, but if that's too low the natural tendency for the chute to
inflate overcomes it. That could either be down to a poor design -
I've seen several parachutes that seem to inflate whatever - or
perhaps down to less-than-perfect pilot/winch/car driver technique.


Dan

The chute will open as soon as the force on the rope gets too low. On a
winch launch, this is typically the case if the pilot "follows the rope"
instead of pulling gently in order to rotate into initial climb attitude.

Bert

> wrote in message
ps.com...
>
> Shouldn't the 'chute stay closed though? I'm sure I wasn't clear, but
> that was the root of my question.
>

On Oct 30, 1:49 am, "Bert Willing" <bw_no_spam_ple...@tango-
whisky.com> wrote:
> The chute will open as soon as the force on the rope gets too low. On a
> winch launch, this is typically the case if the pilot "follows the rope"
> instead of pulling gently in order to rotate into initial climb attitude.
>
> Bert
>
On this (aborted) launch, I was still rolling, both wheels on the
ground. I noted the chute opening in front of other gliders too,
while on the ground. I'd had no problems launching with our non-
chuted poly rope.

On Oct 30, 12:42 pm, wrote:
> On Oct 30, 1:49 am, "Bert Willing" <bw_no_spam_ple...@tango-> On this (aborted) launch, I was still rolling, both wheels on the
> ground. I noted the chute opening in front of other gliders too,
> while on the ground. I'd had no problems launching with our non-
> chuted poly rope.

How springy is 3000 feet of spectra? I imagine that would be more of
a factor for auto tow than winch. I'm speculating that the problem
with the spectra launch is not the parachute itself but the dynamics
of the rope tension. The result may be strongly dependant on how the
tow vehicle accelerarates to nominal launch speed.

Andy

Andy wrote:
> On Oct 30, 12:42 pm, wrote:
>> On Oct 30, 1:49 am, "Bert Willing" <bw_no_spam_ple...@tango-> On this (aborted) launch, I was still rolling, both wheels on the
>> ground. I noted the chute opening in front of other gliders too,
>> while on the ground. I'd had no problems launching with our non-
>> chuted poly rope.
>
> How springy is 3000 feet of spectra? I imagine that would be more of
> a factor for auto tow than winch. I'm speculating that the problem
> with the spectra launch is not the parachute itself but the dynamics
> of the rope tension. The result may be strongly dependant on how the
> tow vehicle accelerarates to nominal launch speed.
>
> Andy
>
That makes senses. My guess would be that the tow vehicle changed gear
and thus briefly reduced power, which would probably be enough to allow
the chute to start to open. Some automatic gearboxes have quite a
deliberate gear change, enough to reduce the tension on the rope. If
there's a lot of spring in the rope a gear change could set up some
brief oscillation, enough to allow the chute to flap around.

Did it close again, or remain open? If the latter, either the tow
vehicle wasn't pulling or there's something very odd about the chute design.

On Oct 31, 3:40 am, Chris Reed > wrote:
> Andy wrote:
> > On Oct 30, 12:42 pm, wrote:
> >> On Oct 30, 1:49 am, "Bert Willing" <bw_no_spam_ple...@tango-> On this (aborted) launch, I was still rolling, both wheels on the
> >> ground. I noted the chute opening in front of other gliders too,
> >> while on the ground. I'd had no problems launching with our non-
> >> chuted poly rope.
>
> > How springy is 3000 feet of spectra? I imagine that would be more of
> > a factor for auto tow than winch. I'm speculating that the problem
> > with the spectra launch is not the parachute itself but the dynamics
> > of the rope tension. The result may be strongly dependant on how the
> > tow vehicle accelerarates to nominal launch speed.
>
> > Andy
>
> That makes senses. My guess would be that the tow vehicle changed gear
> and thus briefly reduced power, which would probably be enough to allow
> the chute to start to open. Some automatic gearboxes have quite a
> deliberate gear change, enough to reduce the tension on the rope. If
> there's a lot of spring in the rope a gear change could set up some
> brief oscillation, enough to allow the chute to flap around.
>
> Did it close again, or remain open? If the latter, either the tow
> vehicle wasn't pulling or there's something very odd about the chute design.

The chute stayed open. (at least until I was too sideways to see it!)

I would like to add some more facts to help determine the problem I am the
owner of the tow vehicle spectra line and chute. The chute is a toast
cross- panel and is 1450 mm diameter. It came with the minimum 2 m
connecting cable and 3 m safety cable. The chute kept fully opening the
first day I used it. You can see it in the video that I have on my web
site. http://www.caglesonline.com/video/autotows.wmv Since that day I have
increased the 2 m connecting cable to 4 m. It does a better job as you can
see in the next video taking the same day and place that jims glider ground
looped. http://www.caglesonline.com/video/07fallroachlake.wmv The tow
vehicle has skid control on it witch means if the tires breaks traction the
computer automatically backs of power to get traction back. Since the first
day towing with it we have figured out how to disable it. I don't know for
positive if it was disabled during the tow in question because there was a
new driver at time. Unless the ignition was turned off then it should of
still been disabled. There was two more contributing factors 1 allot of the
dry lake bed was soft. The tow vehicle was breaking the crest and in some
places leaving 3 inch deep tracts. 2 the winds was variable and had a
slight till wind about half of the day. Some times the tow vehicle was
doing 65 to 75 all the way till some gliders was releasing. I think more
then pilot error or vehicle driver error I believe it was a combination of
several factors butt I would be interested in other thoughts.
John



> wrote in message
ups.com...
> On Oct 31, 3:40 am, Chris Reed > wrote:
>> Andy wrote:
>> > On Oct 30, 12:42 pm, wrote:
>> >> On Oct 30, 1:49 am, "Bert Willing" <bw_no_spam_ple...@tango-> On this
>> >> (aborted) launch, I was still rolling, both wheels on the
>> >> ground. I noted the chute opening in front of other gliders too,
>> >> while on the ground. I'd had no problems launching with our non-
>> >> chuted poly rope.
>>
>> > How springy is 3000 feet of spectra? I imagine that would be more of
>> > a factor for auto tow than winch. I'm speculating that the problem
>> > with the spectra launch is not the parachute itself but the dynamics
>> > of the rope tension. The result may be strongly dependant on how the
>> > tow vehicle accelerarates to nominal launch speed.
>>
>> > Andy
>>
>> That makes senses. My guess would be that the tow vehicle changed gear
>> and thus briefly reduced power, which would probably be enough to allow
>> the chute to start to open. Some automatic gearboxes have quite a
>> deliberate gear change, enough to reduce the tension on the rope. If
>> there's a lot of spring in the rope a gear change could set up some
>> brief oscillation, enough to allow the chute to flap around.
>>
>> Did it close again, or remain open? If the latter, either the tow
>> vehicle wasn't pulling or there's something very odd about the chute
>> design.
>
> The chute stayed open. (at least until I was too sideways to see it!)
>

On Nov 2, 10:59 am, "John Cagle" > wrote:
>Some times the tow vehicle was
>doing 65 to 75 all the way till some gliders was releasing.

I'm surprised that the tow vehicle was going that fast. Did the
gliders ever get into a normal ground launch climb attitude?

What vehicle speeds are other auto tow users seeing on calm wind days?

Andy

I owned a Speedastir. Aileron control was never great on takeoff. If a
wing goes down there was every chance it would stay there. Picking up
a wing with ailerons was a bad idea. Was more responsive to rudder.
If the wing hits the ground release immediately unless you are VERY
sure you can get it back up.
Cheers
Mark.

Cheers
Mark

On Nov 3, 5:36 am, Andy > wrote:
> On Nov 2, 10:59 am, "John Cagle" > wrote:
>
> >Some times the tow vehicle was
> >doing 65 to 75 all the way till some gliders was releasing.
>
> I'm surprised that the tow vehicle was going that fast. Did the
> gliders ever get into a normal ground launch climb attitude?
>
> What vehicle speeds are other auto tow users seeing on calm wind days?
>
> Andy

If a wing drops to the point where you are sure it will hit the ground release
immediately. If you start a ground loop with a winch line attached the results
are very fast, and frequently result in a lot of damage to the glider and its
contents...

Fish wrote:
> I owned a Speedastir. Aileron control was never great on takeoff. If a
> wing goes down there was every chance it would stay there. Picking up
> a wing with ailerons was a bad idea. Was more responsive to rudder.
> If the wing hits the ground release immediately unless you are VERY
> sure you can get it back up.
> Cheers
> Mark.
>
> Cheers
> Mark
>
> On Nov 3, 5:36 am, Andy > wrote:
>> On Nov 2, 10:59 am, "John Cagle" > wrote:
>>
>>> Some times the tow vehicle was
>>> doing 65 to 75 all the way till some gliders was releasing.
>> I'm surprised that the tow vehicle was going that fast. Did the
>> gliders ever get into a normal ground launch climb attitude?
>>
>> What vehicle speeds are other auto tow users seeing on calm wind days?
>>
>> Andy
>
>

At 18:01 02 November 2007, John Cagle wrote:
> The chute kept fully opening the
>first day I used it. You can see it in the video that
>I have on my web
>site. http://www.caglesonline.com/video/autotows.wmv
> Since that day I have
>increased the 2 m connecting cable to 4 m. It does
>a better job as you can
>see in the next video taking the same day and place
>that jims glider ground
>looped. http://www.caglesonline.com/video/07fallroachlake.wmv

It looks from the videos as if the towing cable is
split in four and looped over the chute so it is trying
to keep it closed only because of the tension in the
cable. I think the chute is almost bound to open with
this arrangement. In all the ground launch cables I
have seen and used - for both winch and auto tow -
the strop attached to the glider goes directly to the
apex of the parachute so that the chute itself is part
of the cable and is kept closed by its own tension.

And 65 or 70 mph seems far too fast. At any reasonable
launch angle the glider airspeed is considerably more
than the tow car speed so for a good launch at say
55 or 60 kt into a light wind, the car should be doing
no more than 30 or 40 mph.

Neil

I agree about the chute.

All the winch launching parachutes I've seen (and the principle should
be the same) are constructed roughly as follows:

1. Take four squares of material (lozenges might be better, and possibly
some curvature in some of the sides - you'd need to experiment).

2. Attach one corner of each to the other four to form the apex of the
chute. The cable to the glider goes to this apex.

3. Sew the squares together along (for each) the two sides which meet at
the apex (think jellyfish?)

4. Connect the four free corners by tapes or ropes about 3 or 4 feet
long to the cable connected to the tow car. Most chutes I've seen have a
heavy duty tape stiched from the apex of each square to the free corner,
then continuing to form the junction to the tow car cable.

Chutes like this stay closed so long as the cable is under more than
minimal tension.

You'd need to experiment - maybe start with four handkerchiefs and some
pins to see if my description translates into something usable?


Neil MacLean wrote:
> At 18:01 02 November 2007, John Cagle wrote:
>> The chute kept fully opening the
>> first day I used it. You can see it in the video that
>> I have on my web
>> site. http://www.caglesonline.com/video/autotows.wmv
>> Since that day I have
>> increased the 2 m connecting cable to 4 m. It does
>> a better job as you can
>> see in the next video taking the same day and place
>> that jims glider ground
>> looped. http://www.caglesonline.com/video/07fallroachlake.wmv
>
> It looks from the videos as if the towing cable is
> split in four and looped over the chute so it is trying
> to keep it closed only because of the tension in the
> cable. I think the chute is almost bound to open with
> this arrangement. In all the ground launch cables I
> have seen and used - for both winch and auto tow -
> the strop attached to the glider goes directly to the
> apex of the parachute so that the chute itself is part
> of the cable and is kept closed by its own tension.
>
> And 65 or 70 mph seems far too fast. At any reasonable
> launch angle the glider airspeed is considerably more
> than the tow car speed so for a good launch at say
> 55 or 60 kt into a light wind, the car should be doing
> no more than 30 or 40 mph.
>
> Neil
>
>

Hi John

On Fri, 02 Nov 2007 10:59:32 -0700, John Cagle wrote:

> I would like to add some more facts to help determine the problem I am the
> owner of the tow vehicle spectra line and chute. The chute is a toast
> cross- panel and is 1450 mm diameter. It came with the minimum 2 m
> connecting cable and 3 m safety cable. The chute kept fully opening the
> first day I used it. You can see it in the video that I have on my web
> site. http://www.caglesonline.com/video/autotows.wmv Since that day I have
> increased the 2 m connecting cable to 4 m. It does a better job as you can
> see in the next video taking the same day and place that jims glider ground
> looped. http://www.caglesonline.com/video/07fallroachlake.wmv The tow
> vehicle has skid control on it witch means if the tires breaks traction the
> computer automatically backs of power to get traction back. Since the first
> day towing with it we have figured out how to disable it. I don't know for
> positive if it was disabled during the tow in question because there was a
> new driver at time. Unless the ignition was turned off then it should of
> still been disabled. There was two more contributing factors 1 allot of the
> dry lake bed was soft. The tow vehicle was breaking the crest and in some
> places leaving 3 inch deep tracts. 2 the winds was variable and had a
> slight till wind about half of the day. Some times the tow vehicle was
> doing 65 to 75 all the way till some gliders was releasing. I think more
> then pilot error or vehicle driver error I believe it was a combination of
> several factors butt I would be interested in other thoughts.
> John

My experience is with winching, not auto tow, but a few things we have
learnt along the way. (We have also used a Tost cross panel chute, and a
number of similar designs.):

- The only thing that keeps the chute closed during launch is the cable
tension. This is determined by both the pilot and the winch driver. A
smooth constant acceleration on the part of the winch driver during the
ground run, followed by a smooth rotation into a steady climb on the part
of the pilot keeps the chute closed. Maybe your acceleration is just too
slow to keep enough tension to keep the chute closed. As a comment, we use
these chutes so that the winch driver can control the cable after release
and wind the cable to a point where the chute lands close to the runway.
With auto-tow your requirements may be different and a large chute may be
unnecessary.

- You must have a sufficient distance between the glider and the chute to
eliminate the possibility of the glider overrunning the chute and it
getting snagged in the glider. This could result in the glider being
launched for example, by the tail skid - which has resulted in fatal
accidents in the past. The Soaring Society of South Africa recommends 15m
to 25m between the rings and the chute (some other countries use a little
less but follow the same principle). The additional length also helps
prevent stones picked up by the chute during the ground run from hitting
the glider canopy and leading edge.

- You must stiffen the section of cable immediately in front of the release
rings with a hose pipe or similar. This is to prevent it from getting
picked up in the main wheel or similar resulting during an overrun. This
would result in the glider getting launched with no means of releasing the
cable - also a cause of fatal accidents in the past. The Souring Society of
South Africa recommend a minimum 15m length of stiffened cable (other
countries use a little less).

- You should have a means of releasing the cable from the tow car in case
of a hang up emergency as described above. The driver should also carry
a sharp knife, as a backup to cut the cable in the event of the release
mechanism failing to operate.

- The British Gliding Association recommends that a winch launch be
commenced with the pilots hand holding the release knob. If the wing
touches the ground the pilot should release immediately. If the wing tip
gets caught on the ground a "cart wheel" accident can occur very quickly,
often with serious injury or fatality.

Winching is conducted safely on a large scale in many parts of the
world. The above lessons have already been learnt the hard way and you do
not want to go through the same learning curve again!

Have fun.


Ian

On Nov 2, 10:36 am, Andy > wrote:
> On Nov 2, 10:59 am, "John Cagle" > wrote:
>
> >Some times the tow vehicle was
> >doing 65 to 75 all the way till some gliders was releasing.
>
> I'm surprised that the tow vehicle was going that fast. Did the
> gliders ever get into a normal ground launch climb attitude?
>
> What vehicle speeds are other auto tow users seeing on calm wind days?
>
> Andy

The truck was accelerating to 60ish, then easing off the gas when the
glider achieved climbing attitude. I was consistantly climbing at 60
- 62 knots at close to 45 degrees. On the 1800' poly rope I got 1200'
altitude.

Jim,
My experience is with winch launching. Have done it for many years in
Europe.
By looking at the video, the climb angle is way too shallow, at least
of it were a winch launch. The chute opens while following the rope
after initial lift off.

Following the rope is never a good idea unless you're going to
release. At least with winches.

Right after lift off, one should start climbing gradually and increase
the angle once more than 100ft. That way the rope tension stays firm.

If the air speed should become uncomfortably slow or remain too slow,
you can release safely at 100ft or more. Height = safety - even when
slow. So you always want to get some air under the wings and keep the
rope tension up.

By pushing the nose over even at low airspeeds and then releasing, you
won't stall and land straight ahead and see why the speed was too low.

But following the rope on initial launch for more than 2-3 seconds
because the speed isn't high enough, is not proper technique, at least
not on the winch and I would say probably on a car tow as well.

Either release immediately and abort or gently climb out for the first
100ft and then release if speed remain too low for comfort.

Ground launch requires very quick reaction without any hesitation.
There for it requires a plan of action firmly in place ahead of time
that needs to be followed during launch. If the pilot is prepared
properly and knows how to react given the situation, I think it is
much safer than aero tow.

Once you're over 100ft, nothing much can go wrong.
Tom

Even on the second video, the pilot is heard saying "almost level
attitude" on initial climb out. That is totally wrong technique and
the chute is opening in front of him as a result. That as we saw, is
dangerous.

He would need to climb out a little steeper for the first 100ft and
all would be OK.

Even on winches the chute can open for split second sometimes, but as
the pilot pulls, they close back up again.

Also the climb in the second video is not done very smooth. Proper
technique is to gradually start easing back on the stick and leveling
off as maximum altitude is reached. You will know this because the
sailplane will start rocking back and forth, pitching the nose up and
down, if you don't ease back and the angle remains too steep. The
plane does not like to be dragged through the air at a high angle of
attack, which is what happens when the angle is too steep - regardless
of the airspeed.

Suddenly leveling out and releasing means the maximum altitude was not
reached. Either they leveled off too soon or too late.

Then again, maybe the car had to stop due to a limited ground run.
Then the release technique used in the second video is understandable.
Otherwise not.

This thread was started by someone asking fairly basic
questions about ground launching, and from the responses
doesn't seem to have much (any?) experience of it.

It's been said several times before, but ground launching
is a potentially dangerous business, and before trying
it one should go to an operation which is experienced
in it. You would learn about how the equipment is put
together, how the car or winch is operated and how
the glider should be flown. Also how to cope with potential
problems when things go wrong - low level cable breaks,
wing dropping, use of weak links, just for example.
Life is too short to learn all these things by making
your own mistakes - and it could become even shorter.

In any case, I haven't looked at the rules for my US
glider pilot's licence for a while, but I have a feeling
that it only allows me to use the launch methods which
I am qualified for (which does include winch and autotow.)
If you haven't got a ground launch qualification don't
you need at least an instructor's sign-off, which would
need at least some training in how to do it properly?

Neil

On Nov 7, 9:57 am, Neil MacLean >
wrote:
> This thread was started by someone asking fairly basic
> questions about ground launching, and from the responses
> doesn't seem to have much (any?) experience of it.
>
> It's been said several times before, but ground launching
> is a potentially dangerous business, and before trying
> it one should go to an operation which is experienced
> in it. You would learn about how the equipment is put
> together, how the car or winch is operated and how
> the glider should be flown. Also how to cope with potential
> problems when things go wrong - low level cable breaks,
> wing dropping, use of weak links, just for example.
> Life is too short to learn all these things by making
> your own mistakes - and it could become even shorter.
>
> In any case, I haven't looked at the rules for my US
> glider pilot's licence for a while, but I have a feeling
> that it only allows me to use the launch methods which
> I am qualified for (which does include winch and autotow.)
> If you haven't got a ground launch qualification don't
> you need at least an instructor's sign-off, which would
> need at least some training in how to do it properly?
>
> Neil

Yup, signed off 3 years ago. AFTER not only training, but
experiencing the following WITH an instructor:
1. overspeed requiring release at around 150 feet.
2. Rope break at around 200 feet
3. Rope break at 12 feet
4. Succesful climb to 1100 feet (SGS2-33A on 1800' Poly rope)
Since, I've taken some auto-tows in the club 1-26, and several in my
Speed Astir.
The tow in question was my first behind a rope with a chute.

OK, training done, my apologies if I misinterpreted
from the first posting where you were coming from.
But I still think there might be something wrong with
the parachute setup - it shouldn't open under the normal
tension of the tow.
And 65 to 75 mph does seem too fast for the tow car.
I drove tow cars for many years before we changed over
to a winch, and I don't recall ever going as fast as
that even in no wind conditions.
I hope you sort out the problem.

Neil

On Nov 10, 9:51 am, Neil MacLean
> wrote:
> OK, training done, my apologies if I misinterpreted
> from the first posting where you were coming from.
> But I still think there might be something wrong with
> the parachute setup - it shouldn't open under the normal
> tension of the tow.
> And 65 to 75 mph does seem too fast for the tow car.
> I drove tow cars for many years before we changed over
> to a winch, and I don't recall ever going as fast as
> that even in no wind conditions.
> I hope you sort out the problem.
>
> Neil

It will have to wait until our next dry lake weekend. The BLM insists
on 6 months lead time to obtain a 'use permit' for the dry lake.

I agree with Neil, I think there is a problem with
the chute set up. I got my sign off a long time ago
on auto tow and we didn't use a chute. I have more
recently become somewhat active in the Prescott Soaring
Society where we winch launch exclusively, and I am
in no means an expert at this but, our chute systems
all have at least 8 gore lines. I seem to remember
that yours only had four. I would think that the more
gore lines would allow less of the chute to to be exposed
to the relative wind when under tension, each line
holding in less of the chute. Just a thought.


At 06:18 12 November 2007,
wrote:
>On Nov 10, 9:51 am, Neil MacLean
> wrote:
>> OK, training done, my apologies if I misinterpreted
>> from the first posting where you were coming from.
>> But I still think there might be something wrong with
>> the parachute setup - it shouldn't open under the
>>normal
>> tension of the tow.
>> And 65 to 75 mph does seem too fast for the tow car.
>> I drove tow cars for many years before we changed
>>over
>> to a winch, and I don't recall ever going as fast
>>as
>> that even in no wind conditions.
>> I hope you sort out the problem.
>>
>> Neil
>
>It will have to wait until our next dry lake weekend.
>The BLM insists
>on 6 months lead time to obtain a 'use permit' for
>the dry lake.
>
>