Does anyone use a tug tow hook that releases automatically whenglider kites?

On Friday, February 21, 2014 11:41:20 AM UTC-6, Steve Leonard wrote:

Kirk, I don't think we want to consider a bridle from the tips. This would require HUGE spar changes, as you could easily impart 500 lbs aft force at both wing tips. This will pretty likely fold the wings aft and make for a very high speed, although only vertical and down capable, tug. Maybe the missle you were hoping to use? :-)

I know that - I was really just throwing out some hare-brained ideas to see what would stick.

My solution is a lot simpler:

1. Near term: Replace ALL Schweizer tow hooks on tow planes with Tost hooks (so you can at least release if you get upset high enough), then provide very specific training to ALL glider pilots on the cause an effect of a tug upset, to include a demo ride in a towplane at the receiving end. And treat all aerotows of gliders with CG hooks as potential kiting accidents and brief accordingly.

2. Long term: some sort of sensor controlled automatic release on tug to eliminate problem, assuming our respective government aviation agencies will agree to their installation. Make it mandatory so the numbers are high enough to drop the price down to something affordable. And remember, it has to not only apply to fixed tow hooks, but also to retractable tow ropes (now how do you measure the forces?).

I still prefer the Bearcat towplane option. Kite away!

Kirk
66

I just had a flash (brain fart) of an automatic release system. You
mechanical guys could probably make something like this work. Please bear
with me...

How about simply inverting a Schweizer release and mounting it on a sturdy
hinge. Then, in addition to the normal release rope, which the tuggie
should be able to release in any attutude, add a second release cable fixed
at the under side of the release, and forward of the hinge, such that, if
the hinge is rotated upward (as in kiting) the fixed cable draws tight and
releases the rope? The length of the fixed cable could be set to open the
release at a preset angle.

Seems simple enough. Please show me the error of my ways.

"kirk.stant" wrote in message
...
On Friday, February 21, 2014 11:41:20 AM UTC-6, Steve Leonard wrote:

Kirk, I don't think we want to consider a bridle from the tips. This
would require HUGE spar changes, as you could easily impart 500 lbs aft
force at both wing tips. This will pretty likely fold the wings aft and
make for a very high speed, although only vertical and down capable, tug.
Maybe the missle you were hoping to use? :-)

I know that - I was really just throwing out some hare-brained ideas to see
what would stick.

My solution is a lot simpler:

1. Near term: Replace ALL Schweizer tow hooks on tow planes with Tost hooks
(so you can at least release if you get upset high enough), then provide
very specific training to ALL glider pilots on the cause an effect of a tug
upset, to include a demo ride in a towplane at the receiving end. And treat
all aerotows of gliders with CG hooks as potential kiting accidents and
brief accordingly.

2. Long term: some sort of sensor controlled automatic release on tug to
eliminate problem, assuming our respective government aviation agencies will
agree to their installation. Make it mandatory so the numbers are high
enough to drop the price down to something affordable. And remember, it has
to not only apply to fixed tow hooks, but also to retractable tow ropes (now
how do you measure the forces?).

I still prefer the Bearcat towplane option. Kite away!

Kirk
66

Dan, that might work if the towplane's attitude was constant. However, during a kiting event, the towplane is being pitched nose down, so the hitch would not likely get activated, as the hitch to surrounding structure angle may not change. I wish it could be that simple, but it isn't. See the previous post about a kiting even where the glider was still in sight in the mirror, even though the towplane was significantly nose down.

Steve

Yes, but that was a fixed hitch. I would think that, as the glider shot
upwards, the hinged release would swivel upward before the tug's nose
started down. Is it because the arm aft of the hinge point would be so
short?

I always preferred mechanical stuff to electrical, but the education was
free so I had to take what was offered.


"Steve Leonard" wrote in message
...
Dan, that might work if the towplane's attitude was constant. However,
during a kiting event, the towplane is being pitched nose down, so the hitch
would not likely get activated, as the hitch to surrounding structure angle
may not change. I wish it could be that simple, but it isn't. See the
previous post about a kiting even where the glider was still in sight in the
mirror, even though the towplane was significantly nose down.

Steve

"Dan Marotta" wrote:

I just had a flash (brain fart) of an automatic release system. You
mechanical guys could probably make something like this work. Please bear
with me...

How about simply inverting a Schweizer release and mounting it on a sturdy
hinge. Then, in addition to the normal release rope, which the tuggie
should be able to release in any attutude, add a second release cable fixed
at the under side of the release, and forward of the hinge, such that, if
the hinge is rotated upward (as in kiting) the fixed cable draws tight and
releases the rope? The length of the fixed cable could be set to open the
release at a preset angle.

Seems simple enough. Please show me the error of my ways.

"kirk.stant" wrote in message
...
On Friday, February 21, 2014 11:41:20 AM UTC-6, Steve Leonard wrote:

Kirk, I don't think we want to consider a bridle from the tips. This
would require HUGE spar changes, as you could easily impart 500 lbs aft
force at both wing tips. This will pretty likely fold the wings aft and
make for a very high speed, although only vertical and down capable, tug.
Maybe the missle you were hoping to use? :-)

I know that - I was really just throwing out some hare-brained ideas to see
what would stick.

My solution is a lot simpler:

1. Near term: Replace ALL Schweizer tow hooks on tow planes with Tost hooks
(so you can at least release if you get upset high enough), then provide
very specific training to ALL glider pilots on the cause an effect of a tug
upset, to include a demo ride in a towplane at the receiving end. And treat
all aerotows of gliders with CG hooks as potential kiting accidents and
brief accordingly.

2. Long term: some sort of sensor controlled automatic release on tug to
eliminate problem, assuming our respective government aviation agencies will
agree to their installation. Make it mandatory so the numbers are high
enough to drop the price down to something affordable. And remember, it has
to not only apply to fixed tow hooks, but also to retractable tow ropes (now
how do you measure the forces?).

I still prefer the Bearcat towplane option. Kite away!

Kirk
66

We had a Schweizer tow hook on one of our tugs years ago, and it made
me suspicious about its performance under load. I decided to test it
by fixing the end of the tow rope round a tree and setting the tug on
full throttle. It was absolutley impossible to release at the tug end,
no matter how hard I pulled on the release cable.

We don't use them any more.

At 18:10 21 February 2014, kirk.stant wrote:
On Friday, February 21, 2014 11:41:20 AM UTC-6, Steve Leonard wrote:

Kirk, I don't think we want to consider a bridle from the tips. This
wou=
ld require HUGE spar changes, as you could easily impart 500 lbs aft
force
=
at both wing tips. This will pretty likely fold the wings aft and make
for=
a very high speed, although only vertical and down capable, tug. Maybe
th=
e missle you were hoping to use? :-)

I know that - I was really just throwing out some hare-brained ideas to
see=
what would stick. =20

My solution is a lot simpler:

1. Near term: Replace ALL Schweizer tow hooks on tow planes with Tost
hooks=
(so you can at least release if you get upset high enough), then provide
v=
ery specific training to ALL glider pilots on the cause an effect of a
tug
=
upset, to include a demo ride in a towplane at the receiving end. And
trea=
t all aerotows of gliders with CG hooks as potential kiting accidents and
b=
rief accordingly.






2. Long term: some sort of sensor controlled automatic release on tug to
el=
iminate problem, assuming our respective government aviation agencies
will
=
agree to their installation. Make it mandatory so the numbers are high
enou=
gh to drop the price down to something affordable. And remember, it has
to=
not only apply to fixed tow hooks, but also to retractable tow ropes
(now
=
how do you measure the forces?).

I still prefer the Bearcat towplane option. Kite away!

Kirk
66



I see no way to do this ,but,
put a pylon on the main spar and tow from the cofg ,shorten the vertical
stabiliser and add some area below the fus then protect the tail feathers
with
struts.
If I remember correctly ski boats went from a rope on the back to center
poles to give more maneuverability .
Try getting that past EASA or the FAA .

On 22/02/2014 05:10, kirk.stant wrote:

My solution is a lot simpler:
....snips
I still prefer the Bearcat towplane option. Kite away!

I liked the Bearcat idea - in fact I like Kirk's whole approach to the
discussion. I put the idea to some old colleagues who flew Sea Furies
who also liked it.

Unfortunately, there is a simpler solution which has been implemented
and proved effective at zero cost but doesn't involve Bearcat
endorsements for tuggies. You don't get kiting if you fly low tow.

Australia's move to low tow was to prevent kiting in an era of low wing
loading gliders in a country with sharp-edged thermals. It's been an
effective solution and it's globally applicable even today. If kiting
is the problem Steve and others make it out to be, low tow will be
adopted immediately. If it's not, this whole discussion could just look
like a giant circle w..k.

Steve?

GC


Kirk 66

In article om GC writes:
On 22/02/2014 05:10, kirk.stant wrote:

My solution is a lot simpler:
...snips
I still prefer the Bearcat towplane option. Kite away!

I liked the Bearcat idea - in fact I like Kirk's whole approach to the
discussion. I put the idea to some old colleagues who flew Sea Furies
who also liked it.

Unfortunately, there is a simpler solution which has been implemented
and proved effective at zero cost but doesn't involve Bearcat
endorsements for tuggies. You don't get kiting if you fly low tow.

You don't get kiting if you fly normal "high" tow behind the towplane,
if you remain in control.

If you don't remain in control, starting from low tow is not going to
make a lot of difference.

If the tug has just lifted off, being in low tow sounds a bit difficult,
but that would be a particularly hazardous time.


As for automatic methods to mitigate the problem, perhaps the solution
is not to modify tow planes, but to modify gliders. If the glider is
in a very high pitch attitude on tow, it might be a good time to automatically
release.

Another modification might be to attach the tow rope to the top of the glider.
This would cause the tow force to pitch the glider down.


Is this more of a problem when folks try to tow a slow glider like a 2-33 at
high speeds?


Alan

On 22/02/2014 16:17, Alan wrote:

...You don't get kiting if you fly normal "high" tow behind the towplane,
if you remain in control.

If you don't remain in control, starting from low tow is not going to
make a lot of difference.

Experience (tens of thousands of aerotows) shows there is an enormous
difference. The inadequate control and time to go from high tow to
kiting is orders of magnitude different from that required to go from
low tow to kiting. In fact, I've never heard of that ever happening.
Even with low time students. Kiting from high tow, however, is
apparently so common as to need a whole new system of electronic
whizzbangery and gallons of bandwidth to stop.

If the tug has just lifted off, being in low tow sounds a bit difficult,
but that would be a particularly hazardous time.

Yes. Liftoff is a time to be wary and we train accordingly.
Nevertheless, all I can say is that low tow has prevented kiting
accidents for many years. But don't take my word for it, keep this
ridiculous discussion going with another screwball idea for pivoting,
autoswivelling, pitch-sensing, stick-following nonsense.

If the issue is serious - as it was in Australia - flying low tow will
solve it. If it isn't - see my previous post.

GC



As for automatic methods to mitigate the problem, perhaps the solution
is not to modify tow planes, but to modify gliders. If the glider is
in a very high pitch attitude on tow, it might be a good time to automatically
release.

Another modification might be to attach the tow rope to the top of the glider.
This would cause the tow force to pitch the glider down.


Is this more of a problem when folks try to tow a slow glider like a 2-33 at
high speeds?

Alan

The time difference to go from low tow to kiting compared to high tow to
kiting is about 1 second - try it at safe altitude. As observed you can't
take-off in low tow so the highest risk time, just after take off when the
combination is accelerating, is exactly the same. The transition from
normal tow to low tow, early in the climb, puts the glider into the
turbulence of the prop-wash which may well cause the, less than one second,
loss of control which is all that is needed to start the kiting. Finally,
low tow on a glider with a C of G hook, leaves the rope wrapped around the
side of the cockpit, not really a good idea and C of G hooks are where the
danger lies.

The cheapest mechanical solution is, fit a nose hook to any glider that is
going to be aerotowed.

My best estimate of low level kiting fatal/serious accident frequency is of
the order of one in a million. "Tens of thousands of aerotows" is not a
big enough sample to draw conclusions.

At 07:58 22 February 2014, GC wrote:
On 22/02/2014 16:17, Alan wrote:

...You don't get kiting if you fly normal "high" tow behind the
towplane,
if you remain in control.

If you don't remain in control, starting from low tow is not going
to
make a lot of difference.

Experience (tens of thousands of aerotows) shows there is an enormous
difference. The inadequate control and time to go from high tow to
kiting is orders of magnitude different from that required to go from
low tow to kiting. In fact, I've never heard of that ever happening.
Even with low time students. Kiting from high tow, however, is
apparently so common as to need a whole new system of electronic
whizzbangery and gallons of bandwidth to stop.

If the tug has just lifted off, being in low tow sounds a bit
difficult,
but that would be a particularly hazardous time.

Yes. Liftoff is a time to be wary and we train accordingly.
Nevertheless, all I can say is that low tow has prevented kiting
accidents for many years. But don't take my word for it, keep this
ridiculous discussion going with another screwball idea for pivoting,
autoswivelling, pitch-sensing, stick-following nonsense.

If the issue is serious - as it was in Australia - flying low tow will
solve it. If it isn't - see my previous post.

GC



As for automatic methods to mitigate the problem, perhaps the
solution
is not to modify tow planes, but to modify gliders. If the glider is
in a very high pitch attitude on tow, it might be a good time to
automatically
release.

Another modification might be to attach the tow rope to the top of
the
glider.
This would cause the tow force to pitch the glider down.


Is this more of a problem when folks try to tow a slow glider like a
2-33 at
high speeds?

Alan