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

On Tuesday, 18 February 2014 12:07:20 UTC+2, Chris Rollings wrote:
That might work but I suspect it would be impossible, in the real World, to
get a sufficiently high degree of reliability that we did not get more
accidents from innocent gliders be jettisoned at low altitudes than we
currently get from kiting accidents.

Hi Chris

This is not a personal attack - I appreciate your valuable input but ...

With modern technology we can reliably detect pitch, roll, acceleration of a tug plane IMO.
e.g. My Note 2 has a magnetometer, electronic gyros, accelerometers, barometer, and GPS. I downloaded an artificial horizon app for my Android phone and when it blends all the sensor data you get a very reliable pitch and roll output.
It doesn't even experience gyro drift because it is able to compensate using the magnetometer to sense gravity.

Another example are all the Ardupilot projects.
If they are capable of flying DIY autonomous drones around for under $300 then I think the technology is available and good enough for us to use.

Even so, I'd rather have a 1 in 1000 chance of accidentally being dumped than kill a tug pilot and myself through a momentary lapse of judgement/attention.

I happen to fly at the club in South Africa which had the low altitude, tug upset on Sunday 16th Feb 2014, resulting in the death of the tug pilot in a Cessna 182A.
I simply refuse to believe that we can fly to the moon and back but can't devise a reliable automatic tow release mechanism.
How many more tug pilots around the world do we have to kill before we devise a mechanism which works?

To detect a tug upset reliably I think one would only need:
1. To sense the tug elevator at the back stop +
2. The pitch of the tug (say 20 degrees down and increasing) +
3. The load on the rope (glider still attached).
I can't imagine the above being present in any normal operational situation.

Paul

At 07:23 19 February 2014, Surge wrote:
On Tuesday, 18 February 2014 12:07:20 UTC+2, Chris Rollings wrote:
That might work but I suspect it would be impossible, in the real
World,
to
get a sufficiently high degree of reliability that we did not get more
accidents from innocent gliders be jettisoned at low altitudes than we
currently get from kiting accidents.

Hi Chris

This is not a personal attack - I appreciate your valuable input but ...

With modern technology we can reliably detect pitch, roll, acceleration
of
a tug plane IMO.
e.g. My Note 2 has a magnetometer, electronic gyros, accelerometers,
barometer, and GPS. I downloaded an artificial horizon app for my Android
phone and when it blends all the sensor data you get a very reliable
pitch
and roll output.
It doesn't even experience gyro drift because it is able to compensate
using the magnetometer to sense gravity.

Another example are all the Ardupilot projects.
If they are capable of flying DIY autonomous drones around for under $300
then I think the technology is available and good enough for us to use.

Even so, I'd rather have a 1 in 1000 chance of accidentally being dumped
than kill a tug pilot and myself through a momentary lapse of
judgement/attention.

I happen to fly at the club in South Africa which had the low altitude,
tug
upset on Sunday 16th Feb 2014, resulting in the death of the tug pilot in
a
Cessna 182A.
I simply refuse to believe that we can fly to the moon and back but can't
devise a reliable automatic tow release mechanism.
How many more tug pilots around the world do we have to kill before we
devise a mechanism which works?

To detect a tug upset reliably I think one would only need:
1. To sense the tug elevator at the back stop +
2. The pitch of the tug (say 20 degrees down and increasing) +
3. The load on the rope (glider still attached).
I can't imagine the above being present in any normal operational
situation.

Paul


Paul, by the time your items 1, 2 & 3 are present it is probably too late,
the tail-plane is almost certainly stalled and even if the glider were
jettisoned at that instant, the tow-plane would probably still pitch down
another 40 or 50 degrees before recovery (I say probably, could someone
please test it with a camera plane alongside at safe altitude, done
deliberately it should be possible to pull the release at exactly the right
moment - might take three or four goes to get on exactly right).

The thing that is constantly under-estimated by those that haven't
experienced it is how quickly it all happens. LESS THAN 3 SECONDS FROM ALL
NORMAL TO ALL OVER. People take at least that long to react to something
unexpected unless it is something they have practiced frequently, certainly
not the case in kiting incidents.

Chris has hit the nail on the head with his testing and reporting. When it goes wrong, it goes wrong fast. Faster than you can possibly react. We can try all we want to teach how to not do it, but it will sometimes happen. Why not come up with a system that will minimize the risk to the towpilot? I think we have concluded that for now, we cannot eliminate it without creating other significant problems.

If we are considering an automatic system, why wait to full nose up elevator and nose down 20 degrees? As Chris said, if you are there, you are probably doomed. If the nose is down 10 degrees (or maybe even 5?) and the elevator is half way to full up, something is wrong. Would you agree? On tow, elevator is up, nose is up. On descent, elevator is down, nose is down.

Why not develop and test a parallel releasing system that has inputs from a gyro for pitch attitude and a simple sensor for elevator position? Test at safe altitude, as Chris and company did. I know this is not going to prevent kiting, but if we can reduce the risk when it happens and maybe not even add bad failure modes, it should be well worth the effort.

Just my thoughts.

Steve Leonard

At 17:41 17 February 2014, SF wrote:
If this was an industrial control problem. I would try two things.
1: Mount a Tost CG release on the tow plane upside down and at an angle
whe=
re the upwards angle of the tow rope would initiate a back release. The
an=
gle required, reliability, tendency for unintended operation,and whether
or=
not this would actually work, to be determined by testing. Based on
somet=
hing like this that was attempted and reported on here earlier, I have a
lo=
w confidence in this scheme working out.

We actually tried exactly that as our first attempt (can't remember now if
it was a Tost or Ottfur Hook we used, but they are much the same anyway).
It didn't work because, as I said, the "kiting" departure is caused by the
upward component of the pull on the rope, not the upward angle. If a light
weight single seat glider is flying in steady flight behind the tow-plane
at about 60 knots the tension in the rope is only a few 10's of pounds. If
the glider is pitched 45 degrees nose up the tension in the rope is about
700 - 900 lbs. In the first case, the glider being high enough that the
rope angle is 30 degrees upwards is easily containable by the tow-pilot, in
the second case he is pitched 70 degrees nose down in less than 2 seconds.

2: Using a TOST release, add an electric solenoid activation device
somewhe=
re in the cable run to the release. The solenoid could be activated by a
"=
full back stick" limit switch and a short time delay circuit on the tow
pla=
ne, the normal manual pull handle in the cockpit, or a switch on the
stick.=

"...A short time delay circuit...." The whole sequence from everything
normal, to tow-plane 70 degrees nose down and destined to lose about 400
feet, takes less than 3 seconds.

On most tail-draggers (= many/most tow-planes currently in use), it's
normal to bring the stick fully back shortly after touch-down, be tedious
to have to go and find the rope after every tow.

Again, testing would have to be done to confirm that this scheme would
ac=
tually work.
I have no idea how any of this could be accomplished given it's an
airplane=
and the FAA is involved. Their requirements are baffling to someone
that
=
does not live in that world.

Ultimately, taking the human element out of the equation could prove
imposs=
ible. The cure being worse that the disease is also a real possibility
due=
to unintended consequences. However we have always done it this way,
isn't=
a good answer either. =20

Another fatality on Sunday in South Africa - with a Cessna glider tug crashing just on the initial part of the flight. Eye witnesses seem to have seen the glider (Ventus CM) kite and force the tow plane into the ground. A very experienced tow pilot and gliding instructor will be sorely missed by the gliding community.

Here is the link to the active thread on the AvCom site regarding this incident including the eye witness account. Registration on the site will be required to view the topic. http://www.avcom.co.za/phpBB3/viewto...p?f=9&t=130916

Whether an automatic release would have saved the plane and pilot can be speculated but its certainly worth investigating if it will save lives from being lost in this type of accident.

Clinton

Not an 'auto release', but some info from this document :

http://www.glidingmagazine.com/pdfs/...20Rollings.pdf

"That of course is the reason that attempts to produce a hook that released
if an certain angle was
exceeded were unsuccessful. The quite small angle needed to trigger
the“Kiting�when the
glider is pitched significantly nose-up is not much greater than the amount
of out of position
commonly experienced in turbulent conditions. We did build an experimental
hook and tried it,
but, set to an angle that prevented“Kiting�it occasionally dumped an
innocent glider in
turbulence, and set to an angle that prevented that, it didn’t prevent
the“Kiting�. What was
needed was a hook that responded to the vertical component of the load, not
the angle at which it
was applied, and that problem we decided was beyond us (at least in a form
robust and foolproof
enough to be attached to the rear end of a tow-plane)"

Solved by

"We solved that problem on our tow-planes by replacing the bolt that the
hook latches onto with a
small roller bearing. So far as I know, no one has tested the Schweitzer
hook as fitted to a glider,
but I would not be surprised if it exhibited the same characteristics at
high loads."
http://www.facebook.com/KranskopGliding

That didn't solve the Kiting problem, merely made it probable that the
release would still be able to be operated when the rope was under very
high tension. It remained the opinion of all involved that in a real,
accidental Kiting incident, there was effectively no chance that either
tow-pilot or glider pilot would re-act in time to release before it was too
late.

At 08:17 18 February 2014, Pieter Oosthuizen wrote:
Not an 'auto release', but some info from this document :

http://www.glidingmagazine.com/pdfs/...20Rollings.pdf

"That of course is the reason that attempts to produce a hook that
released
if an certain angle was
exceeded were unsuccessful. The quite small angle needed to trigger
the“Kiting�when the
glider is pitched significantly nose-up is not much greater than the
amount
of out of position
commonly experienced in turbulent conditions. We did build an
experimental
hook and tried it,
but, set to an angle that prevented“Kiting�it occasionally dumped an
innocent glider in
turbulence, and set to an angle that prevented that, it didn’t prevent
the“Kiting�. What was
needed was a hook that responded to the vertical component of the load,
not
the angle at which it
was applied, and that problem we decided was beyond us (at least in a
form
robust and foolproof
enough to be attached to the rear end of a tow-plane)"

Solved by

"We solved that problem on our tow-planes by replacing the bolt that the
hook latches onto with a
small roller bearing. So far as I know, no one has tested the Schweitzer
hook as fitted to a glider,
but I would not be surprised if it exhibited the same characteristics at
high loads."
http://www.facebook.com/KranskopGliding

Thanks Chris - appreciate your comments!

Apologies if I interpreted it incorrectly.

PO


At 10:30 18 February 2014, Chris Rollings wrote:
That didn't solve the Kiting problem, merely made it probable that the
release would still be able to be operated when the rope was under very
high tension. It remained the opinion of all involved that in a real,
accidental Kiting incident, there was effectively no chance that either
tow-pilot or glider pilot would re-act in time to release before it was
too
late.

At 08:17 18 February 2014, Pieter Oosthuizen wrote:
Not an 'auto release', but some info from this document :

http://www.glidingmagazine.com/pdfs/...20Rollings.pdf

"That of course is the reason that attempts to produce a hook that
released
if an certain angle was
exceeded were unsuccessful. The quite small angle needed to trigger
the“Kiting�when the
glider is pitched significantly nose-up is not much greater than the
amount
of out of position
commonly experienced in turbulent conditions. We did build an
experimental
hook and tried it,
but, set to an angle that prevented“Kiting�it occasionally dumped an
innocent glider in
turbulence, and set to an angle that prevented that, it didn’t prevent
the“Kiting�. What was
needed was a hook that responded to the vertical component of the load,
not
the angle at which it
was applied, and that problem we decided was beyond us (at least in a
form
robust and foolproof
enough to be attached to the rear end of a tow-plane)"

Solved by

"We solved that problem on our tow-planes by replacing the bolt that the
hook latches onto with a
small roller bearing. So far as I know, no one has tested the Schweitzer
hook as fitted to a glider,
but I would not be surprised if it exhibited the same characteristics at
high loads."
http://www.facebook.com/KranskopGliding

At 11:54 18 February 2014, Pieter Oosthuizen wrote:
Thanks Chris - appreciate your comments!

Apologies if I interpreted it incorrectly.

PO

I think Chris has made it pretty clear that the fitting of an automatic
system is not at this time a practical solution. I think he has also made
it pretty clear that once the sequence starts the result, as far as the tug
is concerned, is inevitable.

This is one of those situations where tug pilots are going to have to
decide what risks they are willing to take. I would support any tug pilot
who said that he would not tow a glider on a CoG or Compromise hook. On the
other hand I would not tell him he could not do it. There is also a
responsibility for those of us who teach aerotowing to really get across to
students the danger, to the tug pilot, of getting out of position. I am not
sure we have done this in the past, I know I have not been as pedantic as I
should in getting this point home.
Tug pilots do not always know the people they are towing so they are
perhaps not aware of the experience, or lack of it, of the pilot on the
back. In those circumstances the saviour should be the authoriser. We all
know that does not work. Perhaps tug pilots need to be more circumspect in
who they are prepared to tow.

On Tuesday, February 18, 2014 1:48:05 AM UTC-5, wrote:

Here is the link to the active thread on the AvCom site regarding this incident including the eye witness account. http://www.avcom.co.za/phpBB3/viewto...p?f=9&t=130916

Based on what was posted on that link, the pilot of the glider was expert, current, and flying a modern glider.