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

[son_of_flubber]

This topic was buried in a drifting degenerate thread. I'm wondering if anyone knows more about the tow hook innovation mentioned below by UH.

> On Saturday, February 8, 2014 9:31:13 AM UTC-5, son_of_flubber wrote:
>
> Why does the pilot need to pull the release if the glider kites? Why is the release for a deadly tow position not fully automatic? Is a simple purely mechanical, totally foolproof and 100% automatic release not possible? As the guy in the glider, I would be fine with a 100% automatic release. If I kite, release me immediately.
>

On Sunday, February 9, 2014 5:05:52 PM UTC-5, uncl...@ix.netcom.com wrote:>
>
> There was a design and prototype of a release like this created many years ago and published, I believe, in Soaring magazine. I know if no one that has adopted this which makes it fairly clear that this is not perceived as a huge problem.
>

[Mike the Strike]

The solution is simpler than that - it's called "low tow" - used in more civilized parts of the world.

Mike

[son_of_flubber]

On Sunday, February 9, 2014 8:58:56 PM UTC-5, Mike the Strike wrote:
> The solution is simpler than that - it's called "low tow" - used in more civilized parts of the world.

How do you do a low tow when both glider and tug are still in ground effect at launch?

[Don Johnstone]

At 22:27 09 February 2014, son_of_flubber wrote:
>This topic was buried in a drifting degenerate thread. I'm wondering if

>an=

>yone knows more about the tow hook innovation mentioned below by UH.
>
>> On Saturday, February 8, 2014 9:31:13 AM UTC-5, son_of_flubber wrote:

>>=20

>> Why does the pilot need to pull the release if the glider kites? Why is

>t=

>he release for a deadly tow position not fully automatic? Is a simple

>purel=

>y mechanical, totally foolproof and 100% automatic release not possible?

>As=

> the guy in the glider, I would be fine with a 100% automatic release. If

>I=
> kite, release me immediately.
>>=20

>
>On Sunday, February 9, 2014 5:05:52 PM UTC-5, uncl...@ix.netcom.com

>wrote:>=
>=20
>>=20

>> There was a design and prototype of a release like this created many

>year=

>s ago and published, I believe, in Soaring magazine. I know if no one
that

>=

>has adopted this which makes it fairly clear that this is not perceived
as

>=
>a huge problem.
>>
With any automatic system you need a fail safe mode. What would the fail
safe mode be for an automatic release device?
One of those areas where the medicine is potentially worse than the
disease.

[uncl...@ix.netcom.com]

On Sunday, February 9, 2014 8:58:56 PM UTC-5, Mike the Strike wrote:

> The solution is simpler than that - it's called "low tow" - used in more civilized parts of the world. Mike

And in the US. Our club in New York uses low tow as standard ops procedure. I'm not sure who else in US does.
UH

[kirk.stant]

If you are both in low tow you aren't kiting. Then, when the tow plane starts climbing, you ease down to the low tow position. No big deal.

Apparently standard ops in Australia - and some other "civilized" countries.

However, since kiting upsets are pretty much limited to older, low wing loading gliders, the problem is somewhat limited. In the US, my guess is that it is a threat from mainly 1-26s and 2-33s. My solution: careful briefing of 1-26 pilots, and chop up all the remaining 2-33s.

Kirk
66

[son_of_flubber]

On Monday, February 10, 2014 8:49:58 AM UTC-5, kirk.stant wrote:

> However, since kiting upsets are pretty much limited to older, low wing loading gliders, the problem is somewhat limited. In the US, my guess is that it is a threat from mainly 1-26s and 2-33s. My solution: careful briefing of 1-26 pilots, and chop up all the remaining 2-33s.
>

Are you saying that high performance gliders are incapable of kiting, or that the pilot of a high performance glider will never pull back on the stick at launch in ground effect?

Here is a kiting fatality with a Grob 103 Twin http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20001211X11267&key=2

Both pilots were experienced and current. Excerpt from the NTSB narrative:
"The pilot of the tow plane reported 5,078 hours of total flight experience, 1,245 hours of which were in the Cessna 305A. The (tow ed.) pilot reported 80 hours of flight experience in the 90 days prior to the accident, and 25 hours in the 30 days prior; all in the Cessna 305A. On October 5, 1998, the pilot performed 13 glider tows prior to the accident flight.

The glider pilot held a commercial pilot's certificate with ratings for airplane single engine land, glider, and instrument airplane. His most recent FAA second class medical certificate was issued June 26, 1997. The pilot reported 440 hours of flight experience on that date. A review of the glider pilot's logbook revealed 859 hours of total flight experience, of which 121 hours were in gliders."

[Eric Bick (1DB)]

On Sunday, February 9, 2014 5:58:56 PM UTC-8, Mike the Strike wrote:
> The solution is simpler than that - it's called "low tow" - used in more civilized parts of the world.
>
>
>
> Mike

I haven't tried low tow with my cg hook since it is up in the main wheel well. How does that (low tow) work with cg hook configurations? Any problems, or just chafing of the underbelly? Obviously, the tow rope has to extend forward on either the left or right side of the fuselage. Don't see flying two with constant yaw to prevent chafing. What about release? Any unintended consequences? I can maybe see the weak link rubbing up against the wheel well doors.

Also, our club has a PW-6 with chin hook. POH says - "Flying under the towing airplane downwash is not recommended since the towing cable rubs the fuselage front part."

Not sure low tow is the be-all, end-all answer.

Eric Bick -

[uncl...@ix.netcom.com]

On Monday, February 10, 2014 12:47:04 PM UTC-5, Eric Bick (1DB) wrote:
> On Sunday, February 9, 2014 5:58:56 PM UTC-8, Mike the Strike wrote: > The solution is simpler than that - it's called "low tow" - used in more civilized parts of the world. > > > > Mike I haven't tried low tow with my cg hook since it is up in the main wheel well. How does that (low tow) work with cg hook configurations? Any problems, or just chafing of the underbelly? Obviously, the tow rope has to extend forward on either the left or right side of the fuselage. Don't see flying two with constant yaw to prevent chafing. What about release? Any unintended consequences? I can maybe see the weak link rubbing up against the wheel well doors. Also, our club has a PW-6 with chin hook. POH says - "Flying under the towing airplane downwash is not recommended since the towing cable rubs the fuselage front part." Not sure low tow is the be-all, end-all answer. Eric Bick -

How much damage do you think the surface of the tow rope will do if it touches the belly?
My experience is absolutely none. We do use an adaptor on our ropes to convert from big (Schweizer) rings to Tost. It is about 4 ft long so there is no metal contact.
UH

[kirk.stant]

On Monday, February 10, 2014 8:55:46 AM UTC-6, son_of_flubber wrote:

> Are you saying that high performance gliders are incapable of kiting, or that the pilot of a high performance glider will never pull back on the stick at launch in ground effect?

If you do some research on kiting, you will find a good article in the BGA magazine about it.

To be pedantic, Kiting is defined as an uncontrollable pitchup and rise of the glider on tow - once it starts it happens so fast that it yanks the towplane tail up faster than the tow pilot can release. Most glass ships (due to wingloading, elevator authority, etc) appear to not be susceptible to this problem. Older light wingloading gliders are.

What the G-103 did in this accident is not kiting (technically), but just flying too high on tow (and totally the glider PIC's error) - the tow pilot should have released as soon as he reached the aft stop on the elevator. But with a Schweizer tow hook, that is damn near impossible unless it has the inverted mod.

There is also a long discussion somewhere (RAS, BGA?) about automatic releases, and the consensus was that it would be difficult to implement. Personally, I would imagine that a release triggered by hitting the aft stick stop might work, but it gets complicated on the ground, while landing, etc. Hugh potential for dropping ropes all over the place! It would have to sense the presence of a glider (tension on the rope) and the stick full aft and the towplane being airborne - then probably have to be a pyrotechnic guillotine to be reliable. Yeah, good luck getting a 337 for that past the FAA!

If a pilot pulls back on the stick that hard during launch when I'm towing, and I survive the crash, I am going to beat the shit out of him and his instructor(s) with a broken Pawnee wing strut. I've had a student pitch up in a 2-33 (solo) to do a soft release (argghhh!) and pull my Pawnee's tail up (during a pattern tow, no less). He released just before I did. He got seriously talked to after landing.

Yes, glider pilots can kill tow pilots. As a glider pilot you should think of that every time you get hooked up for a tow. And fly your tow like a damn Blue Angel!

Kirk
66

By the way, you can also give your towpilot a thrill by pulling way off to the side - and if he is stupid enough to keep full rudder in and try to fight you, you can stall his vertical stab/rudder - and off he goes into Mr Toad's wild ride as his plane loses all yaw stability all at once!

Unless I'm told the glider is going to box the wake, I pretty much keep my feet off the rudders and let the glider point me wherever he wants...

[Don Johnstone]

At 17:47 10 February 2014, Eric Bick 1DB wrote:

What about release? Any
>unintended=

> consequences? I can maybe see the weak link rubbing up against the wheel

>w=

>ell doors.
>
>Also, our club has a PW-6 with chin hook. POH says - "Flying under the

>towi=

>ng airplane downwash is not recommended since the towing cable rubs the

>fus=

>elage front part."
>
>Not sure low tow is the be-all, end-all answer.
>
>Eric Bick

I think you will find the recommended procedure is to move up to high tow
for release, ask the Aussies, they are the experts on this. I do use low
tow but always move to high tow for the release.
>

[uncl...@ix.netcom.com]

On Monday, February 10, 2014 1:35:29 PM UTC-5, Don Johnstone wrote:
> At 17:47 10 February 2014, Eric Bick 1DB wrote: What about release? Any >unintended= > consequences? I can maybe see the weak link rubbing up against the wheel >w= >ell doors. > >Also, our club has a PW-6 with chin hook. POH says - "Flying under the >towi= >ng airplane downwash is not recommended since the towing cable rubs the >fus= >elage front part." > >Not sure low tow is the be-all, end-all answer. > >Eric Bick I think you will find the recommended procedure is to move up to high tow for release, ask the Aussies, they are the experts on this. I do use low tow but always move to high tow for the release. >

I have something over 11000 tow done in low tow and release from that position all the time. Properly done, the rope goes away straight out and does not end up above the sailplane. If does end up above, the pilot was too low when releasing.
UH

[Karl Striedieck]

A Brit made such a device and the design was circulated around. Externally, it was shaped something like a Tost release, but the tow ring would slip out when the rope angle increased to X degrees.

[Chris Rollings]

Tried to post this yesterday bit it didn't appear. For some reason my
(rare) posts to ras often don't appear. I will also post it on uras and
ask someone to post it on for me. Apologies if that results in
repetition.

Whilst I was Chief Instructor at Booker Gliding Club, we conducted two
series of test on the phenomenon variously referred to as “Kiting”,
“Winch Launching behind the Tow-Plane” and “Sling-Shot Accident”,
one in 1978 and one in 1982; my memory of them is quite vivid.
 
Airplanes used were, for the first series, a Beagle Terrier (a side by
side, two place, high wing, tail-dragger), fitted with an Ottfur Glider
hook for towing (very similar to the Tost hook, dissimilar to the Schweizer
hook) with a 160 hp Lycoming engine; for the second series of tests a
PA18-180 with a Schweitzer hook was used. Gliders used were a Schleicher
Ka 8b and ASK 13. Tow rope initially used was a heavy (4000 lb breaking
strain) rope with a thinner rope weak link at the glider end (nominally 900
lb, but a well worn specimen could break at as little as 200 – 300 lbs
– laboratory tests, not opinion), the second series of test used the same
heavy duty rope with “Mity” links at each end, 1100 lbs at the
Tow-Plane end and 900 lbs at the Glider end – these links use metal shear
pins, one under load and a second unloaded, which takes over if the first
one fails. This eliminates failure due to fatigue and means that the links
always fail at close to their nominal load even after some time in service
– again laboratory tested, not just subjective opinion. Rope length was
around 180 feet in all cases.
 
I was the Glider Pilot on all tests; Tow-Plane Pilot was Verdun Luck (then
my deputy Chief Instructor) for the first series of tests and Brian
Spreckley (then Manager of Booker GC) for the second. The object of the
tests was to try to reproduce the “Kiting” under controlled
circumstances, with a view to developing a Tow-Plane release mechanism that
would automatically release the glider if it got dangerously high above the
Tow-Plane. All tests were conducted at about 4000 feet agl.
 
First test: Terrier Tow-Plane and ASK 13 on nose-hook. At about 4000 feet
I took the glider progressively higher above the tow-plane, eventually
reached about 100 feet above tow-plane (i.e. rope angle more than 45
degrees above horizontal). At about this point, the tow pilot, who had
been using progressively more back stick, ran out of back stick and the
Tow-Plane began to pitch nose down but not excessively violently. I
released at that point. It took a very positive control input on my part
to achieve the displacement, we both felt it was something unlikely to
occur accidentally, even with an inexperienced glider pilot, and there was
plenty of time for either party to release if it did occur.
 
Second test: Terrier Tow-Plane and ASK 13 on C of G hook. I pitched the
glider about 25 – 30 degrees nose up – the weak link broke immediately!
Tow pilot reported a sharp jerk, but no significant change to flight
path.
 
Third test: Terrier Tow-Plane, K 8b on C of G hook. I pitched the glider
about 25 degrees nose up. The glider continued to pitch up fairly rapidly
(as at the start of a winch launch) and substantial forward movement of the
stick only slightly slowed the rate of pitch. The glider achieved about 45
degrees nose up, speed increased rapidly from 55 knots to about 75 knots
and the glider was pulled back towards level flight (again as at the top of
a winch launch). I released at that point. The entire sequence of events
occupied a VERY short period of time (subsequently measured as 2 - 3
seconds). The Tow Pilot reported a marked deceleration and start of
pitching down which he attempted to contain by moving the stick back; this
was followed immediately by a very rapid pitch down accompanied by
significant negative “G”. The tow-plane finished up about 70 degrees
nose down and took about 400 feet to recover to level flight. We both
found the experience alarming, even undertaken deliberately at 4000 feet.
Our conclusion was that the combination of the initial pitch down and the
upward deflection of the elevator caused the horizontal stabilizer/elevator
combination to stall and the abrupt removal of the down-force it provided
caused the subsequent very rapid pitch-down and negative “G”.
 
Our first conclusion was that, in the event of this sequence occurring
accidentally as a result of an inadvertent pitch up by the glider pilot,
there was effectively no chance that either the glider pilot or tow-pilot
would recognise the problem and pull the release in the available time.
 
Attempts to produce a tow-plane hook that would release automatically were
unsuccessful for reasons that became apparent later.
 
These tests were repeated a few years later with a PA18 – 180 as the
tow-plane, Brian Spreckley flying it. The third test described above was
repeated and photographed from a chase plane using a 35 mm motor drive
camera on automatic (this took a frame every half second – video
camcorders of small size were not readily available then). The photo
sequence started with the glider in a slightly low normal tow position and
starting to pitch up, the second frame has the glider about 30 degrees nose
up and about 20 feet higher than previously in the third frame it is about
45 degrees nose up and has gained another 30 feet or so, the tow-plane is
already starting to pitch down, in the fourth frame the glider is about 100
feet higher than its original position and the climb is starting to
shallow, the tow-plane is about 50 degrees nose down, the final frame shows
the tow-plane about 70 degrees nose down and the glider almost back in
level flight , almost directly above it (that was about the point that I
pulled the release).
 
Sufficiently alarmed by events, Brian Spreckley had been trying to pull the
release in the tow-plane earlier and found that it would not operate until
my releasing at the glider end removed the tension from the rope.
Subsequent tests on the ground showed that the Schweizer hook fitted to the
tow-plane, whilst perfectly satisfactory under normal loads, was jammed
solid by the frictional loads when subject to a pull of around 700 lbs with
a slight upwards component – not something that a normal pre-flight check
would reveal.
 
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 in
the UK has tested the Schweizer hook as fitted to a glider, but I would not
be surprised if it exhibited the same characteristics at high loads.
 
The photo sequence also showed that at no time was the glider at an angle
greater than 30 degrees above the tow-plane’s centre-line. However, of
course once the glider has pitched up, the wings generate considerable
extra lift and that extra lift provides extra load on the rope. With a
large, heavy glider it is easy to exceed weak link breaking strains and
with a lightweight machine the tension can easily rise to 700 lbs or so.
With that much load on the rope, quite a small upward angle provides enough
of a vertical component to produce the results described.
 
That of course is the reason that attempts to produce a hook that released
if a certain angle was exceeded were unsuccessful. The, quite small, angle
between the rope and the fuselage centreline 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 fool-proof enough to be attached to the rear end of a
tow-plane).
 
Our conclusions for preventing “Kiting” were:
 
Don’t aerotow gliders, especially lightweight, low wing-loading gliders,
on C of G hooks intended for winch launching (I think the JAR 22
requirement for nose hooks to be fitted to new gliders for aerotowing was
at least in part a result of these tests).
 
Don’t use short ropes. The speed at which things happen varies directly
with the length of the rope.
 
Don’t let inexperienced pilots fly at anywhere near aft C of G.
 
Don’t let inexperienced pilots fly solo in turbulent conditions.
 
Replace or modify all Schweizer hooks fitted to tow planes. (So far as I
know there are none on gliders in the UK, so that question never arose).
 
We did also modify our PA18’s so that instead of the release cable ending
at a floor-mounted lever, it went round a pulley where that lever used to
be, and then all the way up the side of the cockpit, anchored at the roof.
This meant that grabbing any point on the wire and pulling it in any
direction could operate the release; considerably easier than finding a
floor mounted lever when being subject to about minus two “G”. We
never regarded this modification as being likely to prevent a worst-case
scenario, because, as stated earlier, it was the opinion of all involved,
that in a real “Kiting” incident, there was no realistic hope that
either pilot would respond in time.

At 20:32 10 February 2014, Karl Striedieck wrote:
>On Sunday, February 9, 2014 5:27:23 PM UTC-5, son_of_flubber wrote:
>> This topic was buried in a drifting degenerate thread. I'm wondering
if

>=

>anyone knows more about the tow hook innovation mentioned below by UH.

>>=20
>>=20
>>=20

>> > On Saturday, February 8, 2014 9:31:13 AM UTC-5, son_of_flubber wrote:

>>=20
>> >=20
>>=20

>> > Why does the pilot need to pull the release if the glider kites? Why

>is=

> the release for a deadly tow position not fully automatic? Is a simple

>pur=

>ely mechanical, totally foolproof and 100% automatic release not
possible?

>=

>As the guy in the glider, I would be fine with a 100% automatic release.

>If=

> I kite, release me immediately.

>>=20
>> >=20
>>=20
>>=20
>>=20

>> On Sunday, February 9, 2014 5:05:52 PM UTC-5, uncl...@ix.netcom.com

>wrote=
>:>=20
>>=20
>> >=20
>>=20

>> > There was a design and prototype of a release like this created many

>ye=

>ars ago and published, I believe, in Soaring magazine. I know if no one

>tha=

>t has adopted this which makes it fairly clear that this is not perceived

>a=
>s a huge problem.
>>=20

>> >
>
>A Brit made such a device and the design was circulated around.

>Externally,=

> it was shaped something like a Tost release, but the tow ring would slip

>o=

[Chris Rollings]

From our experiments, being in low tow would only increase the available
time in which to release by less than 1 second. More to the point, in my
opinion, descending through the turbulent prop wash shortly after take-off
could quite easily trigger the momentary loss of control that would
precipitate the kiting event.

At 18:35 10 February 2014, Don Johnstone wrote:
>At 17:47 10 February 2014, Eric Bick 1DB wrote:
>
> What about release? Any
>>unintended=
>> consequences? I can maybe see the weak link rubbing up against the
wheel
>>w=
>>ell doors.
>>
>>Also, our club has a PW-6 with chin hook. POH says - "Flying under the
>>towi=
>>ng airplane downwash is not recommended since the towing cable rubs the
>>fus=
>>elage front part."
>>
>>Not sure low tow is the be-all, end-all answer.
>>
>>Eric Bick
>
>I think you will find the recommended procedure is to move up to high to

>for release, ask the Aussies, they are the experts on this. I do use lo

[son_of_flubber]

On Tuesday, February 11, 2014 3:56:33 AM UTC-5, Chris Rollings wrote:

>>>>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 fool-proof enough to be attached to the rear end of a
tow-plane).<<<<

Thank you Mr. Rollings for your pioneering work with tow hooks and thank you for responding to my question.

(And thanks to all the people who deployed the internet and made conversations like this one possible. Wow.)

[Bob Kuykendall]

On Tuesday, February 11, 2014 12:56:33 AM UTC-8, Chris Rollings wrote:
> Tried to post this yesterday bit it didn't appear. For some reason my

> (rare) posts to ras often don't appear....

There you go, messing up a perfectly good Internet discussion with actual data and relevant experience. :)

But seriously, thanks for posting about this. Your investigation supports my general working thesis that for every problem there exists a solution that is simple, obvious, and wrong.

Bob K.

[son_of_flubber]

On Tuesday, February 11, 2014 3:56:33 AM UTC-5, Chris Rollings wrote:

>>>> What was needed was a hook that
responded to the vertical component of the load, not the angle at which it

was applied...<

This statement defines the starting point, not the ending point.

How about a weather proof calibrated mechanical device placed between the Tost release hook and the tug that pulls the Tost release lever when the vertical component exceeds a limit? There is a well-proven mechanism that does something like that on my downhill ski bindings. A rocket-scientist is not required.

Is it a matter of the FAA and insurance underwriters making any change to the status quo cost-prohibitive? What sort of gauntlet does one need to run?

[kirk.stant]

On Tuesday, February 11, 2014 12:41:48 PM UTC-6, son_of_flubber wrote:

> How about a weather proof calibrated mechanical device placed between the Tost release hook and the tug that pulls the Tost release lever when the vertical component exceeds a limit? There is a well-proven mechanism that does something like that on my downhill ski bindings. A rocket-scientist is not required.

Well, if you think it is that big a problem and it can't be addressed through better (more threatening) training, then how about an optical device on the towplane that tracks the glider and 1. warns the tow pilot and glider pilot when the glider is moving out of the safe tow envelope, and 2. fires a guillotine on the tow rope when the glider reaches the limit. Add a flashing light on the tow plane to warn the glider pilot that he is about to be dumped.

Or, just teach the glider pilot to NEVER lose sight of the towplane, and to immediately release if he does.

> Is it a matter of the FAA and insurance underwriters making any change to the status quo cost-prohibitive? What sort of gauntlet does one need to run?

Bwahahahaha!!!!

ROTFLMFAO!

Gasp, sigh, that just really made my day!

Cheers,

Kirk
66

[Colin Wray]

Chris Rollings <chrisr...@msn.com> wrote:

>Third test: Terrier Tow-Plane, K 8b on C of G hook. I pitched the glider
>about 25 degrees nose up. The glider continued to pitch up fairly rapidly
>(as at the start of a winch launch) and substantial forward movement of the
>stick only slightly slowed the rate of pitch. The glider achieved about 45
>degrees nose up, speed increased rapidly from 55 knots to about 75 knots
>and the glider was pulled back towards level flight (again as at the top of
>a winch launch). I released at that point. The entire sequence of events
>occupied a VERY short period of time (subsequently measured as 2 - 3
>seconds). The Tow Pilot reported a marked deceleration and start of
>pitching down which he attempted to contain by moving the stick back; this
>was followed immediately by a very rapid pitch down accompanied by

>significant negative “G�€?. The tow-plane finished up about 70 degrees

>nose down and took about 400 feet to recover to level flight. We both
>found the experience alarming, even undertaken deliberately at 4000 feet.
>Our conclusion was that the combination of the initial pitch down and the
>upward deflection of the elevator caused the horizontal stabilizer/elevator
>combination to stall and the abrupt removal of the down-force it provided

>caused the subsequent very rapid pitch-down and negative “G�€?.

I was the pilot of a tug involved in exactly the scenario described by
Chris above. The culprit was a K6 using a belly hook, and the only
reason I am here to tell the tale is that it occurred at 400ft. It was
actually a dual tow with the K6 on the short rope and a K13 on the
long rope in low-tow position. The K6 had recovered from some earlier
excursions, but all seemed to be going well before it happened.

The "up-ending" was instantaneous, there was no way to have reached
any type of release before the rope broke, and in any case I can
assure you that when descending vertically on full throttle at 400ft,
your first reaction it to close the throttle.

Our CFI in the K13 said he hadn't seen the underside of a PA18 in plan
form quite so close before.

In those days we used to store spare ropes and things behind the rear
seat of the PA18, and my situation was not improved by the whole lot
coming forward and landing on my head and all over the cockpit.

A good friend of mine later died towing a K6 with a PA18, which
incident quite probably was the trigger for Chris' investigations.

[son_of_flubber]

http://i.imgur.com/wPwWj.gif

[kirk.stant]

On Tuesday, February 11, 2014 6:26:21 PM UTC-6, son_of_flubber wrote:

> http://i.imgur.com/wPwWj.gif

Cute!

Seriously, the biggest problem is probably just plain cost. Everybody knows the Schweizer tow releases are junk and dangerous - but (like the Schweizer gliders) they are cheap and available. So we use them. There is a much better and safer replacement - the Tost - but it cost so much that when you try to get a club interested in replacing their Schweizer hooks with Tost hooks you get laughed out of the club house.

So for now we are stuck with solving (a real but fortunately rare) the problem with better awareness of what can happen (by both the tugger and tuggee) and better training.

Now, if anybody has any spare explosive bolts laying around, we could probably come up with some kind of emergency release that the tow pilot could activate under any condition...(just don't let your local FAA guy see it).

Cheers,

Kirk
66

[uncl...@ix.netcom.com]

On Wednesday, February 12, 2014 8:43:35 AM UTC-5, kirk.stant wrote:
> On Tuesday, February 11, 2014 6:26:21 PM UTC-6, son_of_flubber wrote: > http://i.imgur.com/wPwWj.gif Cute! Seriously, the biggest problem is probably just plain cost. Everybody knows the Schweizer tow releases are junk and dangerous - but (like the Schweizer gliders) they are cheap and available. So we use them. There is a much better and safer replacement - the Tost - but it cost so much that when you try to get a club interested in replacing their Schweizer hooks with Tost hooks you get laughed out of the club house. So for now we are stuck with solving (a real but fortunately rare) the problem with better awareness of what can happen (by both the tugger and tuggee) and better training. Now, if anybody has any spare explosive bolts laying around, we could probably come up with some kind of emergency release that the tow pilot could activate under any condition...(just don't let your local FAA guy see it). Cheers, Kirk 66

The only explosive allowed in our tugs is the tow pilot.
UH

[Dan Marotta]

Ain't no doubt about how quickly the tug gets upset when the glider decides
to fly hither and yon.

My event involved a highly experienced retired FAA guy with type ratings in
every aircraft imagineable. It was his first flight in a borrowed HP-14
and, during the departure turn at about 700' AGL he flew high and wide to
the right, outside of the turn. Before I could reach the release lever,
he'd turned hard left and dove across the tail of the Pawnee wrapping the
tow rope around his left wing and, after it cut the top and bottom skins of
the wing clear to the spar, cutting the rope in two in the middle. The
final yank on the rope caused the tug to yaw hard right and pitch slightly
up (from about 45 degrees down).

Not realizing how close he'd come to killing us both, he proceeded to have a
nice 4-hour flight. After landing he asked our line guy to help with
derigging. That's when Steve called him to the left side of the glider and
pointed out the damage.

I had a few words with him, too.

"Colin Wray" <nos...@nospam.invalid> wrote in message
news:vidlf9dobt8fnnmnn...@4ax.com...

> Chris Rollings <chrisr...@msn.com> wrote:
>
>>Third test: Terrier Tow-Plane, K 8b on C of G hook. I pitched the glider
>>about 25 degrees nose up. The glider continued to pitch up fairly rapidly
>>(as at the start of a winch launch) and substantial forward movement of
>>the
>>stick only slightly slowed the rate of pitch. The glider achieved about
>>45
>>degrees nose up, speed increased rapidly from 55 knots to about 75 knots
>>and the glider was pulled back towards level flight (again as at the top
>>of
>>a winch launch). I released at that point. The entire sequence of events
>>occupied a VERY short period of time (subsequently measured as 2 - 3
>>seconds). The Tow Pilot reported a marked deceleration and start of
>>pitching down which he attempted to contain by moving the stick back; this
>>was followed immediately by a very rapid pitch down accompanied by

>>significant negative â?oGâ??. The tow-plane finished up about 70 degrees

>>nose down and took about 400 feet to recover to level flight. We both
>>found the experience alarming, even undertaken deliberately at 4000 feet.
>>Our conclusion was that the combination of the initial pitch down and the
>>upward deflection of the elevator caused the horizontal
>>stabilizer/elevator
>>combination to stall and the abrupt removal of the down-force it provided

>>caused the subsequent very rapid pitch-down and negative â?oGâ??.

[SF]

I think we could combine an optical target designator from an air to air missile, and some explosive bolts, and come up with a solution here, loose the target lock with a speed above 20 Kts, and ring in the hook, and you fire the bolts. Maybe we could get DARPA to fund it. Forget the flashing light on the back of the tow plane, we will use the flare system from a C130 to let everyone know what just happened. I'm in, anybody know how to write a grant proposal? Explosive bolts, missile parts, really cool flares, what's not to like?

[kirk.stant]

On Wednesday, February 12, 2014 11:43:18 AM UTC-6, SF wrote:
> I think we could combine an optical target designator from an air to air missile, and some explosive bolts, and come up with a solution here, loose the target lock with a speed above 20 Kts, and ring in the hook, and you fire the bolts. Maybe we could get DARPA to fund it. Forget the flashing light on the back of the tow plane, we will use the flare system from a C130 to let everyone know what just happened. I'm in, anybody know how to write a grant proposal? Explosive bolts, missile parts, really cool flares, what's not to like?

And we mount it with a Picatinny rail - painted desert camo.

Totally tacticool!

Kirk

[son_of_flubber]

On Wednesday, February 12, 2014 12:03:17 PM UTC-5, Dan Marotta wrote:
> Ain't no doubt about how quickly the tug gets upset when the glider decides
>
> to fly hither and yon.
>
>
>
> My event involved a highly experienced retired FAA guy with type ratings in
>
> every aircraft imagineable. It was his first flight in a borrowed HP-14
>
> and, during the departure turn at about 700' AGL he flew high and wide to
>
> the right, outside of the turn. Before I could reach the release lever,
>
> he'd turned hard left and dove across the tail of the Pawnee wrapping the
>
> tow rope around his left wing and, after it cut the top and bottom skins of
>
> the wing clear to the spar, cutting the rope in two in the middle. The
>
> final yank on the rope caused the tug to yaw hard right and pitch slightly
>
> up (from about 45 degrees down).

Yikes. Over confidence and diminished capacity are a bad combination.

Annual flight reviews would head off more accidents than better tow hooks.

[Dale Watkins]

My KA6CR lite to fly high - I have to keep the stick forward on tow -

ZEN

[Dan Marotta]

The camo paint would not be approved for use in CA or NY. Too evil looking,
don'tcha know... It would probably be OK in NJ as long as the release
mechanism did not incorporate a "hollow point".


"kirk.stant" <kirk....@gmail.com> wrote in message
news:852788ca-5e88-443e...@googlegroups.com...

[Dan Marotta]

Now don't try to increase the number of "flight reviews" we must endure,
Young Grasshopper.

It's more about currency than reviews. Fly more and you'll be amazed at how
much more competent and knowledgeable you are.

"son_of_flubber" <row...@gmail.com> wrote in message
news:31f8b372-9657-486e...@googlegroups.com...

[chrisr...@msn.com]

My statement that an automatic releasing hook was beyond our capabilities refered to the situation over 30 years ago, it is quite possible that technology has moved on a bit since then and it is now possible. It would certainly constiute a modification to the aircraft under UK/European rules, and I strongly suspect ander FAA rules too. As such it would need approval, time consuming and possibly expensive.

[son_of_flubber]

On Thursday, February 13, 2014 10:39:33 AM UTC-5, Dan Marotta wrote:
> Now don't try to increase the number of "flight reviews" we must endure,
> Young Grasshopper.

Due to lax enforcement, flight reviews for glider pilots are already in effect voluntary.

I'm suggesting that pilots who know that their capacities are in decline, might in an ideal world, volunteer for 'early' flight review. I realize that a primary symptom of cognitive decline is an inability to recognize or acknowledge that decline (and irritation with anyone who raises the point).

If that "expert pilot" who nearly killed you on tow, had taken a timely flight review, the whole incident might never had happened.

Experts inevitably grow incompetent over time and some of them continue to fly.

[Dan Marotta]

Now I understand your point. That pilot had a lot of type ratings,
airliners and such. He was a neophyte glider pilot who was given the use of
a glider that he had no business flying. Of course, I didn't know that at
the time.

"son_of_flubber" <row...@gmail.com> wrote in message

news:7136d3e4-a61b-460d...@googlegroups.com...

[son_of_flubber]

On Thursday, February 13, 2014 8:40:08 PM UTC-5, Dan Marotta wrote:
> He was a neophyte glider pilot who was given the use of
> a glider that he had no business flying.

I would expect most neophyte glider pilots to land soon and inspect for damage after wrapping the tow rope around the wing and jerking loose. You might see why I concluded that this guy had more issues than inexperience in a glider.

His inexperience on tow may have lead to entanglement with the rope, but what reasonable person would elect to fly a potentially damaged aircraft for four hours?

[Don Johnstone]

At 22:39 11 February 2014, kirk.stant wrote:

>
>Or, just teach the glider pilot to NEVER lose sight of the towplane, and

>to=
> immediately release if he does. =20
>=20

>> Is it a matter of the FAA and insurance underwriters making any change

>to=

> the status quo cost-prohibitive? What sort of gauntlet does one need to

>r=
>un?

One of the never to be breached rules of aerotowing for a glider pilot in
the UK is "if at any time you loose sight of the tug for ANY reason you are
to pull the release"
If you read Chris's article carefully you may deduce that in the worst case
scenario, the rapid vertical departure of the glider, by the time the
glider pilot realises he has lost sight of the tug, and attempts to pull
the release it is already far to late to make any significant difference to
what is going to happen.

"Our first conclusion was that, in the event of this sequence occurring
accidentally as a result of an inadvertent pitch up by the glider pilot,
there was effectively no chance that either the glider pilot or tow-pilot
would recognise the problem and pull the release in the available time."

It was this very scenario that killed a very good friend of mine who was a
very experienced tug pilot. There are some events that, paradoxically,
require corrective action to commence before onset if they are to be
effective in time to change the outcome.

As for cheap solutions, I am firmly of the view that most wooden gliders
with only CoG hooks should not be aerotowed, those with compromise hooks
should be aerotowed with extreme care.

[Chris Rollings]

At 01:21 16 February 2014, Don Johnstone wrote:
>At 22:39 11 February 2014, kirk.stant wrote:
>
>>
>>Or, just teach the glider pilot to NEVER lose sight of the towplane, and
>>to=
>> immediately release if he does. =20
>>=20
>>> Is it a matter of the FAA and insurance underwriters making any change
>>to=
>> the status quo cost-prohibitive? What sort of gauntlet does one need
to
>>r=
>>un?
>
>One of the never to be breached rules of aerotowing for a glider pilot i

>the UK is "if at any time you loose sight of the tug for ANY reason you
ar

>to pull the release"
>If you read Chris's article carefully you may deduce that in the worst
cas

>scenario, the rapid vertical departure of the glider, by the time th

>glider pilot realises he has lost sight of the tug, and attempts to pul

>the release it is already far to late to make any significant difference
t

>what is going to happen.
>
>"Our first conclusion was that, in the event of this sequence occurring
>accidentally as a result of an inadvertent pitch up by the glider pilot,
>there was effectively no chance that either the glider pilot or tow-pilot
>would recognise the problem and pull the release in the available time."
>
>It was this very scenario that killed a very good friend of mine who was

>very experienced tug pilot. There are some events that, paradoxically

>require corrective action to commence before onset if they are to b

>effective in time to change the outcome.
>
>As for cheap solutions, I am firmly of the view that most wooden glider

>with only CoG hooks should not be aerotowed, those with compromise hook

>should be aerotowed with extreme care.
>
>

I would add that, although I haven't done the same tests with any glass
gliders, I'm pretty sure that many of the light-weight Standard/15m types
would behave in the same way on a C of G hook. Std Cirrus would be a prime
candidate, would somebody with access to one care to try it at safe
altitude and report the result?

What I find rather sad about the gliding movement is the lack of
willingness to go and get the facts. We have been aware of this problem
for over 35 years, I described flights tests that I carried out, to try to
improve understanding and seek a solution. Has anyone else done the same?

[Jonathon May]

At 08:50 16 February 2014, Chris Rollings wrote:
>At 01:21 16 February 2014, Don Johnstone wrote:
>>At 22:39 11 February 2014, kirk.stant wrote:
>>
>>>
>>>Or, just teach the glider pilot to NEVER lose sight of the towplane,
and
>>>to=
>>> immediately release if he does. =20
>>>=20
>>>> Is it a matter of the FAA and insurance underwriters making any
change
>>>to=
>>> the status quo cost-prohibitive? What sort of gauntlet does one nee

>to
>>>r=
>>>un?
>>
>>One of the never to be breached rules of aerotowing for a glider pilot i
>>the UK is "if at any time you loose sight of the tug for ANY reason yo

>ar
>>to pull the release"
>>If you read Chris's article carefully you may deduce that in the wors

>cas
>>scenario, the rapid vertical departure of the glider, by the time th
>>glider pilot realises he has lost sight of the tug, and attempts to pul
>>the release it is already far to late to make any significant differenc

>t
>>what is going to happen.
>>
>>"Our first conclusion was that, in the event of this sequence occurring
>>accidentally as a result of an inadvertent pitch up by the glider pilot,
>>there was effectively no chance that either the glider pilot or
tow-pilot
>>would recognise the problem and pull the release in the available time."
>>
>>It was this very scenario that killed a very good friend of mine who was

>>very experienced tug pilot. There are some events that, paradoxically
>>require corrective action to commence before onset if they are to b
>>effective in time to change the outcome.
>>
>>As for cheap solutions, I am firmly of the view that most wooden glider
>>with only CoG hooks should not be aerotowed, those with compromise
hook
>>should be aerotowed with extreme care.
>>
>>
>
>I would add that, although I haven't done the same tests with any glas

>gliders, I'm pretty sure that many of the light-weight Standard/15m type

>would behave in the same way on a C of G hook. Std Cirrus would be a
prim

>candidate, would somebody with access to one care to try it at saf

>altitude and report the result?
>
>What I find rather sad about the gliding movement is the lack o

>willingness to go and get the facts. We have been aware of this proble

>for over 35 years, I described flights tests that I carried out, to try t

>improve understanding and seek a solution. Has anyone else done the
same?
>

In my opinion more relevant has any one tried these departures from track
with the next generation tugs eurofox to name but one.
We are all used to boxing the wake of a Pawnee and I know the teams
introducing them into clubs are taking a steady measured introduction .
But I don't want to be known as the the guy that killed the tuggie because
I
didn't know what was acceptable .
My apologies to all at YGC for washing in public but this thread stirred my

concerns and I know that when I get to fly behind the fox I will get a
briefing
But as Chris said until you have tested and published the results no one
knows.
Jon
>

[Chris Rollings]

At 10:06 16 February 2014, Jonathon May wrote:
>At 08:50 16 February 2014, Chris Rollings wrote:
>>At 01:21 16 February 2014, Don Johnstone wrote:
>>>At 22:39 11 February 2014, kirk.stant wrote:
>>>
>>>>
>>>>Or, just teach the glider pilot to NEVER lose sight of the towplane,
>and
>>>>to=
>>>> immediately release if he does. =20

Jon, I share your concern about the new generation of light-weight
tow-planes, I strongly suspect they will be more vulnerable to upset
accidents. I think that carrying out test like the ones I described should
be a requirement before the authorities approve the type for towing. It
may be possible I'll get the chance to try it out behind a Eurofox later
this year, I'll publish the results here if I do.

[herbk...@gmail.com]

Imagine a proximity switch built into the tow hook in the nose of any glider. It could be adjusted in such a way that it senses the larger tow ring position moving down when the glider is kiting. That signal could be hooked up to a warning horn or speech output "Glider too high". I realize that the warning would sound on the ground until the rope is tight. Sensing airspeed above 25 knots would address that problem.
Herb

[Chris Rollings]

At 15:37 16 February 2014, herbk...@gmail.com wrote:
>On Sunday, February 16, 2014 5:01:24 AM UTC-6, Chris Rollings wrote:
>> At 10:06 16 February 2014, Jonathon May wrote:

>>=20

>> >At 08:50 16 February 2014, Chris Rollings wrote:

>>=20

>> >>At 01:21 16 February 2014, Don Johnstone wrote:

>>=20

>> >>>At 22:39 11 February 2014, kirk.stant wrote:

>>=20
>> >>>
>>=20
>> >>>>
>>=20

>> >>>>Or, just teach the glider pilot to NEVER lose sight of the
towplane,

>>=20
>> >and
>>=20
>> >>>>to=3D
>>=20
>> >>>> immediately release if he does. =3D20
>>=20
>>=20

>>=20
>> >>>>> Is it a matter of the FAA and insurance underwriters making

any=20
>>=20
>> >change
>>=20
>> >>>>to=3D
>>=20

>> >>>> the status quo cost-prohibitive? What sort of gauntlet does one
nee

>>=20
>> >>to
>>=20
>> >>>>r=3D
>>=20
>> >>>>un?
>>=20
>> >>>
>>=20

>> >>>One of the never to be breached rules of aerotowing for a glider
pilot

>>=20
>> i
>>=20

>> >>>the UK is "if at any time you loose sight of the tug for ANY reason
yo

>>=20
>> >>ar
>>=20
>> >>>to pull the release"
>>=20

>> >>>If you read Chris's article carefully you may deduce that in the
wors

>>=20
>> >>cas
>>=20

>> >>>scenario, the rapid vertical departure of the glider, by the time th

>>=20

>> >>>glider pilot realises he has lost sight of the tug, and attempts to

>pu=
>l
>>=20

>> >>>the release it is already far to late to make any significant

>differen=
>c
>>=20
>> >>t
>>=20

>> >>>what is going to happen.

>>=20
>> >>>
>>=20
>>=20
>>=20
>>=20
>>=20

>> >>>"Our first conclusion was that, in the event of this sequence

>occurrin=
>g
>>=20

>> >>>accidentally as a result of an inadvertent pitch up by the glider

>>=20
>> pilot,
>>=20

>> >>>there was effectively no chance that either the glider pilot or

>>=20
>> >tow-pilot
>>=20

>> >>>would recognise the problem and pull the release in the available

>>=20
>> time."
>>=20
>> >>>
>>=20

>> >>>It was this very scenario that killed a very good friend of mine who

>>=20
>> was
>>=20
>> >
>>=20

>> >>>very experienced tug pilot. There are some events that,
paradoxically

>>=20

>> >>>require corrective action to commence before onset if they are to b

>>=20
>> >>>effective in time to change the outcome.=20
>>=20
>> >>>
>>=20

>> >>>As for cheap solutions, I am firmly of the view that most wooden

>glide=
>r
>>=20

>> >>>with only CoG hooks should not be aerotowed, those with

compromise=20
>>=20
>> >hook
>>=20

>> >>>should be aerotowed with extreme care.

>>=20
>> >>>
>>=20
>> >>>
>>=20
>> >>
>>=20

>> >>I would add that, although I haven't done the same tests with any
glas

>>=20

>> >>gliders, I'm pretty sure that many of the light-weight Standard/15m

>typ=
>e
>>=20

>> >>would behave in the same way on a C of G hook. Std Cirrus would be

a=
>=20
>>=20
>> >prim
>>=20

>> >>candidate, would somebody with access to one care to try it at saf

>>=20

>> >>altitude and report the result?

>>=20
>> >>
>>=20

>> >>What I find rather sad about the gliding movement is the lack o

>>=20

>> >>willingness to go and get the facts. We have been aware of this
proble

>>=20

>> >>for over 35 years, I described flights tests that I carried out, to
try

>>=20
>> t
>>=20

>> >>improve understanding and seek a solution. Has anyone else done

the=20
>>=20
>> >same?
>>=20
>> >>
>>=20
>> >
>>=20

>> >In my opinion more relevant has any one tried these departures from

>trac=
>k
>>=20
>>=20
>>=20

>> >with the next generation tugs eurofox to name but one.

>>=20
>> >We are all used to boxing the wake of a Pawnee and I know the teams=20
>>=20

[Colin Wray]

Chris, as it happens I have also been in the glider during one of
these incidents, and once again I emphasise that it is all over in
fractions of a second, with absolutley no chance to take any sort of
corrective action.

It was not a light sailplane either - an ASH25 in fact - flown by its
owner with me taking no part in the rear cockpit. (I will try to be
more observant in future). The airbrakes had opened as we left the
ground, and although the tug pilot was shouting 'bremse' into his
radio it took quite some time for the translation to sink in, at which
point P1 slammed the brakes shut and quite possibly and inadvertantly
pulled back on the stick. Bang, all over, and one very annoyed and
very lucky tug pilot back on the ground. Maybe the time to translate
the message saved his life.

[SF]

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 where the upwards angle of the tow rope would initiate a back release. The angle required, reliability, tendency for unintended operation,and whether or not this would actually work, to be determined by testing. Based on something like this that was attempted and reported on here earlier, I have a low confidence in this scheme working out.
2: Using a TOST release, add an electric solenoid activation device somewhere 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 plane, the normal manual pull handle in the cockpit, or a switch on the stick. Again, testing would have to be done to confirm that this scheme would actually 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 impossible. 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.

[Brian]

That might be the scenario to build an auto release. it would require an electronic gyro which any more is inexpensive and easy to implement along with the full back stick switch, if the Tow plane pitches down more than a certain amount (Maybe 20 degrees down pitch) and with full aft stick initiates and auto release.

Brian

[clint....@gmail.com]

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/viewtopic.php?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

[Pieter Oosthuizen]

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

http://www.glidingmagazine.com/pdfs/Chris%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

[Chris Rollings]

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
>

[Chris Rollings]

At 03:57 18 February 2014, Brian wrote:
>That might be the scenario to build an auto release. it would require an

>el=

>ectronic gyro which any more is inexpensive and easy to implement along

>wit=

>h the full back stick switch, if the Tow plane pitches down more than a

>cer=

>tain amount (Maybe 20 degrees down pitch) and with full aft stick

>initiates=
> and auto release.
>
>Brian
>

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.

[Chris Rollings]

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.

[Pieter Oosthuizen]

Thanks Chris - appreciate your comments! :)

Apologies if I interpreted it incorrectly.

PO

[Don Johnstone]

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.

[herbk...@gmail.com]

It occurred to me that attaching the tow rope to the tug near the center of gravity (top of turtle deck on a Pawnee for example) would make kiting a non-event. That's how all the RC gliders are towed since you cannot control the position of the glider really well in relation to the towplane while standing on the ground. Interference of the tow rope with rudder and elevator does not seem to be a problem for RC fliers.

[C-FFKQ (42)]

On Tuesday, 18 February 2014 11:25:24 UTC-5, herbk...@gmail.com wrote:
> On Tuesday, February 18, 2014 7:17:16 AM UTC-6, Don Johnstone wrote:
>
> It occurred to me that attaching the tow rope to the tug near the center of gravity (top of turtle deck on a Pawnee for example) would make kiting a non-event. That's how all the RC gliders are towed since you cannot control the position of the glider really well in relation to the towplane while standing on the ground. Interference of the tow rope with rudder and elevator does not seem to be a problem for RC fliers.

Um... wouldn't that cause a great risk of fouling the tail feathers of the tug? No more "boxing the wash".

[Don Johnstone]

At 16:41 18 February 2014, C-FFKQ 42 wrote:
>On Tuesday, 18 February 2014 11:25:24 UTC-5, herbk...@gmail.com wrote:
>> On Tuesday, February 18, 2014 7:17:16 AM UTC-6, Don Johnstone wrote:

>>=20

>> It occurred to me that attaching the tow rope to the tug near the
center

>=

>of gravity (top of turtle deck on a Pawnee for example) would make kiting

>a=

> non-event. That's how all the RC gliders are towed since you cannot

>contr=

>ol the position of the glider really well in relation to the towplane

>while=

> standing on the ground. Interference of the tow rope with rudder and

>elev=

>ator does not seem to be a problem for RC fliers.
>
>
>Um... wouldn't that cause a great risk of fouling the tail feathers of
the

>=

>tug? No more "boxing the wash".

OK here is a whacky idea. A V shaped boom with the point to the rear of the
rudder, the release mounted at this point. The two front points mounted to
a pivot, through the fuselage above the wing, near the CoG. The V
arrangement can pivot up, but not down. The space between the arms has to
be sufficient to allow full rudder. Would only work for low wing
monoplanes.

[kirk.stant]

On Tuesday, February 18, 2014 1:50:52 PM UTC-7, Don Johnstone wrote:

> OK here is a whacky idea. A V shaped boom with the point to the rear of the
>
> rudder, the release mounted at this point. The two front points mounted to
>
> a pivot, through the fuselage above the wing, near the CoG. The V
>
> arrangement can pivot up, but not down. The space between the arms has to
>
> be sufficient to allow full rudder. Would only work for low wing

> monoplanes.

Well as long as were are drawing on envelopes, how about a bridle attached to each wingtip of the towplane, with the towhook at the apex of the bridle, able to slide side to side (to prevent rudder stalls) while the bridle pivots up during kiting so the force just pulls the towplane higher! To drop the glider, release one end of the bridle and the towhook just slips off.

Or just teach the stupid glider pilot to fly the correct tow position!

Of course, a good winch solves this problem nicely....

Kirk

[uncl...@ix.netcom.com]

On Tuesday, February 18, 2014 6:56:56 PM UTC-5, kirk.stant wrote:
> On Tuesday, February 18, 2014 1:50:52 PM UTC-7, Don Johnstone wrote: > OK here is a whacky idea. A V shaped boom with the point to the rear of the > > rudder, the release mounted at this point. The two front points mounted to > > a pivot, through the fuselage above the wing, near the CoG. The V > > arrangement can pivot up, but not down. The space between the arms has to > > be sufficient to allow full rudder. Would only work for low wing > monoplanes. Well as long as were are drawing on envelopes, how about a bridle attached to each wingtip of the towplane, with the towhook at the apex of the bridle, able to slide side to side (to prevent rudder stalls) while the bridle pivots up during kiting so the force just pulls the towplane higher! To drop the glider, release one end of the bridle and the towhook just slips off. Or just teach the stupid glider pilot to fly the correct tow position! Of course, a good winch solves this problem nicely.... Kirk

The Dragonfly towplane for hang & ultralite gliders uses a bridle attached above the top of the rudder and just below the bottom of the rudder, withbthe tow rope free to ride up and down on the bridle. Hang gliders sometimes get way out of shape, but the tug isn't affected.
UH

[Martin Gregorie]

From what I know of model aircraft I suspect, but can't prove it, that
the fin on an RC model is (relatively) considerably stronger than the fin
on a towplane. Structurally, most RC model fins are either solid balsa
sheet or a foam-filled fibreglass moulding. If its a sheet balsa fin its
almost guaranteed to be a lot harder and denser than I'd ever use on a
model I was building myself.

An RC model can be dumped on the strip in a manner that would wreck any
GA aircraft. They are very frequently landed this way. Rounding out? Whats
that? Land the model badly on grass enough to flip it over onto its back
and the fin is almost guaranteed to be undamaged. Could you say the same
about a typical towplane's fin?



--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Surge]

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

[Chris Rollings]

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.

[Don Johnstone]

It is clear from what we have seen on this thread that we have identified
an occurrence which has resulted in the death of tug pilots. If we do
nothing tug pilots will continue to be killed and the question is, "Are we
resigned to classing these future deaths as a normal operating hazard?" For
my part I would not be particularly comfortable with this, especially as I
could be the pilot on the back.

We have established, thanks to Chris that the event, from start to finish,
happens over a very short period. He estimates 2 - 3 seconds and I have no
reason to doubt this assessment. Chris is a very experienced pilot of both
gliders and tugs and he further states that once the event starts it is
unlikely that either pilot can react in time to prevent a predictable
outcome. That predictable outcome is the tug pointing vertically at the
ground at full throttle. The only unknown in any of these events is whether
or not there is sufficient height for the tug pilot to recover from this
situation before the ground gets in the way. If there is insufficient
height the tug pilot is going to die.

There has been much discussion concerning an auto release mechanism. Chris
has said that he does not think that a mechanical "angle detection" system
would work in time, I concur with that view. The problem is not just the
height above the tug that the glider reaches but the rate of change in
height. It has been suggested that by the time the glider has reached the
height behind the tug to cause a problem it is too late to do anything
about it.

There is one possibility, measurement of the rate of change in height
relative to the tug. The technology for this exists and is abundant, we see
this every day in the boxes on the side of the road, I speak of course of
speed cameras. It would not be difficult to have a device that operated the
release if there was a rate of change in excess of what we consider normal.
You could even take two measurements or more to detect an increasing rate
of change (Unsafe) to a decreasing rate of change (Less Unsafe). The device
would trigger the release instead of the camera. Ideally this would be
mounted in the glider but given the cost implications it would be
acceptable in the tug. There is an opportunity to give the glider the rope
before the tug gets into an irrecoverable situation.

This would not be cheap, and I am sure there are other options we have yet
to discover, but is the option of doing nothing acceptable? We do not know
the cause of this occurrence in every case, we do know the effect and the
outcome. We do know the factors that are likely to contribute to the cause,
for example CoG hooks, but addressing this alone, as Chris has pointed out,
is not the complete answer. We are left with mitigating the effects and I
think we owe it to the people who provide our tows to do all we can.

Lastly I would like to thank Chris Rollings for sharing his research.
Without his work we would be dealing with theories, which are less
compelling than real results.

[Brian]

I think the Gyro, and full back stick switch has some potential but has some issues, such as calibrating the Gyro, and possible Test/fault issues that would need to be overcome.

Another one to consider would be a time delay switch on the Throttle. Once the throttle has been set to climb power for more than say 5 seconds (time might need to be adjusted) then if the stick is moved to full aft, a release is initiated.
The throttle delay is to prevent releases during the 1st part of the ground roll. I can't think of any other time when the tow plane would have full back stick and full throttle that the pilot would not want the glider to be released. One advantage of this system is that the tow pilot should know this combination will cause a release and bring a higher awareness to the possibility of the glider kiting.

Another issue to be addressed by either of these systems is that it will require a powerful actuator to ensure a release actually occurs when needed.

Just brain storming some idea's

Brian

[son_of_flubber]

On Tuesday, February 18, 2014 1:48:05 AM UTC-5, clint....@gmail.com 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/viewtopic.php?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.

[Steve Leonard]

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

[uncl...@ix.netcom.com]

On Wednesday, February 19, 2014 7:36:56 PM UTC-5, Steve Leonard wrote:
> 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

The least expensive improvement that many operations can make immediately is to adopt the use of longer tow ropes.The effect of pilot error is drastically reduced by this one simple change. Many places I fly as guest use ropes that are marginally short as matter of standard practice.
We try not to use ropes shorter than 200 ft.
UH

[Steve Leonard]

On Wednesday, February 19, 2014 8:08:24 PM UTC-6, uncl...@ix.netcom.com wrote:
> The least expensive improvement that many operations can make immediately is to adopt the use of longer tow ropes. The effect of pilot error is drastically reduced by this one simple change. Many places I fly as guest use ropes that are marginally short as matter of standard practice. We try not to use ropes shorter than 200 ft. UH

Same practice at Sunflower Gliderport. (my home base)

Steve

[t...@serkowski.com]

How about mounting a camera on the towplane that's keeping an eye on the glider. If the vertical position exceeds some predefined rate of change, the release is pulled.

Got this idea from this story:
http://www.gizmag.com/air-hockey-table-3d-printer-parts/30840/

A camera is mounted above an air hockey table and software is able to track the puck and use that information to drive a paddle to return pretty much all incoming shots.

To test this out one only needs to mount a camera on a busy towplane to collect lots of "normal" operations as well as some simulated kiting scenarios. Then some smart person could analyze the video to see if it's possible write some code to effectively track the glider.

The big question is whether a kite is detectable early enough, and different from normal operations.

-Tom

[Chris Rollings]

At 02:08 20 February 2014, uncl...@ix.netcom.com wrote:
>On Wednesday, February 19, 2014 7:36:56 PM UTC-5, Steve Leonard wrote:
>> Chris has hit the nail on the head with his testing and reporting. When

>i=

>t goes wrong, it goes wrong fast. Faster than you can possibly react. We

>ca=

>n 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

>crea=

>ting 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

>wr=

>ong. Would you agree? On tow, elevator is up, nose is up. On descent,

>eleva=

>tor is down, nose is down. Why not develop and test a parallel releasing

>sy=

>stem 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
>
>The least expensive improvement that many operations can make immediately

>i=

>s to adopt the use of longer tow ropes.The effect of pilot error is

>drastic=

>ally reduced by this one simple change. Many places I fly as guest use

>rop=

>es that are marginally short as matter of standard practice.
>We try not to use ropes shorter than 200 ft.
>UH
>

The tests I described were done with ropes about 180 feet long, I think it
would probably need ropes of 400 feet or more to give sufficient time for
there to be even a chance of releasing in time if a kiting event started.
There are practical reasons for not using ropes that long at most sites.

[Chris Rollings]

I had a quick look at BGA statistics for 1997 (probably a fairly
representative year in the long term), approx 104,000 aerotows. I think we
have only had about four kiting fatalities in the UK, in the last 40 years
(I'd be pleased if someone with access to the stats could check that, I'm
relying on fallible memory). That makes the kiting fatality approx a one
in a million event.

Of the various automatic releases proposed, I can forsee two possible
problems, one is a glider mounted automatic release being unintentionally
activated for a winch launch and giving the glider a launch failure at the
moment it starts to rotate into the full climb (might be pilot error or
switching failure that caused it to be activated). The second is for a
tow-plane or glider mounted one dumping an innocent glider at an early
stage of the tow, this is potentially very dangerous as the land ahead
option often doesn't exist between 50 feet and 300 feet, which necessitates
turning at very low altitude, the commonest cause of spin-ins.

It would take an exceptionally reliable automatic release to be sure that
the launch failure fatal accidents caused by its malfunction came out as
less than one in a million launches.

Please don't misunderstand, I am not arguing against attempts to develop
such a mechanism, just trying to make sure there is understanding of the
degree of reliability needed.

At 02:50 20 February 2014, t...@serkowski.com wrote:
>How about mounting a camera on the towplane that's keeping an eye on the

>gl=

>ider. If the vertical position exceeds some predefined rate of change,

>the=

> release is pulled.
>
>Got this idea from this story:
>http://www.gizmag.com/air-hockey-table-3d-printer-parts/30840/
>
>A camera is mounted above an air hockey table and software is able to

>track=

> the puck and use that information to drive a paddle to return pretty
much

>=

>all incoming shots.
>
>To test this out one only needs to mount a camera on a busy towplane to

>col=

>lect lots of "normal" operations as well as some simulated kiting

>scenarios=
>.. Then some smart person could analyze the video to see if it's
possible
>w=

>rite some code to effectively track the glider.
>
>The big question is whether a kite is detectable early enough, and

>differen=
>t from normal operations.
>
>-Tom
>

[Hans Heydra]

Hi Guys
Just read through the last 66posts on this page. After what happened here
in South Africa this week I though something needs to be done. I was
thinking along the lines of a tilt switch. Whilst noodeling I cam across a
UK company see...
http://www.leveldevelopments.com/products/inclinometers/tilt-switches/
and what they did for another company.
http://www.leveldevelopments.com/case-studies/blast-and-roll-sensor-for-emergency-lighting-system/
This really stood out....
**The final sensor was a custom solution comprising a three axis
accelerometer and 3 axis tilt sensor. The tilt sensor used a customized
filter algorithm to ensure the dynamics of the vehicle in use did not cause
false alarms.**

This system can be tested a low initial cost with a light on the tug pilots
dashboard every time it is triggered to iron out false alarms.

Only thing you need is a tilt switch. With a safety ON and OFF.
Basically before the tug the pilot turns "ON" the tilt switch switch then
proceeds with the tug. If the tug is pulled into a **30 degree dive the
tilt switch is activated and drops the rope automatically through a yet to
be worked out system.(Could be explosive, pneumatic or some other method)
Once the glider pilot has released (under normal gliding conditions) the
switch is turned "OFF" by the tug pilot so it will not be deposited over
some farm field when the tuggie dives back to the field at **30 degrees.

**30 degrees is an example could be 25, 35, 40 Tests would have to be done.

[Chris Rollings]

To repeat one point, our tests left us convinced that the tail-plane on the
tow-plane stalled quite early on in the kiting event, it would need some
tests to check exactly how early. It might be that the nose down angle
would have to be quite small, something that could happen in turbulence
perhaps.

[Evan Ludeman]

On Thursday, February 20, 2014 9:36:03 AM UTC-5, Chris Rollings wrote:

>
> To repeat one point, our tests left us convinced that the tail-plane on the
>
> tow-plane stalled quite early on in the kiting event, it would need some
>
> tests to check exactly how early. It might be that the nose down angle
>
> would have to be quite small, something that could happen in turbulence
>
> perhaps.

That's a pretty interesting (and gut wrenching to this tow pilot) point Chris.

Stall warning flipper on the horizontal? Feasible?

-Evan Ludeman / T8

[kirk.stant]

The more I think about it I think we are going down the wrong path. Move the tow-hook to the CG of the towplane and the problem pretty much goes away.

Back to some sort of bridle from the wingtips so any pulling vector is through the CG (or close).

Or an "outrigger" on each side of fuselage sticking out far enough for the bridle to clear the tail, again installed close to the CG. That might be an easier structural solution, but the geometry would make the outriggers pretty long!

Kirk
66

[Steve Leonard]

Just looking to properly understand and maybe differently explain the dynamics of the situation, Chris. What you described before was:

"Third test: Terrier Tow-Plane, K 8b on C of G hook. I pitched the glider about 25 degrees nose up. The glider continued to pitch up fairly rapidly (as at the start of a winch launch) and substantial forward movement of the stick only slightly slowed the rate of pitch. The glider achieved about 45 degrees nose up, speed increased rapidly from 55 knots to about 75 knots and the glider was pulled back towards level flight (again as at the top of a winch launch). I released at that point. The entire sequence of events occupied a VERY short period of time (subsequently measured as 2 - 3 seconds). The Tow Pilot reported a marked deceleration and start of pitching down which he attempted to contain by moving the stick back; this was followed immediately by a very rapid pitch down accompanied by significant negative "G". The tow-plane finished up about 70 degrees nose down and took about 400 feet to recover to level flight. We both found the experience alarming, even undertaken deliberately at 4000 feet. Our conclusion was that the combination of the initial pitch down and the upward deflection of the elevator caused the horizontal stabilizer/elevator combination to stall and the abrupt removal of the down-force it provided caused the subsequent very rapid pitch-down and negative "G"."

Not to be to "chicken or egg" here, but, I don't think the horizontal tail of the towplane stalled. I think the glider provided an upward force, creating a nose down pitching moment far greater than the elevator could counter (obviously, right?). Once the glider has pitched the plane sufficiently nose down, the wing of the towplane is actually pushing DOWN (even though the pilot is pulling the nose up), hench the negative g felt in the towplane. The glider wing on its long moment arm can produce a far greater pitching moment than the horizontal tail on its short moment arm. The towplane transitions from steady, upright, one g flight, to negative g doward arcing flight because the glider changes the angle of attack of the wing of the towplane from positive to negative.

Your pictures taken later show this is likely. The glider has a large pitch change before it starts its vertical displacement. Similarly, the towplane will get a large pitch change nose down before it starts to deviate from its climbing or level flight path. And it will happen so rapidly, the pilot will not be able to tell if it happened because he pulled back and the tail stalled, or because the glider created such a large nose down pitching moment. I strongly suspect the results would be the same if the towpilot did nothing to try and keep the nose up in the CG hook kiting event. Glider pitches towplane, towplane responds due to lift vector changing magnitude initially, then direction.

We know that this event does not happen often, but when it does, it often has catastrophic results. I don't think there is a practical way to attach the rope to the CG of the towplane. So, we are left with training (which we have seen does not eliminate the problem) or some sort of automatic system (since it has been documented that it is unlikely a pilot can react fast enough to be able to save his or her own life if it goes really bad).

Time to start working on a secondary pull system (sorry, Kirk. No explosive bolts or missles. Would be more fun, though.) using attitude and elevator positon. Or maybe attitude and pitch rate. Need to keep it as simple (fewest inputs and software) as possible. I do like the idea of initial tests of set values to turn on a light in the cockpit for the pilot to see that the automatic system will have operated. Got any reasons not to start at 10 degrees nose down pitch attitude and half way to max nose up elevator travel?

Steve Leonard

[kirk.stant]

On Thursday, February 20, 2014 1:21:58 PM UTC-6, Steve Leonard wrote:
>
> Time to start working on a secondary pull system (sorry, Kirk. No explosive bolts or missles. Would be more fun, though.) using attitude and elevator positon. Or maybe attitude and pitch rate. Need to keep it as simple (fewest inputs and software) as possible. I do like the idea of initial tests of set values to turn on a light in the cockpit for the pilot to see that the automatic system will have operated. Got any reasons not to start at 10 degrees nose down pitch attitude and half way to max nose up elevator travel?

No pyrotechnics? How are we going to grow the sport without pyrotechnics (and a TV reality show...).

How about:

1. Tow gliders vertically with helicopters (It's been done..)
2. Have the towplane push the glider with a reverse towbar setup.
3. Mount the glider on top of the towplane - space-shuttle/747 style.
4. Two words: Electromagnetic catapults.
5. Automatic BRS on towplane triggered by sudden pitch-down.
6. Custom design towplane made from 2 Pawnee fuselages, F-82 style; would make it easy to mount tow hook near CG on center wing.
7. "Tail-gunner" facing backwards in towplane with both hands on tow release. Better not piss that guy off before you launch!
8. Use F8F Bearcats for towplanes - they would climb so steeply that if the glider kited, it would only level off the towplane (and then the glider's wings would come off as you accelerated through glider's Vne - Better release quick!).
9. Use webcam on tail of towplane to track glider and release him when he gets out of position (displacement, rate, or combination of both). As added incentive, use bluetooth to set off smoke bomb in glider cockpit if release is triggered.
10. Take all glider pilots up in a two-seat towplane (with a briefed student and instructor in the glider) and at a safe altitude demonstrate what an upset looks and feels like from both ends of the string.

I like #8, myself, but I think #10 would work pretty darn good.

Kirk
66
Tuggie

[Martin Gregorie]

On Thu, 20 Feb 2014 09:55:38 -0800, kirk.stant wrote:

> The more I think about it I think we are going down the wrong path.
> Move the tow-hook to the CG of the towplane and the problem pretty much
> goes away.
>
> Back to some sort of bridle from the wingtips so any pulling vector is
> through the CG (or close).
>

I'm sure that would work well in the air, but isn't there a potential
problem during the landing roll-out? With no tension on the tow rope it
seems to me that you've got a U-shaped loop of rope dragging on the
ground behind the tow plane which would provide considerable drag on a
grass field if it isn't recently mown. Would this also be a problem at
the start of the take-off roll?

[Don Johnstone]

At 14:36 20 February 2014, Chris Rollings wrote:

>To repeat one point, our tests left us convinced that the tail-plane on
the
>tow-plane stalled quite early on in the kiting event, it would need some
>tests to check exactly how early. It might be that the nose down angle
>would have to be quite small, something that could happen in turbulence
>perhaps.
>

Which is why I suggested speed camera technology to detect a faster than
normal rapid climb of the glider in relation to the tug. Measuring the
height or even the angle is just not going to give the system time to work.
Detecting the rapid vertical acceleration early will do that. Even if the
pilot in the glider detects the early acceleration, inertia probably means
that he will be unable to correct in time.

[Colin Wray]

This is correct, except that the duration can be sub one second. Your
only possible reaction is to shut the throttle. I am sure you can use
today's technology to detect the effect, but certainly not the cause.

[Colin Wray]

Full back stick is not a parameter. If it occurs at all it is after
the event. On the other hand, full back stick can be reached in non
life-threatening situations.

[Colin Wray]

Most people posting here do not understand the word "instantaneous".
Chris Rollings, and the CofG hook exponents, are the only people who
get it.

[mark...@gmail.com]

Here's another idea that probably has something wrong with it.
Attach the tow rope to c/g, maybe the turtle deck and have a fair
lead at the tail which releases at the tail only under some set of unfavorable circumstances.

The glider can zoom without upsetting the tow plane nor will the glider be underemoniously dropped in turbulence.

Not sure about fouling the tail feathers with the tow rope.

[son_of_flubber]

On Thursday, February 20, 2014 9:36:03 AM UTC-5, Chris Rollings wrote:

> To repeat one point, our tests left us convinced that the tail-plane on the
> tow-plane stalled quite early on in the kiting event, it would need some
> tests to check exactly how early. It might be that the nose down angle
> would have to be quite small, something that could happen in turbulence
> perhaps.

1)It might be possible to recognize a pattern of stick movements and vertical acceleration (and possibly AOA and position relative to the tug) in the GLIDER that would provide a high confidence signature of an imminent kiting event prior to upsetting the tug. The fatal control input is made by the pilot a second or two before the glider kites. Perhaps stage one would trigger an alarm and stage two would trigger a release.

Discovery of the 'kiting signature' would be based on analysis of detailed logs of normal tows, including tows in severe turbulence. Logs would include the parameters noted above and perhaps a video of the tug from the glider. The release device might have three modes 1)normal turbulence 2)severe turbulence mode with higher threshold 3)alarm only mode with simulated release tone. AGL and distance to landable area might lower the release threshold.

Mode 3 would allow me to confirm calibration of the device to my particulars and to gradually increase glider pilot confidence in the device. If it were based on sound science and engineering, I would install a device like this on my glider to reduce my chances of killing a tow pilot even if it somewhat increased my risk of an unwarranted release. Kiting is rare, but I would rather die than possibly kill a tow pilot (especially a young one). I would take my chances on a sound device.

I know that this approach sounds sophisticated, but we live in a time of rapidly advancing technology and dropping costs. There are some good starting points that might only require software extensions once the 'kiting signature' is known, see http://www.diydrones.com/notes/ArduPilot

2)The clubs that I know find it nearly impossible to build a consensus about the most simple and inexpensive things, let alone an automatically activated tug hook. Spend money on a 1:1000000 chance?? There are also good arguments against an auto-release tug hook that might lead to the death of a glider pilot in a hard to justify/defend scenario. Lawyers would have a field day in the USA. Deployment would be spotty and slow. Lots of 'wait and see' decisions. On the hand, I could put a device on my glider and the question would be settled for me behind 100% of tugs.

3)What happens in rotor? Is it possible to stall the horizontal stabilizer of the tow plane? Perhaps it would be good to automatically released in severe rotor, especially if my AGL and distance to a landable spot were within predefined limits. Someday I think I might stay on tow in rotor longer than I should. A mode 3 alarm might provide timely and objective advice to the pilot in rotor. The device could confidently detect inverted flight on tow and auto-release immediately.

4)If you had this kind of sensor and computation power in a glider, it could detect and warn of things like 'imminent spin on turn to final' and other mistakes. Once you had the hardware platform installed a lot of useful safety features could be added.

[Steve Leonard]

On Thursday, February 20, 2014 5:48:43 PM UTC-6, Colin Wray wrote:
> Most people posting here do not understand the word "instantaneous". Chris
> Rollings, and the CofG hook exponents, are the only people who get it.

Glad to see you chose my post to respond to when you decide to imply that most of us (myself included) don't know what "instantaneous" means, Colin. I work a lot with electrical guys and your idea of "instantaneous" is an eternity to them. Half a second? That is a lifetime in the world of electrical system responses. I work with regulations and know about human reaction times. I know that the event being discussed will go from start to disaster in less than typical event to recognition to reaction time. Even for someone who is expecting it and knows exactly when it starts.

I understand the dynamics of it at least as well as you do. Maybe better. I know that cambered wing sections can generate higher C/L max than symmetric sections. I know what a C/L versus Alpha curve is. I know its slope. I can tell you what it takes in terms of AOA change to go from 1 g to minus 1 g. I know that a wing that is 5 times the size of the tail on the towplane, and attached to the towplane via the tow rope roughly 20 times further back from the towplane aerodynamic center than the tail will be able to produce more than 30 times the pitching moment to the towplane than the tail on the towplane can. I know that if the glider does this, there is NO way the towplane pilot can do anything to stop it. Again, I don't think the tail on the towplane stalls. I think the glider effectively becomes the "tail" of the tug, and it can and does overpower anything the elevator might do.

I agree that a system based on angular displacement of the rope likely won't work, as the relative angle between the two planes doesn't change much and you can slowly go higher than this and not cause a problem to the tug. Longer ropes can damp the response, but not eliminate it. I read what Chris wrote, and I get it. I get it that you can do this and not break a proper strength rope. You have once again assumed that because someone is proposing an automatic system to try and minimize (notice, I know I can NOT prevent it) the impact, you assumed that "he doesn't get it".

Design thoughts. When is a towplane nose down? In an upset or on descent. If the towplane is in its descent, where is the elevator? It certainly won't be more than half way to full nose up! It might be a quarter to half way up during a normal tow, but the nose will not be below the horizon. And if a kiting event starts, the towpilot will no doubt start pulling back. What I have proposed is a starting point for evaluation of an automatic system to MINIMIZE the risk to the tuggie in the event of kiting. I strongly suspect that 10 degrees nose down is too much, as the tug will already have gone negative load factor, and the event must be stopped before then. But, I am proposing a starting point.

Have you got a better proposal for a starting point for a system to MINIMIZE the risk to the tuggie? In case you are wondering, autothrottle won't Minimize it. :-)

End of rant.

Steve Leonard

[Chris Rollings]

Steve, that's a very good hypothesis, could well be right, it certainly
fits the facts as well as the conclusion we reached did. Fit an angle of
attack indicator to a tow-plane and go and try it.

At 20:21 20 February 2014, kirk.stant wrote:
>On Thursday, February 20, 2014 1:21:58 PM UTC-6, Steve Leonard wrote:

>>=20

>> Time to start working on a secondary pull system (sorry, Kirk. No

>explos=

>ive bolts or missles. Would be more fun, though.) using attitude and

>eleva=

>tor positon. Or maybe attitude and pitch rate. Need to keep it as
simple

>=

>(fewest inputs and software) as possible. I do like the idea of initial

>te=

>sts of set values to turn on a light in the cockpit for the pilot to see

>th=

>at the automatic system will have operated. Got any reasons not to start

>a=

>t 10 degrees nose down pitch attitude and half way to max nose up
elevator

>=

>travel?
>
>No pyrotechnics? How are we going to grow the sport without pyrotechnics

>(a=

>nd a TV reality show...).
>
>How about:
>
>1. Tow gliders vertically with helicopters (It's been done..)
>2. Have the towplane push the glider with a reverse towbar setup.
>3. Mount the glider on top of the towplane - space-shuttle/747 style.
>4. Two words: Electromagnetic catapults.
>5. Automatic BRS on towplane triggered by sudden pitch-down.
>6. Custom design towplane made from 2 Pawnee fuselages, F-82 style; would

>m=

>ake it easy to mount tow hook near CG on center wing.
>7. "Tail-gunner" facing backwards in towplane with both hands on tow

>releas=

>e. Better not piss that guy off before you launch!
>8. Use F8F Bearcats for towplanes - they would climb so steeply that if

>the=

> glider kited, it would only level off the towplane (and then the
glider's

>=

>wings would come off as you accelerated through glider's Vne - Better

>relea=

>se quick!).
>9. Use webcam on tail of towplane to track glider and release him when he

>g=

>ets out of position (displacement, rate, or combination of both). As

>added=

> incentive, use bluetooth to set off smoke bomb in glider cockpit if

>releas=

>e is triggered.
>10. Take all glider pilots up in a two-seat towplane (with a briefed

>studen=

>t and instructor in the glider) and at a safe altitude demonstrate what
an

>=

[GC]

On 21/02/2014 06:21, Steve Leonard wrote:
>
> Not to be to "chicken or egg" here, but, I don't think the horizontal
> tail of the towplane stalled. I think the glider provided an upward
> force, creating a nose down pitching moment far greater than the
> elevator could counter (obviously, right?).

Mmm. ...and how would that differ from a stalled tailplane? Isn't it
the same as an accelerated (>1g) wing stall?

> We know that this event does not happen often, but when it does, it
> often has catastrophic results. I don't think there is a practical
> way to attach the rope to the CG of the towplane. So, we are left
> with training (which we have seen does not eliminate the problem) or
> some sort of automatic system (since it has been documented that it
> is unlikely a pilot can react fast enough to be able to save his or
> her own life if it goes really bad).

Experience shows that training NEVER eliminates problems but can reduce
a problem's frequency to acceptable levels. Kiting is already a very
rare event as another poster (Chris himself, IIRC) showed and this is
largely due to training.

Experience also shows that automation may eliminate a problem but also
produces failure cases (which must, in any case, be trained for).
Further, as Air France's A330 showed, automation almost always means
that pilots aren't as good at dealing with the problem as they would be
if they knew their training was the only thing stopping the accident.

No. In this case, well-trained, alert glider and tug pilots are the
cost-effective solution to the problem. The automated release is pie in
the sky.

GC

[GC]

On 21/02/2014 11:16, son_of_flubber wrote:

... snips

> 3)What happens in rotor? Is it possible to stall the horizontal
> stabilizer of the tow plane? Perhaps it would be good to
> automatically released in severe rotor, especially if my AGL and
> distance to a landable spot were within predefined limits. Someday I
> think I might stay on tow in rotor longer than I should. A mode 3
> alarm might provide timely and objective advice to the pilot in
> rotor. The device could confidently detect inverted flight on tow
> and auto-release immediately.
>
> 4)If you had this kind of sensor and computation power in a glider,
> it could detect and warn of things like 'imminent spin on turn to
> final' and other mistakes. Once you had the hardware platform
> installed a lot of useful safety features could be added.

Are you an Airbus engineer?

GC

[kirk.stant]

On Thursday, February 20, 2014 1:31:56 PM UTC-7, Martin Gregorie wrote:

> > Back to some sort of bridle from the wingtips so any pulling vector is
>
> > through the CG (or close).
>
> >
>
> I'm sure that would work well in the air, but isn't there a potential
>
> problem during the landing roll-out? With no tension on the tow rope it
>
> seems to me that you've got a U-shaped loop of rope dragging on the
>
> ground behind the tow plane which would provide considerable drag on a
>
> grass field if it isn't recently mown. Would this also be a problem at
>
> the start of the take-off roll?

Well, you could make the bridle in two pieces that connect at the release, and come apart when the glider is released; you would now have a long towrope trailing one wingtip and a short one trailing the other.

Starting to get more complicated, of course...

Kirk

[Terry Slater]

Lots of good ideas, but some of the dynamics of a tug upset has been
missed. Chris Rollings mentioned the loads in the rope rapidly increasing
from c50lbs to over 700lbs as the glider assumes a winch launch attitude.
This load on the tug will RAPIDLY slow it down, thus losing flying speed.
So not only does the glider climb, the tug descends with rapidly falling
airspeed, and the elevator becoming ineffective. As the ug loses speed it
will pitch nose down anyway.

Chris also mentioned a very strong deceleration, and I can vouch for this
when a K6E kited behind me on a tow at Aboyne. The K6 pilot missed the
release toggle due to wearing gloves, and had already started his climbing
turn. He realised his mistake and releassed the rope, by which time I was
steeply nose down with little airspeed, albeit at 4000 feet! I was
effectively a passenger during the upset, but interestingly did not lose
sight of the glider in the tug mirror, showing the tail was NOT pulled up.
I have always been very wary of tugging gliders on belly hooks since!

Terry Slater

[Steve Leonard]

Terry, the dynamic of the towplane slowing was not lost on me. The only source for the kiting energy of the glider is the tug. Any climb rate for the glider above that being provided by the engine of the tug will come out of the tug in the form of lost airspeed. That is probably the first thing the towpilot will notice. But, the same loss of speed could occur as a result of the glider's powerful dive brakes openning, so that cannot be used as a trigger for an auto system. Also, slowing the tug will not make it pitch down, unless the slowing is to below the stall speed of the tug. It will make it start to drop, as lift is now less than weight. And, Terry, if you were nose down, your tail likely was pulled up. In an amount that kept the glider in your mirror. Your airpseed loss was the transfer of your kinetic energy to the increased kinetic and potential energy of the glider. The nose down was likely a combo of the glider pulling your tail up and possibly stalling of the wing of the tug. You effectively became a moving anchor point for the glider.

GC, stalled tail and accelerated stalls are not at all the same. Maybe you need some training? :-) My belief is that a kiting glider with a wing that is 3-5 times the size of the tugs tail can provide far greater tug pitch authority than the tail on the tug. You don't have to stall the tug's tail in order to produce more force with something else than it can produce.

You can test the stalled tail theory by flying the tug sans glider at tow speed. Push the stick rapidly forward to create the nose down pitch rate, then pull rapidly back to arrest it. If the stick back pull does not stop the nose down pitch, the tail was stalled. If it does, the tail is not stalled. This may not be the case for an aerobatic plane intentionally doing an outside snap.

As to "well trained glider pilots", ask Terry about the "well trained pilot" he was tugging who thought he pulled the release, so he started his climbing turn away. Well trained or not these things do happen. Not often, but they do happen. And when they happen at low altitude, the result is usually fatal. First step in training is to burn it into the heads of all glider pilots that on air tow, you don't even consider turning away from the towplane until you have seen the rope going away. Amazingly simple but forgotten more than most would imagine.

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? :-)

Mark, fairleads over the tail have issues, too, as boxing the wake will quickly show. But, maybe the air load and the pull of the rope in the other direction will sort of cancel, and not risk bending the fin? However, if there is restriction to up or down pull, you have lost the benefit.

As to other failure modes of an automatic system and the "need to train for them", well, don't we already train for rope breaks? If the system is designed well, it won't make a disconnect any more likely than it is now. And, it is not a change to the airframe, but only an additional means of operating the release. I tend to think that this would be much easier to certify, once you have shown sufficient reliability of the system by design, and that it does not substantially increase the risk of an unplanned seperation of the tug and the glider in practice.

So, with what we have available to us today, why are we afraid to try and design a system to reduce this risk?

Steve Leonard

[kirk.stant]

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 Marotta]

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" <kirk....@gmail.com> wrote in message
news:6a3e8816-efc9-4ab2...@googlegroups.com...

[Jonathon May]

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 .
>

[Steve Leonard]

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

[howard...@gmail.com]

Per Steve's comment that the only energy for the glider comes from the towplane engine I have a comment which is in many ways a request for enlightenment.
I had a kiting incident at Moriarty in my 27. All worked out OK, other than fright, mostly because I got off quickly, just as the kite began. How it began is not very clear at all, and much of this is later rationalization I fear, best I can come up with. Skilled glider pilots who watched failed to come up with much, if anything, that helps.
Tow began normally. Within first few seconds, both still on the ground, the tow plane bobbled a bit -- nothing that much given that this was Moriarty on a nice strong thermal day. When I hit the place where the bobble happened the 27 popped into the air a few feet.
My explanation is that I made moves that exaggerated what followed. Anybody with better ideas please join in.
I pushed forward on the stick, the glider began to react, as I flew out of whatever it was caused the bobble, the glider sank fast towards the concrete, so I (rationalizing) assume I moved the stick back to ease the bump.
The glider bounced off the concrete, not that hard but bounced. The one thing I believe I truly remember is that there was a bit of a snake in the rope -- ie some slack.
The tow plane was of course accelerating. So (rationalizing) as the glider bounces up I have at best neutral stick, maybe a bit aft still, and the slack comes out of the rope and the glider at this point began the early stage of a winch launch.
I know that I did two things quickly -- one was hit the release, the other was to get the nose down. Once at flying speed, at maybe 30 feet (I don't have any real guesses from the observers), I moved to the right to use the taxiway. Then, when the tow plane came in sight going like stink out of my way down the runway, I moved back and landed on the runway.
Not a scratch, including to the tow plane's prop. Good towing Mike Stogner.
My point is that there can be a hell of a lot of energy in the rope if for some reason it gains a bit of slack and is then turned into an elastic band. For some strange reason weak links sometimes do not bust when they might be expected to ...






On Sunday, February 9, 2014 3:27:23 PM UTC-7, son_of_flubber wrote:
> This topic was buried in a drifting degenerate thread. I'm wondering if anyone knows more about the tow hook innovation mentioned below by UH.
>
>
>
> > On Saturday, February 8, 2014 9:31:13 AM UTC-5, son_of_flubber wrote:
>
> >
>
> > Why does the pilot need to pull the release if the glider kites? Why is the release for a deadly tow position not fully automatic? Is a simple purely mechanical, totally foolproof and 100% automatic release not possible? As the guy in the glider, I would be fine with a 100% automatic release. If I kite, release me immediately.
>
> >
>
>
>
> On Sunday, February 9, 2014 5:05:52 PM UTC-5, uncl...@ix.netcom.com wrote:>
>
> >
>
> > There was a design and prototype of a release like this created many years ago and published, I believe, in Soaring magazine. I know if no one that has adopted this which makes it fairly clear that this is not perceived as a huge problem.
>
> >

[Bob Whelan]

On 2/21/2014 3:23 PM, howard...@gmail.com wrote:
> Per Steve's comment that the only energy for the glider comes from the
> towplane engine I have a comment which is in many ways a request for
> enlightenment.

<Snip...>

> I pushed forward on the stick, the glider began to react, as I
> flew out of whatever it was caused the bobble, the glider sank fast towards
> the concrete, so I (rationalizing) assume I moved the stick back to ease
> the bump. The glider bounced off the concrete, not that hard but bounced.
> The one thing I believe I truly remember is that there was a bit of a snake
> in the rope -- ie some slack. The tow plane was of course accelerating. So
> (rationalizing) as the glider bounces up I have at best neutral stick,
> maybe a bit aft still, and the slack comes out of the rope and the glider
> at this point began the early stage of a winch launch. I know that I did
> two things quickly -- one was hit the release, the other was to get the
> nose down.

<Snip...>

> My point is that there can
> be a hell of a lot of energy in the rope if for some reason it gains a bit
> of slack and is then turned into an elastic band. For some strange reason
> weak links sometimes do not bust when they might be expected to ...

Ropes indeed can store significant strain energy. Compared to poly ropes,
nylon rope is akin to a rubber band. Is anyone in the U.S. still using nylon
towropes behind their tugs? Real fun for beginning students and instructors...!

As to how that energy got into the rope...I'm with Steve.

Your written assessment sounds entirely plausible to me. Good job dealing with
your unwanted surprise.

Bob W.

[Colin Wray]

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.

[Gilbert Smith]

Steve, I bow to your vatly superior knowledge of aerodynamics, and I
can now see that you really do 'get it'. (Sorry). I was basing my
comments on little more than my involvement in two of these episodes.

I guess that in real kiting accidents, where the rope remains
reasonably tight throughout, there will be a measurable time before it
becomes unrecoverable. My upset as the tug pilot featured a slack rope
which snapped tight, so any kiting must have been akin to a sling shot
for the glider.

[Don Johnstone]

At 22:23 21 February 2014, howard...@gmail.com wrote:
>Per Steve's comment that the only energy for the glider comes from the

>towp=

>lane engine I have a comment which is in many ways a request for

>enlightenm=

>ent.
>I had a kiting incident at Moriarty in my 27. All worked out OK, other

>tha=

>n fright, mostly because I got off quickly, just as the kite began. How
it

>=

>began is not very clear at all, and much of this is later rationalization

>I=

> fear, best I can come up with. Skilled glider pilots who watched failed

>t=

>o come up with much, if anything, that helps.
>Tow began normally. Within first few seconds, both still on the ground,

>the=

> tow plane bobbled a bit -- nothing that much given that this was
Moriarty

>=

>on a nice strong thermal day. When I hit the place where the bobble

>happen=
>ed the 27 popped into the air a few feet. =20

>My explanation is that I made moves that exaggerated what followed.

>Anybody=

> with better ideas please join in.
>I pushed forward on the stick, the glider began to react, as I flew out
of

>=

>whatever it was caused the bobble, the glider sank fast towards the

>concret=

>e, so I (rationalizing) assume I moved the stick back to ease the

bump.=20

>The glider bounced off the concrete, not that hard but bounced. The one

>th=

>ing I believe I truly remember is that there was a bit of a snake in the

>ro=

>pe -- ie some slack.
>The tow plane was of course accelerating. So (rationalizing) as the
glider

>=

>bounces up I have at best neutral stick, maybe a bit aft still, and the

>sla=

>ck comes out of the rope and the glider at this point began the early

>stage=
> of a winch launch. =20

>I know that I did two things quickly -- one was hit the release, the
other

>=

>was to get the nose down. Once at flying speed, at maybe 30 feet (I
don't

>=

>have any real guesses from the observers), I moved to the right to use
the

>=

>taxiway. Then, when the tow plane came in sight going like stink out of
my

>=

>way down the runway, I moved back and landed on the runway.
>Not a scratch, including to the tow plane's prop. Good towing Mike

>Stogner=
>..

>My point is that there can be a hell of a lot of energy in the rope if
for

>=

>some reason it gains a bit of slack and is then turned into an elastic

>band=
>.. For some strange reason weak links sometimes do not bust when they
might
>=
>be expected to ...

A while ago there was a discussion as to whether it was a good idea to have
one's hand on the release during the early stages of an aerotow as we do
for winching. I believe that we may have found a good reason for doing so.
It is clear from what everyone has said that it is vital that the glider
releases BEFORE it takes over the control of pitch on the tug, or at the
very least before the tug is pitched nose down. Searching for the release
may take more time than the tug pilot has. In most, if not all these
incidents the glider pilot survives.

On that note I do not think it is of any importance whether the tailplane
on the tug stalls or the glider overcomes the available power of the
elevator, the mechanism is not important, the important thing is that the
tug is pitched nose down so far that considerable height is needed for
recovery.

[GC]

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
>

[Alan]

In article <5308130c$0$29966$c3e8da3$5496...@news.astraweb.com> GC <us...@example.net> 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

[GC]

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

[Chris Rollings]

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.