Fatal Towplane Accident 5-9-20

I think a simple mechanical device like a lever arm or cage that extends behind the towplane for a few inches may enhance safety significantly. Something that the tow rope would press against at a particular angle that would activate a lever arm that automatically opens the tow hook and releases the ring. How hard would that be to make? It would be independent of the tow pilot, where if the tow rope under tension pulled at greater than a particular angle to the towplane, it would move the lever back and open the tow hook, releasing the ring.

See what I wrote early in the thread and what response I got:

"We all know how the self-release works on the glider side at winch launching: at a certain angle the rope puts a pressure on a lever which causes the release. Isn't it technically simple to have a similar solution on the tow plane side, a lever above the rope, which pressed at kiting would release the rope immediately? Where am I wrong?"

On Sun, 17 May 2020 15:08:51 -0700, Tom BravoMike wrote:


I think a simple mechanical device like a lever arm or cage that
extends behind the towplane for a few inches may enhance safety
significantly. Something that the tow rope would press against at a
particular angle that would activate a lever arm that automatically
opens the tow hook and releases the ring. How hard would that be to
make? It would be independent of the tow pilot, where if the tow rope
under tension pulled at greater than a particular angle to the
towplane, it would move the lever back and open the tow hook, releasing
the ring.

See what I wrote early in the thread and what response I got:

"We all know how the self-release works on the glider side at winch
launching: at a certain angle the rope puts a pressure on a lever which
causes the release. Isn't it technically simple to have a similar
solution on the tow plane side, a lever above the rope, which pressed at
kiting would release the rope immediately? Where am I wrong?"

Nobody has yet referred to the series of experiments carried out in 1978
and 1982 by Chris Rollings at Booker in the UK. I've just put a copy of a
summary report he wrote some time after 2000 on my website:

https://www.gregorie.org/gliding/kiting_on_tow

This describes both sets of tests as well as a his explanation of why, in
his opinion, an automatic release based on line angle is unlikely to
work.

IIRC this is not the original report, which I've never seen. If anybody
reading this has seen an earlier version, especially one with diagrams or
photos in it, please post a link or give a reference if its in a gliding
magazine.


--
Martin | martin at
Gregorie | gregorie dot org

On Sunday, May 17, 2020 at 7:24:19 PM UTC-4, Martin Gregorie wrote:
On Sun, 17 May 2020 15:08:51 -0700, Tom BravoMike wrote:


I think a simple mechanical device like a lever arm or cage that
extends behind the towplane for a few inches may enhance safety
significantly. Something that the tow rope would press against at a
particular angle that would activate a lever arm that automatically
opens the tow hook and releases the ring. How hard would that be to
make? It would be independent of the tow pilot, where if the tow rope
under tension pulled at greater than a particular angle to the
towplane, it would move the lever back and open the tow hook, releasing
the ring.

See what I wrote early in the thread and what response I got:

"We all know how the self-release works on the glider side at winch
launching: at a certain angle the rope puts a pressure on a lever which
causes the release. Isn't it technically simple to have a similar
solution on the tow plane side, a lever above the rope, which pressed at
kiting would release the rope immediately? Where am I wrong?"

Nobody has yet referred to the series of experiments carried out in 1978
and 1982 by Chris Rollings at Booker in the UK. I've just put a copy of a
summary report he wrote some time after 2000 on my website:

https://www.gregorie.org/gliding/kiting_on_tow

This describes both sets of tests as well as a his explanation of why, in
his opinion, an automatic release based on line angle is unlikely to
work.

IIRC this is not the original report, which I've never seen. If anybody
reading this has seen an earlier version, especially one with diagrams or
photos in it, please post a link or give a reference if its in a gliding
magazine.


--
Martin | martin at
Gregorie | gregorie dot org

Thanks, Martin - excellent reference! It confirms my suspicion why an automatic release would be problematic!

Uli
'AS'

On Sunday, May 17, 2020 at 4:24:19 PM UTC-7, Martin Gregorie wrote:
On Sun, 17 May 2020 15:08:51 -0700, Tom BravoMike wrote:


I think a simple mechanical device like a lever arm or cage that
extends behind the towplane for a few inches may enhance safety
significantly. Something that the tow rope would press against at a
particular angle that would activate a lever arm that automatically
opens the tow hook and releases the ring. How hard would that be to
make? It would be independent of the tow pilot, where if the tow rope
under tension pulled at greater than a particular angle to the
towplane, it would move the lever back and open the tow hook, releasing
the ring.

See what I wrote early in the thread and what response I got:

"We all know how the self-release works on the glider side at winch
launching: at a certain angle the rope puts a pressure on a lever which
causes the release. Isn't it technically simple to have a similar
solution on the tow plane side, a lever above the rope, which pressed at
kiting would release the rope immediately? Where am I wrong?"

Nobody has yet referred to the series of experiments carried out in 1978
and 1982 by Chris Rollings at Booker in the UK. I've just put a copy of a
summary report he wrote some time after 2000 on my website:

https://www.gregorie.org/gliding/kiting_on_tow

This describes both sets of tests as well as a his explanation of why, in
his opinion, an automatic release based on line angle is unlikely to
work.

IIRC this is not the original report, which I've never seen. If anybody
reading this has seen an earlier version, especially one with diagrams or
photos in it, please post a link or give a reference if its in a gliding
magazine.


--
Martin | martin at
Gregorie | gregorie dot org

Interesting read. It still leaves open the possibility of using acceleration and rotation sensors (MEMs) to profile a kiting incident and cut the rope (as mentioned earlier in this thread). It would be easy to record those values (at altitude) with a simulated kiting.

Then we need a reliable rope cutting device, triggered electrically by the MEMs circuit. I just did a conceptual exploration of a guillotine that uses a .22 cal short blank to actuate the blade. I know nothing about guns or munitions, but I am sure someone here has better suggestions for a firing mechanism, released by a melting fuse wire. The firing pin mechanism should be modular and sealed, so replacement is simple and reliable.

Please see screen shots here. As I said, it is all conceptual, and I am looking for input/suggestions. Fire away... https://www.dropbox.com/sh/8o6sbwho3...yO9ts-Voa?dl=0

Matt

FLY THE AIRPLANE sounds good on the ground, and is accurate. But seldom mentioned is this might not be that simple.

Losing hat and glasses and anything else loose in the cockpit might make flying it challenging. Trying not to get hit with a canopy that may still be partially be attached could be another issue. Not to mention with one piece canopies you are going to have a lot of wind in your face

Here is a 1st hand account of such an event, Additional info tow rope was a 1/4� hollowbraid rope.

http://www.soaridaho.com/Schreder/HP-16/nocan.htm

Brian

On Sunday, 17 May 2020 09:03:07 UTC+1, John Foster wrote:
On Saturday, May 16, 2020 at 11:26:06 PM UTC-6, Mike Schumann wrote:
On Saturday, May 16, 2020 at 9:44:41 PM UTC-5, wrote:
Matt, great that you have successful patents. I actually have two of my own. But you probably need to answer your own question, namely when is there enough existing technology? The schweizer and tost have been working successfully for more than 60 years with millions of tows to their credit. Maybe the problem is the modern guy behind the stick and not the “antiquated� technology. Maybe the problem needs to be addressed at the source and not put another bandaid on the festering wound. Taking your analogy and applying it to it’s ridiculous conclusion; why have any aviation training at all? Lets just use engineering to solve every problem of airmanship. Folks the problem is not with the metal (tow hitch) it is with the “mental�!

As for operating with no tow hitch at all, let me tell you, there are guys I would be totally comfortable with towing them with the rope tied to my tail spring (been there-done that), and there are others I wouldn’t tow with the most highly engineered “fail safe� contraption you could possibly design.

Accidents like this can happen to anyone, regardless of their training, reputation, or experience. There are all kinds of scenarios that can trigger a kiting event. One particular danger, given the demographics of our glider pilots, is sudden pilot incapacitation, such as having a heart attack or a stroke.

Having an automatic release mechanism sounds like a reasonable safety enhancement that should be relatively doable from a technology perspective. There are number of approaches, including a simple mechacable, co system based on pulling all the way back on the tow plane stick, or some mechanical or electronic mechanism that can detect an upward force on the tow hook that exceeds the elevator authority of the tow plane.

I think a simple mechanical device like a lever arm or cage that extends behind the towplane for a few inches may enhance safety significantly. Something that the tow rope would press against at a particular angle that would activate a lever arm that automatically opens the tow hook and releases the ring. How hard would that be to make? It would be independent of the tow pilot, where if the tow rope under tension pulled at greater than a particular angle to the towplane, it would move the lever back and open the tow hook, releasing the ring.

On Sunday, 17 May 2020 13:23:21 UTC+1, Jonathan St. Cloud wrote:
On Saturday, May 16, 2020 at 9:10:01 AM UTC-7, Rhubarb wrote:
I believe that full up elevator is what the towpilot will instinctively do in a kite siuation. This device will detect that and hopefully not give any false positives

release logic something like:-
1) GPS groundspeed ~60kmh for for ~5 seconds (so its not an engine test)
2) engine throttle ~80% for ~5 seconds (so its a take-off)
3) full up elevator (for more then ~0.2 second to filter out a knock)

when 1) and 2) are satisfied the system is "armed". A low groundspeed or Landing flaps could disarm it

I have chosen a low groundspeed in 1) to accomodate a strong head wind

GPS groundspeed and full elevator are easy to measure. Throttle a little trickier - maybe one could use flaps instead. tweak as necessary

Manual override, arm and disarm switches in the cockpit of course. some LEDs.

a simple embedded CPU costing 1$ can easily handle this and is very reliable. The BOM could be under 50$. This can be built by a hobbyist.

The tricky bit is
* Mounting the sensors
* triggering the release if its not electical

Peter

Wouldn't it be easier to design an electrical detach of tow rope by a button on the stick or throttle. This way the tow pilot decides and it would take a fraction of a second to activate. As stated before, helicopters use both a stick mounted electronic release and a stick mounted Manuel release.. Full disclaimer, I am not a tow pilot, not a mechanic, can afford new tape each time I assemble, and I don't unbuckle to stand up in flight to untangle yaw strings. A few days ago I would have thought that was normal, now I am confused.

A parallel discussion has arisen on the UK version of this forum.

There have been some memories of tests at one club years ago, deliberately simulating the problem at a safe height.

One thing that two of us remembered is that the tug pilot said it was impossible to pull the release hard enough to let go the rope.

They swapped out the Schweizer hooks and fitted Tost.

I did a search for Schweizer tow hook, and found this, which graphically explains what that difficulty might have been


https://www.soaringsafety.org/learni...ges/Image20.gi
f

https://www.soaringsafety.org/learni...onnecting.html

Also, a separate comment just above that picture says that sometimes
the ring can go forward and obstruct the release.

I've seen that once, a tug intentionally dropping a rope near the launch point but it didn't fall off. I walked up and found the ring looped forward over the top of the release arm.

In all these discussions about feasibility of designing an automatic release method, first it might be worth reconsidering the tow hook, whether it will let go when the command is issued. Also, will a guillotine definitely work?

On Sun, 17 May 2020 18:40:10 -0700, Matt Herron Jr. wrote:

Interesting read. It still leaves open the possibility of using
acceleration and rotation sensors (MEMs) to profile a kiting incident
and cut the rope (as mentioned earlier in this thread). It would be
easy to record those values (at altitude) with a simulated kiting.

I have distinct feeling that simpler (to operate) is better, so wonder if
full up elevator on the tow plane would trigger it, i.e. trigger mounted
just behind a spring loaded stick backstop. The spring should be strong
enough that holding the stick back 'normally', e.g. for taxiing in wind,
would not trigger the guillotine but a "we're all about to die!" yank on
the stick would override the spring.

Disclaimer: I am not a power pilot, let alone a tuggie who's been upset
by a glider, so have no idea whether this might work or is just plain
stoopid.

Then we need a reliable rope cutting device, triggered electrically by
the MEMs circuit. I just did a conceptual exploration of a guillotine
that uses a .22 cal short blank to actuate the blade. I know nothing
about guns or munitions, but I am sure someone here has better
suggestions for a firing mechanism, released by a melting fuse wire.
The firing pin mechanism should be modular and sealed, so replacement is
simple and reliable.

Please see screen shots here. As I said, it is all conceptual, and I am
looking for input/suggestions. Fire away...
https://www.dropbox.com/sh/8o6sbwho3...wkUoyO9ts-Voa?
dl=0


Looks good, but something similar using a gas cartridge would
be more acceptable in parts of the world where ammo is relatively
difficult to come by. A solution that got worldwide use would be better
than a US-only solution simply because the market would be bigger and
cost less per unit fitted.

FWIW, the guillotine on most winches are rather strong springs that work
on the chisel on anvil principle - and that were developed back in the
day when the standard rope was 4.5mm steel cable.


--
Martin | martin at
Gregorie | gregorie dot org

On Sunday, May 17, 2020 at 7:12:16 PM UTC-7, Brian wrote:
FLY THE AIRPLANE sounds good on the ground, and is accurate. But seldom mentioned is this might not be that simple.

Losing hat and glasses and anything else loose in the cockpit might make flying it challenging. Trying not to get hit with a canopy that may still be partially be attached could be another issue. Not to mention with one piece canopies you are going to have a lot of wind in your face

Here is a 1st hand account of such an event, Additional info tow rope was a 1/4� hollowbraid rope.

http://www.soaridaho.com/Schreder/HP-16/nocan.htm

Brian

In the situation you just described, my first reaction would be to release from tow. As an early instructor told me, "don't kill the ****ing tow pilot, because it makes you look like an asshole." That is a direct quote by the way. He made a real impression when he snookered me to look away from the tow plane for a second then he released me (because I lost sight of tow). Some of you might have heard how cheap glider pilots are. Well, I had to buy another tow with that lesson learned. I am sure I can make as big a mistake as the next guy, but my DNA is to not kill the guy doing me a favor.
Confused, Jon

On Monday, May 18, 2020 at 9:09:38 AM UTC-4, Martin Gregorie wrote:
On Sun, 17 May 2020 18:40:10 -0700, Matt Herron Jr. wrote:

Interesting read. It still leaves open the possibility of using
acceleration and rotation sensors (MEMs) to profile a kiting incident
and cut the rope (as mentioned earlier in this thread). It would be
easy to record those values (at altitude) with a simulated kiting.

I have distinct feeling that simpler (to operate) is better, so wonder if
full up elevator on the tow plane would trigger it, i.e. trigger mounted
just behind a spring loaded stick backstop. The spring should be strong
enough that holding the stick back 'normally', e.g. for taxiing in wind,
would not trigger the guillotine but a "we're all about to die!" yank on
the stick would override the spring.

Disclaimer: I am not a power pilot, let alone a tuggie who's been upset
by a glider, so have no idea whether this might work or is just plain
stoopid.

Then we need a reliable rope cutting device, triggered electrically by
the MEMs circuit. I just did a conceptual exploration of a guillotine
that uses a .22 cal short blank to actuate the blade. I know nothing
about guns or munitions, but I am sure someone here has better
suggestions for a firing mechanism, released by a melting fuse wire.
The firing pin mechanism should be modular and sealed, so replacement is
simple and reliable.

Please see screen shots here. As I said, it is all conceptual, and I am
looking for input/suggestions. Fire away...
https://www.dropbox.com/sh/8o6sbwho3...wkUoyO9ts-Voa?
dl=0


Looks good, but something similar using a gas cartridge would
be more acceptable in parts of the world where ammo is relatively
difficult to come by. A solution that got worldwide use would be better
than a US-only solution simply because the market would be bigger and
cost less per unit fitted.

FWIW, the guillotine on most winches are rather strong springs that work
on the chisel on anvil principle - and that were developed back in the
day when the standard rope was 4.5mm steel cable.


--
Martin | martin at
Gregorie | gregorie dot org

A nail-gun (ram-set) that shoots steel nails into concrete is powered by .22 cal blanks and they should be readily available everywhere.
However, why cut the rope if you can have a parallel actuation of the already existing release mechanism?

Uli
'AS'

After reading all the secondary type release options I think I'm with AS.
Either have a Tost Release or a inverted Schweitzer release that could very quickly be operated electrically from a switch on the yoke or control stick..
These kiting accidents happen very fast.
If the Tow pilot IMHO had a electric switch he could actuate by either a button on a switch to dump the rope this could help.
I would imagine it would be fairly easy to engineer a pulling electric solenoid that is attached to the existing release cable, sister-ed on to it. When the tow pilot decides hes had enough, touch the button or slide his hand to activate a switch and release the rope quickly.
Use the existing system your tug has now, just add to it. This system seems so easy maybe I could even build it in a day. Don't try and cut the rope, just release it, very quickly.
Good idea?
Nick
T