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?