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[SamKellner]

http://www.hanggliding.org/viewtopic.ph ... highlight=

http://www.youtube.com/watch?v=_2oeb0nNIKs

Bill C, Hawks,

This accident is very similar to what happened here last year. Although from different causes. The flight looks about the same.

It seems that most agree that the line should be cut, at some point.

What do you think?

[Bob Kuczewski]

My only towing has been a tandem aero tow, so I'm posting without much experience at all.

But I was wondering if the underlying problem in this crash (and possibly Terry's) might be that hang gliders are insufficiently stable under those conditions. What struck me was that the glider started moving to the right (from camera perspective) and the pilot corrected but ended up to the left where he crashed. Is this a case of PIO?

With that thought in mind, I was wondering if anyone has done any experimenting with vertical tail fins to dampen side to side oscillations during a tow. I could imagine a large vertical fin that might even be released after the tow so it doesn't affect the rest of the flight.

Has anyone heard of anything like that?

[Bill Cummings]

I checked out the posts and video over at HGdotORG. The cause is reported to be hooking to the towline over the base tube.

That will pull the base tube back after launch. It will speed up the glider which will have the outcome of an increased chance of PIO and DIO.

A vertical stabilizer will mitigate the PIO and DIO at high speed flight.

Keep in mind that cutting the towline in Bob’s flight might only have helped for one second.

After the cut line anchors itself to the bushes along side the road Bob would have had a powered “crack the whip” crash into the ground with more G’s than the crash he had. Cutting the line is way down the list of my next best option in many situations.

The very slight left crosswind that Bob took off into should have had no significant adverse compounding of the chain of events that lead to the crash.

I would think that under the same conditions/situation that Bob had, being able to release from the towline easily without having to let go of the base tube would have been the next best option.

But failing that only the correct routing of the towline under the base tube was his last best option.

My friend Don Ray years back told me that my desire to start landing and taking off from the beach, instead of deep water, in an effort to add foot launching to our skill level would only be, “ADDING ANOTHER LEVEL OF COMPLEXITY TO OUR SPORT.”

After all we already had the boat towing figured out.

[SamKellner]

my desire to start landing and taking off from the beach, instead of deep water, in an effort to add foot launching to our skill level would only be, “ADDING ANOTHER LEVEL OF COMPLEXITY TO OUR SPORT.” .

Wow, does that mean you invented hang gliding?


Bill, I probably should have posted my question about the ICP over here.

[JoeF]

Sam,
found this:

DIO driver-induced oscillation. When kiting, the moving driving ground resistive set may have motions, accelerations, changes of motion texture, etc. that might induce oscillations in the tether set and the wing set of a a kite system.

Extended: Locally each creative individual often is making personal breakthroughs that are inventive for their lives; hopefully they celebrate such creative living with a joy and shared joy. That such inventive flow may not reach absolute mechanical global invention is a whole different game of cards.

"Was THAT a personal-local invention step by you?"
"Thank you for sharing the story and description of your ideas, insights, personal breakthroughs, etc. "

Sometimes a person wants to know if they are world-first on a mechanical claim; to get close to an answer on such, one would put the description out into the world in order to "test the waters" and see what others say about the matter. Searching in the literature, listening to the feedback, etc. can be done increasingly at less cost. A challenge though is the following: Not finding priors does not prove that a prior won't be discovered; it just means that the search to some point in time as yet to uncover a prior globally. And more, "first" for oneself is with HUGE impact on oneself! And more: Even getting an approved reviewed patent does not mean that a prior won't be found. The game of being absolute-global first on a mechanical concept or process or function is very challenging; and researchers trying to sort such matter out is often a very costly matter.

One of the tactics some will do--even without the patent play--is to headline, "I was first on this!" and play the King-of-the-Mountain game; will anyone come around to push the king off the mountaintop? The claiming person seems to sit on top of the mountain until someone finds a prior example that counters the claim to the throne. The claimant need spend only a penny now on the Internet to make a claim; then others that might care about the subject may end up spending loads of cash and time to prove a countering claim; the imbalance of costs can be considerable. Scholarly professional researchers well know about the cost of doing careful research.

It may be very understandable to invest one's 24 hours on nil care bout any "first" game; a preference might be to spend all of one's life on local personal creativity and perhaps the engendering in the local personal creativity of the next generation. Leave the matter of "first" to professional historians, while living personal firsts and helping others have personal firsts.

I personally have barefoot water skied. That is, my body was the wing of a kite system where the resistive-driving anchor was a powered-fueled boat guided by a pilot of that power. The tether set consisted of one main tether (tow line) that split closely to two lines to a handle set normal to the line of the main line. Then the tether set continued into being the tissues and tendons of my arm. The my body was the wing set of the kite system. That is, my chest and head and legs were aerodynamically deflecting the air with non-zero L/D; and my feet were hybrid paravane wings with a dominant play with the fluid water with a net L/D large enough for the wing, me, to "fly" near water surface with occasional deflects off to the side of the primary towing direction. I was a kite-system's wing. And upon unleashing from the powered tow, my body glided for some while in the air and water until the wing became a non-wing, just all wet. This was done in the Newport City waters during the time I being approached by UCLA athletic promoters; they gave me some time on the waters near where ten years later I would be involved in the Otto Meet just in sight of those waters; again being part of gliding kite systems. Every inch of one's personal local life is filled with "firsts" ... the present "Now" has never occurred before and so is filled with local-personal-important firsts. And I believe that such firsts are paramount... such make up the bulk of Universe, it seems; that is, what is is unique and ever locally first. The realm of structural or formal mechanical firsts is a playground for a neat game in its own right, optionally played or not.

P388-2.jpg (19.43 KiB) Viewed 14331 times

[SamKellner]

DIO driver-induced oscillation. When kiting, the moving driving ground resistive set may have motions, accelerations, changes of motion texture, etc. that might induce oscillations in the tether set and the wing set of a a kite system.

I can sure agree with that

[SamKellner]

My only towing has been a tandem aero tow, so I'm posting without much experience at all.

But I was wondering if the underlying problem might be that hang gliders are insufficiently stable under those conditions. Is this a case of PIO?

I was wondering if anyone has done any experimenting with vertical tail fins to dampen side to side oscillations during a tow. ?

Bob,
I don't think that HG design is insuffiently stable during tow ops, any more than HG is insufficiently stable while doing loops.

I have always used the verticle fin on my UltraSport, not because of the glider design. As a double surface intermediate, perhapps this modle attracts a lot of H-2s & 3s, and that's why the fin was included. If I was flying regularly, I'd probably ditch the fin.

Back to the video and about the line being over the bar: I almost think that the line being over the bar had very little to do with that accident.

Recently on the Yahoo Scootertow group, some of the most experienced reported normally towing with line over the bar, to top of tow . It surprised me.

[Bob Kuczewski]

I have always used the verticle fin on my UltraSport, not because of the glider design. As a double surface intermediate, perhapps this modle attracts a lot of H-2s & 3s, and that's why the fin was included. If I was flying regularly, I'd probably ditch the fin.

Hi Sam,

It sounds like the fin makes it easier to control which could be useful. In my post, I was thinking about using a super-large exaggerated fin that would be so big that it would probably produce more drag than you'd want for normal flying (which is why you'd want to be able to drop it). But the thought (maybe incorrect?) was that such a large fin would make it nearly impossible to have any kind of PIO and might even help prevent lockouts during the tow. But I haven't "done the math" to know if that's true, so that's why I was asking if anyone had experimented with the idea.

Just to be clear, the fin size that I'm talking about wouldn't make the glider unflyable. It would still fly pretty well even off tow and would be safe to fly all the way to the ground with no problem. But the size would cause drag and might cause other undesirable (but safe) flight characteristics which would be eliminated by simply dropping it after the tow.

Has anyone ever experimented with this kind of thing?

[SamKellner]

Bob,
Not that I know of, or maybe a drogue, yes, but not on tow. I don't know about dropping any objects from HG. Might require everyone wearing head gear, even while on the ground

[Bob Kuczewski]

Might require everyone wearing head gear, even while on the ground

Good point Sam!!