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Gliding risk....



 
 
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  #101  
Old November 22nd 19, 07:23 PM posted to rec.aviation.soaring
2KA
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Default Gliding risk....

Wow, what great work. Thanks!

I understand from the article that you looked at both US and German reports for the source data. Were there any significant differences, or did the accident causes break out in similar percentages?

Lynn Alley
"2KA"


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  #102  
Old November 22nd 19, 07:32 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Default Gliding risk....

Nicely done and insightful....yes, a longish read, but I read the whole thing.
Thanks for your time.....

Only "nitpick" maybe run the text through a grammar/spell checker and repost. Some minor spacing, spelling and grammar issues.
Otherwise, the gist gets through and worth the read.

Charlie, ex-CFIG and regional/national contest pilot in the US.
  #103  
Old November 22nd 19, 07:47 PM posted to rec.aviation.soaring
Bret Hess
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Default Gliding risk....

Clemens, can you analyze vs "under the influence of competition" factor?
  #104  
Old November 22nd 19, 07:56 PM posted to rec.aviation.soaring
Clemens Ceipek
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Default Gliding risk....


I understand from the article that you looked at both US and German reports for the source data. Were there any significant differences, or did the accident causes break out in similar percentages?

Lynn Alley
"2KA"


Lynn Alley - great question. Overall the results are fairly similar and for many individual causes the numbers are too small to be statistically significant. That said, the following differences stood out to me and are significant:

Germany has a higher share of accidents in standard emergency situations - this is driven mainly by a much greater use of winch launches, which are more accident prone than aero-tows because pilots must react very quickly in case of a cable break or winch slow down before they stall and spin in. (It also takes a greater number of winch launches to get into lift because you can't wait to release until you're in a thermal.) The low attainable altitude on the winch also tempts pilots to thermal too low near the airport - thus Germany has a higher share of accidents caused by "delaying to land at the airport".

The US has a higher share of "fateful decision" accidents which I believe is attributable to a larger percentage of flights occurring in unforgiving terrain (most of Germany is flat with plenty of fields - similar to the Midwest.) The US has greater numbers of accidents due to "delaying decision to land out" and "out of glide range". I also looked at the data from Austria (although they are not included in the stats) and you will also see a greater share of decision mistakes there since almost all of the soaring takes place in the mountains.

Hope this helps.
Clemens
  #105  
Old November 22nd 19, 08:05 PM posted to rec.aviation.soaring
Clemens Ceipek
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Default Gliding risk....


can you analyze vs "under the influence of competition" factor?


Brett - I wanted to do that as well. Unfortunately, it's not enough to know how many accidents occur in competition. To understand if competition flying is more dangerous than regular flying (and by how much), I would need to know what percentage of flights occur in competition vs. pleasure flights vs. training flights. Unfortunately, I don't think this information exists and I think a guess would be too inaccurate. If you have a good source, please let me know. Clemens

  #106  
Old November 22nd 19, 08:49 PM posted to rec.aviation.soaring
john firth
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Default Gliding risk....

On Wednesday, October 30, 2019 at 8:49:22 PM UTC-4, wrote:
For those who haven’t seen it....

https://chessintheair.com/the-risk-o...-what-we-love/


Great piece of work which I shall read again in March!

A few comments;

"if you dread the thought of a field landing....."
then you should set up a simulation on your own field and practice till
you are confident.

No pilot should EVER be criticised for deciding on a field landing; I suppose this must happen; very immature behavior.

Duo Discus in flight wing failure.
The German report ( thanks Google) says that there was an unbonded section
on the spar some 20cm long. Surely an ultrasound scan of the spar line
would reveal this. I have no experience/ expertise in this regard.

John Firth
  #107  
Old December 4th 19, 10:54 PM posted to rec.aviation.soaring
2G
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Default Gliding risk....

On Friday, November 22, 2019 at 11:49:15 AM UTC-8, john firth wrote:
On Wednesday, October 30, 2019 at 8:49:22 PM UTC-4, wrote:
For those who haven’t seen it....

https://chessintheair.com/the-risk-o...-what-we-love/


Great piece of work which I shall read again in March!

A few comments;

"if you dread the thought of a field landing....."
then you should set up a simulation on your own field and practice till
you are confident.

No pilot should EVER be criticised for deciding on a field landing; I suppose this must happen; very immature behavior.

Duo Discus in flight wing failure.
The German report ( thanks Google) says that there was an unbonded section
on the spar some 20cm long. Surely an ultrasound scan of the spar line
would reveal this. I have no experience/ expertise in this regard.

John Firth


Thanks for pointing the Duo Discus manufacturing problem. Here is a link to the BFU report:
https://www.bfu-web.de/EN/Publicatio...ublicationFile

A couple of disturbing findings in this report:

"Manufacture of the wings was based on the knowledge of Schempp-Hirth at Kircheim which was not available as written instructions. This was true for the processes during manufacture, the specification of materical (e.g. adhesives) and the criteria for quality assurance (tolerances)."

Instead, employees from the subcontractors spent time at Kircheim to learn all of this. This system would utterly fail any quality control evaluation (e.g. CE), and is disturbing to me as a potential customer. Furthermore, this was the SECOND wing failure of an S-H product in the same year:

"The accident to the Discus CS in France revealed an even more extensive bonding defect on the wing spar."

This Discus had been in service for some time prior to the failure (900 hrs and 900 launches), so time in service is no security blanket. All Discus gliders were grounded in France after this accident:

https://groups.google.com/forum/#!to...ng/MTRTAwPn7qA

Yes, ultrasonic nondestructive testing can reveal such defects, but I don't know of any glider repair facilities that use them. I have designed such products in the past and have connections with a local NDT company. I will reach out to them to see how feasible such testing is. In the mean time, you can do a crude kind of NDT test by tapping on the surface above the bond with a metal object like a coin and listen to the sound produced. A defective bond will sound different than a good bond (less sharp and duller):

https://www.aviationpros.com/home/ar...aft-composites

Before I purchased any glider manufactured by either of these subcontractors I would insist on a full-blown ultrasonic NDT test.

Tom

  #108  
Old December 5th 19, 04:53 AM posted to rec.aviation.soaring
son_of_flubber
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Default Gliding risk....

On Wednesday, December 4, 2019 at 4:54:08 PM UTC-5, 2G wrote:

Before I purchased any glider manufactured by either of these subcontractors I would insist on a full-blown ultrasonic NDT test.


This relevant accident happened in 2003.

Before I get my nickers in a twist, I'd like to know whether the manufacturing deficiencies have been addressed in the intervening 16 years.
  #109  
Old December 5th 19, 05:41 AM posted to rec.aviation.soaring
2G
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Posts: 733
Default Gliding risk....

On Wednesday, December 4, 2019 at 7:53:57 PM UTC-8, son_of_flubber wrote:
On Wednesday, December 4, 2019 at 4:54:08 PM UTC-5, 2G wrote:

Before I purchased any glider manufactured by either of these subcontractors I would insist on a full-blown ultrasonic NDT test.


This relevant accident happened in 2003.

Before I get my nickers in a twist, I'd like to know whether the manufacturing deficiencies have been addressed in the intervening 16 years.


Well, my nickers ARE in a twist: I need to learn more to get them untwisted. This kind of slip-shod manufacturing puts a cloud over the whole industry.
  #110  
Old December 5th 19, 05:43 AM posted to rec.aviation.soaring
5Z
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Posts: 351
Default Gliding risk....

On Wednesday, December 4, 2019 at 7:53:57 PM UTC-8, son_of_flubber wrote:
On Wednesday, December 4, 2019 at 4:54:08 PM UTC-5, 2G wrote:

Before I purchased any glider manufactured by either of these subcontractors I would insist on a full-blown ultrasonic NDT test.


This relevant accident happened in 2003.

Before I get my nickers in a twist, I'd like to know whether the manufacturing deficiencies have been addressed in the intervening 16 years.


Sounds like a recent story about Boeing...
https://boingboing.net/2019/12/02/ra...-shavings.html

"...Barnett says the 787 facility was run by a new leadership team that had been transferred in from St Louis, MO, with a background in overseeing military contracts, and that they prioritized production speed over airworthiness and safety.

He says that the culture of poor safety began in 2011 or 2012, with top management ordering employees not to document defects, but that this graduated to "ignoring safety issues and the defective parts." Barnett pursued this internally, exhausting every internal process and facing workplace retaliation before going to federal regulators like the FAA and OSHA, which resulted in even more retaliation, and, eventually, blackballing across the aviation industry."
 




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