On Wednesday, July 15, 2015 at 7:19:11 PM UTC-7, 2G wrote:
Andy,
The 80 figure was given to me in good faith, and I repeated it as such. Could I have verified this number from a 2nd source? Sure, but the actual number isn't the crux of the matter. Would you feel any different about the Nephi operation if the number WAS 80? I doubt it. Are my concerns alleviated if I knew the actual number was 65? No. Anyway, we all agree the true number is 65. So let's JUST MOVE ON - this is beating a dead horse.

Bruce raised an interesting question: is a meet of 20 gliders inherently dangerous. The only meet that has no risk of a glider-glider mid-air is a meet of one. Raise it to two and now the risk is non-zero. Sound ridiculous? Hardly, two gliders flying out of Arlington, WA, had a mid-air resulting in one fatality. So as the number of gliders flying in the same airspace increases, so does the risk of a mid-air. That is just common sense that, I think, we can all agree on. The point of contention is that risk acceptable or not. That gets down to a judgment issue. Some people think that just because nothing bad happened there was no, or little, risk. That is just, simply, not true.

Bruce inspired me to do a little research. In my former life as a research engineer I always put a lot of effort into getting as much information on a particular subject before trying fashion a solution. So I started gathering data on glider-glider mid-airs (there are also a few glider-power mid-airs, but this is a different problem). Part of the problem of gathering this data is it is a bit tedious. The FAA ASRS database found no such incidents, so it is of no help whatsoever. The NTSB accident database is very limited in finding such incidents because a mid-air is not a searchable criteria.. You basically have to look at EVERY reported accident involving gliders. I did, however, find some glider mid-airs by going thru the fatal glider accidents (I quit after 2007 due to lack of time). I found more such incidents by doing a Google search ("glider mid-air accident"). I came up with 13 glider-glider mid-airs (remember, this is not an exhaustive search) What was glaring about what I found was a disproportionate number of mid-airs involving contest flying; 11 of the 13. Contests represent perhaps 5% of total glider hours flown, yet a majority of mid-airs occur during contests. The World gliding contest is particularly bad (5 out of 13). If you calculate the number of mid-airs per 100,000 hours flown contest flying dwarfs other types of events on a risk-based assessment.

I also went to the Soaring Safety Foundation for guidance. I was stunned to find that the SSF has NO database whatsoever. This is a glaring deficiency on their part. I propose that the SSF create a database of ALL glider accidents that is searchable by all phases of glider flying. The Albuquerque Soaring Club did an excellent analysis of glider accidents in New Mexico (http://www.abqsoaring.org/misc_files...Accidents.doc). This level of analysis needs to be done on a national basis.

I feel strongly about safety and do not apologize for it. If I can prevent a SINGLE accident, fatal or otherwise, by my actions it is WORTH IT for the abuse I have taken here (and make no mistake: some people here have been extraordinary abusive, but I don't give a damn).

Best regards,
Tom

If you search the NTSB with type "Glider" and keyword "mid air" 10 come up. Yeah, they are mostly at contests. Yeah, if you fly in crowded airspace you are more likely to hit something. Still, mid air collisions remain a rare event, we hope made rarer still by Flarm.