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Old December 10th 13, 08:14 PM posted to rec.aviation.soaring
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Default "Do It Yourself" airborne proximity warning device

On Tuesday, December 10, 2013 10:19:07 AM UTC-8, Dan Marotta wrote:

I used the keywords "midair" and "glider" in my search but there may well be
others which I missed. My point is that, considering the number of glider
flights conducted in the US, the risk of a midair is extremely low and, in
my opinion, does not warrant the expense, complexity, or distraction of a
collision warning device for most of the glider flying done in the US.
Competition flying is different, of course, as it concentrates so many
gliders in the same airspace. Europe is much more congested and has far
more glider flights than we do and I can see more of a benefit for them.


And, finally, for a good many of us glider pilots, we cannot simply lay down
for an ASG-29, full panel, and Cobra trailer. For us, the sport is somewhat
cost driven.



For some reason it is hard to get the NTSB database to cough up all the incidents. You missed several midairs I know of in the past 5 years or so including one requiring a bailout and one where one pilot tried to bailout but was unable to and thankfully was able to land without injury. That doesn't include a number of scary near misses.

I believe the data shows that midair is the second leading cause of fatality next to stall-spin/collision with terrain. Glider-glider collision is at least ten times likely as glider-GA collision and (by the data) infinitely more likely than glider-air transport collision. If we ever got one of those it would be ugly and bring the stats up to making glider-glider 100 times more likely than glider-air transport.

Yes, contests gather gliders and concentrate traffic but if you look at the some of the work that has been done to accumulate OLC traces into glider flight path "heat maps" you discover that the combination of topography, airports, airspace and (especially) lift sources puts gliders in much closer proximity to each other than you might otherwise think. Gliders tend to occupy a small, common proportion of the available airspace, even though we think we are flying just anywhere. This explains why we see more glider-to-glider collisions than any other kind of glider involved collision. It raises the question as to whether if forced to trade off transponder vs Flarm for cost reasons the most bang for the buck really might be Flarm, even for non-contest flying near terminal areas. The midair collision data suggests this might well be true since the penetration of Flarm and transponders in gliders are both low. The equation would only flip for very small numbers of gliders (5) flying right up against a busy international airport - though there aren't many of these. I carry both Flarm and a Mode S, but I realize others feel they can't afford both, just the way some feel a parachute isn't worth the cost (I believe there also are fewer successful bailouts than glider-glider midairs - so selling one's parachute to buy a Flarm may also be a statistically superior solution - though emotionally I can't imagine anyone making the switch).

In any case, having two, incompatible, Flarm-like technologies is a terrible idea for the reasons already articulated.

9B