On Friday, August 9, 2013 2:36:16 AM UTC-7, kirk.stant wrote:
On Friday, August 9, 2013 4:39:08 AM UTC+2, jfitch wrote:



Perhaps because the collision of a glider with a mode C target is extremely rare?



Really? I believe they are more common than glider-to-glider, if the whole of glider operations is considered (outside contests, for example). Several towplane/glider collisions come to mind, the Cirrus that hit a towplane with a glider on tow in Colorado, and of course the Hawker bizjet that ran into the ASG-29 over the Sierras - all were cases of Mode C targets that may have been detected early enough to prevent collision with a working PCAS or PowerFlarm.



In many non-contest locations, the most common target that you will see on your PF will be a Mode-C; unlikely that the local 2-33 will have a PF!



Kirk

66

There appear to be 8 collisions between gliders and light airplanes in the NTSB database in the last 20 years. I think we counted 7 glider to glider mid airs in the same period (each of which of course involves 2 gliders). Mode C detection would not guarantee collision avoidance, as PowerFlarm glider detection (almost) does. As with glider-to-glider mid air collisions, you are far better served from the standpoint of safety with a little more spin/stall practice than with a PCAS device. You are about 100 times more likely to collide with terrain (and about 3 times more likely to strike a power line) than a light airplane.

And to repeat once more, I'm not arguing against them: I have both PowerFlarm and Mode S. What I am saying is that eliminating all mid air collisions will not make soaring statistically safer by any significant amount. If you eliminate the 15 or so mid air hits from the NTSB database, you will still find about 700 more ways to crash a glider. If you have a limited budget, spend it on some stall/spin training.