On Saturday, November 28, 2015 at 1:19:12 PM UTC-8, Andy Blackburn wrote:

One other perspective. I really hate getting collision alarms - particularly on course where you by definition have missed something if it happens. It generates a near-panic emotional response because you are potentially seconds from being hit. A little tunnel vision sets in as you look down to the display to try to make out the direction and relative altitude of the target and then swing your gaze to pick them up - and figure out what to do. I have on occasion picked up the wrong (farther away) glider in the same general direction - that leads to a very nasty surprise.

Flarm is architected as a multi-layer defense against collisions. The collision alarm is the last line of defense and the broader target tracking is the more important preventative layer - much the way ATC vectoring of traffic is the more important part of keeping airliners apart and TCAS is the last line of defense.

I find degrading the first line of defense and relying only on the last line of defense to not only be somewhat additionally risky because you are counting on everyone to do the right thing in a few seconds under stress, but it is also more anxiety producing to rely almost entirely on an alarm of an impending collision, rather than staying out of each other's way - even if it works out perfectly every time an alarm happens. I don't think very many people would be comfortable getting on airliners if they sent all the air traffic controllers home and relied just on TCAS - even if it worked perfectly every single time.

I know - I've totally lost my sense of excitement and adventure.

9B