Originally Posted by
cats_five
More to the point, could transponders have prevented any of the non-transponder equipped proxes or infringements? I suspect not - Mode S (if the transponder is turned on) will help find the culprit, but it won't stop them infringing.
It is important to understand why transponders a relevant to 'reducing infringements'. The transponder doesn't change the fact the infringement has happened, but it does help everyone else deal with the fact safely. Also, a non-transponding aircraft can realistically only be detected infringing a Zone (not an area or airway) unless it is also an airprox - because no one can see it happen unless they nearly hit the infringing aircraft! In terms of infringements that were in the 'but for the Grace of God...' camp, they are split about 1/3 no-transponder, 1/3 transponder with no Altitude, and 1/3 Mode C/S. When I looked at it, all of the Mode C/S 'close call' infringements had some complicating factor that resulted in ATC having little time to react.
Originally Posted by
cats_five
The sort of software on a PDA linked to a GPS that most XC glider pilots use might do more to prevent infringements than a transponder, and it can be implemented for less than £100. (free software, 2nd hand GPS & PDA from Ebay) It's also fairly easy to reload the airspace when that changes - downloads are easy to find on the Internet, and are also easy to check against a chart.
While people may use this kind of roped together system, I have also seen plenty of issues where people get muddled up with the technology and would have been better off with much more traditional nav approaches. All the various threads around loss of GPS reception, GPS showed wrong position, map stopped working, etc. seem to involve these roped together solutions. Panel mount GPS is an ultra reliable system. Used PDAs with internal GPS antenna, limited battery life/power codes and cables trailing around the cockpit, running free software is not a great solution to certainty of position or maintaining a good external lookout. (IMHO)