Originally Posted by
rocketmandlgc
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All the evidence suggests that safety is improving all the time. Proxes are significantly down, I won't re-print the figures - read other posts. The CAA's own figures state that 15% of airspace infrigements involve aircraft without transponders. I would respectfully point out that in reality that means 85% of infringements are by aircraft WITH transponders.
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More to the point, could transponders have prevented any of the non-transponder equiped 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. I read some of the airprox reports and found that the infringements often seemed to involve a pilot who was 'temporarily unsure of his postition' e.g. lost.
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.