Having caught up on this thread since yesterday I am not happy about the priviliges enjoyed by the gliding community.
I accept there is merit in not imposing transponders on traffic outside CAS in VMC. The argument that not all flying machines can fit transponders is persuasive as more importantly is the evidence that the risk of a collision is small.
There are two reasons it is small. See and avoid has a good chance of working given the low level speed restrictions imposed on all aircraft. The big sky comes to the rescue most times see and avoid fails.
See and avoid cannot wok in IMC. A RIS provides a good degree of salvation BUT the service is often not available and even when it is gliders do not always make good primary targets.
This can mean than anyone in IMC has no protection afforded to them what so ever from gliders also in IMC where the gliders are operating outside designated gliding sites.
I dont accept that is reasonable or fair to other airspace users. I would ban gliders flying in IMC unless they were fitted with a transponder that was at least turned on in cloud.
God forbid it ever happens but if there were a mid air between a glider and a powered aircraft in IMC I suspect the AAIB would have no alternative but recommend all gliders operating in IMC should be required to carry a transponder.