Chris Nicholas wrote:

Mil80c , another point you need to be
aware of;

Many gliders, e.g. mine (a Ka6E), have neither panel space for a
transponder nor capability of carrying any more weight for the extra
batteries - I am already on max AUW, on a CofA which has already been
extended as far as it can be - I am 208 pounds with a parachute, and
there are plenty of heavier pilots than that.

If a new generation of lightweight, low power transponders emerges (the
UK CAA has persuaded one manufacturer to build a prototype which tested
OK), and if ICAO accept 20 w output instead of 100+, and if the thing is
taken to commercial production, and if it can come with an option of a
small remote control panel I could strap to my knee, with the larger
piece and battery going into the stowage behind the pilot's seat, and if
I can lose enought weight to compensate for it, then it might be viable.

I'm not holding my breath while we wait for all that to happen.

Regards - Chris N.

An experiment in the french Alps made with a group of tow planes
mimicking glider flight, i.e. circling together from time to time has
shown that transponders, except in mode S, may not be very useful in
gliders. As soon as 2 or more gliders are close together, e.g. circling
in the same thermal of working together the same ridge, they are hit
simultaneaously by the radar beam and generate simultaneaously their
responses, which results in both interfering and nothing useful
received at ATC. I had the chance of having one of the engineers
involved in the experiment as a passenger last September and he confirmed
this. In mode S, as each transponder is specifically adressable,
this mess will probably not occur, a new experiment using them is
planned.