my experience is, that ATCs do not like glider pilots
as soon as they find out, that you cannot keep your
flight level.
In central Europe I had a transponder in the glider,
to get permission to cross some controlled corridors.
I mostly got permission to cross the airspace with
the condition of keeping flight level! A reply of not
being able to keep flight level invertet mostly the
permission into refusal.
The trick was then to enter the airspace first and then
request for sinking to flightlevel (-2FL for the 20km).
But the ATC never liked you for doing that!!

I think Transponder requirement is only virtually
increasing safety. You accept to install transponders
and as a thank you, they will steal you some more
airspace which has been free for VFR before!

Chris


"Robert Ehrlich" wrote in message
...
Chris Nicholas wrote:
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.