Originally Posted by
ShyTorque
.... as a glider pilot you will be aware that your aircraft doesn't show up well on radar. Proper use of a transponder makes sure that it does.
This is a critical point and unfortunately Flarm is of no use to radar controllers. Visibility on the radar screen typically drops in and out as gliders go into a turn or below a certain airspeed. They pop in and out of the controller's screen disappearing for minutes, then reappearing, then they disappear again, a nightmare to coordinate others around that, with typically no radio communications either.