On Mar 5, 10:04*pm, Hagbard Celine wrote:
" No "havoc" is created by two transponders sqawking 1200 near each
other."

Tell that to the Dutch who fly in the Schiphol area...

Shiphol had a problem with the back-end processing and display of Mode
S derived traffic data on their display screens. In hindsight this
seems an awfully obvious thing they missed with Mode S transponder
mandates.

Some summary to the problem is at

http://eurocontrol.int/msa/public/st...Procedure.html

Transponders provide visibility for gliders to both ATC and airliner/
fast jets TCAS and are therefore a critical item anywhere we are
mixing those types of aircraft. And I fail to see how a particular
display capacity/planning problem at Shiphol is that relevant to any
general idea of carriage of transponders.

Darryl