I believe that ATC don't generally use Primary Radar data anymore but display SSR plots only?
Not correct (wish it was though!!!)
Operational uses of SSR Mode 3A & 3C:
a) Establish & maintain ident of an a/c
b) Establish the posn of an a/c
c) Facilitate transfer of a/c between ATC units
d) To supplement primary radar information (i.e when a/c are in Wx clutter/radar shaddow etc)
e) To provide navigational assistance when requested by the pilot
f) To provide a radar service in the absence of primary radar, but only under specified conditions g) to detect aircraft subject to distress/rad fails/unlawful interference
In practice, SSR is almost always used in conjunction with primary radar. SSR is only used on it's own as a temp measure. The use of SSR on its own must be authorised and the pilot must be informed.
Wader 2 is correct though....
Mode 1 - Military Parentage Code.
Mode 2 - Military Individual Code.
Mode 3a - The 4 figure squawk.
Mode 3b - Not used in Europe (its a civil thing)
Mode 3c - Coded Height Information
Mode 3d - Not used as yet world wide (I believe)
Mode 4 - Have not got a clue, but know its important to the Scopies
Clear as mud - all the above is from a blurred memory, but if i have made a mistake please let me know
MM
