Intruder :
The downlink itself may not show if the pilot is following an RA, but the altitude readout on the ATC screen will be able to confirm it within a few seconds -- or earlier if the downlink is delayed.
Agreed, but it did not work in Ueberlingen . Radar return was 12 seconds there, but on most long range en route radars it is 10 seconds . If the first return is garbled or filtered out by the system ( as it often is the case for sudden aircraft mode C jumps ) , one has to wait until next return to confirm movement and direction.
In any case the main point is that responsibility for anti collision still remains with the controller until he gets confirmation that the aircraft/pilot is manoeuvring in accordance with an RA. So some believe (strongly I might add ) that down linking RAs will make controllers intervention during a TCAS sequence more likely and induce a new kind of problems.
The FRADS/RADE tests conducted by Eurocontrol in Bretigny last years , show controller acceptance of the technical display shown , but did not address the responsibility/ intervention issue.
It will not be an easy one to solve , because waiting 10 or 20 seconds doing nothing when aircraft are on a collision course is not what controllers were and are trained to do.