Ian,
you say…"many if not most controllers will have primary switched off and base all their work on SSR/ADS.".
This is incorrect. Certainly in The U.K. PSR and SSR data are displayed together, over-laid on the same screen. The only time SSR only is used is when the PSR has failed or is on maintenance.
I suspect the majority of ATC units work the same way. If ATC operated as you suggest, should the SSR system on the ground fail, the ATCOs would be left with nothing but the video-maps.
Last edited by ZOOKER; 13th May 2014 at 19:32.
Reason: Minor typing error.