Donald Ramsey wrote:

When radar fails, do ATC folks have at their avail the last recorded
positions of all aircraft or a computed projection (coast?), or do
all the screens just go black? :O

Depends on what failed. If the radar itself failed then you would still
have the coast tags. If the radar display itself failed you have your
paper strips and your memory.


I don't doubt that most controllers
can revert back to non-radar procedures and successfully handle traffic,
I'm just curious how the transition would occur.

A real display failure with any amount of traffic is a total goat rope.
Approach controllers don't do nonradar and if forced to do so on
zero notice it could get real ugly real fast.