Pineteam (and Check Airman) thanks for the link to the Rockwell Collins Multiscan presentation. So far I'm not really a fan of the thing but this gave some good insight. As regards the original question I get the wx radar on on the ground since the flight I had some years ago where we got to the Balkans only to find the radar not working when we turned it on. It's the sort of problem I would rather find out about on the ground before the flight, not at 38000 when presented with a load of active storms
No company SOP regards usage.