I flew an A319-100 today OSL-LHR.
Prior to departure the captain made a PA advising we’d be de-icing before departure “as we picked up some ice on the way into Oslo”.
I was under the impression that pitot tubes, wings etc had anti-icing built in via some form of heating.
While I appreciate none of our current pilot contributors operate this type, or regularly fly in such conditions can you please describe how this would happen?
Where would this ice have likely been?
What features exist to prevent icing in flight?
How much ice can build up in flight before it becomes problematic?
