"Cannot speak for Tubby, but most of you seem still to be convinced that pitot icing
always leads to the related ASI over-reading. This presumption is unfounded. Further homework is called for."
Chris I do have practical experience of pitot icing in a non fbw Airbus and in my case it led to a false underspeed indication.The first ecam was for Fuel aft transfer!
In severe icing,if the drain holes of the pitot are blocked,the sensed pressure is trapped and remains constant ,whatever the changes in airspeed or altitude.If the holes are free the airspeed varies or may quickly drop to Vss until exiting the severe ice area.
See diagrams below for an explanation.Oddly these do not appear in the 330 fcom!
