sensor_validation,
Having identical probes makes it easier to detect one outlier - they should all read the same - but why would they then not fail in same way when subject to same ice cloud?
Airflow related to probe has to be perfectly symetrical, which is barely never the case in flight, because they are on both side of the fuselage. The value displayed is a mean value of two or three pitot readings.
If one probe is failling to drain one kind of particule, it doesn't mean that it will fail to drain another kind. You'll have to know what kind of particule you are dealing with.
S~
Olivier