Pt probes question. In this AF note we read [my own rough translation] "March 2009 [...] Airbus recalls the procedure for maintenance and verification of the probes". The note does not say what anomalies (if any) were ever found during these checks. Could someone explain the procedure? In particular, can the drain holes be inspected visually on the ground, and how often is this done? Somebody mentioned the possibility of obstruction caused by corrosion; so this problem - if present - should persist long enough that it is detectable on the ground.