What was found
AIRSPEED DISPARITY DURING IFR APPROACH, WATER IN LT STATIC PORT. FIRST TIME OCCURRENCE W/ THIS AC OUTSIDE DURING RAINSTORM LASTING 3 HOURS. STATIC DRAINS DRY, WATER ACCUMULATED JUST INSIDE STATIC PORT. DID NOT KNOW WHY STATIC PORT HEATER DID NOT REMOVE THE MOISTURE. RESULT OF PROBLEM: AIRSPEED DISPARITY/ EFIS AIR DATA CHECK SOM ERROR/ PILOTS ABORTED APPROACH AND PERFORMED MISSED/ RETURNED TO DEPARTURE. BLEW OUT STATIC PORT, SUBSEQUENT FLIGHTS, OPS CHECKED GOOD. (K)