What was found
DURING CLIMB AT ABOUT 20K, JUST AFTER PASSING THRU SOME CLOUDS, RECEIVED ALT DISAGREE ADVISORY EICAS. CONSULTED QRH AND DETERMINED FO ALTIMETER WAS THE ISSUE AT APPROX 300 HIGHER THAN CA. SWITCHED FO FLIGHT INSTRUMENTS TO ALTN AIR DATA AND EICAS MESSAGE EXTINGUISHED. WITH TRANSPONDER IN R POSITION ATC VERIFIED REPORTED ALT WAS 200 FEET OFF (HIGH). INSPECTED ALL PITOT STATIC-PROBE PER MM 34-11-01-6, FOUND SMALL DEBRIS STUCK IN FRONT OF FORWARD STATIC PORT ON FIRST OFFICER PITOT-STATIC PROBE. CLEANED DEBRIS, NO OTHER DEFECT FOUND. PER FIM 34-26-00-810-803, INSPECTED BOTH AOA SENSORS, STATIC PORTS, WATER IN STATIC SYSTEMS, ALSO PERFORMED ADM'S TEST PER MM 34-26-03-4. ALL TEST PASSED. A/C OK FOR SERVICE.