What was found
DURING CRUISE FLIGHT AT 28000' WITH THE ACFT COUPLED TO FIRST OFFICERS SIDE & FIRST OFFICER FLYING, ALTIMETER & ISI MATCH WITH 29.92 SET, CAPTAINS ALTIMETER SHOWING APPROX 150 FEET LOW. COUPLED FIRST OFFICERS TO CAPTAIN SIDE & AUTO PILOT ADJUSTED TO CAPTAIN ALTIMETER. ISI & FIRST OFFICERS ALTIMETER CONTINUED TO MATCH. SWAPPED AGAIN & AUTO PILOT MATCHED. FIRST OFFICERS ALTIMETER & CAPTAIN ALTIMETER AGAIN LOWER. DURING DESCENT FROM ALTITUDE, TRANSFERRED TO NRWC 513-ORD-02153. R & R BOTH PITOT STATIC TUBES IAW AMM 34-11-01. CHECK GOOD IAW AMM 34-13-01. REF NRWC 513-ORD-02161 FOR RII LEAK CHECK. REF NRWC 513-ORD-02153 FOR WORK ACCOMPLISHED. PITOT STATIC TUBE LT FWD PN 0856KV9 & SN 261775.