What was found
PASSING FL 200 THE ALT DISAGREE EICAS MESSAGE ALONG WITH THE AURAL ALERT ACTIVATED MOMENTARILY AND THE AGAIN PASSING FL 220. FOLLOWED QRH. EICAS MESSAGE EXTINGUISHED. THE CAPTAINS ALTIMETER WAS 200 FEET DIFFERENT FROM THE F/O AND THE STANDBY ALTIMETERS. REF WRI 34-10/1543 L ADRU HAS BEEN PLACED ON MEL 34-26-01-01 IN FRA FOR THE SAME REASON AFTER ANALYSIS OF EVENT AND FOLLOWING FIM, SUSPECTED L AOA TO BE THE ROOT CAUSE OF THE ALTITUDE DISCREPANCY. IT WAS REPLACED UNDER WRI 34-10/1550. PRESSURISED THE CAPT STATIC SYSTEM IAW AMM 34-11-00-2 UP TO 25,000 FT USING AIR DATA TEST SET. THE DIFFERENCE OF ALTITUDE BETWEEN CAPT PFD AND AIR DATA TEST SET WAS LESS THAN 10 FEET AND MAINTAINED THIS FOR OVER ONE MINUTE. TEST SATISFACTORY.