What was found
STARTING AT FL260, FO€™S VSI BECAME ERRATIC AND FLUCTUATED CONSTANTLY BETWEEN 300 FPM AND 1000 FPM WHILE CAPTAINS REMAINED CONSTANT AT 500 FPM. FO€™S ALTITUDE TAPE FLUCTUATED BETWEEN LEVELING OFF AND CLIMBING RAPIDLY, CORRESPONDING WITH VSI READINGS. IN CRUISE, FO€™S VSI FLUCTUATED +/-200 FPM. VSI AND ALTIMETER APPEARED TO OPERATE NORMALLY DURING DESCENT. PERFORMED UNRELIABLE AIR DATA CHECK, FOUND WATER IN ADC-2 STATIC DRAIN TUBE, EMPTIED DRAIN TUBE; CHECKED ADC-2 COMPUTER FOR TIGHTNESS IN THE RACK, RE-SECURED COMPUTER; ALL HEATERS CHECK GOOD. OPS CHECK GOOD AT THIS TIME. WORK DONE IAW AMM.