What was found
AIR TURNBACK, CAPT''S INSTRUMENT LOSS, UNCOMMANDED ROLL. AT FL 370, RIGHT AP ENGAGED, AIRCRAFT BEGAN A SLOW ROLL TO LEFT WITH RIGHT AILERON CORRECTION. LOST DATA INPUT TO AIRSPEED, ALTIMETER, IVSI, AND CABIN PRESSURE STARTED CLIMBING. EEC BITE CHECK SHOWED FAILED LEFT AIR DATA COMPUTER. REPLACED AIR DATA COMPUTER IAW MM 34-12-01, TEST OK. RECOMMENDATION: REMAIN OPEN PENDING RESULTS OF TEARDOWN REPORT.