What was found
AT CRUISE FL 310, AUTOPILOT 1 ENGAGED, WITH NO WARNING THROTTLES ADVANCED TO FWD STOP, A/S ON CAPT SIDE INDICATED 87 KTS, SPD LIM FLG DISPLAYED, ECAM DISPLAYED "FWD TRANSFER ONLY" NO OTHER ECAM INFO.FOLLOWED QRH FOR ADC SINGLE FAILURE. REMOVED AND REPLACED #1 ADC AS REQ. IAW A300-600 AMM CH 34-11-04 AND PERFORM AFS LAND TEST IAW A300-600 AMM CH 22-40-00 GRND OPS CKS GOOD A/C RETURN TO SERVICE