What was found
UPON REACHING CRUISE ALT FL310, AIRCRAFT EXPERIENCED TOTAL SYSTEM A HYD FAILURE. ACCOMPLISHED ''A'' SYSTEM HYDRAULIC FAILURE CHECKLIST, IAW AOM VOL 1 EMERGENCY PROCEDURES. DECLARED AN EMERGENCY AND RETURNED TO MIAMI, DID NOT DUMP FUEL. FOUND 3 WAY VALVE IN LEFT WHEEL WELL WITH ACTUATOR AND BODY SEPARATED AND THE FOUR ATTACHING SCREWS CRACKED. REPLACED 3 WAY VALVE PER MM 29-11-62. SERVICED HYDRAULIC SYSTEM PER MM 12-12-00. OPS CHECK OK. (M)