What was found
FLT 510 - MEM-MCO - HAD AN A SYSTEM HYDRAULIC QUANTITY THAT SLOWLY DECREASED TO ZERO. COMPLIED WITH ALL AOM PROCEDURES, AND DECLARED AN EMERGENCY. THE AIRCRAFT RETURNED TO MEM AND LANDED SAFELY, WITHOUT ANY FURTHER DIFFICULTIES. UPON INVESTIGATION, FOUND THE CASE DRAIN LINE AND ALSO REPLACED NR 1 AND NR 2 ENGINE DRIVEN PUMPS DUE TO A LOSS OF ALL FLUID. SERVICED, BLED SYSTEM, AND OPERATIONALLY CHECKED SYSTEM GOOD IAW BOEING MM. THE AIRCRAFT WAS RETURNED TO SERVICE. (M)