What was found
FLIGHT CREW REPORTED 1 MINUTE AFTER TAKEOFF ON CLIMBOUT, A-SYSTEM HYDRAULIC QUANTITY DROPPED TO 0 AND A-SYTEM LOW PRESSURE LIGHTS ON. EXTENDED LDG MANUALLY AND RETURNED TO LAND OVERWEIGHT AT ANC WITHOUT INCIDENT. CHANGED RMLG LOCK OPERATED SEQUENCE VALVE PER 727 MM 32-32-31 DUE APPROX 2 INCH CRACK IN VALVE BODY. ACCOMPLISHED OVERWEIGHT LANDING INSPECTION. CHANGED A-SYSTEM CASE DRAIN FILTERS AND NR 1 ENGINE HYD PUMP. PERFORMED LANDING GEAR RETRACTION TEST.