What was found
AFTER T/O WHEN GEAR LVR WAS RAISED TO THE UP POS THE HYD SYS (A) RESERVOIR WENT TO ZERO. THE GEAR REMAINED DOWN AND FLAPS STAYED AT 15 DEG. REMOVED AND REPLACED PACKING AND UNION FOR THE OB TE FLAP CONTROL VALVE IAW IPC REF 27-50-00-30AZZ ITEM 145. LEAK AND OP CK, GOOD ON ENG RUN. DEBRIEF INDICATED THAT (A) PUMPS OPERATED FOR 15 MIN AT ZERO QTY. REMOVED AND REPLACED NR 1 AND NR 2 ENG DRIVEN HYD PUMPS IAW MM 29-11-033-4. REMOVED AND REPLACED BOTH NR 1 AND NR 2 ENG HYD CASE DRAIN FILTERS. SERVICED AND CYCLED ALL FLT CONTROLS NUMEROUS TIMES AND RESERVICED HYD AFTER SHUTDOWN.