What was found
IN CRUISE FLIGHT LEVEL 310 A SYSTEM QTY RAPIDLY DECREASED TO ZERO FOLLOWED BY A SYSTEM PRESSURE DECREASING TO ZERO. WHILE RUNNING POM OUTBOARD FLAPS FAILED TO ALT EXTEND. REPLACED NR 3 LED FLAP ACUTATOR. REPLACED NR 1 AND NR 2 HYD CASE DRAIN FILTERS. LEAK CHECK OK. RAN ENGINE OPERATION OF PUMPS AND FLAPS NORMAL. CLEANED CANNON PLUG ON OUTBOARD ALT FLAP BYPASS VALVE. OPERATION OF ALT FLAPS OPERATION NORMAL.