What was found
ON CLIMBOUT, LOST HYDRAULIC SYSTEM PRESSURE, STOPPED QUANTITY LOSS AT 6 GALLONS INDICATED. LOSS OF HYDRAULIC SYSTEM AND PRESSURE EMERGENCY CHECKLIST FOLLOWED. MAINTENANCE REPLACED THE O-RING IN THE SLOT CONTROL VALVE MOUNT, SERVICED THE HYDRAULIC SYSTEM. HYDRAULIC POWERED FLT CONTROLS OPERATED NORMALLY ON GROUND CHECK, NO LEAKS NOTED.