What was found
(CAN) ON APPROACH THE HYD 3 LOW PRESS CAUTION LIGHT CAME ON, THE NR 3 HYD SYS QTY WAS OBSERVED AT 5 PERCENT. AN ALTERNATE GEAR EXTENSION WAS CARRIED OUT AND EMERGENCY DECLARED. THE ACFT LANDED UNEVENTFULLY. MAINTENANCE INVESTIGATION FOUND A HYDRAULIC LEAK AT THE PRESSURE PORT FITTING ON THE 3B HYDRAULIC PUMP. THE O-RING AND BACKUP RING WERE REPLACED, THE SYS SERVICED WITH FLUID AND SYSTEM CHECKS COMPLETED. O-RING, PN NAS1611-111, AIPC 29-12-03, FIG 1-95. AIRCRAFT TSN 33615, CSN 25867.