What was found
(CAN) PILOT REPORTED LANDING GEAR FAILED TO LOCK UP IN RETRACTED POSITION. GEAR WAS SELECTED DOWN AND EMERGENCY HAND PUMP WAS USED TO LOCK GEAR IN PLACE. THE AIRCRAFT WAS THEN FLOWN TO MAINTENANCE BASE WITH GEAR DOWN. THIS SYSTEM HAS THE HYDRAULIC PUMP PRESSURE SWITCH ON THE NITROGEN SIDE OF THE ACCUMULATOR. WHEN THE SWITCH WAS REMOVED THERE WAS HYDRAULIC FLUID IN THE NITROGEN SIDE OF THE ACCUMULATOR. THE ACCUMULATOR WAS REPLACED AND GEAR RETRACTION AND EXTENSION FUNCTIONAL TEST CARRIED OUT.