What was found
AIRCRAFT EXPERIENCED A HYDRAULIC B LEAK AND AN ASSOCIATED HYD LOW VOL AMBER CAS MESSAGE. THE FLIGHT CREW ELECTED TO RETURN TO LNK. AN EMERGENCY WAS DECLARED, AND THE AIRCRAFT LANDED UNEVENTFULLY. MAINTENANCE WAS CONTRACTED TO INSPECT AND REPAIR THE AIRCRAFT. TECHNICIANS FOUND AN O-RING PACKING (P/N NAS1612-10) ON THE R/H HYDRAULIC LOW-PRESSURE SWITCH (ST016) TO BE PROTRUDED FROM THE UNION TEE FITTING. THE FAILED PACKING WAS REMOVED AND REPLACED. HYDRAULIC SYSTEM LEAK CHECKS WERE COMPLETED WITH NO DEFECTS NOTED. THE AIRCRAFT WAS SUBSEQUENTLY RETURNED TO SERVICE WITH NO FURTHER DISCREPANCIES.