What was found
ENROUTE TO DESTINATION, AIRPORT CREW NOTICED THE ILLUMINATION OF THE LOW HYDRALIC PRESSURE ANNUNCIATORS FOLLOWED BY A DECREASE IN HYDRAULIC SYSTEM PRESSURE ON THE PRESSURE GAUGE. CREW RETURNED TO THE DEPARTURE AIRPORT AND PERFORMED MANUAL GEAR EXTENSION AND LANDED WITHOUT INCIDENT. FURTHER INVESTIGATION BY MAINTENANCE FOUND THE HYD SYSTEM RETURN LINE B-NUT AFT OF THE NR 2 FIREWALL LOOSE. MAINT. CHANGED BOTH HYD PUMPS AND SYSTEM FILTERS AND RETORQUED B-NUT.