What was found
ON CLIMBOUT FROM AKN 3 MINUTES AFTER GEAR RETRACTION HYD WARNING LIGHTS CAME ON WITH LOSS OF HYD PRESSURE. AN EMERGENCY WAS DECLARED AND RETURNED TO AKN. PILOT NOTED ON PREVIOUS FLIGHT NOTICED SMALL PRESSURE FLUCTUATIONS BUT PRESSURE STAYED WITHIN GREEN EXCEPT ONE TIME IT REACHED YELLOW. MAINTENANCE FOUND NOSE GEAR UP LINE AT LT WING ROOT CRACKED IN BEND. A/C LANDING GEAR DEACTIVATED AND HYD SERVICED. A/C FERRIED TO ANC MAINTENANCE BASE FOR REPAIR. THIS WAS THE 3RD OCCURRENCE OF A CRACKED NOSE GEAR UP LINE IN THE LAST WEEK. FOUND HYDRAULIC ACCUMULATOR TO HAVE LOW NITROGEN CHARGE (LAST SERVICED 270 HOURS PREVIOUS) AND CHECKED ALL RIGGING OF NOSE GEAR. BOTH HYDRAULIC PUMPS REPLACED.