What was found
(CAN) AFTER TAKE-OFF, UPON SELECTION OF GEAR UP THE FLIGHT CREW OBSERVED THAT THE #2 HYDRAULIC QUANTITY WENT TO ZERO ACCOMPANIED WITH ASSOCIATED CAUTION/WARNING LIGHTS. AN EMERGENCY WAS DECLARED, AND THE AIRCRAFT RETURNED TO THE DEPARTURE AIRPORT LANDING WITHOUT ANY FURTHER INCIDENT. MAINTENANCE TROUBLESHOOTING FOUND THAT THE RIGHT-SIDE LINE TO THE NOSE LANDING GEAR DRAG STRUT TO BE LEAKING. LINE REPLACED IAW THE AMM AND THE AIRCRAFT RETURNED TO SERVICE. (LINE PN DSC252B4-0124), HOURS: 66134, CYCLES: 81328 (TC# 20190425009)