What was found
(CAN) ABOUT AN HOUR INTO THE FLIGHT, THE CREW RECEIVED A HYD 2 LOW CAUTION MESSAGE. THE NR 2 HYD SYS QTY WAS READING ZERO. THE FLIGHT RETURNED TO THE DEPARTURE AIRPORT SAFELY. INVESTIGATION FOUND A CHAFED HYD LINE IN THE CARGO COMPARTMENT AREA. THE LINE WAS CHAFING AGAINST A BROKEN CLAMP ON AN ADJACENT LINE. THE CHAFED LINE WAS REPLACED AS WELL AS THE BROKEN CLAMP AND THE ACFT WAS RETURNED TO SERVICE. HYDRAULIC LINE, PN AE717812-1 (IPC 29-17-06, FIG 1C-128). CLAMP, PN BBDREF001927143 (IPC 29-17-06, FIG 4A-480). ACFT TSN 19544, CSN 9848.