What was found
PILOT REPORTED A LOSS OF HYDRAULICS DURING FLIGHT AT CRUISE FL400. INSPECTION REVEALED THAT THE RT ENGINE DRIVEN HYD PUMP PRESSURE SIDE HYDRAULIC LINE WAS LEAKING, AND ALLOW THE ACFT HYD SYS FLUID BE DEPLETED. FURTHER INSP REVEALED THAT LINE HAD FAILED INTERNALLY AND WHEN PRESSURE WAS APPLIED THE HOSE WOULD SWELL AND BEGIN TO LEAK. THE PROBABLE CAUSE OF THE FAILURE IS AGE AND POSSIBLE EMBRITTLEMENT OF THE HOSE. TO POSSIBLY PREVENT RECURRENCE OF SUCH FAILURES A TIME INTERVAL FOR REPLACEMENT OF AGING HOSES MAY BE NEEDED. (K)