DC10-40 CREW HAS #3 HYD SYS FAILURE AND RETURNS TO LAND.

Narrative

AFTER LEVELOFF AT FL350 (APPROX 30 MINS INTO FLT) THE #3 ENG R HYD PUMP TEMP HIGH LIGHT ILLUMINATED WITH THE PUMP IN THE OFF POS. SYS TEMP INDICATED 58 DEGS. SYS PRESSURE ON #3 HYD INITIALLY INDICATED NORMAL AT 3000 PSI AND WAS BEING DRIVEN BY THE L HYD PUMP. SYS PRESSURE THEN BEGAN TO INCREASE TO 4000 PSI AND THE #3 ENG L HYD PUMP WAS TURNED OFF. COCKPIT OPERATING PROCS FOR BOTH TEMP HIGH LIGHT AND HIGH PRESSURE WERE COMPLETED AND A CALL TO COMPANY MAINT WAS INITIATED. SYS QUANTITY WAS NORMAL AND A SLIGHT DECREASE IN SYS TEMP WAS OBSERVED. IT WAS NOTED THAT THE #3 SYS TEMP BEGAN TO INCREASE AT A SLOW RATE AND THEN A SUDDEN LOSS OF ALL HYD FLUID IN #3 SYS WAS OBSERVED. COCKPIT OPERATING PROCS WERE COMPLETED FOR A LOSS OF ALL FLUID TO THE #3 SYS. FLT RETURNED TO MSP WITH LNDG AND APCH NORMAL FOR THE PROCS. ACFT STOPPED ON RWY AND TUGGED TO THE GATE. SUPPLEMENTAL INFO FROM ACN 467061: ON INITIAL #3 ENG START; THE R HYD PUMP LAGGED BEHIND THE L ONE; BUT OPERATED NORMALLY; WELL WITHIN ALL LIMITS. CALLBACK CONVERSATION WITH RPTR ACN 467350 REVEALED THE FOLLOWING INFO: RPTR SAID THAT THE R PUMP FOR #3 HYD SYS IS NORMALLY OFF DURING CRUISE. THIS LED TO CONFUSION OVER THE OVERHEAT INDICATION WITH THE PUMP OFF. IT WAS FOUND AFTER LNDG TO HAVE BEEN A FAILED PUMP.