Narrative:

During cruise; we noticed a blinking hydraulic alert light. Checked hydraulic page and we had a LVL1 'hydraulic 3 elev off' alert. Hydraulic 3 quantity was 4.7. While referencing the QRH for the alert the hydraulic 3 quantity slowly continued to decrease. As we were just past [a nearby alternate]; we contacted [dispatch] to discuss the issue with [them] and [maintenance]. While discussing the issue; the hydraulic 3 quantity continued to decrease; and a collective decision between my crew; [dispatch] and [maintenance] was to divert to a [nearby alternate] airport. Upon further discussion with [maintenance]; ZZZZ was chosen as the best alternative. This decision was based on the high probability that we would experience a complete hydraulic 3 failure and it was better to divert rather then fly 7 hours without hydraulic 3. QRH did not require 'land at nearest suitable airport;' but the decision was collectively made due to the lack of divert options while on the route.[ATC was advised] and they proceeded to route us to ZZZZ via vectors. Enroute; fuel dumping was required and the dump information required for the dump report was pasted to [dispatch] after we landed. When the hydraulic 3 quantity dropped to 3.5; the initial lvl 1 alert went away and we received a lvl 1 'hydraulic 3 off.' at this point; the hydraulic 3 quantity stabilized and we cruised for approximately 45 minutes with no quantity loss. During descent into ZZZZ I elected to use spoilers; and when I deployed the spoilers the hydraulic 3 quantity slowly began to decrease. As the quantity dropped to approximately 2.0 when we were overhead the airport; we elected to extend the spoilers and landing gear to see if they would fully deploy while we had remaining fluid. Both the spoilers and landing gear did safely deploy; however; the hydraulic 3 quantity dropped to 0.8 and we received a lvl 2 'hydraulic 3 fail.' as we had prepared for this to occur; we flew a flaps 35 approach to runway xxl. As we had limited turn capability to the right; we elected to stop straight ahead on the runway and be towed to parking. Since the APU was MEL'd inoperative; after shutting down engine 3 after landing; we elected to keep engine one running as our electrical source and to provide constant hydraulic pressure to brake system number 1 during the tow in. We then shut down engine number 2 and were towed to the gate.first officer and relief officer did an outstanding job of coordinating with ATC and maintenance about the issues of stopping on the runway; coordinating for the tow in; and ensuring that all ground personnel were aware of engine 1 being required to remain running due to our system limitations presented by this scenario. After block in; maintenance discovered a damaged hydraulic line in the number 3 engine.

Google
 

Original NASA ASRS Text

Title: MD-11 Captain operating on an oceanic flight reported observing a steady deterioration of the #3 hydraulic system quantity. A diversion to a suitable airport was successfully accomplished.

Narrative: During cruise; we noticed a blinking HYD alert light. Checked HYD page and we had a LVL1 'HYD 3 ELEV OFF' alert. HYD 3 quantity was 4.7. While referencing the QRH for the alert the HYD 3 quantity slowly continued to decrease. As we were just past [a nearby alternate]; we contacted [Dispatch] to discuss the issue with [them] and [Maintenance]. While discussing the issue; the HYD 3 quantity continued to decrease; and a collective decision between my crew; [Dispatch] and [Maintenance] was to divert to a [nearby alternate] airport. Upon further discussion with [Maintenance]; ZZZZ was chosen as the best alternative. This decision was based on the high probability that we would experience a complete HYD 3 failure and it was better to divert rather then fly 7 hours without HYD 3. QRH did not require 'land at nearest suitable airport;' but the decision was collectively made due to the lack of divert options while on the route.[ATC was advised] and they proceeded to route us to ZZZZ via vectors. Enroute; fuel dumping was required and the dump information required for the dump report was pasted to [Dispatch] after we landed. When the HYD 3 quantity dropped to 3.5; the initial LVL 1 alert went away and we received a LVL 1 'HYD 3 OFF.' At this point; the HYD 3 quantity stabilized and we cruised for approximately 45 minutes with no quantity loss. During descent into ZZZZ I elected to use spoilers; and when I deployed the spoilers the HYD 3 quantity slowly began to decrease. As the quantity dropped to approximately 2.0 when we were overhead the airport; we elected to extend the spoilers and landing gear to see if they would fully deploy while we had remaining fluid. Both the spoilers and landing gear did safely deploy; however; the HYD 3 quantity dropped to 0.8 and we received a LVL 2 'HYD 3 FAIL.' As we had prepared for this to occur; we flew a flaps 35 approach to Runway XXL. As we had limited turn capability to the right; we elected to stop straight ahead on the runway and be towed to parking. Since the APU was MEL'd inoperative; after shutting down engine 3 after landing; we elected to keep engine one running as our electrical source and to provide constant hydraulic pressure to brake system number 1 during the tow in. We then shut down engine number 2 and were towed to the gate.First Officer and Relief Officer did an outstanding job of coordinating with ATC and Maintenance about the issues of stopping on the runway; coordinating for the tow in; and ensuring that all ground personnel were aware of engine 1 being required to remain running due to our system limitations presented by this scenario. After block in; Maintenance discovered a damaged hydraulic line in the number 3 engine.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.