MD-11
Dispatch Dispatcher
Troubleshooting
Aircraft Equipment Problem Critical
Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
Aircraft X called on satcom at XA:09z located about XXXSM SE of ZZZ with a hydraulic 3 low and hydraulic 3 off issue.  Flight requested priority handling and landed without issue on runway XXC and exited left.
Cruise at FL380.  Received a Level 1 #3 Hydraulic Elev annunciation.  Looked up in QRH and it stated that the 3-2 NRMP would not work; and there were no other steps to take.  Upon verification of the Hydraulic Synoptic; the Captain and I noticed Hyd Reservoir #3 was lower than the others; and dropping.  At that time; it indicated 4.5 gallons.  #1 was 5.9 gal; #2 was 5.7 gal.  Within 5 min; the #3 reservoir was below 4 gal.  We believed we had a hydraulic leak; although there was no annunciation.  We referenced the QRH and selected Hyd - Manual; and turned off the pumps in #3.  At that point; quantity had dropped to 0.1 gal.  Within 2 minutes; the quantity displayed 12.0 gal.  We [requested priority handling] with ZZZ Center; in anticipation of receiving a Hyd #3 Fail annunciation.  We received vectors direct to ZZZ1; and started our descent.  At approx 5;000 ft; in VMC conditions; we turned on the #3 pumps; and were able to get the aircraft fully configured without issue.  We did receive the Hyd 3 Fail annunciation. The CA made a Flaps 35 landing on Runway XXC.  We were able to taxi clear and taxi to our ramp entry spot where we shut down the engines and were towed in. Maintenance did not have a guess on what caused the loss of fluid in Hyd #3 system.
First Officer reported loss of #3 hydraulic system fluid and continued to destination airport. They required a tow to the gate due to loss of nose wheel steering associated with the loss of #3 system.