A330
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
Flying in cruise about 70 minutes into the flight and prior to ZZZZZ; we received an ECAM for HYD B RSVR LO LVL. The SD screen showed blue hydraulic level was nearly empty; well into the amber (though still with 3;100 PSI of pressure in the blue system). We followed the ECAM actions and turned off the blue engine and electrical hydraulic pumps. Shortly thereafter; we received another ECAM for HYD B RSVR LO AIR PR; as well as loss of the blue system pressure. We went through the ECAM procedures; then contacted Dispatch and Maintenance; brought the Relief Pilot back to the flight deck; looked through the FCOM (Flight Crew Operations Manual) and QRH; and decided that the unexplained loss of fluid; complete loss of blue hydraulics; and our proximity to ZZZ made an air turnback the prudent course of action. ATC was notified via CPDLC; we [requested priority handling] and were routed back to ZZZ. The Captain spoke to the flight attendants and the passengers; and the Relief Pilot and dispatch both did landing distance calculations. We used an early descent; speed brakes and an early gear drop to burn additional fuel and ensure we landed under max weight. After landing; we were met by emergency trucks who verified there was no additional leakage under the aircraft; then we taxied to the gate; being pulled in by the tug as a precaution.I thought the process worked as well as could be expected. The Captain solicited input accordingly and demonstrated good leadership. The cabin crew; dispatch/maintenance and ATC all did a very good job accommodating the air return and planning accordingly. I felt like we all worked together to mitigate the risk of the malfunction and bring the plane safely back to ZZZ.
A330 First Officer reported loss of hydraulic system pressure during cruise; resulting in a diversion.