Date: 202111
Local time of day: 0001-0600
Location: ZZZ.Tower, US
Flight conditions: VMC
Light: Night
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Cruise
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Hydraulic Main System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Troubleshooting; Communication Breakdown; Distraction
Second reporter function: Dispatcher
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; Flight Crew Executed Go Around / Missed Approach; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: After departing ZZZ1; we got a L HYD QTY caution message. I completed the QRH procedure. We monitored the hydraulic quantity and quickly discovered that the left system was losing quantity. Pressure; however; was good. The center and right systems were fine. I reviewed the L HYD PRESS QRH procedure with the First Officer in the event that we lost system pressure. I informed Dispatch of our probable impending loss of the left hydraulic system. The First Officer and I discussed what we would do in the event of the left system failure; determined that we would continue with him as flying pilot while I performed pilot monitoring duties and ran the checklist; discussed the need to start to configure early and did everything we could do to lessen our workload. The system seemed to be holding a steady quantity at .23 and the hydraulic system pressure was normal. When we checked in with Approach; I informed the Controller of the need to slow early and that we may have a hydraulic problem. We were given Runway XXR. As we started to configure; we got the hydraulic pressure message we had anticipated. We requested priority handling. The alternate flap extension took even longer than we had anticipated and we determined that we would not be stable in time to meet the stable approach criteria and executed a go-around. ATC gave us vectors for another approach and a longer final. We were able to get configured and had an uneventful flaps 20 landing. Because of the loss of nose wheel steering; we planned to stop on the runway and be towed to the gate. This was coordinated in advance with both Dispatch and ATC. The fire rescue crew inspected the aircraft after landing as a precaution. When the tug arrived; we were towed to our gate. The person towing us was one of our mechanics who was aware that we had been a priority aircraft. We discussed what had happened and I made a write up in the electronic aircraft maintenance log. I did not include verbiage that we requested priority handling in my write up; because at the time that we were at the gate and I was completing the write up; my body was starting to come down from the adrenaline rush and; since the mechanic already knew; I simply forgot to add it to the write up.Obviously you cannot prevent equipment failures. However; it would have been nice to have a better QRH procedure or more expanded information related the HYD QTY. Such as what to do if a leak is suspected. Or maybe a note that warns that below a certain quantity; system failure is imminent; if it is.


Second narrative: The flight informed me that they had low L HYD pressure. When asked if they were requesting priority handling; they initially said no. I told them I would monitor the situation; inform recovery; and to have them message me if they were requesting priority. They requested priority after performing a go-around in ZZZ. I informed the recovery person of what happened and procedures were put in place to recover the aircraft via tow truck as they had no nose wheel steering. Flight landed safely without further incident and was towed safely. This could not have been prevented. The resulting events/procedures put in place ended up running smoothly without further incident.


Synopsis: B757 Captain and a Dispatcher reported a loss of left hydraulic system quantity on departure event. On approach to destination airport; the indications returned; causing a go-around. The Captain requested priority handling and made a precautionary landing; requiring a tow off the runway.