Date: 202007
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class B ZZZ
Aircraft component: Oil Cooler
Component problem: Improperly Operated; Malfunctioning
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Communication Breakdown
Second reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Chart Or Publication; Human Factors; Procedure; Aircraft
Primary problem: Human Factors

Narrative: Went out to Aircraft X for turnover; there were 6 mechanics assigned to do the workload. There was a [Malfunction A] and a [Malfunction B] that needed to be changed. There was one mechanic from swing shift at the airplane. The swings mechanic was asked which engine had [Malfunction A] and what engine had [Malfunction B]. The swing shift mechanic said [work on Malfunction B] was done and gestured towards the #2 eng - which the removed [component] was placed near the paperwork table by the # 2 eng. The #1 eng needed [Malfunction A addressed] which we were standing next to during the turnover. I assumed [Malfunction B] was on #2 eng that needed leak check. We finished up [Malfunction A] on #1 eng and pushed out plane and leaked checked #2 eng. The A/C left ZZZ and lost oil pressure on #1 eng. Then diverted to ZZZ1. Actually the #1 [component] was changed and was the eng that should have been leak checked. The write up in the log book for tracking purposes did not specify what eng it was; the job card did not specify what engine and I was going by the swing shift turnover which the mechanics that changed the [component for Malfunction B] were not present.A lack of communication between mechanics; leads; supervisors. The mechanic that performed the job was not present on what eng or what needed to be accomplished. So I assumed only leak check on #2 eng was all that was needed so we just focused on [fixing Malfunction A].Better communication; Eng clarification of Job card.


Second narrative: I was PF (Pilot Flying) climbing through FL 270 when we got an indication of low oil qty on L engine. FO (First Officer) took over as PF while I linked through Dispatch to [Maintenance Control]. It was decided that with all other indications being normal; we would continue. Ten mins later; oil pressure started to drop slowly so we turned around to air abort back to ZZZ. After 10-15 mins oil press dropped enough to trigger an ECAM alert which called for engine shutdown. ECAM and QRH were completed to secure the engine while we [coordinated] with ATC and request to divert to ZZZ1 which was the closest airport. Dispatch was notified and coordinated our arrival there. We made a visual approach to Rwy XX with myself being PM (Pilot Monitoring). We landed at max landing weight with plenty of rwy. Taxied clear of the active to have ARFF (Airport Rescue and Fire Fighting) inspect us before we taxied to the gate under our own power. Oil was evident under the L engine as noticed by ARFF. Once at the gate; we deplaned the pax and Mx took over the a/c.The a/c hadn't flown in a few days and had some Mx work done. It was difficult to determine whether the indication of low oil quantity was correct until it was verified by low oil pressure. Maintenance oversight?


Synopsis: A321 Flight Crew reported a loss of oil quantity followed by loss of oil pressure causing the number 1 engine to be shut down and a diversion.