Date: 202005
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Weather elements / visibility: Thunderstorm
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Engine
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Human factors: Troubleshooting; Workload
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I was the Pilot Flying throughout the leg including the single engine landing. As we were descending from cruise and deviating around enroute weather; we were in the clear deviating far from any cells; we started hearing a repetitive muffled pounding sound that seemed like the flight attendants banging on a cart; or a sound along those lines. It wasn't too loud as to startle us; but strange. I looked at our engine instruments and all seemed normal at that point as our power was reduced for the descent. There was no great adverse yaw due to little power and the autopilot being on. Shortly after hearing the noise and asking each other what that could be; the flight attendants called up and reported a banging noise coming from the number one engine.  We could feel very tiny vibrations. I looked at the gauges and remember seeing both N1's in the 40% range; with no engine limits exceeded. I increased power on both engines; and sure enough; I got no response from the number one engine. It appeared to just be windmilling or providing idle power possibly.After confirming the power loss while on the interphone with the flight attendants; we [advised ATC] due to an engine failure; and we were given direct routing. Pilot Monitoring ran the appropriate checklist which led to shutting down and securing the number one engine as the EGT was high and we felt some minor vibrations. Just before completely shutting the engine down; the ENG FAIL light did eventually illuminate. The Pilot Monitoring answered repeated questions with ATC and since we were in a descent; things were moving fast. There we lots of cells out there I had to deviate around. I focused on flying the airplane and keeping control. I was able to leave the autopilot engaged and trimmed the aircraft as appropriate. ATC came back and said there was a thunderstorm building on the field that was not moving away.  As we got closer; we had ATC ask the tower the current conditions and the status on that thunderstorm cell. Since it hadn't moved; winds were increasing; and possibly having to go IMC to land in the Pilot Monitoring after discussing it with me; requested a diversion to an airport where the sky was clear; winds light; a long runway; and no weather in sight.After completing the checklist and coordinating with ATC; at some point we changed the destination in the FMC and notified Dispatch. The passengers were also briefed of the situation both earlier about the engine failure; and later about the diversion. The flight attendants were also rebriefed about the diversion. We also requested to have emergency trucks standing by. I briefed the new approach and reviewed the engine failure profile; single engine go-around procedure again; and requested direct to a fix prior to the FAF so we could get stable. I flew the engine out profile as trained to an uneventful hand flown approach and landing. After clearing the runway; we contacted the emergency vehicle on another frequency and they confirmed everything looked normal. One of the trucks followed us to the terminal and we parked at the gate. As we opened the door; Maintenance came on board. We deadheaded to our scheduled overnight on an Airbus that was coming in about an hour to resume our trip.  The Pilot Monitoring communicated very well and great CRM throughout the whole flight.  He always asked for my inputs; as well as I did his. We had flown together several times over the years which led to good camaraderie and CRM.  I feel we worked well as a team and were well trained to complete the mission in this most stressful situation.  Both of us have extensive experience and many years flying the 737. I want to say the flight attendants did a good job calming passengers on both our flight and the flight back that we deadheaded on. At some point the Chief Pilot contacted the Captain.




Synopsis: B737 pilot reported diverting due to an engine failure.