Narrative:

We were enroute when I called the flight attendants to advise them of expected turbulence as we descend into [our destination]. I asked them to clean up the cabin early so as to be done and seated prior to the choppy air at the lower altitudes. Just a few seconds later; my first officer (first officer) said that he would like to use the lavatory prior to landing. We also had a company captain observer on the jump seat; and he expressed interest in doing the same. My first officer went first and returned promptly then the observer left. As I recall we were given a descent clearance to fl 350 as the first officer initiated the descent; the observer called to come back to the flight deck. I got up from my seat to check the door viewer and open the door and as I returned to my seat we started to get some vibration or bumps. Within a few seconds the flight attendants called to ask about the noise and vibration.as I was explaining to them we were entering some chop; I noticed that the autothrottle had disconnected and the #2 engine was rolling back. I tried to move the thrust lever but had no response. After realizing what we were dealing with I set cont thrust in the FMC and found the single engine drift down speed. I immediately asked ATC for a lower altitude. I told the first officer to continue to fly the aircraft while I got out the engine failure/shutdown checklist. As I was going to the QRH; I re-assessed the situation and felt that the engine fire/severe damage checklist may be more appropriate because of the engine vibration we felt (nothing abnormal on the avi.) as we performed the checklist and shutdown the engine; the vibration stopped. At that point we also had the 'engine fail' annunciation. We never had a fire or overheat light. Our flight deck observer was extremely helpful in helping me with communication to dispatch; flight attendants and the passengers.I had initially told ATC that most likely we would land at ZZZ (landing alternate for our destination.) we were given a direct clearance to ZZZ airport. However; after attaining the weather for both ZZZ and zZZ1 I felt that in the interest of safety that ZZZ1 would be a better option as both were approximately the same distance. My concerns for landing at ZZZ were turbulence; moderate icing on descent and gusty crosswinds on the long runway or a much shorter runway with favorable winds. My concern was I knew we would have additional speed with a flap 15 (ice) landing with a fairly heavy weight landing of about 127;500 pounds. The decision was made to land at ZZZ1 with overcast skies no ice and a smooth ride with light winds straight down a 12;000 ft runway. After all appropriate checklists; briefings and calls were made I assumed control of the aircraft and we landed at ZZZ1 without further incident. Crash fire rescue equipment (crash fire rescue) met us after landing and I stopped the aircraft on the taxiway after we cleared the runway. I wanted crash fire rescue equipment to assess any potential visual damage prior to proceeding to the gate. No apparent damage was noted so we continued to gate. Upon reaching the gate we advised the passengers that customer service agents would help accommodate them to their destinations. I then called dispatch and spoke to all of the appropriate channels to debrief the incident. This included dispatch; maintenance and the chief pilot on call. I entered a defect noting the #2 engine failure in the aircraft logbook. I then conducted an outside walk around the aircraft in particular looking at the #2 engine. Both the contract mechanic and I did not notice anything unusual or apparently abnormal with the engine. However; we did have a red egt exceedance annunciation on the ground. The highest observed egt was 788 in flight prior to shut down. The aircraft was shut down except for overnight gate services accommodations.

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Original NASA ASRS Text

Title: A B737 Captain reported an engine rollback at cruise requiring a diversion and emergency landing.

Narrative: We were enroute when I called the Flight Attendants to advise them of expected turbulence as we descend into [our destination]. I asked them to clean up the cabin early so as to be done and seated prior to the choppy air at the lower altitudes. Just a few seconds later; my First Officer (FO) said that he would like to use the lavatory prior to landing. We also had a Company Captain Observer on the jump seat; and he expressed interest in doing the same. My FO went first and returned promptly then the Observer left. As I recall we were given a descent clearance to FL 350 as the FO initiated the descent; the Observer called to come back to the flight deck. I got up from my seat to check the door viewer and open the door and as I returned to my seat we started to get some vibration or bumps. Within a few seconds the Flight Attendants called to ask about the noise and vibration.As I was explaining to them we were entering some chop; I noticed that the autothrottle had disconnected and the #2 engine was rolling back. I tried to move the thrust lever but had no response. After realizing what we were dealing with I set CONT thrust in the FMC and found the single engine drift down speed. I immediately asked ATC for a lower altitude. I told the FO to continue to fly the aircraft while I got out the Engine Failure/Shutdown Checklist. As I was going to the QRH; I re-assessed the situation and felt that the Engine Fire/Severe Damage Checklist may be more appropriate because of the engine vibration we felt (Nothing abnormal on the AVI.) As we performed the checklist and shutdown the engine; the vibration stopped. At that point we also had the 'ENG FAIL' annunciation. We never had a fire or overheat light. Our Flight Deck Observer was extremely helpful in helping me with communication to Dispatch; Flight Attendants and the Passengers.I had initially told ATC that most likely we would land at ZZZ (landing alternate for our destination.) We were given a direct clearance to ZZZ airport. However; after attaining the weather for both ZZZ and zZZ1 I felt that in the interest of Safety that ZZZ1 would be a better option as both were approximately the same distance. My concerns for landing at ZZZ were turbulence; moderate icing on descent and gusty crosswinds on the long runway or a much shorter runway with favorable winds. My concern was I knew we would have additional speed with a flap 15 (ice) landing with a fairly heavy weight landing of about 127;500 pounds. The decision was made to land at ZZZ1 with overcast skies no ice and a smooth ride with light winds straight down a 12;000 ft runway. After all appropriate checklists; briefings and calls were made I assumed control of the aircraft and we landed at ZZZ1 without further incident. CFR (Crash Fire Rescue) met us after landing and I stopped the aircraft on the taxiway after we cleared the runway. I wanted CFR to assess any potential visual damage prior to proceeding to the gate. No apparent damage was noted so we continued to Gate. Upon reaching the gate we advised the Passengers that Customer Service Agents would help accommodate them to their destinations. I then called Dispatch and spoke to all of the appropriate channels to debrief the incident. This included Dispatch; Maintenance and the Chief Pilot on Call. I entered a defect noting the #2 engine failure in the aircraft logbook. I then conducted an outside walk around the aircraft in particular looking at the #2 engine. Both the Contract Mechanic and I did not notice anything unusual or apparently abnormal with the engine. However; we did have a red EGT exceedance annunciation on the ground. The highest observed EGT was 788 in flight prior to shut down. The aircraft was shut down except for overnight gate services accommodations.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.