Narrative:

Aircraft was operating in cruise at fl 360. The left engine initially experienced a strong vibration and momentary roll back which was also noticed by the passengers and cabin crew. It appeared that that there was an approximate 20% reduction of N1. We disengaged the auto throttles and reduced power. This stopped the vibration and the engine seemed stable. We began a descent to FL240. As we started the descent the cabin tried to notify us of what happened. Since the mechanic had also gone to the cabin we opened the cockpit door and communicated what was going on. While descending we sent an ACARS (aircraft communications and reporting system) message to dispatch to let them know our situation and so they could advise of preferred diversion airports. While dispatch was checking for diversion airports we notified the passengers and flight attendants that everything was currently stable and as long as it stayed that way we would continue to our destination. If we had to divert we would advise them what our planned diversion airport was. As both of us searched through our jeppesen app it was discovered that the recent update and deleted all of the airport in country from our coverage. Since shutting down a currently operating engine and diverting into an airport that we had no charts for did not seem like the best course of action we decided to continue as long as the engine was stable. The engines remained stable with no noticeable vibration for the remainder of the cruise portion. The power was approximately 76% N1 and the only noticeable change was the left engine egt and fuel flow was registering a larger split. All other gauges seemed normal. On our descent into ZZZZ no noticeable vibration or engine indications were noticed; however there was a brief flash of the overhead look up annunciation that was flashing for the flight data recorder. This happened possibly 4 times all less than a second. The aircraft was configured for a normal landing as it seemed the engine was responding appropriately. After the aircraft started down the glide slope the left engine vibration returned. We reconfigured for a flaps 15 landing and idled the left engine this stopped the vibration. We landed uneventfully and taxied to customs. While taxiing the left engine oil bypass annunciation began to flash momentarily. At this point the engine was shut down and we taxied the remaining way to customs. Upon shut down the mechanic and PIC (pilot in command) conducted a visual inspection of the engine and no visible damage was noticed.left engine vibration and roll back of N1. Engine was stable at lower altitudes and power settings.the cause of the engine vibration is still unknown. The was an MEL (minimum equipment list) for the left engine a fire detection loop that was currently listed in the logbook and on the release.power was reduced and aircraft descended. Vibration stopped until short final. It was tough to determine possible diversion airports since no airport data was currently in jeppesen application.

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Original NASA ASRS Text

Title: Air Carrier flight crew reported missing Jeppesen charts for an entire country during a diversion.

Narrative: Aircraft was operating in cruise at FL 360. The left engine initially experienced a strong vibration and momentary roll back which was also noticed by the passengers and cabin crew. It appeared that that there was an approximate 20% reduction of N1. We disengaged the auto throttles and reduced power. This stopped the vibration and the engine seemed stable. We began a descent to FL240. As we started the descent the cabin tried to notify us of what happened. Since the mechanic had also gone to the cabin we opened the cockpit door and communicated what was going on. While descending we sent an ACARS (Aircraft Communications And Reporting System) message to Dispatch to let them know our situation and so they could advise of preferred diversion airports. While Dispatch was checking for diversion airports we notified the passengers and flight attendants that everything was currently stable and as long as it stayed that way we would continue to our destination. If we had to divert we would advise them what our planned diversion airport was. As both of us searched through our Jeppesen app it was discovered that the recent update and deleted all of the airport in country from our coverage. Since shutting down a currently operating engine and diverting into an airport that we had no charts for did not seem like the best course of action we decided to continue as long as the engine was stable. The engines remained stable with no noticeable vibration for the remainder of the cruise portion. The power was approximately 76% N1 and the only noticeable change was the left engine EGT and Fuel Flow was registering a larger split. All other gauges seemed normal. On our descent into ZZZZ no noticeable vibration or engine indications were noticed; however there was a brief flash of the OVERHEAD look up annunciation that was flashing for the Flight Data Recorder. This happened possibly 4 times all less than a second. The aircraft was configured for a normal landing as it seemed the engine was responding appropriately. After the aircraft started down the glide slope the Left engine vibration returned. We reconfigured for a flaps 15 landing and idled the Left engine this stopped the vibration. We landed uneventfully and taxied to customs. While taxiing the Left engine oil bypass annunciation began to flash momentarily. At this point the engine was shut down and we taxied the remaining way to customs. Upon shut down the mechanic and PIC (Pilot In Command) conducted a visual inspection of the engine and no visible damage was noticed.Left engine vibration and roll back of N1. Engine was stable at lower altitudes and power settings.The cause of the engine vibration is still unknown. The was an MEL (Minimum Equipment List) for the Left Engine A fire detection loop that was currently listed in the logbook and on the release.Power was reduced and aircraft descended. Vibration stopped until short final. It was tough to determine possible diversion airports since no airport data was currently in Jeppesen application.

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.