Narrative:

Climbing out of about 20;000 feet; speed about 295 kts; V/south about 2000 feet per minute we experienced sudden significant and strong aircraft vibrations. Vibrations were more pronounced in the aft of the aircraft and seemed to originate from the tail section. According to the aft flight attendants it was intensity of vibration they have never felt before. We were in absolute smooth air. We did not have any abnormal engine vibrations and no other warning messages associated with the vibrations. After leveling off at 27;000 feet and reducing the airspeed to about 270 kts the vibrations stopped. We ran the QRH checklist for aircraft vibrations. Then we got in contact with [ops] and maintenance control. We discussed the event and since all indications were back to normal; we concurred to continue on to [destination]. We also agreed that if vibrations would return we would divert to [a nearby alternate]. About 10 minutes later we experienced another event of vibrations; this time not as strong; would call it light vibrations. Still; we made the decision to divert at this point. I used ACARS to inform dispatch. Dispatch acknowledged and gave us diversion info. We diverted and landed without further incident. During the descent and approach phase we felt more light vibrations; however we could not tell for sure that it was not turbulence related. After deplaning and taking care of the passengers I made a very detailed log book write up in accordance with QRH.to prevent other flight crews experiencing an event like that I would like to see serious maintenance attention and really trying to find the cause of the problem. The aircraft was placed back into service and considered green after only a general visual inspection based on a certain amm task card. No panels were opened and no computer flight control checks and tests were performed.

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Original NASA ASRS Text

Title: A319 Captain reported diverting to an alternate after experiencing significant airframe vibration.

Narrative: Climbing out of about 20;000 feet; speed about 295 kts; V/S about 2000 feet per minute we experienced sudden significant and strong aircraft vibrations. Vibrations were more pronounced in the aft of the aircraft and seemed to originate from the tail section. According to the aft flight attendants it was intensity of vibration they have never felt before. We were in absolute smooth air. We did not have any abnormal engine vibrations and no other warning messages associated with the vibrations. After leveling off at 27;000 feet and reducing the airspeed to about 270 Kts the vibrations stopped. We ran the QRH checklist for aircraft vibrations. Then we got in contact with [ops] and maintenance control. We discussed the event and since all indications were back to normal; we concurred to continue on to [destination]. We also agreed that if vibrations would return we would divert to [a nearby alternate]. About 10 minutes later we experienced another event of vibrations; this time not as strong; would call it light vibrations. Still; we made the decision to divert at this point. I used ACARS to inform dispatch. Dispatch acknowledged and gave us diversion info. We diverted and landed without further incident. During the descent and approach phase we felt more light vibrations; however we could not tell for sure that it was not turbulence related. After deplaning and taking care of the passengers I made a very detailed log book write up in accordance with QRH.To prevent other flight crews experiencing an event like that I would like to see serious maintenance attention and really trying to find the cause of the problem. The aircraft was placed back into service and considered green after only a general visual inspection based on a certain AMM task card. No panels were opened and no computer flight control checks and tests were performed.

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.