Large Transport
Flight Crew Air Transport Pilot (ATP)
Confusion; Troubleshooting; Distraction
Aircraft Equipment Problem Less Severe
Aircraft Equipment Problem Dissipated; Flight Crew Diverted
Aircraft
Climbing out of about 20;000 feet; speed about 295 Knots; V/S about 2;000 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 Knots the vibrations stopped. We ran the QRH checklist for aircraft vibrations. Then we got in contact with [operations command] 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 [land at a nearby airport]. 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 Aircraft Maintenance Manual task card. No panels were opened and no computer flight control checks and tests were performed.
A flight crew experienced sudden significant and strong aircraft vibrations while climbing out of 20;000 feet in smooth air. The vibrations stopped after they leveled off and reduced power. Ten minutes later lower intensity vibrations returned and they elected to divert. The report was submitted because the reporter would like to see serious maintenance attention and really trying to find the cause of the problem.