Narrative:

Climbing through approximately 5000 ft, first officer and I noticed a cyclical vibration in the airframe. The aircraft would vibrate every 45 seconds to 1 min for approximately 1-2 seconds. The vibration was very deep (low) frequency. Climbing through 10000 ft, I called my flight attendant to see if she noticed any vibration. She did not. First officer engaged the autoplt and I contacted company maintenance. We began troubleshooting the problem, but could not find any obvious culprit. Engine vibration was steady, all hydraulic indications were normal and no EICAS warning messages or status messages were present. I asked the first officer to disengage the autoplt at approximately 16500 ft to see if he could feel vibration in the controls. At approximately 17500 ft, the aircraft rolled violently to the right. Within 15-30 seconds, the aircraft rolled again. I told center that we needed an immediate return to ZZZ1. As we began the turn, I recognized that ZZZ was within 50 mi. I told center we needed ZZZ. I had my flight attendant prepare the cabin for an emergency landing. We landed ZZZ uneventfully.

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Original NASA ASRS Text

Title: A CL65 FLT CREW EXPERIENCED A VIBRATION, THEN LATER HAD THE ACFT VIOLENTLY ROLL TO THE R 2 TIMES.

Narrative: CLBING THROUGH APPROX 5000 FT, FO AND I NOTICED A CYCLICAL VIBRATION IN THE AIRFRAME. THE ACFT WOULD VIBRATE EVERY 45 SECONDS TO 1 MIN FOR APPROX 1-2 SECONDS. THE VIBRATION WAS VERY DEEP (LOW) FREQ. CLBING THROUGH 10000 FT, I CALLED MY FLT ATTENDANT TO SEE IF SHE NOTICED ANY VIBRATION. SHE DID NOT. FO ENGAGED THE AUTOPLT AND I CONTACTED COMPANY MAINT. WE BEGAN TROUBLESHOOTING THE PROB, BUT COULD NOT FIND ANY OBVIOUS CULPRIT. ENG VIBRATION WAS STEADY, ALL HYD INDICATIONS WERE NORMAL AND NO EICAS WARNING MESSAGES OR STATUS MESSAGES WERE PRESENT. I ASKED THE FO TO DISENGAGE THE AUTOPLT AT APPROX 16500 FT TO SEE IF HE COULD FEEL VIBRATION IN THE CTLS. AT APPROX 17500 FT, THE ACFT ROLLED VIOLENTLY TO THE R. WITHIN 15-30 SECONDS, THE ACFT ROLLED AGAIN. I TOLD CTR THAT WE NEEDED AN IMMEDIATE RETURN TO ZZZ1. AS WE BEGAN THE TURN, I RECOGNIZED THAT ZZZ WAS WITHIN 50 MI. I TOLD CTR WE NEEDED ZZZ. I HAD MY FLT ATTENDANT PREPARE THE CABIN FOR AN EMER LNDG. WE LANDED ZZZ UNEVENTFULLY.

Data retrieved from NASA's ASRS site as of July 2007 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.