Narrative:

During initial climb both pilot flying (PF) and myself heard a really loud thud followed by a vibration felt in the floor; our seats and the control column. This occurred below 10;000 and above 5000. It happened again and again for a total of 4-5 times; followed by smaller thuds. After the first instance we both looked at each other thinking the flight attendant (flight attendant) might have dropped something on the floor; but I commented we weren't through 10 yet. We also checked the systems pages for any abnormalities... Everything showed normal; and also nothing appeared on the EICAS. We chatted with the flight attendant a bit and she stated she hadn't dropped anything and she heard the noise as well. Several passengers also noted that noise. It happened again and again after passing 10;000 and it occurred more frequently. This all seemed very concerning to us because this was something neither of us had ever encountered. We decided after a few mins that we needed to head back and ATC instructed us to level at FL190. We [advised ATC of situation] because we thought it was the prudent thing to do as we had no idea what was going on with the aircraft. We turned and headed back to [departure airport] with no further interruption. The PF did say he felt smaller vibrations that I could not detect. We also slowed to 220 knots because the thuds seemed to increase in intensity as we went faster. This could have been a coincidence though. No errors noted. There may be things that could be refined a bit though. I did back myself away a bit and took time to analyze the situation. I made my opinions known and we came to a mutual decision to [advise ATC] because of the unknown severity of the problem. I think we handled the situation well as a crew; with the flight attendant included. There are always things we wish we could have done better in hindsight but I feel good with the way the situation was handled by our crew.

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Original NASA ASRS Text

Title: EMB-145 First Officer reported experiencing significant aircraft vibration during climb out. The source of the vibration could not be determined and a decision was made to return to the departure airport.

Narrative: During initial climb both Pilot Flying (PF) and myself heard a really loud thud followed by a vibration felt in the floor; our seats and the control column. This occurred below 10;000 and above 5000. It happened again and again for a total of 4-5 times; followed by smaller thuds. After the first instance we both looked at each other thinking the Flight Attendant (FA) might have dropped something on the floor; but I commented we weren't through 10 yet. We also checked the systems pages for any abnormalities... everything showed normal; and also nothing appeared on the EICAS. We chatted with the FA a bit and she stated she hadn't dropped anything and she heard the noise as well. Several passengers also noted that noise. It happened again and again after passing 10;000 and it occurred more frequently. This all seemed very concerning to us because this was something neither of us had ever encountered. We decided after a few mins that we needed to head back and ATC instructed us to level at FL190. We [advised ATC of situation] because we thought it was the prudent thing to do as we had no idea what was going on with the aircraft. We turned and headed back to [departure airport] with no further interruption. The PF did say he felt smaller vibrations that I could not detect. We also slowed to 220 knots because the thuds seemed to increase in intensity as we went faster. This could have been a coincidence though. No errors noted. There may be things that could be refined a bit though. I did back myself away a bit and took time to analyze the situation. I made my opinions known and we came to a mutual decision to [advise ATC] because of the unknown severity of the problem. I think we handled the situation well as a crew; with the flight attendant included. There are always things we wish we could have done better in hindsight but I feel good with the way the situation was handled by our crew.

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.