Narrative:

We were doing a ZZZ/ZZZ1 turn with aircraft XXX. The first flight was completed uneventfully. The return flight was uneventful until the initial descent into ZZZ. The first officer was the PF. As he added thrust at our level off altitude, he asked me if I felt or heard a vibration. I know that some of these airplanes, particularly the EMB140's, make a slight growling noise at idle thrust in flight. Initially, I thought this was what he was referring to. However, he clarified that the noise was only audible during the initial engine acceleration from the idle position. We experimented a little with the thrust levers and were able to identify the noise as coming from the #2 engine, only when moving the thrust lever from the idle position. As we continued our descent and approach into ZZZ, the sound seemed to become more pronounced. The engine vibration gauges appeared normal, however, the hp vibration for engine #2 was slightly higher than the others 'maybe halfway between the bottom of the green and the amber scale.' we debated whether to even write it up, because it was so subtle, but during taxi we noticed the noise was even more pronounced, perhaps due to less ambient noise, but it was definitely abnormal, so we notified maintenance. I waited for the mechanic so I could talk to him directly, and he wheeled up a ladder to look into the engine to find anything obvious. He looked in the front and back of the engine and did not notice anything abnormal. He did say that they would take the aircraft to the hangar and check it out. Callback conversation with reporter revealed the following information: the reporter stated the airplane was removed from service for investigation of the engine vibration and was returned to service the next day. The reporter said the airplane was routed south and into a different maintenance sector and data was not available from the maintenance computer.

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Original NASA ASRS Text

Title: AN EMB145 R ENG HAD ABNORMAL VIBRATION WHEN MOVING THRUST LEVER FROM IDLE STOP. VIBRATION MORE PRONOUNCED ON GND DURING TAXI.

Narrative: WE WERE DOING A ZZZ/ZZZ1 TURN WITH ACFT XXX. THE FIRST FLT WAS COMPLETED UNEVENTFULLY. THE RETURN FLT WAS UNEVENTFUL UNTIL THE INITIAL DSCNT INTO ZZZ. THE FO WAS THE PF. AS HE ADDED THRUST AT OUR LEVEL OFF ALT, HE ASKED ME IF I FELT OR HEARD A VIBRATION. I KNOW THAT SOME OF THESE AIRPLANES, PARTICULARLY THE EMB140'S, MAKE A SLIGHT GROWLING NOISE AT IDLE THRUST IN FLT. INITIALLY, I THOUGHT THIS WAS WHAT HE WAS REFERRING TO. HOWEVER, HE CLARIFIED THAT THE NOISE WAS ONLY AUDIBLE DURING THE INITIAL ENG ACCELERATION FROM THE IDLE POS. WE EXPERIMENTED A LITTLE WITH THE THRUST LEVERS AND WERE ABLE TO IDENT THE NOISE AS COMING FROM THE #2 ENG, ONLY WHEN MOVING THE THRUST LEVER FROM THE IDLE POS. AS WE CONTINUED OUR DSCNT AND APCH INTO ZZZ, THE SOUND SEEMED TO BECOME MORE PRONOUNCED. THE ENG VIBRATION GAUGES APPEARED NORMAL, HOWEVER, THE HP VIBRATION FOR ENG #2 WAS SLIGHTLY HIGHER THAN THE OTHERS 'MAYBE HALFWAY BTWN THE BOTTOM OF THE GREEN AND THE AMBER SCALE.' WE DEBATED WHETHER TO EVEN WRITE IT UP, BECAUSE IT WAS SO SUBTLE, BUT DURING TAXI WE NOTICED THE NOISE WAS EVEN MORE PRONOUNCED, PERHAPS DUE TO LESS AMBIENT NOISE, BUT IT WAS DEFINITELY ABNORMAL, SO WE NOTIFIED MAINT. I WAITED FOR THE MECH SO I COULD TALK TO HIM DIRECTLY, AND HE WHEELED UP A LADDER TO LOOK INTO THE ENG TO FIND ANYTHING OBVIOUS. HE LOOKED IN THE FRONT AND BACK OF THE ENG AND DID NOT NOTICE ANYTHING ABNORMAL. HE DID SAY THAT THEY WOULD TAKE THE ACFT TO THE HANGAR AND CHK IT OUT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE WAS REMOVED FROM SVC FOR INVESTIGATION OF THE ENG VIBRATION AND WAS RETURNED TO SVC THE NEXT DAY. THE RPTR SAID THE AIRPLANE WAS ROUTED S AND INTO A DIFFERENT MAINT SECTOR AND DATA WAS NOT AVAILABLE FROM THE MAINT COMPUTER.

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.