Narrative:

On takeoff roll out of ZZZ runway 25 at approximately 100 KTS; we saw a bird go under the nose and heard a bang like it hit the aircraft but we weren't sure where. After takeoff we felt some vibration and heard the left engine louder than normal. We noticed that left engine N1 vib was at 5.0 while right engine was below 1.0. All other indications looked normal on both engines. We leveled off at 10000 ft MSL and when the power came back; the vibration stopped and N1 vib also was normal. However; when we started a climb to 15000 ft MSL; the vibration returned and the indication was about 4.7. At this time the flight attendants at 1L and 2L called to tell us about the vibration. We then reduced the power in the climb to keep vibrations down and continued up to FL190 since we were approaching high terrain and we were in and out of WX due to thunderstorm in the foothills. We initiated a call to maintenance and did a little troubleshooting basically figuring that a bird had probably been ingested in the left engine and was causing the vibration. Anytime we advanced the throttle towards climb power the indications returned so we elected to return to ZZZ. We left the engine at lower power so there was no real problem with any more vib. We elected to leave the engine running and did not declare an emergency. ZZZ control vectored us in fairly quickly and we landed uneventfully. Nice job by everyone. Looked at the engine after landing and saw 2 blades bent but no bird remains.

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Original NASA ASRS Text

Title: A B767 STRUCK A BIRD ON TKOF DAMAGING AN ENG. THE ACFT RETURNED TO LAND WITH FAN BLADE DAMAGE.

Narrative: ON TKOF ROLL OUT OF ZZZ RWY 25 AT APPROX 100 KTS; WE SAW A BIRD GO UNDER THE NOSE AND HEARD A BANG LIKE IT HIT THE ACFT BUT WE WEREN'T SURE WHERE. AFTER TKOF WE FELT SOME VIBRATION AND HEARD THE L ENG LOUDER THAN NORMAL. WE NOTICED THAT L ENG N1 VIB WAS AT 5.0 WHILE R ENG WAS BELOW 1.0. ALL OTHER INDICATIONS LOOKED NORMAL ON BOTH ENGS. WE LEVELED OFF AT 10000 FT MSL AND WHEN THE PWR CAME BACK; THE VIBRATION STOPPED AND N1 VIB ALSO WAS NORMAL. HOWEVER; WHEN WE STARTED A CLB TO 15000 FT MSL; THE VIBRATION RETURNED AND THE INDICATION WAS ABOUT 4.7. AT THIS TIME THE FLT ATTENDANTS AT 1L AND 2L CALLED TO TELL US ABOUT THE VIBRATION. WE THEN REDUCED THE PWR IN THE CLB TO KEEP VIBRATIONS DOWN AND CONTINUED UP TO FL190 SINCE WE WERE APCHING HIGH TERRAIN AND WE WERE IN AND OUT OF WX DUE TO TSTM IN THE FOOTHILLS. WE INITIATED A CALL TO MAINT AND DID A LITTLE TROUBLESHOOTING BASICALLY FIGURING THAT A BIRD HAD PROBABLY BEEN INGESTED IN THE L ENG AND WAS CAUSING THE VIBRATION. ANYTIME WE ADVANCED THE THROTTLE TOWARDS CLB PWR THE INDICATIONS RETURNED SO WE ELECTED TO RETURN TO ZZZ. WE LEFT THE ENG AT LOWER PWR SO THERE WAS NO REAL PROB WITH ANY MORE VIB. WE ELECTED TO LEAVE THE ENG RUNNING AND DID NOT DECLARE AN EMER. ZZZ CTL VECTORED US IN FAIRLY QUICKLY AND WE LANDED UNEVENTFULLY. NICE JOB BY EVERYONE. LOOKED AT THE ENG AFTER LNDG AND SAW 2 BLADES BENT BUT NO BIRD REMAINS.

Data retrieved from NASA's ASRS site as of May 2009 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.