B737-700
Flight Crew Last 90 Days 123; Flight Crew Type 6000
Aircraft Equipment Problem Critical; Inflight Event / Encounter Bird / Animal
Aircraft Aircraft Damaged; Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution
Environment - Non Weather Related
Flock of medium white birds flew in front of aircraft at liftoff; and I immediately heard loud groan/whine from Engine Number 1. All engine indications were normal except the Number 1 Engine vibration monitor indicated 1.5 vs .5 for Engine Number 2.We notified ATC of a likely bird strike; and First Officer continued flying aircraft with vectors around field as a precaution.We accomplished the QRH 'Immediate Action' items for engine limit/surge/stall due to the abnormal engine noise. Upon reducing power on the Number 1 Engine; the noise was reduced. We completed the QRH procedure and elected to leave the affected engine running since no abnormal indications other than noise. Captain coordinated with Dispatch and Maintenance who noted that since vibrations not greater than 4.0; we could continue. We did not like the noise and elected to return as a precaution to prevent further damage. We computed landing data and flew an uneventful approach and landing to the longer runway. We shut down the affected engine after one minute and returned to the gate. Damage to the Number 1 Engine (3 blades) was noted on post-flight inspection as well as bird strikes on right landing gear and underside of right elevator. We coordinated with Dispatch; Scheduling; Maintenance in ZZZ1 and the ZZZ Tower for necessary repair and reporting.
B737 encountered birds after takeoff and experienced Number 1 Engine vibration. Flight crew elected to return where they found damaged blades.