Narrative:

At or between 10 feet to 50 feet AGL during takeoff rotation; two canadian geese flew across our nose with about 120 degrees right aspect angle. I saw the birds and attempted a very slight upward rotation to avoid them; however impact occurred shortly thereafter; into the number 1 engine. I elected to leave the landing gear down and the takeoff flaps set; as I did not know if the birds hit the nose or nose gear. The impact felt very hard; like it was to the lower front of the aircraft. I continued the takeoff climb to 1000 feet AGL; and then started a right turn out and climb to 2000 feet. After impact; there was a very loud bang and instantaneous heavy vibration in the airframe.both the first officer and I noticed a smell of burning bird in the cockpit. I reduced the power setting on the number 1 engine with no noticeable reduction in the vibration. I called for the engine fire; seizure; and separation checklist and noticed high vibration on the number 1 engine; approximately 3.3. I pulled the thrust down to idle on the number 1 engine and noticed little to no vibration thereafter. As the first officer was reading the checklist; I made the decision to leave the engine running at idle and to transition to the single engine landing checklist. I informed the flight attendants of the situation; and that we were returning to land. I did not brief the passengers as we were very busy. I started the APU and set up for the ILS.tower was concerned about our flight path. I directed the first officer to reply we were turning right base to final and prepared to land. On final we ran the before landing checklist and were losing sight of the runway due to heavy rain. On short final we saw the runway with good visibility to land. We landed and taxied clear; at which time I briefed the passengers on what had happened. We taxied to the gate without incident and shut down.things happened very; very fast and I rushed the QRH checklist. We missed one item; to select flap inhibit; which gave us a too low flaps warning on final approach. Due to our heavy weight and flaps 15 configuration; it was very hard to slow down. Due to the rain; I was thinking we might have to go around; but when we broke out; we were on glide path and about vref plus 20 knots fast; but slowing as we passed over the overrun. Landing thereafter was uneventful.

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Original NASA ASRS Text

Title: B737-700 flight crew reported returning to the departure airport after a bird strike in the Number 1 engine that caused significant vibration.

Narrative: At or between 10 feet to 50 feet AGL during takeoff rotation; two Canadian geese flew across our nose with about 120 degrees right aspect angle. I saw the birds and attempted a very slight upward rotation to avoid them; however impact occurred shortly thereafter; into the Number 1 engine. I elected to leave the landing gear down and the takeoff flaps set; as I did not know if the birds hit the nose or nose gear. The impact felt very hard; like it was to the lower front of the aircraft. I continued the takeoff climb to 1000 feet AGL; and then started a right turn out and climb to 2000 feet. After impact; there was a very loud bang and instantaneous heavy vibration in the airframe.Both the First Officer and I noticed a smell of burning bird in the cockpit. I reduced the power setting on the number 1 engine with no noticeable reduction in the vibration. I called for the Engine Fire; Seizure; and Separation Checklist and noticed high vibration on the number 1 engine; approximately 3.3. I pulled the thrust down to idle on the number 1 engine and noticed little to no vibration thereafter. As the FO was reading the checklist; I made the decision to leave the engine running at idle and to transition to the Single Engine Landing Checklist. I informed the Flight Attendants of the situation; and that we were returning to land. I did not brief the passengers as we were very busy. I started the APU and set up for the ILS.Tower was concerned about our flight path. I directed the FO to reply we were turning right base to final and prepared to land. On final we ran the Before Landing Checklist and were losing sight of the runway due to heavy rain. On short final we saw the runway with good visibility to land. We landed and taxied clear; at which time I briefed the passengers on what had happened. We taxied to the gate without incident and shut down.Things happened very; very fast and I rushed the QRH Checklist. We missed one item; to select flap inhibit; which gave us a too low flaps warning on final approach. Due to our heavy weight and flaps 15 configuration; it was very hard to slow down. Due to the rain; I was thinking we might have to go around; but when we broke out; we were on glide path and about VREF plus 20 knots fast; but slowing as we passed over the overrun. Landing thereafter was uneventful.

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.