B747 flight crew experiences possible bird strike shortly after gear retraction; which is confirmed by maintenance upon landing 14 hours later. The right side engines both had fan damage requiring replacement.
Synopsis
B747 flight crew experiences possible bird strike shortly after gear retraction; which is confirmed by maintenance upon landing 14 hours later. The right side engines both had fan damage requiring replacement.
Narrative
Flight time today was just under 14 hours. On takeoff during second segment climb a flock of small birds flew underneath the nose crossing our path from my left to right. With the size of our 747 we felt that we had to have hit some of them. My eyes were focused on the motors. The instrumentation for the motors never showed any indication of a problem. Gear and flap retraction were completed and after discussing it with the crew we decided to continue on to destination and just monitor everything carefully. At the 5 hour point in the flight fuel burn and time enroute matched the flight time exactly. At top of descent we were actually ahead on gas. We notified Maintenance of the possible bird strike and had them do a thorough inspection. Damage was found in both the number 3 and 4 engines as well as to one of the flaps. My understanding is that both motors had about 5 bent fan blades each that needed to be replaced. This plane flew 14 hours without any vibration on those engines and no increase in fuel burn. Pretty amazing. The only thing that I would add to the diagnostic side of the departure would have been to have system maintenance monitor the engine parameters enroute with their equipment just to make sure that a vibration wasn't developing that wasn't being shown on our instrumentation.
Second reporter narrative
During gear retraction Captain stated he saw birds pass left to right under aircraft. There were no indications of any impact. Upon arrival at the aircraft for our return flight; maintenance reported we had struck some birds.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.