Narrative:

While cruising at FL340; just west of E180 in smooth air and with the seatbelt sign off; we encountered moderate turbulence caused be a preceding B747-400 at FL350. He had passed us a little earlier; and while we were offset one mile to the right; he was right on the airway. The wind had been a slight right crosswind; which changed to a direct tailwind. The offset assured that we stayed well right of his wake. As the preceding aircraft was approximately 15 miles ahead of us; the wind changed to a slight left crosswind; causing us to encounter his wake turbulence. We immediately turned left; removing the offset; and the turbulence ceased; having lasted approximately 30 seconds. The seatbelt sign was turned on during the encounter. Our crew rest started right after the encounter; and as I entered the cabin; I was informed by another crewmember; that a flight attendant in the back of the airplane had been injured. I went back to the aft galley; where I found her sitting on the floor; in obvious pain; with an ice pack on her right shoulder. I asked her if there was anything I could do to help her and offered to have paramedics meet the airplane. She did not feel that was necessary; but later on asked for a flight attendant supervisor to meet the airplane. We sent a message to the station with that request; and were surprised to find that nobody met the airplane. I again spoke with the injured flight attendant as we left the airplane; and while she seemed to be doing a lot better; she still appeared to be in pain when moving her shoulder.

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Original NASA ASRS Text

Title: A B777 encountered wake turbulence from a preceding B747-400 a thousand feet above them in the mid Pacific.

Narrative: While cruising at FL340; just west of E180 in smooth air and with the seatbelt sign off; we encountered moderate turbulence caused be a preceding B747-400 at FL350. He had passed us a little earlier; and while we were offset one mile to the right; he was right on the airway. The wind had been a slight right crosswind; which changed to a direct tailwind. The offset assured that we stayed well right of his wake. As the preceding aircraft was approximately 15 miles ahead of us; the wind changed to a slight left crosswind; causing us to encounter his wake turbulence. We immediately turned left; removing the offset; and the turbulence ceased; having lasted approximately 30 seconds. The seatbelt sign was turned on during the encounter. Our crew rest started right after the encounter; and as I entered the cabin; I was informed by another crewmember; that a flight attendant in the back of the airplane had been injured. I went back to the aft galley; where I found her sitting on the floor; in obvious pain; with an ice pack on her right shoulder. I asked her if there was anything I could do to help her and offered to have paramedics meet the airplane. She did not feel that was necessary; but later on asked for a flight attendant supervisor to meet the airplane. We sent a message to the station with that request; and were surprised to find that nobody met the airplane. I again spoke with the injured Flight Attendant as we left the airplane; and while she seemed to be doing a lot better; she still appeared to be in pain when moving her shoulder.

Data retrieved from NASA's ASRS site as of April 2012 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.