BOEING 747-422 near Pacific Ocean — 2013-02-19

Probable cause

The flight’s encounter with moderate clear air turbulence while en route, which resulted in a serious injury to a flight attendant. Contributing to the accident was the lack of communication equipment in the rest compartment, which, if installed, could have alerted the cabin crewmembers that the seatbelt sign was on.

Contributing factors

Contributing to the accident was the lack of communication equipment in the rest compartment, which, if installed, could have alerted the cabin crewmembers that the seatbelt sign was on.

NTSB narrative

The flight crew reported that the flight experienced unexpected light-to-moderate turbulence during cruise flight for about 3 hours. The seatbelt sign was illuminated, and the passengers and flight attendants had been seated. A flight attendant, who was on her rest break and was resting in the bunk room, reported that the turbulence had stopped for a while and that she thought she heard a "faint ding" indicating that the seatbelt sign had been turned off, so she went to the lavatory. However, the flight then encountered moderate turbulence, during which the flight attendant sustained a serious injury while walking from her bunk to the lavatory. The flight attendant reported that announcements made over the public address system could not be heard in the bunk room and that it was not always possible to hear when the seatbelt sign was turned on or off. It is likely that, if the flight attendant had a visual indication that the seatbelt sign was on, she would not have attempted to get up until safe movement was assured.

Analysis

Primary failure mode

Environmental

First missed decision gate

Decision to continue on course despite SIGMET indicating potential severe turbulence.

NTSB coding

• Turbulence encounter · Enroute-cruise

Evidence available

• FDR / data
• 11 docket documents

Docket documents11

• Flight Data Recorder Datafdr
• Flight Data Recorder Factual Reportfdr
• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• Captain Statementinterview
• First Officer D. Byrne Statementinterview
• First Officer J. Bouley Statementinterview
• First Officer J. Herbig Statementinterview
• Flight Attendants Statementsinterview
• Statement of Party Representatives to NTSB Investigationinterview
• Flight Plan Weather Briefother
• Meteorology 5 - Weather Studyother

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