Incident Overview
On July 29, 2011, at 0558 UTC, United Airlines Flight 888, a Boeing 747-422 (registration N173UA), encountered severe turbulence during climbout from Beijing International Airport, China. The flight was en route to San Francisco International Airport, California. At the time, the aircraft was climbing through approximately 23,000 feet near Tangshan, China.
Injuries
One flight attendant sustained a fractured right fibula. Four other flight attendants reported minor injuries from falls and impacts with galley equipment, but were able to continue their duties. The four flight crew members, the remaining ten flight attendants, and 366 passengers (including one lap child) were not injured.
Flight and Crew Actions
The captain, aged 59, had approximately 18,500 total flight hours, including about 7,600 hours as pilot-in-command on the Boeing 747. The first officer, aged 62, had about 10,212 total flight hours, with 8,557 hours on the Boeing 747. Two relief pilots were also seated in the cockpit.
The crew reported a normal takeoff and climbout after multiple ground delays. The captain noted that the seatbelt sign was illuminated, but cabin crew were advised they could begin service at their discretion. Flight attendants had just started cabin service when the aircraft encountered a violent jolt. The captain disengaged the autopilot, maintained climb pitch attitude, and reduced throttle to avoid overspeed. Recorded flight data showed a peak vertical acceleration exceeding 2 G, with fluctuations lasting about 20 seconds. After the turbulence subsided, the captain reengaged the autopilot and notified air traffic control.
Post-Event Actions
The purser informed the captain that the flight attendant at door 5L was injured with a possible broken fibula. A physician who was a passenger on board examined her and noted a severely sprained ankle with possible fibula fracture, but did not recommend an immediate diversion. The injured flight attendant expressed a desire to continue to the United States for medical attention. The captain, physician, and flight attendant agreed that immediate medical attention was not required. The captain coordinated with dispatch, and paramedics were arranged to meet the aircraft upon arrival at SFO. The purser moved the injured flight attendant to a business class seat, applied a makeshift splint, elevated her leg, and applied ice.
Aircraft and Weather Information
The Boeing 747-422, serial number 24380, was equipped with four Pratt & Whitney 4056 engines and had about 83,255 total flight hours. No relevant maintenance issues were noted, and post-flight severe turbulence inspection revealed no damage.
Weather conditions included a cold front producing extensive clouds and embedded convective activity. Satellite imagery showed embedded convection near the accident location. A SIGMET warned of embedded thunderstorms with tops to 33,000 feet. The National Weather Service High Level Significant Weather Prognostic Chart indicated a line of isolated embedded thunderstorms along the planned route. The preflight dispatch noted potential embedded thunderstorms and en route turbulence.
Survival Aspects
The seatbelt sign was illuminated during the encounter. United Airlines procedures allowed flight attendants to be out of their seats with the seatbelt sign on unless pilots instructed otherwise.