Boeing 747-422 N173UA

Summary

On 29 July 2011 at about 05:58 local time, a Boeing 747-422 registered N173UA, operated by United Airlines, was involved in an accident near Tangshan, China. 386 people were on board and one was seriously injured, 4 had minor injuries. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

29 July 2011 at 05:58

Classification

Accident

Location

Tangshan, China

Coordinates

39.5452, 118.1680

Aircraft

Boeing 747-422

Registration

N173UA

Category

Airplane

Engines

4

Operator

United Airlines

Operating rule

Part 121: Air Carrier

Phase of flight

Not recorded

Route

Beijing → San Francisco

Aircraft damage

Not recorded

Weather

VMC

Light

Day

NTSB number

DCA11FA091

1 person was seriously injured.

an inadvertent encounter with convectively induced turbulence likely due to radar limitations and convective weather developing upwards into the flight path.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The flight crew reported a normal takeoff and climbout with a small amount of clouds and rain in the area. The preflight weather briefing package included a forecast of convective activity including a SIGMET (significant meteorological information) for thunderstorms south of the Beijing area moving northeastward. The crew was aware of the potential for convective activity during the climbout from Beijing, and the initial enroute segment over the Bohai Sea. During flight, the Captain was actively using the airborne weather radar to search for convective returns, including using the Doppler functions. Satellite imagery showed a signature termed “transverse banding” which is indicative of thunderstorms and turbulence at altitude. Based on the lack of weather radar returns, the Captain kept the cabin seat belt sign illuminated, but advised the cabin crew that they could begin service. The airplane encountered convectively induced turbulence, resulting in a peak vertical acceleration of over 2 G’s. The activity was likely developing upwards into the flight path, and precipitation attenuation and/or radar over-scanning may have contributed to the lack of visibility of the condition, which led to the risk assessment to allow the flight attendants to begin service. Following the turbulence encounter, the flight crew controlled the airplane appropriately to avoid an overspeed or other hazardous condition. The flight and cabin crew consulted with a physician passenger and determined continuing the flight per the injured flight attendant’s desire, was appropriate.

Quoted verbatim from the NTSB record.