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| Date: | Friday 29 July 2011 |
| Time: | 05:58 LT |
| Type: |  Boeing 747-422 |
| Owner/operator: | United Airlines |
| Registration: | N173UA |
| MSN: | 24380/759 |
| Year of manufacture: | 1989 |
| Engine model: | P&W PW4000 SER |
| Fatalities: | Fatalities: 0 / Occupants: 385 |
| Aircraft damage: | None |
| Category: | Accident |
| Location: | over Tangshan, Hebei Province -
 China
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Beijing-Capital International Airport (PEK/ZBAA) |
| San Francisco International Airport, CA (SFO/KSFO) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The flight crew of UA888 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.
Probable Cause: an inadvertent encounter with convectively induced turbulence likely due to radar limitations and convective weather developing upwards into the flight path.
Accident investigation:
 |
|
Sources:
NTSB DCA11FA091
History of this aircraft
Other occurrences involving this aircraft
| 19 February 2010 | N173UA | United Air Lines | 0 | Anchorage, AK | min | |
| Turbulence | ||||||
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 01-Jul-2023 15:43 | RDV | Updated |
Corrections or additions? ... Edit this accident description
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