Pilot Debrief

BOEING 747-422 near Tangshan — 2011-07-29

Final reportDCA11FA091
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Date
2011-07-29
Location
Tangshan, CN
Aircraft
BOEING 747-422
Registration
N173UA
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Climb

Probable cause

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

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.

Analysis

Primary failure mode
Environmental
First missed decision gate
Captain could have delayed cabin service until clear of turbulence.

NTSB coding

Evidence available

  • FDR / data
  • ADS-B / radar
  • 11 docket documents
View NTSB final reportView NTSB docket

Docket documents11

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