Accident Airbus A319-131 N801UA, Monday 9 May 2011
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Date:Monday 9 May 2011
Time:04:06 LT
Type:Silhouette image of generic A319 model; specific model in this crash may look slightly different    
Airbus A319-131
Owner/operator:United Airlines
Registration: N801UA
MSN: 686
Year of manufacture:1997
Total airframe hrs:47316 hours
Engine model:IAE V2522-A5
Fatalities:Fatalities: 0 / Occupants: 125
Other fatalities:0
Aircraft damage: None
Location:Chillicothe, Missouri -   United States of America
Phase: En route
Nature:Passenger - Scheduled
Departure airport:Phoenix-Sky Harbor International Airport, AZ (PHX/KPHX)
Destination airport:Chicago-O'Hare International Airport, IL (ORD/KORD)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
No adverse weather was forecast for the route. The seatbelt sign was turned off at FL320. The airplane leveled off at a final cruise altitude of 37,000' and the ride was smooth up until the turbulence encounter. Both the captain's and first officer's weather radar was in use before and during the turbulence event, and there was no adverse weather along the route visible on radar. The flight crew received no weather updates from Air Traffic Control, no pilot reports (PIREPS), and there was no traffic along the same route in front of this flight.

Evaluation of the winds using FDR data revealed that the aircraft sustained strong and adverse wind fluctuations on all three axes during the turbulence encounter, which included an upwards vertical wind gradient was about 80 knots in a 10 second timeframe. Recorded ground weather radar information revealed that the flight was probably passing over or through the extreme top of a rapidly developing area of convective weather at the time of the turbulence encounter. Although ground based radar reflectivity data indicated that the precipitation rate within this rapidly developing cell at the time was light to moderate, detection of the cell would likely have required active adjustment of the aircraft's weather radar system. However, the flight crew was not actively manipulating the aircraft radar at the time of the event given the lack of severe weather indications.

Probable Cause: An inadvertent encounter with unforecast convective turbulence.

Accident investigation:
Investigating agency: NTSB
Report number: DCA11FA053
Status: Investigation completed
Duration: 2 years
Download report: Final report




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