Boeing 737 724 N23708 accident near Port Arthur, Texas

Probable cause

an inadvertent encounter with clear air turbulence.

NTSB analysis

On March 14, 2016, 2156 central daylight time, United Airlines flight 898,a Boeing 737-724, N23708, encountered turbulence during cruise that resulted in one flight attendant sustaining a serious injury near Port Arthur, Texas. There were no injuries to the other passengers and crew aboard and the airplane was not damaged. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight from the George Bush Intercontinental Airport (IAH), Houston, Texas to the Louis Armstrong New Orleans International Airport (MSY), New Orleans, Louisiana.

According to flight crew statements, the captain was the flying pilot and the first officer (FO) was the pilot monitoring. The airplane was level at flight level (FL) 270, with the autopilot off, in clear air with no convective activity in the vicinity. Immediately before before beginning the descent into IAH, the flight encountered a momentary pocket of moderate to severe turbulence with the airplane banking approximately 25 – 30 degrees to the right, and the altitude fluctuating from 100 feet up to 60 - 160 feet down. The flight crew did not recall seeing anything on the onboard weather radar or TCAS (traffic collision avoidance system). The captain immediately turned on the seat belt sign and made an announcement on the public address for the passengers to fasten their seat belts. Shortly after, the flight crew were informed that a flight attendant FA was injured. The captain called the cabin and was informed that one of the FAs was severely injured. The flight crew declared a medical emergency and arranged for paramedics to meet the flight at the gate. The FA was transported to a local hospital and diagnosed with serious injuries.

According to a weather analysis conducted by United Airlines, satellite imagery indicated no significant cloud features over the route of flight, with the moisture channel imagery indicating moisture channel darkening or drier air in the middle tropospheric levels across the northern half of Texas and southern Los Angeles with increasing moisture further to the south with the stronger jet stream winds. A review of pilot reports (PIREPs) across the region leading up to the turbulence only indicated light turbulence being encountered. Consequently, The Weather Company forecasts only called for light turbulence for the route. However, several Aircraft Meteorological Data and Reporting (AMDAR) automated reports across the region indicated that winds were stronger than predicted at higher levels and indicated a strong vertical wind shear at higher levels than originally forecast.

Text from the NTSB. Open the NTSB docket for DCA16CA181 for the full record.