United B737 near Lake Charles on Jun 12th 2012, turbulence injures 3 cabin crew

Last Update: April 25, 2020 / 15:48:33 GMT/Zulu time

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Incident Facts

Date of incident
Jun 12, 2012

Airline
United

Flight number
UA-1632

Aircraft Registration
N16709

Aircraft Type
Boeing 737-700

ICAO Type Designator
B737

A United Airlines Boeing 737-700, registration N16709 performing flight UA-1632 from Houston Intercontinental,TX to New York La Guardia,NY (USA) with 76 passengers and 5 crew, was climbing through FL280 about 50nm southwest of Lake Charles,LA just crossing the coast towards the Gulf of Mexico at around 20:21L (01:21Z Jun 13th), when the aircraft encountered severe turbulence that caused two flight attendants to receive serious and one flight attendant to receive minor injuries. The aircraft diverted to Lake Charles for a safe landing on Lake Charles's runway 33 about 16 minutes later. The three crew members were taken to a hospital.

The FAA confirmed one crew member received serious, two others minor injuries. The aircraft received no damage.

Passengers reported cabin crew was just around the aisle to serve drinks when the aircraft encountered turbulence having everyone not being strapped in to lift off and hit the cabin ceiling before crashing back onto the floor.

On Jul 7th 2012 the NTSB reported the aircraft encountered turbulence at FL225 near Winnie,TX. Two flight attendants received serious injuries, there were no serious injuries to the other occupants of the aircraft. The NTSB is investigating the accident.

On Apr 25th 2020 the NTSB released their final report concluding the probable cause of the accident was:

the flight crew's penetration of a rapidly developing thunderstorm cell in an area of forecasted convective activity. The serious injuries were the result of a misunderstanding between the captain and cabin crew regarding the potential for turbulence.

The NTSB reported two flight attendants received serious injuries.

The NTSB wrote:

The flight was scheduled to depart IAH at 1744 CDT but was delayed on the ground due to strong thunderstorms at the airport. The captain conducted a preflight briefing with the three flight attendants (FA) about 1.5 hours prior to the actual departure time without the first officer present. The captain recalled in post-accident interviews that he informed the FAs that there would be turbulence on the departure and asked them to stay seated until he contacted them. The three FAs did not recall any mention of turbulence in the pre-flight briefing and none recalled being informed to stay seated in post-accident interviews.

The flight departed IAH normally and proceeded east-southeast to avoid an area of severe weather located east of the airport. The FAs began their cabin service after the sounding of the chime and extinguishing of the blue light over the cockpit door indicating the aircraft was above the sterile cockpit altitude. Flight data recorder (FDR) data indicated the airplane was climbing through FL221 at an airspeed of 285 knots when it encountered an area of turbulence for about 10 seconds, with large fluctuations in vertical acceleration, lateral acceleration, and airspeed. The vertical acceleration fluctuated between about -0.77 g's and +1.89 g's, the lateral acceleration fluctuated between about -0.13 g's and +0.24 g's, and the airspeed fluctuated between about 261 knots and 290 knots.

At the time of the turbulence encounter, the forward FA was out of her jumpseat making a public address announcement and was thrown against the ceiling during the turbulence encounter. One of the aft FAs was unbuckled and preparing to get up in the aft galley when she was thrown against the ceiling and galley and was knocked unconscious. The other aft FA remained buckled in her seat during the turbulence encounter and was struck in the head with the cabin phone during the event. The forward FA used the inter-phone to inform the flight crew of the serious injuries. The flight crew declared an emergency and requested a return to IAH, however, ATC informed them that IAH was closing due to weather over the field. As a result, the flight diverted to LCH and medical personnel met the aircraft at the gate. All three FAs were transported to the hospital where one was diagnosed with a fractured coccyx and a lumbar strain; one suffered a collapsed lung and fractures of her right clavicle, ribs, cervical vertebrae, and pelvis.

National weather service forecasts showed a large area of convective activity over southeastern Texas and into southern Louisiana that was moving southeast. The thunderstorm at IAH that delayed the flight was part of the forecasted convective activity. The flight crew was provided weather information from dispatch that included Convective SIGMETs, Weather Watches, and company advisories warning of severe thunderstorms moving southeastward near the proposed route of flight. The flight plan routing received by the crew appeared to be clear of any strong convection, however, post-accident analysis showed the flight was proceeding east-southeast along the southern edge of the convective activity when it penetrated a rapidly developing cell of "heavy" to "extreme" intensity at their flight level. The cells developed within the 5 to 10 minutes prior to the event. The crew indicated they utilized the aircraft's onboard weather radar during the flight. Both pilots stated that the radar tilt was set to +1 degree during the flight and they identified areas of significant weather located 20 to 50 miles in front of the aircraft and to the north of their intended flight path. The weather radar tilt adjustment allows for pilots to compensate for aircraft altitude and attitude. Company guidance stated that the tilt should be set to 0 degrees or slightly down for operations between 10,000 and 35,000 feet.
Incident Facts

Date of incident
Jun 12, 2012

Airline
United

Flight number
UA-1632

Aircraft Registration
N16709

Aircraft Type
Boeing 737-700

ICAO Type Designator
B737

This article is published under license from Avherald.com. © of text by Avherald.com.
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