NTSB Identification: LAX07LA127.
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Scheduled 14 CFR operation of UNITED AIRLINES
Accident occurred Thursday, April 12, 2007 in Los Angeles, CA
Probable Cause Approval Date: 12/20/2007
Aircraft: Boeing 757-200, registration: N525UA
Injuries: 1 Serious,5 Minor,106 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

While at flight level FL400 (40,000 feet) the flight deck received information about turbulence below 12,000 feet. The captain advised the flight attendants to have the cabin secured and be in their seats within 15 minutes. The first officer gave the 'prepare for landing' announcement in the descent around flight level FL250 (25,000 feet), which was after the captain had notified the flight attendants to prepare the cabin, but before the end of the stated 15 minutes. While descending through 15,500 feet, the airplane experienced a moderate 'jolt' lasting 1-2 seconds. By this time it had been more than 15 minutes since the captain gave the flight attendants the secure cabin instructions. The cabin crew reported injuries to all flight attendants and no injuries to passengers. All six flight attendants received medical attention after landing. One flight attendant was seriously injured with a closed fibular fracture; the five other flight attendants had minor injuries. The first officer said that turbulence during their departure had been very bad, therefore, in order to mitigate any passenger anxiety, when he made the 'prepare for landing' announcement, he added that the turbulence would not be as bad as it was on departure. He understood the captain's instructions to the flight attendants, and this announcement was aimed solely at the passengers. The flight attendants confirmed that they understood the captain's instructions to have the cabin cleaned up and be seated within 15 minutes. As they were finishing the cabin clean up, the first officer's 'prepare for landing' announcement indicated that the turbulence would not be as bad as they had been told to expect. The flight attendants may have interpreted this added information concerning turbulence as a relaxation of the captain's earlier instructions. The Digital Flight Data Recorder (DFDR) indicated the turbulence occurred as the aircraft was coming out of a 12-degree right bank and descending through 15,400 pressure altitude. The event lasted approximately 10-11 seconds. The bank angle of the aircraft was between 8 and 1 degrees right wing down during the event. Vertical acceleration fluctuated between .5 and 2.06 G's. Longitudinal acceleration spiked up to .2 G's about the same time as the 2 G vertical spike. Lateral acceleration fluctuated between .1 G left and .05 G's to the right during the incident. The data showed that the autopilot was engaged and in control of the aircraft during the incident.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The flight's encounter with a turbulence event that occurred while the flight attendants were unseated. Contributing to the accident was the apparent conflicting information provided by the flight deck to the flight attendants and the flight attendants' interpretation of that information.

Full narrative available

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