Boeing 737-7H4 N221WN accident near Santa Clarita, California

Probable cause

The pilot’s abrupt airplane pitch change maneuver. Contributing to the accident was the flight crew’s failure to maintain the heading specified by the air traffic controller, which would have avoided the near collision course with an unidentified airplane that triggered the traffic alert and collision avoidance system resolution advisory.

NTSB analysis

During descent to landing, the flight crew inadvertently turned about 27 degrees off their air traffic controller-assigned heading. When advised by the controller to check the airplane’s heading, the flight crew noted the heading discrepancy and immediately initiated a turn back to the assigned heading. During the turn, the flight crew received a traffic alert and collision avoidance system resolution advisory (RA). The captain responded to the RA by initiating an estimated 1,500- to 2,000-foot-per-minute rate of descent followed by an approximate 2,000-foot-per-minute climb. During the RA response maneuvers, three flight attendants were standing in the aft galley, one of whom was seriously injured.

Text from the NTSB. Open the NTSB docket for WPR10LA134 for the full record.