NTSB Factual Report

On February 13, 2010, about 1445, Pacific standard time, a Boeing 737-7H4, N221WN, abruptly maneuvered during radar vectors for initial approach to the Bob Hope Airport, Burbank, California. At the time, the airplane was about 20 miles northwest of Burbank. The 2 pilots, 80 passengers and 1 of the 3 flight attendants were not injured. The remaining 2 flight attendants sustained a minor and a serious injury. The airplane was not damaged. The airplane was registered and operated by Southwest Airlines as Flight #2534, under the provisions of Title 14 Code of Federal Regulations Part 121. Visual meteorological conditions prevailed for the flight which was operated on an instrument flight rules flight plan. The scheduled domestic passenger flight originated from Las Vegas, Nevada, at 1354.

The Airline Transport Pilot (ATP) captain stated that he was the pilot flying and the ATP First Officer was the pilot monitoring, as they descended for landing. The Approach Air Traffic Controller (ATC) issued the flight a clearance to fly a 190-degree heading and descend to and maintain 6,000 feet. The captain stated that he set a 190 degree heading in the heading window and selected 6,000 feet in the altitude window of the airplane's mode control panel (MCP) used to set autopilot functions and was subsequently verified by the first officer.

The captain stated that as the flight continued, the controller issued a traffic information alert for traffic at their 11 o'clock position and roughly 4 miles away. The captain said that the flight crew began scanning for the traffic and received a Traffic Collision Avoidance System (TCAS) traffic advisory (TA), which identified that the traffic was about 500 feet below their airplane's altitude. The captain stated that he began to shallow the airplane's rate of descent to its assigned altitude of 6,000 feet to avoid the traffic.

Subsequently, the controller advised the flight crew to check the airplane's heading. The captain said that he noticed that he had inadvertently allowed the airplane to turn to a 163-degree heading and immediately initiated a turn back to the assigned heading of 190 degrees. During the turn, the crew received a TCAS resolution alert (RA) to descend at 1,500 to 2,000 feet per minute (fpm), followed by a command to climb at 2,000 fpm.

The captain further reported that the RA commands were followed and that during the climb portion, they observed traffic ahead of their position about 2 miles away and slightly higher in altitude. The captain stated that he responded by making a shallow turn to the right to avoid the traffic.

At the time of the accident, all of the passengers were seated with their seatbelts fastened. The flight attendants stated that all three of them were standing in the aft galley and were making their final preparations for landing. One flight attendant sustained a fractured left scapula.

NTSB 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.