NTSB Factual Report

On December 26, 2006, about 1812 Pacific standard time, while taxiing to the runway, Southwest Airlines flight 1011, a Boeing 737-7H4, N207WN, collided on the ground with Southwest Airlines flight 1092, a Boeing 737-3A4, N673AA, that had been pushed back from its gate at San Diego International Airport, San Diego, California. Southwest Airlines Company was operating both airplanes as scheduled domestic passenger flights under the provisions of 14 Code of Federal Regulations (CFR) Part 121. The airline transport pilot licensed captain, first officer, 3 flight attendants, and 72 passengers on flight 1011 were not injured. The airplane received minor damage. The airline transport pilot licensed captain, first officer, 3 flight attendants, and 126 passengers on flight 1092 were not injured. The airplane was substantially damaged. Flight 1011 was departing as a non-stop to Las Vegas, Nevada, and flight 1092 was departing as a non-stop to San Jose, California. Visual meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan had been filed for both airplanes.

Flight Data Recorders (FDR)

An engineer in the Safety Board's Vehicle Recorder Division received electronic files containing FDR data from both airplanes. The engineer correlated data from each FDR to their Greenwich Mean Time (GMT) data, and then calculated the relationships for each set of FDR data. This data was used to change the elapsed FDR subframe reference number data to FDR GMT. However, the engineer pointed out that GMT data comes from each airplane's captain's clock, and those times could be slightly different, which would affect the established time base.

The plotted data indicated that the taxiing airplane turned to the right (away from the stationary airplane) about 26.5 degrees while moving at a maximum ground speed of 11 knots. It then turned about 2.5 degrees back to the left (towards the stationary airplane) while the brakes were applied, and it stopped. About 8 seconds after coming to a stop, it began moving forward. It collided with the other airplane about 2 seconds later at a recorded groundspeed of 3 knots.

Cockpit Voice Recorders (CVR)

A Safety Board specialist reviewed the cockpit voice recorders from both airplanes and prepared a summary of selected events that occurred during the event.

Flight 1092 was at gate 5. The crew received pushback clearance, and was advised of a company airplane taxing from gate 1 at 1810:06. After pushback, the ground crewman asked the captain to set the brakes. The captain responded that the brakes were set at 1811:39. About 21 seconds later, there were sounds of the impact, and the captain made an exclamation. The first officer and ground crewman exclaimed that another airplane had made contact with them. Thirteen seconds after the impact, the first officer broadcast the word stop four times over the radio.

Flight 1011 was at gate 1, and requested pushback clearance from ground control at 1807:50. The captain had the airplane pushed back, started engines, and advised that the brakes were set at 1809:14. About 52 seconds later, the CVR picked up a radio transmission from ground control that cleared the airplane at gate 5 for pushback. There was no acknowledgement from the flight 1011 crew to indicate that they heard this transmission. The crew commenced setting flaps and performing taxi checklist items. Ground control cleared the airplane to taxi to runway 27, and told them at 1810:46 to use caution because of the company airplane pushing back from gate 5. The first officer (FO) acknowledged the transmission. The captain indicated that they should use caution regarding that airplane; the FO reiterated the caution and clearance to runway 27.

During taxi, the FO indicated that so far they were doing good, and that there was plenty of room on his side if the captain needed to swing it his way a little. The captain indicated that if he swung the airplane it would move the wing. A few seconds later, the FO asked if they had made contact. The CVR recorded the four stop transmissions from the other flight crew, but there was no indication that the crew heard them. The captain asked what they hit, and the FO responded that he didn't know, but it was on the captain's side.

The left winglet from the taxiing airplane, flight 1011, struck the right horizontal stabilizer of the stopped airplane, flight 1092. The top half of the winglet sheared off, and imbedded itself in the horizontal stabilizer just outboard of the elevator.

NTSB Probable Cause

Failure of the captain, during taxi, to maintain adequate clearance from an occupied airplane stopped on the ramp.