Incident Overview
On May 10, 2013, at approximately 0907 mountain standard time, a Boeing 737-7H4, registration N913WN, collided with a parked, unoccupied Boeing 737-7H4, N776WN, at Sky Harbor International Airport in Phoenix, Arizona. The airplane was being pushed back from gate C-1 for a scheduled domestic passenger flight to Reno International Airport, Nevada. The pushback operation involved a single engine running and a pushback tug. The flight crew consisted of two airline transport pilots, three flight attendants, and 54 passengers; none were injured, and no ground injuries were reported. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed. The aircraft was operated by Southwest Airlines under 14 CFR Part 121.
Pushback Maneuver
Gate C-1 is adjacent to the terminal building, with an unoccupied aircraft parked at gate C-3 on the right side. The pushback required a turn into an adjacent alleyway using an "S"-type maneuver. The tug operator was initially required to turn toward the parked aircraft until adequate clearance from the terminal building was achieved, then turn in the opposite direction nearly 180 degrees to align the aircraft in the alleyway.
During the initial turn toward the parked aircraft, the wing walker reported that the tug operator turned tightly. The wing walker also noted that they had to reduce tug speed to avoid baggage carts near the right engine. While focusing on clearing the engine from the carts, the wing walker looked back and saw the right wing tip approaching the left horizontal stabilizer of the parked aircraft. The wing walker was unable to alert the tug operator in time to stop the movement. The right winglet of N913WN struck the left horizontal stabilizer and elevator of the parked aircraft.
Personnel and Procedures
The pushback tug operator had been hired the previous year and was qualified to operate the tug. During an interview with the National Transportation Safety Board (NTSB) investigator in charge, the operator stated he had performed numerous similar pushbacks. The wing walker had 18 years of experience with the company and was qualified. The operator's pushback procedures were followed, except that a pre-brief for the pushback was not conducted.
Damage and Equipment Examination
NTSB investigators examined both aircraft. N913WN sustained minor damage to the right winglet. The parked aircraft, N776WN, sustained damage to its horizontal stabilizer and elevator. The pushback tug was examined by the operator and NTSB investigators and found to be fully functional with no anomalies.