History of Flight
On March 1, 2008, at 1012 central standard time, Southwest Airlines Flight 411, a Boeing B-737-7H4 (N741SA), and Southwest Airlines Flight 15, a Boeing 737-3H4 (N652SW), collided during ground operations at Dallas Love Field (DAL), Dallas, Texas. Flight 411 had landed on runway 13 left and was cleared to taxi to gate 2. While taxiing southbound on taxiway D past Flight 15 at gate 11, the left winglet of Flight 411 collided with the left horizontal stabilizer of Flight 15. Flight 411 stopped immediately on taxiway D and shut down both engines.
Flight 15 had completed a pushback from gate 11, and the ground crew had disconnected and left the area. Flight 15 was stationary with the parking brake set, waiting for Flight 411 to pass before taxiing for takeoff. The aircraft was on an approximate heading of 060 degrees, with the left horizontal stabilizer positioned about 20 feet from the east edge marking of taxiway D.
The captain of Flight 411 later stated that it appeared they could safely pass Flight 15. The first officer asked about wing clearance, and the captain looked over his left shoulder and said they had enough room.
After initial photographs, Flight 411 was towed to gate 2, and Flight 15 was towed to gate 11. Passengers and crew deplaned normally.
Personnel Information
Flight 411 Captain: 57-year-old airline transport pilot with 23,000 total flight hours, including 18,000 as PIC and 9,000 on the B737. He held a first-class medical certificate dated October 23, 2007, with the limitation "must have available glasses for near vision."
Flight 411 First Officer: 50-year-old airline transport pilot with 8,090 total hours, 2,610 as PIC, 4,920 on the B737. Medical certificate dated April 12, 2007, with limitation "must wear corrective lenses."
Flight 15 Captain: 52-year-old airline transport pilot with 16,250 total hours, 10,900 as PIC, 10,980 on the B737. Medical certificate dated January 17, 2008.
Flight 15 First Officer: 48-year-old airline transport pilot with 6,800 total hours, 2,150 as PIC, 4,200 on the B737. Medical certificate dated September 17, 2007.
Aircraft Information
- Flight 411 (N741SA): Boeing 737-7H4, serial number 29277, manufactured 1998. Wingspan 117 ft 5 in; winglet top height 21 ft 4 in; horizontal stabilizer width 47 ft 2 in.
- Flight 15 (N652SW): Boeing 737-3H4, serial number 27722, manufactured 1997. Wingspan 102 ft 5 in; winglet top height 17 ft 9 in; horizontal stabilizer width 41 ft 8 in and height 17 ft.
Meteorological Information
At 0953 central standard time, DAL reported wind 140 degrees at 6 knots, visibility 3 statute miles in haze, overcast clouds at 500 feet, temperature 59°F, dew point 57°F, barometric pressure 30.27 inHg.
Communications and Dispatch
Flight 411 was cleared to taxi to gate 2. Flight 15 called for pushback from gate 11 and was cleared to taxi to runway 13 left with the instruction to "use caution for company behind you."
Flight Recorders
Both aircraft had cockpit voice recorders (CVRs) and digital flight data recorders (DFDRs). Recordings were of excellent quality; no CVR group was formed or transcript prepared. DFDR data for Flight 411 showed the right engine shut down 150 seconds after touchdown, maximum taxi groundspeed 25 knots, impact groundspeed 7 knots on magnetic heading 180 degrees. Perturbations recorded: vertical +1.05G, longitudinal -0.42G, lateral ±0.05G, with braking at 10:13:42. For Flight 15, DFDR showed engines at idle, parking brake set, heading 60 degrees, with perturbations vertical +1.04G, longitudinal -0.05G, lateral -0.18G at 10:12:33.
Wreckage and Impact
Flight 411's left winglet suffered minor damage with a portion separating after striking Flight 15's horizontal stabilizer. Flight 15 had minor damage to the leading edge of the left horizontal stabilizer, with part of the separated winglet embedded. A smear on the underside skin measured at a 56-degree angle from the leading edge.
Additional Information
Southwest Airlines Flight Operations Manual Bulletin 24-05 (November 10, 2005) provided guidance for 737 models, stating that when the aircraft is not on a taxi line, a lateral clearance of 10 feet is considered minimum acceptable separation. It cautioned that lateral clearance, especially to the top of the winglet, is difficult to judge and advised stopping if clearance is in question. SWA Training Topics 2006-01 and 1-07 warned that winglets on the -700 extend beyond what is visible to the pilot and that from the cockpit, the winglet appears at the position light edge but is actually 42 inches further outboard.
Corrective Actions
Southwest Airlines issued memoranda A-08-19 and A-08-30 in March 2008, instructing pilots to use vigilance when taxiing, to stop and request a wing-walker if unsure, and to review training. The City of Dallas repainted markings at DAL, and a Letter of Agreement was signed requiring pushback approval from the tower for certain gates. The Dallas ATCT changed procedures to not allow taxi on taxiway D simultaneously with pushback from affected gates. The separated winglet portion was mounted at the Southwest training center as a visual reminder.
Probable Cause
Not stated in the source.