Narrative:Southwest Airlines flight 31, a Boeing 737-300, N649SW, exited the taxiway while taxing to the gate and came to rest in a ditch at the Nashville International Airport, Tennessee, USA. Nine of the 138 passengers and crew onboard received minor injuries during the evacuation and the airplane was substantially damaged.
The airplane landed normally on runway 20R and exited at taxiway B2. ATC instructed the flight to taxi to the ramp (gate C20) via taxiway B, T3, and T4.
The captain reported he used landing lights to assist in the taxi along B and T3 and then extinguished the landing lights as the airplane crossed runway 13/31, but left the taxi lights on.
The flight crew reported that they had difficulty locating taxiway T4 as it appeared dark and there was glare from the terminal lights ahead. About 15 seconds prior to the excursion the airplane began a left turn briefly to a heading of about 065 degrees. Taxiway T4 was oriented about 045 degrees. The crew was searching for the turn to the ramp when the airplane then turned back to the right to a heading of 090 degrees, consistent with the heading toward gate C20. Three seconds later the airplane exited the taxiway into a grassy area with a large drainage ditch, east of the intersection of taxiways T4 and J. The nosegear collapsed, and the airplane came to rest angled to the right, on the left nacelle, right wing tip, and nose.
Shortly after the airplane came to rest an audible alarm began sounding in the cockpit which the flight crew indicated they could not silence. The pilot advised ATC that "we've cut the corner here and are off in the grass" and asked for ARFF equipment.
When the airplane stopped all the cabin lights went out for some time before the emergency lights came on. The flight attendants stated that they did not know what was going on so began yelling, "heads down, stay down" as they tried to call the pilots but there was no power on the interphones. The FAs initiated the evacuation a short time later. About one minute after the airplane came to rest, the pilots noticed that the slides were deploying and passengers were evacuating and the captain announced on the public address system "okay don't evacuate flight attendants, do not evacuate" to which the first officer responded "oh they are already going."
Review of Air Traffic records and interviews with controllers revealed that about 30 minutes prior to the accident the taxiway lights for "TWY J & Apron 2" were selected "off." This resulted in shutting off the lights for taxiways L and J; taxiways T4 and T5 to the northeast of L; the lights along the edge of the ramp parallel to J; and the connector and circular area between Concourses B and C.
Probable Cause:PROBABLE CAUSE: "The flight crew's early turn towards the assigned gate because taxiway lighting had been inadvertently turned off by the controller-in-charge which resulted in the airplane leaving the paved surface.
Contributing to the accident was the operation of the screen-saver function on the lighting control panel that prevented the tower controllers from having an immediate visual reference to the status of the airfield lighting."
METAR Weather report:
22:53 UTC / 16:53 local time: KBNA 152253Z 18003KT 10SM CLR 17/07 A2989 RMK AO2 SLP121 T01670072
23:53 UTC / 17:53 local time: KBNA 152353Z 00000KT 10SM CLR 14/07 A2989 RMK AO2 SLP122 T01440067 10200 20144 50002
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not
display the exact flight path.
Distance from Houston-William P. Hobby Airport, TX to Nashville International Airport, TN as the crow flies is 1071 km (669 miles).