(Editor's Note: The following is the
unedited text of the updated factual report issued by the National
Transportation Safety Board Thursday, regarding the December 8
accident at Chicago's Midway Airport involving Southwest
NTSB UPDATE ON
SOUTHWEST AIRLINES RUNWAY OVERRUN AT MIDWAY AIRPORT
The National Transportation Safety Board today released the
following update on its investigation into the accident involving
Southwest Airlines flight 1248, a Boeing 737-700 on December 8,
2005, at Midway Airport in Chicago, Illinois. The airplane overran
runway 31C during the landing rollout.
The accident occurred about 7:14 pm central standard time. The
airplane departed the end of the runway, rolled through a blast
fence, a perimeter fence, and onto a roadway. The airplane came to
a stop after impacting two automobiles. One automobile occupant was
fatally injured and another seriously injured. The flight was
conducted under 14 CFR Part 121 and had departed from the
Baltimore/Washington International Thurgood Marshall Airport,
The on-scene portion of the investigation has been completed.
Additional fact-finding, including tests and research, will be
conducted at various component manufacturers. The Safety Board
staff continues to examine the information provided by the flight
data recorder and the cockpit voice recorder.
The two pilots in the cockpit were interviewed on Saturday. Each
interview took approximately three hours.
The pilots stated that everything was normal through the point
of touchdown. Approaching the airport, weather was of concern to
them, and they listened to the ATIS (the recorded weather update)
four times during the latter portion of the flight. They stated
that they agreed with the dispatcher's assessment of the conditions
for landing on runway 31C and backed up that assessment by
inputting the numbers into the on-board laptop computer tool.
The computer confirmed that the landing would be within the
operational parameters of the airplane and Southwest's procedures,
they said. Autobrakes were set on MAX, and they activated after a
"firm" touchdown. The flying pilot (Captain) stated that he could
not get the reverse thrust levers out of the stowed position. The
first officer, after several seconds, noticed that the thrust
reversers were not deployed and activated the reversers without a
problem. At some point, the Captain noticed that the airplane was
not decelerating normally and applied maximum braking manually. The
first officer also became aware of the poor braking effectiveness,
moved his seat farther forward, and also applied maximum braking.
They stated that they continued to apply maximum pressure to the
brakes as the airplane went straight off the end of the runway and
came to a stop.
Interviews were conducted with a number of other Southwest
Airlines flight crews, including the crew of the last Southwest
flight to land at Midway and a subsequent crew that diverted to St.
Preliminary calculations show that the airplane touched down
with about 4,500 feet of remaining runway and was on the runway for
about 29 seconds. Preliminary calculations also show that, for the
runway conditions and use of brakes and thrust reverser that
occurred, the stopping distance without hitting obstructions would
have been about 5,300 feet (the actual stopping distance was about
5,000 feet). In addition, had the airplane landing into the wind,
rather than with a tail wind, the stopping distance fro a landing
would have been about 1,000 feet less.
Documentation of aircraft performance from the scene has been
completed to the maximum extent possible. It was not possible to
observe tire marks from much of the landing rollout due to the fact
that the aircraft landed on a snow-covered runway and snow fell on
the runway immediately following the accident.
FDR data show that autobrakes were active and provided high
brake pressure upon touchdown. Autobrakes and manual braking
continued to provide high brake pressure throughout the landing
FDR data show that thrust reversers were activated about 18
seconds after touchdown or about 14 seconds before contact with the
blast fence. Testing and examination of the thrust reverser systems
Investigators have obtained the laptop computer tool used by the
accident flight crew. It will be examined and calculations of
landing performance will be compared to flight manual data.
Eleven security-type video cameras were identified on the
airport that may show imagery of the airplane rollout or the
surface of the runway and taxiway at the time of the accident. The
videos will be reviewed.
National Weather Service forecasters and other personnel were
interviewed. An enhanced snow band was in the area producing
localized heavy snow due to lake enhancement. This apparently is a
somewhat unusual weather phenomenon, as the band swath was only 20
to 30 miles wide with snow accumulations of 10 inches right over
Midway Airport weather observation equipment and records were
examined and all equipment was working normally during the evening
of the accident.
Southwest Airlines dispatchers who were associated with the
accident flight were interviewed. Prior to the takeoff from
Baltimore, when weather conditions deteriorated and the runway
switched to runway 31C, the dispatcher determined that runway 31C
was approved for landing for flight 1248. Runway conditions,
braking action, wind speed and direction, airplane weight and
mechanical condition of the aircraft are typical factors considered
in making such decisions. The flight was contacted twice on the way
to Midway and the appropriateness of using the runway for landing
was reaffirmed during both contacts.
Official weather observations:
Approximately 20 minutes prior to the accident, the winds were
from 100 degrees at 11 knots, visibility was less than a mile in
moderate snow and freezing fog, the ceiling was broken at 400 feet,
and overcast at 1400 feet, temperature -3C, dew point -5C,
altimeter setting 30.06 in. Hg. Remarks -runway 31C rvr (runway
visual range) 4500 feet, snow increment - 1 inch of new show in the
last hour, 10 inches on the ground.
Approximately 23 minutes after the accident, a special
observation revealed winds out of 160 degrees at 5 knots,
visibility � mile in heavy snow, freezing fog, sky obscured
with a vertical visibility of 200 feet, temperature -4C, dewpoint
-5C. Remarks - runway 31C, rvr 3000 feet.
Blood and urine samples were obtained from both pilots. The
disposition of the blood samples is being reviewed.
The aircraft has been removed from the accident site and was
transferred to a hangar at Midway Airport. The maintenance log
revealed no writeups or deferred items for the accident flight or
several previous flights.
Professional surveyors completed a survey of the accident scene
and the geography leading up to the site to include the locations
of parts shed by the aircraft after it left the paved runway
surface and the blast fence destroyed during the accident
Both engines were visually examined at the accident site.
Although the first stage compressor blades of both engines showed
foreign object damage, they were all intact and present. Wood from
the blast fence and other debris was present in both engines.
A visual examination of the turbine sections revealed no missing
The 60-day engine history revealed no deferrals or writeups.
Each engine has two thrust reverser sleeves. FDR data indicated
that all four sleeves were deployed until after the airplane left
the paved runway overrun surface. Hydraulic system B (that runs the
thrust reversers) revealed no leaks.
The Systems Group documented the switches, circuit breakers and
controls in the cockpit. The leading edge slat, flap, and trailing
edge flap extension measurements were taken and revealed
symmetrical extension of all devices. The measurements will be
compared to Boeing documentation to determine exact extension.
Chicago Fire Department personnel were interviewed to determine
if any switch positions or other items were altered during the
rescue effort. The Fire Department Chief stated that the only
things his people did were to disconnect the battery and turn off
the crew oxygen source.
The brakes were found in good condition with adequate wear
remaining. The main landing gear tires had acceptable tread depth
and no indication of flat spots.
Air Traffic Control
The local controller, two tower controllers, and the tower
supervisor were interviewed. All controllers stated that they saw
the aircraft lights during the landing roll, but did not see the
The investigation has
revealed that runway 31C was used as the landing runway because it
contained lower landing minimums for aircraft using the ILS
approach. If runway 13C was used, the runway most aligned with the
wind, pilots would have been unable to land because of insufficient
All flight attendants were interviewed. They all said that they
noted a smooth landing but that the deceleration feeling thereafter
seem less than usual. They noted that the emergency lighting came
on after the airplane came to rest, and one flight attendant opened
the L1 door to begin the evacuation. The emergency slide deployed
automatically, but its angle in relation to the ground was less
than ideal. This caused passengers to begin to pile up around the
bottom of the slide. Rescue personnel assisted people away from the
slide. The first officer deplaned after about 5 passengers and also
assisted in getting people away from the airplane.
Further factual updates will be issued when appropriate.