DCA06MA009

NTSB accident investigation · Boeing 737-700 · Chicago, IL · December 9, 2005

Accident · FatalClass 1 · MajorFinal report
Date
December 8, 2005, 19:15 local (Dec 9, 2005, 01:15 UTC)
Place
Chicago, IL
Injuries
1 fatal, 1 serious, 21 minor, 85 uninjured; on the ground: 1 fatal, 1 serious, 3 minor
Damage
Substantial damage
Phase of flight
Landing
Aircraft
N471WNBoeing 737-700
Weather
Instrument (IMC) · Night
Status
Completed · report November 29, 2007
Report
Board-adopted at Board Meeting
Investigation class
Class 1
NTSB office
Major Investigations Division
Parties
ASF-100, Federal Aviation Administration
Safety recommendations
Yes
FAA report
20051208031549A
Case key
62926

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

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Probable cause

The pilots' failure to use available reverse thrust in a timely manner to safely slow or stop the airplane after landing, which resulted in a runway overrun. This failure occurred because the pilots' first experience and lack of familiarity with the airplane's autobrake system distracted them from thrust reverser usage during the challenging landing.

Contributing to the accident were Southwest Airline's 1) failure to provide its pilots with clear and consistent guidance and training regarding company policies and procedures related to arrival landing distance calculations; 2) programming and design of its onboard performance computer, which did not present inherent assumptions in the program critical to pilot decision making; 3) plan to implement new autobrake procedures without a familiarization period; and 4) failure to include a margin of safety in the arrival assessment to account for operational uncertainties. Also contributing to the accident was the pilots' failure to divert to another airport given reports that included poor braking action and a tailwind component greater than 5 knots. Contributing to the severity of the accident was the absence of an engineering materials arresting system, which was needed because of the limited runway safety area beyond the departure end of runway 31C.

Sequence of events

NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.

OverrunLanding - roll
Thrust reverser - inadequateCause
Procedures/directives - not followedFlightcrewCause
Lack of familiarity with aircraftFlightcrewCause
Procedure inadequateFactor
Condition(s)/step(s) insufficiently definedCompany/operator managementFactor
On ground/water collision with objectLanding - roll
Object - fence
Object - vehicle

Analysis

The Safety Board's full report is available at http://www.ntsb.gov/publictn/publictn.htm. The Aircraft Accident Brief number is NTSB/AAR-07/06.

On December 8, 2005, about 1914 central standard time, Southwest Airlines (SWA) flight 1248, a Boeing 737-7H4, N471WN, ran off the departure end of runway 31 center (31C) after landing at Chicago Midway Airport (MDW), Chicago, Illinois. The airplane rolled through a blast fence, and airport perimeter fence, and onto an adjacent roadway, where it struck an automobile before coming to a stop. A child in the automobile was killed, one automobile occupant received serious injuries, and three other automobile occupants received minor injuries. Eighteen of the 103 airplane occupants (88 passengers, 3 flight attendants, and 2 pilots) received minor injuries, and the airplane was substantially damaged. The airplane was being operated under the provisions of 14 Code of Federal Regulations (CFR) Part 121 and had departed from Baltimore/Washington International Thurgood Marshall Airport (BWI), Baltimore, Maryland, about 1758 eastern standard time. Instrument meteorological conditions prevailed at the time of the accident flight, which operated on an instrument flight rules flight plan.

Factual narrative

The Safety Board's full report is available at http://www.ntsb.gov/publictn/publictn.htm. The Aircraft Accident Brief number is NTSB/AAR-07/06.

On December 8, 2005, about 1914 central standard time, Southwest Airlines (SWA) flight 1248, a Boeing 737-7H4, N471WN, ran off the departure end of runway 31 center (31C) after landing at Chicago Midway Airport (MDW), Chicago, Illinois. The airplane rolled through a blast fence, and airport perimeter fence, and onto an adjacent roadway, where it struck an automobile before coming to a stop. A child in the automobile was killed, one automobile occupant received serious injuries, and three other automobile occupants received minor injuries. Eighteen of the 103 airplane occupants (88 passengers, 3 flight attendants, and 2 pilots) received minor injuries, and the airplane was substantially damaged. The airplane was being operated under the provisions of 14 Code of Federal Regulations (CFR) Part 121 and had departed from Baltimore/Washington International Thurgood Marshall Airport (BWI), Baltimore, Maryland, about 1758 eastern standard time. Instrument meteorological conditions prevailed at the time of the accident flight, which operated on an instrument flight rules flight plan.

According to the CVR transcript, when the pilots contacted the MDW Air Traffic control Tower (ATCT) at 1909:53.7, controllers advised them to "continue for [runway] 31C the winds zero nine zero at nine, brakin' action reported good for the first half, poor for the second half." About 1912:28, the first officer received a landing clearance from the ATCT. Flight data recorder (FDR) data indicated that the airplane was aligned on the runway centerline as it touched down at an airspeed of about 124 knots. The speed brakes deployed and the brake pressure increased within about 1 second. Both pilots described the touchdown as "firm." The captain stated that he tried to deploy the thrust reversers immediately after touchdown but had difficulty moving the thrust reverser levers to the reverse thrust position. He further stated that he felt the antiskid system cycle after the airplane touched down but then felt it stop cycling and that the airplane seemed to accelerate. He said that he subsequently applied the wheel brakes manually but made no further effort to activate the thrust reversers. He told investigators that he believed that the use of the autobrake system distracted his attention from the thrust reversers after his initial attempt to deploy them.

The first officer said that, when he sensed a decrease in the airplane's deceleration during the landing sequence, he exclaimed, "brakes, brakes, brakes," and manually applied the brakes. He stated that he then looked at the throttle console and saw that the thrust reverse levers were still in the stowed position. The first officer moved the captain's hand away from the thrust reverser levers and, about 15 seconds after touchdown, initiated deployment of the thrust reversers to the maximum reverse setting. FDR evidence confirmed the systems functions described by the pilots and indicated that full thrust reverser deployment occurred about 18 seconds after touchdown.

The first officer stated that, after the airplane came to a rest, he performed the emergency evacuation checklist while the captain checked on the passengers in the cabin. The passengers evacuated through the forward left and the right rear cabin doors.

Aircraft

Registration
N471WN
Reported as
Boeing 737-700
Category
Airplane
Serial number
32471
Airframe hours
5,273
Engines
CFM International 56-7B24, 24,000 lbs thrust, turbo fanCFM International 56-7B24, 24,000 lbs thrust, turbo fan
Damage
Substantial damage
Flight
Part 121
Registered owner
Southwest Airlines Co
Airworthiness certificate
Standard, Transport
Last inspection
Continuous airworthiness · November 1, 2006 · 168 hours before
Departed
BWI · Baltimore, MD
Destination
MDW · Chicago, IL
Flight plan
IFR
Airport
MDW · Midway Airport, runway 31C, 6,522 × 150 ft, concrete

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
59
Injuries
None
Certificate
Airline transport
Airplane ratings
Multi-engine land
Instrument ratings
Airplane
Medical
Class 1, With waivers/limitations
Last flight review
July 1, 2007
Seat
Left
Flight hours
8,500 total · 6,000 in this make and model · 243 in the last 90 days · 83 in the last 30 days · 2 in the last 24 hours

Weather

Conditions
Instrument (IMC) · Night
Wind
110° at 7 knots
Temperature
25 °F, dew point 23 °F
Altimeter
30.05 inHg
Observed at
MDW, 1 nm away

Docket · 76

The files NTSB released with the investigation on June 20, 2006, on NTSB’s docket system: statements, records, photos and specialists’ reports. 109 MB in all.

Order of Hearing: 1AItem 1 · .PDF · 68 KBNotice of Designation of Chairman of Board of Inquiry: 1BItem 2 · .PDF · 89 KBDesignation of Hearing Officer: 1CItem 3 · .PDF · 85 KBDesignation of Hearing Officer: 1DItem 4 · .PDF · 74 KBNotice of Hearing: 1EItem 5 · .PDF · 63 KBOperations 2 - Factual Report of Group ChairmanItem 6 · .PDF · 155 KBOperations 2 - Factual Report of Group Chairman - Addenda & Errata #1Item 7 · .PDF · 19 KBOperations 2 - Attachment 1 Interview SummariesItem 8 · .PDF · 669 KBOperations 2 - Attachment 2 - OPC ProceduresItem 9 · .PDF · 929 KBOperations 2 - Attachment 3 - Thrust Reverser OperationItem 10 · .PDF · 161 KBOperations 2 - Attachment 4 - Normal Landing OperationsItem 11 · .PDF · 369 KBOperations 2 - Attachment 5 - Additional Landing ProceduresItem 12 · .PDF · 565 KBOperations 2 - Attachment 6 - Pilot DutiesItem 13 · .PDF · 413 KBOperations 2 - Attachment 7 - Home Study PackageItem 14 · .PDF · 2.5 MBOperations 2 - Attachment 8 - RBF A05116Item 15 · .PDF · 168 KBOperations 2 - Attachment 9 - RBF A05141Item 16 · .PDF · 178 KBOperations 2 - Attachment 10 - RBF A05108Item 17 · .PDF · 118 KBOperations 2 - Attachment 11 - Captain's Handwritten NotesItem 18 · .PDF · 199 KBOperations 2 - Attachment 12 - Captain's Irregularity ReportItem 19 · .PDF · 451 KBOperations 2 - Attachment 13 - First Officer's Handwritten NotesItem 20 · .PDF · 362 KBOperations 2 - Attachment 14 - Flight Crew CommentsItem 21 · .PDF · 188 KBOperations 2 - Attachment 15 - OPC Programming For LandingItem 22 · .PDF · 197 KBOperations 2 - Attachment 16 - Pilot StatementsItem 23 · .PDF · 639 KBOperations 2 - Attachment 17 - Flight ReleasesItem 24 · .PDF · 708 KBOperations 2 - Attachment 18 - FAA Notice 8400.C082Item 25 · .PDF · 54 KBOperations 2 - Attachment 19 - OPC Screen Shot Rwy 31C SelectedItem 26 · .PDF · 18 KBATC 3 - Factual Report of Group ChairmanItem 27 · .PDF · 6.0 MBATC 3 - Attachment 1 FAA Accident PackageItem 28 · .PDF · 5.2 MBATC 3 - Attachment 2 ATC TranscriptItem 29 · .PDF · 501 KBATC 3 - Attachment 3 DATIS TranscriptItem 30 · .PDF · 91 KBMeteorology 5 - Factual Report of Group ChairmanItem 31 · .PDF · 4.0 MBMeteorology 5 - Attachment 1 Flight release and weather documentItem 32 · .PDF · 1.2 MBMeteorology 5 - Attachment 2 NWS Weather Study of Snow EventItem 33 · .PDF · 3.3 MBSurvival Factors 6 - Factual Report of Group ChairmanItem 34 · .PDF · 16.0 MBSurvival Factors 6 Factual Report Addenda/Errata 09-21-06Item 35 · .PDF · 79 KBSurvival Factors 6 - Attachment 3: MDW Friction Test Log, Snow Log, Airfield Temperature Logs, and Airfield Condition ReportsItem 36 · .PDF · 11.5 MBPowerplants 8 - Factual Report of Group ChairmanItem 37 · .PDF · 1.5 MBPowerplants 8 - Attachment 1 - EEC DataItem 38 · .PDF · 1.8 MBSystems 9 - Factual Report of Group ChairmanItem 39 · .PDF · 1.2 MBSystems 9 - Attachment 1 - Flap/Slat Electronic Unit Faults Recorded During Final Flight LegItem 40 · .PDF · 21 KBSystems 9 - Attachment 2 - Test Procedure And Results From Test N483WNItem 41 · .PDF · 258 KBSystems 9 - Attachment 3 - Revised Reverse Thrust Interlock Position ProcedureItem 42 · .PDF · 99 KBSystems 9 - Attachment 4 - Spreadsheet Of Resultant TRA PositionsItem 43 · .PDF · 17 KBFlight Data Recorder 10 - Factual Report of Group ChairmanItem 44 · .PDF · 3.0 MBFlight Data Recorder 10 - Attachment 1 Flt 1248 Tabular DataItem 45 · .CSV · 583 KBFlight Data Recorder 10 - Attachment 2 UAL Flt 1446 Tabular DataItem 46 · .CSV · 115 KBFlight Data Recorder 10 - Attachment 3 Flt 2920 Tabular DataItem 47 · .CSV · 490 KBFlight Data Recorder 10 - Attachment 4 flt 321 Tabular DataItem 48 · .CSV · 605 KBFlight Data Recorder 10 - Attachment 5 Flt 2947 Tabular DataItem 49 · .CSV · 620 KBStructures 7 - Factual Report of Group ChairmanItem 50 · .PDF · 3.0 MBFlight Data Recorder 10 - Attachment 6 Flt 1830 Tabular DataItem 51 · .CSV · 597 KBCockpit Voice Recorder 12 - Factual Report of Group ChairmanItem 52 · .PDF · 394 KBAircraft Performance 13 - Factual Report of Group ChairmanItem 53 · .PDF · 12.2 MBAircraft Performance 13 - Group StudyItem 54 · .PDF · 5.1 MBAircraft Performance 13 - Study Addendum 1Item 55 · .PDF · 4.1 MBAircraft Performance 13 - Study Addendum 2Item 56 · .PDF · 1.6 MBAircraft Performance 13 - Group Study ErratumItem 57 · .PDF · 15 KBHuman Performance 14 - Factual Report of Group ChairmanItem 58 · .PDF · 116 KBHuman Performance 14 - Attachment 1 SWA FOM/FRM GuidanceItem 59 · .PDF · 991 KBHuman Performance 14 - Attachment 2 SWA Autobrakes Checkairman Training HandoutItem 60 · .PDF · 195 KB
All 76 files on NTSB’s docket

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.