It was on this day in 2005 that the first hull loss occurred of a Boeing 737-700. Southwest Airlines flight 1248 overran the runway at Chicago Midway Airport.
The aircraft on the 10th of December, only to be moved after the NTSB concluded their onsite investigation. (© Gabriel Widyna)
After a delay of 1 hour and 5 minutes, caused by weather, the Boeing 737-7H4 had departed Baltimore / Washington International Airport. Destination, Chicago Midway Airport just over 600 miles (975 km) in a straight line. The route as the crow flies (©ASN)
After an uneventful flight, the aircraft had to hold for about 30 minutes. ATC advised the crew this was due to snow clearing in progress. After receiving clearance to leave the hold the crew was vectored to the 6522 feet (1980 meters) long runway 31C at Chicago Midway Airport. While in the hold the crew had updated the Performance Computer with the latest weather. This resulted in a tailwind component of 8 knots. (Southwest Airlines tailwind limit was 10 knots, However, a limit of 5 knots applied when the braking action was poor.
Using their Performance Computer to go through different scenarios the crew considered different options for fair and poor braking action. The crew was aware of these limits and realised they would have to divert if the braking action was reported as poor.
During the fligth and the approach briefing the crew decided to use the auto brake system due to the weather conditions. Although neither fligthcrew member had used this system previosuly under these conditions. When contacting Midway Tower ATC the crew received the following information;
Runway 31 C braking action - First half, good - Second half, poor
Wind 090° at 9 knots
Shortly after receiving the landing clearance the aircraft touched down at a speed of 124 knots, on the centerline of the runway. Within one second after touchdown (a frim touch down according to the crew) the spoilers deployed and brake pressure increased. The captain reported in the post accident interview that he had trouble selecting reverse thrust and that he was under the impression the antiskid system had failed and the aircraft was accelerating. The First Officer noticed that the deceleration was decreasing and called for the brakes to be applied, and applied manual braking himself. The Captain still had his hands on the reverse thrust levers, without selecting them. 15 Seocnds after touchdown the first officer removed the captains hand form the recerse thrust levers and selected maximum reverse. 18 seconds aftertouchdown the thrust reverser were fully deployed.
The aircraft being readied for removal from teh accident site (© NTSB)
This was to late to stop the aircraft on the runway and the aircraft ran off the end of the runway, it continued;
Through the runway safety area
Through a blast fence
Through the localiser antenna
Accross an airport road
Through the airport perimeter fence.
Comming to a stop an a public road adjacent to the airport perimeter after striking a car. (one of the occupents of the car, a 6 year old child, sadly perished in the collision while 4 passers by received various injuries)
Chicago Midway Airport layout, runway 31C in yellow and final location of aircraft at red dot (Source and © NTSB Report)
An extensive investigation was launched by NTSB and the investigation report gives the following probable cause, from the NTSB report;
"The National Transportation Safety Board determines that the probable cause of this accident was 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." Several contributing factors are also stated in the NTSB report, which can be found by clicking here.
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