Wading through the rampant rumors following last week's tragic snowstorm-related Southwest Airlines accident at Chicago's Midway airport, a number of factors, involving thrust reversers or braking action, are starting to be seen as possible causes or causal factors in the investigation. 

Southwest Airlines' Flight 1248 was involved in the accident at Chicago Midway Airport at approximately 7:15 p.m. CST while the aircraft, a Boeing 737-700, was landing. The aircraft veered off the runway onto Central and 55th Avenue, beyond the northwest corner of the runway. Flight 1248 was scheduled for a 2:55 p.m. CST departure out of Baltimore/Washington International Airport, but the aircraft's departure was delayed until 4:50 p.m. CST because of weather. The flight arrived at Chicago Midway at 7:15 p.m., after circling the Chicago Midway Airport for approximately 35 minutes.

Weather reports indicate that the aircraft was dealing with as low as a 200 foot ceiling and visibility estimated at anywhere from 1/4 to 3/4 mile. The passenger list indicated the aircraft carried 98 passengers with a crew of five.

The aircraft involved was a Boeing 737-700, N471WN (although official SWA statements originally named it as 'tail number N-471'). Southwest took delivery of this new aircraft in July 2004. The 737-700 has the same fuselage as the 737-300 and is fitted with a new generation of wings, stabilizers, and tail sections. The 737-700 is 110 ft 4 in long and can carry up to 148 passengers in an all-economy configuration. The aircraft was released from the airline's Phoenix maintenance facility on Dec. 7, 2005. There were no indications that the aircraft was experiencing any type of maintenance problems.

The Southwest Airlines Captain on Flight 1248 has been flying for the airline for ten years. The Southwest Airlines First Officer on Flight 1248 has been flying for the airline for more than two years.

NTSB sources, quoted in the general media, are starting to talk about a lack of deceleration after touchdown on Midway's 6500 foot runway that indicates a number of possibilities... or a combination thereof. Among items in question are how much of the runway was used in the initial touchdown, when the Boeing's two thrust reversers were actuated, when they actually deployed and what effect braking action played in the matter. Initial concerns about excessive approach and touchdown speeds (the culprit in SWA's one other serious accident in Burbank, CA) appear to have been down-played by NTSB personnel since the pilots were interviewed on Saturday and as the CVR and FDRs were examined in Washington.

Robert Benzon, National Transportation Safety Board investigator in charge, said that, "They all said it was a smooth landing but they could sense a lack of deceleration."

Media reports suggest that both pilots have indicted that the aircraft did not immediately respond to a command to actuate thrust reversers as the aircraft attempted to decelerate on airport that had seen 7-9 inches of snow that day.

Keith Holloway, a spokesman for the National Transportation Safety Board, added that, "The captain told us when he initially tried the thrust reversers, he couldn't do it." 

Southwest CEO, Gary Kelly, has also confirmed that the flight crew selected to deactivate the auto-braking system in order to give them more direct control over the situation... a move defended by Kelly in statements to the media, "We let our flight crews make the determination to brake the aircraft. It's just a choice, and we think that it's been obviously very, very successful over a long period of time."

Boeing corroborated the fact that auto-braking selection is a choice left to flight crews and that Boeing does not mandate its use for such operations... nor do they see anything unusual in leaving such a decision to the cockpit crew. Boeing spokesperson Liz Verdier explained that, "There is not a right or a wrong way to do that... They are used or not used in accordance with conditions or airline operational procedures."

One associated news item that is making the rounds, concerns older airports and short runways, and is no secret to the world of aviation as regards some of the elder airports that make up the nation's air transport network. Midway was built in 1923 and quickly surrounded by houses and businesses that were unrestricted in building up around and close to the airport. It is one of some 300 US commercial airports without 1,000-foot buffer zones bordering their runways. The end of the runway used by SWA 1248 was reportedly only 280 feet from the perimeter fencing of the airport.

A number of programs have been developed to try and mitigate some of these issues, including one that has proven to be quite successful and cost-effective. The use of beds of 'crushable concrete' slow aircraft as the progress off a runway and toward the perimeter... the effect is quite striking in that is not only decelerates the aircraft aggressively but does so in a fashion that minimizes the possibility of passenger injury and, to an extent, aircraft damage. This program, known as Engineered Material Arresting Systems, are currently in use at 18 runways at 14 airports, where they have already been employed to arrest accidental overruns on three occasions since their first use in May 1999 at NYC's Kennedy Airport.

FMI: www.southwest.com. www.nts.gov, www.faa.gov/news/news_story.cfm?type=fact_sheet&year=2005&date=090205