Accident Review: Southwest Airlines 1248 Runway Surface Condition Reporting
In my day job, I've been working on Australian standards for implementing the Global Reporting Format (GRF). Unfortunately, as with many advances in aviation, this was a change brought about by an accident. While it was likely that there were many influential accidents and incidents, I want to analyse the critical inciting event in this post.
Southwest Airlines Flight (SWA) 1248 was miraculous in that everyone on the aircraft survived. But it was also tragic with the death of a child not even at the airport. And it triggered a lot of action by the Federal Aviation Administration (FAA), the International Civil Aviation Organisation, and many other civil aviation authorities.
On a Snowy Night in December
On December 8, 2005, Southwest Airlines Flight 1248, a Boeing 737-700, was preparing to land at Chicago Midway International Airport during a snowstorm. It had held in the area while the airport operator completed snow-clearing operations on the operational runway. From a wind direction perspective, Runway 13C was the preferred runway. Still, the visibility at the time meant that its reciprocal, Runway 31C, was the only option. As such, the crew had to contend with a tailwind on landing.
With snow clearing reported as complete, the flight was vectored for Runway 31C and touched down a little after 1900 hours (local). From reading the investigation report, the initial touchdown went as expected, but it quickly became apparent that the aircraft was not decelerating as expected. Simultaneous issues with reverse thrust and auto-braking delayed the full application of these systems as the aircraft ran off the other end of the runway.
The aircraft continued through the runway safety area (RSA, similar to but not the same as a runway end safety area (RESA)), a blast fence, the ILS antenna, across a perimeter road, through the airport perimeter fence and onto a public road. On the road, it struck three vehicles, killing one of their occupants, a six-year-old, and injuring another four. Eighteen passengers on the aircraft were also injured.
The Investigation
The National Transport Safety Board (NTSB) investigated the accident and issued its report two years later. Among the analysis and findings, the investigators focused on the system surrounding runway surface conditions. This assessment comes with over 15 years of post hoc rationalisation, but please indulge me.
Knowing what became of their findings, the seemingly insignificant findings 18 & 21 hold the key. They say:
Finding 18: "Guidance on braking action and contaminant type and depth reports would assist pilots, air traffic control, operator dispatch, and airport operations personnel in minimising the subjectivity and standardisation shortcomings of such reports."
Finding 22: "Establishment of a means of correlating the airplane's braking ability with the runway surface condition would provide a more accurate assessment of the airplane's basic landing performance capability."
The relationship between what the airport operator sees on the runway (contaminant type, depth, coverage, etc.) and the aircraft's performance during the landing (or take-off) manoeuvre became the crux of the GRF initiative. With this foundation, relevant findings on runway surface condition reporting and decision-making make more sense. These findings include:
The need for ATC to provide all the relevant information
The recognition that conditions change during flight and that pre-arrival assessments may also be required
The provision of performance calculation systems that include appropriate safety margins and present calculation assumptions to the crew
The importance of Crew training on interpretation of runway surface condition reports
The investigation summarises all these points in finding number 22. It calls for developing a new approach to runway surface condition assessment and reporting system.
The Aftermath
The FAA established the Take-off/Landing Performance Assessment (TALPA) Aviation Rulemaking Committee (ARC) within months.
Globally, the early work of the TALPA ARC was adopted by ICAO, with several of its panels and working groups bringing together the expertise required to revamp this system. The group at the forefront of this work was the ICAO Friction Task Force. Its project became known as the enhanced global reporting format for assessing and reporting runway surface conditions (or GRF for short). Groups like this are made up of volunteers from around the world that typically do this work in addition to their day job. They are supported by employees of ICAO.
In record time, according to ICAO timelines, a comprehensive suite of changes was proposed in 2015. And by comprehensive, I mean amendments to five Annexes, three PANS documents and two guidance documents. Rarely are such broad changes proposed.
More to Come…
I will save further discussion on the GRF for tomorrow's post. For now, let me leave you with a little teaser.
Why is it taking so long?
In short, the GRF established by ICAO is based on a world where every airport has air traffic control, staff on site 24/7 and a seasonal set of conditions that compromise runway surface conditions in a reasonably predictable way. This set of conditions applies to a vast minority of Australian airports. But we want to take advantage of the safety improvements that come with the GRF. We need to find a set of parameters that address the risk posed by contaminated runways within the operational context of our certified aerodromes.
See you tomorrow.
