Insights from another industry
Learning from the subtle cause of a terrible airline accident
On 28 December 2014, AirAsia Flight 8501 crashed into the sea, killing all 162 people on board. The painful and subtle lessons from this crash could also benefit rail if we adopt the right approach.
There are many tragic aspects to the fatal crash of AirAsia Flight 8501. The impacts from each individual loss of life will continue to reverberate for many years to come. The fact that there were a total of 162 people who lost their lives increases the scale and scope of those losses.
But perhaps the most gut-wrenching aspect of this particular crash is the history of the signals about the fault that ultimately caused the crash. In the 12 months before the crash, there were multiple opportunities to respond appropriately to signals about the underlying fault. In fact, there were a total of 23 such signals, including four on the fatal flight itself, and the frequency of these signals had been increasing over that year. Despite this, effective corrective action was not taken which ultimately resulted in the plane crash.
The reason for the ineffective handling of the error signal turned out to be quite subtle. The problem wasn’t that these faults were ignored. Each time the fault occurred it was ‘fixed’ by the maintenance engineers (or the pilots, in-flight). The error signal was being responded to. However, because there was no record of the number of times the fault was occurring, no one realised there was a more serious underlying defect that needed to be addressed. Nor was there recognition of the fact that unless the underlying defect was addressed, the fault would keep occurring and possibly get worse. Each instance of the problem was treated as a single, standalone, incident, and the underlying defect and root cause remained unaddressed.
It was only after the crash, during the accident investigation, that investigators were able to ‘drill down and across’ the different times when the error signal occurred, to identify the root cause driving the repeated error signals. This approach enabled them to go from the failure, to the fault, to the defect, to the cause, and ultimately to the root cause.
In this instance, they found small cracks in the solder joint of one of the circuit boards for one rudder component. These caused an intermittent signal from the rudder, and hence the repeated faults and ultimately the fatal accident.
The crash could have been prevented if there had been a system that enabled this more probing data analysis, recognised repeated faults, and used technical terms about defects consistently. This is always important, but especially in a fragmented industry like air travel. Since this investigation, the airline industry has adopted Data Reporting Analysis and Corrective Action Systems (DRACAS) to prevent such problems.
Avoiding these sorts of incidents in rail is also very challenging because of the many different operators in rail. Each has their own functional priorities and terminologies. These provide unintended opportunities for repeated faults to go unnoticed, or for language about faults to be used in different ways. Despite this, many local rail networks already have their own DRACAS. A national DRACAS for Control Command and Signalling (CCS) systems would support, complement, and extend the reach of this valuable approach. In addition to improving safety, pooling local information into a national system could provide financial benefits. For instance, if a defect in equipment from a supplier or manufacturer is reported by multiple purchasers, it could be quicker and cheaper to resolve that issue than if each purchaser was collecting that data on its own.
Information is being developed for rail on CCS DRACAS. In collaboration with industry partners, we would like to acknowledge the contributions of everyone involved. As is so often the case, the combination of our expertise with that of our stakeholders has been essential for the production of a workable new solution.
Find out about the work of the DRACAS Steering Group and documents for the National CCS DRACAS.
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