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1、Accidents, Errors and Swiss CheeseOn Saturday, Asiana Airlines flight 214, a Boeing 777, crashed upon landing at San Francisco Airport. Through a combination of luck and robust aircraft design, only 2 people were killed; a surprising outcome given the photos of the wreckage. Unfortunately, many more
2、 were injured, a number in serious or critical condition. Intense speculation surrounds the cause of the crash, with theories ranging from pilot error to inoperative runway guidance systems to mechanical failure. What is known so far is that the plane made an abnormal final approach, striking its ta
3、il against a sea wall that precedes the runway. Whats unclear is why?The NTSB, the government body in charge of the investigation, has numerous experts on scene. Their process is methodical, sometimes taking years to establish a series of root causes and recommendations following a plane crash. In t
4、his case, the NTSB has a number of factors in its favor. The remaining pieces of the plane are immediately observable, unlike crashes that happen at sea. The black boxes have already been recovered. The crash happened in a populated area, with numerous eyewitnesses as well as video. The crew survive
5、d the crash and will be able to provide important information about the final fateful minutes of the flight.When accidents like Asiana 214 happen, people hunger for immediate and simplistic answers. Our need to feel secure fuels a desire for straightforward explanations that bring closure to mysteri
6、es. Our culture of real-time social media rapidly turns people into aviation experts, investigative sleuths and conspiracy theorists. Unfortunately, armchair speculation is rarely accurate, and ultimately the contributing factors of a crash can be diverse and complex.The intense media focus creates
7、a false sense of insecurity, leading many to feel that commercial air travel is risky. In truth, aviation safety efforts have produced remarkable results commercial air travel is an incredibly safe mode of transportation. Prior to Saturday, the last fatal plane crash on US soil of a commercial jet o
8、f at least regional size was back in 2006. The last previous fatal domestic crash involving a larger, “transatlantic” class jet think 737s and larger was in 2001. During that timeframe there have been 10s of millions of safe, uneventful flights. Much of this is due to the disciplined, evidence-based
9、 approach to safety of modern aviation.One of the foundational safety principles of modern aviation is known as the Swiss cheese model. It is a concept that was first described by the cognitive psychologist and researcher James Reason. In his seminal book Human Error, Reason chronicled a number of f
10、amous disasters, including Three Mile Island and the Challenger space shuttle accident. But instead of merely reviewing the underlying factors of each incident, he proposed an integrated theory of accident causation. Reason had several profound insights: Accidents involving complex systems are often
11、 the result of the confluence of multiple contributing factors. Contributing factors can occur in a wide range of domains from unsafe acts such as a pilot approaching a runway at an improper altitude to organizational errors such as a culture of fiscal austerity that does not prioritize training act
12、ivities. As opposed to the active errors that occur at the time of an incident many contributing factors are in fact latent errors. These latent errors lie dormant, waiting for an active error to turn them into a trigger for an incident. Human beings, lacking unlimited concentration, focus and memor
13、y, will always be prone to operational errors. Properly designed systems account for this limitation, expect a level of human error, and ultimately keep these errors from resulting in an actual incident.Reason summarized his integrated theory of accident causation with an excellent visual known as t
14、he Swiss cheese model.Lets consider the model in the context of an investigation into a a crash landing such as Asiana flight 214. As a disclaimer, this example is not intended to represent a factual analysis of this tragic event. It is simply an example of how the Swiss cheese model can be used by
15、investigators to gain a deeper perspective of the root cause of an accident. Instead of merely focusing on the immediate visible possibilities (e.g. pilot error), the Swiss cheese model forces investigators to look at the latent failures lurking deep within the organizational body.In the case of a c
16、rash landing, examples of unsafe acts could include items such as: Incomplete use of mandatory checklists Insufficient intra-crew or crew-to-tower communicationsStepping back a level is a layer of failures known as preconditions for unsafe acts. A classic example in a plane crash would be fatigue, as when pilots on a long flight have had insufficient sleep. The next layer, unsafe supervision could be represented by the following examples
