Increasing Learning from Accidents A Systems Approach illustrated by the UPS Flight 1354 CFIT Accident
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Most accident analyses are primarily based on advert hoc approaches. Many formal evaluation strategies have been proposed, however few are broadly used. This case examine reveals how a structured course of referred to as CAST (Causal Evaluation primarily based on Methods Idea), primarily based on a extra highly effective mannequin of accident causation, can enhance the outcomes of accident investigation. The case examine used is a CFIT (managed flight into terrain) accident
involving a UPS A300-600 plane whereas touchdown on the Birmingham-Shuttlesworth Worldwide Airport on August 14, 2013. The outcomes are in contrast with the official NTSB accident report. The NTSB course of is often thought-about the “gold normal” in accident investigations, and certainly, they do a wonderful job. Subsequently, a comparability of the outcomes is informative about how accident investigation and evaluation is likely to be improved past the usual method utilized by the NTSB and most others.
The structured evaluation technique used, referred to as CAST (Causal Evaluation primarily based on System Idea), is primarily based on an expanded accident mannequin referred to as STAMP (Methods-Theoretic Accident Mannequin and Processes) [Leveson, 2012]. Historically, accidents have been considered ensuing from a sequence of failure occasions, every occasion immediately associated to the occasion that precedes it within the chain. For instance, the bags door is not fully closed, the plane climbs to a degree the place unequal strain between the cargo
compartment and the passenger cabin causes the cabin flooring to break down, the cables to the management surfaces (which run by way of the ground) are severed, the pilots can not management the plane, and the aircraft crashes. The largest downside with such a chain-of-events mannequin is what it omits. For instance, why did the design of the bags door closure mechanism made it troublesome to find out whether or not it was successfully sealed? Why did the pilots not detect that the door was not shut accurately? Why did the engineers create a design with a single level failure mode by operating all of the cables by way of the cabin flooring? Why did the FAA certification course of permit such designs for use? And so forth. Whereas these
extra components will be included in accident investigation and evaluation, there isn’t a structured course of for ensuring that “systemic” causal components are usually not missed.
STAMP extends the normal mannequin of accident causation to incorporate the chain-of-events mannequin as one subcase however consists of the causes of accidents that don’t match inside this mannequin, notably those who happen within the advanced sociotechnical programs widespread at the moment. These causes (along with part failure) embody system design errors, unintended and unplanned interactions amongst system parts (none of which can have failed), flawed security tradition and human choice making, insufficient controls and oversight, and flawed organizational design. In STAMP, accidents are handled as extra advanced processes than easy chains of failure occasions. The main focus shouldn’t be merely on the occasions that led to the accident, however why these occasions occurred.
