Information Processing, Human Error and the Learning Process — Page 164, Lesson 263

I want to walk you through the topic of human error in aviation. Let's start with a clear definition. "Error" is a generic term that describes all those occasions in which a series of mental or physical activities do not achieve their intended effect. That's the professional definition — it covers everything from a simple slip of the tongue all the way up to catastrophic failures like the Tenerife runway collision in 1977, the Bhopal methyl isocyanate tragedy in 1984, and the Challenger and Chernobyl catastrophes in 1986. These are the kinds of events that have driven the aviation industry to invest heavily in human error research, and national authorities have all included the study of human error in their Human Performance syllabi. Now, let's talk about how errors are generated. While it is possible to have isolated errors that have neither consequence nor influence on any further elements, errors in general tend to be cumulative. One error leads to a second, which in turn can lead to a third, and so on. This is commonly known as the error chain. A simple example of an isolated error would be pulling out a young plant from a flower bed, mistaking it for a weed — it has no further consequences. A cumulative error would be issuing an incorrect aircraft maintenance procedure, which then results in a series of accidents. Broadly speaking, error generation can be caused by either internal or external factors. Let's look at the internal factors first. Among the internal sources are: mistaken perception, misinterpretation of information, preconceived assumptions, experimentation, faulty memory, fatigue, and lack of practice — which is sometimes known as the 'deterioration effect'. These are all things going on inside the individual that can lead to errors. On the external side, some external sources are: stressors, ergonomics — that is, bad design or layout of instruments — economics, which means company or organisational pressures, and social environment, such as cultural misunderstandings. These are factors in the environment around you that can generate errors. Finally, let's look at how errors are classified. Different types of errors are discussed in their relevant chapters, particularly Chapter 9, but in general, errors can be classified into three main groups. The first group is faults. A fault is when the action satisfies the operator's intent, but the intent itself was incorrect. For example, the execution of a drill was 100% accurate, but it was the incorrect drill for the task or emergency. So you did everything right, but you were doing the wrong thing to begin with.