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ResponseTimes
Response or reaction time is the time interval between the onset of a given signal and the production of a response to that signal.
In the simplest case, such as pushing a button when a light illuminates, the reaction time is about 0.2 seconds. If we complicate the task by having two lights and two buttons the reaction time will increase, the increase being due to the increase in loading on the central decision maker. In aviation the reaction times will be even longer since the decision element of the task is likely to be more complex.
In an incident at Manchester a bang was heard before V1 (Decision Speed) and the brakes were applied within one second. In a case at Sumburgh airport when the aircraft ran off the end of the runway it took 5 seconds after the perceived emergency before the brakes were applied. Why the difference?
At Manchester the stimulus occurred before V1. Hours of training in simulators have stressed that with any emergency before V1 the aircraft should be halted and the emergency dealt with. It becomes a reflex action to stop the aircraft on the ground for any emergency before V1.
In the Sumburgh case the emergency occurred after V1. Training stresses that for any emergency after V1, the take-off run should be continued and the problem dealt with in the air. In this incident however, the emergency was that the aircraft could not get airborne (due to the elevator locks becoming engaged). The central decision maker took some time to override the ingrained desire to get the aircraft off the ground.
Reaction times are important but in general:
It is of paramount importance to make the correct response rather than a fast response.
Human Reliability, Errors and Their Generation
“It is in the nature of man to err” - Cicero.
Human Reliability
Human reliability can be defined as an individual functioning in the manner in which he/she is supposed to function. Studies of human error rates during the performance of a simple and repetitive task can normally be expected to occur about once in 100 times. This error rate is built into the human system and can increase rapidly when stress, fatigue or low morale is an added factor. It has been demonstrated that with practice human reliability can be improved by several orders of magnitude. Frank Hawkins quotes that an error rate of 1 in 1,000 might be thought of as “pretty good” in most circumstances.
Factors Affecting Human Reliability
Among the factors affecting human reliability are:
•Length of time of exposure to risk.
•Degree of risk
•Mental and physical health.
•Innate psychological characteristics.
•Innate physiological characteristics.
•Personality deficiencies.
•Stress factors.
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•Experience.
•Motivation.
•Skill level.
Errors General
“Error” is a generic term which describes all those occasions in which a series of mental or physical activities do not achieve their intended effect.
Human error ranges from a slip of the tongue to those that caused the terrible cost to human life in disasters such as the Tenerife runway collision in 1977, the Bhopal methyl isocyanate tragedy in 1984 and the Challenger and Chernobyl catastrophes in 1986.
The aviation industry is currently investing large amounts of funding in human error research and national authorities have all included the study of human error in Human Performance syllabi.
Error Generation
Although 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 to take out a young plant from a flower bed mistaking it for a weed. A cumulative error would be, for example, to issue an incorrect aircraft maintenance procedure which results in a series of accidents.
Broadly speaking error generation can be caused either by internal or external factors.
•Internal Factors
Among the internal sources can be:
•Mistaken perception.
•Misinterpretation of information.
•Preconceived assumptions.
•Experimentation.
•Faulty memory.
•Fatigue.
•Lack of practice. This is sometimes known as ‘deterioration effect’.
•External Factors
Some external sources are:
•Stressors.
•Ergonomics (bad design or layout of instruments).
•Economics (company or organisational pressures).
•Social environment (cultural misunderstandings).
Types of Errors
Different types of errors are discussed in their relevant chapters (and, in particular, Chapter 9 of these notes) however, in general, errors can be classified into three main groups:
• Faults. 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/emergency.
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•Slips. Slips do not satisfy the operator’s intent although the intent was correct. For example: the correct drill for the task/emergency was carried out but wrongly. The term “slips” can also be referred to as lapses.
•Omissions. An omission is simply missing out a process or step that should have been included. In well-practised, highly automatic tasks (reading checklists would be one example), unexpected interruptions are frequently associated with omissions.
•Violations. Sometimes appear to be human errors but they differ from slips and lapses in so far as they are deliberate “illegal” actions. They are conscious actions in violation of the rules, regulations or procedures.
The Learning Process
Introduction
We have, in this chapter, discussed the learning process in acquiring skills and skill development however the learning process also allows us to gain intellectual advance. In its simplest form, learning is an internal process which allows the mental acquisition and retention of data.
Types of Learning
Below is listed the types of learning and brief examples:
•Classical/Operant Conditioning. This is the behaviouristic approach of Pavlov where the recipient is taught through, principally, physiological responses.
For example: An experienced pilot’s reaction to a fire warning.
•Insight. The data is intellectually and cognitively understood and is retained. For example: A pilot setting up the on-board navigation equipment.
•Observational Learning/Imitation. The data from an outside source is replicated.
For example: A student pilot following-through on the controls during an approach and then executing the approach on his/her own shortly afterwards.
•Experience. Learning from our mistakes.
•Skill Learning. Observational learning, along with practice, plays an important role in the learning of skills (motor programmes). It involves motivation, attention, observation, much practice and corrective feedback.
Quality of Learning
Some of the factors affecting the quality of learning are:
•Intellectual capacity of the recipient.
•Quality of communication between transmitter and recipient.
•Applicability of the data.
•Motivation of both the transmitter and the recipient.
•Overlearning. This means simply carrying the training process beyond what is required to perform to the minimum acceptable level. Overlearning not only improves the chances of recall but makes the performance of the task more resistant to stress.
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Retention of Information
Information retention can be increased by the use of:
•Mnemonics
(“HASELL”, “FEFL” or “FREDA”).
•Memory Training
Among the methods commonly used are:
•Word/phrase or object association.
•Chunking.
•Repetition.
•Revision.
•Research.
Motivation
Whereas it is possible to learn without motivation, attention is essential. However, having said this, the learning process is vastly improved with motivation and high performance rarely comes without it. However, motivation is always enhanced by reinforcing successful endeavours. This topic is discussed in detail in Chapter 9 (Behaviour).
Experience
We all have the ability to learn from our experiences and mistakes and from those of others. An interesting reality is that in spite of the fact that age not only severely affects pilots’ learning abilities but slows both mental and physical reactions, their performance decreases by a very small amount, if at all, with advancing years.
Studies have come to the conclusion that these deficiencies are compensated for by experience.
Mental Schema
Mental schemas are mental representations of categories of objects, events and people. For example, most Englishmen have a mental schema for football so that simply hearing these words is likely to activate whole clusters of information in the long-term memory, including the rules of the game, images or players, goal posts, balls, vests, stadiums, green playing fields, winter days and perhaps even hotdogs.
In the example of the students in a graduate student’s office, their mental schemas of such an office led them to “remember” erroneously.
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