Gremline Flight Safety Report: The Emergence of Human Factors by Professor Helen Muir

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the gremline digest —  the emergence of human factors

The Emergence of Human Factors
by Professor Helen Muir  © 2009

Professor Helen Muir is Professor of Aerospace Psychology and Head of Human Factors Group at Cranfield University College of Aeronautics. ”Human Factors” is a topic central to flight safety but, in my opinion, is more often talked about than understood. This article gives a clear and concise introduction to the increasing awareness of the role played by human factors in aircraft accidents. Awareness of the crucial influence human factors have on accident rates is probably lower among General Aviation pilots (and instructors) than in any other sector of aviation. An understanding and constant awareness of the important relationship between human factors and safety will help to reduce accident rates.
We thank Professor Muir for a thought-provoking conversation about human factors and for her kind permission to publish this article on Gremline.



For centuries before the first flight of Orville and Wilbur Wright, humans had engaged both their imagination and ingenuity in an attempt to emulate bird flight. This early achievement began an evolutionary programme which has led to supersonic civil transport, to spaceflight and to outstanding military capabilities. In fact, it is difficult to imagine a more impressive tribute to applied physical sciences than the recognition of the achievements in aeronautics and astronautics.
      To recognise the aerospace achievements in solely engineering terms would be to ignore an important element. The fact that aircraft are controlled by people who, together with the many ground support personnel essential to their safe and effective operations, had led to a need to understand the human role in aircraft operations. This in turn had led to the involvement of the applied human sciences in aerospace. As a consequence we are now fully aware of the fact that flight crews and other operational personnel must be selected and trained according to clearly defined criteria and that equipment must be designed to ensure that the task demands will not exceed the capabilities of human performance.


The emergence of the discipline of human factors has been relatively recent, although its origins can be traced back over sixty years. The Second World War provided a huge impetus to the development of aviation and, as part of this, evidence of the human problems became apparent. As early as 1940, the ‘70% human error’ in aircraft accidents findings has been published. The fact that the performance of combat aircraft and the success of missions depended on the skill of the crews performing in extremely hostile environments led to the realisation that our understanding of the acquisition and maintenance of skills was severely limited. This subsequently led to the initiation of new research programmes.
      In 1939, the Head of the Psychological Laboratory at Cambridge University, Sir Frederick Bartlett, was commissioned by the Medical Research Council to undertake research into the problems associated with military aviation. The team which he developed was to dominate academic psychology in the United Kingdom for the next generations and its research into the fundamental nature of human skills led to contributions in the area of aircrew selection and training, the effects of sleep loss and fatigue, and aspects of visual perception and display design. The ‘Cambridge Cockpit’ developed largely by K.J.W. Clark was used for these studies. This was a piece of experimental equipment built around a Spitfire cockpit into which was fitted a panel with instruments which responded in a realistic manner to movements of the controls. Using this equipment, the experimental psychologists demonstrated that when fatigued, the degradation in pilot performance led to peripheral activities such as checking fuel being overlooked with attention being paid only to one or two instruments, the others being ignored. (Reference 1)
      In America, research into the design of displays and instruments also began to be undertaken. In 1947, Fitt and Jones (Reference 2) identified nine sources of errors made in the interpretation of instruments including misinterpretation of information, legibility problems, scale of interpretation errors and illusions.


The late 40s and 50s saw the publication of numerous papers in the field of skill acquisition and control performance, much of which is based on research into the flying task. For example, in 1947 Williams (Reference 3) suggested that the pilot’s task could be analysed into four sub-goals described as directional, attitudinal, temporal and mechanical.
Investigations by Mackworth (Reference 4) into the performance of radar operators made a major contribution to the understanding of our ability to monitor situations. In the UK, the 50s saw the establishment of ergonomics as a discipline, whereas in the USA the term ‘human factors’ was introduced. These words are usually regarded as synonymous.
      The late 50s and early 60s will be remembered for important developments in our understanding of perception and communication, notably by Broadbent (Reference 5) who was by then leading the team at Cambridge. This work has formed the basis of what has become known as Cognitive Psychology. This involves our understanding of how we take in information from the world around us and process it in such a way that we make a decision to take some action or store information in our memory systems. During this period, our knowledge and understanding of the influence of stress on performance and the influence of different types of stress, e.g. environmental, work, domestic etc., was substantially increased (Reference 6). Our knowledge of all these processes is obviously fundamental to understanding human performance of the flying task since it enables us, for example, to identify types of error and their associated causes as seen in the table at the end of this article.
      The 1970s saw the application of much of this work to the flight deck. Studies of pilot workload were introduced in order to ensure that the workload associated with flying the aircraft did not at any time exceed the capabilities of the required crew at any period of the flight. These techniques became part of the certification process. Indeed, workload assessment techniques were later used for the determination of whether a civil cockpit should be crewed by two or three pilots.
      The 1970s also saw the first attempt by aviation psychologists to conceptualise the relationship between the human and the rest of the aircraft system. In 1972, the SHEL model was published by Edwards (Reference 7) in which the interaction between the Hardware, I.e. the aircraft, the Software, in other words the operational procedures, rules, etc., the Lifeware involving the flight crew and the Environment e.g., the physical, economic and social factors, was described.


Since the early 70s, one of the principal topics under consideration has been the development of flight deck automation. Over the last 15 to 20 years there has been a rapid evolution of display and control devices including the introduction of electronic computing devices which provide a range of support facilities for aircraft guidance and control. In the early stages of automation, the systems were developed by engineers and human factor specialists were not involved until the system had been installed in the cockpit and required evaluation. The increasing awareness of human factors has led to the situation where the major manufacturers now involve human factor expertise at all stages of the design process. The recognition that flying a modern aircraft is no longer a one man effort but rather a team managing a system has led to the acceptance of the importance of human factors training and indeed crew resource management for all pilots (reference 10). In the space of sixty years, human factors has not only emerged as a discipline but has been recognised as being of such importance within the aviation community that in the UK human factors is part of the licensing requirement for all new pilots. In addition, crew resource management training is mandatory for all commercial pilots and part of recurrent training. The lead shown by pilots to recognise the value of human factor training will, it is hoped, be followed by other personnel in the industry responsible for safety. The complete elimination of human errors may be an unrealistic goal but advances to minimise the causes and consequences of error in aviation is one to which all human factors specialists are dedicated.

Table: Examples of Types of Error and Their Associated Causes

1. Davis DR, Pilot Error: Some laboratory experiments, His Majesty’s Stationery Office, London (1948).

2. Fitt PM & Jones RE, Analysis of 270 “pilot error” experiences in reading and interpreting aircraft instruments, (Report TSEAA-694-12A) Wright-Patterson Air Force Base, OH: Aeromedical Laboratory, (1947).

3. Williams AC, Preliminary analysis of information required by pilots for instrument flight. In SN Roscoe (Ed), Aviation Research Monographs 1 (1) Urbana: University of Illinois, Aviation Research Laboratory, (1947).

4. Mackworth NH, Researches on the measurement of human performance (Medical Research Council Special Report Series 268) London: His Majesty’s Stationery Office, (1950).

5. Broadbent DE, Perception and Communication. Pergamon Press, (1958).

6. Broadbent DE, Decision and Stress. Academic Press (1972).

7. Edwards E, Man and Machine: Systems for Safety. In Proceedings of British Airline Pilots Association Symposium (pp 21-36) London: British Airline Pilots Association, (1972).

8. Ruffel Smith HP, A simulation study of interactions of pilot workload with errors, vigilance and decisions. (Technical Memorandum 78482) Moffett Field CA: NASA-Ames Research Centre, (1979).

9. Edwards E, Flight deck automation; some human factor aspects, AERO 16, Aviation Ergonomics, Loughborough, (1976).

10. Wiener EC, Kanki BG and Helmreich RL, Cockpit Resource Management, Academic Press, (1993).


It is worth noting that although Professor Muir’s article concentrates on the application of human factors to aviation the same principles may be applied to any industry with the reduction of human error in mind.



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