The term ‘Human Factors’ refers to the application of scientific knowledge, mostly from the human sciences of psychology, anthropology, physiology and medicine, to the design, construction, operation, management and maintenance of products and systems. The purpose of the application of this knowledge is to attempt to reduce the likelihood of human error and therefore the likelihood of negative outcomes while operating or using products or systems.
Most aircraft accidents and incidents are the result of errors (including slips and lapses) made by the people responsible for operating the aviation system. These people could be pilots, air traffic controllers, maintenance staff or executive managers of the various aviation organisations. Some of the errors committed by these people are the result of deliberate violations of rules and procedures. However, even the majority of errors resulting from violations do not come from any intent to harm anyone or commit a crime.
Some people believe that if a human is given a reasonable task to complete and they are adequately trained, then the individual should be able to repeatedly perform the task without error. However, applied research and accident investigation reports from around the world demonstrate that this view is incorrect. Competent humans conducting even simple tasks continually make errors, but in most cases, they recognise the errors they have made and correct them before any consequence of the errors is realised. In a small number of cases, they fail to either recognise the errors or fail to correct them before the consequences of the errors are realised.
Contemporary human factors application is now as much about understanding how groups of people, be they flight crew, cabin crew, maintenance staff, air traffic controllers or senior management teams operate, and why they make decisions and behave in particular ways, as it is about individuals. It is also about viewing accidents as part of the overall complex system which supported all the aspects of the operation. As such, it is about understanding how organisations manage risk and balance their safety obligations with their business imperatives.
Human factors incorporate a broad and complex body of applied knowledge aimed at more clearly understanding why errors occur.
ICAO (the International Civil Aviation Organisation) uses the SCHELL
model to represent the main components of human factors. SCHELL is an expanded version of this model. The SCHELL model gives an idea of the scope of human factors.
SCHELL stands for:
S = software: the procedures and other aspects of work design C = culture: the organisational and national cultures influencing interactions H = hardware: the equipment, tools and technology used in work E = environment: the environmental conditions in which work occurs L = liveware: the human aspects of the system of work L = liveware: the interrelationships between humans at work
The SCHELL model emphasises that the whole system shapes how individuals behave. Any breakdown or mismatch between two or more components can lead to human performance problems. For example, an accident where communication breaks down between pilots in the cockpit, or engineers at shift handover, would be characterised by the SCHELL model as a liveware-liveware problem. Situations where pilots or engineers disregarded a rule, would be characterised as liveware-software.
It is then not surprising that a modern definition of airmanship includes knowledge of the whole system:
“Airmanship is the consistent use of good judgment and well-developed skills to accomplish flight objectives. This consistency is founded on a cornerstone of uncompromising flight discipline and is developed through systematic skill acquisition and proficiency. A high state of situational awareness completes the airmanship picture and is obtained through knowledge of one’s self, aircraft, environment, team and risk.”
(from Redefining Airmanship. Tony Kern. 1996)