senses for collecting vital task and environment-related information are subject to limitations and degradation. Human senses cannot detect the whole range of sensory information available. For example, the human eye cannot see an object at night due to low light levels. This produces implications for pilot performance during night flying. In addition to sight, other senses include sound, smell, taste and touch (movement and temperature). Information processing Humans have limitations in information processing capabilities (such as working memory capacity, time and retrieval considerations) that can also be influenced by other factors such as motivation and stress or high workload. Aircraft display, instrument and alerting/warning system design needs to take into account the capabilities and limitations of human information processing to prevent human error. Output characteristics After sensing and processing information, the output involves decisions, muscular action and communication. Design considerations include aircraft control-display movement relationship, acceptable direction of movement of controls, control resistance and coding, acceptable human forces required to operate aircraft doors, hatches and cargo equipment and speech characteristics in the design of voice communication procedures. Environmental tolerances People function effectively only within a narrow range of environmental conditions (tolerable for optimum human performance) and therefore their performance and well-being is affected by physical environmental factors such as temperature, vibration, noise, g-forces and time of day as well as time zone transitions, boring/stressful working environments, heights and enclosed spaces. Components Software Non-physical, intangible aspects of the aviation system that govern how the aviation system operates and how information within the system is organised. Software may be likened to the software that controls the operations of computer hardware. Software includes rules, instructions, Aviation regulations, policies, norms, laws, orders, safety procedures, standard operating procedures, customs, practices, conventions, habits, symbology, supervisor commands and computer programmes. Software can be included in a collection of documents such as the contents of charts, maps, publications, emergency operating manuals and procedural checklists. Hardware Physical elements of the aviation system such as aircraft (including controls, surfaces, displays, functional systems and seating), operator equipment, tools, materials, buildings, vehicles, computers, conveyor belts etc. Environment The context in which aircraft and aviation system resources (software, hardware, liveware) operate, made up of physical, organisational, economic, regulatory, political and social variables that may impact on the worker/operator. Internal air transport environment relates to immediate work area and includes physical factors such as cabin/cockpit temperature, air pressure, humidity, noise, vibration and ambient light