Saturday, February 10, 2018


Malfunctioning processes has an impact on safety is a fact known throughout the aviation industry. Any undesired processes within a technical system are known to drastically impact safety. Rarely is the SHELL model checked for malfunctioning processes. In the interest of safety and to predict the effect of a hazard the aviation industry is implementing the SMS system as an additional layer of safety. There are several considerations and interaction in the SHELL model to analyze the effect these interactions have on aviation safety. Knowledge becomes critical in analyzing these interactions. Accountability is the platform of SMS and a crucial element when applying human factors. SMS is a wonderful system when applied correctly to make corrections to mistakes, both what’s consider minor mistakes and major mistakes. In the interest of public safety, there is no alternative to safety. New approaches to safety, including SMS, are required to catch up to the increased demand for safety in air travel.

The system creates ragged edges that don’t fit.
Each component of the SHELL model represents a building block of human factors studies within aviation. The SHELL system is a safety risk management tool in a system environment considering Software, Hardware, Environment, Liveware and Liveware.  Liveware is the concept of how Liveware (human factors) interacts with other Liveware (human factors) and the other components within the SHELL module. This system is a conceptual model of human factors that clarifies the scope of aviation human factors and assists in understanding the human factor relationships between system resources, or environment and the human component in the system. The model adopts a systems perspective that suggests the human is not the sole cause of an accident. The systems perspective considers a variety of contextual and task-related factors that interact with the human operator within the system to affect operator performance. As a result, the SHELL model considers both active and latent hazards in the system.

The human component is at the center of the SHELL model that represents the modern air transportation system. This is a critical and flexible component in the system, interacting directly with other system components, namely Software, Hardware, Environment and Liveware. Human senses for collecting vital task and environment-related information are subject to performance. A human sense does not detect the whole range of sensory information available. The circadian rhythm and emotions are triggers for variations in human performance. Humans are variables in information processing effectiveness and influenced by motivation. E.g. aircraft display, instrument and alerting, or warning system design are engineered to reduce the effect of these variables. 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.

The key to success is not in the edges but within the system itself.
Humans function effectively within a defined range of environmental conditions (tolerable for optimum human performance), with performance affected by physical environmental factors such as temperature, vibration, noise, g-forces and time of day as well as time zone transitions and working environments.

The concept of SMS that we don’t manage risks; we lead personnel, manage equipment and validate operational design for improved performance above the safety risk level bar is strengthen by including the SHELL model in a root cause analysis and risk assessment. A lesson learned from the SHELL model is that it comes with ragged edges, which also is characteristics of an effective SMS.