SHELL model

In aviation, the SHELL model (also known as the SHEL model) is a conceptual model of human factors that helps to clarify the location and cause of human error within an aviation environment.^: 1

It is named after the initial letters of its components (Software, Hardware, Environment, Liveware) and places emphasis on the human being and human interfaces with other components of the aviation system.^: 3

The SHELL model adopts a systems perspective that suggests the human is rarely, if ever, 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 aviation system to affect operator performance. As a result, the SHELL model considers both active and latent failures in the aviation system.