The SHEL Model examines the human factor in aviation. The International Civil Aviation Organization created this model to recognize interaction and mitigate human error. The physiological aspect of human interaction is the common denominator for all aspects of this model, which makes everything interdependent. The “Limeware” aspect of the SHEL Model is also known as the human element. Pilots, A&P mechanics, ATC controllers, management, engineers, and other individuals are all components of Limeware for the SHEL Model. This will take account for the production, limitation and interactions of humans involved within the aviation system. Liveware is the most critical and also the most flexible component of the SHEL Model. This is also the least predictable and most affected by internal and external factors. An example of this would be a PIC who has verified the aircraft is airworthy regarding paperwork and inspections, but the weather does not give favorable conditions for the flight. This would be an external factor forcing the PIC to make a no-go decision. An example of an internal factor would
be the PIC has been sick and not feeling well enough to fly, forcing them to remove themselves as a candidate to act as PIC. Both these examples are involving factors that affect the PIC, outside of the aircraft or airport environment.
