Human Factors and the SHEL Model

To err is human; a person can never be 100% error free. It is just about impossible as we are all prone to making errors at some point in time. This is where the study of human factors comes into play. What exactly are human factors anyway? Simply put, human factors is about people. It’s about people in their working and living environments, their relationship with machines and equipment, the surrounding environment, and their relationship with interacting with other people. The types of human errors can be classified according to the SHEL model. This model focuses on four key components: Software, Hardware, Environment, and Liveware. Hardware factors include the design of equipment, displays, and controls. Engineering control strategies have been implemented in this area such as easy access to critical controls or design layout in general. Other examples include the design of the landing gear handle to mimic the round shape of a landing gear tire or a flap slat handle which is designed in such a way as mimics the appearance of an aircraft’s flap. Software factors simply include airline policies, standard operating procedures, checklists and other similar items. Environmental factors include noise, temperature, humidity, time of day, and overall weather. The liveware portion focuses on the interaction of people such as other crew members in the cockpit, communicating with air traffic control, or company management. While eliminating errors is nearly impossible, by improving cockpit designs, constant monitoring of accidents, incidents, and other reports such as NASA’s ASRS reporting system, these errors can be mitigated. Today’s air transportation system has an excellent safety record compared to the early days of aviation due to the fact new improvements are always occurring in the field of human factors.

Reference: Wells, Alexander T. & Rodrigues, Clarence C. (2004). Commercial Aviation Safety. New York:
The McGraw-Hill Companies, Inc.