Human Factors...and Runway Safety

Three out of four accidents result from less than optimum human performance.

The human element is the most flexible, adaptable, and valuable part of the aviation system, but it is also the most vulnerable to influences that can adversely affect its performance.

The term "pilot error" may indicate WHERE in the system a breakdown occurs, but it provides no guidance as to WHY it occurs. The effort of uncovering the WHY we make mistakes is generally know as the study of Human Factors. This study is more than an endeavor by medical or psychological experts; it must be multidisciplinary in nature. In aviation - and with pilots in particular - some of the human factors to consider when examining the human role are decision-making, design of displays and controls, flight deck layout, communications, software, maps and charts, operating manuals, checklists and system procedures. Anyone of the above could be or become a stressor that triggers a breakdown in the human performance that results in a critical human error.

A model used by some human factors analysts is S-H-E-L, where the S stands for software (to include procedures), H is for hardware, E is for environment and L is for live ware (the human). With these for letters circling another L, representing the individual under study, we have a model looking like this:

diagram with the letters S and H on first row; on the next row an L centered between S and H; on the last row the letters L and E.  There's a line going from each letter to the L in the middle.

The two L's represent the human-to-human interaction that does become primarily a psychological study.

The following are some of the more obvious components of this interaction.

Software-Liveware. This encompasses aspects such as the use of manuals and checklists as well as the procedures we are expected to execute in the system.

Hardware-Liveware. This is basically the human-to-machine interface. Here is where we analyze the design of the machine, the coding and location of instruments, and the movement of controls to name a few. Sometimes the adaptability of the human will mask the deficiency of the design.

Environment-Liveware. In the past, the human had to adapt to the helmet, the speaker, the mask, the oxygen system and the climate as well as the G-forces. Although some of this cannot be eliminated, it has become our practice to begin adapting the man-made devices to the human and to mitigate environmental drawbacks as much as possible. Included in this arena would also be spatial illusions and disorientation.

Liveware-Liveware. This is the interface between people. Much of the focus in this heading is directed at the breakdown of teamwork.

Motivation can play a significant difference between what a person can and actually will do. Motivated individuals perform with greater effectiveness than unmotivated, all else such as qualifications being equal. But exceptional motivation cannot always compensate for a shortcoming in another area such as human disconnect with a hardware or software issue.

Controlling Human Error. The control of human error should take on two approaches. First, it is necessary to make the effort to minimize the occurrence of errors. Strive to ensure high level of competence; design controls so that they match human characteristics; provide proper checklists, procedures, maps, markings lighting, Standard Operating Procedures (SOP); reduce noise, vibration, temperature extremes and other stress-inducing or distracting situations.

Eliminating human errors is an unrealistic goal since errors are a normal part of human behavior. So the second approach to the controlling of human error is to reduce the consequences of those errors that will occur. AMASS, for example, is not designed to be an incursion prevention device. It is a device to detect an error and thereafter prevent a collision.

Questions? Comments? Contact Dan Cilli in the Southern Region Runway Safety Program Office at (404) 305-5596 or via e-mail at