Introduction to Human Factors

by Kent B. Lewis
“A broad field that studies the interaction between people and machines for the purpose of improving performance and reducing errors. As aircraft become more reliable and less prone to mechanical failure, the percentage of accidents related to human factors increased. Some aspect of human factors now accounts for over 80 percent of all accidents. Pilots who have a good understanding of human factors are better equipped to plan and execute a safe and uneventful flight.” (FAA Instrument Flying Handbook, 2001, p. 1-1)
Within human factors, specializations develop that use an interdisciplinary approach to the scientific study of the complex human-machine system. Examples of these specializations are aeromedical, critical incident response, first responder stress debrief, professional standards and pilot assistance.
  • Human factor elements include:
  • Design/System Failure
  • Organizational
  • Supervisory
  • Medical/Physiological/Psychological
  • Communications
  • Crew Resource Management
  • Aeronautical Decision Making
  • Attitude/Personality
  • Knowledge or Skill
  • Sensory-Perceptual
Mishaps: “WHO” did “WHAT?”
“The Naval Safety Center periodically publishes a list of the most common aircrew errors, shown below:
  • Inadequate crew coordination
  • Procedural violation
  • Physical or mental condition
  • Misuse of flight controls
  • Inadequate flying speed
  • Poor flight preparation
  • Inadequate lookout procedure
While the above designations are good descriptors concerning human error mishaps, they do not tell us much about the “Whys”. From a human factors standpoint, we need to relate the occurrence of mishaps to the behavior of people in the performance of their jobs. Accomplishing this may may be possible if we can more accurately define human factor “causes” of accidents, and through an understanding of the capabilities and limitations of human performance, develop improved mishap prevention measures.” (Naval Postgraduate School Aviation Psychology Lecture Summaries, 1992, p.3)

These same type of errors may result in injury to factory workers, poor performance of surgical teams or inefficient business management. Development of intervention strategies to combat poor performance and optimize system capabilities are key to everyone’s bottom line. To do this, we must identify “Why” and target the most appropriate levels for intervention.

DoD and the FAA are currently collaborating on defining human factor causes with the development of a Human Factors Analysis and Classification System (HFACS). Traditional intervention strategies focus on prevention of specific types of accidents, such as Controlled Flight Into Terrain (CFIT) or Stall/Spin mishaps rather than human error. Corrective recommendations have been focused on decision-making vs a wide range of possible human error categories. Causal factors must be analyzed and classified to accurately capture and recreate the complex layers of human error in context with the individual, environment and mishap or event. The resulting taxonomy will address latent failures of the system and active failures of the operator, from the earliest opportunity for intervention to the last.
The DoD HFACS model currently addresses these basic layers of system failure:

Organizational influences
  • Resource/Acquisition management
  • Organizational climate
  • Organizational process
  • Inadequate supervision
  • Planned inappropriate operations
  • Failure to correct known problem
  • Supervisory violations
Preconditions to Acts
  • Environmental factors
  • Physical
  • Technological
  • Condition of individuals
  • Cognitive factors
  • Psycho-behavioral factors
  • Adverse physiological states
  • Physical/mental limitations
  • Perceptual factors
  • Personnel factors
  • Coordination/communication/planning factors
  • Self-imposed stress
  • Errors
  • Skill-based
  • Judgement and Decision -making errors
  • Misperception errors
  • Violations
As part of the FAA’s Safer Skies initiative, Joint Safety Analysis Teams and Joint Safety Intervention Teams studied civil aviation accidents associated with human factors. The results were classified based on NTSB recommendations for corrective action. The results found that that NTSB recommendations routinely targeted Organizational/Administrative levels (36%) and Technological/engineering approaches. “However, unlike the NTSB where relatively few recommendations targeted the human, nearly 1/3 of those obtained from JSAT/JSATs did so.” (Developing a Methodology for Assessing Safety Programs Targeting Human Error in Aviation, 2004, p. 4) Analysis suggests that additional interventions should be directed towards skill based errors, violations and modification of the task and environment.

In the majority of cases, a mishap “happens” before the aircraft has ever left the ground, at times as high as the organizational or supervisory level. Mishaps are caused by hazards with human and material factor roots. Identification of hazards through the use of system based safety programs and risk management methodologies will result in interventions at the earliest and most appropriate levels. The earlier that a hazard is identified, the earlier it can be assessed, eliminated or controlled.

Safety Quote
“You can’t go on liberty if you’re dead”.
Lt Col Michael Kurth, HMLA-369
Navy Cross recipient
Desert Storm

Preflight yourself before you go….Know your personal limitations. Use the PAVE checklist.

Another NASA, DoD and FAA initiative was the National Plan for Civil Aviation Human Factors

Two goals:
1. Reducing error in human-system interactions
2. Increase efficiency of human-system performance

The national agenda focuses on 2 major elements

1. Human-centered automation
2. Selection and training
3. Human performance assessment
4. Information management and display
5. Bioaeronautics

-Application of research:
1. Create environment for change
2. Develop HF education and training programs at all levels
3. Equip personnel and facilities with modern tools and techniques of the HF engineering discipline.
4. Develop infrastructure to translate and disseminate human factors products.


Control of the Mission Versus Control of the System

by Matt "Pug" Boyne

Thursday, February 12, 2009

As flight deck technology gains greater sophistication, flight deck designers will continue to create additional information sources and control measures. It is an observation that aircraft accidents have a greater chance to occur when pilots cede control of the aircraft to automated systems rather than keeping control of the aircraft themselves. This may be referred to as a choice to use mission level automation (Rogers, Schutte & Latorella, 1996.) At this point pilots have moved from a controlling function to a monitoring one and if not properly engaged may lose situational awareness.

A classic example for lessons learned in this area is the American Airlines 757 crash on approach to Cali, Columbia in December of 1995 (Aeronautica Civil of the Republic of Columbia, 1996.) While rushing to prepare for a new approach to the airport the pilots loaded an incorrect navigational point into their flight management computer and then trusted that the autopilot system would bring them to the correct position. At this point they abrogated their control authority and moved to a monitoring position. Due to further distractions with navigational charts, both pilots allowed their monitoring duties to suffer as well. Unfortunately, due to confusion as to their location and the high terrain surrounding the airport, the flight management system directed the autopilot onto a path that resulted in collision with the mountains, loss of life and aircraft.

This example is used to describe the real risks to cockpit automation. As long as pilots retain control over the mission of the aircraft, they will maintain a higher level of situational awareness than when they move to a monitoring position. If the automated systems are used, they should be employed as a work load mitigator and not a placed in a decision making role. For tasks that are not mission critical, that may be thought of as aircraft or system specific, such as cabin temperature or fuel balancing, delegation to the automated system will not result into a significant safety hazard. Monitoring can be thought of in a time versus risk assessment. If sufficient time exists for human intervention before given a critical situation, delegation to automation will reduce workload, improve effectiveness and minimize fatigue.

This does not imply that pilots must at all time maintain physical control of the aircraft, as in manually flying. Rather the control must be in a dynamic sense. This means that the aircraft will not change profiles without pilot input, which may be through the flight controls manually or by engaging an autopilot mode control


Aeronautica Civil of the Republic of Columbia (1996). Aircraft accident report: Controlled flight into terrain, American Airlines Flight 965, Boeing 757-223, N651AA, near Cali, Columbia, December 20, 1995. Santafe de Bogota, D.C., Columbia: Author.

Rogers, W.H., Schutte, P.C. & Latorella, K.A. (1996). Fault management in aviation systems. In P. Parasuraman & M. Mouloua (Eds.), Automation and Human Performance: Theory and Applications. Mahwah, NJ: Lawrence Erlbaum Associates.

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Crew Resource Management

Dispatch Resource Management Advisory Circular AC 121-32 1995.pdf


Human Factors Checklist Facilitator's Guide Dr Ciavarelli.pdf

Team Resource Management Facilitator's Guide.pdf


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