1. Human Factors Analysis and Classification System (HFACS)
Organizational
Factors
Unsafe
Supervision
Pre-Conditions
for
Unsafe Acts
Unsafe
Acts

2. Swiss Cheese Model

3. Errors Violations UNSAFE ACTS Exceptional Routine Perceptual Errors
What Happened
Violations
Errors
Exceptional
Routine
Perceptual
Errors
Skill-based
Decision
Unsafe Acts
The unsafe acts committed by aircrew generally take on two forms, errors and violations.
Errors are generally defined as mental or physical activities that fail to achieve their intended outcome. There are three basic error types - skill-based, decision, and perceptual. Errors, are not surprising given the fact that human beings by their very nature make errors. Consequently, aircrew errors are seen in most mishaps – often as that last fatal flaw before a mishap occurs
Violations are actions that represent a willful disregard for rules and regulations and typically occur less frequently.. There are two basic types of violations - routine and exceptional.
Using this simple classification scheme, the investigator must first decide if an unsafe act (active failure) was committed by the operator (aircrew, maintainer, etc.). If so, the investigator must then decide if an error occurred or a rule was willfully violated. Once this is done, the investigator can further define the causal factor as a specific type of error or violation.
Unsafe
Acts

4. Preconditions for Unsafe Acts
Why it Happened
Substandard
Conditions of
Operators
Practices of
Physical/
Mental
Limitations
Crew
Resource
Management
Personal
Readiness
Adverse
Physiological
States
Mental States
Non-Supervisory
Tolerance of
Unsafe Acts
Preconditions
for
Unsafe Acts
Unsafe
Acts
Preconditions for Unsafe Acts
Simply focusing on unsafe acts is like focusing on a fever without understanding the underlying disease causing it. As such, investigators must dig deeper into why the unsafe acts took place.
Latent, pre-conditions of pilots directly influence their performance. In this framework, there are two main categories of preconditions for unsafe acts - substandard conditions and substandard practices.
Substandard conditions of operators (pilots) include adverse mental states, adverse physiological states, and physical and mental limitations.
Substandard practices of operators (pilots) include interpersonal resource (mis)management, the failure of others outside of management to correct known deficiencies, and personal readiness

5. Unforeseen Known UNSAFE SUPERVISION Unrecognized Inadequate Planned
Hazardous
Operations
Inadequate
Documentation/
Procedures
Supervision
Planned
Inappropriate
Failure to
Correct
Problem
Supervisory
Violations
Unsafe
Supervision
Preconditions
for
Unsafe Acts
Acts
Unsafe Supervision
Often the mishap causal chain of events can be traced back up the supervisory chain of command
Deficiencies in supervision and line management directly influence the unsafe conditions and actions of operators.
Unforeseen - those unsafe management and/or supervisory practices that go unnoticed, yet are not result of negligence or adverse behavior – pertains to middle management (not CEO or higher organizational level)
Known - unsafe management of operations which were a direct result of supervisory action or inaction [NOTE: “known” in this instance does not imply that supervisor intentionally did something wrong, rather it refers to those instances in which supervisor erred in managing a known aspect of the operation]

6. Organizational Influences
Climate
Resource
Management
Operational
Process
Organizational
Influences
Unsafe
Supervision
Preconditions
for
Unsafe Acts
Acts
Organizational Influences
Fallible decisions of upper-level management directly effect supervisory practices, as well as the conditions and actions of operators. These latent failures generally revolve around issues related to resource management, organizational climate, and operational processes.

7. Human Factors Analysis
Provides More than just an Accident Investigation Tool
Organizational
Factors
Preconditions
for
Unsafe Acts
Unsafe
Acts
Supervision
Opportunity for Pro-active Action by Management
Failures in your System’s Defenses
We all (senior management, safety staff, line supervisors, and operators) play a role in preventing aviation accidents.
In many respects you are the most important link in the ‘safety chain’. You have the most immediate influence on committing or preventing unsafe acts. As previously discussed, latent conditions are out there, patiently waiting like a set of wires for an inattentive pilot to come along. You, working in the environment day in, and day out often see the “Preconditions” and “Supervisory” weaknesses long before an accident results. Everyone here has heard “I knew it was going to happen, I just didn’t know when.” or “I could have told you he was going to have an accident.”
What we need to do is to intervene and correct these systems (or individuals) before the accident can occur. To accomplish this I recommend the following strategies:
Get actively involved – Look for the hazards in all operations; learn, and use the tools and techniques of managing risk. Correct what you can, elevate to your supervisor those issues that threaten operations that are above your ability to correct.
Keep folks informed – If you identify hazards which can not be controlled notify your supervisor and the other operators working in that environment. Within DOI/USFS we expect you to use the SAFECOM (Safety Communications) system to keep us informed of hazardous situations as well as for accidents/incidents.
Don’t quit! – If you see a problem and either can’t fix it yourself, or can’t seem to get the command attention you feel the situation deserves…don’t give up. Not all issues will be resolved immediately, or to your satisfaction. If eliminating the hazard is not feasible, seek ways to minimize the risk.