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Contact: Cary Meier, Systems Safety Analysis Branch, AAL 240, Alaska
Posted On: July 24, 2005
System Safety! What is it?
. . . human performance system safety. This is more along the lines of how a human uses a component, how a process is followed. . .
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SYSTEM SAFETY – WHAT IS IT?
What is System Safety? The textbook definition is: “The
limiting of accident risk through design of a systematic, methodical, and
forward-looking hazard identification and control program, beginning in the
conceptual design phase and continuing through its development, fabrication,
testing, production, use, and ultimate disposal.”
Let’s expand by saying that it is about risk management, human factors,
ergonomics, equipment design, reliability programs, continued analysis systems,
root cause analysis, and the management of error. We can further divide
all of these things into two basic groups.
TECHNOLOGY SYSTEM SAFETY
Let us call the first group “technology system safety”. This
group is the engineering side, the examination of present human engineering,
design criteria, principles, and practices to achieve success through
integration of the human into the system, subsystem, or equipment. Further
more it is the addressing of human factors input into a component’s design,
development, testing, and evaluations processes. Emphasis is put on the
systems approach to human-machine interfacing. This technology system
safety is the reliability of the component, documenting the life of the
component to establish life limitations, and other issues such as the size of a
control knob, if it can be turned when wearing gloves, if the display of the
component can be seen if the sun glares on the glass, and so on. This also
includes the analytical techniques and documentation requirements to provide
proper design of equipment and systems and to protect against products
liability. Safety concepts, legal concepts, qualitative hazard evaluation,
hazard classification, system life cycle safety, statistical distributions,
fault tree and software safety analysis are integral processes of technology
system safety.
HUMAN PERFORMANCE SYSTEM SAFETY
We also have what could be called “human performance system
safety”. This is more along the lines of how a human uses a component,
how a process is followed, how an activity is conducted, or the measurement of
human performance and how errors are managed. This requires the
application of the six safety attributes of System Safety (responsibility,
authority, procedures, controls, process measurement, & interfaces) to
identify the hazards related to all aspects of a process and the determination
of their causes. This involves defining the physical and functional
characteristics of a process by employing all the information available (design
documents, operating procedures, standards, equipment, environment, human
factors, training, etc.) and relating the interaction between this
information. Then the hazards are assessed to determine severity and
probability, and to recommend a means for their elimination or control.
After that an evaluation is conducted as a follow-up analysis to determine
effectiveness of preventive measures, addressing new or unexpected hazards, and
issuing additional recommendations if necessary. Human performance system
safety is the assurance that a human can perform any given action correctly and
safely each and every time.
Our primary focus or objective in Flight Standards is the application of
human performance system safety. This is where we need to target our
resources to enhance aviation safety and reduce accidents. Human error is
the leading primary cause of aviation accidents, while equipment failure
contributes a small percentage to the probable cause. Because of this, the
improvement of human performance through the application of system safety is
very important.
Cary Meier
Systems Safety
Analysis Branch, AAL 240,
Alaska
Reference Material and Organizations for this article:
Human Factors in
Aviation Safety, University of
Southern California
TapRooT® Root
Cause Analysis Problem Investigation Proactive Improvement, Paradies and
Unger
System Safety Society
NASA
NTSB
James Reason
Publications