Human Factors in Aircraft

Maintenance
This presentation explores the fundamentals of human factors in aircraft
maintenance. We'll examine how human capabilities and limitations affect
safety and efficiency, and explore strategies to mitigate potential risks.
What are Human Factors?
Definition Focus
Human factors refers to the study of how human capabilities In aircraft maintenance, human factors focuses on optimizing
and limitations interact with the workplace environment. interactions between personnel, systems, and the environment
to enhance safety, efficiency, and well-being.
The Evolution of Human
Factors in Aviation
In the 1970s, Cockpit Resource Management (CRM) training
1
was introduced, establishing new protocols for pilot
communication and teamwork.

By the 1980s, the concept evolved into Crew Resource

2
Management, broadening to include all flight crew members
and enhancing overall aviation safety.

In the 1990s, human factors principles were formally

3
integrated into aircraft maintenance training programs,
acknowledging that technical expertise alone wasn't sufficient
for safety.
Why Study Human Factors?
Regulation Prevention
Aviation regulators emphasize Human factors training helps
human factors because human people understand their natural
performance remains the most limitations while improving
variable element in the aviation organizational systems to
system, even as technology prevent errors.
advances.

Goal
The ultimate goal is to achieve zero accidents and incidents through a
comprehensive understanding of human performance and limitations.
The SHELL Model
Understanding Interfaces Key Components
The SHELL model helps clarify the location and cause of human Software (maintenance procedures, manuals, checklist
errors within aviation environments by focusing on interfaces layout, etc.)
between the human and other elements. Hardware (tools, equipment, aircraft structure)

Environment (physical conditions, work patterns)

Liveware (individuals)
Liveware (yourself)
Error Sources in the SHELL
Model

Software Hardware
Misinterpretation of procedures, Inadequate tools, poorly designed
poorly written manuals, and equipment, and difficult-to-maintain
ineffective software systems lead to aircraft contribute to errors.
errors.

Environment Liveware
Uncomfortable workspaces, poor Poor communication, inadequate
lighting, and excessive noise create training, and insufficient support
conditions conducive to errors. increase the likelihood of human
errors.
Human Limitations and
Error
While aircraft technology continues to improve, humans remain a constant
factor in aviation safety. We can educate, train, and support individuals, but we
must acknowledge that humans are fundamentally fallible. Implementing
procedures and interventions can help mitigate human errors and improve
safety.
The Shift in Accident Causes

80% 80%
Early Days Modern Era
In the early days of flight, mechanical Today, human error remains the
failures were the primary cause of leading cause of aircraft accidents.
accidents.
Human Factors in
Maintenance Accidents
Causes Percentage of Accidents

Pilot Error 33%

Inadequate Cross-Check 26%

Maintenance Deficiencies 12%

Human Failure vs Other
Causes
human failure is the most common
cause for modern aircraft incidents.
Aloha Airlines Flight 243 (1988)
Incident
1
An explosive cabin decompression ripped off a section of the fuselage during flight.

Investigation
The investigation revealed over 240 cracks in the aircraft's skin during inspection, 2
indicating systematic failures in maintenance procedures.

Human Factors
Multiple human elements contributed to the failed inspections,
3
including perceptual errors, inadequate lighting conditions, and
organizational deficiencies.
British Airways Flight 5390 (1990)

Incident
1 A captain was partially sucked out of the cockpit window at 17,300 feet during flight.

Cause
2 A windshield blew out during flight due to improper installation by a
maintenance manager using incorrect bolts.

Factors
Visual inspection errors, poor workplace lighting conditions,
3
and inappropriate maintenance tools led to the incorrect
installation.
Additional Case Studies
Good People Doing the Right
Thing, But...
Even skilled professionals can make mistakes. Accidents may occur when
good people try to do the right thing but are constrained by human limitations.
It's essential to recognize that even in systems with robust procedures and
regulations, human error remains possible.
The Error Chain
Link 1
Initial error or oversight is introduced. 1

Link 2
The error continues undetected through multiple checkpoints. 2

Link 3
The error chain ultimately results in an incident or accident. 3
The Swiss Cheese Model
Professor James Reason's Swiss Cheese Model illustrates how accidents can
occur due to the alignment of multiple weaknesses in a system. Each layer
represents a barrier or defense, and holes represent potential errors or
hazards. When these holes align, an accident can occur.
Murphy's Law and
Complacency
Murphy's Law states that "if something can go wrong, it will." This principle
underscores the inherent potential for human error. Complacency, a state of
self-satisfaction and reduced awareness, can be a significant risk factor in
aircraft maintenance. It's crucial to remain vigilant and recognize that even
systems with excellent safety records are not immune to potential errors.
Defenses Against Murphy's
Law
Murphy-proofing involves reducing the risk of human error through careful
design and process improvements. Specifically, tools and equipment can be
designed to prevent mishaps. This proactive approach helps create a safer
and more efficient workplace.
Promoting Constructive Work Environments
Even organizations with strong safety records can fall prey to complacency. The best defense is fostering a culture where employees
feel empowered to raise safety concerns and offer constructive criticism. Regular review of procedures and continuous improvement
of workplace conditions are essential elements of maintaining this vigilance.
Human Errors in Aircraft Maintenance Are Not
Random
Errors in aircraft maintenance are not random events but often occur due to factors such as limited attention span, fatigue, and
pressure to complete tasks quickly. Understanding these contributing factors allows us to create a more supportive and error-resistant
work environment.
Summary and Key
Takeaways
Human Factors SHELL Model
Human factors are crucial for The SHELL Model helps
aviation safety, focusing on identify potential error points in
how human capabilities and the interactions between
limitations influence workplace humans, hardware, software,
performance. environment, and liveware.

Error Mitigation
Understanding human limitations and implementing strategies like
training, procedures, and design improvements can help mitigate
human errors.