The Human Factor
WHAT ARE HUMAN FACTORS IN AVIATION MAINTENANCE
Welcome to a journey through the intricate world of human factors in aviation maintenance. In a recent episode of The CotAcasT, I delve into this realm where the precision of machines meets the complexity of human behavior. As we navigate through the history, challenges, and innovations in this field, we uncover a critical aspect of aviation that often remains unseen yet is vital to the safety and efficiency of every flight. But what are human factors, and why do they play such a pivotal role in aviation maintenance? How have our understandings and approaches evolved over time, from the early days of trial-and-error to today's sophisticated systems? Most importantly, we explore a crucial question: Are we doing enough to address the human element in maintaining the aircraft that crisscross our skies?
Since 1988, the Federal Aviation Administration (FAA) has been formally engaged in addressing the critical issue of human error in aviation. Interestingly, the key to enhancing aircraft safety in the future lies not just in technological advancements but in a more fundamental aspect: educating employees to recognize and prevent human errors. Data from accident analyses reveal a striking fact: about 75–80 percent of aviation accidents stem from human error, with roughly 12 percent linked to maintenance issues. While mistakes made by pilots often result in immediate and visible consequences, those related to maintenance are usually more latent, manifesting subtly over time. This distinction underscores the importance of focusing on human factors in aviation maintenance as a pivotal aspect of overall aviation safety.
Human factors are concerned with optimizing performance … including reducing errors so that the highest level of safety is achieved and maintained. —Ron LoFaro, Ph.D. FAA
Human factors is the study of how people interact with their environments. —FAA-H-8083-25, Pilot’s Handbook of Aeronautical Knowledge
Human factors are those elements that affect our behavior and performance, especially those that may cause us to make errors. —Canadian Department of Defense (video)
Understanding why human conditions like fatigue, complacency, and stress are crucial in aviation maintenance is key to enhancing safety. These elements, collectively known as human factors, play a significant role in aviation incidents. It’s widely acknowledged that around 80 percent of maintenance errors are influenced by these factors. Unaddressed, they can lead to critical events, worker injuries, inefficiencies, and, in some cases, serious accidents. Common examples of such errors include incorrectly installed parts, missing components, and overlooked necessary checks. The challenge with mistakes made by aviation maintenance technicians (AMTs) is their often undetectable nature. Unlike other aviation safety threats, these mistakes can remain hidden, silently compromising aircraft safety over extended periods. This is particularly concerning given the unique human factors AMTs face: working at odd hours, in confined or elevated spaces, and under varying temperature and humidity conditions. The need for meticulous attention to detail compounds the job's physical demands. Moreover, the nature of their tasks often means spending more time preparing for a task than executing it. This complex environment highlights the critical need for addressing human factors in aviation maintenance, not only for the safety of the aircraft but also for the technicians' well-being.
Given these intricate challenges aviation maintenance technicians face, one critical question emerges: How can the aviation industry better support AMTs in mitigating these human factors? This query opens the door to exploring innovative solutions, such as advanced training programs, ergonomic work environments, and enhanced safety protocols. These measures not only aim to reduce the incidence of human error but also ensure the mental and physical well-being of the technicians. Ultimately, the goal is to foster a culture where safety is paramount and everyone is equipped with the tools and knowledge to contribute effectively to this mission. The answer to this question can potentially revolutionize aviation maintenance practices and significantly elevate aviation safety standards.
WHAT ARE HUMAN FACTORS?
Human factors" is a term that has gained significant traction in the commercial aviation industry, particularly as it becomes increasingly clear that human error is a primary contributor to most aviation accidents and incidents, more so than mechanical failures. This field includes multiple disciplines, including psychology, engineering, industrial design, statistics, operations research, and anthropometry. It delves into understanding human capabilities and applies this knowledge to designing and implementing various systems and services. A crucial aspect of human factors is the integration of these principles into the aviation maintenance environment, ensuring their effective application.
For Aviation Maintenance Technicians (AMTs), the ability to solve problems quickly and efficiently is paramount. They are routinely faced with situations that require immediate troubleshooting and response, which can be mentally and physically demanding. This constant pressure, unfortunately, can lead to significant stress, illustrating the need for incorporating human factor considerations not just in equipment and procedures but also in the overall work environment and well-being of maintenance personnel. Understanding and addressing these factors is essential in creating a safer, more efficient, and less stressful maintenance workflow.
HISTORY
The concept of human factors in aviation evolved significantly over time. Initially, before World War I, human-machine compatibility was assessed through simple trial and error. This approach shifted notably during the American Civil War with the U.S. Patent Office's focus on the usability of mass-produced military equipment. World War I and II were turning points, highlighting the need to understand human capabilities and limitations in using complex machinery, leading to the establishment of specialized aeronautical laboratories in the U.S. and significant research, such as the Fitts and Jones study on control knob configurations. Post-World War II, despite advancements, many insights into group dynamics and flight crew communication were overlooked despite advancements.
The Vietnam Conflict marked a shift towards systematic error reduction in aviation, introducing "Zero Defects" quality programs and less effective top-down management strategies. The Airline Deregulation Act (1978-1988) brought further changes, challenging maintenance departments with mergers and staff reductions, yet the approach to human factors in aviation maintenance remained largely outdated. In the 1990s, a cultural shift among U.S. carriers recognized the importance of human factors, leading to changes in management, communication, and organizational structures. Examples include Continental Airlines' introduction of 'CRM-type' training and United Airlines' restructuring of inspector roles. However, challenges remained, including active and latent errors, communication breakdowns, complacency, inadequate knowledge, distractions, lack of teamwork, and fatigue. The United Kingdom Civil Aviation Authority (CAA) identified common maintenance errors, including incorrect installation of components and electrical wiring issues, highlighting ongoing concerns about human factors in aviation maintenance.
HUMAN FACTOR ACCIDENTS
On March 20, 2001, a Lufthansa Airbus A320 almost crashed shortly after takeoff because of reversed wiring in the captain's sidestick flight control. Quick action by the co-pilot, whose sidestick was not faulty, prevented a crash. The investigation has focused on maintenance of the captain's controls carried out by Lufthansa Technik just before the flight. A problem with one of the two elevator/aileron computers (ELAC) occurred during the previous flight. An electrical pin in the connector was found to be damaged and was replaced. It has been confirmed that two pairs of pins inside the connector had accidentally been crossed during the repair. This changed the polarity in the sidestick and the respective control channels “bypassing” the control unit, which might have sensed the error and would have triggered a warning. Clues might have been seen on the electronic centralized aircraft monitor (ECAM) screen during the flight control checks, but often, pilots only check for a deflection indication, not the direction. Before the aircraft left the hangar, the mechanic performed a flight control check, but only using the first officer’s sidestick.
Alaska Airlines Flight 261, a McDonnell Douglas MD-83 aircraft, experienced a fatal accident on January 31, 2000, in the Pacific Ocean. The two pilots, three cabin crewmembers, and 83 passengers on board were killed, and the aircraft was destroyed. The subsequent investigation by the National Transportation Safety Board (NTSB) determined that inadequate maintenance led to excessive wear and catastrophic failure of a critical flight control system during flight. The probable cause was “a loss of airplane pitch control resulting from the in-flight failure of the horizontal stabilizer trim system jackscrew assembly’s acme nut threads. The thread failure was caused by excessive wear resulting from Alaska Airlines’ insufficient lubrication of the jackscrew assembly.
August 26, 1993, an Excalibur Airways Airbus 320 took off from London-Gatwick Airport (LGW). It exhibited an undemanded roll to the right on takeoff, which persisted until the aircraft landed at LGW 37 minutes later. Control of the aircraft required significant left sidestick at all times, and the flight control system was degraded by the loss of spoiler control. Technicians familiar with Boeing 757 flap change procedures lacked the knowledge required to lock out the spoilers on the Airbus correctly during the flap change work the day before the flight. Turnover to technicians on the next shift compounded the problem. No incorrect spoiler lockout procedure was mentioned since It was assumed that the 320 was like the 757. The flap change was operationally checked, but the spoiler remained locked out incorrectly and was not detected by the flight crew during standard functional checks. The lack of knowledge of Airbus procedures was the primary cause of this incident.
April 26, 2001, an Emery Worldwide Airlines DC-8-71F left main landing gear would not extend for landing. The probable cause was the failure of maintenance to install the correct hydraulic landing gear extension component and the failure of inspection to comply with post-maintenance test procedures. No injuries.
On May 25, 2002, China Airlines Flight 611 Boeing 747 broke into pieces in mid-air and crashed, killing all 225 people on board. The accident resulted from metal fatigue caused by inadequate maintenance after a previous incident.
On August 26, 2003, a Colgan Air Beech 1900D crashed just after takeoff from Hyannis, Massachusetts. Both pilots were killed. The improper replacement of the forward elevator trim cable and subsequent inadequate functional check of the maintenance performed resulted in a reversal of the elevator trim system and a loss of control in flight. Factors were the flight crew’s failure to follow the checklist procedures and the aircraft manufacturer’s erroneous depiction of the elevator trim drum in the maintenance manual. On
September 28, 2007, American Airlines Flight 1400 DC-9 experienced an in-flight engine fire during a departure climb from Lambert St. Louis International Airport (STL). During the return to STL, the nose landing gear failed to extend, and the flight crew executed a go-around, during which the crew extended the nose gear using the emergency procedure. The flight crew conducted an emergency landing, and the 2 flight crewmembers, 3 flight attendants, and 138 passengers deplaned on the runway. No occupant injuries were reported, but the airplane sustained substantial damage from the fire. American Airlines maintenance personnel used an inappropriate manual engine-start procedure, which led to the uncommanded opening of the left engine air turbine starter valve and a subsequent left engine fire.
Current Challenges and Innovations in Human Factors
In aviation maintenance, understanding the current challenges in human factors is crucial. This understanding highlights the progress made and highlights areas that require further improvement. Today, the aviation industry faces an intricate blend of new technologies, evolving procedures, and a diverse workforce. Each of these elements presents unique challenges. For instance, integrating advanced digital systems in aircraft maintenance demands higher technical proficiency and continuous learning among maintenance personnel. However, with challenges come innovations. The industry has significantly shifted towards more ergonomic tools, advanced training simulators, and comprehensive safety management systems. These innovations aim to reduce human error by enhancing the work environment, improving training methods, and fostering a safety culture. For instance, virtual reality (VR) is increasingly utilized for training purposes, offering a safe and immersive environment for technicians to hone their skills without the risks associated with on-the-job training. Moreover, airlines and maintenance organizations are investing in AI-driven predictive maintenance tools, which aid in identifying potential issues before they escalate into serious problems.
Aviation professionals need to adopt a proactive approach toward these challenges. Emphasizing continuous learning, embracing new technologies, and adapting to changing protocols are vital to mitigating risks associated with human factors in aviation maintenance. This proactive stance enhances safety and improves efficiency and reliability in maintenance operations. As we come to the end of our exploration of human factors in aviation maintenance, it's clear that this field is not just about tools and technology but about people – their skills, limitations, and the critical role they play in ensuring the safety of every flight. From the early days of rudimentary trial-and-error to today’s sophisticated, multidisciplinary approaches of today, we've seen how the understanding and management of human factors have evolved, becoming a cornerstone of aviation safety.
*Ref. FAA-H-8083-25, FAA-H-8083-30B
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