Aviation: Human Factors
Importance of Human Factors
The greatest impact in aircraft safety in the future will not come from improving the technology. Rather it will be from educating the employee to recognize and prevent human error. A review of accident related data indicates that approximately 75–80 percent of all aviation accidents are the result of human error. Of those accidents, about 12 percent are maintenance related. Although pilot/co-pilot errors tend to have immediate and highly visible effects, maintenance errors tend to be more latent and less obvious. However, they can be just as lethal.
Definitions of Human Factors
Human factors are concerned with optimizing performance … including reducing errors so that the highest level of safety is achieved and maintained. —Ron LoFaro, PhD FAA
Human factors is the study of how people interact with their environments. —FAA-H-8083-25, Pilot’s Handbook of Aeronautical Knowledge, dated 2003
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)
Our focus is on human factors as it relates to improper actions. Note, however, that human factors exist in both proper and improper actions. Since improper actions usually result in human error, we should also define that term.
Human error is the unintentional act of performing a task incorrectly that can potentially degrade the system. There are three types of human error:
1. Omission: not performing an act or task.
2. Commission: accomplishing a task incorrectly.
3. Extraneous: performing a task not authorized.
There are also four consequences of human error:
1. Little or no effect.
2. Damage to equipment/hardware.
3. Personal injury.
4. Catastrophic.
Why are human conditions, such as fatigue, complacency, and stress, so important in aviation maintenance? These conditions, along with many others, are called human factors. Human factors directly cause or contribute to many aviation accidents. It is universally agreed that 80 percent of maintenance errors involve human factors. If they are not detected, they can cause events, worker injuries, wasted time, and even accidents.
Aviation safety relies heavily on maintenance. When it is not done correctly, it contributes to a significant proportion of aviation accidents and incidents. Some examples of maintenance errors are parts installed incorrectly, missing parts, and necessary checks not being performed. In comparison with many other threats to aviation safety, the mistakes of an aviation maintenance technician (AMT) can be more difficult to detect. Often, these mistakes are present but not visible and have the potential to remain latent, affecting the safe operation of aircraft for extended periods of time.
AMTs are confronted with a set of human factors unique within aviation. They can be working in the evening or early morning hours, in confined spaces, on high platforms, and in a variety of adverse temperature/humidity conditions. The work can be physically strenuous, yet it also requires attention to detail. Because of the nature of maintenance tasks, AMTs commonly spend more time preparing for a task than actually carrying it out. Proper documentation of all maintenance work is a key element, and AMTs typically spend as much time updating maintenance logs as they do performing the work.
Human factors awareness can lead to improved quality, an environment that ensures continuing worker and aircraft safety, and a more involved and responsible work force. The reduction of even minor errors can provide measurable benefits including cost reductions, fewer missed deadlines, reduction in work related injuries, reduction of warranty claims, and reduction in more significant events that can be traced back to maintenance error. Within this chapter, the many aspects of human factors are discussed in relation to aviation maintenance. The most common human factors are introduced along with ways to mitigate the risk to stop them from developing into a problem.
What are Human Factors?
The term “human factors” has grown increasingly popular as the commercial aviation industry realizes that human error, rather than mechanical failure, underlies most aviation accidents and incidents. Human factors science or technologies are multidisciplinary fields incorporating contributions from psychology, engineering, industrial design, statistics, operations research, and anthropometry. It is a term that covers the science of understanding the properties of human capability, the application of this understanding to the design, development, and deployment of systems and services, and the art of ensuring successful application of human factor principles into the maintenance working environment.
The spectrum of human factors that can affect aviation maintenance and work performance is broad. They encompass a wide range of challenges that influence people very differently as humans do not all have the same capabilities, strengths, weaknesses, or limitations. Unfortunately, aviation maintenance tasks that do not take into account the vast amount of human limitations can result in technical error and injuries.
Elements of Human Factors
Human factors are comprised of many disciplines. This section discusses ten of those disciplines: Clinical Psychology, Experimental Psychology, Anthropometrics, Computer Science, Cognitive Science, Safety Engineering, Medical Science, Organizational Psychology, Educational Psychology, and Industrial Engineering.
The study and application of human factors is complex because there is not just one simple answer to fix or change how people are affected by certain conditions or situations. The overall goal of aviation maintenance human factors research is to identify and optimize the factors that affect human performance in maintenance and inspection. The focus initiates on the technician but extends to the entire engineering and technical organization. Research is optimized by incorporating the many disciplines that affect human factors in an effort to understand how people can work more efficiently and maintain work performance.
By understanding each of the disciplines and applying them to different situations or human behaviors, we can correctly recognize potential human factors and address them before they develop into a problem or create a chain of problems that result in an accident or incident.
Clinical Psychology
Clinical psychology includes the study and application of psychology for the purpose of understanding, preventing, and relieving psychologically-based distress or dysfunction and to promote subjective well-being and personal development. It focuses on the mental well-being of the individual. Clinical psychology can help individuals deal with stress, coping mechanisms for adverse situations, poor self-image, and accepting criticism from coworkers.
Experimental Psychology
Experimental psychology includes the study of a variety of basic behavioral processes, often in a laboratory environment. These processes may include learning, sensation, perception, human performance, motivation, memory, language, thinking, and communication, as well as the physiological processes underlying behaviors, such as eating, reading, and problem solving. In an effort to test the efficiency of work policies and procedures, experimental studies help measure performance, productivity, and deficiencies.
Anthropometry
Anthropometry is the study of the dimensions and abilities of the human body. This is essential to aviation maintenance due to the environment and spaces that AMTs have to work with. For example, a man who is 6 feet 3 inches and weighs 230 pounds may be required to fit into a small crawl space of an aircraft to conduct a repair. Another example is the size and weight of equipment and tools. Men and women are generally on two different spectrums of height and weight. Although both are equally capable of completing the same task with a high level of proficiency, someone who is smaller may be able to perform more efficiently with tools and equipment tailored to his or her size. In other words, one size does not fit all and the term “average person” does not apply when employing such a diverse group of people.
Computer Science
The technical definition for computer science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems. Yet how this relates to aviation maintenance is simpler to explain. As mentioned earlier, AMTs spend as much time documenting repairs as they do performing them. It is important that they have computer work stations that are comfortable and reliable. Software programs and computer-based test equipment should be easy to learn and use, and not intended only for those with a high levels of computer literacy.
Cognitive Science
Cognitive science is the interdisciplinary scientific study of minds as information processors. It includes research on how information is processed (in faculties such as perception, language, reasoning, and emotion), represented, and transformed in a nervous system or machine (e.g., computer). It spans many levels of analysis from low-level learning and decision mechanisms to high-level logic and planning. AMTs must possess a great ability to problem solve quickly and efficiently. They are constantly required to troubleshoot situations and quickly react to them. This can be a vicious cycle creating an enormous amount of stress. The discipline of cognitive science helps us understand how to better assist AMTs during situations that create high levels of stress so that their mental process does not get interrupted and affect their ability to work.
Safety Engineering
Safety engineering ensures that a life-critical system behaves as needed even when the component fails. Ideally, safety engineers take an early design of a system, analyze it to find what faults can occur, and then propose safety requirements in design specifications up front and changes to existing systems to make the system safer. Safety cannot be stressed enough when it comes to aviation maintenance, and everyone deserves to work in a safe environment. Safety engineering plays a big role in the design of aviation maintenance facilities, storage containers for toxic materials, equipment used for heavy lifting, and floor designs to ensure no one slips, trips, or falls. In industrial work environments, the guidelines of the Occupational Safety and Health Administration (OSHA) are important.
Medical Science
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness. Disposition and physical well-being are very important and directly correlated to human factors. Just like people come in many shapes and sizes, they also have very different reactions to situations due to body physiology, physical structures, and biomechanics.
Organizational Psychology
Organizational psychologists are concerned with relations between people and work. Their interests include organizational structure and organizational change, workers’ productivity and job satisfaction, consumer behavior, and the selection, placement, training, and development of personnel. Understanding organizational psychology helps aviation maintenance supervisors learn about the points listed below that, if exercised, can enhance the work environment and productivity.
Educational Psychology
Educational psychologists study how people learn and design the methods and materials used to educate people of all ages. Everyone learns differently and at a different pace. Supervisors should design blocks of instruction that relate to a wide variety of learning styles.
Industrial Engineering
Industrial engineering is the organized approach to the study of work. It is important for supervisors to set reasonable work standards that can be met and exceeded. Unrealistic work standards create unnecessary stressors that cause mistakes. It is also beneficial to have an efficient facility layout so that there is room to work. Clean and uncluttered environments enhance work performance. Another aspect of industrial engineering that helps in the understanding of human factors is the statistical analysis of work performance. Concrete data of work performance, whether good or bad, can show the contributing factors that may have been present when the work was done.
History of Human Factors
Around 1487, Leonardo da Vinci began research in the area of anthropometrics. The Vitruvian Man, one of his most famous drawings, can be described as one of the earliest sources presenting guidelines for anthropometry. Around the same time, he also began to study the flight of birds. He grasped that humans are too heavy and not strong enough to fly using wings simply attached to the arms. Therefore, he sketched a device in which the aviator lies down on a plank and works two large, membranous wings using hand levers, foot pedals, and a system of pulleys. Today, anthropometry plays a considerable role in the fields of computer design, design for access and maintainability, simplicity of instructions, and ergonomic issues.
In the early 1900s, industrial engineers Frank and Lillian Gilbreth were trying to reduce human error in medicine. They developed the concept of using call backs when communicating in the operating room. For example, the doctor says “scalpel” and the nurse repeats “scalpel” and then hands it to the doctor. That is called the challenge-response system. Speaking out loud reinforces what tool is needed and provides the doctor with an opportunity to correct his/herself if it is not the necessary tool. This same verbal protocol is used in aviation today. Pilots are required to read back instructions or clearances given by air traffic control (ATC) to ensure that the pilot receives the correct instructions and gives ATC an opportunity to correct if the information is wrong. Frank and Lillian Gilbreth also are known for their research on fatigue.
Also in the early 1900s, Orville and Wilbur Wright were the first to fly a powered aircraft and also pioneered many human factors considerations. While others were trying to develop aircraft with a high degree of aerodynamic stability, the Wrights intentionally designed unstable aircraft with cerebralized control modeled after the flight of birds. Between 1901 and 1903, the brothers worked with large gliders at Kill Devil Hills, near Kitty Hawk, North Carolina, to develop the first practical human interactive controls for aircraft pitch, roll, and yaw. On December 17, 1903, they made four controlled powered flights over the dunes at Kitty Hawk with their Wright Flyer. They later developed practical in-flight control of engine power, plus an angle of attack sensor and stick pusher that reduced pilot workload. The brothers’ flight demonstrations in the United States and Europe during 1908-1909 awakened the world to the new age of controlled flight. Orville was the first aviator to use a seat belt and also introduced a rudder boost/ trim control that gave the pilot greater control authority. The Wrights’ flight training school in Dayton, Ohio included a flight simulator of their own design. The Wrights patented their practical airplane and flight control concepts, many of which are still in use today.
Prior to World War I, the only test of human to machine compatibility was that of trial and error. If the human functioned with the machine, he was accepted, if not he was rejected. There was a significant change in the concern for humans during the American Civil War. The U.S. Patent Office was concerned about whether the mass-produced uniforms and new weapons could be used effectively by the infantry men.
Evolution of Maintenance Human Factors
With the onset of World War I (1914–1918), more sophisticated equipment was being developed and the inability of personnel to use such systems led to an increased interest in human capability. Up to this point, the focus of aviation psychology was on the pilot, but as time progressed, the focus shifted onto the aircraft. Of particular concern was the design of the controls and displays, the effects of altitude, and environmental factors on the pilot. The war also brought on the need for aeromedical research and the need for testing and measurement methods. By the end of World War I, two aeronautical labs were established, one at Brooks Air Force Base, Texas, and the other at Wright Field outside of Dayton, Ohio.
Another significant development was in the civilian sector, where the effects of illumination on worker productivity were examined. This led to the identification of the Hawthorne Effect, which suggested that motivational factors could significantly influence human performance.
With the onset of World War II (1939–1945), it was becoming increasingly harder to match individuals to pre-existing jobs. Now the design of equipment had to take into account human limitations and take advantage of human capabilities. This change took time as there was a lot of research still to be done to determine the human capabilities and limitations. An example of this is the 1947 study done by Fitts and Jones on the most effective configuration of control knobs to be used in aircraft flight decks. Much of this research transitioned into other equipment with the aim of making the controls and displays easier for the operators to use.
Unfortunately, all the “lessons learned” in the WWII studies of group dynamics, and flight crew communication were seemingly forgotten after the war. Post WWII aircrew studies continued to focus primarily on flight crews, especially pilot selection, simulator training, and cockpit layout and design.
Subsequent studies of the technician focused on his or her individual competency, and included equipment design (ergonomics). The Vietnam Conflict brought the quest for greater safety, and with that, came a systematic approach for error reduction. This increased attention brought both good and bad changes. It led to the “Zero Defects” quality programs in maintenance and manufacturing. Generally, this had a positive effect. However, it also led to “crackdown programs” which were one-way communication from management (the infamous “my way or the highway” approach). This concept is more dictatorial than democratic, and typically had a long-term negative effect on the company. This “crackdown” approach for behavior control is based upon fear and punishment, which creates a problem. Errors are driven into hiding, and then become apparent later, usually at a more critical time (“Murphy’s Law”). Additional attempts to develop “foolproof” equipment designs were added to the zero-defect manufacturing goal and began to find recognition in the maintenance world as well. Subsequent efforts focused on effects of positive rather than negative motivators. The results of this effort were a reversal of the “crackdown” method, and motivation due to increased morale often improved maintenance safety performance. Studies have shown that motivation resulting from negative sources seldom achieved the same effect. This led to a “Participative Management” style recognized by some U.S. industry and a few airlines, but did not reach maintenance operations until much later.
The Airline Deregulation (1978 –1988) effort had a profound effect upon the aviation community. Prior to 1978, the airline industry was regulated by the Civil Aeronautics Act of 1938. This resulted in peaceful markets, stable routes, and consistent air fares. However, there was a downside consisting of two major problems: wasteful management practices and excessively high wages compared to other comparable skilled-labor industries. The Airline Deregulation Act brought in competitive business practices, with routes and fares controlled by their profitability. This led to a new style of airline management in which a CEO was more of a business person and less knowledgeable of aviation. Existing airlines developed new routes and added new kinds of service and style. Start-up airlines brought other innovative ideas. The numerous mergers and acquisitions added an increasing pressure to focus on the financial bottom line. Doing more with less became the byline. In the 1980s, maintenance departments were not immune to the pressures of mergers and staff reductions. However, fleets were extremely reliable at that time, and significant savings were aided by a reduction in number of maintenance technicians. Other new ways of conducting business included leasing of aircraft and outsourcing of maintenance. A result of deregulation was change for the maintenance programs (both personnel and departmental) and the pressure to produce and adjust. The problem, however, was that human factors for aviation maintenance is still stuck in the 1960s model.
A detailed review of aviation literature published between 1976 and 1987 had very little to say about maintenance. Out of 50 published articles, only 15 even mention maintenance. Most of these articles deal with ergonomics, one article examines military engine design to “solider proof” the maintenance duties, and one U.S. Navy article advocated more management control.
As human factors awareness progressed, a “culture change” occurred in U.S. carriers in the 1990s. Management behavior began to change; there were practical applications of systems thinking; organization structure was revised; and new strategy, policy, and values emerged. Virtually all of these involved communication and collaboration. One example is in 1991, when Continental Airlines began “CRM type” training in maintenance. They saw the importance of improving communication, teamwork, and participative decision making. A second example is when United Airlines instituted a change in organization and the job of design of inspectors. They remained more accessible during heavy maintenance and overhaul and stayed in closer communication with mechanics during normal repairs. This resulted in fewer turnbacks and higher quality. A third example is when Southwest Airlines created and sustained a strong and clear organizational structure led by the CEO. This resulted in open and positive communication between the maintenance and other departments. A final example is when TWA instituted a new program to improve communication between the maintenance trade union and maintenance management. This resulted in improved quality.
The Pear Model
There are many concepts related to the science and practice of human factors. However, from a practical standpoint, it is most helpful to have a unified view, or a model of the things we should be concerned about when considering aviation maintenance human factors. For more than a decade, the term “PEAR” has been used as a memory jogger, or mnemonic, to characterize human factors in aviation maintenance. The PEAR mode prompts recall of the four important considerations for human factors programs, which are listed below.
• People who do the job.
• Environment in which they work.
• Actions they perform.
• Resources necessary to complete the job.
People
Aviation maintenance human factors programs focus on the people who perform the work and address physical, physiological, psychological, and psychosocial factors. The programs must focus on individuals, their physical capabilities, and the factors that affect them. They also should consider their mental state, cognitive capacity, and conditions that may affect their interaction with others. In most cases, human factors programs are designed around the people in the company’s existing workforce. You cannot apply identical strength, size, endurance, experience, motivation, and certification standards equally to all employees. The company must match the physical characteristics of each person to the tasks each performs.
The company must consider factors like each person’s size, strength, age, eyesight, and more to ensure each person is physically capable of performing all the tasks making up the job. A good human factors program considers the limitations of humans and designs the job accordingly. An important element when incorporating human factors into job design is planned rest breaks. People can suffer physical and mental fatigue under many work conditions. Adequate breaks and rest periods ensure the strain of the task does not overload their capabilities. Another “People” consideration, which also is related to “E” for “Environment,” is ensuring there is proper lighting for the task, especially for older workers. Annual vision testing and hearing exams are excellent proactive interventions to ensure optimal human physical performance.
Attention to the individual does not stop at physical abilities. A good human factors program must address physiological and psychological factors that affect performance. Companies should do their best to foster good physical and mental health. Offering educational programs on health and fitness is one way to encourage good health. Many companies have reduced sick leave and increased productivity by making healthy meals, snacks, and drinks available to their employees. Companies also should have programs to address issues associated with chemical dependence, including tobacco and alcohol. Another “People” issue involves teamwork and communication. Safe and efficient companies find ways to foster communication and cooperation among workers, managers, and owners. For example, workers should be rewarded for finding ways to improve the system, eliminate waste, and help ensure continuing safety.
Environment
There are at least two environments in aviation maintenance. There is the physical workplace on the ramp, in the hangar, or in the shop. In addition, there is the organizational environment that exists within the company. A human factors program must pay attention to both environments.
The physical environment is obvious. It includes ranges of temperature, humidity, lighting, noise control, cleanliness, and workplace design. Companies must acknowledge these conditions and cooperate with the workforce to either accommodate or change the physical environment. It takes a corporate commitment to address the physical environment. This topic overlaps with the “Resources” component of PEAR when it comes to providing portable heaters, coolers, lighting, clothing, and good workplace and task design.
Organizational. The second, less tangible, environment is the organizational one. The important factors in an organizational environment are typically related to cooperation, communication, shared values, mutual respect, and the culture of the company. An excellent organizational environment is promoted with leadership, communication, and shared goals associated with safety, profitability, and other key factors. The best companies guide and support their people and foster a culture of safety. A safe culture is one where there is a shared value and attitude toward safety. In a safe culture, each person understands their individual role is contributing to overall mission safety.
Actions
Successful human factors programs carefully analyze all the actions people must perform to complete a job efficiently and safely. Job task analysis (JTA) is the standard human factors approach to identify the knowledge, skills, and attitudes necessary to perform each task in a given job. The JTA helps identify what instructions, tools, and other resources are necessary. Adherence to the JTA helps ensure each worker is properly trained and each workplace has the necessary equipment and other resources to perform the job. Many regulatory authorities require that the JTA serve as the basis for the company’s general maintenance manual and training plan. Many human factors challenges associated with use of job cards and technical documentation fall under “Actions.” Clearly understandable documentation of actions ensures instructions and checklists are correct and useable.
Resources
The final PEAR letter is “R” for “Resources.” It is sometimes difficult to separate resources from the other elements of PEAR. In general, the characteristics of the people, environment, and actions dictate the resources. Many resources are tangible, such as lifts, tools, test equipment, computers, technical manuals, and so forth. Other resources are less tangible. Examples include the number and qualifications of staff to complete a job, the amount of time allocated, and the level of communication among the crew, supervisors, vendors, and others. Resources should be viewed (and defined) from a broad perspective. A resource is anything a technician (or anyone else) needs to get the job done. For example, protective clothing is a resource. A mobile phone can be a resource. Rivets can be resources. What is important to the “Resource” element in PEAR is focusing on identifying the need for additional resources.
Another major human factors tool for use in investigation of maintenance problems is the Boeing developed Maintenance Error Decision Aid (MEDA). This is based on the idea that errors result from a series of factors or incidents. The goal of using MEDA is to investigate errors, understand root causes, and prevent accidents, instead of simply placing blame on the maintenance personnel for the errors. Traditional efforts to investigate errors are often designed to identify the employee who made the error. In this situation, the actual factors that contributed to the errors or accident remain unchanged, and the mistake is likely to recur. In an effort to break this “blame and train” cycle, MEDA investigators learn to look for the factors that contributed to the error, instead of the employee who made the error. The MEDA concept is based on the following three principles:
• Positive employee intent (In other words, maintenance technicians want to do the best job possible and do not make intentional errors.)
• Contribution of multiple factors (There is often a series of factors that contribute to an error.)
• Manageability of errors (Most of the factors that contribute to an error can be managed.)
SHEL Model
The “SHEL” model is another concept for investigating and evaluating maintenance errors. As with other human factors tools, its goal is to determine not only what the problem is, but where and why it exists. SHEL was initiated by Professor Elwyn Edwards (Professor Emeritus, Aston University, Birmingham, U.K.) in 1972. It was later modified slightly by the late Capt. Frank Hawkins, a Human Factors consultant to KLM, in 1975. The acronym SHEL represents:
• Software
• Hardware
• Environment
• Liveware
The model examines interaction with each of the four SHEL components, and does not consider interactions not involving human factors. The term “software” is not referring to the common use of the term as applied to computer programs. Instead it includes a broader view of manual layout, checklist layout, symbology, language (both technical and nontechnical), and computer programs. Hardware includes such things as the location of components, the accessibility of components and tooling. Environment takes temperature, humidity, sound, light, and time of day factors into account. Liveware relates technician interaction with other people, both on the job and off. These include managers, peers, family, friends, and self.
No discussion of human factors is complete without reference to James Reasons’ Model of Accident Causation. This diagram, which was introduced in 1990, and revised by Dr. Reason in 1993, is often referred to as the Swiss cheese model and shows how various “holes” in different systems must be aligned in order for an error to occur. Only when the holes are all aligned can the incident take place.
Human Error
Human error is defined as a human action with unintended consequences. When you couple error with aviation maintenance and the negative consequences that it produces, it becomes extremely troublesome. Training, risk assessments, safety inspections, etc., should not be restricted to an attempt to avoid errors but rather to make them visible and identify them before they produce damaging and regrettable consequences. Simply put, human error is not avoidable but it is manageable.
Types of Errors
An unintentional error is an accidental wandering or deviation from accuracy. This can include an error in your action (a slip), opinion, or judgment caused by poor reasoning, carelessness, or insufficient knowledge (a mistake). For example, an AMT reads the torque values from a job card and unintentionally transposed the number 26 to 62. He or she did not mean to make that error but unknowingly and unintentionally did. An example of an unintentional mistake would be selecting the wrong work card to conduct a specific repair or task. Again, it is not an intentional mistake but a mistake nonetheless.
Intentional. In aviation maintenance, an intentional error should really be considered a violation. If someone knowingly or intentionally chooses to do something wrong, it is a violation, which means that one has purposely deviated from safe practices, procedures, standards, or regulations.
Active and Latent. An active error is the specific individual activity that is an obvious event. A latent error is the company issues that lead up to the event. For example, an AMT climbs up a ladder to do a repair knowing that the ladder is broken. In this example, the active error was falling from the ladder. The latent error was the broken ladder that someone should have replaced.
The “Dirty Dozen”
Due to a large number of maintenance-related aviation accidents and incidents that occurred in the late 1980s and early 1990s, Transport Canada identified twelve human factors that degrade people’s ability to perform effectively and safely, which could lead to maintenance errors. These twelve factors, known as the “dirty dozen,” were eventually adopted by the aviation industry as a straightforward means to discuss human error in maintenance. It is important to know the dirty dozen, how to recognize their symptoms, and most importantly, know how to avoid or contain errors produced by the dirty dozen. Understanding the interaction between organizational, work group, and individual factors that may lead to errors and accidents, AMTs can learn to prevent or manage them proactively in the future.
Lack of Communication
Lack of communication is a key human factor that can result in suboptimal, incorrect, or faulty maintenance. Communication occurs between the AMT and many people (i.e., management, pilots, parts suppliers, aircraft servicers). Each exchange holds the potential for misunderstanding or omission. But communication between AMTs may be the most important of all. Lack of communication between technicians could lead to a maintenance error and result in an aircraft accident. This is especially true during procedures where more than one technician performs the work on the aircraft. It is critical that accurate, complete information be exchanged to ensure that all work is completed without any step being omitted. Knowledge and speculation about a task must be clarified and not confused. Each step of the maintenance procedure must be performed according to approved instructions as though only a single technician did the work.
Complacency
Complacency is a human factor in aviation maintenance that typically develops over time. As a technician gains knowledge and experience, a sense of self satisfaction and false confidence may occur. A repetitive task, especially an inspection item, may be overlooked or skipped because the technician has performed the task a number of times without ever finding a fault. The false assumption might be made that inspection of the item is not important. However, even if rare, a fault may exist. The consequences of the fault not being detected and corrected could cause an incident or accident. Routine tasks performed over and over allow time for the technician’s mind to wander, which may also result in a required task not being performed.
Lack of Knowledge
A lack of knowledge when performing aircraft maintenance can result in a faulty repair that can have catastrophic results. Differences in technology from aircraft to aircraft and updates to technology and procedures on a single aircraft also make it challenging to obtain the knowledge required to perform airworthy maintenance.
Distraction
A distraction while performing maintenance on an aircraft may disrupt the procedure. When work resumes, it is possible that the technician skips over a detail that needs attention. It is estimated that 15 percent of maintenance related errors are caused by distractions.
Lack of Teamwork
A lack of teamwork may also contribute to errors in aircraft maintenance. Closely related to the need for communication, teamwork is required in aviation maintenance in many instances. Sharing of knowledge between technicians, coordinating maintenance functions, turning work over from shift to shift, and working with flight personnel to troubleshoot and test aircraft are all are executed better in an atmosphere of teamwork. Often associated with improved safety in the workplace, teamwork involves everyone understanding and agreeing on actions to be taken. A gear swing or other operational check involves all the members of a team working together. Multiple technicians contribute to the effort to ensure a single outcome. They communicate and look out for one another as they do the job. A consensus is formed that the item is airworthy or not airworthy.
Fatigue
Fatigue is a major human factor that has contributed to many maintenance errors resulting in accidents. Fatigue can be mental or physical in nature. Emotional fatigue also exists and affects mental and physical performance. A person is said to be fatigued when a reduction or impairment in any of the following occurs: cognitive ability, decision-making, reaction time, coordination, speed, strength, or balance. Fatigue reduces alertness and often reduces a person’s ability to focus on the task being performed.
Lack of Resources
A lack of resources can interfere with a person’s ability to complete a task because of a lack of supplies and support. Low quality products also affect one’s ability to complete a task. Aviation maintenance demands proper tools and parts to maintain a fleet of aircraft. Any lack of resources to safely carry out a maintenance task can cause both non-fatal and fatal accidents. For example, if an aircraft is dispatched without a functioning system that is typically nonessential for flight but suddenly becomes needed, this could create a problem.
Pressure
Aviation maintenance tasks require individuals to perform in an environment with constant pressure to do things better and faster without making mistakes and letting things fall through the cracks. Unfortunately, these types of job pressures can affect the capabilities of maintenance workers to get the job done right. Airlines have strict financial guidelines, as well as tight flight schedules, that pressure mechanics to identify and repair mechanical problems quickly so that the airline industry can keep moving. Most important, aircraft mechanics are responsible for the overall safety of everyone who uses flying as a mode of transportation.
Lack of Assertiveness
Assertiveness is the ability to express your feelings, opinions, beliefs, and needs in a positive, productive manner and should not be confused with being aggressive. It is important for AMTs to be assertive in issues relating to aviation repair rather than choosing not to or not being allowed to voice their concerns and opinions. Not being assertive could ultimately cost people their lives.
Stress
Aviation maintenance is a stressful task due to many factors. Aircraft must be functional and flying in order for airlines to make money, which means that maintenance must be done within a short timeframe to avoid flight delays and cancellations. Fast-paced technology that is always changing can add stress to technicians. This demands that AMTs stay trained on the latest equipment. Other stressors include working in dark, tight spaces, lack of resources to get the repair done correctly, and long hours. The ultimate stress of aviation maintenance is knowing that the work they do, if not done correctly, could result in tragedy.
Lack of Awareness
Lack of awareness is defined as a failure to recognize all the consequences of an action or lack of foresight. In aviation maintenance, it is not unusual to perform the same maintenance tasks repeatedly. After completing the same task multiple times, it is easy for technicians to become less vigilant and develop a lack of awareness of what they are doing and what is around them. Each time a task is completed it must be treated as if it were the first time.
Norms
Norms is short for “normal,” or the way things are normally done. They are unwritten rules that are followed or tolerated by most organizations. Negative norms can detract from the established safety standard and cause an accident to occur. Norms are usually developed to solve problems that have ambiguous solutions. When faced with an ambiguous situation, an individual may use another’s behavior as a frame of reference around which to form his or her own reactions. As this process continues, group norms develop and stabilize. Newcomers to the situation are then accepted into the group based on adherence to norms. Very rarely do newcomers initiate change in a group with established norms.
Example of Common Maintenance Errors
In an effort to identify the most frequently occurring maintenance discrepancies, the United Kingdom Civil Aviation Authority (CAA) conducted in-depth studies of maintenance sites on aviation maintenance operations. The following list is what they found to be the most common occurring maintenance errors.
1. Incorrect installation of components.
2. Fitting of wrong parts.
3. Electrical wiring discrepancies to include crossing connections.
4. Forgotten tools and parts.
5. Failure to lubricate.
6. Failure to secure access panels, fairings, or cowlings.
7. Fuel or oil caps and fuel panels not secured.
8. Failure to remove lock pins.
