Text-only reference. Published from the recorded official FAA General Chapter 14 PDF. Diagrams, photographs, and figure artwork are not reproduced here; use the official FAA PDF for those materials.
14-25 THE DIRTY DOZEN Twelve human factors for aircraft maintenance proficiency Lack of Teamwork Fatigue Lack of Resources
Pressure
Lack of Assertiveness
Stress
Lack of Awareness Norms Complacency Lack of Knowledge Distraction Lack of Communication MITIGATING THE RISK Ensure that the pressure is not self-induced. Ask for extra help if time is an issue. Communicate if you think you will need more time to complete a repair rather than rush through it. Pressure to get things repaired is always present in aviation. Maintainers must not let the pressures of time constraints get in the way with safely finishing a repair. Physiological Stressors Physiological stressors include fatigue, poor physical condition, hunger, and disease. • Poor physical condition—trying to work when ill or not feeling well can force the body to use more energy fighting the illness, leaving less energy to perform vital tasks.
• Proper meals—not eating enough, or eating foods lacking the proper nutrition, can result in low energy and induce symptoms like headaches and shaking. • Lack of sleep—a fatigued AMT is unable to perform to standard for long periods of time and can become sloppy with repairs and make significant mistakes. • Conflicting shift schedules—the effect of changing sleep patterns on the body’s circadian cycle can lead to a degradation of performance. 14-26 THE DIRTY DOZEN Twelve human factors for aircraft maintenance proficiency Lack of Teamwork Fatigue Lack of Resources
Pressure
Lack of Assertiveness
Stress
Lack of Awareness Norms Complacency Lack of Knowledge Distraction Lack of Communication MITIGATING THE RISK Provide clear feedback when a risk or danger is perceived. Allow co-workers to give their opinions and always accept corrective criticisms. Never compromise your standards. Lack of assertiveness in failing to alert others when something does not seem right can result in many fatal accidents. Do not let something that you know is wrong continue by ignoring it. People cope with stress in many different ways. Specialists say that the first step is to identify stressors and the symptoms that occur after exposure to those stressors. Other recommendations involve development or maintenance of a healthy lifestyle with adequate rest and exercise, a healthy diet, limited consumption of alcoholic drinks, and avoidance of tobacco products.
Lack of Awareness Lack of awareness is defined as a failure to recognize all the consequences of an action or lack of foresight. [Figure 14-30] 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. [Figure 14-31] 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 their 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. Some norms are unsafe in that they are non-productive or detract from the productivity of the group. Taking shortcuts in 14-27 THE DIRTY DOZEN Twelve human factors for aircraft maintenance proficiency Lack of Teamwork Fatigue Lack of Resources
Pressure
Lack of Assertiveness
Stress
Lack of Awareness Norms Complacency Lack of Knowledge Distraction Lack of Communication MITIGATING THE RISK Take time off or a short break if you are feeling stressed. Healthy eating, exercise, and a sufficient amount of rest can reduce stress levels. Discuss with a co-worker and ask them to monitor your work. Stress is the subconscious response to the demands placed on a person. aircraft maintenance, working from memory, or not following procedures are examples of unsafe norms. Newcomers are better able to identify these unsafe norms than long-standing members of the group. On the other hand, the newcomer’s credibility depends on their assimilation into the group. The newcomer’s assimilation, however, depends on adherence to the group norms. Everyone should be aware of the perceptiveness of newcomers in identifying unhealthy norms and develop a positive attitude toward the possibility that norms may need to be changed. Finally, as newcomers become assimilated into the group structure, they build credibility with others. Once this has been done, a relative newcomer may begin to institute change within the group. Unfortunately, such actions are often difficult to do and rely heavily on the group’s perception of the newcomer’s credibility.
Norms have been identified as one of the dirty dozen in aviation maintenance and a great deal of anecdotal evidence points to the use of unsafe norms on the line. The effect of unsafe norms may range from the relatively benign, such as determining accepted meeting times, to the inherently unsafe, such as signing off on incomplete maintenance tasks. Any behavior commonly accepted by the group, whether as a standard operating procedure (SOP) or not, can be a norm. Supervisors need to ensure that everyone adheres to the same standards and that unsafe norms are not tolerated. AMTs should pride themselves on following procedure, rather than unsafe norms that may have been adopted as regular practice.
14-28 THE DIRTY DOZEN Twelve human factors for aircraft maintenance proficiency Lack of Teamwork Fatigue Lack of Resources
Pressure
Lack of Assertiveness
Stress
Lack of Awareness Norms Complacency Lack of Knowledge Distraction Lack of Communication MITIGATING THE RISK Check to see if what you are working on conflicts with an existing modification or repair. Even if you are highly proficient in a task, always have someone check your work. Always ask co-workers to check your work. After completing the same tasks multiple times, maintainers can develop a lack of awareness for what is around them. They tend to lack common sense and vigilance because they have completed the same task so many times. 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. [Figure 14-32] 4. Forgotten tools and parts. 5. Failure to lubricate. [Figure 14-33] 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. [Figure 14-34] All of the maintenance discrepancies listed above can be avoided if the proper procedures are followed on the job card that is being used. [Figure 14-35] Regardless of how many times the task has been completed, each time you 14-29 THE DIRTY DOZEN Twelve human factors for aircraft maintenance proficiency Lack of Teamwork Fatigue Lack of Resources
Pressure
Lack of Assertiveness
Stress
Lack of Awareness Norms Complacency Lack of Knowledge Distraction Lack of Communication MITIGATING THE RISK Ensure that everyone follows the same standard. The easiest way of accomplishing something may not be the standard. Be aware that just because it seems normal does not make it correct. Norms is short for “normal,” or the way things are normally done. They are unwritten rules that are followed or tolerated by most of the organization. Negative norms can detract from the established safety standard and cause an accident to occur. pick up a job card, treat it like it is the first time you have ever completed the task, and complete it with diligence and complete accuracy.
Historically, twenty percent of all accidents are caused by a machine failure, and eighty percent by human factors. [Figure 14-36] Originally focusing on the pilot community, human factors awareness has now spread into the training sphere of maintenance technicians. An in-depth review of an aviation incident reveals time and again that a series of human errors (known also as a chain of events) was allowed to build until the accident occurred. If the chain of events is broken at the maintenance level, the likelihood of the accident occurring can be drastically decreased. Figure 14-37 is a list of maintenance-related incidents/accidents and their causes.
It is easy to see how many of the “Dirty Dozen” contributed to the causes or were considered contributing factors.
Where to Get Information
Following is a list of websites and references that are good sources of information on human factors.