U.S . Department of Transportation Federal Aviation Administration Advisory Circular Subject: Maintainer Fatigue Risk Management Date: 12/2/16 AC No: 120-115 Initiated by: AFS-300 Change:
1 PURPOSE. This advisory circular (AC):
1. Describes the basic concepts of human fatigue and how it relates to safety for aviation maintenance organizations and individual maintainers.
2. Provides information on Fatigue Risk Management (FRM) in terms of fatigue hazards and mitigation strategies specific to aviation maintainers.
3. Describes the benefits of implementing FRM methods within aviation maintenance organizations.
4. Identifies methods for integrating FRM within a Safety Management System (SMS) (if applicable).
Note: This AC is informational and is not mandatory. It does not constitute a regulation.
2 RELATED READING MATERIAL. Additional information about this topic can be found in the current editions of the following documents:
• AC 117-2, Fatigue Education and Awareness Training Program.
• AC 117-3, Fitness for Duty.
• AC 120-100, Basics of Aviation Fatigue.
• AC 120-103, Fatigue Risk Management Systems for Aviation Safety.
• The Federal Aviation Administration (FAA) Maintenance Fatigue website, https://www.faa.gov/about/initiatives/maintenance_hf/fatigue.
• International Civil Aviation Organization (ICAO). Fatigue Risk Management Systems: Implementation Guide for Operators. 2011.
• Avers, K., and W.B. Johnson. “A Review of Federal Aviation Administration Fatigue Research: Transitioning Scientific Results to the Aviation Industry.” The Journal of Aviation Psychology and Applied Human Factors 1.2 (2011): 87-88.
• Hobbs, A., K.B. Avers, J.J. Hiles. Fatigue Risk Management in Aviation Maintenance: Current Best Practices and Potential Future Countermeasures.
Technical Report DOT/FAA/AM-11/10. Washington, D.C.: Federal Aviation Administration, Office of Aerospace Medicine, 2011.
2 Note: This document summarizes and does not reproduce the scientific references in the documents listed above. This list is not all-inclusive.
3 BACKGROUND. We are a nation of sleep-deprived workers. It is estimated that adults attempt to function on 1 to 1.5 hours less sleep than the generally recommended 8 hours per night. Human fatigue costs U.S. businesses over $136 billion in lost productivity each year. The losses do not include cost estimates associated with workplace injury, insurance claims, or rework. Of concern to Aviation Safety (AVS) is the finding that maintenance personnel tend to get 3 hours less sleep per night than is recommended. That is a sleep debt twice the national average. Sleepiness and fatigue associated with sleep debt is cumulative. This means that losing even an hour of sleep every other night over the course of a week will produce conditions that negatively affect performance. Some of the most critical performance errors associated with worker fatigue include, but are not limited to:
• Impaired judgment and decision making;
• Impaired communication skills;
• Decreased attention span and ability to recall information;
• Irritability;
• Slower reaction times; and
• Increased risk-taking.
3.1 Critical Issue. Personnel fatigue was first identified as a critical issue in aviation maintenance by the National Transportation Safety Board (NTSB) in 1996, stemming from the ValuJet accident in Florida. Since then, it continued to gain attention as a maintenance safety risk:
1. In 2000, an FAA field study that collected 50,000 hours of ActiGraph data from maintenance personnel across multiple organizations found that maintainers were typically getting about 5 hours of sleep;
2. In 2006, an FAA survey of international human factors (HF) programs in maintenance organizations revealed that over 80 percent of those responding indicated that human fatigue was an issue;
3. In 2008, an FAA conference on human fatigue revealed that scientists, regulators, company management, and labor representatives all agreed that human fatigue poses a safety hazard in the aviation maintenance industry and that individuals, and government and civilian organizations, need to take appropriate action; and
4. In 2010, the FAA Administrator publicly committed to review all aspects of FAA regulations that address human fatigue.
4 INTRODUCTION. The importance of managing human fatigue risk in the aviation maintenance industry cannot be overemphasized. This AC will provide maintenance organizations and the individual maintainer with the information necessary to detect
3 fatigue symptoms, to identify fatigue hazards, to assess the associated safety and health risks, and to implement fatigue countermeasures. It will provide the necessary information to determine acceptable approaches/tools for mitigating fatigue-related risks and to create science-based business practices for managing fatigue risks.
4.1 Causes of Human Fatigue. The causes of fatigue in aviation maintenance are shared by the employer and by the individual maintainer. Causes of fatigue can be categorized related to the most responsible entity.
4.1.1 Factors primarily under the control of the individual maintainer may include:
1. Amount of sleep in previous 72 hours;
2. Quality of sleep;
3. Continuous hours awake;
4. Emotional, physical, or medical issues that interfere with restorative sleep (i.e., sleep quality); and
5. Underutilizing and overlooking the importance of sleep opportunities.
4.1.2 Factors primarily under the control of the employer may include:
1. The start time and duration of the shift;
2. Work and work/life schedule changes;
3. Suboptimal rotation of shift schedules;
4. Not having a routine work schedule;
5. Work schedules that overlap with time periods when the body is biologically programmed to sleep (known as circadian rhythm);
6. Working too long at the same task; and
7. Working under suboptimal conditions, such as low staffing levels, insufficient breaks, poor lighting, noise, extreme temperatures, and so on.
4.2 Fatigue Hazards. Human fatigue is a safety hazard in performing any and all maintenance tasks because, at a minimum, it can impair judgment, make it difficult to get and stay focused, cause forgetfulness, affect mood, and reduce motivation. Fatigue hazards not only affect the safety of the flying public, but also pose risks to the safety and health of the maintainer, the maintenance organization, and the industry as a whole.
4.2.1 Safety Risk. Fatigue affects worker safety on and off the job. Fatigue in the workplace can be a serious safety hazard and is repeatedly linked to errors that lead to incidents and accidents.
• The relative risk of work-related injuries increases approximately 15 percent on afternoon shifts and 28 percent on night shifts, as compared to morning shifts.
• A large U.S. air carrier found that injury risk increases dramatically after a worker has been on the job for 8 hours. Workers on a 12-hour shift had more than double the risk of suffering an injury than workers on an 8-hour shift. Workers on a 16-hour shift had more than four times the risk of suffering an injury than workers on an 8-hour shift.
• The NTSB estimates that fatigue causes at least 100,000 crashes, 40,000 injuries, and 1,550 deaths on U.S. roadways per year.
4.2.2 Health Risk. Fatigue is related to increases in health issues, doctor visits, use of sick leave, impaired driving, and difficulty dealing with home and social life. Health issues include, but are not limited to:
• Heart disease and high blood pressure;
• Depression, anxiety, and stress;
• Gastrointestinal disorders (peptic ulcers, indigestion, heartburn, flatulence, upset stomach, or constipation);
• Overeating;
• Higher alcohol and drug use; and
• A lower sense of overall well-being.
4.3 Duty-Time Limitations. Historically, the FAA has managed fatigue in aviation maintenance with personnel duty-time limitations. Title 14 of the Code of Federal Regulations (14 CFR) part 121, § 121.377 states that, “Within the United States, each certificate holder (or person performing maintenance or preventive maintenance functions for it) shall relieve each person performing maintenance or preventive maintenance from duty for a period of at least 24 consecutive hours during any seven consecutive days, or the equivalent thereof within any one calendar month.”
Eventually, an enhanced application of fatigue modelling with use of wearable technologies (e.g., Fitbit devices) will help workers and employers assess fatigue risk and adjust schedules accordingly. SMS and Fatigue Risk Management Systems (FRMS) will help ensure that schedules need not be based on “one-size-fits-all” duty-time limitations.
4.3.1 Scientific Evidence. Scientific evidence indicates that duty time interacts with sleep loss, time of day, time since last sleep, time on task, environmental conditions, type of work schedule, schedule rotation/changes, and other causes of fatigue, and that each should be considered when developing work schedules. An effective approach to managing fatigue risk should take the same data/information into consideration, regardless of the size of the operation.
4.4 FRM. Conceptually, FRM serves to help make informed decisions regarding how to identify, mitigate, and prevent fatigue-related risk. In practice, FRM, be it a plan, policy, program, or system, contains the processes/procedures (i.e., reactive, proactive, and predictive) used for purposes of maximizing personnel alertness. FRM also minimizes
5 fatigue-related performance errors that create safety hazards and risk for the maintainer, team/crew members, the public, and aircraft/equipment.
4.4.1 Promotion of FRM Techniques. Along with the FAA, the ICAO, the European Aviation Safety Agency (EASA), Transport Canada (TC), the Civil Aviation Safety Authority of Australia, and worldwide agencies in the aviation, road, and rail transport industries have been promoting, and in some cases requiring, use of FRM techniques. Most notably, Public Law (PL) 111-216, Airline Safety and Federal Aviation Administration Extension Act of 2010, Section 212(b), Fatigue Risk Management Plan, established a requirement for part 121 air carriers to develop, implement, and maintain a Fatigue Risk Management Plan (FRMP) for the air carrier’s pilots that is acceptable to the Administrator.
4.4.2 Benefits of FRM. Applying FRM strategies has significant worker and organizational benefits related to safety and health. The documented benefits include, but are not limited to:
• Fewer on-the-job accidents and injuries;
• Fewer physical illnesses;
• Reduced absenteeism;
• Reduced turnover;
• Reduced morale problems;
• Reduced insurance claims and premiums;
• Reduced damage to equipment and aircraft;
• Increased average sleep time and sleep quality; and
• An improved quality of life.
4.4.3 SMS. FRM should be part of an SMS. The integration provides a comprehensive approach in identifying hazards and managing risks that extends beyond regulatory compliance. Below are underlying principles of effective FRM as it applies to an SMS:
1. It requires a systemic approach involving, at a minimum, company policies; incident reporting and analysis systems; and reactive, proactive, and predictive risk assessment that define responsibilities, authority, input, procedures and processes, and outputs, which are basic elements of safety management.
2. It requires a partnership between the employer and the employee, as each can contribute uniquely to solutions.
3. It identifies an organization’s hazards related to worker fatigue. Thus, requirements of an effective SMS minimize the need for additional fatigue-specific regulations.
4. It ensures that the hazards and any associated risks are identified and mitigated, and that the level of risk is continuously monitored. Thus, risks are as low as reasonably practical, as it is unrealistic to aim for “zero fatigue.”
6 5 DEFINITIONS.
5.1 Acute Fatigue. Acute fatigue is a somewhat sudden onset of physical or mental exhaustion. It is closely related to recent sleep (last 24 hours), time since last sleep, and current time of day. Less than 8 hours of sleep in the last 24 hours, being awake longer than 17 hours, and working between midnight and 6:00 a.m. are associated with acute fatigue in the average person.
5.2 Biomarkers. Biomarkers are characteristic biological properties that can be detected and measured in the body, such as in the blood or tissue. Biomarkers may indicate either normal, abnormal, or diseased processes in the body. Currently, there are no easily obtainable biomarkers of fatigue. However, several biomarkers of the circadian rhythm exist, such as core body temperature and melatonin levels. In the absence of biomarkers to identify fatigue, we can directly measure fatigue effects in performance variables, or indirectly by using measures of sleep and time of day, and by modeling the effects of these conditions on performance.
5.3 Chronic Fatigue. The average adult needs about 8 hours of sleep per day. If the average person gets less than the required amount of sleep each day for multiple days, then a state of chronic fatigue can occur. With chronic fatigue, performance is degraded and recovery tends to be relatively slow. A person can hasten recovery by attempting to sleep longer than the normal amount for several days. Chronic fatigue is often the result of a physical condition or psychological condition.
5.4 Circadian Rhythm. The body’s internal clock, the circadian rhythm, tells your body when to be awake and when to go to sleep. The circadian rhythm is closely aligned with day and night and is sensitive to light exposure. Humans are preprogrammed to be awake when it is light and sleep when it is dark. Twice during the day, the body slows down. It happens mid- to late afternoon, between 3:00 p.m. and 5:00 p.m., so expect to experience drowsiness during the lull. If one is awake after midnight and into the early morning hours between 2:00 a.m. and 6:00 a.m., which is counter to the body’s natural rhythm, then one should also expect to experience drowsiness.
5.5 Fatigue. Fatigue refers to a physiological state in which there is a decreased capacity to perform cognitive tasks and an increased variability in performance as a function of time on task. Fatigue is also associated with tiredness, weakness, lack of energy, lethargy, depression, lack of motivation, and sleepiness.
5.6 Fatigue Risk Management (FRM). A management program used to mitigate the effects of fatigue.
5.7 Fatigue Risk Management System (FRMS). A nonprescriptive fatigue mitigation system that minimizes the acute and chronic sources of fatigue.
5.8 Safety Management System (SMS). An SMS is a structured management system to control risk in operations. It is an integrated network of people and other resources performing activities that accomplish the safety mission and reach safety goals in the aviation environment. Management of the system’s activities involves planning,
7 organizing, directing, and controlling assets to meet the organization’s safety goals. The safety management process starts with design, and implementing organizational processes and procedures to control risk in aviation operations. Once controls are in place, quality management techniques can be used to provide a structured process for ensuring that the controls achieve their intended objectives, and to improve them where they fall short. SMS relies on reliable and valid organizational data that fosters decision making based on risk assessment (i.e., Risk-Based Decision Making).
5.9 Window of Circadian Low (WOCL). Individuals living on a regular 24-hour routine with sleep at night have two periods of maximum sleepiness. These are known as WOCLs. One WOCL occurs at night, roughly from 2:00 a.m. to 6:00 a.m., a time when physiological sleepiness is greatest and performance capabilities are lowest. The other WOCL is in the afternoon, roughly from 3:00 p.m. to 5:00 p.m., and is less severe than the nighttime WOCL.
6 FATIGUE BASICS. Complex around-the-clock aviation maintenance operations heighten the challenge of fatigue among maintainers. Incident/event reports from maintainers reveal that fatigue is a clear concern. The value of understanding fatigue basics in regard to personal and flight safety cannot be overemphasized. There is evidence that, more often than not, individually we are unaware when we start showing signs of fatigue and unaware of the extent to which fatigue has impaired our performance. This makes it very important that members of the maintenance workforce are able to recognize signs of personal and others’ fatigue as soon as possible.
Understanding the fundamentals of fatigue and how it affects job performance, decision making, and life in general will improve the ability to identify and manage associated safety risks.
6.1 Warning Signs of Fatigue. Be familiar with the following common symptoms of fatigue that could put individuals, coworkers, and the public at risk (Rosekind et al., 1996) listed in Figure 1, Signs of Fatigue, below. These are observable indicators of fatigue. Some signs are more noticeable than others, such as yawning, slowed reactions, and limited communication versus lack of concentration, forgetfulness, and irritability. It is important to note that these are the most common examples of symptoms, not an exhaustive list.
Also, these symptoms do not necessarily indicate fatigue; rather, a collection of symptoms signifies that a person is experiencing at least some level of fatigue.
8 Figure 1. Signs of Fatigue
6.2 Fatigue and Performance. The factors listed in Figure 1, above, are direct causes of fatigue and actually make fatigue unavoidable. Consider this: after 16 hours of being awake, our mental ability to perform work-related tasks decreases to a level consistent with having a blood alcohol concentration of 0.05 percent. After 24 hours of no sleep, mental impairment is consistent with performance deficits observed at roughly
0.10 percent blood alcohol concentration. Similarly, individuals operating on a 2-hour sleep debt over 2 weeks (i.e., 6 hours of sleep, instead of the needed 8 hours, for 2 weeks straight) perform similarly to an individual that has been awake for 16 hours or longer.
Despite increased effort to do the job right, as fatigue levels increase, poor performance is inevitable. As a point of reference, most states and countries consider a 0.08 percent or higher blood alcohol concentration a legal level of impairment for driving a motor vehicle.
6.2.1 Operational Data. Operational data collected by a large U.S. air carrier maintenance organization revealed that individuals working 16-hour days or longer were four times more likely to be involved in a personnel injury incident/accident than an individual working an 8-hour day. Individuals working 12-hour days were two times more likely to be involved in a personnel injury incident/accident than an individual working an 8-hour day. The work-related fatigue symptoms listed in paragraph 6.1 (e.g., reduced reaction time, forgetfulness, and being withdrawn) clearly illustrate the level of risk associated with fatigued maintainers remaining on duty. Numerous field and laboratory studies have clearly shown that cognitive and psychomotor performance decreases with hours of wakefulness.
6.3 Fatigue and Your Brain. When deprived of sleep, the brain generates the response of sleepiness. If deprived of sleep for long enough, the brain can spontaneously shift from wakefulness to sleep in an uncontrolled fashion. The more fatigued you are, the more rapid and frequent the nodding off. You can nod off for short periods (e.g., microsleeps, which last only seconds), or as long as several minutes. Most everyone has unintentionally nodded off at one time or another. The potential safety risk of it happening at the wrong time and place reinforces our personal and organizational
9 responsibilities to manage fatigue risk. The bottom line is that working fatigued not only puts an individual at risk, but also his or her colleagues, and ultimately the flying public.
6.4 Causes of Fatigue. Causes of fatigue are discussed in terms of those that actually make fatigue unavoidable, referred to as primary factors, and those that might lead to fatigue.
Fatigue is the direct result of the following:
6.4.1 Disrupted Sleep and Sleep Loss. Just like food, water, and air, sleep is a basic biological need that is critical to survival. Sleep is necessary for the mind and body to restore itself;
without it, your performance will begin to suffer. You may not be getting a sufficient amount of sleep and/or the sleep that you do get is of poor quality. For example, if a barking dog periodically wakes you multiple times throughout the night, you are more likely to wake up without being fully rested and restored. It makes a big difference when your daily routine includes, as a rule, between 7 and 9 hours of deep and undisturbed sleep. If your daily routine lacks sufficient sleep, then you can expect to experience fatigue symptoms due to sleep debt. Sleep debt is the difference between the amount of sleep a person gets and the amount of sleep that they need. This debt must be repaid in order for you to perform daily activities without feeling fatigue. Be aware that countering a sleep deficit is not as easy as simply extending the time you sleep the next time. Rather, it requires uninterrupted sleep along with sleeping longer. More extended periods of sleep deprivation require more extended periods of sleep recovery.
6.4.2 Prolonged Wakefulness. The amount of time since you last woke up, which is your sleep history, determines how long you have been continuously awake. As the length of time since you were last asleep increases, your level of alertness decreases. This happens regardless of how much or little sleep you got the previous night. There is no way to “stockpile” sleep. You cannot sleep for 12 hours in an attempt to remain alert for the next 24 hours.
6.4.3 Circadian Rhythm. Your body’s internal clock, the circadian rhythm, tells your body when to be awake and when to go to sleep. The circadian rhythm is closely aligned with day and night and is sensitive to light exposure. Our bodies are preprogrammed to be awake when it is light and asleep when it is dark. Twice during a day, the body slows down. It happens mid- to late afternoon, between 3:00 p.m. and 5:00 p.m., so expect to experience drowsiness during the lull. If you are awake after midnight and into the early morning hours between 2:00 a.m. and 6:00 a.m., which is counter to your body’s natural rhythm, you should expect to experience drowsiness.
6.4.3.1 Below are work-related situations and personal choices that minimize opportunities for exposure to light and/or sleep and disrupt your body’s internal clock, making it difficult to get adequate sleep.
• Overtime/back-to-back shifts;
• Early morning and night shifts;
• A rotating schedule;
• No work breaks;
• Long commutes to and from work;
• Travel that crosses time zones;
• Use of sleep aids or other medications that can result in drowsiness or keep people awake;
• Misuse of alcohol; and/or
• Use of caffeine before going to bed.
6.5 Multiple Secondary Factors of Fatigue. Secondary factors do not necessarily result in fatigue; however, they are very likely to contribute to fatigue, especially if you experience more than one factor or if they occur in combination with one or more primary contributors.
6.5.1 Work Schedules. Work schedules that require reporting for duty before 7:00 a.m., after 6:00 p.m., and rotating shifts that do not align with our body’s natural wake and sleep cycle, which results in too little or poor quality sleep. Rotating shifts and overtime can also lead to fatigue based on the previous hours or days worked.
6.5.2 Work Environment. Work environments that put excessive demands on the body may worsen fatigue levels. Examples of excessive demands are: vibration, loud or continuous noise, excessive heat or cold, poor air quality, and poor lighting.
6.5.3 Work Demands. The physical, cognitive, and emotional demands of a job that create relatively high workload contribute to fatigue.
6.5.4 Travel. Travel across time zones creates a mismatch between the body’s internal clock (natural wake and sleep cycle) and the time change. Because the body has no time to adjust, we end up going to sleep later than normal or waking up earlier than necessary, so we do not get enough sleep and, in turn, we experience some level of daytime sleepiness.
6.5.5 Illness. Ongoing illnesses, such as allergies, colds, flu, muscle spasms, etc., can create a level of discomfort that will keep you from getting restful sleep.
6.5.6 Sleep Disorders. Undiagnosed and untreated sleep disorders, such as sleep apnea, restless leg syndrome, and insomnia can keep you from getting to sleep and staying asleep. If you experience disrupted sleep, proper medical care may be necessary.
6.5.7 Lifestyle Choices. Lifestyle choices related to unhealthy habits in general, such as not eating well-balanced meals, not exercising regularly, not staying hydrated, as well as poor sleep habits in particular, such as watching TV in bed, and either smoking, rigorously exercising, or overeating right before bedtime, have a profound negative impact on sleep quality and duration.
6.5.8 Use of Substances. Substances used too close to bedtime, such as caffeine and alcohol, or used too close to waking up, such as sleep aids and medications, can contribute to fatigue.
6.5.9 Stress and Anxiety. Stress and anxiety often will keep you from falling asleep, even when feeling very tired.
7 FATIGUE RISK MANAGEMENT (FRM). Aviation maintenance personnel face a particular risk of fatigue due to night shift work, the potential for long and unregulated duty times, and the sleep disruption that can result from these working conditions (Hackworth et al., 2007; Johnson et al., 2001).
7.1 FRM in Aviation Maintenance. Most of the FRM approaches in industry have been designed for continuous control tasks, such as driving a vehicle or operating an aircraft.
In such tasks, one of the major fatigue-related threats is an unwanted sleep episode, in the form of either an extended period of sleep or a microsleep. In maintenance, falling asleep at work is not the main hazard created by fatigue. Rather, a fatigued maintainer is at increased risk of maintenance errors due to impaired mental functioning. Maintenance organizations face a unique set of fatigue-related challenges; however, they also have access to a unique set of potential solutions. As a result, FRM in maintenance can involve a wider range of countermeasures than comparable systems developed for flightcrews or vehicle drivers.
7.2 Characteristics of Maintenance Work. Although maintenance personnel must contend with significant fatigue risks, some characteristics of aircraft maintenance provide opportunities to mitigate the hazards presented by fatigue.
7.2.1 Maintenance Tasks. Maintenance tasks tend to be self-paced rather than externally paced.
Although much maintenance work is performed under time pressure, a maintainer conscious of impaired performance may be able to pause a task, trade speed for accuracy, or repeat a step as necessary.
7.2.2 Performance Modification. In some cases, there are opportunities to modify methods of task performance in maintenance. In many cases, task cards can be modified and error-capturing barriers can be added and introduced, such as secondary inspections or operational/functional checks.
7.2.3 Flexibility. Maintenance organizations sometimes have flexibility to choose the time at which certain tasks are performed. In such cases, it may be possible to schedule the most safety-critical tasks, or those most susceptible to fatigue, at times when fatigue will have the least impact.
7.2.4 Travel. Most maintainers are not required to travel across time zones while on duty.
Consequently, jet lag and travel-related circadian rhythm disruption, which are major considerations for flightcrew FRMS, are not usually relevant in the maintenance environment. The exception is when maintainers must travel to a remote work site to perform a task.
7.3 Employer and Employee Responsibilities. The conditions that produce fatigue originate not only in the workplace but also in the employee’s personal life. Effective FRM requires a partnership with shared responsibility between the employee and the employer.
7.3.1 Workplace Factors. Workplace factors include working hours, staffing levels, environment, and the availability of break periods.
7.3.2 Personal Factors. Personal factors leading to fatigue can include social and family commitments, commute time, second jobs, and medical conditions that may reduce the quality or quantity of sleep. The employee has a responsibility to ensure, as much as possible, that he or she is rested and “fit for duty” before reporting for work.
7.4 Objectives of FRM. FRM interventions can be characterized not only in terms of the activities that comprise the approach, such as Hours of Service (HOS) limits and incident reporting systems, but also the intended objectives of these activities. An approach common to many risk management systems is a distinction between controls aimed at hazard prevention, and controls directed at risk mitigation (Murphy and Yates, 2009;
Reason and Hobbs, 2003). Consistent with this distinction, the three potential objectives of FRM should be considered as layers of defense.
1. The first and most obvious objective of fatigue countermeasures is to reduce the level of fatigue experienced by personnel at work. This is the approach most commonly referred to when considering FRM. Worker education, HOS limits, and the redesign of shift schedules are examples of interventions intended to meet this objective.
2. The second class of interventions is designed to break the link between fatigue and performance decrements. This can be achieved by reducing the probability that a fatigued maintainer will make an error, or capturing fatigue-related errors once they have occurred. Work breaks and additional task steps designed to capture errors are examples of such interventions.
3. A final approach to manage the risks presented by maintainer fatigue is to minimize, where possible, the operational consequences of errors, including fatigue-related. An example is § 121.374(c), a regulation that prevents a possibly fatigued maintainer from performing the same task on both engines of a twin-engine aircraft used in Extended Operations (ETOPS). The rule is not intended to reduce fatigue or reduce the probability of error. Rather, it tends to minimize the criticality of an error should one occur. This AC acknowledges that manufacturers and operators must conduct appropriate analyses to identify “critical tasks.” For example, fatigued cabin cleaning crew may spill liquids, or loosen connections that could result in subsequent hazard and risk. Sometimes the most basic activity can be critical, so the best alternative is to assume that fatigued workers present hazards, regardless of their position.
8 HOW TO REDUCE FATIGUE. Fatigue reduction interventions are intended to minimize fatigue in the workplace, while recognizing that its complete elimination is not always practical. Interventions include HOS limits (whether voluntary or mandatory), scientific scheduling, napping strategies, education, excused absences, and in certain