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(4) Of the 1,424 flightcrew members responding to a NASA survey of fatigue factors in regional airline operations, 80 percent acknowledged having “nodded off” during a flight at some time 20.
(5) Results of a survey involving corporate/executive aviation operations, 71 percent of 1,488 flightcrew members reported having nodded off during duty 73.
b. Evidence of Fatigue from Accident Investigations. Fatigue has been, and continues to be, a contributing factor in aviation accidents. Currently, the NTSB has seven aviation fatigue-specific recommendations. Since 1993, the NTSB has determined that fatigue contributed to 7 air carrier accidents within the United States, resulting in 250 fatalities and 52 serious injuries.
Recent events continually highlight the operational relevance of fatigue among flightcrew; it is not uncommon that crew fall asleep while flying. NTSB investigations have found that flightcrew on long duty days (a shift of more than 13 hours) exhibit a disproportionate amount of accidents when compared to those on short duty days (a shift of less than 13 hours). The longer the crews are awake, the more errors they tend to commit, especially cognitive errors such as decisionmaking.
(1) NTSB investigators divide the causes of fatigue into operational and personal factors.
Operational factors contributing to fatigue induced by the workplace include short rest periods between shifts, which can be as short as 8 hours under current regulations, rapid rotation of shift start times, which can disrupt circadian rhythms, working early morning and graveyard shifts, and duration of commute, among others. Equally important are personal drivers of fatigue, which are largely habits and behaviors controlled by the individual, such as ensuring proper duration of rest. However, personal drivers of fatigue also depend on many factors such as the presence of sleep disorders, circadian variability, additional employment, and use of alcohol and stimulants.
(2) The table, below, of recent aviation accidents attributed in part to crew fatigue was presented during the NTSB keynote address at the FAA Fatigue Symposium.
Airline Date Probable Cause Outcome American International 808 1993 Impaired judgment, decisionmaking and flying abilities due to fatigue.
3 serious injuries.
Korean Air 801 1997 Crew failure to prepare for/execute non-precision approach.
228 fatalities;
26 serious injuries.
American Airlines 1420 1999 Flightcrew failure to discontinue approach and ensure that spoilers had extended after touchdown. Contributing factor was the flightcrew’s impaired performance due to fatigue.
11 fatalities;
45 serious injuries.
Federal Express 1478 2002 Crew failure to establish and maintain proper glidepath at night. Fatigue was contributing factor.
3 serious injuries.
Page 18 Par 12 Corporate Airline 2004 Combination of fatigue related factors producing pilot error.
13 fatalities;
2 serious injuries.
Shuttle America 2007 Fatigue contributing factor affecting ability to plan and monitor approach leading to runway overrun.
No fatalities.
13. MEASUREMENT AND MITIGATION OF FATIGUE RISK.
a. Factors in Fatigue Risk. Fatigue due to extended work hours, time of day, and shift work induces reductions in vigilance and reaction time and increases in risk of poor decisions, human error, incidents, and accidents. As described earlier, cognitive fatigue results from the interaction of sleep limitations and circadian drives for sleepiness with time-on-task and cumulative duty time effects. Human error due to fatigue is the result of sporadic losses of brain function and attention that increase in frequency with reductions in sleep and circadian drive for sleep. Lapses in attention are random in time, making it difficult to demonstrate the role of fatigue in specific accident cases. Self-reported, subjective sleepiness cannot be relied upon in this context, because it has a low correlation with actual performance impairment. One way to understand the role of fatigue in accident risk is to consider that fatigue causes random periods of inattention that occasionally coincide with operational conditions that demand attention to avert a serious event or incident. Hence, accident risk increases when either:
(1) Lapses of attention increase in frequency due to sleep loss or circadian factors; or
(2) Work demands increase the need for attention.
b. Mitigation of Fatigue Risk. There are two main strategies to reduce fatigue-related accident risk: a) decrease fatigue factors that drive lapses in attention, or b) alter the job so that the task is less sensitive to lapses in attention.
(1) Factors leading to fatigue reviewed above—in brief, they are:
• Time since awakening,
• Cumulative sleep debt, and
• Circadian rhythm of attention.
(a) Determining how multiple fatigue factors combine to lead to heightened risk is difficult without the aid of a computer simulation of fatigue factors and how they combine to increase lapses in attention and heighten fatigue risk.
(b) Biomathematical fatigue models or simulations can derive from the work schedule and likely sleep under those schedules, and the fatigue factors that reduce performance and attention and increase risk of errors and accidents. Fatigue models can help improve performance and safety in operational settings by pointing to job-related factors, such as work
Par 13 Page 19 scheduling, sleep opportunities, and individual sleep habits, which could be changed to reduce the chances of fatigue-related attention lapses that could lead to errors and accidents.
(c) Arranging for less schedule-induced fatigue is important but is only half of the equation. The staff and crews must use sleep opportunities effectively to be rested and prepared for duty. Training of staff and crews should provide basic information on fatigue as contained in this AC, including the measures that individuals should take to be fully rested for duty. Staff and crews need to know that alert performance requires sufficient sleep prior to duty and recovery sleep following duty to prevent cumulative sleep debt.
(2) Operators can modify the work environment to minimize the consequences of fatigue.
For example, training of crews to work together better as a team—commonly known as Crew Resource Management (CRM)—can reduce the chances of fatigue-related mistakes. CRM training includes a range of knowledge, skills, and attitudes that improve the quality of communications, situational awareness, problem solving, decisionmaking, and teamwork. Taken together, these teamwork skills and procedures can catch fatigue-related errors before they adversely affect operations. In addition, the flight control systems themselves can be modified to provide alerts and warnings to pilots to supplement attention to the instruments, reducing the chances that a lapse of attention will lead to a mishap.
14. FATIGUE RISK MANAGEMENT.
a. Fatigue Risk Management System (FRMS).
(1) Prescriptive flight and duty time limitations and rest requirements reduce, but do not eliminate, the conditions that lead to fatigue. FRMSs potentially offer non-prescriptive procedures to reduce fatigue further by addressing the complexity of aviation operations and fatigue challenges associated with aviation operations. FRMSs are inherently evidence-based and include a combination of processes and procedures that are employed for the measurement, mitigation, management, and monitoring of fatigue risk within a specific operational setting 80.
Fatigue risk management programs provide an interactive and collaborative approach to address performance and safety levels of operations on a case-by-case basis, and, therefore, are more adaptive to the specific conditions that create fatigue in a particular operational environment.
(2) An FRMS employs a multi-layered defense to proactively manage operational fatigue risk. The defenses against fatigue risk can include the following levels of intervention:
(a) Flight and duty time scheduling,
(b) Employee training and individual sleep practices and hygiene,
(c) Teamwork and crew resource management, and
(d) Procedural and flight system barriers to error.
b. FRMS Applicability. An FRMS can be used within the envelope of prescriptive flight and duty time limitations or as an alternative to such prescriptive rules if it provides at least an equivalent level of safety. An FRMS enhances the capability of prescriptive flight and duty time
Page 20 Par 14 limitations to provide an equivalent or enhanced level of safety based upon the identification and management of fatigue risk relevant to the specific circumstances. Use of an FRMS can allow greater operational flexibility and efficiency while maintaining safety by relying on in-flight measurements of sleep and alertness, including subjective reports by crewmembers, to monitor how scheduling affects flight and cabin crew alertness during flight duty.
(1) Commercially available computer models can be used to predict average performance capability from sleep/wake history and normal circadian rhythms. Models embedded within the FRMS process can help operators understand the likely effects on performance of sleep obtained before and during trip patterns. Such models, though not required, encapsulate the latest scientific research on human circadian systems, sleep, and performance capability and can be useful for rapidly estimating the likely fatigue levels associated with proposed new routes or schedule changes. However, certain assumptions and limitations need to be taken into account.
They represent one useful component of an FRMS, but are not a substitute for an FRMS.
(2) An effective FRMS is data-driven and routinely collects and analyzes information and reports related to crew alertness as well as operational flight performance data. An FRMS’s comprehensive range of safeguards helps to control the risk associated with both transient and cumulative fatigue. An FRMS based upon scientific principles and knowledge combined with sound methods of data collection and analysis can help maintain an equivalent level of safety while allowing greater operational flexibility.
c. FRMS as Part of a Safety Management System (SMS). Ideally, an FRMS should be an integral part of an operator’s established SMS and its capability should be commensurate with the risk oversight needs. Whether within an existing SMS or as a stand-alone system, an FRMS applies SMS principles to proactively and continuously manage fatigue risk through a process requiring shared responsibility among management and flight and cabin crewmembers. Since feedback and non-punitive reporting from employees are essential elements of an SMS, a “just culture” is integral to any FRMS program. When properly implemented, an FRMS is a continuous performance improvement process, using feedback on the success or limitations of prior scheduling and fatigue mitigations to suggest improvements for future scheduling and fatigue mitigations.
d. Benefits of FRMS. Aviation carriers, regulators, and groups worldwide are addressing the benefits of incorporating FRMS programs into current aviation operations. Recent examples include easyJet, Air New Zealand, United Airlines, Continental Airlines, the Australia Civil Aviation Safety Authority, the Flight Safety Foundation, and the International Civil Aviation Organization (ICAO). Preliminary data from easyJet’s FRMS program have demonstrated its effectiveness in reducing fatigue 82. Air New Zealand has been a leader in demonstrating the operational benefits of an FRMS as presented at the FAA Symposium, “Aviation Fatigue Management Symposium: Partnerships for Solutions” on June 17—19, 2008 in Vienna, Virginia.
Based on the available research and demonstrated success of such programs, the FAA is exploring ways to implement effective FRMS-based programs in operations where fatigue has been identified as an inherent risk. An FRMS offers a way to conduct safer flights beyond existing regulatory limits and is a promising addition to prescriptive flight and duty time and rest period regulations.
Par 4 Page 21 ORIGINAL SIGNED by Raymond Towles for John M. Allen Director, Flight Standards Service
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