Fatigue Risk Management
Fatigue is a major human factors hazard because it affects most aspects of a crew member’s ability to perform tasks. It therefore has implications to safety. Fatigue is the general term used to describe physical and/or mental awareness which extends beyond normal tiredness.
The International Civil Aviation Organisation (ICAO) defines fatigue as:
“A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase or workload (mental and/or physical activity) that can impair a crewmembers alertness and ability to safely operate an aircraft or perform safety related matter”
It is the responsibility of crew to ensure they achieve adequate rest in the periods provided between their allocated duties.
It is the responsibility of the operator to ensure crew schedules are planned and operated in a way that enables crew members to remain sufficiently free from fatigue so that they can operate to a satisfactory level of safety under all circumstances.
A disruptive schedule means a schedule which disrupts the sleep opportunity during the optimal sleep time window. The average period for sleep is 7 to 9 hours per day and it can take the average human 15 minutes to fall asleep.
Crew who are sleep-deprived think and move more slowly, make more mistakes, and have memory difficulties. It can be attributed to sleep deprivation, circadian disturbances associated with time zone transitions, and high workload. Studies have shown that 17 hours of sustained wakefulness is equivalent to a blood alcohol level of 0.05 percent, after 24 hours it is equivalent to 0.10 percent.
Humans are “programmed” to sleep during hours of darkness and be awake and alert during daylight hours. In practical terms it is extremely difficult to fully adapt to being awake at night and to sleep during the day. Insufficient sleep can degrade performance. An individual can fall asleep and never know it, nor ever know the duration. Studies indicate sleep periods of 7 to 9 hours per day are necessary to prevent fatigue and sleep debt.
Fatigue results in a reduced ability to carry out operational duties and can be an imbalance between:
- the physical and mental exertion of all waking activities, and
- recovery from that exertion which may require sleep
Getting enough sleep both quality and quantity on a regular basis is essential for restoring the brain and body. Reducing the amount or the quality of sleep, even for a single night, decreases the ability to function and increases sleepiness the next day. Sleepiness eventually becomes overwhelming and results in uncontrollable micro-sleeps.
Sleep science makes it clear that sleep cannot be sacrificed without consequences. It has multiple functions including vital roles in memory and learning, in maintaining alertness, performance, mood and in overall health and well-being. Because of this, well planned science based, fatigue management strategies are crucial for managing sleep loss, sleep debt and sustained periods of wakefulness.
Safety Management System and Fatigue Risk Management System
Operators are required by ICAO to manage their safety risks using a Safety Management System, or SMS. For operations that comply with the prescriptive flight and duty time limits the operator’s SMS should include fatigue as one of the hazards it manages.
Principles from fatigue science can be applied to identify possible fatigue hazards when developing pairings and rosters to improve their design. This means considering factors such as the dynamics of sleep loss and recovery, the circadian biological clock, and the impact of workload on fatigue along with operational requirements. Sleep loss and fatigue are cumulative which requires constant review and mitigation.
A Fatigue Risk Management System (FRMS) is a system that uses a service provider’s SMS processes and procedures to specifically identify and manage crew member fatigue as a hazard. It addresses actual fatigue risk in the operations to which it applies, rather than the predicted risk which is the basis of prescriptive limits. Prescriptive FTL schemes have traditionally been used as the primary fatigue risk control method.
ICAO defines an FRMS as:
“a data-driven means of continuously monitoring and maintaining fatigue related safety risks, based upon scientific principles and knowledge as well as operational experience that aims to ensure relevant personnel are performing at adequate levels of alertness”.
The purpose of an FRMS is to support the safe application of FTL schemes by recognizing the need for crew to be adequately rested before commencing and during flying duties by facilitating both proactive and reactive interventions in relation to the implementation of FTL schemes. A key feature of FRMS is that responsibility for managing fatigue risk is shared between operators and individual crew members.
Risk Management
The objective of Risk Management is to ensure that the risks associated with hazards to flight operations are systematically and formally identified.
The ICAO definition for HAZARD is:
“a condition or object with the potential of causing injuries to personnel, damage to equipment or structures, loss of material or reduction of ability to perform a prescribed function.”
A THREAT is a cause or contributing factor that leads to a hazard.
Four basic factors causing flight risks are: human, technical, environmental, and organizational.
Fatigue can contribute to the risk of accidents by impairing performance in numerous ways:
- Diminished ability to perform certain tasks
- Changes in emotional state and willingness to apply effort
- Changes in the way we communicate
- Loss of situational awareness
- Lapses in attention
- Difficulty concentrating on tasks
- Failing to communicate important information
Fatigue in crew is a significant problem in modern aviation operations.