Dying for a break? Human factors and fatigue management in the MRO sector

Tuesday, November 10, 2020

The RAeS Human Factors Group in Engineering (HFG:E) project team: COLLEEN BUTLER, HSE’s Science Division; ANNA VEREKER, Civil Aviation Authority; KAREN ROBERTSON, QinetiQ and SARAH BOOTH, Baines Simmons, consider the risks and management of fatigue for aircraft engineers.


Discussion of fatigue in aviation incidents is often focused on pilots and cabin crew, with less attention provided to maintenance engineers responsible for round-the-clock planned and reactive maintenance of aircraft. However, the fatigue of maintenance engineers has been identified as a contributory factor in several air accident reports: ‘…improper installation of the split/cotter pin’… ‘fan cowl doors on both engines left unlatched..’ are fatigue-related errors made while performing aircraft maintenance and inspection procedures that have led to in-flight emergencies and fatal accidents(1,2).

The financial implications of aviation maintenance error, even where no accidents occur, can be substantial. If the crew are forced to shut down an engine in flight and return or divert, even if there is only trivial rectification required, the cost to the airline can be significant and can increase with aircraft size, passenger numbers and volume of fuel dumped. Fatigue risk in aviation maintenance can pose significant safety and financial risks to the maintenance engineer, the maintenance organisation, the aviation industry and the public.

The successful management of fatigue risk in aviation maintenance is, therefore, a major safety and business opportunity. The implementation of fatigue risk management systems presents opportunities to optimise engineer alertness and decision-making for safety-critical work, to look after their morale and promote healthier work patterns. The reduction in accidents, absenteeism and staff turnover that can result serves to improve health and safety outcomes and increase productivity.

What does fatigue look like in the context of aviation maintenance?

The International Civil Aviation Organization (ICAO) has defined fatigue as ‘a physiological state of reduced mental or physical performance capability resulting from sleep loss, extended wakefulness, circadian phase, and/or workload (mental and/or physical activity) that can impair a person’s alertness and ability to perform safety-related operational duties(3).’ Some of the characteristics of working in UK aviation maintenance were highlighted in a review undertaken by Simon Folkard in 2003(4).

The research included a survey of licensed aircraft maintenance engineers and their employers. At the time, issues highlighted included the wide variety of more than 100 work patterns, many involving rotating shifts (64%), with night shifts being a feature of both rotating and permanent patterns (41%). Research shows that the relative risk of accidents tends to be highest on the night shift and that rotating shifts where there is weekly rotation can be one of the worst from a circadian perspective.

Links have been established between fatigue and a variety of maintenance errors, including memory lapses (5), taking shortcuts (5), and difficulty concentrating on tasks (6). Examples of where fatigue may have contributed to accidents and incidents highlight the part that long work hours without a break can play.

For example, in 2013 a British Airways A319 suffered a double fan-cowl loss after engineers worked long hours leading up to the night shift and their performance may have been compromised by fatigue. Night work is a frequent feature of engineering work patterns and has been associated with extended hours of wakefulness, reduced alertness due to working in the window of circadian low and sleep loss due to attempting to sleep during the day.

There are reports of individuals (pilots and engineers) developing their own strategies to cope with fatigue; the so-called ‘fatigue-proofing behaviours’ to reduce the likelihood of fatigue-related errors occurring(7). These include taking more time than usual to complete tasks, use of self-selected breaks and break facility areas, peer checking of work and/or use of checklists. However, these strategies are often informal and are not shared and documented across the organisation to ensure that all have access to such best practice behaviours.

Equally, this behaviour may not be evidence-based, relying on strategies that only have very brief benefits for alertness, if any at all (for example turning up the air conditioning in the cab or drinking water). Alan Hobbs and co-workers(6) have highlighted that, compared to other sectors, maintenance personnel face a ‘unique set of fatigue challenges’ and also have ‘unique opportunities for fatigue risk management’ solutions. These include altering the timing of tasks to mitigate the impact of fatigue, considering an individual’s level of fatigue when tasks are assigned and changing the pace at which tasks are completed.

What does the guidance say?

Currently, there are no aviation safety regulations about fatigue management for maintenance engineers, although the CAA has published best practice guidance for managing fatigue in a maintenance environment(8). The Safety Management System (SMS) for Airworthiness is part of future developments within EASA regulations.

Under ICAO requirements(9) this means that ‘Human performance-related hazards are being identified’, and fatigue is captured within the SMS as a hazard. This allows for flexibility in the way that organisations manage fatigue within their operational context; what works for a small operation will not necessarily work for a large one.

The intent of fatigue management is to work with known physical limitations (for example circadian rhythms and workload parameters) to structure work tasks, shifts, rest breaks and routines to make the best use of peak alertness times, and to mitigate low alertness times and cumulative fatigue.

Providing an adequate opportunity for rest away from work is essential. Fatigue is not a hazard that can be eliminated; it is one that requires constant flexible management as the requirements and dynamics of the workforce and business priorities change.

Implementing a FRMS

 There is no ‘one size fits all’ solution to managing fatigue risk but the key elements of any successful FRMS are:

Understanding fatigue risk

As a starting point, organisations are encouraged to obtain an overview of fatigue hazards in their operation – using multiple methods such as surveys and focus groups, considering roster options, and workload.

With this overview, the organisation will be able to identify priorities for fatigue risk management and will be able to tailor processes, procedures and training to their specific operational environment.

Regular communication and flexibility to act

An organisation would regularly check in with employees about their fatigue levels and would have the flexibility to adjust schedules, breaks and tasks as needed to accommodate variances.

Physical and emotional support

Support would be available for issues affecting an employee’s ability to gain adequate rest, including options around childcare and family support, adequate bedding and sleeping facilities (where employees sleep in company-provided accommodation), and support for anxiety and pressure if these issues impacted staff rest.

Acknowledgement of organisational pressures

Business pressures would be acknowledged and catered for, with a clear ‘stop point’ if these pressures accumulated to a level where employees were becoming overstretched. Seasonal differences in work would be accommodated, and extra personnel or other resources provided as needed to meet the business objectives.

Understanding of shared responsibility

Fatigue management would be understood as a joint responsibility between the business and individuals. Many of the factors which can influence fatigue are solely within the control of the maintenance organisation.

It is also important that personnel understand their role and take responsibility for using their rest facilities and the time provided for rest appropriately to ensure that they are fit for work.

Reporting and responding

There is benefit in organisations introducing a fatigue reporting system once mitigation of fatigue risks is established within the organisation. The reporting system would be supported with the ability to respond to reports, or risk being considered ineffective by personnel.

If an event/maintenance error occurs where fatigue is suspected to have been involved, then the organisation would have the capability to investigate this. This provides a valuable feedback loop into the FRMS and wider SMS.

Training tailored to organisational needs

Effective training on the management of fatigue is essential for all areas of the organisation – including those who write schedules, management, safety and human factors teams, and maintenance engineers. Training should be designed to meet the needs of the population being trained, rather than simply ‘off-the-shelf’.

However, training is not a complete solution for managing fatigue; it simply provides knowledge. Personnel must have an opportunity to implement this knowledge within a supporting system to positively impact fatigue.

The bottom line…

Fatigue is not a hazard that can be eliminated; rather, it is one that requires constant flexible management as the requirements and dynamics of the workforce and business priorities change. Included above are both cautionary notes about the consequences of failing to manage fatigue effectively, and ideas for more successful management of a maintenance engineer’s fatigue. This is an ongoing challenge which requires commitment from both maintenance organisations and their personnel.


(1) Air Accident Investigation Branch (AAIB) Report on the accident to Airbus A319-131, G-EUOE London Heathrow Airport, 24 May 2013. Aircraft Accident Report 1/2015.

(2) Accident Report NTSB/AAR-13/01 PB2013-103890, National Transportation Safety Board (2013), N37SH Near Las Vegas, Nevada, US., 7 December 2011.

(3) Loss of Control Sundance Helicopters, Inc. Eurocopter AS350-B2, International Civil Aviation Organisation (2011) Fatigue Risk Management Systems: Implementation Guide for Operators. www.icao.int/safety

(4) Work hours of aviation maintenance personnel. Safety and Airspace Regulation Group Report, CAA Paper 2002/6 (2003), Civil Aviation Authority UK.

(5) Hobbs, A., Williamson, A. (2003) Associations between errors and contributing factors in aircraft maintenance, Human Factors, 45, (2), pp186-201.

(6) Fatigue Risk Management in Aviation Maintenance: Current best practices and potential future countermeasures. Hobbs, A., Avers, K.B. and Hiles, J.J.

(2011) FAA Report DOT/FAA/AM-11/10. Office of Aerospace Medicine, Washington, DC, US.

(7) Fatigue Proofing: The role of protective behaviours in mediating fatigue-related risk in a defence aviation environment. Accident Analysis and Prevention, Dawson, D., Cleggett, C., Thompson, K., Thomas, M.J.W, (2017), 99, 465-468.

(8) Aviation Maintenance Human Factors, (EASA JAR 145 Approved Organisations), UK CAA (2003) CAP 716.

(9) Safety Management Manual, third edition, ICAO (2013) Doc 9859/AN/474.

(10) Baines Simmons (2017) A Framework for Investigating Fatigue. Baines Simmons White Paper 17/01.