Fatigue can be described as a physiological state of reduced physical and mental performance capability.

It's caused by four main factors:

  1. Sleep loss
  2. Extended time awake
  3. Working and sleeping at suboptimal times in the circadian body clock cycle
  4. Workload (mental and physical).

Fatigue can affect our ability to perform tasks safely. The more fatigued you are, the more you might find difficulty in maintaining concentration, alertness, or in simply staying awake. Fatigue can therefore increase the risk of errors, which can increase the potential for incidents and/or accidents.

As such, it is important that organisations ensure anyone performing safety-related duties is sufficiently alert.

More information on fatigue is available on human and organisation performance.

Managing fatigue is everybody’s responsibility. Both individuals and organisations need to take steps to manage the effects of fatigue so that it doesn’t result in a safety risk.

Fatigue risk management isn’t a simple task, because there can be numerous causes, many of which are interrelated. These include:

  • Work schedules and rosters
  • Sleep disruption
  • Environmental conditions
  • Physical and mental work demands
  • Physical and mental wellbeing.

Under the Health and Safety at Work Act 2015, fatigue is a risk that must be managed.

The Act states that organisations are required to make sure their operation is safe (so far as is reasonably practicable), which includes minimising the risk of fatigue. Organisations are required to involve all personnel in managing fatigue. Individuals are responsible for taking sensible safety precautions, for example, ensuring they take advantage of rest opportunities to ensure they remain sufficiently alert for subsequent duties.

One means of minimising flight crew fatigue risk is through the control of flight and duty times. Managing flight and duty time, and complying with it, is the responsibility of both the operator and the crew. Some examples of the types of responsibilities both operators and crew have for managing fatigue effectively are:

Operators are responsible for:

  • establishing schemes for regulating flight crew members’ flight and duty times (FDT schemes)
  • providing information and training to workers about the factors contributing to fatigue and the risks associated with it
  • encouraging reporting of fatigue risks so that factors which may cause fatigue can be identified and control measures put in place to manage the risk.

Crews have the responsibility to:

  • make the best use of opportunities and facilities provided for rest. It’s their responsibility to plan and use rest periods effectively to minimise fatigue.
  • not work if they know, or suspect, their personal state makes them unfit to operate, to the extent that the flight may be endangered. They must not fly if they know they are, or are likely to be, in breach of their flight and duty time scheme.

Example FDT schemes

CAA Advisory Circular AC119-2 Air Operations – Fatigue of Flight Crew provides an example FDT scheme for various types of air operations. The example is a complete scheme, and when applied and followed in full is deemed, in principle, to be acceptable.

In accordance with the Civil Aviation Rules, operators can develop their own FDT schemes that, if acceptable to the Director of Civil Aviation, can be implemented as part of the organisation’s risk management provisions.

The alternative FDT scheme for Part 135 day VFR operations within the NZ domestic FIR [DOCX 949 KB], provides an example helping operators understand what needs to be considered in developing their own FDT scheme.

This alternative FDT scheme has been reviewed by the Sleep Wake Research Centre at Massey University and found to be scientifically acceptable when applied and followed in full.

Note: Operators may incorporate this scheme in their exposition without further fatigue management expert input. Before this scheme can be used in an operation, however, the CAA must assess and approve its implementation.

Click here for an editable version of the alternative Part 135 day VFR FDT scheme [DOCX 949 KB].

Assessing FDT schemes

When assessing flight and duty time schemes under the current regulatory framework, we apply the Assessment of Flight and Duty Time Schemes Procedure [PDF 236 KB].

This procedure lays out our expectations and the process we currently use to assess schemes that regulate flight and duty times.

It’s important we continue to gain insights into how fatigue can contribute to incidents and accidents. Lessons learned from these events can help improve fatigue risk management in the future.

Fatigue reporting and investigation

To identify situations where fatigue could be a risk to safe operations, it’s vitally important the individual(s) involved submit a report and investigate appropriately to adequately resolve unacceptable fatigue risks.

These investigations form an important part of an organisation’s safety system. They also provide valuable information to enable the tracking of any accumulated fatigue issues over time.

Visit IFALPA for more information on fatigue reporting.(external link)

CAA Advisory Circular AC12-2 Occurrence investigation provides more information on occurrence investigations. It also provides some specific questions regarding fatigue, to be considered during an investigation.

Safety watch lists - fatigue

ICAO's approach

The International Civil Aviation Organization (ICAO) has set the fundamental standards for fatigue management in aviation. Its website presents an excellent summary on the approaches to managing fatigue, supported by comprehensive resources and guidance. Read about fatigue on ICAO's website here.(external link)

A range of other resources are online. We've collated some of them in the links below:

CASA fatigue management resources(external link)

CASA fatigue management guidance(external link)

FAA advisory circulars and guides associated with 14 CFR Part 117(external link)

FAA fatigue risk management for maintenance(external link)

IATA - fatigue management(external link)

IFALPA - fatigue resource library(external link)

NZAAA - fatigue risk management programme [DOC 64 KB]
This document provides an example for agricultural aviation sectors and is for reference purposes.

UK CAA flight time limitations - guidance and resources(external link)

 Ask us about human factors

If you have any questions about this topic, email humanfactors@caa.govt.nz