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Use of NVG in helicopter operations - Night Vision Imaging Systems (NVIS) and Fatigue Management

Night Vision Imaging Systems (NVIS) and Fatigue Management

The following are questions asked of CASA during the development of new fatigue management and night vision rules. Some questions have been edited for reasons of privacy or brevity.

Definitions used

  • AS/NZS 4360:2004 — an Australian/New Zealand standard for risk management
  • FRMS  Fatigue Risk Management System
  • NVG  Night Vision Goggles
  • OTC  Over the counter
  • PSWR  Prior Sleep Wake Rule
Question 1: Why is fatigue monitoring to be a part of the NVG Trial?

CASA has the responsibility to ascertain the safe introduction of legislation. Trial participants engaging in NVG use, in conjunction with CASA oversight, shall assist in ensuring this.

It is now recognised and is undisputed that fatigue impairment not only contributes but is often the causal factor in many accidents within the transport industry. The primary hazard in this field for the introduction of NVG use is the fact that NVG use occurs at night. Although it is acknowledged that some individuals adapt to shift work better than others, it is a simple fact of human biology that physiologically we are designed to work during the day and sleep at night. Humans have an inbuilt body clock (circadian rhythm) that predisposes us to sleep at night and be awake during the day.

Most of us experience difficulty in maintaining normal sleep patterns during the day if we are rostered to work at night. Scientific studies have shown that sleep-deprived individuals have reduced cognitive function which gives rise to increased error rate and decreased performance. It is important to note that this risk can be reduced by strategies and this is the primary purpose of this information and the links contained here. As the Trial progresses, operators may need to alter these strategies in light of company experience to further reduce the overall risk and CASA shall monitor this process.

Question 2: What are the causes of fatigue?

Within the scope of the Trial, there are two principal factors that cause fatigue-related risk:

  1. The first factor may be referred to as work-related causes of fatigue. These are controlled by the operator and include the following:
    • The hours of work rostered for duty.
    • The type of work undertaken (in this case this is limited to NVG use).
    • Environment, specific tasking, aircraft (single pilot/multi crew).

    The operator creates this risk, therefore has the responsibility for managing it safely.

  2. The second factor is non-work-related causes of fatigue which are due primarily to factors controlled by an individual employee’s behaviour, most often outside of work, and as a consequence, these factors become the employee’s responsibility to control rather than the operator's.

This becomes the shared responsibility model in controlling fatigue.

Question 3: How will the Trial participants introduce strategies to diminish the risk?

The trial participants are made up of those operators who have in place a Fatigue Risk Management System and those who have not. For those who have an FRMS, an amendment should be considered to achieve the following:

  • Engage in a risk assessment, with fatigue as a context, of NVG use in operations.
  • Ensure they incorporate adequate adverse event investigation methods.
  • Ensure that the outcome of such events is linked to safety meetings and/or system review meetings.
  • Ensure that current training includes strategies for forward-rotating the roster (not just providing a prior day off), use of the prior sleep wake tool, and observation of behavioural factors.
  • Ensure that the system will include a reporting form for adverse events which will be sent to CASA.
  • Ensure that any relevant item contained within the instrument or CAAP is incorporated in the system and company operations manual.
  • If any amendment to current work practices is required, then evidence of consultation is required.

Once the system is amended, the amendment is to be forwarded to the CASA Service Centre for approval prior to use. The applicable Regional Office will be made aware of the amendment and its approval.

For those operators who either operate to CAO 48 or a standard exemption, then an amendment to the company operations manual is required, incorporating prescriptive limitations, training instructions, administrative instructions, risk treatment measures (as necessary) and any other requirement as stated in either the instrument or the CAAP.

Once the amendment has been created, then this should be forwarded to the CASA Service Centre.

Question 4: How will this shared responsibility model work in practice?

CASA'S RESPONSE (April 2007):

Firstly, the operator has a responsibility to ensure that a roster will afford a crew member the propensity for normal sleep duration within a 24 hour period. If the crew member is rostered for shift duty, it is unlikely that normal sleep duration or quality will occur during the day, therefore current best practice is to limit the amount of consecutive night duties between the hours of 2300 and 0600 (or part thereof) to four (or less if there are prescriptive limitations that apply). This will minimise the accumulation of sleep debt by an individual.

Operators utilising an FRMS will already have this parameter here, and those operators who are not will need to include this as part of their risk management.

Operators, as a part of their risk assessment process, should take into account their particular demographic in reference to the experience level of pilots with NVG use, task, environment, aircraft, type of NVG in use, and other factors to ascertain reasonable prescriptive limitations to diminish the fatigue risk generated by workplace factors. An acceptable means by which this can be done is via the guidance given for the AS/NZS 4360:2004 design standard for risk management.

Operators are also required to deliver training to flight crews to enable them to understand the fatigue management principles as described here.

Operators must have considered contingency plans should an employee consider themselves unfit for work due to fatigue. Individuals (employees) are required to manage their private lives in such a manner so they present themselves fit for duty. They must also recognise and report when this is not the case. This will entail such items as:

  • Recognising how much sleep they require to feel well-rested and attempting to obtain this sleep in allocated breaks.
  • Ensure that the system will include a reporting form for adverse events which will be sent to CASA.
  • The recording of sleep patterns in sleep diaries and using this information to calculate reasonable windows of alertness.
  • Open disclosure with the operator of any additional employment that may result in decreased opportunity for sleep.
  • Open and honest reporting of adverse events for subsequent investigation by an operator.
Question 5: What is the 'Prior Sleep Wake Rule'?

CASA'S RESPONSE (April 2007):

This rule (or tool) may be utilised by an individual to ascertain a reasonable window of alertness based on their recent sleep history. It works on the principle that 1 hour of sleep 'buys' two hours of wakefulness. Simply doubling the last significant sleep period does not cater for the fact that the individual may be carrying sleep debt as a result of a diminished sleep period prior to this one, so the sleep periods considered will be the last two.

Simply put, it utilises sleep duration for the past two periods in excess of two hours to make an assumption as to how long it could be reasonably ensured that flight crews will not be a significant fatigue risk.

Before further explanation, studies have shown that prior to starting duty, less than 5 hours sleep in the past 24 hours and less than 12 hours sleep in the past 48 hours will be likely to introduce significant fatigue risk. Individuals should consider reporting unfit for duty if sleep obtained prior to duty is less than this. An employee should then refer to their sleep diary and add together these two periods (note that if napping of less than two hours occurs, then this may be doubled and added to the finish time). This figure should then be applied to the individual awake time (not the start of duty time, as fatigue commences to be accumulated from the time we wake up). Once this is done, then this will represent a time frame by which the employee can reasonably assure he or she will be fit for duty.

An example of this would be 7 hours sleep last sleep period and 6 hours the previous sleep period. This is greater than the 5/24 and 12/48 requirement. If the individual awakes at 10am, then (7+6+13) it is reasonable that alertness will be assured until 2300 hours that night. Note that after this time, an employee will be likely to be at contextual fatigue risk (flying or driving), but still may be fit for other duties (administrative tasks, etc). This should not be construed as a time where the individual must go and find somewhere to sleep. If in this case the individual was able to achieve a two hour nap in the afternoon and awoke at 1900 hours, then alertness may be assured taking into account 7+2=9 hours applied to 1900 hours forecasts a reasonable window of alertness now out to 0400 the next morning.

Operators and flight crew should attempt to foresee how long a task will take, to the best of their ability, and see that it remains within this period. For background information on this rule/tool, see www.drewdawson.com. Operators requiring further information on this question should e-mail Bill Cox (CASA FOI) at bill.cox@casa.gov.au.

Question 6: What crew training needs to be done to reduce the fatigue risk?

CASA'S RESPONSE (April 2007):

Firstly, crew members need to be aware of the PSWR. Operators also need to advise crew members on how to manage the forward rotation of a roster. Operators usually do this by giving the crew member the day off prior to taking on night duty. This is reasonable, but crews need to know how to manage that day off to enable them to be fit for work that evening. Strategies they should consider should include:

  • Arising early to ensure a small sleep debt.
  • Consider some light exercise during the morning.
  • Individuals report results vary, but consider a lunch high in carbohydrates, avoiding high protein.
  • Ensure quality sleep hygiene conditions exist (noise, temperature etc).

It is likely that most individuals will achieve a good afternoon sleep period after this.

Crew members should also be aware how much sleep debt they are accumulating by working night shift. Firstly, they need to be aware of how much sleep they require to feel well-rested. Most individuals are constantly in sleep debt and think this is the normal amount, so after 1-2 nights where no alarm is set (and sleep debt is diminished) see how long you sleep the following night and this will be what is regarded as 'normal' and is likely to be in the range of 7.5 to 8.5 hours.

Once on night duty, measure sleep periods within the 24 hour period and if sleep debt is accumulated, attempts to reduce this by napping should be made. Note that if a sleep debt of 3 hours is achieved, it does not mean that an individual must achieve an additional 3 hours sleep to reduce the debt. Sleep hygiene involves ensuring that the environment a crew member attempts sleep in meets the following definition whilst on tour:

  • Suitable sleeping accommodation means facilities that provide privacy and are conducive to sleep.
  • Where possible, a separate self-contained room must be provided for each person.
  • The accommodation must be suitable for sleeping under the local conditions, with a comfortable bed and appropriate control measures for noise levels, light, ventilation, insects and pests and climatic conditions.
  • Clean drinking water and easy access to sustenance must also be provided.

Behavioural patterns in fatigued personnel should also be included in this training. Operators should train crew members to recognise the emotional, physical and mental aspects. Crew members must recognise that possible fatigue impairment may occur for them prior to the physical manifestation such as eye rubbing, yawning, etc. They should also understand that whilst an individual may recognise he or she is getting tired, it may be far more difficult to recognise the decreased performance that increased fatigue levels bring to flight operations.


The company needs to provide training in the administrative aspects regarding the Trial such as the prior to flight record, web-based and adverse event reporting. Further information regarding these subjects may be obtained from www.drewdawson.com or by e-mailing bill.cox@casa.gov.au.

Question 7: What about Chief Pilot and Safety Manager/Officer training?

CASA'S RESPONSE (April 2007):

An important aspect of this Trial shall be the company monitor and review process. To enable an operator to understand how any adverse event has been contributed to by fatigue, an investigation (relating to the size of the event) will need to be undertaken. It is anticipated that operators will ensure that pilots record and submit any event that included an error whilst on task. Setting this 'sensitivity' level low will enable the operator to recognise the early signs of fatigue impairment in flight crews. Naturally, the level of investigation undertaken will depend on the magnitude of the error.

To assist operators in understanding fatigue-contributing factors, the following questions should be asked:

  • What time did the event take place?
  • Assurance the flight crew member was inside their wakefulness window as calculated by the PSWR.
  • Asking the crew members for information on possible/diagnosed sleep disorders, prescribed or OTC medications taken, the degree of stress they feel they are under (for example, moving house, new baby, etc).
  • In fact, any issue possibly affecting the wellbeing of the pilot should be considered (for example, what was eaten/drank and when, recent physical activity).
  • Any behavioural characteristics observed by other crew members.

It is imperative that to enable the 'just cultural' aspects of open and honest reporting to continue, that the investigating personnel do not jump to conclusions in apportioning blame. Similar attitudes should also be applicable when addressing flight crew members who consider themselves too tired to undertake a task (they can forecast this to some extent via the PSWR).

Once an investigation has been completed, appropriate action must be considered. With 'sensitivity' levels for adverse events set to low levels, it may be necessary to just collect these data for internal trending purposes. CASA requires operators to have regular safety meetings to discuss events to see if further risk treatment is required and what these treatment measures will entail. If events are more significant in nature, then it may be necessary for more immediate action. Once the event is recorded, analysed and conclusions drawn, with appropriate action as necessary taken, then CASA is to be advised electronically via nvis_hf@casa.gov.au of the event, determinations and actions.

Question 8: What forms must I create?

CASA'S RESPONSE (April 2007):

Pilots are to fill out a pre-flight form at the commencement of a duty period. This form is to contain the following information:

  • How much sleep do you need to feel well-rested?
  • How much sleep did you get in the past 24 hours (>5 hrs)?
  • How much sleep did you get in the past 48 hours (>12 hrs)?
  • Calculate PSWR end time.
  • Forecast end of flight duty time.

Pilots are to fill out a post-flight form and relate any adverse events that occur (note: if there are no adverse events, then only fill out the web-based reporting form at the end of the duty period). This adverse event reporting form should contain the following information:

  • Was the event outside your calculated PSWR end time and, if so, by how much?
  • What was the time of the event?
  • Do you suffer from any diagnosed sleep disorders or undiagnosed sleep disorders you are aware of?
  • On a scale from 1 to 5, with 5 being extreme and 1 being minimal, describe external stresses in your life.
  • Describe any ailments you are currently suffering from.
  • Describe any prescription medication or OTC medication currently being taken.
  • Describe your recent diet include when and what consumed (drink as well).
  • Describe any recent physical activity.
  • Describe recent caffeine intake.
  • Describe the event.