Royal Navy In The Air Engineering Environment English Language Essay

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Today we all live in a 24/7 society and as such we expect to be able to do and get anything we want (within reason) at anytime of the day or night. This need is one of the reasons why many organizations and services have had to instigate some sort of shiftwork pattern for their employees. Today approximately 1 in 5 employed people follow some sort of shiftwork routine. And this is on the increase.

All three services within the UK Armed Forces have worked a number of shift working routines for many years, not only within the field of Aviation but covering everything that would be required to produce a fight force capable of defending the United Kingdom and its interests. Within Aviation and Aeronautical Engineering in particular there are a number of routines that are wildly used to great effect. However, just because we follow these routines does not necessarily mean that they are the best routines.

This report sets out to determine the human factors associated with shift working routines including the negative psychological and physiological effects of shift work.

Then to investigate the various routines that are currently being used within the 3 services and also the routines that are used to great effect within industry.

With the result of proposing a shift working pattern for use both in shore establishments within the United Kingdom.

2.0 Maintenance Human Factors

The Civil Aviation Authority (CAA) number one Safety Risk Issue is Crew and Human Factors with Maintenance Human Factors being part of it.

Human Performance can be affected by:

Drugs, medicines or alcohol

Physical fitness

Tiredness, fatigue and circadian rhythm

Environmental factors

Stress and stressors


Social factors

This report will concentrate and expand on item 3 - Tiredness, fatigue and circadian rhythm

2.1 Sleep

Question: Why do we need sleep?

Answer: To restore both physical and mental function.

How much sleep do we need?

Although Margaret Thatcher claimed to only need four hours a night sleep the pace of twenty first century life means that we are more likely to need around 10 hours of sleep per night.

Today we are living in a Sleep-deprived Society. In that past 20 years, we've added about 148 hours to you annual working and commuting time (which is equal to a full months working Time (Gross, 2009, p. 113).

A suggested rough rule of thumb from Dement a pioneer in sleep research is that we require 1 hour of sleep for every 2 hours we are awake. Therefore a minimum of 8 hours sleep per day.

During sleep laboratory experiments it was found that increasing your sleep from 8 to 8 ½ hours per night has the potential to increase productivity by 25% (Gross, 2009, p. 112).

2.1.2 Sleep Deprivation and the Effects on Health and Performance

It has been proved that sleep deprivation is dangerous and potentially lethal (not that you are likely to die from lack of sleep but that you could from your actions or inactions as a result). Both the Exon Valdez and the Challenger Space Shuttle were attributed to human error caused by extreme sleep deprivation. Several authors have also attributed numerous illnesses to sleep deprivation that include obesity, diabetes and memory loss (Gross, 2009, p. 113).

A recent study into the effect of shift work looked at the different sleep patterns of marine workers. They studied the sleep differences of workers at home and on board. They concluded that 70 - 80% of marine accidents are the result of human error

Some of the effects on performance can be as follows:


Visual and tactile misperception

Mild disorientation

Irritability and short tempered.


Negative mood states

Involuntary sleep (micro sleep).

Short term tasks (with motivation) can often be performed satisfactory.

Poor performance is more pronounced during circadian rhythm lows.

Memory affected.

2.1.3 Fatigue and Sleep Loss

Whatever the specific cause, the main side-effects of shiftwork that are apparent to the worker himself are those of fatigue and loss of sleep. Sleep becomes a major preoccupation of the shift worker, and it is possible to make generalisations about the amount of sleep taken by day and at night, with about 2 hours less sleep in the former than the latter.

Human error is inevitable and can not be eliminated completely. Fatigue has been reported as one of the main factors contributing to maintenance error.

Fatigue is the weariness that accrues form applying oneself to a task over a long period of time.

Fatigue can be mental or physical.

Fatigue results in both an inability to continue a task (mental and physical) and a disinclination to perform the task (motivation).

Sleep and fatigue are intimately related. Fatigue normally dissipates during normal rest and sleep.

Each person has a different ability to withstand fatigue which usually diminishes with age.

In the workplace, working long hours, working during normal sleep hours and working on rotating shift schedules all produce fatigue of some extent (Civil Aviation Authority [CAA], 2002, Ch. 4, p.13).

2.2 Circadian Rhythm

Most animals including humans display a Circadian Rhythm, from the Latin Circa - about and dies - day, 'about a day'.

A number of physiological and mental functions are affected by the circadian timing system, these include:

Hormonal output

Heart rate

Metabolic rate

Breathing rate

Body temperature

Alertness and even urine excretion

Many studies have shown that the periodicity or rhythm of a number of aforementioned physiological and behavioural functions persist if we suddenly reverse out activity pattern and sleep during the day and are active during the night. This indicates that these rhythms are internally controlled (Gross, 2009, p. 201).

However, our circadian rhythms are kept on the once-every -24-hour schedule by regular daily environmental (exogenous) cues called zeitgebers (from the German meaning 'time givers'). The most important zeitgebers the daily cycle of light and dark. If we persist with our reversal of sleep and activity, the body's circadian rhythms will (after a period of acclimatisation) reverse and become synchronised to the new set of exogenous clues (Gross, 2009, p. 201).

Some people can take five to seven days to adjust, others take up to 14 days, and some never achieve a complete reversal. The changeover period is sometimes very stressful, and shift workers often report experiencing insomnia, digestive problems, irritability, fatigue, even depression, when changing work shifts. In shift work, the zeitgebers stay the same, but workers are forced to adjust their natural sleep-wake cycles in order to meet the demands of changing work schedules (Gross, 2009, p. 201).

The psychological distress that often accompanies shiftwork from its onset may be the primary factor that provokes many (approximately 20-50 %, depending on the source data) to leave shiftwork (CAA, 2003, p.4).

2.2.1 Circadian Rhythm and Shift Work

It has been said that there are two things wrong with shiftwork; having to work when you ought to be asleep, and having to sleep when you ought to be awake. Although shiftwork has been with us since Roman Times (normal city traffic in those days being restricted to the night hours), there is little doubt that shiftwork involves patterns of behavior that is basically unnatural to the human animal (Monk, Folkard, 1983, p. 97).

The rapid growth in shiftwork over the last few decades has meant that society can no longer rely on a small pool of people that can cope happily with shift work. In Europe and the US it has been estimated that about 20% of the work-force in currently engaged in some sort of shift work with the figure around the 17% for the United Kingdom (Monk, Folkard, 1983, p. 97).

For workers to successfully cope with shiftwork there are essentially three factors which have to be 'got right', namely sleep, social and family life, and circadian rhythm (Monk, Folkard, 1983, p. 97).

The circadian rhythms and their adjustment (or, rather, lack of it) has dominated much of the recent research in the shiftwork area. They provide a temporal structure to life that is disrupted by the need to work at night. That a structure exists is obvious, with dramatic differences in behavior and physiology between states of sleep and wakefulness.

2.2.2 Circadian Rhythm Change (Monk, Folkard, 1983, p. 101)

From the above discussion of circadian rhythms it becomes clear that the pattern with which morning, evening and night-shifts are worked is important in two respects. First the rate with which shifts change will determine the degree of circadian rhythm phase adjustment that can occur, with little or no phase adjustment occurring when only one or two shifts of a particular type are worked before changing to a different type. Secondly the direction of rotation would also seem to be important with morning; evening, night rotation facilitates adjustment better than night, evening morning.

Although there are many different types of shift systems it is possible to create three broad categories. These are:

The Permanent Shift System.

This is where an individual only works one sort of shift eg nightwatch security.

The Slowly Rotating Shift System.

This is where the shift system rotates slowly (ie weekly, fortnightly, or monthly). This type of system is probably the one use most frequently, particularly when the system is not continuous (ie when there are times of days when there is no one working); it is particularly prevalent in Britain and North America.

Many other view points is that the weekly rotating routine should be avoided due to the fact that just as the shiftworker starts to adapt to the new routine that shift changes and he/she must start again. The very slowly rotating system (3-4 weeks) is more acceptable but this would require the shift worker to maintain his sleep/wake routine even on his off days.

The Rapidly Rotating Shift System.

Under this type of system the worker never works more than one or two shifts in a row before changing to a different time. Thus, he might work two morning shifts, followed by two evening shifts, followed by two night shifts followed by two or three days off, then the cycle repeats itself.

2.2.3 Rhythms in Physiological Measures (Monk, Folkard, 1983, p. 104)

For people to work at night then either their circadian rhythm will need to adjust to become in phase with the new schedule or they will have to sleep and work at time that are inappropriate to their circadian rhythm.

Studies have shown that it can take a considerable amount of time for individual circadian rhythms to adjust to the new schedule with some individuals taking 12 days to become aligned.

Because this adjustment does take so long then expert opinion has divided into to groups:

That there is a permanent shift system with the individual living by the same routine even on their days off.

That the rapidly rotating system should be adhered to. This routine minimizes the shift of the circadian rhythm. With the lack of adjustment to be a positive thing as they believe that the constant re-setting on the circadian system is more harmful that living a few days with their circadian system that is in the wrong phase.

There are two distinct disadvantages to the rapidly rotating system these are that the night shift performance may be impaired and that sleep dept may quickly build up requiring that two or three days off are given after each short run of night duty to recharge the batteries.

2.2.4 Larks and Owls (Gross, 2009, p. 113)

Studies have found that 5-10% of the population fall into two categories; Larks (morning types/early birds) wake early, ready to face the day and owls (night adepts/night birds) wake later, struggle to wake up, and stay up later at night.

There is some evidence to suggest that Owls circadian rhythms are longer than 24hrs, while larks' cycles are much closer to the 'classic 24 hours'. Only 5-10% of the population falls at either end of this spectrum, with most of us falling somewhere in between.

Nevertheless, morning types can endure the punishing schedule of late shifts better, ands suffer fewer physical problems than the evening types. The crucial factor is how easily a person's body clock can be reset. Because morning people's clocks are more stable and need no tuning they're exactly 24hours- even on shifts the clock stays constant.

These finding suggest that night workers should try to orient their whole life towards being a daytime person, who just occasionally stays up all night to work. Shifts should be broken into units of just a few days to minimise circadian disruption.

However, Chronobiologists (those who study biological rhythms) recommend that the way to maintain alertness and reduce the risk of accidents is to try and adapting the body clock to suit fully the new work patterns, making shift changes less often not more.

2.3 Diurnal Variation

Diurnal variation considers the effects of the time of day have on people's ability to perform various tasks. These diurnal variations in performance are thought to reflect the 24hrs rhythms that are now known to exist in the vast majority of biological functions. Under normal circumstances they result in predictable trends in performance over the day, with the precise nature of these trends being influenced by various factors such as the demands of the task and individual differences. Such time of day effects on performance have obvious practical implications in a variety of situations such as the school timetabling and shiftwork systems (Folkard, 1983, p. 245).

There is some evidence that the effects of stress on performance differ markedly depending on the time of day. Clearly, the influence of time of day has both theoretical and practical implications for the stress and performance area.

2.3.1 Short Term and Long Term Memory

It has commonly been assumed that time-of-day effects in performance reflect the single circadian rhythm that is itself controlled by a single 'Biological Clock. This implies that if an individual's performance on one task is low at a particular time of the day, then his/her performance on all other tasks at the same time of day would also be low (Folkard, 1983, p. 249).

Several studies have been carried out on the performance of memory tasks have shown that memory tasks may differ over the day in relation to other tasks. However, the exception to the through the day improvement in performance is found with memory tasks.

Several studies have been carried out in relation to short and long term memory. Short term (or Immediate) memory has shown to be opposite to the motor skill performance as it is highest first thing in the morning and lowest in the early evening. Also that the difference between highest and lowest performances is considerably greater than the deviation in the motor skill tests. Studies have also found that long term (or delayed) memory is more inline with motor skill performance and is superior when presented the material in the afternoon or evening.

2.3.2 Working Memory

Studies have shown that different types of memory processes may show different trends over the day. Many of the tasks that people perform are, however not pure memory ones, despite the fact that they are clearly more complex than the simple immediate processing tasks such as visual search. These tasks, which include mental arithmetic, reading, reasoning, have been characterized as involving working memory and are becoming more frequent in industrial situations due to the increased use of high technology. They have in common the fact that they involve both immediate processing and short term memory. Much experimental evidence exists that performance on these tasks reaches a maximum about mid-day (Folkard, 1983, p. 258).

2.3.3 Sensor and Motor Skill Performance

This area has had a great deal of research carried out since the 1960's due to the increased need to maintain high levels of productivity and safety on various shift systems (Folkard, 1983, p. 252). Several studies have found that performance is low in the morning, high at about 20:00. Afternoon superiority for the sensor and motor skill performance. A number of authors have reported similar trends including reaction times and vigilance performance. Therefore the improvement of performance over the day for perceptual -motor tasks requiring immediate processing of information appears to have at least some generality (Folkard, 1983, p. 254).

2.4 Conclusion

The conclusion to be made from all the studies carried out regarding Shiftwork, Circadian Rhythms and Diurnal Variations is that there is no single shift pattern that is preferable over the others without taking into account the individual and the nature of task to be carried out. Each routine has advantages and disadvantages over the others.

Further work would be required in order to investigate whether it is possible to scheduled specific aircraft maintenance to coincide with the times of the day when performance for that particular type of task is optimal.

3.0 Working Time Regulations

Adult workers cannot be forced to work more than 48 hours a week on average - this is normally averaged over 17 weeks. You can work more than 48 hours in one week, as long as the average over 17 weeks is less than 48 hours per week.

Your working week is not covered by the working time limits if you have a job:

where you can choose freely how long you will work (eg a managing executive)

in the armed forces, emergency services and police - in some circumstances

as a domestic servant in private houses , as a sea transport worker, a mobile worker in inland waterways or a lake transport worker on board sea going fishing vessels

The Working Time Regulations 1998 (WTR), which brought into force the EU Working Time Directive, originally became part of British law on 1 Oct 98 and have been amended subsequently. The Armed Forces are subject to the regulations. Important exemptions were granted which allow employers considerable flexibility in implementing the regulations.

The WTR govern the maximum hours an employee can work. Failure to comply with the Working Time Regulations would amount to a breach of Health and Safety laws which in turn may result in legal action being taken against the MOD and/or a Commanding Officer.

3.1 Armed Forces Working Time Regulations Exemptions and Derogations

Regulation 18(2)(a) of the WTR provides exemption where characteristics peculiar to the Regular Armed Forces 'inevitably conflict' with some of the regulations. This is not a blanket exemption; it does not apply to routine activities undertaken by members of the Regular Armed Forces. In practice the nature of the activity is such that it can not be made to comply with the WTR without the detrimental effect on operational effectiveness, the exemption should apply.

Basically, this includes the following activities:

Operations (including military aid to civil authorities, where it is not possible to conduct activities within the prescribed working time limits.

Support of and preparation for operations.

Exercises and training simulating operational conditions, including their support.

Training (including exercises) aimed at causing fatigue and stress to prepare for or simulate an operational situation.

Working at Sea or in the Air

Work at sea or in the air is subject to the WTR. However, where it can be shown that adherence to normal working time limits would inevitably have an adverse impact upon operational effectiveness, the sea and air duties in question will be regarded as falling within the scope of the 'inevitable conflicts' exemption of the WTR. Flying hours are dealt with separately.

Working Limit Opt-Out

There is legal process by which workers can agree to work longer than the 48 hour limit. This Opt-Out agreement must be in writing and signed by the worker.

However, this Opt-Out process does not apply in the case of regular military personnel, as the hours worked will either by governed by forces working routine regulations, or the relevant exemptions will be applicable.

Working at nights

A night worker is someone who works at least 3 hours at night. A night worker can not opt out of the night time working limit.

Special Hazards

Where a night worker's work involves special hazards or heavy physical or mental strain, there is an absolute limit of eight hours on the worker's working time each day. This is not an average!


Although the Working Time Regulations give strict guidelines for the working week it is evident that the regular forces have a number of exemptions and derogations that could result in the Soldier, Sailor and Airman being expected to work far in excess of the maximum allowable weekly hours. As such the working time regulations are only really applicable to UK based none operational forces, whether this gives rise to flight safety implications are grounds for another report.

4.0 Shiftwork

4.1 What is Shift Work?

Shift work occurs in a work schedule that utilizes 24 hours a day and occasionally, 7 days a week, to keep an organization operating. Shift work occurs whenever 24 hour coverage is necessary or when a 24 hour day optimizes work output and productivity.

4.2 Who Works Shift Work

Once considered a manufacturing issue, shift work occurs today in many industries and fields. The police force, military, security, healthcare, retail, restaurants, hospitality, service stations, transportation, fire brigade, customer service call centres, newspapers, media, and any facility that houses people 24 hours a day such as prisons and nursing homes, and more, require shift work to keep their operations running.

4.3 Why do we work a shift pattern?

There are a number of personal reasons why people chose to work a shift routine, these include:

More time with the family.

A second Job.

Minding the children whilst the other partner is at work.

Rates of pay for shift work tend to be greater than the standard rates.

Travelling time can be greatly reduced due to commuting to work outside the usual rush hour times. This has the added advantage that as you will be able to travel further within the same period it offers up the opportunity to live where you want to and not as close as possible to the place of work.

Enable other things to be done during the day such as attend college etc.

There are less outside interference and time can tend to be more productive.

This is not a personal choice but it might be that they don't have a choice in the matter. If they want the job they have to work the routine.

Aviation Maintenance and Shiftwork

CAP715 (2002, p. 14) details that the requirement for shiftwork within the civil aviation sector is due to the fact that most aircraft movements occur between 6 a.m. and 10 p.m. to fit in with the requirements of passengers. Therefore aircraft maintenance engineers are required whenever aircraft are on the ground, such as during turn arounds. However, this scheduling means that aircraft are often available for more significant maintenance during the night. Thus, aircraft engineering is clearly 24hours business and it is inevitable that, to fulfil commercial obligations, aircraft maintenance engineers usually work shifts.

The Armed Forces and Shiftwork

Unlike the civilian aviation industry whose primary driver is inevitably to make money, the military is not a company interested in making a profit for shareholders. Their purpose is the defending of the United Kingdom and its interests and the strengthening of international peace and stability. This is a 365 days a year 24 hrs a day commitment and as such the armed forces (Royal Navy, Royal Air Force and British Army) will be permanently on duty to fulfil their purpose.

Within the Military Aviation Environment (across all three services) there are basically two types of squadrons:

Front Line Squadrons

These squadrons are predominately involved in operations and therefore require a 24/7 shift routine because of the 24/7 nature of their purpose and therefore maintainers will need to be on watch at all times to cover any eventuality.

Second Line Squadrons

These squadrons are predominately required for training both aircrew and ground crew that will eventually be supplied to the front line squadrons.

The majority of aircrew training is carried out during daylight hours with a smaller percentage of the time used for night time flying. However, this requirement for aircrew training means that the majority of the time available for the maintainers to carry out the routine scheduled maintenance on the aircraft is after the completion of planned flying, usually at night.

Apart from flying front line operational missions and training there is also a requirement associated with both front and second line squadrons; that is to keep their aircrew current in both day and night time flying by accruing a specified numbers of day and night flying hours each month. This requirement also necessitates the need for a 24 hour watch system.

5.0 Shift working routines

General Shift Work Patterns

Below is a sample of commonly used shiftwork patterns, the morning shift is most commonly 6 am - 2 pm with the evening shift being 3 pm -12 pm midnight and the night shift most commonly 6 pm -6 am:

Three-shift working

The day is divided into three working periods: morning, afternoon and night. This type of shift work usually , but not always, involves one or more weeks of mornings, followed by one or more weeks of afternoon, followed by one or more weeks of nights.

Continental Shifts

This is a continuous three-shift system that rotates rapidly; for example, three mornings, then two afternoons, then two nights. Usually there is a break between shift changes.

Two-shift system early/late-double day

Normally two shifts of eight hours each; for example, 6 am -2 pm and 2 pm -10 pm. Shifts are usually alternated weekly or over a longer interval.

5.1.3 Split shifts

These are full shifts divided into two distinct parts with a gap of several hours in between. Used in industries where peak demands are met at different times of the day, for example catering, passenger transport and service industries.

Specific Shift Work Routines

Below is a sample of specific shift work routines followed by organisations within the service sector and outside the British military environment:

5.2.1 Fire Brigade

Focussing on wholetime firefighters the Fire Brigade provide a round-the-clock service by operating a two shift, four-watch system at stations - red, white, blue and green.

Duties may either be assigned to a day staffed station where you work 4 days on, 4 days off (from 0700 - 1900) or a shift station you work 2 days (from 0700 - 1900), 2 nights (from 1900 - 0700) with four days off.

5.2.2 Fire Brigade Control Room Staff

Control Staff duty shift pattern is two day shifts, followed by two night shifts followed by four rota leave days. Day duties commence at 0800 and finish at 1730 and night duties start at 1730 and finish at 0800.

Air Ambulance/ Police Helicopters

Investigations that shown that the air ambulance and the police helicopters utilise an almost identical watch routine with the only difference being the ratio of engineers to aircraft/bases.

Each engineer will work a 12 hours shift covering the night time hours of 19:00 - 07:00. The engineer will work for 4 shifts then have four off, 6 shifts then 4 off and finally 4 on and the 6 off and then repeat.

The off time maintenance is covered by the on watch engineer at another base. He/she will only carry out maintenance on the aircraft he is covering only if the aircraft is grounded due to an aircraft fault which needs to be rectified before the aircraft can fly again.

This is not a 24 hour shift watch routine similar to the other routines that the author has investigated due to the fact that there is no 24 hour engineering cover, just night time cover.

5.3 MAE Working Routines

Investigations by the author have shown that the Royal Air Force, Royal Navy and the British Army utilise very similar watch routines within the military aviation environment.

Three watch routines that are representative of the majority of the Military forces routines and that will be discussed further are:

The 24 About Watch System.

The Search and Rescue 5 Watch System.

The 'Thrust' Watch System.

5.3.1 The 24 About Watch System


The first routine is the '24 About' Watch System. This is the most common routine followed within Military Aviation Environment. There are three distinctive groups of maintainers used for this routine. A Port Watch, a Starboard Watch and a Night Watch (sometimes called the 'Slip Watch'). Routine (see Appendix 1)

Port and Starboard Watches alternate every 24 hours with the watch changeover being 12:00 each day (Monday to Friday) with the night watch covering the period from 22:30 to 07:30 Monday to Thursday inclusive.

The watch that starts at 12:00 on Friday stay at work until completion of work on the Friday, will cover any additional requirements for work over the weekend (which will be an exception rather that a rule) and then will work until 12:00 on the Monday. This will mean that every other weekend you will be off from 12:00 on the Friday until 12:00 the following Monday. Port and Starboard Watches work approximately 35 hours a week each with nights working 36 hours a week.

Unless there is a manpower requirement, personnel very rarely change from one watch to another with port and starboard watches working the same routine over a two week period. System Advantages and Disadvantages:

The 24 About Routine is a favourite within the MAE for a number of reasons:

You have 24 hrs off to do what ever you want.

Every other weekend you have an extended weekend (12:00 Friday - 12:00 Monday).

Don't have to work nights.

Any sleep deficit can be easily caught up on your off watch period.

Night watch only has to work 4 nights and have 3 nights off.

The routine relatively easy to co-ordinate.

The down side to this routine is that the night watch is always in a fight with their circadian rhythm. It will never be fully adjusted as I have no doubt that the maintainers will try and live a normal life from Friday to Monday night and not live the same night routine. Therefore sleep deficit could be an issue.

There could potentially a smaller sleep deficit experience by the watches on the days of their on watch period (finishing at 22:30 and then back to work again by 07:30 the following day, does not leave a lot of time to get in your 8 hours of sleep). Civilian Variation

The author discovered that Babcocks run a 24 about routine whilst maintaining the RAF Search and Rescue aircraft down in the Falklands Islands. However they do not have a night watch, and are on call from approximately 20:00 each evening until the following morning. Also they work 7 days a week, working 8 weeks on and then have four weeks off.

The Thrust Watch System


An experimental routine that was used by 848 Naval Air Squadron was the 'Thrust' Watch System. This routine was unique to 848 and relatively complicated compared to the '24 About' routine.

Routine (see Appendix 2)

This routine uses eight watches with two watches always working at the same time e.g. Port Watch A and Port Watch B working together and Port Watch C and Port Watch D and so on. There is also a night Watch that works Monday Night 19:00 - 07:00 and Tuesday and Wednesday 22:00 - 10:00.

The routine revolves around only working 3 days (37.5hours) a week and having a duty weekend 1 in 4 with night watch working 36 hours with 4 nights off. At any one time during the week there will be at least 50% of available watch manpower working. The two exceptions to this are on Tuesday Morning and Thursday evening.

The additional manpower on Tuesday allows personnel to be freed up for other activities such as sport, personal administration and Quality Assurance procedures etc.

The additional manpower on the Thursday is due to 'Thrust' surge, this increases the manpower by 25% between 13:30 to 22:30 to coincide with the busiest time of the week for planned aircraft maintenance. Generally no night flying is carried out on a Thursday night to aid the maintenance plan. The additional manpower also allowed for the work to continue over the evening meal times. During quiet periods the Thrust Watch can be stood down until about 16:30-17:00. System Advantages and Disadvantages:

This routine was very popular with maintainers and probably more so than the 24hr about routine. This was largely down to the fact that you only worked 3 days a week and the maintainers had complete days off work rather than a 24hour period (afternoon then morning).

When the individual worked late (22:30) he/she either has the following day off or a later start time the following. Allowing the individual to have the required sleep. Other times there is plenty of time for rest and recuperation. Allows for minimum circadian rhythm shift (except night watch).

The only real disadvantage to the 'Thrust System' apart from the night watch always being in constant battle with their circadian rhythm was that it is relatively complicated to administer compared to the 24hour about system. Although 848 Squadron is a second line unit it has a number of front line operational responsibilities, so when these are combined with personnel's requirement to be away on courses, on leave, on exercise or deployed on operation it was an almost impossible job to co-ordinate manpower.

The Search and Rescue 5 Watch System


This below watch routine is used by 771 Squadron Search and Rescue (SAR) Squadron based at Royal Naval Air Station Culdrose. 771 Squadron have experimented with various watch routines over the last 15-20 years but always return to the 5 Watch System. This routine is quite unique within the Royal Navy due to the fact that the Squadron is required to provide 24hours a day 7 days a week Search and Rescue capability.

Routine (see Appendix 3)

The routine revolves around a 5 week 7 days a week watch period. On any one day there will be a watch covering the daytime hours (07:00 - 18:-00) followed by a different watch covering the evening hours (18:00 - 07:00). Each watch will work 7 days of 07:00 - 18:00 and then have 7 days off then work 7 days of 18:00 - 07:00 and then have 14 days off and then the cycle will be repeated. Due to the fact that individuals only work 2 weeks out of 5 the Squadrons leave (holiday) policy is that all annual leave entitled (38 days) is withdrawn.

System Advantages and Disadvantages


A favourite routine with maintainers only having to work 2 weeks out of five.

Circadian rhythm can stay fairly constant will little effect during the majority of the routine.

Apart from possible sleep deficit during the night shift this can be cancelled out during the rest of the 5 week routine.


Labour intensive, 5 separate watches.

Circadian rhythm can be affected during the night shift with subsequent changes in performance.

Circadian rhythm never has enough time to shift properly to the night shift routine so the night time performance will never be on par with the day time performance.

6.0 Conclusion and Recommendations

It has been shown that there a number of physiological and psychological effects associated with shiftwork. Experiments have also shown that individuals circadian rhythms can be affected due to the working routine that they follow and also that the diurnal variations have been shown to effect Individuals performance as different times during the day.

The main conclusion to be made from this study is that there is no single optimum pattern and the shift system should be tailored to the individual needs and the specific nature of the tasks to be performed. Each of the routines covered within this report have the own specific advantages and disadvantages.

The recommendation from this report is that a similar routine to the Thrust Watch System would be the ideal routine to follow from within the MAE if it would be possible to irradiate the co-ordination of manpower issues.


Civil Aviation Authority. (2002). CAP715. An introduction to Aircraft Maintenance Engineering Human Factors for JAR66.

Civil Aviation Authority. (2003). CAA Paper 2002/06. Work Hours of Aircraft Maintenance Personnel.

Monk, T. H., Folkard, S. (1983). Circadian Rhythms and Shiftwork. In G. R. J. Hockey (Ed.), Stress and Fatigue in Human Performance (pp. 97-122). Chichester: Wiley.

Holding, D. H. (1983). Fatigue. In G. R. J. Hockey (Ed.), Stress and Fatigue in Human Performance (pp. 145-168). Chichester: Wiley.

Folkard, S. (1983). Diurnal Variation. In G. R. J. Hockey (Ed.), Stress and Fatigue in Human Performance (pp. 245-272). Chichester: Wiley.

Gross, R. (2009). Psychology. The science of mind and behaviour (5th ed.). Dubai: Hodder Arnold.