Article citation information:
Basaria, F.T. The
analysis of work shift patterns and risk of fatigue in aircraft maintenance
personnel: a case study. Scientific
Journal of Silesian University of Technology. Series Transport. 2023, 118, 5-16. ISSN: 0209-3324. DOI: https://doi.org/10.20858/sjsutst.2023.118.1.
Fransisca Tiur BASARIA[1]
THE ANALYSIS OF WORK SHIFT PATTERNS AND RISK OF FATIGUE IN AIRCRAFT
MAINTENANCE PERSONNEL: A CASE STUDY
Summary. In response
to the COVID-19 pandemic in 2020, PT. XYZ, the biggest aircraft maintenance,
repair, and overhaul (MRO) company in Indonesia, implemented a new shift
pattern for line-maintenance personnel. The new shift pattern allows maintenance
personnel to have fewer working hours per day (7-hour shifts) in more shift
varieties for 5 consecutive days. Maintenance personnel will have 2-morning
shifts, 1-noon shift, and 2-night shifts followed by 3 rest days. This study
aims to explore the risk of fatigue caused by the newly implemented shift
pattern. Data were collected through electronic questionnaires from a total of
303 respondents. This study found that at the time of the survey, many
respondents (78 of 303, 26%) felt tired and had difficulty concentrating,
regardless of the shift they were in. Based on the duty time, the highest
scores of level 6 (tired, difficult to concentrate) were discovered on night
shift day 5. This result shows that although the organization had provided the
maintenance personnel with the opportunity to obtain sleep during rest days,
tiredness and fatigue were still experienced by the aircraft maintenance
personnel. This study recommends necessary actions to be taken to prevent
fatigue, especially from the noon shift afterwards, where fatigue level is
increasing, and alertness level is decreasing.
Keywords: fatigue,
work shift patterns, aircraft maintenance, risk analysis
1. INTRODUCTION
In November 2020, a transition of the previous
2-2 shift pattern to a 5-3 new shift pattern was carried out at PT. XYZ. The previous 2-2 shift pattern allows line-maintenance
personnel to have a 12-hour shift which starts in the morning on day 1 and
starts in the evening on day 2. Following that, maintenance personnel are
supposed to have 2 rest days afterwards.
The new 5-3 shift pattern, however,
allows maintenance personnel to have fewer working hours per day (7-hour
shifts) in more shift varieties. The morning shift on days 1 and 2 starts at 6
AM to 8 AM, the noon shift starts at 2 PM on day 3, and the night shift on days
4 and 5 starts at 9 PM to 11 PM. Maintenance personnel will then have 3
consecutive rest days. These resting days were
intended to be used by the maintenance personnel to recover from their previous
working days. However, the changing shift work may
cause disrupted sleep, which could result in health and safety issues and the
risk of fatigue.
Based on previous research [1], sleepiness and fatigue associated
with a sleep debt are cumulative. Losing an hour of
sleep every other night for a week could result in situations that impair
performance. Much research has focused on flight
crew shift patterns and their ramifications, but there is currently little
evidence on how work patterns may affect aviation maintenance personnel's sleep
and the problems that may result. Thus, this
research aims to analyse the effect of changing shift patterns toward the risk
of fatigue of aviation maintenance personnel.
2. LITERATURE REVIEW
2.1 Fatigue
Referring
to ICAO [2], fatigue is 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 adequately perform
safety-related operational duties. The chief cause
of fatigue is not having obtained adequate rest or recovery from previous
activities. Research conducted by Transport Canada [3] stated that there are three major categories
of fatigue consequences – physical (for example, abruptly nodding off for
a few seconds, called a microsleep), mental (for example, lapses in attention)
and emotional (for example, irritability).
2.2 Managing Fatigue
Fatigue management is a crucial aspect of
safety management since it is a significant and preventable element in
transportation incidents or accidents. Sometimes, organizations and regulators
manage fatigue indirectly through prescriptive limits on work hours, often
because it is seen as the only available option [4]. However, a given amount of break
from work does not necessarily provide a given level of fatigue recovery as the
length of the break is not the main factor but rather the amount and quality of
sleep obtained [5]. Both work
and non-work factors can affect sleep [6]. Work-related factors such as shift length,
work type, workload, work environment, and breaks within a shift can affect the
quantity of sleep and time awake acquired in a 24-hour period. Also, non-work-related issues, such
as sleep disorders, family duties, social and leisure activities, and mental
stress, can impact the amount and quality of sleep people get. These factors
can also influence how long people stay up, which can lead to fatigue. The graph below depicts the
association between these variables.
Work-related factors Non-work-related factors Circadian rhythms Sleep/time awake Fatigue
Fig. 1. Factors affecting fatigue
FAA [7] issued Advisory Circular AC 120-115 stating that the causes of fatigue
in aviation maintenance are shared by the organization and by the maintenance
personnel. It is because both the organization and maintenance
personnel have factors that they can control. For
example, the organization can control the start time and duration of a shift,
schedule changes, rotation of shift schedules, sufficient breaks for employees,
and workplace environment such as lighting, temperatures, etc. On the other hand, maintenance personnel also can control
the amount of sleep they obtain during break days, quality of sleep, and
activities outside work. To be able to take responsibility for themselves,
maintenance personnel must have a thorough grasp of the causes and effects of
fatigue [8]. Conceptually,
managing fatigue can help organizations identify hazards related to fatigue and
mitigate any associated risks beforehand.
The ICAO
SARPs [2] require three types of hazard identification, which are predictive,
proactive, and reactive. In predictive hazard identification, fatigue
could be discovered by reviewing anticipated work schedules (rosters) and
considering the elements known to affect sleep and fatigue. Then in proactive hazard identification, fatigue can be
identified by monitoring the tiredness level in current operations. Meanwhile, fatigue hazard identified by examining the role
of fatigue in safety reports and past events is classified in reactive hazard
identification.
Aligning
with ICAO, Transport Canada applied Reason’s [9] principle of hazard identification in Safety Management System (SMS) to
Fatigue Risk Management System (FRMS).
There are five major levels of
control for managing fatigue risk that an organization can follow:
•
Level 1
(organizational): work schedule
gives employees adequate opportunity to sleep,
•
Level 2
(individual): personal responsibilities of employees to actually get sufficient
sleep,
•
Level 3
(behavioral): monitoring or systems to detect fatigue symptoms,
•
Level 4 (error):
strategies to prevent workplace fatigue from causing errors or mishaps,
•
Level 5
(incident): identifying the role of fatigue in workplace errors or incidents.
A defense system around each level
is necessary to support a successful fatigue risk management system.
Many studies use the Samn-Perelli fatigue scale and
other objective tools to measure pilot fatigue levels at work [10–15]; however, none of these studies has used
aircraft maintenance personnel as the target to survey their fatigue levels
under the various shift schedules.
3. METHODOLOGY
This research
used the Samn-Perelli Status Check, Fatigue Likelihood Score, and Individual
Fatigue Likelihood in determining the risk of fatigue for the newly implemented
shift pattern. Data were collected through electronic
questionnaires. The questionnaire consists of 6 questions that were sent to a
total of 303 aviation maintenance personnel distributed in each work shift.
3.1 Samn-Perelli
Status Check
The Samn-Perelli Status Check is a
7-point scale that subjectively measures the respondent’s level of
fatigue at that moment in time [16]. Possible scores range from 1
(“fully alert, wide awake”) to 7 (“completely exhausted,
unable to function effectively”). This scale was initially designed to
test pilot fatigue and alertness before takeoff.
3.2 Fatigue Likelihood
Score (based on work schedules)
The
primary goal of reviewing work schedules is to understand the possible effects
that particular hours of work will have on sleep opportunities, in addition to
making sure that they adhere to industry standards and other regulations. In the context of a Fatigue Risk
Management System (FRMS), the company is responsible for ensuring that
appropriate opportunity for sleep is provided between work shifts. It is the
obligation of the maintenance employees to take advantage of the available
possibilities for recovery sleep.
Tab. 1
Fatigue Likelihood Scoring Matrix
for Work Schedule
|
Score |
0 |
1 |
2 |
4 |
8 |
|
Total hours per 7 days (hours) |
< 36 |
36.1 – 43.9 |
44 – 47.9 |
48 – 54.9 |
55+ |
|
Maximum shift duration (hours) |
< 8 |
8.1 – 9.9 |
10 – 11.9 |
12 – 13.9 |
14+ |
|
Minimum short break duration (hours) |
> 16 |
15.9 – 13 |
12.9 – 10 |
9.9 – 8 |
< 8 |
|
Maximum night work per 7 days (hours) |
0 |
0.1 – 8 |
8.1 – 16 |
16.1 – 24 |
> 24 |
|
Long break frequency (days) |
> 1 in 7 |
< 1 in 7 |
< 1 in 14 |
<1 in 21 |
< 1 in 28 |
Referring to Transport Canada [3], this is level 1 control for
managing fatigue.
To assess sleep opportunity and
potential fatigue, the following questions should be answered:
1. Hours
worked per seven-day period
2. Maximum
shift length
3. Minimum
length of time off between shifts
4. Hours
worked on night shift per 7 days
5. Long
break frequency
Table 1
shows the scoring matrix of the Fatigue Likelihood Score. Based on Table 1, an
ordinary 9 to 5 working hours (5 days consecutively) would produce a score of
zero. On the other hand, a work schedule of seven 12-hour night shifts,
followed by seven days off, would produce a score of 21, which would be
considered high. This approach
is further described in Figure 2.
Fig. 2. Examples of work schedules
scored
3.3 Individual Fatigue
Likelihood (based on time asleep and awake)
Tab. 2
Individual fatigue likelihood scoring
|
Threshold value |
Scoring |
|
|
X (sleep in prior 24
hours) |
5 hours |
Add 4
points for every hour below threshold |
|
Y (sleep in prior 48
hours) |
12 hours |
Add 2
points for each hour below threshold |
|
Z (time awake since
last sleep) |
Y |
Add 1
point for each hour of wakefulness greater than Y |
Tab. 3
Individual fatigue likelihood score, risk level, and
approved controls
|
Individual Fatigue Score |
Risk Level |
Approved Controls |
|
Acceptable |
||
|
1-4 |
Minor |
Inform the line supervisor and document it in the
daily logbook. Self-monitor for fatigue-related
symptoms, and apply individual controls such as strategic use of caffeine,
task rotation, working in pairs, and additional rest breaks |
|
Moderate |
Inform
the local manager and document it in a fatigue report. Implement
additional fatigue controls such as task reallocation, napping, and increased
level of peer and supervisory monitoring |
|
|
Significant |
Call
the manager before driving to work. Document in a fatigue report on the next
work shift. Do not engage in safety-critical tasks
(including driving to work), and do not return to work until sufficiently
rested as per sleep/time awake rules |
4. RESULTS AND DISCUSSION
This survey was conducted on 3 units
(A, B, C) which were directly affected by the New Patterns Shift 5-3. The
distribution of the number of surveys can be seen in the demography below:
Units of Respondents
A total
of 303 respondents were separated into 3 units. A unit consisting of
216 employees sent 61 responses, achieving 28.2% of respondents. Then C unit totaling 149 employees, sent
66 responses, achieving 44.2% of respondents. While B
unit comprising 276 employees sent 176 responses, achieving 63.7% of
respondents.
Shifts of Respondents
Based on
shifts carried out in these 3 units, it was divided into 5 parts of shift,
namely morning shift 1 (P1), morning shift 2 (P2), noon (S), night shift 1
(M1), and night shift 2 (M2). The response results obtained at the P1 shift
were 54 or 18% of respondents; on the P2 shift, 38 or 12% of respondents; on
the S shift, 60 or 20% of respondents; on the M1 shift, 45 or 15% of
respondents; and the M2 shift, 106 or 35% of respondents (Figure 3).
Fig. 3. Work shifts of
respondents
4.1 Survey Result
4.1.1 Samn-Perelli Status Check
Survey question
number 4 is a simplified version of the Samn-Perelli Checklist, which asked
respondents to rate their level of fatigue at the time the survey was taken. As illustrated in
Figure 4, many respondents (78 out of 303, 26%) felt tired and had difficulty
concentrating, regardless of the shift they were in. Further, 20% of the respondents felt
extremely exhausted and unable to concentrate (60 out of 303), followed by 19%
who felt moderately tired (57 out of 303).
Fig. 4. Respondents’
Samn-Perelli status results
Figure 5
shows an increasing fatigue level of the current condition during each shift. The numbers marked ‘X’ in the
middle of the boxes are the average scores (mean) for each shift, and the
numbers with lines inside the boxes are the median of each shift.
Most respondents on morning shift
day 1 (P1) felt “okay, somewhat fresh” or equal to level 3. This average score then increases
for respondents on morning day 2 (P2) to level 4 (“a little tired, less
than fresh”). On the noon shift day 3 (S) and
night shift day 4 (M1), many respondents felt “Moderately tired, let
down” or equal to level 5. Data on night shift day 5 (M2) has the
highest average score (level 6), which stands for “extremely tired, very
difficult to concentrate”.
This figure
supports the Circadian Rhythms body clock, where human
alertness tends to be higher,
and sleepiness levels are lower at 3 PM
than at 3 AM [17–19]. Aircraft maintenance personnel performance
reaches its minimum in the early dawn, referred to as the ‘window of
circadian low’[20]. The circadian body clock does not adapt
fully to altered schedules such as rotating shifts or night work, although each maintenance personnel have more break time between
shifts.
4.1.2 Fatigue Likelihood Scores
Every maintenance personnel experienced the same
new shift pattern;
therefore, it could
be assumed that the company gives equal opportunity for maintenance employees to rest. This fatigue likelihood score assesses
whether the current schedule provides the maintenance personnel with sufficient sleep opportunities to reduce the risk of fatigue.
Fig. 5. Samn-Perelli Status Check
Assuming each maintenance personnel have 5
working days in which each day comprises 7 working
hours, therefore, the total hours per 7 days is 35 hours
(score 0).
The maximum shift duration of each shift
is ideally 7 working hours, which also produces a 0 score.
The time
between shifts ranges
between 16 to 23 hours;
therefore,
the score for minimum short break duration is also 0.
There are 2 consecutive night shifts of
this new shift pattern. This produces a maximum score of 2 for maximum night
work per 7 days.
The break frequency is 2 in 7 days, which
also contributes to 0 scores for this calculation.
In total, the fatigue likelihood score of this new pattern ranges between 0 to
2.
Based on the
theory, the new shift pattern of 5-3 in line with the
maintenance department is still considered a low-risk category.
4.1.3 Individual Fatigue Likelihood Scores
Figure 6
describes the individual fatigue likelihood score based on the FRMS Survey question numbers 5, 6 and 7. The
numbers marked ‘X’ in the middle of the boxes are the average scores (mean) for each shift, and the numbers with lines inside the boxes are the median of each shift.
Based on the data survey, individual fatigue
likelihood scores are distributed in moderate risk levels.
Most respondents on morning day 1 have an average total individual fatigue score of
6,
which fall into the moderate risk level. Respondents who filled out the survey on morning day 2 duty have a higher individual fatigue likelihood
score (8) compared to respondents
on the morning
day 1 shift. However,
this is also categorized as a
moderate risk level.
On the other
hand, respondents with duty on the
noon shift have a smaller
average total individual fatigue score, which is score 6 and equals to moderate
risk level. The
average total individual fatigue score rises for respondents who participated in the night shift day 4 (total score of 7,
moderate risk level). And
the highest average total individual fatigue score (score 9) was discovered in respondents whose duty is on night shift
day 5. This
average score is considered a
significant risk level and should
be eliminated immediately.
Fig. 6. Individual fatigue
likelihood score results
From the results and analysis, it is known that at the
time of the survey, many respondents (78 out
of 303, 26%) felt tired and had difficulty concentrating,
regardless of the shift they were in. Then 20%
of the respondents felt
extremely exhausted and unable to concentrate (60 out of 303), followed by 19% feeling moderately tired (57 out of 303). Based on the duty time, the highest scores
of level 6 (tired, difficult
to concentrate) were discovered on the
night shift day 5,
followed by level 5 (moderately tired) on night shift day 4 and noon shift. This result shows that necessary actions
are required to be taken to prevent fatigue, especially from the noon shift afterwards, where fatigue levels are
increasing, and alertness levels are decreasing.
Nevertheless, the fatigue likelihood score shows the
contrary. This method of assessment is showing level
1 fatigue control; ensure organizations give a sufficient day off time for maintenance
personnel to sleep. The
risk level of the new
shift pattern is considered low risk based on hours worked per seven-day
period, maximum shift length, minimum length of time off between shifts, hours
worked on night shift per seven-day, and long break frequency. There was no
significant case resulting
in a
higher score of fatigue likelihood. This is due to the assumptions of no overwork during
shifts, maximum of 16 hours of night shifts per seven-day, and no consideration of the circadian rhythm and its effect. Chang et al. [21] revealed that people adapt their work-rest cycles based
on their work days, which prevents fatigue levels from increasing over
successive work days of the same schedule since employees may plan their work
days ahead of time. However, uneven morning and afternoon work
hours could result in excessive weariness with particular shift types.
Thus,
the calculation of fatigue likelihood scores should be detailed in the next control, which is level 2; the quality
of sleep obtained by the
maintenance personnel. Individual fatigue
likelihood score describes whether the sleep obtained during off-duty time is
good quality sleep. From the result
of the Individual Fatigue
Likelihood Scores, it is known that the respondents
on the night shift day 2
experienced significant fatigue (score 9), whereas, on other shifts, respondents underwent moderate
fatigue ranging from a
total score of 5 to 8. It
can be concluded that although an organization has provided the maintenance personnel with the opportunity to obtain sleep during rest days, it does not
necessarily mean that
the maintenance personnel will actually have good quality sleep to recover from
the fatigue they are experiencing. Although the
break time between each shift is longer than 12 hours; however, regarding the
Circadian Rhythms, it might be difficult for the maintenance personnel to sleep when the body clock tends to be on the peak
level of alertness.
Based on the survey results and analysis, it is suggested that an organization should have sufficient fatigue controls in place
to reduce the likelihood of fatigue-related incidents. This can be done by evaluating the possibility of overwork in each shift due to the unavailability of a supporting system (for example, tools, equipment, and next-shift personnel), which could contribute to a higher fatigue likelihood score. It is necessary to review the new shift
pattern of 5-3 in the Line Maintenance
Department and focus more on the actual working hours of the maintenance personnel. Manpower
planning corresponding
to daily load should
be considered to minimize the gap between each shift.
Moreover,
fatigue awareness training and promotion need to be performed
to enhance the knowledge
of fatigue and the importance of having good quality sleep. Managing fatigue responsibility is shared between
the organization and the
maintenance personnel as an individual. Therefore, the maintenance personnel should be better
aware of the fatigue
conditions they experience.
Periodic promotion
events such as webinars, email publications, and banners are favorable as a fresh start.
5. CONCLUSION
The new
5-3 work shift pattern allows maintenance personnel to have fewer working hours per day
(7-hour shifts)
in more shift varieties. The morning
shift on days
1 and 2 starts at 6 AM to 8 AM, the noon shift at 2 PM on day 3, and the night shift on days 4 and 5 starts at 9 PM to 11 PM. Subsequently, the maintenance
personnel will then have 3 consecutive rest days.
Based on the Samn-Perelli Status Check, fatigue likelihood
scores, and individual fatigue likelihood scores, this study finds that at the
time of the survey, many respondents (78 out of 303, 26%) felt tired and had difficulty concentrating,
regardless of the shift they were in. Based on the duty time, the
highest score of level 6 (tired, difficult to concentrate) was discovered on night shift day 5. This result
shows that necessary actions are required to be taken to prevent fatigue and further implications on safety, especially from the noon shift afterwards, where fatigue levels are
increasing, and alertness levels are decreasing.
Consequently,
this study recommends several actions to be taken. The first action is to
provide sufficient fatigue controls in place to reduce the likelihood of
fatigue-related accidents. This can be done by
evaluating the possibility of overwork in each shift due to the unavailability of a supporting system, providing a better rest area and environment. The second
action is to consider the importance of the circadian rhythm and break time
between shifts in future scheduling. The break time
between scheduling should ensure that the aircraft maintenance personnel have
sufficient time to sleep or rest during their off-duty time. Finally, the third action is to offer fatigue
awareness training and promotion to enhance maintenance personnel’s knowledge of fatigue
and the importance of having good quality sleep.
Future
research should consider the effect of work shifts on aircraft maintenance
personnel's work performance. Measurements or techniques that can capture
and evaluate the impact of sleep quality obtained by the maintenance personnel,
break time, and work performance, should be explored.
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Received 28.09.2022; accepted in
revised form 11.11.2022
Scientific Journal of Silesian University of Technology. Series
Transport is licensed under a Creative Commons Attribution 4.0
International License
[1] Industrial Engineering Department,
Faculty of Engineering, Bina Nusantara University, Jakarta, Indonesia 11480.
Email: fransisca.tiur@binus.ac.id. ORCID: https://orcid.org/0000-0001-7445-8688