Glossary of Human Factors terms

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Glossary of Human Factors terms

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A.C.R.M.
MAINTENANCE CREW ADDITIONAL INFORMATION
© Dedale 1996-2001
DATE: APRIL 2001 Page 1 Trainee's Booklet
Glossary of Human Factors terms
Main Sources:
• ACRM 2000's Instructor Guide © Dedale 1996-2000.
• Human Factors Training for AI/SE © Dedale 2001.
• Adaptation from ECOTTRIS – European Collaboration On Transition Training Research for Improved Safety – NLR. 1999.
• BRIEFINGS (2000) A Human Factors Course for Pilots. Reference Manual  Dedale 1993-2000.
• BRIEFING Notebook © Dedale 1994.
A
Accident ICAO's Definition (Annex 13, chapter 1):
"Event linked to the use of an airplane, that occurs between the moment where one
person goes on board with the intention to make a flight and the moment where all the
persons on board with the same intention are out of the plane, and during which:
one person is fatally or seriously injured and/or there is damage to property or
equipment, and/or the airplane disappeared or is totally out of reach."
Maintenance is not a frequent cause of accidents. It directly contributed (primary cause)
to about 6% of accidents (from 1990 to 1999, source: Boeing) and is ranked number 4
in terms of frequency, just after ‘Flight crew’ (67%), ‘Airplane’(11%) and ‘Weather’
(7%).
Aircraft accidents involve multiple causes and contributing factors. Because only single
cause coding was used, this statistic is a simplification which gives a good idea about
the influence of the categories listed. If we don’t focus only on maintenance as a
primary cause of accident, a 1995 industry study found that maintenance was a
contributing factor in about 15% of the accidents (39 out of 263).
But, on average, maintenance related accidents tend to be very serious. As indicated by
the statistics (source : Boeing), maintenance was the second highest cause of fatalities
related to air accidents, from 1982 to 1991 (1481 fatalities, after CFIT: 2169, and before
Loss of control: 1387). 15 % of accident fatalities have been attributed to maintenance
in the official accident investigation reports.
Note. We have no direct statistics about the number of accidents that have been
prevented thanks to maintenance, and this is rather frustrating!
ACRM Airbus Crew Resource Management.
A stands for Airbus oriented (however relevant for all modern aircraft) and embedded in
Airbus main courses; C stands for Crew: tailored for maintenance crew, cockpit crew
and cabin crew (can be expanded to the whole company); R stands for Resource and M
for Management.
See CRM.
Active failure Active failures are the errors & violations committed at the ‘sharp end’ of the system -
by the front-line operators (for instance maintenance technicians, pilots). Such unsafe
acts are likely to have a direct impact on the safety of the system, and because of the
immediacy of their adverse effects, these acts are termed ‘active’ failures.
ATA 104 ATA 104 is a US regulation concerning maintenance stating that “safety and human
factors related to the subjects should be discussed throughout the course”. At Airbus,
safety and human factors will be addressed in an integrated manner in your technical
training, starting with the MTD 3D briefings of the ATA chapters.
Automatic mode of behavior Opposite of the conscious mode: it is largely unconscious. We may be aware of the
outcome of our action, idea, or perception but not of the process that created it.
Limitless in capacity, it is very fast and operates in parallel (many things at once, rather
than one thing after another). It is effortless and essential for handling the recurrences of
everyday life. Naturally, we prefer to operate in the automatic mode whenever possible.
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C
Circadian rhythm Many biological processes indeed evolve in a sinusoidal way over a period of about 24
hours. This circadian regulation tends to optimize human functional capabilities during
the day and decrease them during the night (this is the case for the sleep/wake cycle, the
body temperature cycle, the secretion of hormones, blood pressure, etc.). The situation
which results from that combination is thus different in day and night shifts.
Maintenance technicians work in shifts, and everyone knows it is harder to work
overnight. The explanation comes from the way fatigue combines to the negative effect
of the circadian rhythm which is decreasing during the night.
See fatigue.
Communication Communication involves the transmission of or interchange of information.
Communication thus consists of an exchange of messages between one or several
transmitters and one or several receivers using one or several modes or ‘channels’,
including speech, writing, gestures, etc.
In a larger perspective, communication can be defined as the motivated establishment
of a relationship aimed at achieving one or several goals.
Communication problems and solutions are reviewed in the course.
Conscious mode of behavior Opposite of the automatic mode. It is restricted in capacity, slow, sequential, laborious,
error-prone but potentially very smart. This is the mode which is used to ‘ pay
attention ’ to something.
Crew Resource Management
CRM
JAR OPS & ICAO definition: Crew Resource Management (CRM) is the effective
utilization of all available resources (e.g. crew members, airplane systems, and
supporting facilities) to achieve safe and efficient operation
MRM stands for Maintenance Resource Management, a terminology often used to
designate a CRM for Maintenance personnel.
See ACRM.
Critical task A task which, if not accomplished in accordance with system requirements, will have
adverse effects on cost, system reliability, efficiency, effectiveness, or safety.
Cross checking Monitoring of other team member activities as a standard practice. Cross checking is a
powerful error detection tool. Its efficiency is due to the fact that errors are usually more
easily detected by others than by those who make them. Cross checking thus makes the
best use of human redundancy.
D
Decision making Ability to evaluate information in order to (timely) choose the optimal course of action,
or to select a solution among different available solutions (does not include the initiation
of standard procedures). Decision making implies making a choice between different
options.
E
Economic issues in maintenance Here are some strong indicators of the role played by maintenance on quality and costrelated matters (flight delays, flight cancellations, IFTB & Diversions, IFSD).
- 1 hour delay: 10,000 to 15,000 $
Maintenance contributed to about 15% of flight delays with respect to Airbus aircraft. It
also contributed to 50% of delays due to engine problems (Source: General Electric).
Besides the financial impact, delays can also impact safety due to the stress they
generate on the crew. Further, delays attributed to maintenance may be partially due to
constraints imposed by the overall system (technical resources and manpower available,
A.C.R.M.
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DATE: APRIL 2001 Page 3 Trainee's Booklet
planning and scheduling of flights, corporate policy,...). Delays are also very often the
result of maintaining safety.
- Flight Cancellation: 50,000 to 90,000 $
Another A/C is needed for the passengers, that results in more than 1 hour delay.
As shown on the slide, maintenance contributed to 50% of flight cancellations due to
engine problems.
- IFTB (In Flight Turn Back) / Diversion: about 300,000 $
The A/C returns to the main base to be repaired (IFTB). If it is diverted the cost can be
higher if no other A/C is available because food and accommodation need to be
provided to the passengers.
- IFSD (In Flight Shut Down). Maintenance contributed to 20% of IFSD (Source:
Boeing). The cost is not estimated because it can have very different consequences: a
short delay if the problem is easily fixed, or a flight cancellation if the problem persists.
If the cost of the engine repair or change is included it can easily reach 500,000 $ to a
million dollars.
- Another category is often referred to as well: AOG (Aircraft On Ground). It is not
mentioned here because it results in a flight cancellation.
Error (human error) Definition 1 (Psychologists and Human Factors specialists)
Definition by James Reason in Human Error (1990):
Error is intimately bound up with the notion of intention. The term 'error' can only be
meaningfully applied to planned actions that fail to achieve their desired consequences
without the intervention of some chance or unforeseeable agency. Two basic error
types: slips and lapses, where the actions do not go according to plan, and mistakes,
where the plan itself is inadequate to achieve its objectives.
An error is NOT intentional. You make an error when:
• what you do differs from what you intended,
• or your plan was inappropriate.
An error differs from a violation. The difference, simply, is that unlike an error, a
violation is an intentional deviation. It is a deviation from a rule, a regulation, a
procedure.
Definition 2 (Industry)
There is another way to define the term ‘error’ in the maintenance domain, and this is a
source of ambiguity. ICAO for example states in its 1995 Circular that: "Human error
in maintenance usually manifests itself as an unintended aircraft discrepancy (physical
degradation or failure) attributable to the actions or non-actions of the aircraft
maintenance technician”. Notice that these ‘actions’ or ‘non-actions’ can be either
‘errors’ or ‘violations’, referring to definition 1.
Error and learning Short-term: we use our errors to regulate our difficulties and risks perception and then
consequently adapt our performance.
Long-term: we memorize what has happened… and benefit from it!
“Error & intelligence are two faces of the same coin” (J. Reason)
Error is the price to pay for our intelligence: flexibility, creativity, adaptation, learning,
anticipation, economy of resources, etc.
‘To err is human’. Human error is embedded in human performance. Error is like
experimentation; from error we learn new ways of doing things. The same processes
that lead to error also produce creative new ways of approaching and solving problems.
Error management Prevention: even if it is impossible to prevent all errors, it is still important to make an
effort on that side. Reason uses the following metaphor to illustrate this “It is better to
drain the swamp than to try to kill all the mosquitoes”. The design of technical systems
and equipment, regulations, procedures, professional skills, team work, good
communication rules, etc. all contribute to prevent predictable errors.
Detection: when an error is committed, what is important is to catch it before it can
threaten safety. The resources and tools mentioned above are also error-detection tools.
Correction/Recovery/Mitigation : These three terms have close meanings.
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‘Correction’ embeds a notion of reversibility while ‘recovery’ doesn’t. (For instance,
when driving if we take the wrong road, making a U-turn on a country road is a
correction, whereas taking another road later on – hence changing our initial route – is a
recovery). ‘Mitigation’ means compensating consequences (e.g. extinguishing a fire).
Here again, the tools and resources mentioned as prevention strategies can also serve the
error correction, recovery and mitigation.
The Airbus Global Safety Strategy achieves error management through design of A/C
systems and equipment (design for maintainability), operating procedures and personnel
training.
General remarks:
- Error detection and recovery improve error prevention, since we rarely commit the
same error twice.
- The detection can take place just before the error is committed (in the course of
action), just after or be delayed (several months later), then creating a latent
condition. Because of the nature of its activity, maintenance is likely to produce a
lot of latent conditions that may affect a flight days, months and even years later.
Example In the case of the 1989 Iowa DC10 engine disk failure, the suspected
inspection failure occurred 17 months before the accident!
Error tolerance System design is of primary importance because it greatly undermines error
propagation.
The consequences of the same error drastically vary according to the system in which
the error is made. For example pushing the wrong button on your television doesn’t
have the same impact as it would on the control panel of a nuclear power plant or on the
MCDU of a glass cockpit.
An error that yields serious consequences and that cannot be recovered is called a
critical error, and a system in which errors can develop serious consequences is called
vulnerable or error-intolerant towards this specific erroneous action.
On the contrary, a system is error tolerant if it is designed so as to ensure that no error
can have serious implications for overall safety.
Expert Being an expert involves at least two components.
First, an expert has spent the time necessary to develop the appropriate skills for the job,
and performs those skills accurately and efficiently. The skills can be physical (motor
and manipulation skills) or mental (the ability to do analyze a situation, etc.).
Experts have also developed the ability to quickly isolate relevant information or cues in
their environment and can recognize significant patterns that will direct their actions
more efficiently (e.g. Trouble-Shooting).
Furthermore, experts better know what they know and what they don’t, which allows
them to remain in their domain of competence, avoiding risky attitudes.
F
Family concept Airbus has wanted to facilitate the transition from an Airbus aircraft type to another,
through the concept of Airbus Family. This concept means a commonality of
philosophy and principles. For example, the way documentation is organized as well as
the way to use it are also similar. They are 3 families which also represent subsequent
aircraft generations: the A300-A310 family, the A319-A320-A321 family, and the
A330-A340 family. They are more similarities within families than between families.
For example an A340 is closer to an A330 than to an A320. Beware of the differences in
order to avoid errors!
Fatigue Fatigue comes from consuming our physical or mental resources. Our resources, mental
and physical, are like fuel in a car. During a normal day, we consume our fuel at a
fairly constant level (like being in ‘cruise mode’ on the highway). But if we have to go
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faster or if we have to work harder, then just like a car, we will consume our fuel more
quickly.
Maintenance technicians work in shifts, and everyone knows it is harder to work
overnight. The explanation comes from the way fatigue combines with circadian
rhythm.
See circadian rhythm.
Followership While leadership is the ability to lead the others, ‘followership’ is the ability to properly
follow the leader. All team members must express their willingness to follow the leader,
but not ‘blindly’. So in case of doubt or if you have any question related to the job or to
safety, you should express your concern (the concepts of ‘assertiveness’ and
‘advocacy’) in the most suitable manner according to your airline culture and policy.
See leadership.
H
Human Factors Originally and generally meaning, “Human Factors” refer to the role of men regarding
safety or quality, in high-risk domains such as aviation, marine, nuclear power plants,
railways, and all intrinsically hazardous processes where human operators interact with
complex technical systems.
“Human Factors” is about people in their living and working environments. It is about
their relationship with machines and equipment, with procedures, and with the
environment about them. It is also about their relationship with other people…
Hence, addressing human factors is dealing with interactions within a large sociotechnical system.
Maintenance Human Factors: today’s reality, taken from the ADAMS report:
“Double standard of task performance:
- quality of task documentation & usability of documentation technology in many
maintenance organizations, quite inadequate from a users point of view
- ‘Black Books’ are universally accepted to exist: illegal, unofficial manuals in which
the technician records useful information for their own reference – making it more
likely for a technician to use information that is not current, up to date and accurate.
- A/C technicians report they do not follow documented procedures as prescribed in 1/3
of the tasks surveyed.
- Technicians & their managers have a contradictory understanding of what the job of
the Maintenance technician involves:
* The technician sees himself as responsible for the A/C safety & of using his
judgement to do what is necessary for that
* The managers see the primary role of the tech to follow procedures as laid down (if
this is done, safety is ensured). But they know that if the procedures were followed
strictly nothing would be done on time”
Human limitations Why do human beings make errors? There is a simple analogy we can use to explain
this. Think first about a machine or a piece of equipment. It was engineered with
specific thresholds in mind - weight tolerance, speed limit, etc. If you take the machine
past its recommended limits, its performance is going to suffer. It may even shut down
altogether.
Humans are very similar. We have mental, physical and psychological limits to our
performance. When we push ourselves past those optimums, the likelihood of error is
going to increase. We make more errors when we are tired or when our mental
resources are consumed with details of a novel and demanding situation.
The biggest difference between humans and machines in this analogy is that humans
can learn and adapt their performance. They can actually change their thresholds. How
do we do this? One way that we learn is from the errors that we make. Have you heard
anyone say «I know I’ll never do that again!» - that is learning from error.
Humans also differ to machines by the fact that they know they are limited and protect
themselves about that. Our knowledge of both our weaknesses and forces explains why
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we are, in spite of our limitations, capable of outstanding performance.
I
Incident ICAO's Definition (Annex 13, chapter 1):
"Any non-accident event, linked to the use of an airplane, that compromises or could
compromise operating safety". "A serious incident is an incident whose circumstances
could have lead to an accident (an accident was about to happen)."
Note that the only difference between an accident and a serious incident lies in the
outcome.
L
Latent condition Latent conditions are to technological organizations what resident pathogens are to the
human body. Like pathogens, latent conditions - such as poor design, gaps in
supervision, undetected manufacturing defects or maintenance failures, unworkable
procedures, clumsy automation, shortfalls in training, less than adequate tools and
equipment - may be present for many years before they combine with local
circumstances and active failures to penetrate the system’s many layers of defenses.
They arise from strategic & other top-level decisions made by governments, regulators,
manufacturers, designers, and organizational managers. The impact of those decisions
spread throughout the organizations, shaping a distinctive corporate culture, and
creating error-producing factors within the individual workplaces. Latent conditions can
increase the likelihood of active failures through the creation of local factors promoting
errors & violations, and can also aggravate the consequences of unsafe acts, by their
effects upon the system’s defences.
Leadership By giving status - e.g. Foreman - the company assigns official authority.
But it's also a matter of personal qualities: attitudes, motivation, experience,
communication, social and human intelligence that confer on someone the capacity to
influence and lead other persons.
A good leader doesn’t need to resort to authority to lead the others: he ‘naturally’ gets
from the team members what he wants because he is trusted and respected.
Learning Learning is the modification of the capacity of an individual to perform a task through
interactions with the environment. Learning can refer either to the process or to its
result. For education sciences, learning defines more precisely the modality of
acquisition of knowledge, skills or aptitudes.
Learning is greatly facilitated when you are motivated to learn. See motivation.
Long lasting team Maintenance personnel often work in long lasting teams, i.e. in teams with low
personnel turnover. Because they work and live together over a long period of time,
team members get used to each other and know each other quite well.
This work organization presents both advantages and drawbacks for safety. They are
reviewed in the course.
People working in the same long lasting team tend to form a ‘clan’. A clan is a social
structure based on relations of proximity and closed to the outside world in which
everyone's roles are defined mainly through tacit rules, enforced through 'peer pressure'
(group conformity). Clan members have the tendency to reject newcomers until they are
considered to be worthy of becoming members of the clan.
M
Motivation Motivation plays an important role in learning. In other words, how you approach your
transition experience can greatly affect the efficiency of the learning.
You can be negative and resistant, and you will find the work that much harder to
master. A closed mind is a slow mind to learn. If you are reluctant to make errors (too
fearful or too proud), you will be too cautious, and you will lose valuable opportunities
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to learn.
Or you can be positive and enthusiastic. The more open you are to the new material, the
faster you will become an expert on the new plane.
Any problem or difficulty? Remember your AI instructors are here to help!
N
Negative transfer (in learning) A condition in which previous experience negatively interferes with the learning of a
new task, usually due to conflicting stimuli or response requirements.
The opposite is called positive transfer.
No Fault Found policy Maintenance personnel sometimes have difficulties in locating a fault. This often results
in undue removals of properly working components, which represents costs for the
airline. The 'No Fault Found' policy has been developed by Airbus Industrie in close
collaboration with the major avionics manufacturers for coping with that problem. This
policy remains the only NFF reduction procedure in use in the aerospace industry today.
It states that the tests performed by Airbus or authorized repair stations are normally
free of charge, unless:
- The airline doesn’t supply supporting data (or chooses not to provide the
substantiating data after the request of the Supplier’s repair station);
- Supporting data doesn’t substantiate the removal;
- The relevant TSM procedures, in relation to a PFR warning message, provide the
correct system trouble shooting.
So if you encounter difficulties in locating a fault, don’t remove a Unit only to prove
that you have done something! By the way, it is very likely that applying the
corresponding TS procedure will solve the problem.
Furthermore, keep all historical data. It helps to put the TS cases in perspective. In case
you sent the Unit to Airbus Industrie or the authorized repair station for testing.
Remember that historical data will be required not to charge the test to your airline.
Note: Details can be found in the Airbus Industrie NFF Policy document, ref.AI/SG-
ES/921.0320/99 – May 1999.
O
Organizational learning Individual behaviors are bounded by the fact that they work within an organization,
which does not imply they have no degree of freedom…
The safety of an organization partly depends on its capacity to learn from experience:
organizational safety. This is based on systems of operational feedback, for example
incident reporting systems.
P
Procedure A procedure defines what the task is, when the task is conducted, by whom it is
conducted, how the task is done, what the sequence of actions is and what type of
feedback is required. A procedure also often includes warnings and cautions, that must
be complied with for its safe application.
Role and features of procedures:
- Predetermined framework for joint action
- Common language which facilitates communication and make it more reliable
- Error detection tool: a common reference makes it easier to detect deviations
- Because A/C systems are complex, opaque and interconnected, procedures are the
only way to interact safely with modern technology aircraft.
Adhering to procedures is absolutely needed with modern technology aircraft!
Practice A procedure is like a music score, it is ‘interpreted’ during the course of action and
transformed into practice. In other words, instructions cannot tell you everything. You
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need to be knowledgeable and properly trained to follow instructions the way they were
intended to be followed. Safe procedure application requires that maintenance staff
understand the main reasons behind the procedures (i.e. that modern technology is too
complex to be operated without proper guidelines) and the consequences of their
actions.
In real operational life, procedures are not always adhered to! Factors affecting
compliance with procedures are reviewed in the course.
Adhering to procedures is absolutely needed with modern technology aircraft!
R
Role The set of tasks performed by a human operator which constitute his/her
purpose in the system. For example, releasing the aircraft to service is one of the
maintenance roles.
S
Skill (1) A goal-directed, well-organized behavior that is acquired through practice and
performed with economy of effort.
(2) An organized and co-ordinated pattern of mental and/or physical activity. It is built
up gradually in the course of repeated training or other experience. Skills can be
described as motor, manual, intellectual etc. according to the context or the most
important aspect of the skill pattern.
Status A status is a recognized social position within an organization. For example, the status
of Team Supervisor / Chief technician / Technician is always attributed by the airline.
Status provides authority, and authority is a source of leadership.
See leadership.
Stress Stress is an automatic response to a disturbing situation. Such a situation can be either
unexpected (an emergency) or anticipated (ex. when you know in advance that you will
work under time pressure, of when you know you will be overloaded - a lot of work to
do). Stress is a vital adaptation mechanism, as it mobilizes resources against any kind of
aggression agent also called a ‘stressor’.
Stress is not only a physical reaction but also an emotional one.
Stress can either be good or bad, it is a matter of intensity: it is good when moderate,
enabling us to adapt to the situation, but bad when in excess, resulting in drastic
performance impairment.
Main sources of stress in maintenance are physical working conditions (light, noise,
temperature and weather conditions, etc.), production pressure (e.g. delivering the A/C
on time) and conflicts (with maintenance, cockpit crew, cabin crew and other
personnel).
Stress can be managed, both at the individual and at the team level. Furthermore, the
organization should prevent conditions favoring excessive stress.
Synergy Synergy is synonymous with proper or efficient teamwork. Synergy exists when the
crew’s performance exceeds the sum of individual performances (the 1+1>2 or 11x1>11
metaphor). Synergy needs some primary conditions to be built: a common goal, a leader
recognized by team members (good leadership and followership), clear roles, tasks
sharing, and communication. See leadership and followership.
T
Transfer The change in performance of a task as a result of previous learning. Transfer can be
positive (former learning helps), negative (former learning negatively interferes) or
absent (former learning plays no role).
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V
Violation The main difference between an error and a violation is that the violation is intentional –
e.g. you intend to deliberately deviate from the procedure. Let us take car driving as an
example. You know it is a red light, and you still go through it. You are aware of what
you are doing when you do it.
Sometimes, a violation can become routine. You have deviated in the past, with no
apparent negative consequences, and probably some short-term advantages (e.g., like
saving time by speeding or running a red light). So the behaviour is repeated, and starts
to become automatic, a habit, albeit a bad habit. Or perhaps the violation has evolved
throughout the fleet such that it becomes the norm, standard practice, «everyone does
it». Here are some reasons why procedures are not followed:
- Team values: The good mechanic is the one who can work without procedures!
- Routine, Habit: I am used to doing it like this, and it works ...
- Group Norms: That’s the way we do it here... in the airline, the team
- Time pressure: I don’t need the procedure anymore, and it’s urgent!
- Economy of resources / Workload management: It's easier to do it this way and it
saves time ...
- Lack of knowledge / Lack of training …Understanding the why’s behind the
procedure
- To be of help or to do someone a favour, to save time and let others save time
e.g. Refuelling above the High level (2%) to please the pilots

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