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Maintenance Error Decision Aid (MEDA)^©^

Users Guide^©^

Table of Contents

Introduction 1

1.  Definition of an Error 2

2.  Definition of a Contributing Factor 2

3.  The MEDA Error Model 4

4.  The MEDA Philosophy 5

5.  The MEDA Investigation Process 6

6.  Using the MEDA Results Form 8

    1.  Section I. General 9

    2.  Section II. Event 11

    3.  Section III. Maintenance Error 12

    4.  Section IV. Contributing Factors Checklist 13

        A.  Information 14

        B.  Equipment, Tools, and Safety Equipment 16

        C.  Aircraft Design, Configuration, and Parts 19

        D.  Job and Task 21

        E.  Technical Knowledge and Skills 23

        F.  Individual Factors 26

        G.  Environment and Facilities 30

        H.  Organizational Factors 34

        I.  Leadership and Supervision 37

        J.  Communication 39

        K.  Other Contributing Factors 41

    5.  Section V. Error Prevention Strategies 42

    6.  Section VI. Summary of Contributing Factors, Error, and Event 44

7.  How to Carry Out the MEDA Investigation Interview 45

    1.  The MEDA Interview Team 45

    2.  Guidelines for the MEDA Investigation Interview 46

    3.  Rules of Causation 50

    4.  Overcoming Interviewer Biases 52

        **Introduction**

        The Maintenance Error Decision Aid (MEDA) is a structured
        process used to investigate errors made by maintenance
        technicians and inspectors. It is a way for an organization to
        learn from its mistakes.

        No one wants to make an error. Errors are a result of
        contributing factors in the work place. In many cases, anyone
        confronted with the same contributing factors might well make
        the same error. We estimate that 80%\--90% of the contributing
        factors to error are under management control, while the
        remaining 10%\--20% are under the control of the maintenance
        technician or inspector. Therefore, management can make changes
        to reduce or eliminate most contributing factors to an error and
        thereby reduce the probability of future, similar errors.

        The purpose of this MEDA User's Guide is to provide the
        information that is needed to carry out a MEDA error
        investigation. The investigation is, essentially, an interview
        with the maintenance technician who made the error to find out
        the contributing factors to the error. The MEDA Results Form is
        the main tool that was developed for helping with the
        investigation. It is a four-page document used by the
        investigator during the interview. To help prepare someone to
        carry out a MEDA investigation, the remainder of this document
        is arranged, as follows:

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1.  Definition of an error

2.  Definition of a contributing factor

3.  The MEDA error model

4.  The MEDA philosophy

5.  The MEDA investigation process

6.  Using the MEDA Results Form

    1.  Section I---General Information

    2.  Section II---Event

    3.  Section III---Maintenance Error

    4.  Section IV---Contributing Factors Checklist

    5.  Section V---Error Prevention Strategies

    6.  Section VI---Summary of Contributing Factors, Error, and Event

7.  How to carry out the MEDA investigation interview.

    **1. Definition of an Error**

    What is an error? For simplicity, we will define an error in this
    way:

-   An **error** is a human action (or human behavior) that
    [unintentionally]{.underline} deviates from the expected action (or
    behavior).

    Some theorists, such as Profession James Reason, distinguish among
    different types of errors, such as errors of omission and commission
    or slips, lapses, and mistakes. In the MEDA system, we will work
    with more specific error descriptions, such as:

-   Part not installed correctly

-   Part not installed at all

-   Part installed in the wrong location

-   Not enough oil added during servicing

-   Inspector did not see the fault

-   Tool left in the engine cowling.

    In using specific error descriptions, all of the error types
    discussed above are included. For example, not installing a part
    would be called an error of omission and a lapse or installing a
    part in the wrong location would be an error of commission and a
    (possible) slip. Thus, using specific error descriptions precludes
    the need to determine the specific error type, which simplifies the
    task for the MEDA investigator.

    Sometimes there is confusion between an error and a violation. We
    define a violation in this way:

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-   A **violation** is a human action (or human behavior) that
    [intentionally]{.underline} deviates from the expected action (or
    behavior).

    So, the obvious difference between an error and a violation is
    whether the behavior was intentional on the part of the maintenance
    technician or inspector. As we will discuss later, contributing
    factors and violations sometimes act together in causing an error
    that leads to an event.

    In MEDA, we are specifically interested in errors that lead to
    problems on an aircraft, equipment damage, personal injury, or
    rework. This will become clearer as we discuss the MEDA error model.

    **2. Definition of a Contributing Factor**

    In MEDA the term "contributing factor" is used to describe
    conditions that contribute to an error. In the Human Factors
    technical literature the term "performance shaping factor" is used.
    However, we use the term contributing factor because it is simpler
    to say that "x was a contributing factor to error" rather than "x is
    a performance shaping factor and therefore increased the likelihood
    of an error."

    What is a contributing factor? We simply define contributing factor
    in this way:

-   A **contributing factor** to an error is anything that negatively
    affects how a maintenance technician or inspector does his/her job.

    What affects how a maintenance technician or inspector does his/her
    job? Some things are obvious, like---lighting in the area where the
    task is to be carried out, having the correct tools and parts to do
    the job, distractions or interruptions during task accomplishment,
    and hearing job instructions incorrectly from a supervisor. Other
    things are not so obvious, like---decisions about staffing levels
    made by the management three years ago, errors made by a production
    planner that affects the maintenance technician's task performance,
    and a supervisor who assigns a task to an unqualified maintenance
    technician.

    It is easier to understand the concept of contributing factor using
    a model:

    Figure 1. Contributing Factors to Maintenance Error

    In this model, a maintenance technician works within an immediate
    environment under supervision within an organization. Any of these
    levels or any of the listed items in the model can affect how a
    maintenance technician does his/her job and, therefore, could
    contribute to an error. In Section 5.4 we will define all of the
    terms above and discuss how they can contribute to an error.

3.  **The MEDA Error Model**

    In its simplest form, the MEDA error model is shown in Figure 2.

    Figure 2. Simplified MEDA Error Model

    In this simple model, contributing factors cause errors that cause
    events. However, cause is a "strong" word. We need to think about
    two meanings of "cause."

-   Cause-in-fact: If "A" exists (occurred), then "B" will occur.

-   Probabilistic: If "A" exists (occurred), then the likelihood of "B"
    increases.

    We will find that in the maintenance technician's world there are
    relatively few "cause-in-fact" occurrences, especially with regard
    to contributing factors causing errors. For the "contributing
    factor---error," almost all causes are "probabilistic." For the
    "error---event," it is possible to have some "cause-in-fact"
    instances. For example, leaving an o-ring seal off of a master chip
    detector will (probably) always result in an oil leak if an engine
    is run at take-off power. However, as an investigator, you will find
    that even for the error---event relationship that most causes are
    probabilistic in nature. This causal thinking leads to a more
    complex MEDA error model.

    Figure 3. MEDA Error Model

    This error model shows explicitly that there is typically a
    probabilistic relationship between contributing factors and an error
    and between an error and an event.

    **4. The MEDA Philosophy**

    The MEDA philosophy is based on this error model. The fundamental
    philosophy behind MEDA is:

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-   Maintenance errors are not made on purpose

-   Maintenance errors result from a series of contributing factors

-   Most of these contributing factors are part of an airline process,
    and, therefore, can be improved so that they do not contribute to
    future, similar errors.

    The central philosophy of the MEDA process is that people do not
    make errors on purpose. Nobody comes to work and says "I'm going to
    make a mistake today!" Some errors do result from people engaging in
    behavior they know is risky. Often, however, errors are made in
    situations where the person is trying to do the right thing, and
    others in the same situation could make the same mistake. For
    example, if an error is made because the maintenance manual is
    difficult to understand, then others using that same procedure could
    make the same error.

    Typically an error does not occur due to a single contributing
    factor. During the field test of the MEDA process, the field test
    airlines found that there were, on average, about four contributing
    factors to each error. So, we say that errors result from a
    [series]{.underline} of contributing factors.

    Most of these contributing factors are under management control. In
    order to change the probability that an error will occur in the
    future, the contributing factors must be addressed (i.e., changed or
    fixed). For example, if a person gets the wrong fastener from a
    parts bin because the bin labels are too worn to read correctly,
    then another maintenance technician could make the same error. If
    you wish to change the probability that the error will occur in the
    future, you need to change the bin labels. Too often, when an error
    occurs the maintenance technician is punished and no further action
    is taken. That does not reduce the probability that others will make
    the same error. MEDA is a structured process for finding these
    contributing factors in order to address the contributing factors to
    the error.

    While not based on the error model per se, there are two other
    aspects of the MEDA error philosophy:

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-   The maintenance organization must be viewed as a system where the
    maintenance technician is but one part of the system, and

-   Addressing the contributing factors to lower level events helps
    prevent more serious events.

    The maintenance organization is a system, and the maintenance
    technician is part of that system. This fact is illustrated in
    Figure 1 where we showed that a maintenance technician worked in an
    immediate work environment under supervision following the policies
    and procedures developed by the management in order to run the
    business. This is called a "socio-technical" system, which indicates
    that both technical issues (e.g., tooling, technical documentation,
    and aircraft systems) and social issues (e.g., teamwork) affect the
    maintenance technician in doing his/her job.

    Finally, we have seen good data from the U.S. Navy that showed that
    the contributing factors to low cost/no injury events were the same
    contributing factors to high cost/personal injury events. Thus,
    addressing the contributing factors to lower level events can
    prevent higher level events.

    **5. The MEDA Investigation Process**

    The purpose of this MEDA Users Guide is to provide information to
    the MEDA investigator. In order for the MEDA investigator to do
    his/her job correctly, he/she should understand their role as
    investigator within the whole investigation process. Figure 4 is a
    diagram of the MEDA investigation processes.

    Figure 4. The MEDA Investigation Process

    1\. MEDA is an event-based process. That is, a MEDA investigation is
    carried out after an event occurs in order to find out why the event
    occurred. However, before carrying out an MEDA investigation, we
    must know that a maintenance technician/inspector error caused or
    was partially causal to the event.

    2\. Therefore, after an event occurs, the next thing that is done is
    an initial investigation to determine whether there was an error
    that contributed to the event. If there was no error, an engineering
    investigation may continue in order to determine why some technical
    system failed (e.g., from metal fatigue or failure of electronic
    parts). If there was an error that caused or contributed to the
    event, then a MEDA investigation would follow.

    3\. The next thing that must be done is to find the maintenance
    technician or inspector who made the error.

    4\. Then you interview the maintenance technician/inspector, using
    the MEDA Results Form, in order to find out two things:

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-   What the contributing factors were to the error, and

-   What ideas the maintenance technician/inspector has for
    improving/fixing the contributing factors.

    Obviously, using the interview to understand the contributing
    factors to error is the primary purpose of the MEDA investigation.
    The maintenance technician/inspector is, at that time, probably the
    world's expert on the contributing factors to that specific error.
    It is your job to find out what those contributing factors are. In
    addition, the maintenance technician/inspector is also probably the
    world's expert on what changes need to be made to the contributing
    factors in order to keep them from contributing to future, similar
    errors. So, another task of the investigator is to get ideas for
    improvements to the contributing factors from the maintenance
    technician/inspector. Note that this helps make the erring
    maintenance technician/inspector part of the continuous improvement
    process, so they are no longer just "the person who made the error."

    5\. During the interview with the maintenance technician/inspector
    you may obtain information that requires follow-up in order to gain
    full knowledge about the contributing factors or other
    circumstances. This may include follow-up interviews with other
    maintenance technicians in the same work group, with production
    planners or with spares technicians. Or, it may include inspecting
    something like a tool that the maintenance technician said was hard
    to use or the lighting in a room where the maintenance technician
    said it hard to see a parts label.

    6\. Once all of the interviews/investigation has taken place, the
    Results Form data would be added to a database. Analysis can then be
    done to find trends in errors or contributing factors. This type of
    analysis will probably not be that useful until a number of
    investigations have been done---probably 20 or more---because trends
    might not be visible.

    7\. It is time to make improvements to the contributing factors.
    Management would typically make these types of decisions, since
    improvements to some contributing factors might cost money or
    manpower to implement. These decisions are often made at an existing
    meeting of managers, such as at the weekly/monthly QA audit findings
    meeting or the weekly/monthly management reliability findings
    meeting. Also, decisions about improvements might be made on the
    basis on one investigation, if there are obvious and relatively
    straightforward contributing factors that need to be fixed (like
    improved lighting or labeling). These decisions could also be made
    based on the analysis of several like events, if the improvements
    are less obvious or are expensive to make so that additional data
    are necessary to make a important, high-cost decision (like changing
    the shift handover procedure).

    8\. It is important to provide feedback to the maintenance
    technicians/inspectors to let them know what improvements are being
    made. This will show them that the process is being used to make
    improvements and is not being used to punish maintenance
    technicians.

    **6. Using the MEDA Results Form**

    The MEDA Results Form is a four-page form consisting of six
    sections:

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-   Section I---General Information

-   Section II---Event

-   Section III---Maintenance Error

-   Section IV---Contributing Factors Checklist

-   Section V---Error Prevention Strategies

-   Section VI---Summary of Contributing Factors, Error, and Event

    Sections I, II, and III establish what happened (the incident),
    Section IV establishes why the incident happened (the contributing
    factors), Section V lists the system barriers that failed to prevent
    the error and recommendations for prevention strategies to prevent
    the error from occurring again. Section VI is for a summary of the
    whole incident, including the contributing factors.

    **6.1 Section I. General**

    This section is for collecting specific information about when,
    where, and to what the incident occurred. Your organization may have
    other or additional information that should be collected. We
    encourage organizations to change this section in order to collect
    the information that is most useful to you. This information often
    includes the variables that you would like to use when you sort the
    data or summarize the data. For example, you may want to summarize
    the MEDA results as a function of airplane type, station of error,
    or ATA chapter.

    **Reference #:** Two letter airline designator plus three sequential
    numbers (e.g., BA001, BA002, etc.)

    **Airline:** Two or three letter airline designator

    **Station of Error:** Station [where the error occurred]{.underline}
    NOT where it is being reported (if different)

    **Aircraft Type:** Manufacturer and model (e.g., B747-400, DC10-30,
    L1011-100, A320-200)

    **Engine Type:** Manufacturer and model (e.g., PW4000, RB211-524,
    CF6-80A, etc.)

    **Reg. #:** Aircraft registration number

    **Fleet Number:** Letter or number designator

    **ATA #:** Can be used to collect the ATA chapter (e.g., 30-10) most
    closely related to the error under investigation or the specific
    task card number for the task that resulted in the error.

    **Aircraft Zone:** e.g., 210, 130, etc.

    **Ref. \# of previous related event (If applicable) :** If this
    investigation is a repeat of a similar event, use this field to
    reference to the previous investigation\'s data

    **Interviewer's Name/Interviewer's Telephone #:** This information
    is required in case the MEDA focal in your organization needs
    clarification or more detailed data

    **Date of Investigation:** Date the investigation starts

    **Date of Event:** Date the event occurred

    **Time of Event:** Time of the event, if known

    **Shift of Error:** Shift during which the error occurred, if known

    **Type of Maintenance:** Indicate whether the error occurred during
    line or base maintenance, and what type of check or maintenance was
    being performed (e.g., turnaround, A-Check, overhaul, etc.)

    **Date Changes Implemented:** Date that recommended and approved
    prevention strategies were implemented and documented

    **6.2 Section II. Event**

    An event is an unexpected, unintended, or undesirable occurrence
    that interrupts normal operations. MEDA can be used to investigate
    four major types of events:

1.  Events that interrupt the normal process of flying from point A to
    point B, like flight delays, gate returns, cancellations, etc.

2.  Aircraft damage events

3.  Personal injury events

4.  Finding that a task was not done correctly (e.g., through an
    inspection, functional test, or system failure during flight) which
    results in having to do the task a second time (rework).

    It is entirely possible that there is more than one event checked on
    the form. For example, oil loss may cause an in-flight engine
    shutdown that is followed by a diversion.

    **Step 1** in the Event section is to select the events that apply
    to this investigation.

    **Please select the event (check all that apply)**

    **1. Operations Process Event**

    ( ) a. Flight Delay \_\_\_days\_\_\_hrs.\_\_\_min.

    ( ) b. Flight Cancellation

    ( ) c. Gate Return

    ( ) d. In-Flight Shut Down

    () e. Air Turn-back

    ( ) f. Diversion

    ( ) g Other (explain below)

    **( ) 2. Aircraft Damage Event**

    **( ) 3. Personal Injury Event**

    **( ) 4. Rework**

    **( ) 5 Other Event (explain Below)**

    **Step 2** is to write a description of the
    incident/degradation/failure (e.g., could not pressurize) that
    caused the event in your own words. It is important that you not
    just check the box to indicate which event(s) occurred. You should
    write additional information in the blank space in the block.

    Example:

    *After takeoff, the aircraft would not pressurize in the automatic
    mode. Manual control was noted as functional.*

    **6.3 Section III. Maintenance Error**

    In the MEDA model, the maintenance error is the error that directly
    leads to the event. The errors that are listed are very specific
    errors related to maintenance technicians and inspectors. There are
    seven different major error types listed:

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1.  Installation error

2.  Servicing error

3.  Repair error

4.  Fault isolation, test, or inspection error

5.  Foreign object damage error

6.  Airplane/equipment damage error

7.  Personal injury error.

    An eighth box is provided for "Other" in case the specific error of
    interest was not listed in 1-7 above.

    **Step 1** is to select the type of maintenance error by putting a
    check mark () in the correct box or boxes. NOTE: Sometimes several
    errors combine to cause an incident. It is important to keep track
    of which contributing factors and error prevention strategies listed
    in Sections IV and V relate to which errors identified in
    Section III. This could be done in several ways. For example, you
    could fill out one Results Form for each error. Alternatively, you
    could check one error box with a red pencil and the second with a
    blue pencil. Then the factors that contributed to the first error
    could be written in red and the factors that contributed to the
    second error could be written in blue. Or, you could put a \* by the
    first error and a \# by the second error. Then you could place a \*
    by the factors that contributed to the first error and a \# by the
    factors that contributed to the second error.

    **Step 2** is to write a brief written description of the
    maintenance error in the open space below the errors.

    Example:

    *The auto pressure controller was installed with the sense lines
    backwards.*

    **6.4 Section IV. Contributing Factors Checklist**

    This checklist will help the analyst identify the contributing
    factors that contributed to the error. \[Remember, if two or more
    errors combined to cause the event, it is important to identify
    which factors relate to which error.\] There are ten major
    categories of contributing factors in the checklist:

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A.  Information

B.  Equipment, tools, and safety equipment

C.  Aircraft design, configuration, and parts

D.  The job or task

E.  Technical knowledge and skills

F.  Individual factors

G.  Environment and facility

H.  Organizational factors

I.  Leadership and supervision

J.  Communication

    There is also an eleventh category (K) "Other" that is to be used in
    case the contributing factor cannot be found in A through J. We
    included this category just in case the contributing factor was not
    found in the checklist. However, our experience to date is that the
    "Other" category is never used. That is, the ten categories have
    been inclusive of all contributing factors.

    **Step 1** is to put a check mark by all of the applicable
    contributing factors for the error(s) identified in Section III.

    **Step 2** is to provide a written description of how each factor
    that was identified actually contributed to the error in the open
    space in the contributing factors box.

    **Step 3** is to put a check mark by N/A (Not applicable), which is
    located to the left of each of the ten categories, if you determine
    that no contributing factors from that category contributed to the
    error(s).

    **Contributing Factors Checklist Examples**

    The following pages contain additional information about each
    contributing factor from Section IV of the MEDA Results Form. Each
    lettered section heading corresponds to a lettered block on the
    Results Form, and each numbered item beneath that heading
    corresponds to a numbered item on the Results Form. Use this
    supplemental material during your error analysis to assist you in
    filling out the Results Form.

    **6.4.A. Information**

    [Information]{.underline} refers to the written or computerized
    source data that a maintenance technician needs to carry out a task
    or job. It includes workcards, maintenance manual procedures,
    service bulletins or engineering orders, maintenance tips,
    illustrated parts catalogs and other manufacturer supplied or
    internal resources. Information does not include verbal instructions
    from supervisors, shift handover logs, etc., which are considered to
    be [Communication]{.underline} on the Results Form

    To determine that information was a contributing factor to the
    maintenance error, either the information itself must be
    problematical (e.g., hard to understand, not complete, conflicting),
    or the information should have been used but was not (e.g., it was
    not available, it was ignored). If it is expected that the
    maintenance technician has this information memorized, then refer to
    the [Technical Knowledge/Skills]{.underline} section.

    Examples to look for:

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1.  *Not understandable*

-   Unfamiliar words or acronyms

-   Unusual or non-standard format

-   Poor or insufficient illustrations

-   Not enough detail or missing steps

-   Poorly written procedures

2.  *Unavailable/inaccessible*

-   Procedure does not exist

-   Not located in correct or usual place

-   Not located near worksite

3.  *Incorrect*

-   Missing pages or revisions

-   Does not match aircraft configuration

-   Transferred from source document incorrectly

-   Steps out of sequence

-   Not the most current revision

-   Procedure does not work

4.  *Too much/conflicting information*

-   Similar procedures in different resources do not agree (e.g. MM
    versus task card)

-   Too many references to other documents

-   Configurations shown in different resources do not agree

5.  *Update process is too long/complicated*

-   Requested revisions have not been incorporated yet

-   Configurations changed by Service Bulletins or Engineering Orders
    have not been updated in applicable maintenance procedures

-   Document change requests are not submitted, lost, or incorrectly
    filled out

6.  *Incorrectly modified manufacturer\'s MM/SB*

-   Intent of manufacturer\'s procedure is not met

-   Non-standard practices or steps are added

-   Format does not match rest of procedure or other procedures

7.  *Information not used*

-   Procedure available but the technician did not have enough time to
    get it

-   Technician thought that he did not need the procedure because he had
    done the task many times before

8.  *Other*

-   Operator cannot use digital information

    **6.4.B. Equipment/Tools/Safety Equipment**

    [Equipment, tools and safety equipment]{.underline} are the tools
    and materials necessary for the safe performance of a maintenance
    task. Equipment and tools refer to things such as non-destructive
    test equipment, work stands, calibrated torque wrenches,
    screwdrivers, test boxes, and special tools called out in
    maintenance procedures. Safety equipment includes both personal
    protective equipment such as hard hats and safety harnesses as well
    as collective safety devices such as hazard barriers and safety
    railings.

    Unsafe equipment and tools may cause a maintenance technician to
    become distracted from the task due to concern for personal safety.
    If equipment or tools are not available or are inaccessible, the
    maintenance technician may use other equipment or tools that are not
    fully suited for the job. Other factors that can contribute to error
    include mis-calibrated instruments, use of unreliable equipment, or
    equipment or tools with no instructions for use.

    Examples to look for:

1.  *Unsafe*

-   Platform moves and is unstable

-   Brakes or safety devices inoperative

-   Non-skid material worn or missing

-   A lock-out mechanism is missing or faulty

-   Placards (warnings or cautions) are missing or faded

-   Sharp edges are exposed or personal protective devices are missing

-   Power sources are not labeled or protected

2.  *Unreliable*

-   Intermittent or fluctuating readings on dials or indicators

-   Damaged or worn out

-   Expired use limits

-   History of defects

3.  *Layout of controls or displays*

-   Easy to read wrong display or use wrong control

-   Awkward locations, hard to reach

-   Too small to read or control

-   Directional control of knobs or dials is not clear

4.  *Mis-calibrated*

-   Tool out of calibration from the start of use

-   Wrong specifications used during calibration procedure

5.  *Unavailable*

-   Is not owned or in stock

-   Not available for procurement

6.  *Inappropriate for the task*

-   Standard hand tools used for leverage

-   Not capable of handling weights, forces, or pressures required for
    the task

-   Connections or grips not the right size

7.  *Cannot be used in intended environment*

-   Not enough space to operate tool

-   Requires level surface where one is not available

8.  *No instructions*

-   Instructional placards missing or faded

-   Directional markings missing

-   Tool usage instructions not available

9.  *Too complicated*

-   Tool usage requires too many simultaneous movements and/or readings

-   Fault isolation or testing is too complex

10. *Incorrectly labeled*

-   Hand marked labeling or operating instructions are incorrect

-   Tool has incorrect scale readings

11. *Not used*

-   Equipment/tool/part is available but not used

-   Not all parts installed during multiple installation

12. *Incorrectly used*

-   Safety equipment not appropriate for the hazard

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-   Personal protective equipment not properly worn

13. *Other*

-   System protection devices on tools/equipment not available

    **6.4.C. Aircraft Design/Configuration/Parts**

    An aircraft should be [designed/configured]{.underline} so that
    parts and systems are accessible for maintenance. The maintenance
    technician should be able to see and reach a part, should be able to
    remove it from a reach and strength standpoint, and should be able
    to easily replace the part in the correct orientation. When
    reviewing accessibility as a contributor to maintenance error, it
    must be seen as a real contributor to the error and not just as an
    inconvenience to the maintenance technician.

    Configuration variability between models and aircraft can contribute
    to error when there are small differences between the configurations
    that require maintenance tasks to be carried out differently or
    require slightly different parts.

    [Parts]{.underline} refer to aircraft parts that are to be replaced.
    Incorrectly labeled parts can contribute to improper installation or
    repair. Parts that are unavailable can contribute to error by the
    maintenance technician who uses a substitute part.

    Good part design also incorporates feedback that helps the
    maintenance technician know that something has been performed
    correctly. For example, an electrical connector that has a ratchet
    effect provides feedback to the maintenance technician when the
    installation is correct. If this ratchet effect is included in some
    connectors and not others, this could contribute to error. If a
    maintenance technician goes from a ratchet connector to a
    non-ratchet connector, the technician may over tighten the second
    connector looking for the ratchet.

    Examples to look for:

1.  *Complex*

-   Fault isolation on the system or component is difficult

-   Installation of components is confusing, long, or error prone

-   Multiple similar connections exist on the system or component
    (electrical, hydraulic, pneumatic, etc.)

-   Installation tests for the component are extensive and confusing

-   Different sized fasteners can be installed in multiple locations

2.  *Inaccessible*

-   Components or area to be maintained is surrounded by structure

-   No access doors exist in the maintenance area

-   Area lacks footing space or hand-holds

-   Small or odd-shaped area

3.  *Aircraft configuration variability*

-   Similar parts on different models are installed differently

-   Aircraft modifications have changed installation or other
    maintenance procedures between aircraft

4.  *Parts unavailable*

-   Part not owned or in stock

-   Not available for procurement

    *5. Parts incorrectly labeled*

-   Hand marked labeling incorrect

-   Wrong part number on part

6.  *Easy to install incorrectly*

-   Can be easily installed with wrong orientation

-   No orientation indicators (e.g., arrow, colors)

-   Connections identical in size, color or length

7.  *Other*

-   Components are too heavy for easy removal/installation

-   Lack of feedback provided by component or system

-   Direction of flow indicators do not exist

    **6.4.D. Job/Task**

    A maintenance technician\'s [job/task]{.underline} can logically be
    separated into a series of tasks. If the interviewer feels the task
    was a contributing factor, he should analyze the combination or
    sequence of tasks. The interviewer, when examining the task
    sequencing, should also determine whether written information was
    being used, what technical skills and knowledge were expected of the
    maintenance technician, and what communication took place.

    Examples to look for:

1.  *Repetitive/monotonous*

-   Similar steps are performed over and over (opening and closing
    circuit breakers during a long test)

-   The same task performed many times in multiple locations (removing
    seats)

2.  *Complex/confusing*

-   Multiple other tasks are required during this task

-   Multiple steps required at the same time by different maintenance
    technicians

-   Long procedure with step sequences critical

-   System interacts with other systems during testing or fault
    isolation

-   Multiple electrical checks are required

-   Task requires exceptional mental or physical effort

3.  *New task or task change*

-   New maintenance requirement or component

-   Revision to a procedure

-   Engineering modification to existing fleet

-   New aircraft model

4.  *Different from other similar tasks*

-   Same procedure on different models is slightly different

-   Recent change to aircraft configuration has slightly changed task

-   Same job at different worksites is performed slightly different

5.  *Other*

-   The workgroup performs the task differently than specified in the
    source data (or written information)

    **6.4.E. Technical Knowledge/Skills**

    [Technical skills]{.underline} (sometimes also referred to as
    abilities) refer to tasks or subtasks that maintenance technicians
    are expected to perform without having to refer to other
    information. Technical skills include such things as being able to
    lock wire, use a torque wrench, and remove common parts from an
    aircraft. For (lack of) technical skills to be a contributing factor
    to error, the technician must not have skill that was generally
    expected of him/her.

    [Technical knowledge]{.underline} refers to the understanding of a
    body of information that is applied directly to performing a task.
    Technical knowledge, in order to be a contributing factor to error,
    is knowledge that is supposed to be known (memorized) by the
    maintenance technician. Three broad categories of knowledge are
    required of a technician: airline process knowledge, aircraft
    systems knowledge, and maintenance task knowledge. These are
    discussed in more detail below.

    [Airline process]{.underline} knowledge refers to knowledge of the
    processes and practices of the airline or repair station in which
    the maintenance technician works. Examples include shift handover
    procedures, parts tagging requirements, and sign off requirements.
    While this knowledge is generally acquired through general
    maintenance operating procedures and on-the-job discussion with
    peers, it may also be acquired from other sources such as employee
    bulletins and special training.

    [Aircraft system]{.underline} knowledge refers to knowledge of the
    physical aircraft systems and equipment. Examples include location
    and function of hydraulic pumps and rework options for corroded or
    fatigued parts. While this knowledge is generally acquired from the
    aircraft design characteristics, training, maintenance manuals, and
    on-the-job discussion with peers, it may also be acquired from other
    sources such as trade journals and maintenance tips.

    [Maintenance task knowledge]{.underline} refers to the specific
    knowledge required to perform a unique task. Examples include the
    procedure for bleeding a hydraulic system and for measuring tire
    wear. While this knowledge is generally acquired through maintenance
    instructions or on-the-job discussions with peers, it may also be
    acquired from aircraft placards, design characteristics, or even
    other maintenance technicians when working as a team.

    Examples to look for:

1.  *Skills*

-   Safety wiring

-   Rigging of controls

-   Using calibrated equipment

-   Carrying out a fault isolation task

    *2. Task knowledge*

-   Slow task completion

-   Technician change of maintenance responsibilities

-   Task performed by maintenance technician for the first time

-   Task performed in wrong sequence

3.  *Task planning*

-   Frequent work interruptions to get tools or parts

-   Failure to perform preparation tasks first

-   Too many tasks scheduled for limited time period

-   Task necessary for safety not performed first

4.  *Airline process knowledge*

-   Failure to acquire parts on time

-   Technician new to airline or to type of work (from line to hangar,
    etc.)

-   Airline processes not documented or stressed in training

5.  *Aircraft system knowledge*

-   Technician changes aircraft types or major systems

-   Fault isolation takes too much time or is incomplete

6.  *Other*

-   Technician performance/skills not accurately tracked/measured

    **6.4.F. Individual Factors**

    [Individual factors]{.underline} vary from person to person and
    include body size/strength, health, and personal events and the way
    that a technician responds to things such as peer pressure, time
    constraints, and fatigue caused by the job itself.

    [Physical health]{.underline} includes the acuity of human senses as
    well as physical conditions and physical illnesses. Human senses,
    especially vision, hearing, and touch, play an important role in
    maintenance. Technicians are frequently required to perform tasks
    that are at or near the limits of their sensory capabilities. For
    example, some tasks require good vision and/or touch, such as visual
    inspection for cracks or finger inspection for burrs. Good hearing
    is also required in order to hear instructions or feedback before
    and during a maintenance task.

    Physical conditions, such as headaches and chronic pain, also have
    been shown to relate to errors. Alcohol/drug use, as well as side
    effects of various prescription and over-the-counter medicines, can
    negatively affect the senses. Physical illness, such as having a
    cold or the flu, can also negatively affect the senses and the
    ability to concentrate. Illnesses can also lead to less energy,
    which can affect fatigue.

    [Fatigue]{.underline} has been defined by the U.S. Federal Aviation
    Administration (FAA) as a depletion of body energy reserves, leading
    to below-par performance. Fatigue may be emotional or physical in
    origin. Acute fatigue may be caused by emotional stress, depletion
    of physical energy, lack of sleep, lack of food, poor physical
    health, or over excitement. Fatigue may also be caused by the work
    situation itself. The time of the day, the length one has been
    working, and complex mental tasks or very physical tasks can cause
    fatigue.

    A technician's response to [time constraints]{.underline} or time
    \"pressure\" is an individual factor. The need to finish a
    maintenance task so an aircraft can be released from the gate or to
    finish a heavy maintenance task so an aircraft can be put back into
    service often cause technicians to feel pressure to get their tasks
    done. Studies have linked too little time with increased error.
    There is a well-known speed/accuracy trade-off, in that the faster
    one tries to finish a task the more likely an error is to happen.
    This trade-off also holds for speed and safety.

    A technician's response to [peer pressure]{.underline} can also
    influence a their performance. For example, there may be peer
    pressure not to use maintenance manuals because it is seen as a sign
    of lack of technical knowledge. Peer pressure may also influence a
    technician\'s safety-related behavior.

    [Complacency]{.underline} is over-contentment with a situation that
    may lead to a failure to recognize cues that indicate a potential
    error.

    [Body size and strength]{.underline} are two obvious factors that
    affect a maintenance technician\'s ability to perform a task. If
    someone is too small to reach a plug or if someone is unable to let
    down an LRU from an upper rack, this can contribute to error.

    Examples to look for:

1.  *Physical health*

-   Sensory acuity (e.g. vision loss, hearing loss, touch)

-   Failure to wear corrective lenses

-   Failure to use hearing aids or ear plugs

-   Restricted field of vision due to protective eye equipment

-   Pre-existing disease

-   Personal injury

-   Chronic pain limiting range of movement

-   Nutritional factors (missed meals, poor diet)

-   Adverse affects of medication

-   Drug or alcohol use

-   Complaints of frequent muscle/soft tissue injury

-   Chronic joint pain in hands/arms/knees

2.  *Fatigue*

-   Lack of sleep

-   Emotional stress (e.g. tension, anxiety, depression)

-   Judgment errors

-   Inadequate vigilance, attention span, alertness

-   Inability to concentrate

-   Slow reaction time

-   Significant increase in work hours or change in conditions

-   Excessive length of work day

-   Excessive time spent on one task

-   Chronic overloading

-   Task saturation (e.g., inspecting rows of rivets)

3.  *Time constraints*

-   Constant fast-paced environment

-   Multiple tasks to be performed by one person in a limited time

-   Increase in workload without an increase in staff

-   Too much emphasis on schedule without proper planning

-   Perceived pressure to finish a task more quickly than needed in
    order to release the aircraft from the gate

4.  *Peer pressure*

-   Unwillingness to use written information because it is seen as a
    lack of technical skills/knowledge

-   Lack of individual confidence

-   Not questioning other\'s processes

-   Not following safe operating procedures because others don\'t follow
    them

5.  *Complacency*

-   Hazardous attitudes (invulnerability, arrogance, over-confidence)

-   Task repetition leads to loss of mental sharpness or efficiency

    *6. Body size/strength*

-   Abnormal reach, unusual fit, or unusual strength required for the
    task

-   Inability to access confined spaces

7.  *Personal event*

-   Death of a family member

-   Marital difficulties

-   Change in health of a family member

-   Change in work responsibilities/assignment

-   Change in living conditions

    *8. Workplace distractions/interruptions during task performance*

-   Confusion or disorientation about where one is in a task

-   Missed steps in a multi-step task

-   Not completing a task

-   Working environment is too dynamic

    *9. Memory lapse*

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-   Forgot

10. *Other*

-   Absenteeism

-   Vacations

-   Medical leave

-   Risk-taking behavior

    **6.4.G. Environment/Facilities**

    The working [environment/facilities]{.underline} can contribute to
    error. For example, temperature extremes (either too hot or too
    cold), high noise levels, inadequate lighting (reflection/glare,
    etc.), unusual vibrations, and dirty work surfaces could all
    potentially lead to maintenance errors. Concerns about health and
    safety issues could also contribute to maintenance technician
    errors.

    Examples to look for:

1.  *High noise levels*

-   High noise impacts the communication necessary to perform a task

-   Extended exposure to noise reduces ability to concentrate and makes
    one tired

-   Noise covers up system feedback during a test

    *2. Hot*

-   Work area is too hot so the task is carried out quickly

-   Extremely high temperatures cause fatigue

-   Long exposure to direct sunlight

-   Exterior components or structure too hot for maintenance technicians
    to physically handle or work on

    *3. Cold*

-   Work area is too cold so the task is carried out quickly

-   Long exposure to low temperature decreases sense of touch and smell

    *4. Humidity*

-   High humidity creates moisture on aircraft, part and tool surfaces

-   Humidity contributes to fatigue

    *5. Rain*

-   Causes obscured visibility

-   Causes slippery or unsafe conditions

    *6. Snow*

-   Causes obscured visibility

-   Causes slippery or unsafe conditions

-   Protective gear makes grasping, movement difficult

    *7. Lighting*

-   Insufficient for reading instructions, placards, etc.

-   Insufficient for visual inspections

-   Insufficient for general maintenance activity

-   Excessive - creates glare, reflection, or eye spotting

    *8. Wind*

-   Interferes with ability to hear and communicate

-   Moves stands and other equipment (creates instability)

-   Blows debris into eyes, ears, nose or throat

-   Makes using written material difficult

    *9. Vibrations*

-   Use of power tools fatigues hands and arms

-   Makes standing on surfaces difficult

-   Makes instrument reading difficult

    *10. Cleanliness*

-   Loss of footing/grip due to dirt, grease or fluids on parts/surfaces

-   Clutter reduces available/usable work space

-   Inhibits ability to perform visual inspection tasks

11. *Hazardous/toxic substances*

-   Reduces sensory acuity (e.g. smell, vision)

-   Exposure causes headaches, nausea, dizziness

-   Exposure causes burning, itching, general pain

-   Personal protective equipment limits motion or reach

-   Exposure causes general or sudden fatigue

-   Exposure causes general concern about long term effect on health

12. *Power sources*

-   Not labeled with caution or warning

-   Guarding devices missing or damaged

-   Power left on inappropriately

-   Circuit protection devices not utilized or damaged

-   Cords chafed, split, or frayed

13. *Inadequate ventilation*

-   Strong odor present

-   Burning or itching eyes

-   Shortness of breath

-   Sudden fatigue

14. *Other*

-   Area(s) not organized efficiently (difficult to find parts, work
    cards, etc.)

-   Area too crowded with maintenance technicians and/or other personnel

    **6.4.H. Organizational Factors**

    The [organizational]{.underline} culture can have a great impact on
    maintenance error. Factors such as internal communication with
    support organizations, trust level between management and
    maintenance technicians, management goals and technician awareness
    and buy-in of those goals, union activities, and attitudes, morale,
    etc., all affect productivity and quality of work. The amount of
    ownership the technician has of his/her work environment and the
    ability to change/improve processes and systems is of key importance
    to technician morale and self esteem, which in turn, affects the
    quality of task performance.

    Examples to look for:

1.  *Quality of support from technical organizations*

-   Inconsistent quality of support information

-   Late or missing support information

-   Poor or unrealistic maintenance plans

-   Lack of feedback on change requests

-   Reluctance to make technical decisions

-   Frequent changes in company procedures and maintenance programs

2.  *Company policies*

-   Unfair or inconsistent application of company policies

-   Standard policies do not exist or are not emphasized

-   Standard error prevention strategies don\'t exist or are not applied

-   Inflexibility in considering special circumstances

-   Lack of ability to change or update policies

3.  *Not enough staff*

-   *Not enough trained personnel*

-   *Not enough trained personnel at the time*

4.  *Corporate change/restructuring*

-   Layoffs are occurring

-   Early retirement programs drain experience

-   Reorganizations, consolidations and transfers cause more people to
    be in new jobs

-   Demotions and pay cuts

-   Frequent management changes

5.  *Union action*

-   Contract negotiations create distractions

-   Historical management/labor relations are not good

-   Positive or negative communication from union leadership

-   Strike, work slowdown, or other labor action creates a disruption

6.  *Work process/procedure*

-   Standard operating procedures (SOPs) incorrect

-   General maintenance manuals outdated

-   Local/organizational "norms" negatively influence the task

-   Inadequate inspection allowed

-   Process/procedure does not obtain the desired outcome

7.  *Work process/procedure not followed*

-   *Skipped operational check*

-   *Required protective equipment not used*

-   *Did not use "parts removed" tag*

8.  *Work process/procedure not documented*

-   *No procedure for radio check before towing operation*

-   *No inspection criteria*

-   *No procedure for proper use of safety equipment*

9.  *Work group normal practice (norm)*

-   *Documented procedure -- most people don't do it*

-   *Undocumented procedure -- most people do it*

10. *Other*

-   Company is acquired by another company

-   Work previously accomplished in-house is contracted out

-   Overall inadequate staffing levels

    **6.4.I. Leadership/Supervision**

    Even though [supervisors]{.underline} normally do not perform the
    tasks, they can still contribute to maintenance error by poor
    planning, prioritizing, and organizing of job tasks. Delegation of
    tasks is a very important supervisory skill and if not done
    properly, can result in poor work quality. Also, there is a direct
    link between the management/supervisory attitudes and expectations
    of the maintenance technician and the quality of the work that is
    performed.

    Supervisors and higher-level management must also provide
    [leadership]{.underline}. That is, they should have a vision of
    where the maintenance function should be headed and how it will get
    there. In addition, leadership is exhibited by management \"walking
    the talk\", that is, showing the same type of behavior expected of
    others.

    Examples to look for:

1.  *Planning/organization of tasks*

-   Excessive downtime between tasks

-   Not enough time between tasks

-   Paperwork is disorganized

-   Tasks are not in a logical sequence

2.  *Prioritization of work*

-   Technicians not told which tasks to carry out first

-   Important or safety related tasks are scheduled last

-   Fault isolation is not performed with the most likely causes checked
    first

3.  *Delegation/assignment of tasks*

-   Assigning the wrong person to carry out a task

-   Inconsistency or lack of processes for delegating tasks

-   Giving the same task to the same person consistently

-   Wide variance in workload among maintenance technicians or
    departments

4.  *Unrealistic attitude/expectations*

-   Frequent dissatisfaction, anger, and arguments between a supervisor
    and a technician about how to do a task or how quickly a task should
    be finished

-   Pressure on maintenance technicians to finish tasks sooner than
    possible or reasonable

-   Berating individuals, especially in front of others

-   Zero tolerance for errors

-   No overall performance expectations of maintenance staff based on
    management vision

5.  *Amount of supervision*

-   \"Look over the shoulder\" management style

-   Frequent questioning of decisions made

-   Failure to involve employees in decision-making

6.  *Other*

-   Meetings do not have purpose or agendas

-   Supervisor does not have confidence in group\'s abilities

-   Management doesn\'t \"walk the talk\" and thereby sets poor work
    standards for maintenance staff

    **6.4.J. Communication**

    [Communication]{.underline} refers to the transfer of information
    (written, verbal, or non-verbal) within the maintenance
    organization. A breakdown in communication can prevent a maintenance
    technician from getting the correct information in a timely manner
    regarding a maintenance task.

    Examples to look for:

1.  *Between departments*

-   Written communication incomplete or vague

-   Information not routed to the correct groups

-   Department responsibilities not clearly defined or communicated

-   Personality conflicts create barriers to communication between
    departments

-   Information not provided at all or not in time to use

2.  *Between mechanics*

-   Failure to communicate important information

-   Misinterpretation of words, intent or tone of voice

-   Language barriers

-   Use of slang or unfamiliar terms

-   Use of unfamiliar acronyms

-   Failure to question actions when necessary

-   Failure to offer ideas or process improvement proposals

-   Personality differences

3.  *Between shifts*

-   Work turnover not accomplished or done poorly or quickly

-   Inadequate record of work accomplished

-   Processes not documented for all shifts to use

-   Job boards or check-off lists not kept up to date

4.  *Between maintenance crew and lead*

-   Lead fails to communicate important information to crew

-   Poor verbal turnover or job assignment at the beginning of a shift

-   Unclear roles and responsibilities

-   Lead does not provide feedback to crew on performance

-   Crew fails to report problems and opportunities for improvement to
    lead person

-   Communication tools (written, phones, radios, etc.) not used

5.  *Between lead and management*

-   Little or no communication exists

-   Goals and plans not discussed regularly

-   No feedback from management to lead on performance

-   Lead does not report problems and opportunities for improvement to
    management

-   Management fails to communicate important information to lead

6.  *Between flight crew and maintenance*

-   Late notification of defect

-   ACARS/data downlink not used

-   MEL/DDG interpretation problem

-   Logbook write-up vague or unclear

7.  *Other*

-   Computer or network malfunctions lead to loss of information

-   E-mail not used or ignored

    **6.4.K. Other Contributing Factors**

    This section was put into the Users Guide in case a MEDA
    investigator found a contributing factor that did not fit into one
    of the ten contributing factors categories. During the field test of
    the Results Form, several investigators used Section K. However,
    upon inspection of what they wrote into the section, they had
    clearly failed to put the contributing factor into the correct
    category A-J that was already on the form. This suggested that the
    training needed to be improved.

    Since the field test, we have never seen the "Other" category used,
    but we have left it on the form just in case there may be a need
    some day.

    **6.5 Section V. Error Prevention Strategies**

    This section is subdivided into two subsections. The purpose of
    Section A is to indicate organizational barriers that were in place
    but failed to prevent the error from occurring.

    **Section A asks, *"What current existing procedures, processes,
    and/or policies in your organization are intended to prevent the
    incident, but didn't?" ***

    The investigator needs to think about which of the listed items were
    involved or contributed to the error. For example, if a maintenance
    policy was not a good policy or was not followed, then you would
    check "Maintenance Policies or Processes" and write in which policy
    was not good or not followed. If an inspection was performed, but
    the inspector missed the fault, and the fault later caused the
    event, then you would check "Inspection or Functional Check" and
    indicate what the inspection was.

    **Section B asks, *"List recommendations for error prevention
    strategies."***

    This section has three columns. The left most column
    (Recommendation #) is for you to put a serial number (1, 2, 3, etc.)
    in order to simply number the recommendation, so that it is easier
    to refer to it. The middle column (Contributing Factor #) is for you
    to put the number of the contributing factor that you are addressing
    (e.g., A.1. for Information Not Understandable). The right most
    column is for you to write in the proposed improvement to be made to
    the contributing factor that you listed (e.g., rewrite the third
    step in the engineering order to make clear what the torque values
    are supposed to be).

    **Types of Error Prevention Strategies**

    In order to help you think through Error Prevention Strategies, the
    following material describes the four major types of strategies that
    you should consider:

1.  Error reduction/error elimination

2.  Error capturing

3.  Error tolerance

4.  Audit programs.

    These strategies are discussed in more detail below.

    Often, the individual error investigation does not yield
    contributing factors with strong linkages to the error under
    investigation. Sometimes the effect of certain contributing factors
    is not fully understood until a number of events are investigated
    with the same contributing factor(s) related to them. The difficulty
    for the front-line manager performing an investigation is the
    pressure to take action resulting from a single event investigation.
    The dilemma, however, is how to decide on a prevention strategy when
    you do not have any strong identifiable contributing factors leading
    to the error. What if the error had safety implications? Somehow,
    the error must be addressed.

    **Error Reduction/Error Elimination**

    The most often used, and most readily available, error prevention
    strategies are those that directly reduce or eliminate the
    contributing factors to the error. Examples include increasing
    lighting to improve inspection reliability and using Simplified
    English procedures to reduce the potential for mis-interpretation.
    These error prevention strategies try to improve task reliability by
    eliminating any adverse conditions that have increased the risk of
    maintenance error.

    **Error Capturing**

    Error capturing refers to tasks that are performed specifically to
    catch an error made during a maintenance task. Examples include a
    post task inspection, an operational or functional test, or a
    verification step added to the end of a long procedure. Error
    capturing is different than error reduction in that it does not
    directly serve to reduce the \"human error\". For example, adding a
    leak check does little to reduce the probability of a mis-installed
    chip detector. It does, however, reduce the probability that an
    aircraft will be dispatched with a mis-installed chip detector. This
    is why most regulatory authorities require a subsequent inspection
    of any maintenance task that could endanger safe operation of the
    aircraft if performed improperly.

    While error capturing is an important part of error management, new
    views point to a general over-confidence in the error capturing
    strategy to manage maintenance error. In theory, adding a post-task
    inspection will require two human errors to occur in order for a
    maintenance-induced discrepancy to make it onto a revenue flight. In
    recent years, however, there has been a growing view that the
    additional inspection to ensure the integrity of an installation
    will adversely impact the reliability of the basic task. That is,
    humans consciously or subconsciously relax when it is known that a
    subsequent task has been scheduled to \"capture\" any errors made
    during the primary task. It is not unusual to hear an airline
    manager say that the addition of an inspection did little to reduce
    the in-service experience of the error. For example, several major
    carriers are pulling inspections out of scheduled line-maintenance
    tasks, in the hopes of improving quality.

    **Error Tolerance**

    Error tolerance refers to the ability of a system to remain
    functional even after a maintenance error. The classic illustration
    of this is the 1983 Eastern Airlines loss of all three engines due
    to O rings not installed on the chip detectors. As a strategy to
    prevent the loss of multiple engines, most regulatory authorities
    granting ETOPS (extended twin operations) approval prohibit the
    application of the same maintenance task on both engines prior to
    the same flight. The theory is that even if a human error is made,
    it will be limited to only one engine. This was not the case in the
    Eastern loss of all three engines. One type of human error, the same
    incorrect application of a task applied to all three engines, nearly
    caused an aircraft to be lost.

    Another example of building error tolerance into the maintenance
    operation is the scheduled maintenance program for damage tolerant
    structures (allowing multiple opportunities for catching a fatigue
    crack before it reaches critical length).

    Error tolerance, as a prevention strategy, is often limited to areas
    outside the control of the first line investigator. However, it is
    important for the first line supervisor or interviewer to be aware
    of this type of prevention strategy, and consider it when it may be
    the best way to effectively deal with the error.

    **Audit Programs**

    Audit programs refer to an approach that does not to directly
    address a specific contributing factor. An audit is a high-level
    analysis of the organization to see if there are any systemic
    conditions that may contribute to error.

    **6.6 Section VI Summary of Contributing Factors, Error, and Event**

    The purpose of this section is to provide you with some space to
    write out a brief summary of what happened and what you found
    regarding contributing factors during the interview. If there is not
    enough room provided, continue the description on another piece of
    paper and submit it with the rest of the Results Form.

    **7. How to Carry Out the MEDA Investigation Interview**

    By now it should be clear that the most important part of the
    investigation is the interview with the erring maintenance
    technician/inspector in order to find out the contributing factors
    to the error. Interviewing is a skill just like using a torque
    wrench is a skill. You will get better at interviewing the more
    interviews that you carry out. There are two purposes of this
    section:

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1.  To discuss who should be on the interview team

2.  To provide guidelines for how to carry out the interview,

3.  To provide some specific rules of causation, and

4.  To discuss interviewer biases, so that the interviewer can try to
    overcome them.

    **7.1 The MEDA Interview Team**

    How many people should be on the interview team? We have seen
    successful programs use 1 or 2 people on the interview team. How do
    you decide how many people to use?

    The advantage of one person doing the interview is that one person
    is typically less threatening to the technician than several people.
    However, this person must be a good interviewer, since he has to do
    all of the work himself. You may find that you start off with a
    2-person interview team, but as the interviewers gain experience,
    you can move to a smaller team.

    The advantage of a 2-person team is that one person can be asking
    questions while the second person is writing down information. In
    addition, the second person may think of additional questions to
    ask. When an organization first implements MEDA, they often start
    with a 2-person interview team.

    We typically suggest that 3 people are too many on the interview
    team. The technician could start to feel outnumbered, and,
    therefore, uncomfortable and unwilling to tell everything that he
    knows. However, a 2-person team with a union observer has proven
    useful at unionized maintenance organizations. The union observers
    job is to let the maintenance technician know that the union
    supports the MEDA process and to encourage the maintenance
    technician to cooperate during the interview.

    Who should be on the interview team? First, whoever is on the team
    should have some form of MEDA training. Hopefully, that is training
    provided by Boeing, but it could be training provided by your
    training organization. Even if you receive the Boeing training,
    additional training on interviewing is helpful, especially if the
    training includes practice at interviewing that is possibly
    videotaped for audio and visual feedback.

    The organization that is responsible for the MEDA process at the
    maintenance organization should be most concerned that good
    information is being gained from the MEDA investigations. Perhaps
    the best way to make sure good information is being collected is for
    the organization to assign one of their members as a MEDA
    investigation team member so they can make sure quality interviews
    are being carried out. Therefore, the team should include a person
    from this organization. So, for example, if QA "owns" the process,
    one of the interviewers would be a QA auditor.

    A second team member could be a respected, senior maintenance
    technician from the area where the error occurred. This person
    should bring two things, in addition to interviewing skills, to the
    interview:

-   He should have the respect of the maintenance technician being
    interviewed

-   He should be technically knowledgeable about the work that was being
    done when the error occurred.

    One person should act as the team leader. This most likely would be
    the person from the organization that "owns" the process. His job
    would be to introduce the team members, lead off on the questioning,
    keep the interview moving if it starts to bog down, make sure that
    everybody gets to ask questions, end the interview when no more
    useful information is forthcoming, and thank the maintenance
    technician for providing the information.

    **7.2 Guidelines for the MEDA Investigation Interview**

    Once the team has been chosen, it is time to carry out the MEDA
    investigation interview. We suggest eight steps for carrying out the
    interview. They are:

1.  Get as much information as possible about the error and the event
    before the interview

2.  Interview people separately if more than one person is involved

3.  Interview in an appropriate place

4.  Put the person being interviewed (the interviewee) at ease

5.  Determine the interviewee's knowledge of the MEDA process

6.  Get the interviewee's view of what happened

7.  Give the interviewee some feedback on what they said

8.  End on a positive note.

    These eight steps are described in more detail below.

    1\. Before carrying out the interview, gather as much information as
    possible about what happened. Going into the interview, you should
    know the event that started the investigation, and you will probably
    know what the error was that caused the event. If any engineering
    investigations have taken place, read that information, also, before
    the interview.

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2.  Many times there will only be one technician to interview, so this
    would not be an issue. However, if more than one technician was
    involved in the error, they should each be interviewed, and the
    interviews should be done separately. You are not doing this to see
    if you can catch someone up in a lie. You are doing this so that one
    technician doesn't influence the information provided by a second
    (or third, etc.) technician. No one has perfect memory, so one
    person's statement could influence what a second person said ("I
    don't really remember what happened, so Joe's view must be
    correct"). If you find that you get wildly differing stories from
    the technicians, follow-up interviews may need to be conducted.

3.  It is important where the interview takes place. It should be an
    area that is quiet so that you can talk easily with the person. It
    is also helpful if you can find a place so that you can sit down to
    carry out the interview. It should be a place where the interviewer
    and the interviewee can talk as two people on an equal level. Try
    not to carry out the interview with you sitting behind a
    supervisor's desk and the technician sitting in a chair in front of
    the desk. This will appear to the interviewee to put him on a lower
    personal level (employee vs. supervisor), and the interview could
    start to feel like an interrogation or cross-examination to the
    technician.

    4\. It is very important that you put the technician at ease for the
    interview. If the technician is worried about the incident, it may
    affect his memory and willingness to answer certain questions.

    a\. Put yourself in their position---they probably feel that the
    incident reflects poorly on them and they may be concerned about
    punishment.

    b\. So, you need to act relaxed and use a neutral tone of voice in
    the interview.

    c\. To maintain the feeling of equality, the interviewer's and
    interviewee's eyes should be on the same level (for example, the
    interviewer should not be standing while the interviewee is
    sitting).

    d\. The interviewer should also use neutral body language---that is,
    arms and legs should not be crossed.

    e\. Look the technician in the eyes while asking questions. Act like
    you would act when you're talking to your friends.

    f\. Finally, respond in a positive manner. If someone says that they
    had trouble understanding the maintenance manual, say something
    like, "Yeah, those manuals are sometimes hard to understand." Don't
    say something like, "Nobody else has that problem," or "Boy, I'd
    never do that." Those are not positive responses.

    5\. In order to help put the person at ease, determine their
    knowledge about the MEDA process. Ask them what they know about
    MEDA.

    a\. If they say that they are familiar with the process, then ask
    them to explain to yo what they know about MEDA. Then correct any
    misperceptions that they might have and provide additional
    information to them, as necessary.

    b\. If they say they have not heard about MEDA, then take a few
    minutes explaining fully about the MEDA process and philosophy.

    c\. The technician may be afraid that they will be punished for
    making the error and might ask you about it. If they do, tell them
    that you are not involved with decisions about punishment. Your job
    is to gather the facts, not make punishment decisions.

    6\. Get the technicians version of what happened. Start the
    interview with, "Would you please tell me about what was happening
    before and during the time leading to the error." Then let them talk
    about what happened.

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a.  Do not interrupt unless the person gets off the topic.

b.  Do not use a tape recorder, but use the MEDA Results Form to write
    down notes about possible contributing factors.

c.  When the technician has told you what he knows, then ask specific
    questions about contributing factors that you think you heard him
    talk about when he was telling you what happened.

d.  Review the other contributing factors categories to make sure that
    they were not contributory to the error.

e.  Do not ask questions or make statements that lead the interviewee,
    like, "After that, you probably went to the other side to see if the
    fastener had broken off. Correct?"

f.  Don't ask questions that put the interviewee on the defensive, like,
    "So how long after that stupid decision did you wait to talk to your
    supervisor?"

g.  Try to ask questions that require more than a simple yes or no
    answer.

h.  Again, don't make statements of judgment, like

-   That was stupid.

-   I would never do that.

-   No technician that I know of has ever done that.

-   You did WHAT!?!

    Those types of statements will quickly shut the interview down.

7.  Give the person feedback on what they said. The purpose of this is
    to make sure you heard/interpreted what the technician said
    correctly. Use the [paraphrase]{.underline} to do this. Put the key
    points in your own words and say, "I think that I heard you say that
    (x is the case)." The word "think" is very important here, because
    it gives them the opening to disagree with what you said. This
    process also shows active listening, which is also a very important
    communication tool.

    8\. End the interview on a positive note.

    a.  One way to do this is to ask the technician to help you think
        through possible corrective actions for the contributing factors
        that were uncovered in the interview. Now the technician is part
        of the improvement process rather than just the person who
        committed the error that lead to the event.

    b.  Thank them for their time and the useful information.

    c.  Commit to giving them feedback about possible corrective
        actions. Feedback helps to show the technicians that you are
        using the MEDA process to solve problems rather than to punish
        technicians.

        Often contributing factors themselves have causes that are
        important to an investigation. For example, you may determine
        that one contributing factor to a technician error was that the
        technician did not use the maintenance manual while carrying out
        the task. It is important to find out why he did not use the
        manual, so find out the contributing factors to that decision.
        Maybe he didn't use the manual because:

-   It was unavailable because the manuals are all on microfiche and the
    microfiche printer did not work.

-   It was too far away to get in time to use for unscheduled (ramp)
    maintenance

-   The technician thought that he had done the task often enough that
    he didn't need the manual.

    Note that the various reasons why the manual was not used have
    widely differing corrective actions. If you do not find out why the
    manual was not used, you will have difficulty in coming up with an
    appropriate corrective action.

    A commonly given "rule of thumb" is to "ask why five times." This
    will help assure that you would get the whole contributing factors
    causal chain. Then what you look for is the correct level to stop
    asking "why." For example:

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-   Person says that they did not use the maintenance manual. Find out
    why...

    -   Not available (find out why)

        -   The manuals were only on microfiche, and the microfiche
            printer was not working. Stop asking "why" here, because it
            is not the maintenance technician's issue why the printer
            was broken

    -   Ramp maintenance area was not close to manuals, so maintenance
        technician did not have enough time to get the manual. Keep
        asking questions\...

        -   Ask about time constraints (when was the flight out?) and

        -   The trade-off the maintenance technician made on working
            without manual vs. turning aircraft in time (what is their
            training on this and what is the company policy).

    -   Decided not to use (find out why)

    -   Had done the task a lot, so did not think he needed manual. Keep
        asking questions...

        -   Ask how often he has done the task

        -   Ask when the last time was he did the task.

            **7.3 Rules of Causation**

            Filling out the MEDA Results Form correctly, so that the
            collected information provides maximum value to the
            organization, is not an easy task. We have found that if the
            interviewer keeps four "rules of causation" in mind, then
            the task can be made easier. These rules are:

            Rule 1---The relationship between the contributing factor
            and the error must be clearly written down.

            Rule 2---Negative descriptors, such as "poorly" or
            "inadequate," may not be used.

            Rule 3---Each procedural deviation must have a preceding
            contributing factor.

            Rule 4---Failure to act is only a contributing factor when
            there is a pre-existing duty to act.

            Let us discuss these in a little more detail.

            **Rule 1---The relationship between the contributing factor
            and the error must be clearly written down.**

            This is one of the most important rules for filling out the
            MEDA Results Form. You must write in the appropriate
            contributing factors section how the contributing factors
            that you checked actually contributed to the error.

            **Rule 2---Negative descriptors, such as "poorly" or
            "inadequate," may not be used.**

            If you just say that something was done "poorly" in "in an
            inadequate fashion," it is not clear what the corrective
            action is. Saying that the maintenance manual was written
            "poorly" does not tell someone how to rewrite the manual. We
            must be specific about what the real issue is. For example,
            "The maintenance technician was working in the vertical tail
            fin of the aircraft, and the task required that he face
            towards the rear of the aircraft. The maintenance manual
            tells him to "loosen the left bolt" (of two bolts side by
            side). The technician loosened the bolt on his left, but the
            maintenance manual was actually referring to 'aircraft
            left.'"

            **Rule 3---Each procedural deviation must have a preceding
            contributing factor.**

            Procedural deviations are a common contributing factor to
            error. However, in order to determine the best way to "fix"
            the procedural deviations, we need to know why the deviation
            occurred. Therefore, it is important, when you determine
            during the interview that a procedural deviation occurred,
            to find out why the technician deviated. Some common
            procedural deviations include:

-   Failure to use the maintenance manual/task card

-   Failure to use torque wrench or other calibrated equipment

-   Failure to carry out a functional or operational check at the end of
    a procedure.

    In each of these cases, it is important to find out why the
    technician decided to deviate from the accepted procedure. There are
    several possible reasons, including:

1.  The procedure does not really work, so all technicians have to
    deviate from the procedure to get the task done

2.  The technician, for this one time only, decided to deviate from the
    procedure for some reason (e.g., was running out of shift time and
    wanted to get the task done, so he took a short cut)

3.  This one technician often deviates from any procedure, even though
    none of the other technicians do

4.  The procedure is a good one, but it has become the normal practice
    at this maintenance organization for technicians to deviate from
    this procedure

5.  The procedure is a good one, but it has become the normal practice
    at this maintenance organization for technicians to deviate from
    most procedures, and this is just one example of it

6.  The procedure is a local "shop practice," and it is not written
    down, so the technician deviated from the procedure because he had
    not been trained on it and did not know of its existence.

    It is important to find out why the deviation occurred, so the
    Results Form can be filled out correctly and a proper "fix" can be
    proposed. For example:

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1.  If the reason for the deviation was 1. above, then you would check
    boxes "H.7. Work process/procedure not followed" and "H.6. Work
    process/procedure" on the Results Form and write in the space "the
    technician did not follow the procedure because it does not work,
    because (and give the reason)."

2.  If the reason for the deviation was 2. above, then you would check
    box "H.7. Work process/procedure not followed" and give the reason
    that the technician gave you for not following the procedure.

3.  If the reason for the deviation was 3. above, then you would check
    box "H.7. Work process/procedure not followed" and give the reason
    that "This technician regularly deviates from acceptable procedures,
    and this is another example of that behavior."

4.  If the reason for the deviation was 4. above, then you would check
    box "H.7. Work process/procedure not followed" and box "H.9. Work
    group normal practice (norm)" and give the reason "The procedure was
    not followed, but this is the accepted practice (norm) in this work
    group."

5.  If the reason for the deviation was 5. above, then you would check
    box "H.7. Work process/procedure not followed" and box "H.9. Work
    group normal practice (norm)" and give the reason "The procedure was
    not followed, but not following procedures is a normal practice for
    most technicians in this organization, and this is just one example
    of that."

6.  If the reason for the deviation was 6. above, then you would check
    box "H.7. Work process/procedure not followed" and box "H.8. Work
    process/procedure not documented" and give the reason "The procedure
    was not followed, because the procedure is not documented, and the
    technician had never been trained on the procedure or told of its
    existence." \[You would probably also check box "E.4. Airline
    process knowledge" and give the reason "The technician was not
    provided training on this airline process."\]

    **Rule 4---Failure to act is only a contributing factor when there
    is a pre-existing duty to act.**

    This is an important rule of causation that comes from the legal
    field. We should not expect someone to do something unless there is
    a pre-existing duty to do that thing. For example:

-   We do not expect you to leave home for work 30 minutes earlier than
    usual just in case there is an unexpected traffic problem.

-   We do not expect a technician to come to work 30 minutes early just
    in case there is rush work to be performed.

-   We do not expect a technician to carry out a functional task twice
    just in case the first test was not enough.

    It is important to know in these situations exactly what
    pre-existing duties technicians/inspectors have. For example:

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-   Before closing an access panel, does the technician have a clearly
    stated duty to do a visual inspection of the area before closing the
    panel?

-   If the technician is not sure how to proceed on a task, does he have
    a clearly stated duty to get help from the lead/supervisor/engineer
    before proceeding?

-   If the technician deviates from a procedure, does he have a clearly
    stated duty to document the deviation?

    jjjjjjdfgertert

    **7.4 Overcoming Interviewer Biases**

    Attribution Theory was developed in the 1960s in the Social
    Psychology literature. One of the major findings from those doing
    research in Attribution Theory is **attribution bias**:

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-   When I make an error, I attribute my making the error to (external)
    contributing factors

-   When you make an error, I attribute your making the error to factors
    internal to the person (e.g., lazy, complacent, or careless).

    Thus, unfortunately, it is "human nature" for someone to blame
    another's misfortune on that person's internal factors, such as
    being lazy, complacent, or careless. An investigator must overcome
    their built-in attributions and, in an open-minded fashion, search
    for the "true" contributing factors.

    There are other types of biases of which the interviewer must be
    aware. Some of them are listed and defined below. The interviewer
    should like for these biases in themselves and try to overcome them.

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-   Experience/knowledge can have a positive or negative effect. It has
    a negative affect when the investigator thinks things like, "I don't
    even need to do the interview---I know what he did wrong," or, "All
    errors are a result of poor training."

-   Sometimes we believe that big events must have had a big cause. "Joe
    made a major error because the airplane was out of service for 2
    days." This is not necessarily true. Remember, one of the U. S.
    shuttle flights crashed and killed everyone on board because of a
    50-cent O-ring seal.

-   Sometimes an investigator only identifies those contributing factors
    that are within their ability to change. However, your job is to
    determine all of the contributing factors, even if some of them are
    hard or impossible to improve.

-   Factors that are close in time or space to the error will more
    likely be labeled as causal. While these factors may be causal, do
    not end your search for contributing factors with these items.
    Sometimes decisions about staffing or spare parts, which were made
    months before the event, are contributing factors to the error.

-   Factors that first draw the attention of the investigator will more
    likely be labeled as causal. While these may be true contributing
    factors, you must keep an open mind about other contributing factors
    so that you don't stop your search after the first one or two that
    caught your attention.

-   Sometimes an investigator sees an error-caused event that is similar
    to an historical error event and assumes that they both had the same
    contributing factors since the outcomes were similar. Do not make
    this leap of faith---determine the specific contributing factors to
    the event at hand.

-   Sometimes an investigator enhances or discounts a contributing
    factor explanation based on the presence of another contributing
    factor. For example, "Joe was tired, therefore the maintenance
    manual was confusing." Even if Joe is tired, you have to show what
    there was about the maintenance manual that confused Joe.

-   A very common bias that must be guarded against is blaming an error
    on a person's dispositions. For example, "Joe has a history of
    skipping functional tests, therefore, he must have skipped the
    functional test when he made this error." Do not guess at
    contributing factors. If you have a guess, check it out by the
    questions that you ask.

-   Sometimes an investigator describes first what should have been and
    then compares the actual events to determine what is causal. "Joe
    should have gotten a wing walker before moving the aircraft. He did
    not, so not getting the wing walker was a contributing factor."
    Remember, the failure to act is only a contributing factor when
    there is a pre-existing duty to act.

    Thus, as you can see, an interviewer's task is not an easy one. Not
    only should the interviewer follow the steps listed above in section
    7.1 in order to carry out the interview, the interviewer must be
    able to recognize his/her interviewing biases and overcome them in
    order to come up with the true contributing factors to the error
    that lead to the event.