Human Factors Survey of Aviation Maintenance Technical Manuals

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Human Factors Survey of Aviation Maintenance
Technical Manuals
Alex Chaparro PhD, Leonidas Deligiannidis PhD,
Chris Hamblin, Bonnie Rogers National Institute
for Aviation Research
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Increased Attention Given to Maintenance by
Regulatory Agencies

• Precipitated by
• Seminal Incidents Aircraft accidents
• Increases in aircraft traffic
• Percentage of accidents attributable to
  maintenance error appears to have change little
  over that last 50 years.

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Maintenance Error and Aircraft Safety

• Aloha flight 243 (1988) Structural failure of the
  upper cabin
• Two experienced inspectors failed to detect
  cracks in the aircraft skin.
• BAC1-11 (1990) Left windscreen blew out
• 84 of 90 securing bolts were smaller than the
  specified diameter

http//www.volpe.dot.gov/infosrc/journal/30th/imag
es/safe_aloha.jpg
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Fatal Accidents of Large Commercial Jets
(1959-2001)
www.flightsafety.org/ priorities.html
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Predicted Increases in the number of commercial
flights and aircraft accidentspre 9-11.
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Maintenance Error

• Analysis of maintenance errors indicates that the
  majority of incidents involve omitted or
  incorrect execution of tasks, incorrect
  installations, and the use of incorrect parts
  (Boeing, 1995).
• Johnson and Watson (2001) identified information
  as being the highest ranked contributing cause,
  being implicated in approximately 38 of all
  maintenance errors.
• An analysis of NASA Aviation Safety Reporting
  System data regarding maintenance incidents found
  document procedures to be related to 60 of
  incident reports from 1986 to 1992 and 45 of
  incidents from 1996 to 1997.

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Review of User-reported problems with maintenance
documentation

• Publication Change Request (PCRs) represent
  errors that the current maintenance manual
  development and review process have failed to
  detect.
• Two companies provided copies of PCRs to the
  maintenance manual submitted by users.
• Reviewed a total of 300 PCRs
• Categorized requested changes into four groups
  technical, procedural, graphic, and language

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Types of errors for each category

• Technical
• Incorrect parts, values or tools are specified
• Procedural
• Poor sequencing, missing/unnecessary procedures,
  failure to specify how to check/test equipment
• Language
• Typos, grammar, clarity
• Graphics
• In correct dimensions, incorrect graphic, poor
  quality graphic

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Analysis of the PCRs

• 39 of PCRs report errors in procedures
• 31 of the PCRs report errors in technical
  information
• 24 of the PCRs report problems with language

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Examples of PCRs

• Aircraft Manufacturer 1
• Torque values were called out in percent rather
  than foot pounds
• Changed to foot pounds
• The figure indicated the Left and Right oxygen
  bottles connecting incorrectly into a tee fitting
• Replaced with an accurate illustration of the
  components
• Also included a drawing of the oxygen system
  layout

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Contd Examples of PCRs

• Aircraft Manufacturer 1
• After maintenance operation, electrical
  connection to the propeller synchronizer and
  automatic feathering solenoid had been switched
• Added note on possibility of misconnecting
  components
• Added check/test for source of system malfunction
• The check valve can be installed backwards
• Added check arrow on component in a graphic
• Added a note after step suggesting that the
  technician confirmed the direction in which the
  arrow should point

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Normans Action Cycle
Mechanics Goal(s)
Execution
Evaluation
Gulfs of Execution
Gulfs of Evaluation
Intention to act
Evaluation of interpretations
Sequence of action(s)
Interpreting the perception
Execution of the action sequence
Perceiving the state of the world
The World
(Norman, 1988)
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Normans Action Cycle
Mechanics Goal(s)
Execution
Evaluation
Gulfs of Execution
Gulfs of Evaluation
Intention to act
Evaluation of interpretations
KIH ? KIW
KIW ? KIH
LTM STM Chunking Graphics Affordances Mapping Con
straints
Sequence of action(s)
Interpreting the perception
Feedback Check/test Inspections
Execution of the action sequence
Perceiving the state of the world
The World
(Norman, 1988)
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Bridging the Gulfs

• Facilitating task execution by using
• Mapping in the form of color coding
• Physical constraints
• organizing tasks into smaller subtasks reducing
  working memory demands
• Identifying task critical information that the
  user needs
• Including the user in the document development
  process

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Bridging the Gulfs

• Facilitating task evaluation by using
• Mapping in the form of color coding
• Physical constraints
• Feedback in the form of check/tests
• Improving visibility to allow system monitoring
  by the maintenance personnel

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User-Centered Design

• Analysis of the PCRs suggests that many of the
  problems stem from a mismatch between mental
  model of the writer and the mechanic regarding
  how maintenance is performed and what is
  maintenance relevant information.
• Technical writers may not have experience
  performing aircraft maintenance
• User (mechanic) is rarely consulted in the
  development of the maintenance procedures
• Maintenance procedures are typically not validated

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Current practices

• Validation of the maintenance procedures is often
  limited because
• access to aircraft is limited
• Aircraft is not in the configuration that the
  customer will receive
• assumed cost of validation
• Lack of familiarity with evaluation techniques
• Time constraints
• Low priority given to maintenance issues by
  manufacturers

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Using Virtual Reality Technology to Validate
Maintenance Procedures

• Allows evaluation of maintenance procedures to be
  performed earlier in aircraft development
• Can use latest engineering drawings for an
  aircraft or its components
• Physical access to the aircraft is not required
• Maintenance procedures can be evaluate at any
  time
• Assembling a component incorrectly does not
  impact a safety
• Many aircraft manufacturers operate VR labs

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Limitations of Virtual Reality

• Limited or distorted cues/feedback
• Ability to simulate tactile cues is limited
• Ability to use both hands to interact with a
  simulate object is not supported

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Application of VR

• Problems that are being addressed at WSU
• Multi-view environments for observation and for
  training
• Interaction techniques for single or two-handed
  environments
• Navigation techniques

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Multi-View Environments

• Intended for the evaluation of maintenance
  procedures (observer views subject performing the
  maintenance task)
• Adds educational value

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Navigation issues within VR

• Need navigation because of
• limited tracker range
• physical room dimensions
• View larger components from a distance
• Need to move in 3 dimensions to view or access
  components positioned out of reach.

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Gestures For Navigation

• Gestures needed to move around and to interact
  with the virtual environment
• Navigation required two flavors
• FLY user can point at the direction of travel
• DRIVE similar to FLY but user does not move
  vertically

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Interaction Techniques

• Need to grab/select and manipulate components to
  assemble/de-assemble a larger part
• Need to be able to work with two hands
• May need to manipulate remote objects (fly back
  and remove unwanted components)

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Interaction Techniques (Cont.)
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Implementation

• JWSU a java based VR toolkit that supports
• multiple view
• different interaction techniques
• different navigation techniques
• easy to add on new interaction/navigation
  techniques
• utilizes the Xj3D VRML loader to load complex
  models (www.xj3d.org)

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Remaining technical Issues

• Need for better haptic simulation
• Need for better bimanual interaction with VR
  models
• Need to evaluate the effectiveness of VR for
  validating aircraft maintenance procedures.

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Summary

• The development of aircraft maintenance
  documentation has proceeded without consideration
  of the needs of the user population.
• Further improvements in aircraft safety may be
  realized by the application of cognitive
  principles as part of a User Centered approach
  to aircraft maintenance.
• Virtual Reality holds promise as a means to
  validate maintenance procedures earlier in the
  development of an aircraft.