Human Factors Survey of

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14 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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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

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.


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/images/safe_aloha.jpg

Fatal Accidents of Large
Commercial Jets (1959
-
2001)

www.flightsafety.org/ priorities.html


Predicted Increases in the number of commercial
flights and aircraft accidents*

*
pre 9
-
11.

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.


Review of User
-
reported problems with
maintenance documentation

Publication Change Request (PCR’s) represent
errors that the current maintenance manual
development and review process have failed to
detect.

Two companies provided copies of PCR’s to the
maintenance manual submitted by users.

Reviewed a total of 300 PCR’s

Categorized requested changes into four
groups: technical, procedural, graphic, and
language


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


Analysis of the PCR’s

39% of PCR’s report errors in procedures

31% of the PCR’s report errors in technical
information

24% of the PCR’s report problems with
language



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

Cont’d: 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

Execution

Evaluation

Mechanic’s

Goal(s)


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’s Action Cycle

(Norman, 1988)

Gulfs

of

Execution

Gulfs

of

Evaluation

Execution

Evaluation

Mechanic’s

Goal(s)


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’s Action Cycle

(Norman, 1988)

Gulfs

of

Execution

Gulfs

of

Evaluation

KIH
≠ KIW

LTM

STM

Chunking

Graphics


Affordances

Mapping

Constraints

KIW
≠ KIH

Feedback


Check/test


Inspections

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

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


User
-
Centered Design

Analysis of the PCR’s 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

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

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


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



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

Multi
-
View Environments

Intended for the
evaluation of
maintenance procedures
(observer views subject
performing the
maintenance task)

Adds educational value

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.

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

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)

Interaction Techniques (Cont.)

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)

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.

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.