Procedure
following
Perceptual
groupings in
air traffic
control
Subjects performing
visual target
tracking tasks
have been shown
to utilize perceptual
organization.
This organization
has been shown
to have both
Gestalt features
and goal-oriented
features. Previous
studies have
attempted to
use memory recall
techniques to
examine potential
cognitive groupings
in air traffic
control tasks,
with negative
results.
Analysis of eye
movements has
shown similar
patterns of
organization
to the underlying
visual tasks.
Experiments
were performed
to evaluate
whether recall
or eye-tracking
techniques can
be used to extract
perceptual groupings.
Subjects’
memory of scenario
information
is generally
poor, except
where significant
manipulation
of targets occurred.
For this reason
it is suggested
that recall
techniques may
not produce
accurate clustering
information.
Fixation data,
however, produced
clustering consistent
with Gestalt
factors. Goal-oriented
factors did
not seem to
affect grouping.
Paired
approaches
By decreasing
the spacing
required for
aircraft flying
instrument approaches
to closely spaced
parallel runways,
some of the
capacity lost
at these airports
under instrument
conditions may
be regained.
One method to
accomplish this
is called “paired
approaches”.
The paired approach
concept utilizes
“safe
zones”,
which are relative
positions in
which the two
aircraft paired
on approach
to the parallel
runways cannot
pose a near
midair collision
danger and in
which the wake
vortex from
the leading
aircraft will
pass behind
the trail aircraft.
A previous analytical
evaluation of
the safe zone
has determined
that there are
few significant
physical constraints
to implementing
paired approach
procedures.
A number of
issues remain
with respect
to human performance,
however. In
addition to
normal instrument
approach tasks,
a paired approach
procedure will
likely involve
a tracking task,
as the pilot
attempts to
remain within
the safe zone,
and a monitoring
task, which
would involve
monitoring the
relevant flight
deck display.
The former task
will depend
upon such factors
as the length
of the safe
zone, and the
rate of change
of the safe
zone. The latter
task will depend
not only upon
the types and
number of symbology
elements, but
also upon whether
the information
provides sufficient
cues for the
pilot to make
correct judgments
and decisions,
which will in
turn affect
action.
One additional
issue is the
source of the
information.
Real-time information
broadcast from
the aircraft
may be available,
which would
permit calculations
of the safe
zone based upon
current aircraft
and environmental
states. However,
there is also
information
available in
the form of
the restrictions
required by
the procedure.
These restrictions
indicate likely
speeds (and
perhaps positions)
for the aircraft.
This information
can be used
to provide predictive
information
about where
the safe zone
is likely to
be in the future,
or to provide
“worst-case”
safe zone calculations.
The real-time
information
is instantaneously
accurate, but
relatively dynamic,
and may not
provide sufficient
lead-time for
pilots to react
to changes in
the safe zone
due to speed
reductions,
missed approaches,
etc. The procedural
information,
on the other
hand, provides
a prediction
of the likely
position of
the safe zone,
is less dynamic,
but may not
be accurate
if the aircraft
are not following
procedural restrictions.
These two sources
should be combined
to provide the
best possible
information
for the flight
crews.
A recently completed
experiment utilized
a part-task
simulator and
line pilots
executing instrument
approaches to
closely spaced
parallel runways,
including scenarios
in which the
lead aircraft
blunders towards
the trail aircraft,
and in which
missed approaches
are accomplished.
The results
should help
determine if
pilots are able
to understand
the various
situations that
may occur during
the approach,
and whether
this understanding
will reinforce
compliance to
desired pilot
behavior. Additionally,
it will provide
some information
concerning the
utility of the
real-time and
procedural information,
and how to incorporate
that information
into a display.
Procedure
following
In my dissertation
research I investigate
information
displays to
support operators
when executing
procedures in
order to aid
performance
and increase
situational
awareness and
safety. Although
the experimental
efforts are
focused on aviation
procedures,
the results
have implications
for other safety
critical socio-technical
systems (such
as healthcare,
manufacturing,
nuclear power,
and spacecraft
operations).
The intent of
such displays
is to assist
operators in
not only following
operational
procedures,
but also in
comprehending
the context
of the procedures,
enabling them
to understand
why, when, and
how to deviate
from the procedures
if necessary.
The importance
of this problem
is reflected
in the observation
that the control
of most systems
in safety critical
environments
is highly proceduralized.
While the extent
to which procedures
impact the work
domain has been
recognized,
there has been
little human
factors work
on procedure
design and utilization
until recently.
Operators are
expected to
follow procedure
and are faulted
if they deviate
from procedures,
without considering
whether the
underlying procedure
contributed
to the operator’s
error, or even
whether the
procedure should
have been followed
at all.
Procedures themselves
are typically
developed informally,
pieced together
from diverse
requirements
and constraints
on the system.
The result is
that the design
philosophy behind
procedures is
not only sometimes
highly variable
from instance
to instance,
but is also
almost never
presented to
the operator.
Operators are
expected to
ardently adhere
to procedure
and still be
able to make
intelligent
decisions when
procedures fail,
but are given
little support
to accomplish
that goal.
Procedures are
frequently under-defined
and limited
in scope. Operators
must translate
the requirements
of the procedure
into action
and can encounter
situations that
were not considered
by those designing
the procedure.
Information
about the assumptions
made when the
procedure was
designed is
typically lacking
– there
is often no
training on
when procedures
do not apply
(and what to
do in those
situations),
and almost no
display support
is provided
to the operator
for following
or interpreting
procedures.
Even less training
and display
support is provided
on how to operate
once the procedure
has failed.
One example
of this is the
Three Mile Island
nuclear facility
incident in
1979. A President’s
commission conclusion
was that the
accident was
due to human
error caused
by deficiencies
in training
for operating
the plant under
accident conditions,
confusing and
misleading operating
procedures,
poor control
room displays
for operating
the plant during
emergency situations,
and a lack of
training on
previous accidents
.
Pilots of Alaska
Airlines Flight
261 were unaware
that normal
troubleshooting
procedures for
flight control
malfunctions
were inappropriate
with stripped
threads on a
horizontal stabilizer
jackscrew nut,
which contributed
to this fatal
accident . The
NTSB indicated
that insufficient
guidance concerning
the recognition
of when an approach
was unstabilized
and a lack of
indication that
part of the
pre-landing
procedure was
not followed
contributed
to a fatal accident
in Little Rock,
AR . Numerous
other examples
exist in the
NTSB database
The research described
in this document
is intended
to examine how
such support
in understanding
and following
procedure might
be provided
to an operator
and in what
ways the information
can aid the
operator.
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Last updated:
March 4, 2004