28
Sensemaking in Safety Critical and Complex Situations
mode and checking the ship’s position given by the GPS ( Global Positioning System)
against the ship’s ground-based radar system ( L oran-C). The agreement between the
two systems was within the required tolerances and the ship departed. T hirty-four
hours after departure, the ship ran aground, 17 miles off course.
• June 10, 1995, RM departs St. Georges, Bermuda, en route to Boston.
• Ship’s navigator sets autopilot in NAV mode. Checks GPS against ground/ radiobased positioning systems ( L oran-C). Ground-based system reveals the position
about 1 mile southeast of GPS position.
• 30 minutes after departure, the cable from the GPS receiver to the antenna had
come loose and the GPS had defaulted to dead reckoning mode ( navigating by
estimating the distance and direction travelled rather than by using landmarks or
astronomical observations in the absence of the GPS).
• 34 hours after departure, ship runs aground, 17 miles off course.
The official report into the grounding contains an extensive analysis of the incident itself: the actions of the captain and the officers on the bridge in the hours prior
to the grounding and the equipment and systems in use at the time. At first sight, it
appears remarkable that the officers were unaware that the navigation system had
defaulted to dead reckoning mode and was not connected to the GPS. They also
failed to understand the significance of a red light sighted by a lookout and a call
from a Portuguese fishing vessel to warn the ship that it was in shallow water. At
some points in the report, there is a focus on what the officers should have done,
for example, ‘ Had the officers compared position information from the GPS and the
Loran-C they should not have missed the discrepant c o-ordinates’ and, on approaching land, ‘ The second officer’s response to these sightings should have been deliberate and straightforward. He should have been concerned as soon as the buoy was not
sighted and when the lookouts sighted the red light…’. Statements such as these are
easy to make with the benefit of hindsight because accident investigators know what
happened next. Hindsight bias shifts the focus of an investigation onto what the
those involved should have done. Focussing on those who were closest in time leads
to hindsight bias – safety initiatives centred on redrafting of instructions, rules and
training procedures.
However, the report ( in accordance with the scissors analogy in Figure 2.1) also
identified a number of PSFs that help us to understand why everything seemed to be
in order:
• In those days, satellite reception was poor and the GPS often went ‘ offline’ for
short periods. This was not necessarily a cause for concern
• There was no clear indication that the system had defaulted to dead reckoning
mode
• The GPS display indicated that the ship was on course
• When the GPS did go offline, the indications that it had done so were weak ( a
short ‘ beep’ may have been heard and the letters ‘ DR’ appeared at the bottom of
a small screen)
• Even if they had heard the ‘ beep’ it was nothing to worry about
Sensemaking in Safety Critical and Complex Situations
mode and checking the ship’s position given by the GPS ( Global Positioning System)
against the ship’s ground-based radar system ( L oran-C). The agreement between the
two systems was within the required tolerances and the ship departed. T hirty-four
hours after departure, the ship ran aground, 17 miles off course.
• June 10, 1995, RM departs St. Georges, Bermuda, en route to Boston.
• Ship’s navigator sets autopilot in NAV mode. Checks GPS against ground/ radiobased positioning systems ( L oran-C). Ground-based system reveals the position
about 1 mile southeast of GPS position.
• 30 minutes after departure, the cable from the GPS receiver to the antenna had
come loose and the GPS had defaulted to dead reckoning mode ( navigating by
estimating the distance and direction travelled rather than by using landmarks or
astronomical observations in the absence of the GPS).
• 34 hours after departure, ship runs aground, 17 miles off course.
The official report into the grounding contains an extensive analysis of the incident itself: the actions of the captain and the officers on the bridge in the hours prior
to the grounding and the equipment and systems in use at the time. At first sight, it
appears remarkable that the officers were unaware that the navigation system had
defaulted to dead reckoning mode and was not connected to the GPS. They also
failed to understand the significance of a red light sighted by a lookout and a call
from a Portuguese fishing vessel to warn the ship that it was in shallow water. At
some points in the report, there is a focus on what the officers should have done,
for example, ‘ Had the officers compared position information from the GPS and the
Loran-C they should not have missed the discrepant c o-ordinates’ and, on approaching land, ‘ The second officer’s response to these sightings should have been deliberate and straightforward. He should have been concerned as soon as the buoy was not
sighted and when the lookouts sighted the red light…’. Statements such as these are
easy to make with the benefit of hindsight because accident investigators know what
happened next. Hindsight bias shifts the focus of an investigation onto what the
those involved should have done. Focussing on those who were closest in time leads
to hindsight bias – safety initiatives centred on redrafting of instructions, rules and
training procedures.
However, the report ( in accordance with the scissors analogy in Figure 2.1) also
identified a number of PSFs that help us to understand why everything seemed to be
in order:
• In those days, satellite reception was poor and the GPS often went ‘ offline’ for
short periods. This was not necessarily a cause for concern
• There was no clear indication that the system had defaulted to dead reckoning
mode
• The GPS display indicated that the ship was on course
• When the GPS did go offline, the indications that it had done so were weak ( a
short ‘ beep’ may have been heard and the letters ‘ DR’ appeared at the bottom of
a small screen)
• Even if they had heard the ‘ beep’ it was nothing to worry about