Decision making specifics and usual deck officers’ mistakes during collision avoidance

by Aleksandr D. Pipchenko
Decision making specifics
and usual deck officers’
mistakes during collision
avoidance
NU OMA annual conference, 2018
LEARNMARINE.COM

15/11/2018 LEARNMARINE.COM
Incident statistics of European waters
2

Incident statistics of European waters
Distribution of very serious casualties
• A very serious marine casualty means a marine casualty involving the total loss of the ship or
a death or severe damage to the environment.
15/11/2018 LEARNMARINE.COM 3

Human error… again?

Incident statistics

Oil tanker Sanchi partially explodes in East China
Sea
06-01-2018

Sea
06-01-2018

MSC Alexandra & Dream II 03-Aug-16
• The VLCC Dream had
deadweight of 319,999 DWT and
gross tonnage of 164,241 GRT.
The ship was en route from
Beilun, China to Port of Khark,
Iran under ballast. The vessel
was built in 2008 by Daewoo
Shipbuilding and Marine
Engineering in South Korea.
• The container ship MSC
Alexandra 365.80 m/52.00 m
/12.00 m.
• Deadweight of 165,908 DWT,
gross tonnage of 153,115 GRT
and capacity to carry 14,000
TEU. The container carrier was
built in 2010 by Daewoo
Shipbuilding and Marine
Engineering in South Korea.

MSC Alexandra & Dream II

USS Fitzgerald & USS John S McCain
collision17-06-2017 & 21-08-2017

LPG Tanker ‘BW Maple’ collided with
chemical tanker ‘Dawn Kanchipuram’
28-01-2017

Josephine Maersk & Spring Glory
05-Jun-12

Vessel’s safety and COLREGs…
COLREGs IS EASY –
JUST ALTER COURSE
IN ADVANCEREALLY???

WHAT ARE WE?
STAND-ON OR GIVING THE WAY?

This happens when we do not take into account several
factors:
 As per IMO Performance Standards for RADAR
Equipment, ARPA CPA error may be as big as 0.3 nm.
 When we check the CPA on the AIS, it might be
unstable and show different values, depending on the
other vessel's sensor errors and motion.
 Also, we have to take into account the own vessel
dimensions.
 Even if the distance between vessels is big we shall
always check the TCPA, to understand how fast the
situation is developing.
Risk underestimation
LEARNMARINE.COM15/11/2018 19
Learnmarine

When own vessel maneuverability is not
taken into account, turns are often being
performed not as early as expected.
Especially this happens when the vessel
reduces the speed first.
Speed reduction consequently reduces
turning ability and one has to put rudder to
larger angles in order to perform turns with
the same rate as on faster speed. This is very
often omitted.
Maneuver is too late or not large enough
Learnmarine

Maneuver is too late or not large enough
Learnmarine

Autopilot initially set for the ocean passage, might not react
as fast as expected. Bad practice is to set the new course
on autopilot and leave it without supervision. While we
think that vessel is already turning it could not change the
heading at all.
Turn angle and realistic rate of turn shall be taken into
account. If you set 20°/min ROT in AP, 40° may take about
3 minutes. Therefore to reach desired CPA one has to start
turning at least three minutes in advance.
On the other hand, manual steering provides a faster ship
response, but may negatively affect the situational
awareness. Once started to steer the vessel manually all
watchkeeper's attention is stuck on the helm and the gyro
repeater. Therefore before using the helm one shall arrange
the helmsman in advance if not available on the bridge.
Relying on autopilot, when quick actions
are necessary
Learnmarine

When we have several targets at the scene
we have to find out, which targets are
limiting our maneuver and which are the
most dangerous. In a case shown on the
figure below, very often officers start to
estimate maneuver for the crossing target
B. The trick is if target A will not maneuver,
CPA with it will be too small. This happens
because the relative speed of approach for
target A is much bigger, which calls for a
bigger TCPA and consequently bigger course
alteration.
Doing maneuver for the wrong target
Learnmarine

For some reason, a lot of watchkeepers
totally disregard the speed maneuver
option. However, COLREGs Rule 8 does
recommend to use course alteration, if
"there is sufficient sea-room available". But
the same rule states:
“…If necessary to avoid collision or allow
more time to assess the situation, a vessel
may slacken her speed or take all way off by
stopping or reversing her means of
propulsion.”
Ignoring the speed maneuver
Learnmarine

On the picture below, vessel B on the port
side is initially may be passing clear and
doesn't need to give a way. But the own
vessel maneuver to starboard (to give a way
for vessel A) might bring it into close-
quarters situation when it can't provide the
safe distance with own maneuver. This
happens because its relative motion line
turns clock-wise if we turn to starboard.
That's why assessment of limiting targets
shall never be neglected.
Not checking how maneuver for one
vessel will affect another
Learnmarine

On the picture below a watchkeeper might prefer
to reduce speed to give a way to vessel B (which is
about 10° behind the beam). However this doesn't
improve the situation with the vessel A, which is
restricted in maneuverability, it only increases
TCPA, but risk of collision remains. Important point
is to find the moment when we can start turning to
starboard without affecting the CPA with vessel B.
The trick is that relative motion line (RML) behind
our beam with our staboard turn will turn anti-
clockwise, but once the target B gets ahead of our
beam RML's behavior changes and it will start
turning clock-wise with the Own Vessel turning to
starboard.
Doing 2nd maneuver too early, while the
first target is not clear
Learnmarine

To be able to find the best solution the navigator has to understand:
(a) How COLREGs shall be applied in different situations; and
(b) Relative motion laws.
Summary and conclusions
Learnmarine

WHAT ABOUT REMOTELY OPERATED OR AUTONOMOUS VESSELS?
Learnmarine

RISK BASED TARGETS
PRIORITIZATION
Learnmarine
Severity – is directly connected to the
approach velocity, as
KE = 0.5mV2
Likelihood – depends on MDTCP
(vessel maneuverability), CPA and
TCPA
MDTCP – minimum distance to
collision point Collision Risk Awareness
Close quarters: emergency
Close quarters: danger
Risk of collision: caution

FUZZY LOGIC AS A PART OF RISK ASSESSMENT
Learnmarine
MDTCP, nm CPA, nm TCPA, min
-- emergency; -- danger; - caution

Learn more about as at Learnmarine.com
Thank you for your attention!
Learnmarine

Decision making specifics and usual deck officers’ mistakes during collision avoidance

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Decision making specifics and usual deck officers’ mistakes during collision avoidance

Similar to Decision making specifics and usual deck officers’ mistakes during collision avoidance (20)

Recently uploaded

Recently uploaded (20)

Decision making specifics and usual deck officers’ mistakes during collision avoidance