Collision
of the liner
The
first “radar assisted collision”.
On
At
Inquiries would later determine officers
aboard Andrea Doria had used improper radar
procedures, and turned to the left at in the moments prior to the collision
rather than to the right - the proper Rule of the Road for a head on crossing
at at sea.
“The first radar assisted collision”:
She took the northern track against westbound traffic to save
time and fuel and with the captain's expressed belief that encountering head-on
shipping was safer than crossing. Interestingly, studies done some years later
by A.N. Cockcroft and published in the "Journal
of the Royal Institute of Navigation" presented data showing that, in
restricted visibility, 75 percent of 494 collisions involved meeting situations
and 20 percent crossing.
Even if Doria, (thought to be to port)
was fine on Stockholm's starboard bow, an early and significant course change
to starboard would have complied with the Rules mandating a port-to-port
passage in a meeting situation, and more critically, would have supplied early
and unequivocal information to Doria's radar
regarding Stockholm's intention and thus time to manoeuver
if any confusion remained.
Andrea Doria, upon entering markedly
reduced visibility, took all the necessary steps (whistle signal every 100
seconds, watertight doors secured, lookout, etc.) but her token speed reduction
from 23 to 21.8 knots was insufficient.
Having determined a tight CPA to starboard, she came left (by
only) 4 degrees. The Rules (and courts) mandate a port-to-port passage unless a
starboard passage can be achieved safely without the necessity of either vessel
changing course to open the CPA further. Even this change, if it had been done
earlier and boldly (60 degrees or so), would have made her intentions known to
Doria's
excessive speed for the conditions, Stockholm's insistence on going down a
"one-way street" in the wrong direction, Doria's
attempts to improve the margin of safety for a starboard passage instead of
going to starboard for a port-to-port passage as required by the Rules,
Stockholm's failure to suspect fog ahead - all of these would have proven moot
if the awareness of the developing close-quarters situation had triggered even
one of the vessels to "early and significant action."
It's ironic that navigational plots done as part of the
subsequent investigation demonstrated that if neither vessel had radar and had
thus not changed course, they would have effected a
close starboard-to-starboard passage. Radar guided them (and their decisions)
into the jaws of collision.
A Destroyer skipper I once had never ceased impressing upon his OODs the idea that it is not only important to know and
follow the Rules, but that any action taken be early so that, as he emphasized,
"the other vessel knows what you're doing. Make any course change large
enough so that (if at night) the light shift can be seen and one that his radar
will detect. Half of preventing a collision is you knowing what you're doing --
the other half is that he knows what you're doing." A great skipper.
-- Jim Austin
“Another subsequent radar assisted collision”:
Collision in the Channel
By Andrew Craig-Bennett
The UK Marine Accident Investigation Branch
(MAIB) report on the collision between the British yacht “Wahkuna” and the Liberian
flag, containership “P&O Nedlloyd
Vespucci” on the 28th May
2003.
This collision has lessons for almost
everyone. A large, well equipped, modern yacht, in the hands of a very
experienced owner and with a strong crew, was run down and sunk, in fog, in the
English Channel by a large, modern, well equipped containership with a good
professional crew, which was unaware of the accident and did not stop. Very
fortunately, no one was killed, and the colliding ship was successfully
identified, so the MAIB have been able to speak to everyone concerned in the
incident. This was a classic “radar assisted” collision. Both vessels saw each
other on radar in good time. The collision, which would not have happened had
radar not been in use on both vessels, was precipitated by mistakes in the use
of radar. The ship was keeping a good lookout, with the Master, the officer of
the watch and a lookout on the bridge, the yacht had all five crew members in
the cockpit and was motoring in a light air with the mainsail hoisted to
increase visibility.
The ship was bound from Antwerp to Singapore;
at the time of the accident she was making 25 knots, her full sea speed. The
yacht was bound from Dielette to the Needles, and was
making 7.5 knots under power when she saw the ship’s radar echo. The collision
occurred almost midway between Alderney and the Isle of Wight. The French radar
station responsible for this area of the Channel, CROSS Jobourg,
reported that 19 ships passed through their surveillance area during a period
of dense fog, from 10.00 until 14.00, on the day of the accident. Only one of
these ships reduced speed. The ship was unaware of the collision. Her officers
assumed that no impact had taken place, because the yacht’s echo on the ship’s
ARPA appeared to pass clear of the ship by two cables, and the lookout posted
on the bridge wing saw nothing.
The yacht’s crew abandoned into their life
raft, but the EPIRB did not work, due to a corroded battery. By good fortune,
they were picked up, after more than five hours in the raft, by the fast ferry
“Condor Express”, which saw a flare. Although the crew of “Wahkuna”
did not see the ship’s name, the MAIB had no difficulty in identifying the
ship, with the help of the records held by CROSS Jobourg,
and MAIB inspectors flew to Hong Kong to meet the ship on her arrival there.
The yacht
The yacht had a Raymarine
radar; besides the chart table display there was a cockpit display and this was
being watched. The (M) ARPA features of the radar were not in use and no manual
plotting was being done. When the containership’s echo was seen it was assumed
that she was on a collision course. The yacht was slowed and the engine taken
out of gear, so that the ship could pass ahead. Had the yacht held her course
and speed she would have passed eight cables ahead of the ship. The MAIB
comment: “The actions taken by the yacht were based on an inaccurate assessment
of the situation by radar and served to confuse the bridge team on P&O Nedlloyd Vespucci as well as
putting the two vessels on a collision course. Had the skipper been able to
make full use of his radar, a more accurate assessment of the situation would
have been possible, and it would have been apparent that a substantial
alteration of course to starboard, in accordance with Rule 19(d), would have been
more appropriate.” “When Wahkuna was virtually
stopped in the water, her skipper estimated that the radar contact would pass
1.5 miles ahead as a result of his action. This assessment, however, was based
only on a visual interpretation of the radar display, because none of the crew
knew how to use the radar’s automatic plotting facilities, and a manual plot
was not undertaken… “After making the assessment that the container ship would
pass ahead, it is evident that a radar lookout was not maintained. Had it been,
it would have been apparent that the container ship was closing rapidly, and
avoiding action could have been taken sooner”.
The ship
To any yachtsman, the most striking things
about the ship are that she was making 25 knots in a fog so dense that her own
bow was not visible, and that she did not see the yacht she hit. The MAIB
however see things a little differently. They point out that, if the old,
pre-Radar, definition of “safe speed” – a speed that allows the ship to stop
within the range of visibility – is used, the ship should not have been under
way at all, since, even at manoeuvring dead slow ahead she needs three cables
to stop. But they proceed to tiptoe rather gently round the whole question of
Rule 6 (safe speed) in relation to the containership, with a learned discussion
of the Rules, including citations from the leading textbook, Cockcroft and Lamejier, papers by
the Seafarers International Research Centre at Cardiff University and the MCA’s
own Marine Guidance Notes on Navigation in Fog, and an inconclusive discussion
as to whether the Master was under commercial pressure to maintain full speed.
This will be very surprising to yachtsmen; it is not at all surprising to
professional seamen.
The reality of today is that ships do proceed
at full speed in fog, relying on radar, and, in the case of containerships,
these speeds are now very high. It will be recalled that, of the 19 ships that
passed through the area during the fog, only one reduced speed. The MAIB
condemn the ship for having the radar set in use for collision avoidance ground
stabilised (referenced to the GPS) and not water track stabilised (referenced
to the log and compass). This is contrary to IMO recommendations, because, of
course, any tidal stream or current renders the information presented by the
ARPA display incorrect. This is an elementary, but common, mistake, so far as
radar observers are concerned, and it probably accounts for the ship’s
impression that the target representing the yacht passed clear of them by two
cables and resumed her course, when in fact she had collided with the ship and
was sinking. The MAIB also condemn the ship for excessive reliance on the
accuracy of her (erroneous) ARPA plot and for accepting too close a closest
point of approach (CPA)
When the yacht slowed down, it was evident to
the ship (but not to the yacht, which seems not to have continued to observe
the radar) that a risk of collision now existed, but the Master was unsure what
action to take; he put the ship in hand steering, posted the OOW to the wheel
and posted the lookout to the bridge wing. He did not slow down or alter
course, because the yacht’s movements had suddenly become unpredictable to him.
The yacht skipper’s decision to slow down to avoid crossing ahead of a large,
fast moving target is the decision that most yachtsmen would make. The
containership master’s decision to go to hand steering, but to maintain his
course and speed, when he became concerned about the yacht’s intentions, is the
decision that most professional seamen would take. These two decisions, both
quite intuitive, caused the collision, because the yacht’s position vis-à-vis
the ship was not what the skipper assumed it to be.
Recommendations
Not surprisingly, the MAIB have written to the
makers of the failed EPIRB! They also recommend that the RYA should emphasise
the importance of Rule 19 (conduct of vessels in restricted visibility) and
that manufacturers of yacht radars should include a voucher for free training
in radar plotting with each yacht radar set sold. However, this begs the
question of use of radar for collision avoidance aboard yachts.
As this incident demonstrates, unless either
manual or automatic plotting is carried out, using accurate inputs, the use of
radar in fog can cause a collision that would otherwise be avoided. The yacht
in this case was very well equipped, with a cockpit radar screen as well as one
at the chart table, and a strong crew of 5. To use radar for collision
avoidance requires training, but it also requires that someone who has had that
training should keep a continual watch on the radar picture. This is by no
means easy to do, and a cockpit repeater is not the place to do it.
With the benefit of 20/20 hindsight, the first
lesson that this case teaches is that if a yacht is crossing shipping lanes in
fog, and has radar, if at all possible a crew member, trained in the use of
radar, should follow big ship practice and maintain a continual watch on the
radar set, preferably in the cabin and away from distraction. Rather than apply
the old, pre-radar, yacht rule of “When in doubt, in fog, stop the engine and
listen” yachtsmen should apply Rule 19 – there is no stand on vessel in fog,
think of the trace that you are painting on the other ship’s radar, and avoid turning
to port for an echo ahead of the beam.