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2014/04/25

Sewol. Chronicle of a tragedy.

Sometimes the sea is not as kind as we would like to believe. Sometimes the sea is brutal. This time, however, was not only the sea, but the criminal incompetence of those who ruled the ship a handful of minutes before the tragedy was taking place. Who didn't wish to be present to avoid, expertly, that the incident occurred, who for only greed has increased dramatically the carrying capacity of the ship, helping to raise the center of gravity and, in fact, jeopardize all passengers. Sooner or later it would happen! 
Hurts to find out what happened at the time that over 300 young student were aboard to reach an island vacation.

Cries my heart to read this terrible news, I'm a father, I understand the pains of those parents, and I am horrified at the thought. There is still much to be done so that do not happen again, not by the hand of man, not to earn a few dollars more. What ever are now those dollars faced with the death of so many young lives?

What caused Sewol sinking? 

Human errors, which accounted for 85% responsible in all maritime accidents; will not reduce in accidents waiting to happen; but number of accidents could decrease in a climate of more improved safety culture in maritime sector. All of as are accounted for this challenging task. The 6,325-ton Sewol was carrying 476 people, including 325 students from a high school in Ansan, just south of Seoul, when it sent out a distress signal at 8:58 a.m. in waters 20 kilometers off the island of Byeongpoong.

MS Sewol, previously Ferry Naminoue or Naminoue-Maru, was built by the Japanese company Hayashikane in 1994. She had 146 m (479 ft) in length and 22 m (72 ft) in width, it could carry 921 passengers, 956 including the crew.  It was operated by Cheonghaejin Marine Company, Incheon.

It had been reported to have space for 180 or 220 cars and could carry 152 20-foot shipping containers. The maximum speed of the ship was 22 knots (41 km/h; 25 mph
Sewol operated in Japan for 18 years (from 1994). The ship was brought in from Japan on October 2012. 

Since then extra passenger cabins were added on the third, fourth and fifth decks, increasing the passenger capacity by 181, and increasing the weight of the ship by 239 tons. The construction was legal and passed regulatory tests.
After regulatory safety checks by the government of South Korea, the ship began its operation in South Korea on 15 March 2013. 
The ship then made two-to-three round-trips every week from Incheon to Jeju.

It was reported that Sewol again passed a vessel safety inspection by the South Korean Cost Guard on 19 February 2014.
This inspection was called an “Intermediate Survey” which according to International Association of Classification Societies (IACS), “include examinations and checks as specified in the Rules to determine whether the ship remains in a general condition which satisfies the Rule requirements.”


How the accident happened?

On 16 April 2014; about 30 kilometres (19 mi) off the southwest coast, the ferry began to list badly as it headed for Jeju. There were reports of the ferry having veered off course but the co-ordinates of the accident provided by port authorities indicated it was not far out of the regular shipping lane. 

The ship, reportedly altered the course with a very big rudder angle (a sharp turn) and during that turn (to starboard side?), ship very heavily listed on her port side. Right at that moment, a very Rescued passengers reported hearing a loud noise and the ferry coming to a shuddering halt – indicating it may have run aground although the water was reportedly 37 metres (121 ft) deep at the place where the ship capsized. Rescued passengers also reported that they were told "don't move" by an announcement over the ship's intercom system, whilst the ship was sinking.

Inside the ferry, chaos unfolded, survivors said, as the walls and floor seemed to exchange positions. Bottles and dishes fell. The ship’s twisting stairways became almost impossible to negotiate. Passengers were tossed to one side. Trays and soup bowls overturned, said Song Ji-cheol, a college student who worked part-time in the cafeteria.
The ferry was reported to be sinking at 8:58 am Korean Time.

At 9:30 am, the ferry was reported to have tilted 20 degrees to the Port side..
By around 11:18 am, the bow of the ship was submerged, with about 2 metres of height and 20 to 30 metres in length showing. 
At 8 am KST on April 18, only 1 metre of the bow was above water
As of 1:03 pm, the ship was completely submerged.

During the capsizing, it was first believed that passengers trapped in the vessel were able to send text messages to friends and family as the vessel sank. However, subsequent investigations by the Cyber Terror Response Center reported that survivors had not used their phones from noon on the 16th to 10 am on the 17th and determined that all reported text messages were fake.

Ocean temperatures in the area where the ship capsized were around 12 °C (54 °F), and the length of time before signs of hypothermia are exhibited at that temperature is approximately 90 minutes.
As of 25 April 2014;  188 of the ship’s 476 passengers and crew members confirmed dead and about 118 missing, compared to 179 survivors.


Captain accused of leaving the bridge

Initial investigations showed that at the time of accident, the third officer- an inexperienced officer who started to work onboard just 6 months ago-  was on duty and the Ship’s captain Lee Joon-seok- a 68-years old professional-  arrived into the bridge right after the accident.  According the report of third officer, the Captain was calm and asked the angle of ship’s list. 

According to my experience, what Captain’s behaviour was the proper practice and there is nothing to blame. Captain can not be expected to be on the bridge at all times and duty officer is eligible for navigation at open seas,  as far as the ship is not navigation in high risk areas or pilotage waters. According to reports, neither was the case. So what happened? We can only estimate. 

Can a sharp turn cause sinking?

Answer is quite simple: Yes, it can. It can and for various reasons this can take place. But, there should be other assisting factors for this result. First, if the ship has got a very narrow GM (Metesantric Height)  distance, or negative GM that can occur. Such ships are called as "tender ship" (Contrary to a "stiff ship")  and they ususally have difficulty to correct themselves if listed to one side. The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stability against overturning. 

Metacentric height also has implication on the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers. Hence, a sufficiently high but not excessively high metacentric height is considered ideal for passenger ships. An excessively low or negative GM increases the risk of a ship capsizing in rough weather, for example HMS Captain or the Vasa. 

It also puts the vessel at risk of potential for large angles of heel if the cargo or ballast shifts, such as with the Cougar Ace. A ship with low GM is less safe if damaged and partially flooded because the lower metacentric height leaves less safety margin. For this reason, maritime regulatory agencies such as the International Maritime Organization specify minimum safety margins for seagoing vessels. 

A larger metacentric height on the other hand can cause a vessel to be too "stiff"; excessive stability is uncomfortable for passengers and crew. As greater the metacentrik height goes, righting lever increases accordingly.  It corrects the ship to come upright again. If a ship floods, the loss of stability is caused by the increase in KB, the centre of buoyancy, and the loss of waterplane area - thus a loss of the waterplane moment of inertia - which decreases the metacentric height.  

This additional mass will also reduce freeboard (distance from water to the deck) and the ship's angle of down flooding (minimum angle of heel at which water will be able to flow into the hull). The range of positive stability will be reduced to the angle of down flooding resulting in a reduced righting lever. 

When the vessel is inclined, the fluid in the flooded volume will move to the lower side, shifting its centre of gravity toward the list, further extending the heeling force. This is known as the free surface effect.

The island group on the Port side of the ship let us think that ship altered the course to Starboard, not to Port. The island group on the Port side of the ship let us think that ship altered the course to Starboard, not to Port.


Which could be the case in Sewol accident? 

If Sewol was not in a collision-with a submerged rock or any other unknown object- then, most probably, the ship had a very narrow metacenter height and large heel periods. 
Using the helm with a great angle- due to the inexperience of the officer on watch or a technical failure, as mentioned above-  could result in a big outwards heel. 

When turning, especially in a sharp turn for which a greater angle of rudder has been used,  the initial heel when the wheel is put over is inwards, because the rudder force is acting at a point below the centre of gravity of the ship.  
As the ship begins to turn, the centripetal force on the hull (which is greater than the rudder force), acting through water pressure at a point below the centre of gravity, overcomes the tendency to heel inwards and causes her to heel outwards.  

This outward heel is very noticeable when turning at good speed.  If the wheel is eased quickly the angle of outward heel will increase, because the counteractive rudder force is removed while the centripetal force remains, until the rate of turning decreases.  Should an alarming heel develop, speed should be reduced instantly.

Then, returning to Sewol case; this is a question which remains to be answered:  why the ship's rudder was put in a very large angle-most probably to hard to starboard (less likely to port) which resulted in the sharp turn and heel? Answers may vary: there might be another ship, a sailing or fishing boat, or the island was too close on the port bow due to a drift (remembering the strong currents in the area, drifting should be expected; and inexperience of the officer might play a role here, again) caused a panic to officer,  forcing her to put the helm hard to either side. The inexperience of watch officer could play a role in here. Because, if she was aware of the metacenter height of the ship, she would not do so. 

On the other hand, the officer on duty, appears to be a female officer, said to reporters that, she did not make a sharp turn, but "the steering turned much more than usual."
What is the meaning of this? To my interpretation; She means that she did not give a rudder command with a big angle; but, however, due to the Helmsman's error or a technical failure, the rudder went all the way to the side. Well, hard to port or hard to starboard. An exceptional order which could be used very easily in harbor operations but never -except emergency- on a ship with little metacenter margin at full speed ahead! 

Of course, a human error of helmsman, or a mechanical failure of the rudder, should not be omitted. What third officer said could be just the truth. But the result remains unchanged: A rudder command was given with a great angle while the ship was proceeding in her full speed. As a counter action, the ship’s speed should be dropped immediately and in this case, according to wittness reports, this was also done. 

Whatever happened; had happened at the initial heel, the very first one. Witnesses say that there was a very big noise. If not crashing to a submerged rock, or obstacle, what could be the cause of this, if not the clushing of cargo, either with each other or with ship's side plates? And, in this case, as the cargo of Sewol were nothing else than cars and vehicles in the garage and some containers on the fore deck, shifting-sliding-overturning of the vehicles at ship’s garage during the heavy listing  could be the case. This could push the center of gravity towards the listed side and crashing  of vehicles could damage the ship’s shell plates which could lead sea water inside- further worsening the scenario. The result is an immediate and inevitable capsize. 

Sewol Captain: Did he know the ship was tender?

And how this emergency situation was handled by the ship’s crew? Reports seem that crew- and obviously the Captain- underestimated the situation at the very first moment.  In a good risk evaluation should result by alarming all crew and passengers to gather at muster stations. Ship’s emergency alarm should be announced. This was not the case, however. The passengers were asked to stay in their cabins, assuming this wold be safer. Wrong assumption!

Another important point. Many people trying to find an answer to the question: why Sewol captain was so late to give the order for evacuation? Captain's answer to this question is clear: "I did not want to risk the passengers in cold water and strong currents until the assistance arrives" he says. But; he could have ordered passengers to vacate the inner cabins and come upper decks, where they would have had a greater chance of survival -- without telling them to abandon ship. So why he did not do that?

To my estimation: the Captain knew the small metacentre margin that  the ship had. If all passengers rushed up to upper deck, this would even worsen the situation by changing the center of gravity further up. That's why he did not call all passengers to the upper deck, hoping to balace the ship in the mean time. Big risk, at the cost of the life of passengers!

"You couldn't turn the wheel very sharply on that boat. You just couldn't. It was dangerous because the dynamic stability was not very good." This is the statement one of the ex-crewmembers of Sewol ferry, concurring with my early remarks about the accident that the ship had a stability problem with marginal metacenter height. 

Ex-workers  also said that "the vertical extension and renovations to the cabin deck raised the ship's center of gravity without taking into proper account the water levels in the ballast tanks" which further justifies my insight. 

Lessons to take 

This is another maritime accident to take lessons, but it costed to so many young lives. Maritime business requires serioussness. Accident has no mercy once it happened. Human errors, which accounted for 85% responsible in all maritime accidents; will not reduce in accidents waiting to happen; but number of accidents could decrease in a climate of more improved safety culture in maritime sector. All of as are accounted for this challenging task. 

Some compare this accident with the Costa Concordia accident. Well. In some point of view, Captain Schettino handled the emergency situation much better with much more passengers had been evacuated with less victims in comparison. But, he was luckier. He had much more time before the ship capsized. But, we must appreciate that except his very early flock out of the ship, and except the wrong maneuvering right before hitting the rocks Capt. Schettino did the right things to do in the emergency situation. But, every situation has it's exceptions. Let's see the end of judgements. 

A prayer for the poor victims. 
R.I.P.


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