There is clearly a lot of speculation about what happened on board the Costa Concordia that led to her tragic demise.  Was it a navigational error?  Did the electrical systems cause a loss of steering or propulsion?  Was it an uncharted rock?  Was the ship going too fast?

Here are some theories:

Navigational Error:

The Costa Concordia’s next port of call took the ship on a northbound route in between the island of Giglio and the Italian mainland.  We received a report that the island of Giglio was meant as more of a “fly-by” opportunity for the guests on board to take photos, and that the ship was not scheduled to stop there.  Upon completing their “fly-by”, there is speculation that the ship had tried to cut the corner by sailing through a narrow channel between Giglio and the small island of Cala Del Lazzaretto, however looking at the chart, this theory is HIGHLY unlikely.

Giglio chart island costa concordia map

Considering the depth of the waters in that area, what certainly appears possible is they laid their northbound track exactly adjacent and to the east of Cala Del Lazzaretto.  The above chart is certainly not the same scale chart as would be found on board the Costa Concordia, but as you can see, there’s plenty of open ocean for a cruise ship to depart safely.  Charting a course close to Cala Del Lazzarretto would have not have been the prudent decision.

Other speculation exists that the ship experienced an electrical issue a few hours out of her last port of Civitavecchia and that the captain had decided to bring the ship in toward Giglio

This does not add up.  A ship experiencing electrical problems that would affect the ship’s steering and/or propulsion systems does not approach shoal water or try to enter port without tugboat assistance.

Perhaps the ship’s power went out and she lost steering?

It’s certainly possible.  Her sistership, the Carnival Splendor experienced an engine room fire last year that left the ship dark and adrift for days off the coast of Mexico in 2010.  Power loss can happen for a number of reasons such as loss of seawater cooling to the engines, a blown circuit breaker, or a power overload situation.  Had the loss of power affected the ship’s steering gears, it might have sent the ship off course and into the rocks.

Considering the size of the ship, and her speed at the time, any such casualty in close proximity to shoal water would have likely led to this disaster.

Perhaps the steering system malfunctioned?

After doing some research on this particular vessel, it appears the Costa Concordia did not use “azipod“-type drives, rather she used conventional rudder and propellor shaft, “tail drive,” arrangement powered by a diesel-electric system.  Had the rudders experienced a mismatch scenario, where the rudders did not react exactly to the rudder orders of the helmsman, the ship would have sailed off course.

About 10 years ago I was on a US Navy destroyer when this exact situation occurred, the rudders went the opposite way of the ordered rudder angle.  Fortunately we were able to immediately take remote control of the rudders and essentially drive them by hand and a potential crisis was averted.

Is it possible this same situation occurred on the Costa Concordia?  Sure.  Was it the root cause of this disaster?  Probably not considering how much open water was available to leave the port safely.

Ship's Squat effect bernoulli

This picture describes the phenomenon of squat of a ship. It appears when a ship is moving with in a low depth of water under the skittle. 1: Deep water case. The ship floats by buoyancy. 2: Shallow water case. Water is compressed between the sea bed and the ship's body, and runs out faster. According to the Bernoulli's principle, the pressure decreases when the speed increases. A low ebb is formed, attracting the ship downwards. Before and after this hollow, the waves are also higher. via Wikipedia

Perhaps the ship was going too fast and it experienced a phenomenon called “ship’s squat”.

When large ships move through shallow water, they tend to squat, or sink down in the water.  This is essentially due to the Bernoulli effect.  The water directly under the hull is squeezed and forced to move faster than the water around the sides of the hull creating a low pressure area under the hull.  This phenomenon was determined to be the contributing factor in the grounding of the QE2 in 1992 off Martha’s Vineyard.  She was transiting through the channel at 24 knots and hit a submerged rock at a depth of 34 feet.  Her normal operating draft was 32.5 feet, however due to the squat effect, she ran hard aground.  The ship’s crew had estimated the squat effect had increased her draft by 2 feet, however investigators later estimated it to be between 4 and 8 feet.

Considering the size of the gash on the port side of the ship, she was certainly moving along smartly at the time, which would indicate that ship’s squat may have been a factor.

All that being said…

The port of Giglio does not have a narrow channel, it’s an open bay to the sea with deep navigable water all around.  Hence the fact they have constructed breakwaters around the port.  At this point in time, there does not appear to be any reasonable answer why the ship navigated so closely to the island of Cala Del Lazzarretto.

 

 

 

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