SCHRIFTENREIHE SCHIFFBAU Festschrift anlässlich des 100 ...

It would be possible to provide the crews with diagrams showing the recommended
maximum speed in a given sea state in order not to mechanically overload the bow door
structures in ferries. It is not self-evident that the crew knows at which ship speed in a certain
seaway the sea loads can exceed the design loads of the ship structures.
It was further found that a core safety element of a Ro-Ro passenger ferry in case of a loss
of its watertight integrity is in fact a sufficient freeboard from the waterline in that equilibrium
floating condition to the vehicle deck. A sufficient freeboard prevents massive water ingress
into the ship and, consequently, a rapidly increasing heel. Prevention of the rapidly
increasing heel is a necessary condition for a successful evacuation of the passengers and
crew. Whenever modifications of the existing damage stability requirements for Ro-Ro
passenger ferries are discussed, this technical fact should be kept in mind.
In an ideal case the vehicle deck and ship should be designed so that in a possible damage
case the ship’s list does not exceed a certain maximum value, above which an orderly
evacuation is not anymore possible. All life saving appliances (LSA) should function properly
at least until this defined angle of list. There are various ways to achieve this, of which a high
freeboard is only one.
A potential water inflow onto the vehicle deck depends very strongly on the ship speed and
on the freeboard to the opening or leak. If the bow doors are regarded as potential openings,
locating them somewhat higher in the ship structure could improve safety. The freeboard of
the vehicle deck opening at the bow of the MV Estonia was about 2.8 m. If it had been e.g.
one meter more, that is 3.8 m, the amount of water ingress on the vehicle deck would have
been radically smaller and the changes of the MV Estonia to survive considerably higher.
Due to the bow wave a high freeboard on the bow is more important than elsewhere along
the waterline.
The evacuation possibilities of passengers in a ship having a heavy list should be
significantly improved: It is somewhat concerning that the evacuation or escape of the
passengers and crew in a ship with a list of more than 25°-35° is either very slow or
impossible. The MV Estonia case shows that if the vessel has a large open vehicle deck,
such an angle can be reached very rapidly, if there is a massive inflow of water onto the
vehicle deck.
When the MV Estonia’s list exceeded a certain limit the engines shut down automatically,
because the lubrication systems did not anymore work properly. Thus the (auxiliary) engines
providing electrical power tripped, when they could have been most needed. Without
sufficient electrical power the possibilities of the crew to influence the course of accident
were rather limited. Engines, which would keep running at higher heeling angles, could
provide better changes for the crew to rescue the ship and the passengers to evacuate.
A real evacuation may be one-sided to the higher side only. The number and location of life
saving appliances should be such that also in a one-sided evacuation no shortage is faced.
About 50 percent of the persons who got out of the ship survived. If life boats could have
been lowered at ship list in excess of 20° the casualty rate could have been considerably
lower. Some rafts turned upside down in seaway. The overwhelming reasons for the
casualties were drowning, hypothermia and a combination of both. This is not new.
Evacuation into water in the Baltic Sea is for most of the year not likely to end well.
According to the best available information the MV Estonia had heeling tanks connected with
a cross-flooding duct in between. In the duct there was a valve, which could be opened to let
water from one tank to another. In addition the ship was equipped with a system that opened
this valve automatically, when the WT-doors were centrally closed. It is further known that
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