numerical investigations of the capsizing sequence of ss ... · scale capsizing or sinking events,...

Proceedings of the 11th International Conference on the Stability of

Ships and Ocean Vehicles, 23�28 September 2012, Athens, Greece, 1

Numerical Investigations of the Capsizing Sequence of

SS HERAKLION

Stefan Krüger, TU Hamburg Harburg, [email protected]

Hendrik Dankowski, TU Hamburg-Harburg, [email protected]

Caroline Teuscher, TU Hamburg-Harburg, [email protected]

ABSTRACT

The sinking of the RoRo- Passenger Ferry SS HEARKLION in 1966 was one of the most disastrous ferry accidents in modern Greek shipping. SS HERAKLION was originally built as combined freight and passenger vessel and was later converted into a RoRo- Passenger ship. Some technical aspects of the conversion were at least doubtful, however the ship started her final voyage on December 7 from Crete to Piraeus. The weather was rough, and the ship was travelling in a stern quartering sea condition with heavy beam winds. The rolling was strong, and after a course alteration into following seas the rolling increased. This caused cargo to shift and a side door was pushed open by a heavy truck which was not secured. Water entered into the car deck which resulted in a heavy list of the ship. When further water ingress took place, the ship the finally sank. After the accident, investigations were carried out at NTUA (on behalf of the Hellenic authorities) and at the Institute für Schiffbau (on behalf of the insurance company). There are some interesting aspects of the accident which are worth to be studied again by more advanced methods compared to the late 60s. Numerical evaluations of the accident (parts of this research were in close collaboration with NTUA, Ship Design Laboratory) have shown some interesting aspects of the earlier accident phase before and during the flooding of the main garage deck. The investigation has also shown options how the accident could have been avoided. The paper presents the treatment of complex full scale safety issues by numerical simulation methods. It shows that it is useful to apply different calculation methods for different phases of such accidents. The intact phase of the accident is treated by our seakeeping code E4ROLLS until water enters the car deck. The initial water ingress into the car deck is computed with Glim´s method until a certain list is reached, and some conclusions are drawn. The paper will also show that scientific advances in ship theory can help to better understand the accident roots of such complex accidents, and these methods can help to find new answers to old problems.

Keywords: SS HERAKLION, capsizing, passenger ferry, flooding of the vehicle deck

1. INTRODUCTION

Marine casualties are typically complex

event chains, especially when the casualty

leads to the total loss of a ship due to capsizing

or sinking. Whenever such a casualty needs to

be investigated, lots of computations need to be

made to figure out the event chain which has

lead to the final loss. During these

investigations, a variety of different

computational methods is applied, which

extends from simple hydrostatic calculations to

complex dynamic simulations. The problem

exists that all these methods require more or

less sophisticated computational models, and

both need to be validated. The validation of



Figure 1 SS LEICESTERSHIRE (top) and

SS HERAKLION (bottom) after the

conversion

such methods can be performed by computing

theoretical test cases, by the comparison with

experiments or by full scale accidents. The

validation by experiments has the advantage

that all data and test conditions are well

defined, which makes it quite easy to re

compute these accidents. Further, any

deviations between experiment and

computation can in most cases be reasonably

explained, and such deviations often result in

the refinement of the computational procedure

or in the model, or both. Therefore it is a

conditio sine qua non to validate numerical

methods by experiments. However, with

respect to marine casualties, experiments never

reflect the full event chain as they can only

focus on a small part of the problem, and they

are always performed under ideal conditions.

Therefore it seems plausible to also use full

scale accidents of ships for validation purposes.

But the problem exists that these accidents

never happen under ideal conditions where all

data is exactly known. Mostly the ship has

sunk and it cannot be accessed, important data

are not known with sufficient accuracy and the

surviving witnesses often do not clearly

remember important facts. This makes the

analysis of full scale accidents always

challenging, and often it is not clear whether a

numerical model or a computational procedure

is actually suitable for the analysis. Therefore,

TUHH is actually running a research project

where we systematically collect data of full

scale capsizing or sinking events, prepare the

calculation models and figure out the relevant

event chains. These data are collected in a

database which will be used for the validation

of other methods in the future. In the

framework of these investigations, we came

across the capsizing and sinking accident of SS

HERAKLION, which took place in 1966.

Although the accident was quite long ago and

the ship has nothing in common with modern

designs, the accident was characterized by a lot

of interesting technical details which made the

analysis quite challenging. Although no safety

recommendations can be drawn from this

accident, the technical analysis shows a variety

of interesting details which allow the validation

of a couple of computational methods. Our

analysis of the accident, which was done in

close collaboration with the National Technical

University of Athens (NTUA) is presented in

the following sections.

2. SHIP AND LOADING CONDITION

SS HERAKLION was originally built as SS

LEICESTERSHIRE by Fairfield Shipbuilding

and Engineering in 1949 as Hull No. 2562, call

sign SZNO. The ship was a typical design of a

combined freight and passenger vessel. 1964

the ship was bought by the Hellenic shipping

company Typaldos Lines, and she was

converted into a combined passenger and

vehicle ferry, see Fig. 1. This major conversion

showed already all later problems with RoRo-

Passenger- ferries, which was a new ship type

in those days and it was unclear for the

authorities how to deal with this type of ship.

Since 1949, additional safety requirements

were put in place, and additional transversal

bulkheads were retrofitted to meet a one

compartment status. This was not consequently

done, as Fig. 2 shows, because the additional

transversal bulkheads did not extent down to

the double bottom. An additional deck was

fitted to serve as vehicle deck, which was

accessed by side doors and ramps. As the

watertight transversal bulkheads did for



obvious reasons not extent above the vehicle

decks, the vehicle deck now was the freeboard

deck, which made a complete set of safety

relevant calculations necessary. An additional

passenger deck was also retrofitted which

resulted in a significant increase of the vertical

centre of gravity.

Figure 2 Sketch of SS HERAKLION after

the conversion. The side door of the forward

vehicle deck can also be seen.

However, during the conversion some

existing regulations could not or only hardly be

fulfilled, a fact which was later proven during

the accident investigations. Therefore, the

issuing of some certificates was doubtful, and

was also later withdrawn by the Hellenic

authorities.

The main dimensions of the ship after the

conversion were the following: Length over all

146.50 m, moulded breadth 18.29 m, draft

design 4.58m, depth to freeboard deck 5.35 m,

depth to upper deck 10.851m, speed 17 knots.

During the accident investigations by the

Hellenic authorities it was found quite

challenging to figure out the stability condition

of the vessel during her final voyage. An

inclining experiment with SS HERAKLION

was never performed, and the stability

information on the vessel was extremely poor.

During the accident investigations, the light

ship weight of SS HEARKLION was

determined by Fragoulis (Fragoulis 1967) and

Georgiadis (Georgiadis 1967). They used the

available data of the inclining experiment of

sister vessel SS XANIA instead and considered

some additional weights and also some that

were not on board of SS HERAKLION. The

loading condition of the final voyage was

based on the available loading list and

contained cars, trucks, passengers, ballast and

bunker and stores. However, some information

was doubtful, also the inclining experiment

performed with SS XANIA, which was based

on level trim hydrostatics and small

inclinations. Further, SS XANIA had a large

amount of ballast water on board during the

inclining experiment which also made the

results doubtful. Some tank volumes were

incorrect, too, and also the hydrostatic

particulars were not fully available in the

AEENA- accident reports. Therefore we had

decided to recalculate all weight information,

including a new evaluation of the inclining

experiment (Teuscher 2011). This step was also

necessary to generate the weight information

for the mass moments of inertia computation

for the dznamic analysis. It was found that due

to the conversion, the centre of gravity was that

high that the ship could only be operated when

the complete double bottom fuel oil tanks were

filled with ballast water. The loading condition

during the final voyage resulted then in a total

displacement of 7740 tons, draft at A.P. 6.35

m, Draft at F.P. 2.95 m, GMc 0.94m, freeboard

to vehicle deck of abt. 0.85 m. The tank fillings

of the loading condition according to our

investigation is plotted in Fig. 3 (Teuscher

2011)

Figure 3 Loading Condition of the final

voyage.

3. THE FINAL VOYAGE

On December 7th

, 1966 SS HERAKLION

departed from the port of Souda Bay, Crete to

make her voyage to the port of Piraeus. The

departure of the vessel was delayed due to the

late arrival of a reefer truck, which was then



stowed unlashed in the forward garage deck

rectangular to the ship´s centre line. At about

22.00 hrs, the ship reached the open sea close

to the island of Milos (see Fig. 4), steering a

course of 352 degree. The wind was rough with

8 Bft (11 in gales). As the wind direction had

changed overnight from about 180 degree to

now 270 degree, the direction of the waves was

still about 200 degree, bringing SS

HERAKLION into the interesting situation of

beam wind and stern quartering seas (see Fig.

4). The sea was rough with significant wave

heights about 5-6 m, (significant) wave length

between 80 and 120 m. The weather data were

not recorded during the accident, but were later

obtained from the German DWD (Wendel

1970).

Figure 4 Accident scenario of SS

HEARKLION. Source: AEENA.

Due to the beam wind, SS HERAKLION

had a steady heel to starboard side of about 8

Degree. Due to the seastate, the ship was

permanently rolling with amplitudes about 20

degree, as the surviving persons reported. This

rolling motion caused the cargo to shift, and

some cars tippled over. This cargo shift

increased the steady list of SS HERAKLION to

about 11 degrees. The crew decided to alter the

course to 20 Degree to bring SS HERAKLION

directly before the seas. She was now travelling

in following seas and beam wind. Despite the

course alteration, the rolling motion increased,

and due to the severe rolling, the unlashed

reefer truck pushed against the starboard side

door and forced the door open. Due to the

steady list of about 11 Degree and the roll

motion, water immediately entered the vehicle

deck which caused a list of about 60 degree.

Due to unsecured openings, further

compartments were flooded, the vessel finally

capsized and sank. Only 46 persons of 264

could be saved, this made the SS

HERAKLION accident the most disastrous

marine casualty in Modern Greek shipping.

4. ANALYSIS OF THE ROLL MOTION

IN INTACT CONDITION

4.1 General Considerations

The accident of SS HEARKLION can be

split into four different phases, which do all

have some interesting technical challenges: The

first phase is the intact rolling in a beam wind

following sea scenario. The second phase took

place after the alteration of the course, which

made the rolling even worse and lead to the

opening of the side door. The third phase is

characterized by the flooding of the vehicle

deck until the ship reaches a large list, and the

fourth phase is the subsequent flooding of

further compartments including the

superstructure until the ship finally sinks. This

paper deals with the first three phases of the

accident: Because it is obvious that these

phases are strongly influenced by dynamic

effects, they can only be analyzed with

methods which compute the roll motion in

following seas with sufficient accuracy.

Although many tanks were filled, free surface

effects can be disregarded, as most tanks were

completely filled. The flooding of the vehicle



deck can also be computed taking into account

the relevant dynamics, as the fluid motion

influences the ship motion and vice versa. The

relative motion between the ship and the wavy

surface triggers the in- and outflow of the water

on deck and needs to computed with sufficient

accuracy. For these computations, we use the

seakeeping code E4ROLLS which was

originally developed by Söding and Kröger for

the investigation of the ELMA- T.R.E.S.

capsizing accident in 1986. E4ROLLS

simulates all six degrees of freedom in time

domain. The concept is that those degrees of

freedom which are governed by hydrodynamic

effects are computed linearly using RAOs (e.g.

from a strip theory or panel code), whereas a

non linear simulation is performed for those

degree of freedom where the nonlinearities are

the governing effects. The equation used for

the roll motion reads:

Here, Mwave denotes the direct roll moment

obtained from the roll RAO, and h is the

righting lever in waves computed by the

concept of Grim´s equivalent wave (Grim

1960). The latter makes the computation

extremely fast and at the same time reliable.

E4ROLLS was intensively validated by model

tests during German BMBF- funded research

programs from 1998-2006.

Figure 5 Principle of Grim´s equivalent

wave (Grim 1960).

4.2 Stability, roll motion and critical

resonances

Figure 6 Polar Plot of significant wave

heights required for a 25 Degree roll angle of

SS HERAKLION in intact condition, 8s period

Figure 6 shows the results of an E4ROLLS-

computation for the final voyage of SS

HERAKLION, intact condition. The polar plot

was computed for a significant period of 8 s,

corresponding to a wave length of 100 m. The

seastate is represented by a JONSWAP-

spectrum, the radial energy distribution follows

a cos2 - function. This leads to a short crested,

natural seaway. The polar plot shows the

required significant wave height which lead to

a roll angle of 25 Degree (abt. 8 Degree STB

static heel due to wind plus the roll amplitude).

For each node of the polar, 10 simulations of

20000 s each have been performed for each

significant wave height, and the wave height

was varied in steps until 25 degree roll angle

were reached. The radial rings show the ship

speed, the circumferential axis shows the

encounter angle. Beam wind was assumed from

270 Degree (90 degree PS), this is the reason

why the polar plot is not symmetric. From

these results, some interesting conclusions can

be drawn. The computations show that in the

accident situation of SS HEARKLION, roll

amplitudes of about 20 degree - as reported -

were likely to occur, as the required significant

wave heights are about 5-6m. This value is

typical for wave lengths of 100 m- 120 m, as

reported by the German DWD for the day of

the accident (Wendel 70 and AEENA-

( ) ( )[ ]( )ϕϑϕψ

ϕϕψψϕϕϑϑζϕ

cossin

cossin)( 22

+−

+−+−−−−+++=

xzxx

xzsdTankwavesywind

II

IhgmMMMMM &&&&&&&&

&&



Reports). Most interesting is the fact that SS

HEARKLION was travelling close to the 1:1

roll resonance situation in following seas.

Based on the Stillwater GM of 0.94 m and

valid for small angles only, the natural roll

period of SS HERAKLION amounts to 14.6 s.

This results in a theoretical speed of 12.5 kn in

following seas at an encounter angle of 30

degree, which is approximately the encounter

angle of SS HERAKLION before her first

change in course. The polar shows the well

known fact that resonance situations in

following seas are not distinct points - as a

linear theory might suggest - but more or less

broad banded resonance areas which extent

over a range of speeds and encounter angles.

This behaviour is a consequence of the fact that

the natural roll period of a ship in following

seas is not a fixed value, but is varies due to

several nonlinearities. For the accident

situation of SS HERAKLION, the following

nonlinearities occur (see also Fig. 7):

• As the righting lever curve of SS

HEARKLION is of progressive type

(positive form stability),, the natural

roll period decreases with increasing

roll angle or list. For the SS

HERAKLION, the steady list due to

wind and cargo shift plays a major

role, and the larger the steady list

becomes, the smaller becomes the

roll period.

• For the roll period in waves, the

stillwater righting lever curve is not

relevant, but (as the two extremes)

he crest and through leverarm curve.

The stability varies between these

two situations, and the resulting roll

period depends on how long these

extreme phases occur during one

cycle. The resulting roll period is

longer compared to the computed

Stillwater period.

• The roll angle itself has an influence

on the roll period, especially when

the crest and through curves are

analyzed. For smaller roll angles up

to approx. 15 degree, the roll period

decreases, for larger roll angles

larger than 15 degree, the roll period

increases.

Figure 7 Righting levers of SS

HERAKLION for Stillwater, crest and trough

conditions. Computations by Wendel (Wendel

1970), coloured curves our computations.

This is underlined by Figure 7, where the

righting lever curves in waves of SS

HERAKLION have been computed by Wendel

(Wendel 1970) for a 100 m wave, wave height

7 m. The mean value between crest and trough

(used by Wendel for his analyses) differs

significantly from the Stillwater curve (blue

line), an indication for the fact that any

conclusion from the Stillwater natural roll

period (for small angles) is not valid for the SS

HERAKLION accident.

Figure 8 Polar Plot of significant wave

heights required for a 25 Degree roll angle of

SS HERAKLION in intact condition, 8.5s

period.



All these findings are confirmed if the

computation is repeated for another possible

accident scenario. Fig, 8 shows the limiting

significant wave height now for a significant

period of 8.5s (113 m corresponding wave

length). It can now even better be observed

how close SS HERAKLION sails at the 1:1

resonance and that the alteration of the course

did not improve the situation.

4.3 Conclusions for the first two phases

As shown, SS HERAKLION was travelling

sufficiently close to the 1:1 following sea

resonance situation, so that large rolling angles

occurred. The polar also shows that changing

the course was not a good choice, as the rolling

motion was not reduced. The reason is that the

ship was brought closer to the resonance at

following seas, but the direct excitation (MWave

in the roll angle equation) due to the waves was

reduced slightly when SS HERAKLION took

the waves exactly from abaft.

Figure 9 Horizontal accelerations computed

for SS HERAKLION in the accident situation

prior to the course alteration

From Fig. 6 and Fig. 8 the fact can be

derived that the whole accident could have

been avoided if the crew had decided to select

another course or speed combination. At that

course, SS HERAKLION was clearly safe

below a speed of 10 knots, and if she had opted

for a course with bow quartering wind (e.g. 60

or 75 Degree STB) she could have sailed

nearly any speed without being endangered.

Even sailing at a higher speed than 15 knots

would have improved the situation, but

slightly. May be it was due the fact that SS

HEARKLION was already delayed that the

crew did not want to increase the delay by

reducing speed or changing course. But had the

crew done so, the accident could have been

most probably avoided. In this respect, the SS

HEARKLION accident is comparable to the

loss of MV FINNBIRCH in 2005 and SS

FIDAMUS in 1949, both ships capsized in

following seas close to a 1:1 resonance (Kluwe

and Krüger 2008). But there can be no doubt

that SS HERAKLION was quite safe from the

intact stability point of view, as our

computations show. Fig 9 shows the horizontal

acceleration computed for SS HERAKLION

during the accident situation. It can be seen that

accelerations of about 0.5 g occur to starboard

side, this is sufficient to let the cargo tip over.

5. ANALYSIS OF THE WATER

INGRESS INTO THE VEHICLE

DECK

5.1 General considerations

The sinking of SS HERAKLION took place

when the reefer truck struck against the STB-

side door, pushed it open, which allowed water

to enter the vehicle deck. It was shown in the

accident investigations by Fragoulis,

Georgiadis and Antoniou (Fragoulis 1967,

Georgiadis and Antoniou1967) and by Wendel

(Wendel 1970) that the flooding of the vehicle

deck resulted in such a loss of buoyancy that

the ship irreversibly must have capsized. But a

more precise stability computation (loss of

buoyancy method, free trimming righting

levers) gives a more complex picture, as Fig.

10 shows:



Figure 10 Righting levers computed for SS

HERAKLION after the flooding of the forward

car deck.

Figure 10 shows the computation of the

righting levers of SS HERAKLION after the

forward car deck is flooded. The computation

assumes the complete superstructure to be

watertight, as water will gradually enter these

compartments. The heeling moment of the

tippled cars has been taken into account, and

also the heeling moment due to wind of 8 Bft,

which must be added for the situation when the

reefer truck struck the car deck open. From

these calculations, it becomes obvious that after

the flooding of the car deck, two equilibria

exist, where the first equilibrium is about 10

degree STB. This first equilibrium is only

theoretically stable, because a larger wind

heeling moment (gales were reported to be

about 11 Bft) is sufficient to let the ship heel to

about 45 degree STB. It is also possible that

the wave moments from the seastate force

sufficient water into the vehicle deck to

overcome this first stability plateau. But this

computation shows that SS HEARKLION was

not necessarily lost when the STB side door

was pushed open: If the crew had managed to

turn her in such a way that the wind heeling

moment would have acted from STB side on

the vessel, she would have had chances to

survive even the water ingress. This possible

scenario will also be analyzed in the following

sections. Further, even the equilibrium at about

45 degree is stable. Figure 11 shows the

floating position of SS HERAKLION after the

complete flooding of the car deck including the

wind heeling moment from PS.

Figure 11 Floating position of SS

HERAKLION after the flooding of the vehicle

deck

Figure 11 shows that SS HERAKLION must

not necessarily sink or capsize even after the

most unfavourable combination of heeling

moments (tippled cars at STB, wind from PS).

If the crew had followed the relevant guidelines

and kept all weather tight doors and openings

closed, the ship could have stayed in that

position. It was however unclear during the

accident investigations if and how internal

progressive flooding has taken place. Of course

these computations depend on the assumptions

made, where the largest uncertainty lies in the

masses and centroids. If the stability of SS

HERAKLION had been smaller than

computed, the first stability plateau might

become completely unstable, which forces the

vessel to heel to about 50 Degree STB even

without additional external moments. However,

these computations indicate that based on our

assumptions the ship had had a good chance to

survive the accident if the crew had taken other

operational decisions.

5.2 Numerical simulations of the water

ingress with E4ROLLS

At present, we have two different methods to

compute water ingress into vehicle decks: The

first is E4ROLLS, which has been extended for

water on deck problems by Petey (Petey 1988).

The floodwater is modelled by Glim´s method

using shallow water equations. The inflow into

the vehicle deck is computed by the net flux

through the opening including the dynamics of

the roll motion. This method gives good results



(BSU 2010) when the amount of water

accumulated in the vehicle deck is small

compared to the total mass of the ship and

when the water inflow does not strongly

influence the trim. Because in E4ROLLS only

the additional roll moment (see MTank in Eqn.

1) is modelled, the mass increase and trim

moment are neglected at present (we are

currently improving this). Further, as the direct

wave moment (see MWave in Eqn. 1) is obtained

from the linear RAO, the results become less

reliable when a certain static heel (typically 30

to 40 degree) is reached. From practical

considerations, this is not a problem because

the ship can be assumed as lost in case such

large static heeling angles are reached. Further,

we have developed a method for sinking

computations E4SINKING (Dankowski 2011),

which computes the static flux through the

relevant openings and determines a hydrostatic

equilibrium according to the added mass

method. Dynamic effects can roughly be taken

into account if the relative motion between ship

and opening is computed (e.g. by E4ROLLS)

and used for the flux computations. This

method is of course more robust and for the

desired purpose less precise, as the dynamics

are underestimated. When analyzing the SS

HERAKLION accident, Teuscher (Teuscher

2011) has checked both methods and found

that they converged with respect to the most

important results (flooding times and

floodwater amount). We will in the following

present the results obtained from E4ROLLS for

the flooding of the vehicle deck.

Figure 12: Time plot of the roll angle (top) and

the volume in the vehicle compartment (sum of

the curves in the bottom plot), accident

scenario

Figure 12 shows the computed time series for

SS HERAKLION after the STB side door was

pushed open. The computation was made for a

speed of 15 knots, encounter angle 0, wind

8Bft, significant period 8.5 s, significant wave

height 5 m. The vehicle deck was modelled by

two compartments to take into account the

sheer, therefore the total volume is the sum of

these two (see Fig. 12, bottom time series). The

hydrostatic computation resulted in about

1800t water accumulated in the vehicle deck at

the equilibrium of about 45 degree. This

coincides with the dynamic results obtained

from E4ROLLS, where the static equilibrium is

computed somewhat larger at slightly larger

volumes in the vehicle deck. The first phase of

the flooding shows that it takes approximately

500 s to flood the vehicle deck and to pass the

first stability plateau, because the water inflow

is forced into the ship by the motion. After this

situation is reached, the vessel oscillates around

this condition, but we have assumed that course

and speed are kept during the simulation. It is

now interesting to analyze alternative scenarios

to check whether there had been additional

possibilities to prevent the accident. In his

investigations, Wendel (Wendel 1970) has

suggested that the ship should take the wind

from abaft and the waves from STB stern

quartering. The idea was to get rid of the wind

heeling moment by a starboard turn.

Unfortunately, numerical simulations by



Teuscher (Teuscher 2011) have shown that SS

HERAKLION would also have capsized

during this manoeuvre. We have thought about

another alternative which we present here for

the first time, see Fig. 13. There, a turn to PS is

computed. The open side door is now exposed

to the sea, but the vessel has turned into a head

wind condition. The ship is - like in the

scenario suggested by Wendel - not exposed to

the beam wind anymore, and the heeling

moment becomes smaller. The main difference

between the two scenarios is that now, the

water is entrapped in the vehicle deck, as the

ship heels to PS. This heeling increases the

freeboard further, and the situation converges

Figure 13: Time plot of the roll angle (top) and

the volume in the vehicle compartment (sum of

the curves in the bottom plot), alternative

scenario

into a condition where the amount of water on

deck does not increase further. The ship

remains stable at about 25 Degree heel to port

side, where about 500 t of floodwater have now

accumulated on the deck. It is quite probable

that this manoeuvre - a turn to PS - would have

saved the vehicle deck from being completely

flooded.

5.3 Conclusions for the water ingress

The numerical simulations of the water

ingress into the vehicle deck have shown

reasonable results. The re computation of the

accident scenario have shown that based on our

assumptions, the vehicle deck is flooded and

the ship takes a large heel. But the simulations

have also shown that the ship was not

necessarily lost when the refer truck opened the

side door: The ship had some residual stability

left even with the flooded vehicle deck, and if

the heeling moment could have been reduced,

the capsizing might have been prevented. The

dynamics of the roll motion plus the wind

heeling moment plus the moment of the tippled

cars was too severe, and the residual stability

was then lost. But the calculations have also

shown that the ship could have been saved if

the crew had turned her immediately to port

side. In this situation, the open side door

would have been directly exposed to the sea,

which would have resulted in a PS heel. This

PS heel would have led to a stable equilibrium

floating condition with about 500 t of water

entrapped in the vehicle deck, and the ship

would have - according to our computations -

survived.

6. CONCLUSIONS

The capsizing accident of SS HERAKLION

was analyzed with numerical methods. It could

be shown that the application of such methods

to marine casualties - even if they are some

time ago - can show new facets of such

accidents that are worth a scientific

investigation. In the present case, the accident



analysis came to a plausible event chain which

is in line with the known facts and the

observations of surviving witnesses. This is

most important with respect to actual marine

casualties, as it is important to use only

validated methods and procedures for the

evaluation of such accidents. The evaluation of

the capsizing event of SS HERAKLION could

plausibly show that it might have been possible

to avoid the accident by operational measures,

and this finding might be of some use with

respect to the education of seafarers. However,

the accident of SS HERAKLION has also

shown that several safety rules were not

followed, and it is most important that we obey

all the existing rules strictly: All maritime

casualties which we have investigated at our

institute always showed a massive violation of

existing safety regulations.

7. ACKNOWLEDMENTS

The authors wish to thank Prof. Dr. Ing. S.

Kastner, Univ. Bremen, for having initiated

this work. We further thank Prof. Dr.- Ing. A.

Papanikolau, Ship Design Laboraratory, NTUA

for the excellent cooperation.

8. REFERENCES

AEENA (Hellenic Maritime Accident

Investigation Board) 1967 “Official Report

HERAKLION”, Original in Greece, 1967,

Athens

BSU Bundesstelle für Seeunfalluntersuchung

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ORTGAL UNO am 13. Januar 2010

westlich von Irland (Foundering of FK

ORTEGAL UNO 13th of January, 2010,

west of Ireland). BSU Report 07/10,

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Georgiadis, S. Antoniou A 1967, " Expertise on

the Sinking of SS HERAKLION". AEENA,

Official Investigation Report, Athens 1967,

Addendum No 5 (Original in Greece)

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Schiffes im Seegang". Schiffstechnik 1960

Fragoulis, 1967, " Expertise on the Sinking of

SS HERAKLION". AEENA, Official

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Addendum No. 2, (Original in Greece)

Kluwe, F. Krüger, S. 2008, "Evaluation of

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aus Bewegungssimulationen." Rep. 487.

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des Seeunfalles von MS HERAKLION

unter besonderer Berücksichtigung des

dynamischen Verhaltens im Seegang", BSc

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Wendel K. 1970, “Gutachten über den

Untergang des Fährschiffes HERAKLION

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numerical investigations of the capsizing sequence of ss ... · scale capsizing or sinking events,...

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