CHAPTER 5 THE CIRCUMSTANCES OF THE VOYAGE

The ESTONIA operated on the route between Tallinn and Stockholm. She left Tallinn every second night at 1900 hrs and arrived in Stockholm the next morning at 0900 hrs local time. She left Stockholm the same day at 1730 hrs local time and was back in Tallinn the next morning at 0900 hrs. As the vessel was in port a great part of the day a late arrival did not affect the next departure.
In Tallinn the ship had her starboard side to the berth and the cargo was handled via the forward ramp. In Stockholm the ship docked in Frihamnen, and there also she had her starboard side to the berth. All ro-ro cargo handling in Stockholm took place via the aft ramps.
Normal passage through the Stockholm Archipelago was via Sandhamn, but when the weather conditions were considered unfavourable, the passage was via Söderarm.
The total distance between Tallinn and Stockholm via Sandhamn is 225 nautical miles and via Söderarm 228 nautical miles. To keep the schedule, the required average speed in unrestricted waters between Tallinn and Stockholm was 16.5 knots via Sandhamn and 17.0 knots via Söderarm. The normal time for entering the Stockholm Archipelago by the Sandhamn passage was 0515 hrs at the Revengegrundet lighthouse, and by the Söderarm passage 0425 hrs at the Söderarm lighthouse.
The voyages were very regular and, according to the log book at Stockholm Pilot station, the passing times at the Söderarm lighthouse did not vary more than about 15 minutes.

On departure from Tallinn on 27 September the ESTONIA was seaworthy and properly manned. There were no outstanding items either from the authorities or from the classification society's surveys. The maintenance standard of the vessel was good as witnessed by various instances.
During the last day in Tallinn the vessel was used in a training programme for Estonian Maritime Administration surveyors in the conducting of a Port State Control in compliance with the Paris Memorandum of Understanding on Port State Control (see about Paris MOU in 9.1). The trainees made a thorough Port State Control inspection of the ESTONIA and were supervised and instructed by two senior inspectors from the Swedish Maritime Administration. The exercise was documented in protocol, set up in a form according to the Paris MOU. A copy of this protocol is included in the Supplement.
The Swedish inspectors leading the exercise have been interrogated by the Commission and have stated that the vessel was in good condition and very well maintained. They found no deficiencies that would have caused detention or other serious remark, if the inspection had been a regular Port State Control. However, some deficiencies were noted, such as that the rubber seals for the bow visor were worn, had tear marks in some places, and were in need of replacement, and watertight hatch covers on the car deck were open and in a condition indicating that at least one was not normally closed. It was also stated during the interrogation that the Swedish inspectors had experienced “lack of respect for issues related to load line matters” in their contact with officers met during the exercise.

The vessel had on departure from Tallinn a loading condition that was normal for the route. The car deck contained mainly cargo vehicles. The bunker and stores condition was based on the normal routine of supply during the stop in Stockholm. The trucks and trailers were identified on the cargo manifest for the voyage, giving information about vehicle identity, length, weight and content in general.
Due to uneven weight distribution on departure the vessel's port side heeling tank was filled.
Instructions had been given by the chief officer to secure the heavy cargo carefully due to the forecast heavy weather.
Table 5.1 gives the departure condition of the ESTONIA. Deadweight on departure has been estimated to a total of about 2300 t as detailed in Table 5.1. Quantities of oils and water have been estimated by Nordström & Thulin, based on the normal consumption rates and replenishment routines. The weight of the heavy vehicles is taken from the cargo manifest. One truck included in the custom list but not in the cargo manifest has been added to the weight given in the cargo manifest. The number of passenger cars, vans and buses is taken from the custom list. Their weight is an estimate. The hydrostatic particulars are based on calculations by the NAPA program assuming a water density of 1.01 t/m³. The transverse metacentric height of 1.17 m includes the correction due to free liquid surfaces. According to the valid stability booklet the minimum required metacentric height was 0.63 m.

Table 5.1 Departure condition.

Deadweight
Heavy fuel oil (IFO 180)
tank 10	108 m3
tank 11	108 m3
daytank 36	25 m3
settling tank 38	20 m3
Total	261 m3	250 t
Marine diesel oil
tank 18	33 m3
tank 41	10 m3
Total	43 m3	35 t
Gas oil
tank 20	12 m3	10 t
Ballast water
tank 1	175 m3
tank 13+14	183 m3
Total	358 m3	360 t
Fresh water		300 t
Miscellaneous liquids		50 t
Weight on the car deck
Cargo vehicles, 40 units, 1000 t
Passenger cars, 25 units, vans, 9 units, buses, 2 units, 100 t
Total		1100 t
Crew and passengers		100 t
Miscellaneous		95 t
Total deadweight		2300 t
Floating Condition
Draught mean		5.390 m
Trim, positive by stern		0.435 m
Displacement		11930 m3
Longitudinal CG from aft. perp.		63.85 m
Vertical CG from keel		10.62 m
Transverse metacentric height		1.17 m

Prior to departure from Tallinn the vessel had received the route-adapted weather forecast from the Swedish Meteorological and Hydrological Institute (SMHI) in accordance with the subscription arrangement. The forecast, issued on 27 September at 1311 hrs, was transmitted by fax and acknowledged by the ESTONIA in the afternoon. It contained the information shown in Table 5.2.

Table 5.2 Weather forecast from SMHI.

Stretch	Time LT	Mean wind speed on 10 m level (m/s)	Prob. for mean wind >15 m/s in %	Wave height
				sign (m)	max (m)
Naissaar - N Osmussaar	20-22	S-SW 10-15	20	1.0-2.0	3.0
N Osmussaar - S Bogskär	22-04	SW-W 15-20	70	2.5-3.5	5.5
S Bogskär - Sandhamn	04-07	W-NW 18-25	90	3.5-2.0	5.5
Comments: Intense low near Oslo moving E-ward via southern Sea of Bothnia to southern Finland. It will cause increasing SW- later W-NW, from to night gusty wind. At dep. rain with mod vis. Later some short showers.

In Tallinn the Harbour Authorities forwarded the weather forecasts given by the Estonian Meteorological and Hydrological Institute (EMHI) to ships in port. The forecast distributed during the morning of 27 September predicted south-westerly wind of 12-17 m/s with a wave height of 2-3 m for the Northern Baltic area. At 1230 hrs a new warning message was issued, forecasting the wind to increase to 17-20 m/s, veering to west in the morning of 28 September.
Prior to departure the vessel also had the use of weather forecasts from the Estonian and Finnish regular broadcasting stations and coastal radio stations on VHF or MF and via the NAVTEX system.
The NAVTEX message - transmitted by Stockholm Radio on the morning of 27 September - forecast the wind to be SW 10-13 m/s, increasing first to 17-22 m/s and during the night to 20-25 m/s and veering to west.
After departure, marine weather forecast for the Northern Baltic and the Gulf of Finland could have been received on VHF. The forecasts transmitted during the night of 27 September by Tallinn Radio, Helsinki Radio and Mariehamn Radio all included warnings of winds of 20 to 25 m/s from a westerly direction.

Prevailing weather

The weather situation on 27 and 28 September 1994 has been analysed by the SMHI, FMI and EMHI. The reports of the analyses are given in full in the Supplement.
According to the reports there was a severe depression covering Northern Scandinavia and the Norwegian Sea. One of the low-pressure centres intensified on 27 September and moved rapidly eastward via southern Norway and eastern Sweden to southern Finland. The depression deepened and was located over Oslo on 27 September at 1400 hrs with pressure 987 hPa. On 28 September at 0200 hrs it was over the south-eastern part of the Gulf of Bothnia with 982 hPa, and at 1400 hrs over eastern Finland with 985 hPa.
A warm front, associated with this low, together with an area of rain, moved quickly eastward during the evening of the 27th over the northern Baltic Sea. South and south-west of the low, the wind shifted from south-westerly to westerly, and then became very gusty.
The wind direction, the mean and the maximum wind speeds in m/s at the most relevant observation sites are shown in Table 5.3. The indicated maximum values are the highest mean value for any 10-minute period during the preceding three hours except for Ristna, where the maximum values are measured in gusts. Maximum wind speed in gusts was also recorded at Bogskär and was 24.6 m/s at 2246 hrs on 27 September and 27.7 m/s at 0625 hrs on 28 September.

Table 5.3 Wind observations.

Day/ time	Söder- arm	Svenska Högarna	Bog- skär	Utö	Rus- sarö	Ristna
27/9 1700 hours	SW 09 mean 12 max.	SW 12 mean 14 max	SW 13 mean 14 max	SW 09 mean -	WSW 09 mean -	SW 08 mean 12 max
27/9 2000 hours	SW 11 mean 13 max	SSW 14 mean 16 max	S 14 mean 17 max	SSW 13 mean -	SW 08 mean -	SSW 08 mean 14 max
27/9 2300 hours	S 13 mean 17 max	SW 16 mean 18 max	SW 17 mean 18 max	SW 15 mean -	S 16 mean -	WSW 16 mean 21 max
28/9 0200 hours	SW 14 mean 15 max	W 17 mean 18 max	SW 20 mean 21 max	SW 15 mean -	SW 12 mean -	WSW 15 mean 22 max
28/9 0500 hours	W 20 mean 20 max	WNW 24 mean 24 max	W 19 mean 22 max	WSW 15 mean -	WSW 12 mean -	W 18 mean 29 max
28/9 0800 hours	WNW 17 mean 20 max	WNW 18 mean 25 max	WNW 21 mean 24 max	WNW 13 mean -	WNW 09 mean -	W 17 mean 26 max
28/9 1100 hours	WNW 12 mean 17 max	WNW 14 mean 18 max	- - -	W 15 mean -	WNW 11 mean -	W 12 mean -
For locations of the observation sites, see Figure 13.1.

5.4.2 Waves

Wave conditions for the night of the accident have afterwards been calculated by the Finnish, Swedish and German institutes of marine research, MTL, SMHI and DW respectively, using their own numerical models of wave growth. The most important input data to the wave calculation models were the estimates of area sea wind speed and direction for a certain time period before and after the accident. The basic wind data were provided by the national meteorological institutes.
Wave calculation models predict the significant wave height, wave period and mean wave direction at different points of the sea area under consideration. Significant wave height is defined in the numerical models by the area under the wave spectrum, but is very close to the statistical measure of the mean value of the highest one-third of the waves.
Table 5.4 shows the significant wave height Hs, spectrum peak or modal wave period Tp, and the mean direction of the waves predicted by the Finnish, Swedish and German institutes of marine research before, during and after the accident.

Table 5.4 Summary of wave conditions.

Institute	Position	Time day, hrs	Hs [m]	Tp [s]	Mean dir. [deg.]
MTL, Finland	59° 25', 22° 35'	27.9, 2300	3	7	260
SMHI, Sweden	59° 25', 22° 35'	27.9, 2300	2.9	7.1	246
MTL	Accident site	28.9, 0100	4.0	7.8	260
SMHI	Accident site	28.9, 0100	4.1	8.4	214
MTL	Accident site	28.9, 0200	4.4	8.2	260
SMHI	Accident site	28.9, 0200	4.3	8.7	217
DW, Germany	Accident site	28.9, 0200	4.3	8.3	218
MTL	Accident site	28.9, 0800	5.0	8.7	270
SMHI	Accident site	28.9, 0800	5.4	9.7	236

MTL experience is that the root-mean-square error in predicted significant wave height is about 0.5 m, in wave period about 1 s, and in wave direction about 10°.
Due to the wind shift six hours before the accident, waves were at the time of the accident still duration-limited. If the wind direction had remained constant, the waves would have been fetch-limited, significant wave height could have been about 5 m and the modal period about 10 s. This gives the absolute upper limit for the significant wave height.
Numerical predictions by MTL show that significant wave height may increase significantly in shallow water due to focusing of refracted waves. The minimum water depth in the accident area as verified by the Finnish Maritime Administration was over 40 m, which means that there was no shallow-water effect on the route of the ESTONIA.
Numerous studies of wave statistics in a seaway show that during a short interval when the significant wave height may be assumed constant, the distribution of measured wave crest-to-trough heights and heights of individual wave crests and troughs follow closely the Rayleigh distribution. Table 5.5 shows probabilities of an individual wave height exceeding different levels determined by the Rayleigh distribution. Wave height is given in a non-dimensional form divided by the significant wave height.

Table 5.5 Short-term wave height exceeding probabilities.

Height/HS	Prob. of exceedance
1	0.14
1.5	0.01
2	0.00034
2.2	0.0001

Thus, if the significant wave height is 4 m, one wave in 100 will be higher than about 6 m. Often as a rule of thumb the maximum wave height is estimated as twice the significant height.
The calculated significant wave height of about 4 m agrees well with visual observations made on board vessels which took part in the rescue operations. Masters of these vessels have estimated that before the accident waves were not higher than 5-6 m while after the accident individual waves were up to 7-8 m high and in general the wave height was 4-6 m. The estimates of wave height by the Swedish helicopter pilots who arrived at the accident site between 0350 hrs and 0645 hrs vary more than estimates by the mariners. A majority of the pilots have given estimates between 5-6 m or 6-8 m, one pilot gave 6-9 m and another 6-10 m. One pilot reports even a single very high wave of 12 m height measured by radar.

5.4.3 Light conditions and visibility

During the night of the accident the moon was about half in the last quarter. Moonrise was at about 2150 hrs and sunrise at about 0625 hrs.

Pictures from weather radars (Figure 5.1) show that broken cloud fronts were passing over the Northern Baltic and the accident area at about the time of the accident.

Figure 5.1 Cloud fronts over the Northern Baltic on 28 September 1994 at 0130 hrs (Finnish Meteorological Institute).

The night was cloudy with an occasional clearing of the sky just before midnight. After midnight the cloud coverage gradually increased again and in the early morning the sky was cloudy.
For most of the night visibility was more than ten nautical miles, but was occasionally reduced by rain showers.

5.4.4 Hydrological conditions

Currents were not measured during the night of the accident in the northern Baltic. However, the surface current speed and direction were later estimated by both MTL and SMHI.
According to MTL the velocity of the surface current was between 0.2 and 0.6 knots in an easterly direction at the time of the accident. The velocity of the current was estimated by SMHI to be 0.5 knots in a direction between east and north east.
A surface water temperature of between 12°C and 13°C was measured in the accident area before midnight on 27 September. After midnight the temperature dropped to 10°C-11°C.
The air temperature during the night was 12°C-8°C.

There are no recordings of the speed of the ESTONIA during her voyage from the harbour in Tallinn to the time of the accident. The Commission has made an estimation of how the speed was affected by the waves, inter alia by comparing her speed with the speed of the SILJA EUROPA, another passenger ferry steering a nearly parallel course about eight nautical miles north of the track of the ESTONIA. Other available observations have also been used in the estimations. The speed of the SILJA EUROPA is taken from the DGPS recording which 30 times/minute registers the position, the time, the speed over ground, the course over ground and the heading. The data reveal how the speed was affected by the wind and waves.
The ESTONIA departed from Tallinn 15 minutes late from her normal schedule. The manoeuvre from the port to the Tallinn leading lights is estimated to have taken about 10 minutes. It must be assumed that full service speed, i.e. about 19 knots, was maintained from the Tallinn breakwater to Osmussaar lighthouse, which she passed very close at 2200 hrs. Her estimated speed was still close to 19 knots and she was now a few minutes ahead of normal schedule. Between 2215 and 2245 hrs (approximate) the ESTONIA was plotted by a meeting vessel, the AMBER and according to Amber's plot, the speed was then about 18.5 knots. The speed of the SILJA EUROPA was at this point 18.8 knots and further decreased to 17.6 knots between Russarö lighthouse and the Apollo buoy.
After passing Osmussaar lighthouse the ESTONIA lost her land shelter and the sea conditions deteriorated. Based on experience it is believed that the sea conditions were slightly worse in the area where the SILJA EUROPA was sailing.
At about 2255 hrs the Apollo buoy was abeam and the ESTONIA's speed is estimated to have been close to 17 knots.
The ESTONIA passed the Glotov buoy at about 2355 hrs and, by comparing with the SILJA EUROPA, it can be assumed that her speed was now about 15 knots. This estimate is also confirmed by the trainee second officer, who has stated that the speed was between 14 and 15 knots, as well as by the third engineer who has stated that the speed was 15 knots when he started his watch in the engine control room at midnight.
During the first thirty minutes after midnight the average speed of the SILJA EUROPA dropped by about one knot.
When the ESTONIA reached the waypoint at 59°20´ N, 22°00´ E between 0025 and 0030 hrs, her true course was changed from 262° to 287° and the stabilisers were extended. Her average speed was between 14 and 15 knots.
Table 5.6 gives the speed of the SILJA EUROPA and illustrates how the sea state affected her speed. At 0042 hrs the SILJA EUROPA changed course from 259° to 276°. The change of course and possibly also deteriorating sea conditions resulted in increased motion of the vessel and at 0059 hrs the officer of the watch reduced the speed to 13 knots. The position of the SILJA EUROPA at about 0100 hrs was bearing approximately 350° and distance 10 nautical miles from the ESTONIA.

Table 5.6 The recorded speed of SILJA EUROPA.

Time, hrs	Max [kn]	Min [kn]	Aver [kn]
0030	16.4	14.8	15.4
0035	16.4	15.3	15.9
0040	16.8	15.4	16.1
0045	16.4	14.8	15.6
0050	16.2	14.7	15.6
0051	16.6	14.8	15.8
0052	15.7	14.3	15.2
0053	16.1	14.9	15.6
0054	16.0	14.2	15.0
0055	15.5	13.3	14.6
0056	15.3	13.9	14.4
0057	15.5	13.8	14.6
0058	14.9	11.6	13.9
0058	14.9	11.6	12.9
0059	13.9	11,7	12.7
0100	14.5	12.9	13.4
0105	13.6	11.9	12.9
0110	13.8	12.1	12.9
0115	13.2	10.7	12.3
0120	12.6	10.9	12.4
0125	13.6	9.6	13.3
0130	10.7	9.1	10.7

In the table the Max, Min and Aver columns give the highest, the lowest and the average speeds, respectively, during one minute.