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Yogi sinking dissected but not proved

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A year after the sinking of M/Y Yogi, a new 198-foot (60m) yacht built by Proteksan-Turquoise in Turkey, French investigators have released the report into what happened.



The report by the Bureau d’enquetes sur les evenements de mer (the French Marine Accident Investigation Office, known as BEAmer), carries this caveat: “The analysis of this incident has not been carried out in order to determine or apportion criminal responsibility nor to assess individual or collective liability. Its sole purpose is to identify relevant safety issues and thereby prevent similar accidents in the future.”


Statements from the owner, the shipyard, the classification society, and the flag state authority (France) indicate that the vessel was technically sound and complied with the requirements of the French administration, the report notes.


Still, it sank.


In the early hours of Feb. 17, 2012, M/Y Yogi sank off Skyros Island in the Aegean Sea while en route from Istanbul to Cannes. Its eight crew were rescued. According to the report, here’s what happened:

On Feb. 15, 2012, Yogi sailed from Tuzla, Turkey, to Istanbul for bunkering. As the vessel was not fitted with a stability analysis software, the master carried out the stability calculations on paper. To lighten the vessel and to keep a level trim, the swimming pool tanks were emptied and the DO tanks were left empty, according to Proteksan Turquoise shipyard instructions.



On Feb. 16, the master’s report indicated weather conditions as follows: wind NNW 5-6 with 35-knot gusts. Swell 2-2.50m.
Météo France reported wind NE 10-15 knots then NNE 25 knots (30- to 35-knot gusts).
Significant wave height between 0.7-1m, sea state slight, then moderate in the western and southwestern part of the basin, reaching 1.3-1.5m after 8 p.m. around Skyros.
About 3 a.m., end of the customs inspection and beginning of bunkering (25,000 liters).
At 6:15 a.m., getting under way bound to Cannes.
At 6:30 p.m., out of Dardanelles straits, pilot dropped.
The autopilot setting was 5 degrees maximum rudder angle.The engines were running at
60 percent of the maximum load.


On Feb. 17, about 1:40 a.m., the chief engineer on watch (Chief M1) observed that the starboard engine exhaust expansion ring was split and leaking. As the phone was out of order, he tried to inform the bridge with the interphone but this was defective as well. Chief M1 went up to the bridge and asked the master to stop the starboard engine (there had been no high temperature alarm).
At this moment, Chief M2, arrived on the bridge. He closed the two starboard engine exhaust hull valves.
At 1:46 a.m., failure confirmation e-mail sent to DPA. The starboard engine was out of
service. Soon after, the port engine exhaust and coolant freshwater temperature were also abnormally high. Chief M1 asked the master to slow down; at the same instant the engine automatically shut down.
Yogi was stopped and making no way. Starboard broadside to the waves, she was rolling and listing to port.
At 2 a.m., the DPA was informed of the second engine failure. The three engineers (the Master Mechanics had also been woken up) undertook the survey of the two seawater suction strainer and of the two engine cooling circuit strainers. The baskets were clean, but it seemed to the engineers that they were frame fit in the chamber without enough clearance and thus the inlet rate of seawater flow was insufficient.
The chambers were put back without the baskets, the seawater cross-pipe was bled and the circuit was placed back in service.
The service pump circuit (which was feeding the generators) had been set on the propeller shaft stuffing box (max. temp. 35°C, normally cooled by the main engine seawater cooling circuit); but soon after the generators’ coolant pressure was insufficient: back to initial set-up.
At 2:20 am, pan-pan alert.
About 2:30 a.m., the port engine was restarted and temperatures were back to normal. Chief M2 came to the bridge. When the master clutched in he observed that there was no answer to the helm: the autopilot was off and the two steering engines were “out of order”. The alarm lamps were on and a 30-degree angle to starboard was displayed on the helm angle repeater. In addition he did not succeed in starting the bow thruster.
The engineers consider to seal the leak on the starboard exhaust with a thermal blanket (back-up generator insulation) and ratchet straps. Chief M1 and the master mechanics went then aft (without handheld VHF) for a first investigation in the steering room, through the companion hatch on the starboard side of beach club 2: about 15cm of water flooded beach club 2. When they opened the hatch, they observed that the steering room was also partially flooded (30-40cm) without any flooding detection alarm actuation. As the companion hatch was opened, the water was running down from beach club 2 to the steering room and the alarm set off.
Chief M1 went back to the engine room and started to pump. The watertight door to access the hi-fog room was then closed by an engineer.
The master mechanics went up to the bridge to report to the master and the first officer. The first officer accompanied by the master mechanics (also without hand-held VHF) went to inspect beach club 1 using the outside starboard staircase; taking advantage of a lurch to port, he opened the watertight door, and observed about 1m of water.
In order to keep off a route broadside-on to the waves, the engine was kept running dead slow, despite the unavailable helm.


Soon after, the first officer and the master mechanics carried on a second investigation in beach club 1, after they had put on their survival suits. It appeared that the height of water was the same.
Due to the tacking, the list shifted to starboard and increased suddenly. Water from the sewage tank flooded the engine room.
At 3:25 a.m., DPA in contact with a company in Athens to charter a salvage tug.
At 3:40 a.m., the hi-fog room located aft of the engine room was flooded. The draining pumps ran dry.
At 3:45 a.m., the Lloyd open form contract was confirmed and the salvage tug went under way.
At 4:28 a.m., mayday issued.
At 4:40 a.m., last SAT C communication between the vessel and the DPA.
About 6 a.m., the crew attempted to reach the liferafts, located on the aft of the sundeck, through the lounge but the two glass windows were blocked closed by the list. The crew did not succeed to break them. The crew found refuge in the superstructure.
At 6:43 a.m., the first helicopter cancelled its mission due to a technical failure.
At 6:47 a.m., last mobile phone communication between the master and the DPA.
At 7:45 a.m., the second helicopter was on task. During the following minutes the stewardess and the rating were winched from the superstructure. Two life rafts were released.
As the weather conditions were deteriorating (snow and hail), winching was considered too dangerous. The six other crew members jumped in the water, one after the other, to be winched up.
At 8:50 a.m., all crew were in the helicopter bound to Skyros.
At 11:04 a.m., the 406 MHz beacon ceased to transmit. Position 38°35.4 N – 025°03.7 E.


Yogi was the third of a three-vessel class built by Proteksan Turquoise shipyard. It was 6.4m longer and differed from the other yachts by a covered sun deck and a hard top. That’s the reason why a 27.9-metric-ton additional keel had been welded to the keel during the build, the report stated. The hull was made of steel and the superstructure of aluminium.



The vessel had two wide access shell doors at the level of the lower deck. The side door on starboard allowed pleasure boat movements from beach club 2. The stern door was used to store two retractable swim ladders. It was accessible from beach club 1. Both doors opened downward and outward.
Fitted with joints, they were watertight and weathertight. The locking was done by eight hydraulic jacks fastened on the hull. When closing, if the male part of the jack was not perfectly fit in the door, the locking was impeded and an alarm went off.


Intact stability had been analyzed. An inclining experiment was done on March 17, 2011, in the presence of the local representative of the classification society, who was also the representative of the flag state authority.
Damage stability was subjected to several propositions, which were linked to the definition of the watertight compartments proposed by the owner and for which the classification society asked the flag state advice. Indeed, at first, compartment beach club 1 and beach club 2 constituted one compartment (no tightness between the 2 compartments). This arrangement was not compliant to the damage stability criteria.


Watertightness between these compartments had been restored by a watertight hinged door. The compartmentation as well as the watertight doors location was subjected to a
new examination after which it had been asked: “Given the type of door fitted between compartment 1 (described as beach club 1) and compartment 2 (described as beach club 2), the damage stability analysis should consider the case when these two compartments are flooded. This door would have to remain closed when the vessel is under way.”


Damage stability had been analyzed. The watertight bulkheads of the vessel should be so arranged that minor hull damage that results in the free flooding of any one compartment will cause the vessel to float at a waterline which, at any point, is not less than 75mm below the weather deck, freeboard deck, or bulkhead deck if not concurrent.

Minor damage should be assumed to occur anywhere in the length of the vessel, but not on a watertight bulkhead.


However, the classification society took into account the flooding of only one beach club and not both.
Two months after the delivery, Yogi had a technical call in June 2011 to sort out a problem on the air conditioning system and to repair damages caused by a leak of refrigerant. Some deficiencies noted on the stern door (technical or aesthetic) had been corrected:
* repair of hydraulic and electric opening/closing circuits damaged by water infiltrations in the swim ladder stainless chest, and
* replacement of the door seal (poorly bonded but tight) by a silicone seal with a more appropriate color.
In addition, a 200-liter, two compartment with submersible pumps tank to collect the dripping from the beach clubs had been installed aft of the steering gear in compartment 03. The installation required the modification of the draining circuit. These important modifications, although they affect an installation located under the freeboard deck, do not appear on plans, and the ABS company and the French administration were not informed. The schematic diagram is not part of the approved drawing package.
On master’s request (who took command in July 2011), double hose clamps had been fitted on the modified draining circuit connections.


Different works were scheduled during the warranty survey done at the shipyard from October 2011 to February 2012. The major works were to recoat the vessel and to take down the stern door in order to refit the swim ladders chests, and it was necessary to punch the two hinges. The electric connections, the hydraulic spools and the fastening had been renewed.
Operations had been monitored by an expert, a naval architect, and tightness tests (passed although the lower part of the stern door had not been tested) had been conducted with fresh water at a pressure of three atmospheres. The tightness had then been checked by the crew during the voyage from Tuzla to Istanbul and from Istanbul to Dardanelles.


However, a projected work list to be done in the frame of the warranty visit shows a specific request linked to the vessel instability (new inclining experiment), problems of submersion of the freeboard marks for some particular loading cases and a request to study an additional VIP cabin.



Loss of stability led to sinking
The foundering of the vessel can be explained only by a fast deterioration of the stability, due to a progressive flooding of the three compartments of the aft zone.
The gas leak in the starboard engine due to the crazing then cracking of the expansion ring had been preceded by no alarm. BEAmer had been informed of a similar failure on M/Y Petara (the rubber expansion ring, which melted at near 600°C temperature, had been replaced by a metallic ring). As the engineers did not have time to make a temporary repair, the starboard engine was not restarted.
The increase of the temperature of the cooling freshwater and of the exhaust in the port engine did not lead to an immediately observable failure of the exhaust expansion ring. The engine shut down automatically, before the master had reduced speed. The engine had been restarted once the cooling seawater circuit had been reset.


The engines were set at 60 percent of maximum load. The sea state and vessel motions did not require to reduce speed. BEAmer does not consider the hypothesis of an air-blocked seawater circuit due to the vessel pitching and rolling.
On the other hand, BEAmer considers the hypothesis of an insufficient cooling seawater flow rate, due to strainer basket frame fit in the chamber without enough clearance as an underlying factor contributing to put the vessel in jeopardy. Proteksan Turquoise objects to this hypothesis. (See the builder’s response to this report on page B13.)
The cooling temperature thresholds had been exceeded, without the telemonitoring device had allowed the officer to anticipate an “auto shutdown” of the port engine and a major failure of the starboard engine. This malfunction is also an underlying factor.


The changes made to the superstructures led to a raise of the center of gravity. The additional keel do not appear on the as-built plans nor on the free-board report transmitted to the administration. Generally speaking, due to the absence of draught marks (to check the trim and the actual gross weight of the vessel), the stability calculations done on board lacked of precision.


Results of the Feb. 17 loading case calculations show figures hardly at the limits of the required criteria. The intact stability of the yacht appeared inadequate to the crew when the vessel was at sea: even when the wind was moderate the list taken by the vessel was noticeable.
When the master wrote the projected work list to be done in the frame of the warranty visit, he requested other inclining experiment in order to check the figures. This request had been rejected by Proteskan Turquoise project manager and suppressed from the final list of works to be done.


This intact stability situation is an underlying factor and points out vulnerability of the
vessel.
The damage stability analysis has been impaired by a CNSNP advice that was not acted upon, which precised that the analysis should take in consideration the case when both beach clubs would be simultaneously flooded.
On the other hand, it is probable that criteria would not have been met if this analysis had considered this requirement. This had been confirmed by the inability of the vessel to right up after the list to starboard had increased.


Considering the presence of 10cm (up to 30cm or more) of water in each of the beach clubs, it appears that the vessel could not right herself.
This small reserve stability had been an aggravating factor of the flooding of contiguous compartments. It had led to the foundering of the vessel when the vessel superstructure
flooding spots (engine room and crew dinning room air inlets) had been submerged, when the list had been reaching about 40 degrees.


In addition, BEAmer notices that “minor breach” notion puts the vessel survival capacity at risk. The definition should comprehend the entirety of a hull division between two watertight bulkheads and not be limited to one compartment.
The side doors located under the level of the free-board deck have to be watertight. The sill of the side doors was under the waterline yet the detailed plans show that the door internal lower sills, protected by a seal, were above the deep waterline (DWL).


However BEAmer observes that International Convention on Load Lines (LL66, 1988 protocol) is not referred in division 242 although it seems particularly relevant in the case of big size side doors opening to watertight compartments.
Although it was not part of the planned warranty work list, the disassembly of the stern door had been difficult. These difficulties resulted in meticulous watertightness control, both in the shipyard and at sea.
To remain undetected, a water leak should have begun only shortly before the engine failure, with an important flow rate. Moreover, when the height of water is higher than several dozens of centimeters, its origin cannot be identified anymore.


A tightness failure of the stern door seal is the first hypothetical factor of the flooding of Yogi.


The officers on watch had never been alerted by the flooding alarm of the steering room. Given the vessel motions and the height of water observed during the investigation, it should have gone off. This malfunction is the second hypothetical factor contributing to the flooding.
The modified draining circuit of the three aft compartments constitutes a “weak link” that could have initiated the spreading of water from one compartment to the two others, through a siphon effect in case of an overflowing of the drips tank, and following the flooding of beach club 1. This malfunction constitutes a third hypothetical factor.


BEAmer observed that the crisis had been managed without unnecessary risk-taking and with cold-blood by the crew, under the master’s authority.


A response issued by Mehmet Karabeyoglu, managing director of Proteksan-Turquoise, available here.

Full report available by clicking here. French and English are in same document.

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