The German Federal Bureau of Maritime Casualty Investigation released its report on the collision between the Dutch coastal motor vessel Scheldebank with the canal ferry operating in the area of the Hochdonn ferry crossing.
Events from the perspective of the Scheldebank
he Scheldebank left the NOK’s Südschleuse lock in Brunsbüttel at about 0645 on 8 May 2020. She was bound for Kiel-Holtenau. The master, the chief mate and the pilot were on the bridge. The master steered the vessel in accordance with information on the gyrocompass and course recommendations of the pilot. Visibility deteriorated as the canal passage began and in the end only stood at 50-100 m. Accordingly, the 90 m long ship’s fore section was barely visible from the bridge.
The voyage passed uneventfully up until canal kilometre6 17.5. The vessel sailed slightly south of the axis of the canal. The chief mate and the pilot kept a lookout. In the all-stations call by VTS NOK at 0745, shipping on the canal was advised, inter alia, that a Traffic Group (TG) 3 vessel (the Scheldebank was being referred to) had passed the Kudensee siding area8 at 0720. The all-stations call indicated that no oncoming traffic (i.e. coming from the east) was expected for the Scheldebank up until canal kilometre 27.
The all-stations call also revealed that due to diving works a pontoon was situated on the northern side of the canal just east of the Hochdonn High Bridge (located at canal kilometre 19), which had to be passed with particular care.
At about 0750, the Scheldebank approached the high bridge sailing very slightly south of the axis of the canal at canal speed, i.e. the stipulated maximum speed of 15 km/h (8.1 kts). From canal kilometre 18, i.e. about 800 m before the bridge, the vessel reduced speed and passed under the bridge at a speed over ground of about 13 km/h. At the same time, the pilot recommended that they steer a little further towards the southern bank of the canal. The aforementioned measures were taken in order to safely pass the pontoon they had been notified of with sufficient clearance.
On the bridge of the Scheldebank they observed the Hochdonn in operation by radar and ECDIS9, as they were approaching the ferry crossing with the same name located east of the high bridge. The ferry crossed the canal from south to north at about 0750. On the northern bank, the ferry’s radar echo merged with that of the terminal ashore. Since the massive high bridge obstructed the radar view of the ferry’s crossing area, the Scheldebank’s pilot also paid attention to the HOCHDONN’s AIS10 signal when observing the course of her voyage by means of the PPU11 and ECDIS.
Shortly after the Scheldebank’s superstructure had passed the bridge at about 0755, the pilot rechecked the position of the ferry. Her radar echo was still merged with that of the canal’s northern bank. The Hochdonn’s AIS signal also continued to give the impression that she was still stationary at the northern terminal.
Nevertheless, only a few seconds later and with visibility remaining poor at some 75 m, an obstacle directly in front of the bow of the Scheldeban became dimly discernible on her bridge, which – as became clear shortly afterwards – was the Hochdonn. The immediately executed stop manoeuvre could no longer prevent contact with the ferry.
Events from the perspective of the Hochdonn
By his own account, the ferry pilot, who was alone at the ferry’s control position in accordance with regular ferry service procedures, reportedly used the radar and AIS to ensure that there were no vessels approaching the ferry crossing within a distance of about 800 m prior to departure. However, with regard to the reliability of the on-board AIS device, he emphasised to the investigation team that it was highly susceptible to interference.
Due to the extremely dense fog, the ferry pilot was initially unable to see the opposite ferry terminal (distance of about 120 m) or even the fog light, which was installed and switched on there. He therefore used an ‘electronic navigational chart’ on his privately owned tablet to navigate to the ferry terminal. However, the functionality of the tablet was restricted to a less detailed display of the relevant section of the canal and the GPS position of the Hochdonn.
Due to the extremely difficult visibility conditions, the ferry sailed to the middle of the canal at reduced speed and only resumed normal speed when the aforementioned fog light was visible at the ferry terminal.
Shortly afterwards, i.e. presumably after little more than 1.5 minutes of sailing time, the ferry pilot saw a ship ‘behind the ferry’ which he believed was approaching the ferry at an extremely high speed. A suction effect then reportedly occurred and in the period that ensued the Hochdonn was reportedly drawn towards the stern of the vessel, which the ferry pilot was unable to identify as the Scheldebank due to the rapid sequence of events. This caused the funnel on the ferry’s starboard side to buckle and the superstructure there to be deformed. Seconds later, the Scheldebank had already disappeared from the ferry pilot’s field of vision. He then managed to stabilise the ferry’s course and manoeuvre her safely to the ferry terminal.
By carefully analysing all available sources, the BSU was able to clarify the course of the accident and its attendant circumstances largely as follows.
Extremely poor visibility conditions of no more than 75 m prevailed at the scene when the accident happened. The Scheldebank approached the railway bridge in front of the Hochdonn ferry terminal at slightly less than the maximum permitted speed. In the period that followed, the ship reduced her speed moderately and at the same time altered her course slightly to the southern half of the canal in response to a pontoon moored on the northern bank of the canal and diving works being carried out from it.
The Hochdonn cast off from the northern ferry terminal just as the ship was about to pass the railway bridge some 300 m from the subsequent scene of the accident. Although it is reasonable to assume that (even during the temporary and inevitable overlapping of her radar echo with the very distinctive echo of the high bridge) vessels of the size of the Scheldebank can be located from the control position of the Hochdonn with proper use and configuration of the radar, the merging of the echoes in question and/or an unfavourable radar configuration evidently resulted in the ferry pilot failing to identify the approach of the Scheldebank on the radar when he decided to begin the crossing.68 The ferry pilot did not have a properly configured, functioning and user-friendly AIS device at his disposal as a supplementary navigational aid.
Despite an orientation aid there in the form of a fog light, which was switched on at the time of the accident, the ferry pilot on the Hochdonn was only able to make out the southern terminal visually when the ferry had reached the middle of the canal. Therefore, he initially sailed at reduced speed and concentrated intensely on identifying and heading for his destination with the help of a tablet computer with a navigational chart and his own GPS position displayed on it.
The ferry’s reduced speed meant that she had not moved far enough towards the southern bank of the canal when the Scheldebank crossed the area of the ferry
line. This in conjunction with the already discussed fact that the Scheldebank was intentionally steered towards the southern edge of the channel ultimately resulted in the vessels colliding there.
On the merits of the case, the development of the risk of collision was objectively neither foreseeable nor avoidable for the pilot and ship’s command of the
Scheldeban. In particular, in the knowledge of and relying on the fact that NOK ferries must keep a safe minimum distance when crossing the canal, the ship had no reason to reduce her speed as a precaution when approaching the ferry crossing.
Moreover, there were no specific indications on the bridge of the Scheldebank that the forthcoming passage of the ferry line could pose a hazard. Until she had passed completely under the high bridge, the radar equipment on her bridge was not able to identify the Hochdonn’s echo moving away from the echo of the ferry terminal during the period in question due to the high bridge’s radar shadow. By the time the radar view was clear, the Scheldebank and the ferry had already converged to such an extent that the latter could no longer be differentiated in the radar antenna’s visual beam. Moreover, it was proven that the Hochdonn’s faulty AIS signal gave the false impression on the bridge of the Scheldebank that the ferry was still at the northern terminal up until the very last.
#1 Ergonomics, visibility conditions, as well as ambient temperature and air quality on NOK ferries
According to information from WSA NOK, the ferries Hochdonn, Audorf and Nobiskrug, which were built in the 1950s and do not meet modern standards in terms of bridge ergonomics, visibility, as well as ambient temperature and air quality, are to be replaced in the near future by new-builds that are already undergoing trials. Accordingly, the BSU sees no reason to make the difficult working conditions at the control position of the ferries in question the subject of safety recommendations, even though they may undoubtedly interfere with the safe operation of these vessels.
#2 AIS on NOK ferries
According to information from the WSA NOK, all the ferries currently operated on the NOK and owned by the federal government have comparable or largely identical navigation equipment. This is characterised by the fact that the ferry pilot has a radar set as a central aid for traffic monitoring at his disposal. An AIS device with separate display screen is also installed at the control positions. The bridge equipment does not include an electronic navigational chart.
#3 Electronic navigational chart on NOK ferries
Approaching the ferry terminal in extremely poor visibility conditions requires a high level of concentration on the part of the ferry pilot. Given the rapid succession of the manoeuvres in question, this can impair the ability to concentrate and also lead to the ferry pilot inevitably devoting the main focus of his activity to reaching the opposite ferry terminal unerringly shortly after casting off.
#4 Lookout on NOK ferries
In the opinion of the BSU, the fact that the ferry pilot on a NOK ferry is solely responsible for the lookout, irrespective of visibility and/or other special circumstances, and in this respect cannot (at least formally) fall back on the support of the deckhand, represents a safety risk and therefore requires an organisational correction on the part of the ferry operator.
#5 Suspension of the NOK ferry service in fog
The contractual and internal requirements for the ferry service do not take into account the requirement contained in Section 12(2) FäV that the ferry service be suspended if the crossing involves any kind of risk.