Vulnerability of tugs underlined following loss of life in Scotland
The death of two crew members after the capsizing of Biter while assisting passenger vessel Hebridean Princess once again demonstrates the inherent dangers associated with small tugs.
Working on a tug is one of the maritime industry’s most dangerous jobs. Tug crews are required to spend much of the working day under the bow of enormous vessels, out of sight of their bridge crews and, sometimes, pinned between the vessel and lock gates or quaysides.
During a tow, flawless communication is required to keep the vessel’s much larger engine and thrusters at bay and prevent the tug from becoming the towed. In one such incident, Biter, a Scottish harbour tug, girded and capsized after being pulled in the wrong direction, while crew on Hebridean Princess watched in horror from the deck of their vessel.
On the morning of 24 February 2023, Hebridean Princess, a 72 metre cruise ship, left James Watt Dock for engine and equipment tests after maintenance at Greenock shipyard, Scotland. Later returning to the dock just after 14:00, a harbour pilot boarded the vessel, and two tugs, Bruiser and Biter, were dispatched to conduct the towage operation.
With Bruiser afore and Biter aft, heaving lines were passed to the tugs by the crew of Hebridean Princess, and secured to each vessel. Over VHF (very high frequency), Biter, the pilot and Bruiser co-ordinated a 3-4 knot tow. Biter would maintain a position aft and starboard of the vessel, with Bruiser dead ahead.
As Hebridean Princess drew parallel with Victoria Harbour, the tug crews began to prepare for the most complex part of their manoeuvre. The vessel was to turn in place and proceed astern toward its berth in the James Watt Dock.
At 15:26, Bruiser’s lines were fully secured. Over VHF, the instruction was given for Bruiser to drop back from Hebridean Princess’ starboard quarter to a position full astern of the vessel. “Do you want me swinging off pilot and go dead astern?” asked Biter’s master. “Yeah, dead astern minimum please,” responded the pilot.
Halfway through the manoeuvre which would end with Biter’s bow pointing aft of Hebridean Princess, the tug stalled.
It was over in seconds. Just as Biter reached a position perpendicular to Hebridean Princess’ stern, at 15:26:58, the towing line went taut. The tug began to ‘girt’, meaning that the line was pulling the vessel over into a list. The tug’s centre of gravity had been overcome by the vast momentum of Hebridean Princess, and at 15:27:08, the tug had completely capsized, trapping its crew beneath.
Failure of the gob rope
Hebridean Princess was moving at a speed over 5 knots, imposing a load on the small tug’s tow lines that it was not designed to deal with. But even then, the problem ought to have been averted. To prevent girting, Biter was equipped with a gob rope, fastened perpendicular to the tow line.
In the event of a sudden lateral heave, the gob rope would slip aftward, bringing the vessel’s towing point aftward, and meaning that the tug’s bow would swing to the side rather than be pulled over.
But this did not work. With a gob rope arrangement which did not pull the towing point particularly far aft of the towing hook, there was far less time for the crew to react when the tow line went taut.
“While it was not possible to determine exactly why Biter’s gob rope failed, the practice of securing Biter’s gob rope to a samson post, when combined with the low friction coefficient of the HMPE rope, might therefore have allowed the gob rope to render more easily than an alternative securing arrangement,” MAIB’s subsequent report determined, noting that a 2.5m stretch of the polyethylene rope had melted and fused, commensurate with the sudden friction of being pulled taught around the samson post.
The accommodation hatch was left open during operation to allow the master to talk to a crewmate on deck over the noise of the engine. Though Biter’s accommodation hatch comprised a not-especially-sturdy wooden door, had this been closed, it might have formed a pocket of air inside the tug’s bridge giving its crew a better chance to escape.
“It is therefore highly unlikely that air would have been trapped in the wheelhouse when the vessel inverted, which might have limited the crew’s chance of survival,” MAIB determined.
Better training needed
Given that the gob rope had not been tested in the configuration as on Biter, MAIB recommended for parties involved to pursue a higher standard of crew training, and guidance on best practices relating to harbour towage.
“Pilots and tug crews must be suitably trained and experienced for their roles, and they must share a detailed understanding of the towage plan before they start the job,” commented Andrew Moll OBE, Chief Inspector of Marine Accidents.
Further he added: “Tug Biter’s accident was another cruel lesson of how rapidly things can go dreadfully wrong. In less than 10 seconds the tug capsized, and two experienced seafarers lost their lives, because of a breakdown of the systems that should have kept them safe.
“Small conventional tugs remain an essential part of UK port operations. However, the vulnerabilities of these vessels must be understood by those that operate and control them.”
Image: Tug Biter before the accident; credit: Alamy.
