Towline Failure and Snapback
Towline failure during ship assist: snapback zones, wheelhouse protection, the MAIB investigations, and why the risk is treated as normalised.
A towline that parts under tension releases its stored elastic energy along the line of tension, sweeping an arc that can reach the tug’s wheelhouse. It is a distinct failure mode from girting and it injures rather than capsizes.
The MAIB investigation into the failure of a tow rope aboard Svitzer Avon while assisting Auto Eco in the approaches to Royal Portbury Dock on 4 February 2025 was published as an interim report in January 2026 under Regulation 14(2)(b) of the Merchant Shipping (Accident Reporting and Investigation) Regulations 2012, because the full report would not appear within twelve months. The line lashed back, damaged the wheelhouse and injured two crew. The Chief Inspector wrote to the operator expressing concern that towline failure has become normalised and that the associated risks are not being mitigated, referring back to MAIB report 15/2022 into Svitzer Mercurius and its recommendation 2022/138 for a fleetwide risk assessment of towline failure and snapback and the use of laminated glass or other defences. The investigation remains open.
The full article will cover the energy stored in synthetic and steel lines, snapback geometry and zone marking, wheelhouse glazing and screening, inspection regimes, and the recommendations arising from each investigation.