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Day Signal mast broke off and fell to deck

What happened?

On a offshore field support vessel waiting on poor weather and experiencing high winds, the Day Signal mast on the roof of the wheelhouse broke off and part of it weighing 35kg, fell 16m to the main deck.

The weather was deteriorating and Hs (Significant Wave Height) was over 3m. The bridge team had discussed lowering the Day Signal but agreed that the wind and vessel movement could cause an increased and unnecessary risk for working on the roof of the wheelhouse. It was decided to leave the Day Signal in the raised position. The weather continued to deteriorate and the wind increased to 45-50 knots, gusting 60 knots. Later that day, a loud slamming noise was heard on the bridge. Deck lighting revealed that the Day Signal mast had broken off and was lying on the main deck. Owing to the weather situation the decision was made to leave the broken signal mast unsecured on deck until the weather improved. No-one was harmed.

What went right

  • The bridge team took account of the wind and weather conditions and wisely opted not to do a job which would have put people at risk;
  • The on-duty deck officer had closed the back deck – restricting access to outside areas owing to the risk from the weather – and this meant that no-one was around at the time.  

What went wrong/what were the causes

  • The mast was made of lightweight Aluminium in order for it to be light enough to raised and lowered manually;
  • The mast design  was considered sufficient to withstand the forces from high winds;
  • The mast had not been identified as a potential dropped object.

Actions taken

  • Reviewed procedures for closing the back deck during bad weather, to ensure sufficient barriers or warnings are in place when required;
  • Includes Day Signal Mast in Dropped Object survey. Implemented additional securing wiring;
  • Check for similar items onboard, for example, Helideck Windsock Mast, and include in Dropped Object survey if necessary;
  • Review maintenance and inspection regime on Aluminium masts or similar. 

A Day Signal is a requirement of the Collision Convention on the International Regulations for Preventing Collisions at Sea –  COLREGs. It shows that a vessel has “Restricted Manoeuvrability”.

On this vessel, the Day Signal is normally a rigid type, permanently installed and raised/lowered by use of a hinged system and a hand cranked winch.

Members may wish to refer to:

Safety Event

Published: 22 January 2024
Download: IMCA SF 02/24

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