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NTSB: Flooding, sinking and loss of tugboat Mangilao

What happened

The National Transportation Safety Board of the United States (NTSB) has published a report entitled MAB 20-33 into the sinking of a tugboat.  The tugboat, towed by another tugboat, sank in heavy weather in the Pacific whilst on passage from Guam to Subic Bay in the Philippines.  There was no loss of life.

The incident occurred approx. 0440 local time, in worsening sea and weather conditions. The towline to the towed, uncrewed, vessel parted, and the two vessels separated. The towing vessel turned round and found the other vessel taking on water, and it eventually sank. There was no pollution nor were injuries reported.  

What were the causes

Investigation determined that the probable cause of the sinking was the failure of the towing arrangement due to the loss of a towline shackle pin, which left the towed vessel adrift and resulted in the ingress of water from boarding seas in a developing typhoon.

Further detailed information is available from the report at www.ntsb.gov/investigations/AccidentReports/Reports/MAB2033.pdf

Safety Event

Published: 4 January 2021
Download: IMCA SF 02/21

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