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
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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