NTSB Requires Speed Limits for ASD Tugs in Port Maneuvers

CC Portland underway before the grounding. Source: VesselFinder.com via NTSB
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The National Transportation Safety Board (NTSB) has issued a requirement for owners and operators of azimuthing stern drive (ASD) tugs to set speed limits during certain port maneuvers. This decision comes after two accidents caused by excessive speed. The NTSB’s report on the grounding of the CC Portland in the Corpus Christi Ship Canal last year revealed that the incident was caused by excessive speed during a bow-to-bow harbor relief maneuver. The grounding resulted in $1.3 million in damages, but fortunately, no injuries were reported. ASD tugs are equipped with two azimuth thrusters under the stern and are primarily used for push-pull, harbor assistance, and escort towing operations. The NTSB concluded that the lack of a company policy regarding maximum speed for bow assist maneuvers contributed to the grounding.

In another accident investigated by the NTSB, the tugboat George M and container ship MSC Aquarius collided in the Houston Ship Channel earlier this year. Although there were no injuries, the damage to both ships was over $900,000. The NTSB determined that the collision was caused by the George M’s attempt to approach the container ship at excessive speed. As a result, the NTSB encourages owners and operators of ASD tugs conducting bow-to-bow port support operations to establish speed limits. According to the NTSB investigators, the risk of accidents increases as speed increases during these operations. Increased speed reduces the reserve propulsion power available to the operator, making it harder to regain position if the tug moves out of position. The full report, Marine Survey Report 23-19, is available on the NTSB website.

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