The Deep Draft

Dear readers,  another interesting case study.

A vessel overshot a desired heading, causing it to collide with nine yachts, buoys and ground tackle.

NARRATIVE

A general cargo vessel was proceeding under pilotage along a river. It was dark and the weather was calm with dense fog patches. Visibility was less than 0.5 mile and the tide was flooding at springs. The pilot, the master, and the second mate manned the bridge. A lookout was posted forward. The pilot was using the main radar, while the second mate acted as helmsman and used the second radar. The master acted as lookout on the port side of the bridge. The vessel was manoeuvred to the starboard of the channel to provide distance for a passing vessel. Her course was 210 degrees. After the vessels had passed, the pilot considered he needed to bring the ship back towards the middle of the channel in preparation for taking the deeper water on the port side of the channel. He ordered 20 degrees port helm, with an instruction to steer a course of 180 degrees. The engine was dead slow ahead and the vessel was making good about three knots. The pilot continued to monitor the radar and saw the heading was 165 degrees. He repeated his order for 180 degrees and then, intending to control the anticipated swing to starboard, removed the full starboard helm which had been applied by the second mate. There is conflicting evidence as to whether the pilot returned the rudder to amidships or, in fact, applied port helm. The vessel continued to swing to port and the pilot ordered hard to starboard and slow ahead. The vessel reached a heading of about 140 degrees before she started swinging to starboard. She closed a line of moorings on the east side of the river and collided with nine yachts and damaged buoys and ground tackle.

LESSONS

– An initiating cause of the accident was the fact that the vessel overshot the desired heading of 180 degrees while making a 30 degrees alteration of course. An initial rudder angle of 20 degrees to start the swing was reasonable.

– Although the second mate applied full starboard helm to counter the swing to port, it was done too late to prevent the vessel overshooting. This may have been due, in part, to the lack of a visual reference with which to estimate the rate of swing.