Mechanical linkages can lead to accidents when not checked

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The incident

A passenger ship with 37 people on board was heading close to a pier. The captain commanded astern movement on main propulsion engines while the vessel’s speed was 4.5kts ahead. The passenger vessel did not respond to the engine movements and continued navigating ahead. As a result of not following the engines, the vessel bounced off the pier many times. Although the master decided to make the engines stop, the vessel had already grounded. All 37 passengers were safe and with the help of a diving boat were disembarked. Also, the diving boat pulled the vessel back to the land. Moreover, after pulling the ship to the landing stage, the damage to the vessel and the pier was minor.

Probable cause

The local engineering after checking the vessel discovered that the linkage between the starboard engine gearbox and the gear shift mechanism had disconnected. That is why the crew were unable to change the direction of the passage vessel. Since the port engine was reversed, it applied reversed thrust. On the contrary, the starboard engine continued to apply ahead thrust.

Those factors caused the ship to swing to port and make contact with the pier. The console with the remote controls for the engines did not have any indications for propeller direction so the master was unable to understand why the vessel was not responding as he had expected.

Gear shift mechanism linkage (inset: linkage disconnected in service)

Lessons Learned

  • Mechanical linkages are likely to detach or fail, especially when used on repeat. Check and tighten them as required. Where possible, use self-locking nuts and split pins to prevent such incidents.
  • Simple instruments or gauges in the wheelhouse showing the running direction and speed of rotation of the propellers can provide immediate feedback to the person manoeuvring the vessel.
  • If you have twin screw propulsion, include the loss of one engine in your risk assessment and consider how you may be able to recover from such a situation in an emergency

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