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Control module failure caused main engine sudden reduction to idle speed

What happened?

An offshore support vessel (OSV) was underway to field loaded with cargo when a sudden drop of starboard main engine RPM was observed. The main engine dialog screen gave the error message <invalid throttle signals>. The engineers informed the bridge immediately. Investigation began; the onshore office and the client were also informed. With the client, it was decided to take the vessel back into port as a quick fix was not available.

What went wrong? What were the causes?

  • The remote speed controller module had failed;
  • The cause was overheating for a prolonged period;
  • The root cause was assumed to be extremely unfavourable conditions (hot and humid) in the engine room, leading to unexpected and unpredictable failures of electronic components because of high temperatures.


  • Crew should remain aware of and alert to the likelihood of unexpected equipment failure under extreme conditions of heat;
  • Sufficient spares of potentially vulnerable electronic items should be carried and stored appropriately.

Our member started a fleet-wide study of the effects of high engine room temperatures on electronic control equipment.

Safety Event

Published: 17 September 2018
Download: IMCA SF 21/18

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