On cargo ships, the engine spins the ship’s propeller, thrusting it forward or backward, while separate generators produce electricity for the vessel. The engine relies on electricity for pumps that inject fuel and circulate oil and water to keep components lubricated and cool.

Myriad causes could lead a ship to lose power or propulsion, or to experience a complete blackout, typically coming down to failures of either the ship’s co-dependent electrical and mechanical systems, experts said. The Coast Guard reports reviewed by The Sun cited equipment malfunctions and human mishaps as causes for the ships losing propulsion.

Routine vessel vibrations jarred parts loose. A second engineer on a ship that didn’t have an alarm system for the main engine’s air compressor didn’t realize it was on manual, rather than automatic mode, leading to low pressure that caused the engine to shut down. A defective sensor led to a lack of cooling oil for another vessel’s engine.

When a ship’s automated engine monitoring system recognizes a problem, it cuts the motor off to avoid costly damage, Mercogliano said.

“They’re designed to protect themselves,” he said.

The 691-foot Grande Cameroon, of Italy, was on its way to Baltimore when it experienced a complete blackout in the Chesapeake Bay, just south of Tilghman Island. According to the Coast Guard, the ship lacked proper sensing equipment to recognize temperature changes in a steam line connected to one of its fuel tanks.

“A blackout requires more time to reset compared to just a loss of propulsion,” said Mark Phillip Laurilla, a chief marine engineer based in the Philippines, in an email. “Loss of propulsion doesn’t happen all the time but it happens often enough that some companies send their officers to simulator training particularly for this type of scenario.”

Students at Cal Maritime run through scenarios in simulator-based classes.

“We’ll run a scenario where we’ll throw all sorts of situations at them, total loss of steering, total loss of propulsion … so our students really get familiar with those emergency procedures, and they become second nature,” Calnan said.

In November 2021, a 981-foot, Liberian-flagged container ship lost propulsion in the Patapsco River, after going under the Key Bridge en route to Seagirt Marine Terminal. Tugboats guided it back out and down the bay to the Annapolis Anchorage for repairs. The Coast Guard report said the crew aboard the Agios Dimitrios failed to calibrate a component of the main engine.

Video of the Key Bridge collapse showed the lights aboard the Dali go out and then flicker as it approached the 1.6-mile span. A local pilot, who was on board to guide the ship out of the harbor safely, reported losing all power, including the ability to steer, in a “mayday” call shortly before striking the bridge.

Experts who watched the footage have postulated multiple possibilities, from electrical failures to contaminated fuel to human error.

“What happened to the Dali was not one generator failing, but an entire system,” Laurilla said. “It is highly unlikely that all of their generators were in poor condition. So something common to all of them caused the problem and forced them to shut down. The only common denominators would be fuel or switchboard problems.”

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(Baltimore Sun reporter Annie Jennemann and editor Christopher Dinsmore contributed to this article.)

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