www.ntsb.gov/investigations/Documents/DCA24MM031_PreliminaryReport%203.pdf
The US National Transportation Safety Board (NTSB) released its preliminary report into the Baltimore Bridge incident, when container ship Dali hit the bridge after a loss of power, causing the bridge to collapse.
A primary electrical breaker which feeds most of the vessel’s equipment and lighting had unexpectedly tripped, leading to a blackout (loss of power) onboard.
The electricity was supplying pumps delivering fuel to the main propulsion engine, and so that also shut down, so the vessel’s propeller stopped.
The crew managed to restore electrical power to the vessel, and the emergency generator started.
A second electrical blackout occurred when the vessel was 0.2 miles from the bridge. The emergency generator provided electrical power to the emergency equipment continuously through the second electrical blackout.
When the pilot ordered a hard turn of the rudder, it was ineffective since there was no propulsion to help with the steering.
The crew regained electrical power before the vessel struck the pier but was unable to regain propulsion.
There had also been a loss of electrical power on the vessel during in-port maintenance 10 hours before leaving Baltimore. While working on the diesel engine exhaust scrubber system for the diesel engine driving the only online generator (generator 2), a crewmember mistakenly closed an inline engine exhaust damper. Closure of this damper effectively blocked the engine’s cylinder exhaust gases from traveling up its stack and out of the vessel, causing the engine to stall. When the system detected a loss of power, generator no. 3 automatically started.
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