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NTSB: Loose Electrical Wire Led to Dali Hitting Francis Scott Key Bridge

Dali
Courtesy USACE

Published Nov 18, 2025 2:45 PM by The Maritime Executive

 

[Breaking] A simple oversight in labeling an electrical wire was a causal factor behind the blackout aboard the boxship Dali, resulting in the vessel's allision with a bridge pier and the destruction of the Francis Scott Key Bridge, according to the National Transportation Safety Board. 

The Dali's main switchboard was constructed with commonplace spring-grip terminals for each wire connection. To make a connection, the spring is pushed back with a tool, the bare tip of the wire is inserted down into the terminal block, and the spring is released, forcing the wire against a contact - where it should stay for the rest of the life of the ship. 

Aboard the Dali, each individual wire had a cylindrical label with the wire number on it for easy tracing and troubleshooting. The label was supposed to be placed above the bare tip of the wire, up on the insulation. Instead, someone clamped at least some of the labels too far down towards the tip of the wire. 

On wire 381 of terminal block 1, the label's incorrect position and its larger diameter prevented the bare tip of the wire from being inserted all the way down into the terminal block, the NTSB alleged. The safety agency determined that the plastic label hit the top of the terminal block and stopped the wire from going in any further. Because of this, the wire's tip was barely held by the clamp at the time of assembly. It then rattled free of the clamp at some point in service, and thereafter it made a poor connection with the contact, according to NTSB's investigators. 

In the early hours of March 26, 2024, the loose wire ceased making contact with the terminal, causing a fault that shut down the Dali's auxiliary power, NTSB found. In a cascade of events, this cut out the vessel's propulsion and steering, leaving Dali helpless and adrift. Without tug assist, and unable to restart, Dali drifted into a pier supporting the Francis Scott Key Bridge and destroyed it, collapsing the structure and killing six people.