This information is preliminary and subject to change.
Investigative Update Release Date 24 June 2024
The information in this investigative update is preliminary and will be supplemented or corrected during the course of the investigation.
This report provides an update to the NTSB’s preliminary report issued on May 14, 2024, concerning the March 26, 2024, contact of the containership Dali with the Francis Scott Key Bridge in Baltimore, Maryland, and the subsequent collapse of the Key Bridge. Investigative activities have continued since the preliminary report was issued.
NTSB investigators have completed in-person interviews of the vessel’s crew. Onboard examination of engineering systems and testing of electrical systems has been completed. Documentation of the damage to the vessel structure is ongoing.
During the accident voyage, electrical breakers HR1 and LR1 unexpectedly opened when the vessel was three ship lengths from the Key Bridge, causing the first blackout (loss of electrical power) to all shipboard lighting and most equipment. While examining and testing the vessel’s electrical power distribution system and control circuitry, NTSB investigators (in coordination with vessel crew and parties to the investigation) noted an interruption in the control circuit for HR1’s undervoltage release.[1]
Exemplar terminal block identical to model removed from ship. (Source: WAGO)
NTSB investigators subsequently removed an electrical component (a terminal block; see figure) from the control circuit for HR1’s undervoltage release.[2] Two portions of control wiring associated with the terminal block were also removed. We continue to examine the removed components at the NTSB Materials Laboratory. We will continue to evaluate the design and operation of the vessel’s electrical power distribution system, and investigate all aspects of the accident to determine the probable cause and identify potential safety recommendations.
[1] An
undervoltage release is a device that opens a breaker when voltage falls below predetermined thresholds.
[2] A
terminal block is an insulated block that connects two or more wires together.
Preliminary Report Release Date: 14 May 2024
On March 26, 2024, about 0129 eastern daylight time, the 947-foot-long Singapore-flagged cargo vessel (containership) Dali was transiting out of Baltimore Harbor in Baltimore, Maryland, when it experienced a loss of electrical power and propulsion and struck the southern pier supporting the central truss spans of the Francis Scott Key Bridge (Key Bridge). A portion of the bridge subsequently collapsed into the river, and portions of the deck and the truss spans collapsed onto the vessel’s forward deck. A seven-person road maintenance crew employed by Brawner Builders—which was contracted by the Maryland Transportation Authority (MDTA)—and one inspector employed by Eborn Enterprises, Inc., a subconsultant to the MDTA, were on the bridge when the vessel struck it. The inspector escaped unharmed, and one of the construction crewmembers survived with serious injuries. The bodies of the six fatally injured construction crewmembers have been recovered. One of the 23 persons aboard the Dali was injured.
The US Coast Guard classified this accident as a major marine casualty. NTSB is leading the safety investigation.
Read the
Preliminary Report.
View on scene photos from
NTSB Flickr.
