The NTSB has launched its preliminary factfinding report on the allision of the boxship Dali with the Francis Scott Key Bridge. While the company has not drawn any conclusions but about causal elements, the summary accommodates beforehand unreleased details about the 2 temporary losses {of electrical} energy and the lack of propulsion that preceded the accident. 

First, NTSB confirmed early studies that Dali had misplaced energy twice on the pier on the day earlier than she sailed. On March 25, Dali skilled a blackout throughout in-port upkeep as a result of human error. A crewmember by chance closed an engine exhaust damper for the No. 2 generator, inflicting it to stall. The No. 2 was the one generator working (out of the 4 aboard), so the ship skilled a short blackout till the crew might deliver energy again on-line with the No. 3 generator. After a brief interval, the No. 3 generator skilled lack of gas strain and its breaker opened, prompting a second blackout alongside the pier. 

During this incident, the crew converted from utilizing the No. 2 transformer to the No. 1 transformer (and, importantly, the No. 1 transformer’s breakers). Either transformer might be used to show the 6,000-volt energy provide from the mills into “low voltage” 440-volt energy for the ship’s programs, and the No. 2 had been in use for months. 

Simplified diagram of Dali’s high-voltage and low-voltage electrical busses (NTSB)

When the ship departed the pier early the following morning, the No. 3 and No. 4 mills have been working, and the No. 1 transformer, No. 1 excessive voltage breaker and No. 1 low voltage breaker have been in use. Most of the tools that had precipitated issues on the pier the day earlier than (save for the No. 3 generator) was offline.

The ship left the pier at 0036, launched her docking tugs, made her flip and headed outbound in Fort McHenry Channel at a gradual bell. An apprentice pilot had the conn with an skilled pilot watching. At about 0125, as Dali was about three ship lengths away from the Francis Scott Key Bridge, the No. 1 excessive and low voltage breakers each opened and lower off all energy to the remainder of the ship. The causes are unknown and are beneath investigation, with assist from the producer. 

The two auxiliary engines stored working, uninterrupted, however they have been not related to the remainder of the ship’s programs. Without energy to the electrically-driven lube oil pump and coolant pump for the primary engine, the propulsion system routinely shut down. It was by no means introduced again on-line. 

Rudder management was additionally briefly misplaced, and the rudder was caught amidships because the Dali drifted in the direction of the bridge. The emergency generator began up shortly after and restored energy to bridge programs and to at least one steering pump for rudder management. At 0126:13, the senior pilot ordered 20 levels port rudder. This had a lowered impact on the ship’s trajectory, because the propeller was not pushing water previous the rudder.

The crew manually reconnected the excessive voltage and low voltage breakers, restoring full energy to the vessel. At 0126:39, the pilots referred to as for an pressing tug help and ordered an anchor dropped. 

Shortly after, the ship misplaced electrical energy once more. This time, the diesel generator breakers for the No. 3 and 4 mills had opened, chopping off the still-running auxiliaries from the excessive voltage bus. The emergency generator stayed on and stored offering backup energy to the bridge. The No. 2 generator was working on standby and rapidly related routinely, and the crew closed the breakers for the No. 2 transformer (the one beforehand in use the day earlier than) to deliver again low-voltage energy for the second time. From the beginning of the second blackout to the restoration of energy took about 30 seconds. 

Overview of the accident timeline (NTSB)

At 01:29:10, Dali struck the southwest pier of the Key Bridge’s important span at 6.5 knots, dropping the complete six-span truss into the water. One crewmember sustained a minor damage when the bridge deck hit Dali’s bow, six street crew staff have been killed and one employee was injured. Salvage operations to refloat the Dali are ongoing, and litigation over duty for the catastrophe is simply starting.