Baltimore's Francis Scott Key Bridge Collapses after Ship Strike

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  • #106
Baluncore said:
and the port anchor dropped
Do we know when this happened?

At 8 knots, an anchor will not stop the ship. It might - slightly - help turn it. But this is a "Hail Mary", as it were. At this point, the bridge knew they were in deep trouble.
 
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  • #107
Vanadium 50 said:
Do we know when this happened?
According to the ABCNews link in my post #103:
1:27:04 a.m. -- The pilot aboard the Dali orders the vessel's port anchor be dropped, according to the VDR.
 
  • #108
russ_watters said:
et al; I don't understand the anti-NTSB flak/jokes here. The NTSB is maybe the best forensic engineering organization in the world. There's nobody else you would want to be investigating this, at least in terms of the crash itself (I think the 9/11 structural sims were done by NIST).

Do you think the people available for easily accessible media photos are the most critical? How many seats for the media are there on the helicopter? The RHIB? Other side of the coin: if your department has a bunch of newbies, and you have a major project, do you make them stay in the office or have them shadow you in the field?

BTW, COVID was a black hole and my company re-branded twice in the past 6 years, so I have two gleaming-white hard hats in addition to a beat-up one that I don't wear anymore unless both of the others migrate to my garage.
No shade thrown.

I have a clean hard hat for pictures, and a real one for work (fits better, tighter to head, and is less likely to fall off). My past life involved a great deal of these folks that would show up for pictures, and then left when the real work showed, usually after a fire, train derailment, or other issue (some dealing with pyrophoric materials or materials that would ignite with minor friction/impacts, contact toxins, and at least one chemical weapon precursor). Most of these incidents were unpleasant and we had to report to the "face people", even when they couldn't understand the work being done, why it was being done that way and what we had to do to mitigate issues. Very, very few had any kind of STEM/engineering/chemistry training.

I obviously don't know this bunch's job requirements or exactly what they do (and this isn't really a chemical incident). My comments were probably unhelpful and unwarranted.

I agree that there will be a great deal of work to do and they may be the best to do so, and report as accurately as we can expect.
 
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  • #109
So, if I read the timeline right, there was 5 minutes between the order to lower the anchor and the collision. That is not a lot of time. A US Navy vessel would have someone assigned at the anchor ready to go, but cargo ships have much smaller crews. They may have had to stop what they were doing to go there.

In 5 minutes the Dali would have traveled about a kilometer.
 
  • #110
berkeman said:
I've seen in a couple places that the Vessel Data Recorder (VDR) seemed to shut down during each of the power loss windows. That seems really strange to me that the VDR and all sensors are not battery backed up to enable recording during a ship power outage. Does anybody have any knowledge about VDR systems on ships?

Not exactly an expert on VDR systems but decent with internet.
The VDR is a JCY-1900 module (seen in this NTSB video at 7:07 )
Quote from manufacturer's brochure:
There is also an internal UPS included as standard, which is able
to power the VDR for 2 hours in case of power failure. During
blackout only bridge audio is recorded and will automatically return
to normal condition after power is restored.
The systems diagram from the manufacturer's brochure is attached to see what could have been connected to the device. Sounds like a nice job to dissect the data, if it wasn't for everyone breathing down your neck...

Anyways all that is definitely captured in case of an outage is this microphone data. Maybe this will change in the future with different legislation, but who knows...
SumatraPDF_L8hAVkcbt1.png
 
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  • #112
russ_watters said:
et al; I don't understand the anti-NTSB flak/jokes here.
Investigators and inspectors all aways fair game. I don't think there's any doubt how useful these guys are. Of course, the 'Brass Hats' always turn up for major events so the clean hats may demonstrate that in this case.
 
  • #115
berkeman said:
Sorry if this info is in the videos that I haven't watched, but the cause of the accident was loss of main engine power, right? And has there been any indication what could have caused that? Is it an unusual failure? (I would guess so, but I don't know). Thanks
There was a post on the internet shortly after the accident by a former containership captain who said that he always had a drill for loss of engine or electrical power when leaving port. Such occurrences IIRC are not rare. He also said the first thing he does on loss of engine power is drop anchor. The captain of the DALI did not immediately drop anchor but instead called for tug support first which might have taken as much as a half hour to get to them. The call to drop the port anchor was about two minutes after the problems started. DALI has a bow thruster ( as seen by the decal on the bow) but it probably is run by an electric motor but was probably not available.

One other thing, the ship was traveling down the channel(rudder amidship) when the power was lost so I do not think the ship should have turned too much based on that. Dropping the port anchor should not have caused it to veer toward the support. However, the ship makes a relatively sharp turn toward the bridge support prior to inpact.
 
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  • #116
Bow thruster?

Skipper might as well have gotten the crew on deck and told them to blow real hard.
 
  • #117
Vanadium 50 said:
Bow thruster?

Skipper might as well have gotten the crew on deck and told them to blow real hard.
Shades of Bridges at Toko-Ri.
 
  • #119
gleem said:
One other thing, the ship was traveling down the channel(rudder amidship) when the power was lost so I do not think the ship should have turned too much based on that. Dropping the port anchor should not have caused it to veer toward the support. However, the ship makes a relatively sharp turn toward the bridge support prior to inpact.
I heard on one video that the black smoke, ostensibly from the main engine restart was blowing/flowing laterally indicating a breeze from the port side, which would have pushed the DALI to starboard. I heard a conflicting comment that there was no breeze that evening.

In another video, someone mentioned a channel to the starboard side of the DALI, from which a current may have pushed the stern to port reorienting the ship toward starboard. The Curtis Bay Channel comes from the west to join the Fort McHenry Channel, which goes from NW to SE and is centered on the main span of the Francis Scott Key Bridge. Ostensibly, a current flow east in the Curtis Bay Channel may push the stern of the ship and be enough to turn the ship if it has no rudder control (rudder is stuck amidship).

https://fishing-app.gpsnauticalchar...ORE+HARBOR+boating+app#14.23/39.2192/-76.5270

I also heard some discussion with engineers that the bridge had less protection than others. So, the lesson here is that the bridge piers needed much better protection.

https://www.reuters.com/world/us/ba...need-protect-critical-foundations-2024-03-28/

As for the ship, the lesson learned here is that such ships need to have independent systems to ensure navigation/steering/rudder control in the event that the main power plant (or whatever systems provides power to the navigation/steering system) shuts down.
 

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  • #120
Astronuc said:
I heard on one video that the black smoke, ostensibly from the main engine restart was blowing/flowing laterally indicating a breeze from the port side, which would have pushed the DALI to starboard. I heard a conflicting comment that there was no breeze that evening.
There is a lot of ship underwater to resist such a motion and it would take a substantial wind to move the ship a significant amount in 4 min. Also typically a night the wind is usually light, especially in a harbor.

About current I doubt there is a significant cross-current in the channel since in a narrow harbor the tides would be basically flowing out of the harbor. The current in the channel would be lower than that near shore due to depth. The video I saw showed the ship distinctly turning not drifting toward the bridge. I don't think a difference in the speed of the current would significantly change in the length of the ship unless it was a huge CW vortex near the bridge but such a vortex would have moved the bow to port first before causing it to turn to starboard.

If the black smoke was of the engine going in full astern then that would have caused the ship to turn to starboard toward the bridge support. If the ship had it GPS nav equipment running we have a record of the track of the vessel. We'll eventually find out.

Another question I have is do they have a battery backup for certain equipment like nav or deck lights that you don't want to go out.
 
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  • #121
I'm not sure what good having a backed up navigation does if you don't have the ability to steer. ("Where am I?" "You're in a boat!") Radio, however, is battery-powered. I believe that's an actual requirement, not just a good idea.
 
  • #122
Ships rudders are usually controlled by hydraulics. The hydraulic pumps are usually electrically powered. Short rudder deflections will be used to maintain, or to change course. The problem with loss of rudder control is that you do not know you have lost it until you need it.

The hydraulic actuators employed for rudder control are fitted with pilot operated check valves. Fluid pressure, applied to one side of the actuator, also opens the return check valve on the other side. When hydraulic pressure is not being applied to move the rudder, those valves hydraulically lock the rudder in position against the sea.

If electrical power is lost, or a one-sided hydraulic failure occurs, then the rudder may well be left, locked in an offset position, until an engineer can reach the rudder-control machinery space, and take over manual control.

A one-sided hydraulic failure may initially make turning one way possible, but returning to straight ahead may then be found to be impossible.

Loss of rudder control most easily explains the curved collision course.
 
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  • #124
gleem said:
There is a lot of ship underwater to resist such a motion and it would take a substantial wind to move the ship a significant amount in 4 min. Also typically a night the wind is usually light, especially in a harbor.
The ebbing tidal water from that channel to the west would have far more effect than the light breeze and, in the video, it says that the direction would tie in with the ship turning. (Although it was not far from slack water at the time.)
 
  • #125
Baluncore said:
When hydraulic pressure is not being applied to move the rudder, those valves hydraulically lock the rudder in position against the sea.
The ship was on a constant heading down the channel (or should have) when the power went out. If the rudder was locked then it should have continued undeviated down the channel. It did not.

It was less than one hour before slack water on that date. The high water mark was only 1.09 feet and only inches from the low water mark, so the current is negligible.

Vanadium 50 said:
I'm not sure what good having a backed up navigation does if you don't have the ability to steer.
The equipment records the track of the ship so it might provide some useful information. I also would assume they would have lost their AIS and with no lights they would be a hazard to shipping.
 
  • #126
gleem said:
The ship was on a constant heading down the channel (or should have) when the power went out. If the rudder was locked then it should have continued undeviated down the channel. It did not.
How do you suggest the vessel maintained its position, within the narrow dredged channel, without using the rudder?
 
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  • #127
Regarding the heading change after loss of power, I saw a video suggesting that the change was a result of changing channel geometry from a side branch of the waterway, which in turn applied forces on the ship.

Lemme find the video.

Edit: found it.

 
  • #128
Baluncore said:
How do you suggest the vessel maintained its position
You mean 'heading' not position? Hat could cause a change if the rudder is fixed amidships?

The wind couldn't have been relevant but water currents (tidal and river flow) talk a lot more on a large hull.
I was looking for information about tidal streams in the location but couldn't find any small scale details. But i do know (from information about the Solent) that the tidal streams are often not in step with the tidal levels (I mean the rate of change of). That stream from the west could have nudged the stern of the ship to the east, which woud be equivalent of the rudder turning the ship to the right.
The narrow, deep channel would also have an effect, which the pilots would know all about (more than our speculations)
 
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  • #129
sophiecentaur said:
You mean 'heading' not position?
NO. I mean position relative to the centre line and banks of the narrow channel.

Channel bank suction effects and prop walk, both at low tide, would require continuous small rudder corrections to move back to the middle of the channel. The heading is quite irrelevant, in that avoiding being sucked onto a bank is more critical than pointing the right way.

The vessel would be making small rudder changes sufficient to correct deviations within the dredged channel. Those changes would necessarily result in the average compass heading being correct.

If excessive rudder changes were made, bigger changes would be required to remove the accumulated angular momentum, and the track could become unstable at that vessel speed.
 
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  • #130
Baluncore said:
NO. I mean position relative to the centre line and banks of the narrow channel.
Lateral position: yes, spot on.
 
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  • #131
Baluncore said:
How do you suggest the vessel maintained its position, within the narrow dredged channel, without using the rudder?

Baluncore said:
Channel bank suction effects and prop walk, both at low tide, would require continuous small rudder corrections to move back to the middle of the channel. The heading is quite irrelevant, in that avoiding being sucked onto a bank is more critical than pointing the right way.
Unless something is changing rudder corrections are not needed when running down a straight fairway. Regarding the bank effect We do not know how big it was if it was a factor.

I estimated that the ship if in mid-channel was 30 yds from the marked channel edge and an additional 45 yds from the 30 ft depth contour during much of the channel until it hits the entrance to the Curtis Bay channel to starboard which is 880 yds wide with the distal side of the channel being about 500 yds from the bridge.

The ship traveling 9 mph takes about 1.24 min per boat length. It took 4 minutes from engine failure to collision with the bridge which puts it at 3.22 Boat lengths (0.6 m) from the bridge when power was first lost. That puts it in the Curtis Bay channel entrance where the bank effect goes away until it reaches the distal end of this channel 500 yds from the bridge and by this time it has already turned into the bridge support

The tidal range that day was 1 ft so I do not see much effect due to this factor.

This is the video and chart I used to form my opinion. There is obviously information we do not know. I still believe the captain tried to stop the ship as seen by the black smoke pouring out until the ship hits the bridge.



https://www.charts.noaa.gov/OnLineViewer/12281.shtml
 
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  • #132
Baluncore said:
Channel bank suction effects and prop walk, both at low tide,
The nearest experience I have of this sort of effect was in a sixty foot canal narrow boat - not dissimilar shape. The channel bank suction aeemed to be a surface effect. You could see the bow wave following between a well defined bank (vertical canal sides) and the hull and you had to correct for the suction (unstable course) as you went close in. I have a feeling that a shallow dredged Vee channel would not necessarily talk as much. At low tide, the effect would be more, of course. But we'd have to wait for the experts to pronounce on that. At this stage, it's not much better than idle chit chat (fun though it can be).I can imagine what the lawyers would do with what we have to say.
 
  • #133


Nice stills and videos.
 
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  • #134
gleem said:
Unless something is changing rudder corrections are not needed when running down a straight fairway.
Are you saying that because the channel is straight, they did not use the rudder, and it could not have been making a slight starboard correction, at the moment they lost rudder control?
 
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  • #135
nsaspook said:


Nice stills and videos.

About 10 minutes in, he shows close-up pictures of the bridge that someone took while on a Carnival cruise. I passed under that bridge in 2013 in the same way. I need to see if I've got pictures of it also. :wideeyed:
 
  • #136
Astronuc said:
As for the ship, the lesson learned here is that such ships need to have independent systems to ensure navigation/steering/rudder control in the event that the main power plant (or whatever systems provides power to the navigation/steering system) shuts down.
Is this realistic?

The rudder works in conjunction with the main engines. It redirects water flow, providing a force. If the main engine is down, the rudder becomes much less effective.

There are aux engines, but as I understand it, they are too small to drive the ship, and in any event, are not hooked up to the shaft. Do we require ships to carry two complete redundant engines?

Further, what about damage to the rudder itself? Maybe that wasn't what happened here (but maybe it was), but it could happen. Do we require multiple rudders as well as multiple engines?

You are familiar with another sector, where one technology has been made two to three orders of magnitude safer than its predecessor. Unfortunately, the reaction of most of the public has been "it's too expensive".
 
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  • #137
Vanadium 50 said:
Is this realistic?
I think thrusters could provide limited redundancy, if the auxiliary/emergency generators are big enough and are online during sensitive operations.
Speed limits and capabilities should be matched and requirements updated, but 'feels' doable.
 
  • #138
Thrusters, despite the name, have almost no thrust. They will not get a ship to 7 knots, and so they will not stop a ship at 8 knots. They are good for "fine tuing" as a ship is docking, but not for, for example, getting out of the way of a bridge.

Technically, this is a solved problem - go to diesel-electric. Diesel turns a generator, which powers the motor, which turns the shaft. Now your auxiliaries can do the same thing. This is a lot more expensive, and it's not clear it's even helpful, because now there are more things to break down.

It's also less efficient, which means higher costs. Global shipping is a $200B a year business. Knocking down a bridge that takes $2B to fix is a 1% perturbation. A 10% hit on fuel economy to prevent this makes no economic sense.

Further, 10% more fuel means 10% more pollution. Is that a good idea?
 
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  • #139
Another propulsion loss situation while leaving port... Also, fuel issues on Dali

 
  • #140
Vanadium 50 said:
It's also less efficient, which means higher costs. Global shipping is a $200B a year business. Knocking down a bridge that takes $2B to fix is a 1% perturbation. A 10% hit on fuel economy to prevent this makes no economic sense.
I was thinking the same thing with respect to the pier supports. Upgrading all of the supports around the world to account for the much larger ships would probably be equally costly. But, when there is only one major hit around the world every decade or so, the ROI doesn't work out well.

I find it interesting that there is a tunnel portion of the bridge outside the naval base in Norfolk VA. I guess the military doesn't want its ships trapped by a bridge collapse.
 
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