As long as a boat is moving through the water, the rudder is effective whether the engine is running or not (obviously: sailboats steer just fine!). The Dali was still coasting through the water at about 8 knots when the engine stopped. The seemingly bigger problem was that with the low-voltage bus unpowered, the rudder could not be commanded to move at all (until an emergency generator came online which restored limited rudder control ability).
I’m still curious to see a final report that explains why the ship changed course at all. It was on a miles-long straightaway with zero wind, it seems like it should have safely coasted under the bridge even with no power or ability to move the rudder.
Even if there were zero wind (the NTSB preliminary report says 2 kts of wind, which is pretty close to zero) there would be current in the channel. I didn’t see anything in the preliminary NTSB report that said how much current there was in the channel or in which direction (large ships do try to leave port on the outflow after a high tide, the previous high tide in Baltimore March 25th was at about 8 pm, low tide was going to be 2:20 am on March 26th)
I believe that I read that they intentionally steer a little bit to the right to offset the current from that & just after they aimed it a bit right is when they lost power so they couldn’t steer back to the center of the channel
That would explain it. It looks like they were making a deliberate attack on the bridge the way it accelerated to the right. Most fatal aircraft disasters are a series of events that add up. All the planets aligned on this one and the bridge came down.
I’ve always been overly cautious from a planning point of view. I see the bridge without any buffer structures as an accident waiting to happen. It might never happen but if it does what are the consequences? In this case It’s billions in damage and loss of life. It would seem prudent to add on tug time to departing ships to the cost of doing business.
And I would point out that steering to the right meant a longer travel of the rudder back to a left trim with the rudder taking longer to move due to the power shortage. A back-up power source would be a good modification. There should be uninterrupted rudder control regardless of the generators.
For a certain very low value of the word “effective”. Sailing vessels have far larger rudders in proportion to their size precisely because they are relying on movement through the water for steerage way.
Large commercial vessels rely almost entirely on the effect of prop wash on the rudder for steerage at relatively low speeds as here.
IIRC, in the NTSB report, there is a backup power source for the steering system but it puts the rudder into a slow-mode (moves more slowly) due to less available power to move it.
Correct but it’s not an effective backup if it works at a slower speed. Imagine if your car steered slower when trying to execute an emergency maneuver.
In this case it’s a massive ship in a harbor “china shop”.
Of course I can’t find a cite when I need one. But I believe ballast is normally treated before release and the amount they’'re taking off roughly matches what they put on to stabilize it.
Commercial vessels freely take on and discharge water ballast routinely as they take on and discharge cargo.
When you first made your comment I thought perhaps you had heard that damage had (or might have) caused the ballast to become mixed with bunkers or something like that. This can occur in a casualty although I wouldn’t have thought it would have occurred in this casualty due to the location of the damage.
Unless there is any specific problem with this ballast, and if you are just assuming ballast water is treated routinely, your comment has no foundation.
Honestly, it is probably sufficient 99.9% of the time. The ship spends the vast majority of its time (when moving) in the open sea where this is more than sufficient. As it happened, the power failure happened at the worst possible moment. A few minutes either way and this disaster would not have happened.
Engineers generally don’t build cars and planes and ships to be safe in 0.1% of cases. If they did, no one could afford to travel or ship things.
While bilges are usually not the cleanest part of the ship, it may be simply the organisms in the ballast water - Maryland is one of a handful of states that have laws regarding the way ballast water must be discharged:
States: Legislatures in the states of California, Hawaii,
Maryland, Michigan, Oregon, Virginia and Washington
have enacted laws within the last several years addressing
ballast water discharges. These laws vary greatly from
state to state. Some are essentially equivalent to the
USCG’s program, with additional requirements for submitting ballast water reports to the state (e.g., Virginia and
Maryland), while others are much more stringent than the
USCG’s program (e.g., California, Michigan and Washington).
It could also be that the ballast water is also contaminated with bunker fuel or who knows what else, but there unless the Dali’s ballast water was taken on in Baltimore, discharge should not be as simple as just pouring it out
I found the source I got it from and it’s a clip entitled Refloat process in post 440. It’s not backed up by anything and may be based on the standards established for dumping ballast. So I agree it has no foundation based on the video.
Ballast water is not kept in bilges - it is kept in ballast water tanks.
The requirements concerning biological concerns are IME essentially always complied with by exchanging ballast water in the open ocean. By doing so, the ballast on arrival is considered clean enough for local discharge. UV treatments per Magiver’s cite are far too much of a hassle/costly for the many thousands of tonnes of ballast involved, when simply exchanging at sea is possible.
The Dali is highly likely to have exchanged at sea before arrival at Baltimore. It was an operational error if it had not.
Exchanging at sea is not possible in this case - the Dali is currently stuck in an estuary!
Unless the water was exchanged close enough in to the port to meet Maryland’s legal requirements, it seems like the prudent thing to do would be to pump the ballast water out into a barge that can then dump it at sea
It was pumped in to shore up the ship after the demolition and the amount pumped in is the same amount they will pump out. Unless the ballast system was already compromised with some other chemical I’d expect it to go back into the bay.
A ship leaves Port A with ballast taken on in that port which may be biofouled. While on the high seas on a voyage to Port B, the ship exchanges that ballast with water taken on in the open ocean which will not be biofouled. The ship then is free to discharge that ballast when in Port B.
This is typically all that is required. I don’t have time to do a deep dive into Maryland’s requirement but from my quick review of your cite that is all that is required by law.
The Dali should (if all has been done properly) have arrived at Baltimore with exchanged ballast that it is free to discharge in Baltimore.
You need to understand that what you are complaining about because you happen to have heard of this practice because of this casualty, is done in every port in the world, every day.