Not sure Old School - even with a freewheeling prop - there is alot of water going past the rudder at 7 kts. Giving the pilot the benefit of the doubt and excepting he is a trained professional. I am starting to doubt he ever got a rudder back, or if he did it was very late in the situation.
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But you have a stbd swing already going so need enough water going past the rudder to check that swing and then to start a swing to port but then I have never conned a ship like this while coasting so I am only speculating however seems like it is asking a lot to make happen in a short distance
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This is from “MacElrevey’s Shiphandling for the Mariner” which is the reference I’ve always used.
"Perhaps the most fundamental misunderstanding about shiphandling with an anchor is the belief the a ship sheers in the direction of the anchor that is put down. This is not so.
The hawsepipe is too close to the center line for which anchor is used to make a difference. What’s being done with the engine and rudder is what matters.
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I seriously doubt any anchor was dropped to attempt to shear the ship away from that bridge pillar but rather in the prayer that an anchor down might stop her before the strike
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Indeed - I believe a 100% correct.
if that’s the case, why not drop both anchors? Two is surely better than one…
The point I was trying to make was wrt why the ship was turning slowly to starboard.
If in fact the rudder was to starboard while the power was lost than having an anchor down may have shortened the radius of the turn.
In my first post on that topic I didn’t mention which side anchor was used because it didn’t seem relevant.
Could be any number of reasons why only the port was dropped.
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I don’t know why they didn’t either
All in all, the pilot did a hell of a good job in a crisis. He saved lives.
There is probably a built in bias toward dropping anchor in response to an emergency loss of power and steering in tight quarters.
In hindsight, dropping an anchor may have been a mistake that exacerbated the swing to starboard into the bridge support, rather than checking the swing.
If the intent was only to slow the ship down to reduce the force of impact on the bridge, then dropping both anchors would make more sense. Two is twice the drag of one.
Although, I wonder how effective dragging two anchors at 7-8 knots really is, and how much it would actually reduce the speed of a heavily loaded ship in a short time.
Imagine the public criticism the pilot would be getting if he didn’t at least try dropping an anchor!
Again, the pilot did a great (but maybe not perfect) job in the heat of the moment.
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Not sure if you read the Viking Sky accident report posted a few weeks ago, but the Sky dropped both anchors. Granted it was in storm conditions and probably a rocky floor, but it ripped the flukes right off. Stopping 100k tons moving at 7kt in one minute is not only not what they’re designed for, it’s a pipe dream to think it’s even possible.
But you’re right, they’d be publicly damned if they hadn’t dropped one. Speaking of which that’s a good reason to start with just one, so you still have the second to use when you rip off the first?
According to NTSB timeline
01:27:04. The Pilot gave an order to drop the port anchor. And additional steering commands.
2 minutes later
01:29:00 VDR records V/L making 7 knots, audible sounds of contacting bridge pier.
No actual time for the actual anchor being let go.
No mention of time for noise of anchor going.
No mention of any further command for the anchor.
No mention of how much cable.
So the port anchor probably got let go at some unknown point after 01:27:04 after the deck hand, heard the instruction reacted, reached the brake, released the brake.
If the Ship was proceeding along the channel at 8 knots when power was lost and still doing 7 knots when it contacted the bridge pier?
Was the brake ever re applied?
Oh well never go aground with both anchors in the pipe. So they say.
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The pilot did exactly what he was trained to do. The latest report in gCaptain says it is not clear when the anchor was dropped before or after the impact. The only thing the forecastle party would have had in their field of vision would have been their bootlaces. That is the only reason casualties were confined to those actually on the bridge.
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But when you are only seconds, or at most a minute from hitting a bridge, what do you save the second anchor for?
And yes, I do understand they are not potentially designed to take the shock load it would get generated if the anchor stuck to the ground, but likely the anchor would drag creating extra drag to shed speed. It would seem the possibility that they did something is better than doing nothing.
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Could have got even more interesting if it had dragged an anchor through the HP gas line it is currently sitting on
Has to do with the amount of chain let out in each case.
For stopping, slowing or turning short the recommended amount of chain paid out is 1-1/2 to 2 times the depth. At this short a scope the anchor will not dig in and hold, little chance of parting the chain or overloading the brake.
The standard rule of thumb for anchoring is 5-7 times the depth. In the case of the Viking Sky might just let everything out and take the risk of something letting go.
With the Dali not much chance of getting the ship stopped but hopefully to slow the ship or maybe gain a little time. If they had gotten the engine back would have been good to have an anchor or two down.
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I have some control system experience in a different industry. There we were always worried about cyber attack on the control systems via the maintenance internet connections.
Is there a possibility of this being a Cyber Attack?
Is it true the ships systems are automatically monitored from shoreside locations?
Would shoreside equipment providers have the ability to monitor and diagnose onboard systems?
Is it possible for those ship board systems to become compromised , attacked, by a shoreside hacker?
The attacker could take over control and shut down onboard systems, e.g. generators directly. Or perhaps they could create false equipment alarms, say oil pressure failure, on the main driver and generators.
Or perhaps the hack would be to garbel up the automation procedures, so that devices restart procedures conflict.
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Did anyone check the rudder is still there?
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Possible but extremely unlikely.
Systems are monitored but it is a one way street. They cannot control or access any automation related systems to perform maintenance remotely.
I do not know what system that the Dali was using for relaying data, if they were even set up for relaying data. I don’t know off the top of my head when that system is required to be implemented. The systems that I’ve used relay fuel consumption, engine speed and power from the machinery side. From the deck side it relays the ship’s heading, speed (not sure if it’s STW or SOG or both) and I think relative wind and strength.
In my experience, all of the automation is air gapped. The above machinery information comes off of measurements that are independent of the automation. For example, the fuel flow comes off of a fuel meter that does not tie into the automation. The ME power and RPM come off of a torsion meter on the shaft and does not tie into the automation.
There is always the possibility of a Stuxnet type of thing coming in through an automation update via a technician visit. In order to do this successfully though, you would need to compromise multiple independent systems as the automation running the engine room is a separate, independent (and air gapped) system than is used for steering. In my experience, the autopilot system and machinery automation are also different manufacturers.
My professional opinion is that it is improbable that this was a cyber attack. The odds of timing this just right regarding the position of the ship in relation to the bridge are pretty small, particularly with contending with potential currents and the unpredictability of maneuvering in general. Additionally, why just aim to knock down the bridge? Let’s say you did hack the system. Why not cause a delay in sailing as well so that you could hit the bridge during the commute? Through out a couple of alarms during startup that would indicate faulty pressure transducers to a critical piece of machinery and you could easily use up a few hours at the dock while they’re swapped out.
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Chief MAKOi point of view
Cyber-Attack and the Rise of Autonomous Ships | Chief MAKOi (youtube.com)