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Comment by iforgotpassword | Hacker News Reader

I think this is the actual wtf, along with the transfer ui:

> The transfer of thrust comes with an additional level of complexity because the propellors must be transferred one at a time. Half way through a transfer the boat is in a situation where one propellor is controlled by one station and the other is controlled by someone else. At this moment the checkbox labeled “Gang” is automatically unchecked.

Absolutely no surprise that in a moment of panic, the thrust controls end up spread across multiple stations. Why is this even a feature? Not a sailor so just armchair commenting, but in what situation would that be beneficial?

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From what I was able to infer this is the use case of “Splitting Thrust Control During Station Transfer”

(btw I made that up just based on my reading of it. I don’t design Navy ship subsystems for a living - I work on specialized subsystems like these)

The temporarily assigning control of each propeller to different stations would require the automatic deselection of a synchronization (or "Gang") function during the transfer.

Why weren’t they properly trained on this? How did they get into this situation unknowingly?

I would assume a provided manual by the manufacturer would have trained the Sailors on how to properly perform this function.

This sounds like a more exceptional than routine use case.

I've experience of steering a twin prop 50 tonne SAR vessel so quite a bit smaller than this but still same principles. We also have strict procedures for transferring command of the helm between different stations. There is never a situation where you would want the throttles for each prop split between command stations. There is almost never a situation where you would want the throttle controls at a different station than the helm (the person steering). The throttles and the rudder interact a lot and in any close quarters manoeuvring situation you want helm and throttles all under the control of one person.

"Never" is a strong word.

I could definitely see value in war-time, if perhaps one was degraded or damaged, and required special attention that might justify having a person focused on it and communicating with the helm.

Right. This is also possible for us, but the engineer needs to go to the engine room and bypass the throttle system and take manual control of the engine management computers to give throttle inputs to each engine. If these computers fail but somehow the engines are still running I know we can mechanically take each engine in and out of forward and reverse gear. In either of these cases throttle orders would go through the intercom or would be manually relayed by shouting along a human chain if the intercom is out. We can also take manual control of the rudder if the steering hydraulics fail, by rigging two sets of block and tackle to an emergency steering tiller. We practice these fairly regularly in drills and I can say that close quarters manoeuvring with manual control of the rudder is not something you would want to do with an inexperienced crew for real!

That's a good argument for independent throttle control being possible, but it's not a good argument for that being the default. When working with safety critical systems (which throttle control absolutely is), it's important to have sensible, easy to understand defaults. The more steps you have to take to do the "correct" thing, the more likely it is that someone screws up one of those steps.

Seems to me a technically advanced enough system like this should probably combine the independent throttles with the steering to some extent? I'm talking out of my rear possibly, but like if a severe enough turn radius was used, maybe then automatically adjust the throttles to make it possible in combination with the rudder?

(as a default)

I think designing a system like that that gave the control necessary and worked predictably would be difficult. I'm not a navy person (the closest experience I have is driving fishing boats on a lake), but I do know that steering a big boat is complicated.

Steering via the rudder, via controlling the different throttles, or some combination has different characteristics. And which one is best would depend on the ocean and weather conditions, overall speed of the ship, as well as many other factors I don't know about.

A computer is unlikely to be able to properly account for all of this. And if it did, it would affect how the ship controls, something that you really don't want to do on a large ship.

Combining multiple controls into one computer managed control can be a good design. But I think it's the wrong design for large ships.

The article does address this. The system did have a computer-assisted driving mode but it was always turned off into manual driving mode as the sailors either didn't understand or trust the automatic mode.

Yeah, I was in the navy actually, but my lane was purely electronics, I too only drive a 15' fishing boat.

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