Watching a discovery special about a replenishment ship the other day, and it had a large sign by the bridge (where it’s easily visible to anybody on the front deck) outlining the emergency breakaway process.
It included, in bright red, a reminder to “not cut or disconnect tensioned lines”. *Why is this such a critical thing?
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Also, they include stop pumping, disconnect hose (on receiving ship) and retrieving the hose as the first steps of an emergency breakaway.
If your seconds away from crashing into another ship, why are they worrying about that stuff? Wouldn’t a collision cause far more damage to both vessels than any sort of unexpected disconnect or loss of hoses?
Because if the line is under tension, cutting it will release the tension and give the line considerable kinetic energy, whipping it about in an unpredictable & uncontrolled fashion.
Cutting a slack line will not have the same effect.
Just noticed a minor error in my post. The sign is facing the AFT deck, not the fore deck. Makes a lot more sense since that’s where most of the transfer is done.
I haven’t seen the documentary but in my experience as a sailor aboard a US Navy Frigate emergency breakaway was about wrapping things up immediately. We always kept enough distance from the supply ship that a collision was highly unlikely, even in the roughest seas. During refueling we had three highlines carrying one supply hose each to the forward, amidships, and aft receiving stations. In addition to fuel there was also the transfer of mail (Yay! Mail call.), supplies, documents, and sometimes personnel. The main concern was keeping the two ships parallel so as not to part the lines. We did have a supply hose disconnect at the forward station one time during refueling which coated the entire ship and everyone on deck with black oil. Fortunately Petty Officer Peanuthead was upwind of the break and suffered no harm. Lucky me!
Keep in mind an emergency breakaway is a very, very fast maneuver, but not necessary an immediate one.
You could have an emergency breakaway due to an operational threat such as submarines in the area, or due to a mechanical threat such as the loss lf a gyro compass.
So you want to disconnect in a matter of a minute or two. But there are tens or possible a hundred men on deck. And line under tension being cut can snap though them and kill and main many. So just pulling away and putting all those men in danger by cutting lines in tension when there is not a necessity to do so isn’t prudent.
What he said, I was on an LHD, and it was basically the same thing. One time we had to actually perform one, and, as everyone was on stationed we were able to slacken the lines before release, stop the pumps, and fully detach in less than 30 seconds. There were some pre-emptive moments right before hand that made everyone pay attention though.
Usually, even with the emergency breakway procedure (unlike the actual one I described above) you perform the actions in a controlled manner. Mainly to prevent the any of the fuel/oil transfer hoses and lines out of the water as much as possible. The reason being that the slip stream along the hull is very powerful and can pull more line in, ultimately, leading into the props, and that would be bad.
In the actual emergency breakway we had, the lines and hoses went into the ocean and they had a lot of people, and the capstans, working to drag them in ASAP.
That puts things in a rather different light. I was thinking “stop the pumps” and “disconnect the hoses” alone would take 30 seconds between giving the order, verifying it,* and people getting into place.
I also hadn’t considered the hoses getting tangled in the props. I was thinking reeling in the hoses was to avoid damaging the hoses/nozzles, dinging the hull, or dumping fuel oil into the ocean, fairly minor concerns compared to even a low-speed collision.
I’m pretty sure high-tension lines aren’t going to be immediately fatal if cut. Mythbusters busted that one. Plus, I’ve seen video of when the arresting cable on a carrier snapped, and it only resulted in broken legs (albeit for everybody within a few yards of the line, across the entire width of the deck). There’d probably be a few broken bones and a lot of bruises, but no decapitations of amputations.
Anyway, thanks for the answers all, especially Peanuthead and the others with first-hand knowledge.
Mythbusters were just testing whether a breaking cable can cut someone in half. There are many more ways a breaking line can be dangerous besides that. A heavy mooring line has a lot of mass and very substantial energy, and when one lets go, what happens next is in the lap of your favourite deity. If there is something heavy attached to the line (like a shackle) it can smash someone’s head in. If the line wraps around someone it can throw them like a rag doll and how badly they are then hurt depends on what they hit when they land. I’ve been practicing law in the maritime field for a few decades. People getting hurt by broken lines is relatively common. I haven’t handled a death case yet but I’ve seen some serious head injuries and some very close calls.
Mythbusters tested this with metal cable.
The stuff they taught us about in the Navy was synthetic lines: “Synthetic line snapback!”
The problem is that synthetic lines stretch like rubber bands, storing far more energy than steel cables, and when they part, everything in their path is in trouble.
I remember seeing films where guys without legs were explaining how they lost their legs to synthetic line snapback.
Regarding emergency breakaway… As I recall, it was the way we normally ended underway replenishment. In other words, non-emergency breakaway was rarely done at sea. I believe this was done for training purposes: if you always finish the job by doing the emergency breakaway procedure then it isn’t difficult to do in an emergency.
It is my understanding that all Navy ships have a theme song that they play at that precise moment.
On my ship, the Nimitz, they played the theme song from the film The Final Countdown, an 80s time-travel flick where the Nimitz turns up in December 1941 by Hawaii. It’s actually a pretty good tune.
So it went like this on the 1MC…
crackle EMERGENCY BREAKAWAY!, EMERGENCY BREAKAWAY! … {rich movie music plays} … {flurry of activity}
You only get one guess at what the theme song was for the USS Enterprise.
The USS Ranger was the Will Tell Overture, as it was the theme to “the Lone Ranger” TV show.
I recall seeing footage in the navy of flight deck operations where cables snapped causing serious harm to those caught by the cable but I cannot recall if limbs were severed or not. Crewman lost limbs but it may have been after the fact in surgery, not a huge difference in the end though. A lost limb is lost limb whether immediately or within the week.
Lets say that the reason for the abrupt end to the unrep operation was that a bomber had lit up the ship and launched a couple of vampires and now you got the whole ship assuming combat stations with the ram , sam and as always the marines with their muskets.
How easy were the hoses and what not, to break away from the ship and let em sink, while your captain is putting the pedal to the metal.