Yuan Class AIP & Kilo Submarine Thread

[jobjed]

Re: PLAN Yuan Class D/E AIP Submarine Thread

Wow, where did you get documents from the investigation? They were made public? You post is so detailed that it looks like you took it fromthe officer's testimony. I thought that would be classified document...

Whoa, have you used your brain? Perhaps they were intentionally leaked? The Chinese government maintains an official policy of secrecy but it doesn't hurt to leak accounts to boost the military's public image. Have you completed elementary school? Superdog already said he got it from a 'navy office observer' AKA an officer; don't you understand English? Can you stop asking obvious questions? I thought it was pretty obvious such an incident would have its official report classified but maybe that's why it's called a 'leak'?

 

[SamuraiBlue]

Re: PLAN Yuan Class D/E AIP Submarine Thread

According to a "Navy office observer" who was on the boat during the incident, they were patrolling at a "large depth" when they hit the density change (most likely somewhere between 200-300m). At the beginning the sub starts dropping 10m per minute. The on-shift captain first gently increased the speed and used normal procedure to increase buoyancy, but by the 4th minute they have plunged 30m and continue to drop, then they shifted to a higher power/nosier mode and prepares to blow the middle main ballast. By the 6th minute they have dropped 49m and the hull start to make grunting noises. At this time the on-shift captain ordered to blow the middle main ballast, and the boat captain has also arrived to the control room to help.

About 20 seconds later, pipes ruptured with a loud bang in compartment 5 (motor compartment), the crew there have to shut-off the motor and cut power. Upon receiving this report, the mission commander immediately ordered to blow all the main ballasts, and the on-shift captain started damage control alert. At this time the sub has lost power and continue to drop with the tail angled down, it became difficult to stand up without holding onto something.

Fortunately the 3 sailors in compartment 5 were able to quickly seal the compartment and shut off the damaged pipes before too much water came in, and pumping air into the ballasts eventually worked. The sub stopped dropping by the 8th minute after gaining 70.6m of depth. It wasn't mentioned if the sub went over its test depth (300m), it's possible if the incident started well under 200m.

After stopping the drop they did a controlled surfacing and surfaced by the 14th minute. They found that water filled about 1/8th of compartment 5 and many electrical systems were damaged. The mission commander wanted to dive before sunrise to avoid detection, but some of the crew were not very confident if they could continue on. Eventually they managed to fixed necessary equipments within 3 hours to dive again, and they continued to fix as much as they could in the next 90 hours. Despite the boat could only travel at 4 knots and could not reverse, they went on to successfully complete the mission.

Whoa, have you used your brain? Perhaps they were intentionally leaked? The Chinese government maintains an official policy of secrecy but it doesn't hurt to leak accounts to boost the military's public image. Have you completed elementary school? Superdog already said he got it from a 'navy office observer' AKA an officer; don't you understand English? Can you stop asking obvious questions? I thought it was pretty obvious such an incident would have its official report classified but maybe that's why it's called a 'leak'?

I seriously have doubts about the details. Sub hulls do not start showing pressure fatigue by slipping a mere 50 meters below operation floor. If that was true a sub will never maintain hull integrity when scrapping a reef or hit by a dud torpedo (or someone mistakenly hit the hull with a hammer from the inside while fixing a breach).
From experience handling filled scuba tanks slamming against each other during transit, a pressure tank should be able to maintain hull integrity 3~5 times beyond operational strength or it will be little use due to various possible acute strain it may endures at maximum operational levels.
Pipe ruptures, although this may occur there are always various other point that you can close to stop the water altogether so the whole sealing the compartment doesn't add up unless it was a more serious situation.
Still sinking with the motor at full strength at up trim?
The front rudder on the bow or sail are like wings on a plane creating lift which should provide enough to raise the boat if the hull was at full integrity without the blowing the tanks.

I would take a heap of salt with that "Leak".

 

[hydropod]

Re: PLAN Yuan Class D/E AIP Submarine Thread

I seriously have doubts about the details. Sub hulls do not start showing pressure fatigue by slipping a mere 50 meters below operation floor.

Kilos have a maximum operating depth of 240m and crush depth of 300m by most sources. From the article, the boat was already at a high depth when the emergency occurred. Going 70 m below max operational depth would have put a Kilo in grave danger.

Pipe ruptures, although this may occur there are always various other point that you can close to stop the water altogether so the whole sealing the compartment doesn't add up unless it was a more serious situation.

Which is exactly what the crew in the flooded compartment did by turning off all the valves to the ruptured piping. According to the article the compartment ended up about 1/8 flooded so they must have done it quickly. Its not easy, given at say 250m, the water pressure will be about 25 bars and for comparison, a fire hydrant would only be pressured to about 7 to 10bars.
As to closing watertight doors, that is mandatory once battle stations/ damage control stations have been called as stated by article.

Still sinking with the motor at full strength at up trim?
The front rudder on the bow or sail are like wings on a plane creating lift which should provide enough to raise the boat if the hull was at full integrity without the blowing the tanks.
I would take a heap of salt with that "Leak".

Diving plane efficiency increases and decreases with the speed of the boat as it travels. At low crawl speed as stated by the article I would guess speed would be less than 3 knots. Good luck trying to even adjust the trim of the boat with only your planes at that speed, let alone raise your boat's depth, and that applies to all SSKs and SSNs.

Plenty of cases when even blowing main ballast does not immediately arrest the decent of boats in emergencies, let alone in a pycnocline as stated here.

 

[kwaigonegin]

Re: PLAN Yuan Class D/E AIP Submarine Thread

The Yahoo article was poorly written and misleading people thinking the Chinese were saying their sub was patroling or sinking into thousands meters deep and the crew still managed to save the sub. Which was impossible for a Kilo to survive with only max depth of 300 meters. It's correct the Chinese article didn't mention anything of" proving loyalty".

But the Chinese article did mentioned the sub was patroling in an area thousands of meters deep, (the area was thousands of meter deep, NOT the sub, that's what confused most people when reading fast)the sub itself was cruising at hundred(s) meters deep when the incident happened. If the crew didn't react quick and professional, the sub would've sunk thousands of meters deep.

Thanks for the translation. This is why I like this site. I do agree that generally speaking Western media or even English translations from Mandarin Chinese often times are very innacurate and many may even have anti Chinese agendas but it is no different than the news media here when it comes to political news. Some networks have left wing tendencies others veer right. It is up to the readers (hopefully) to filter out the crap and make their own unbias and objective conclusion.

As to this news article most if not all submarines 'don't or can't patrol thousands of meters deep' so that alone should raises suspicions on the literal accuracy. The pressure hull would've implode way before that. Even SSBNs don't go down that deep let alone a Kilo.

As to the 'loyalty' question brought up by Samurai, I will tell you one thing though. Regardless of whether it's in the article or made up etc I guarantee you one thing...When $h1^ hits the fan you are loyal to your shipmates or the guy next to you in the foxhole. You don't do it for country, for pride or for any patriotic reason people like to think you do it for. The simple truth is you do it for the guy next to you. I'm 100% sure those bubbleheads were doing it to not only save the boat but also for their buddies. Those guys have very tight bonds even more so than surface pukes.

 

[SamuraiBlue]

A kilo-class sub can manage full head flank of 21 knots for an hour on batteries alone.
That is what the "higher power/nosier mode" means and still didn't rise. The story is too far fetched for me.


=== Edit ===

25 bars is 36.2595 PSI
Scuba tanks are filled at 3000 PSI at normal. You're telling me that a sub has less hull integrity then a scuba tank by a 100 folds?

 

[hydropod]

A kilo-class sub can manage full head flank of 21 knots for an hour on batteries alone.
That is what the "higher power/nosier mode" means and still didn't rise. The story is too far fetched for me.

You might want to read up on what a pycnocline is, it helps.

In this situation, not only is the boat losing floatation from the lower density of water below, but its also been "pressed down" by the higher density water above the boat. Flank speed in this case might not be enough, which if the article is correct, then it wasn't.

Not to mention that the boat suffered propulsion casualty a further 2 minutes from that point onward into the emergency from flooding of its propulsion section, which would only further exacerbate the situation.

 

[SamuraiBlue]

You might want to read up on what a pycnocline is, it helps.

In this situation, not only is the boat losing floatation from the lower density of water below, but its also been "pressed down" by the higher density water above the boat. Flank speed in this case might not be enough, which if the article is correct, then it wasn't.

Not to mention that the boat suffered propulsion casualty a further 2 minutes from that point onward into the emergency from flooding of its propulsion section, which would only further exacerbate the situation.

As I posted earlier sea temperature and salinity both becomes stable at 200m there could be a down flow current that the sub may have hit but those currents are no faster then a few knots 10 at most. There are no natural variables that can trigger such dangerous effects.

 

[hydropod]

As I posted earlier sea temperature and salinity both becomes stable at 200m there could be a down flow current that the sub may have hit but those currents are no faster then a few knots 10 at most. There are no natural variables that can trigger such dangerous effects.

Ok, to make an analogy: Its a bit like wind shear encountered by an airliner. Your airliner with engines at TOGA settings can lift itself off the ground, but if its caught in a strong wind shear, the plane is going to lose altitude for a few seconds, no matter what thrust setting the pilot sets. Its not the airflow or the current flow that is "pushing" or making the plane/boat lose altitude/depth, but the sudden and rapid change of pressure/density above and below the wings/boat that leads to the rapid change in altitude/depth. Normal correction methods such as airfoil control/dive plane control would have minimal effects while this is taking place.

Add in the much lower speed of submarines, the fluidity of water, combined with much larger area of water affected means that it will take a submarine much, much longer to remove itself from these effects, and the boat will be diving deeper during the whole time without rapid and massive corrections to its trim and angle by blowing all ballast, max plane angle etc.

Also, if say the airliner was flying at cruise altitude and speed: Hitting a wind shear might just mean a change of underwear for some passengers. Same would have applied to a Kilo at 15kts hitting a pycnocline at 100 m depth, change of underwear or a few bruises for the crew and no danger.

However, a Kilo crawling at <3 kt at close to or at max depth hitting a pycnocline (as indicated by the article) is like an airliner at landing approach hitting a strong wind shear at 500 ft height and 210kts TAS. Near certain chance that you are not going to make it, and that is why everyone is applauding the crew of the Kilo for making it out.

Hope that makes more sense to you.

 

[SamuraiBlue]

Ok, to make an analogy: Its a bit like wind shear encountered by an airliner. Your airliner with engines at TOGA settings can lift itself off the ground, but if its caught in a strong wind shear, the plane is going to lose altitude for a few seconds, no matter what thrust setting the pilot sets. Add the much lower speed of submarines, the fluidity of water, combined with much larger area of water affected means that it will take a submarine much, much longer to get out of trouble, and the boat will be diving deeper during the whole time without rapid and massive corrections to its trim and angle.

If say the airliner was flying at cruise altitude and speed, then hitting a wind shear might just mean a change of underwear for some passengers. Same would have applied to a Kilo at 15kts hitting a pycnocline at 100 m depth.

However, a Kilo crawling at <3 kt at close to or at max depth hitting a pycnocline (as indicated by the article) is like an airliner at landing approach hitting a strong wind shear at 500 ft height and 210kts TAS. Near certain chance that you are not going to make it, and that is why everyone is applauding the crew of the Kilo for making it out.

Hope that makes more sense to you.

Sorry but the shallower the depth the lower the pressure due to higher sea temperature and unlike air in our atmosphere there is no large energy source that can heat up a large region of the lower depth of the sea creating a violent upstream meaning there are no violent downstream either, so you're analogy doesn't work deep under the sea.
The down steam I mentioned is due to gravity in which some cooled water falls from the warmer area in which it gains momentum creating a down current and as a result the bottom is pushed upwards at the edge of a rift creating an up current but both currents maintain a constant speed due to it's nature.

 

[hydropod]

Sorry but the shallower the depth the lower the pressure due to higher sea temperature and unlike air in our atmosphere there is no large energy source that can heat up a large region of the lower depth of the sea creating a violent upstream meaning there are no violent downstream either, so you're analogy doesn't work deep under the sea.
The down steam I mentioned is due to gravity in which some cooled water falls from the warmer area in which it gains momentum creating a down current and as a result the bottom is pushed upwards at the edge of a rift creating an up current but both currents maintain a constant speed due to it's nature.

Seriously, read up on what a pycnocline is, feels like I am wasting my breath here. It's a change in DENSITY due to differing salt levels in water. Stop confusing it with effects of a thermocline, which is what you are describing.

As to your scuba tank question, really? Have you thought about the difference in pressure cycles? Duration? Compressibility of fluids vs gas? Even HY100 rated at 100MPa (14500 psi) on a submarine is only good to about 600 or 650 m, so still rated to a safe level of less than 1000psi. Are you going to say that your scuba tank is sturdier than the thick pressure hulls of a Seawolf/Virginia too?