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Air Asia Indonesia Lost Contact from Surabaya to Singapore

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Air Asia Indonesia Lost Contact from Surabaya to Singapore

Old 12th Jan 2015, 09:05
  #1821 (permalink)  
 
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I do hope he meant imploded .......... and even that is very difficult to believe.
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Old 12th Jan 2015, 09:14
  #1822 (permalink)  
 
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@langleybaston: "I do hope he meant imploded .......... and even that is very difficult to believe."

Given that the cabin pressure is usually maintained at the equivalent of a pressure altitude between 8000 and 10000 feet asl, then it would "normally" be at below sea level pressure when the cabin was almost back at the surface if no "adjustment" had been made from the pressure at cruise.

However, I have also seen comments in other reports that if the cabin enters the water with a rupture allowing water ingress at the end that first enters the water, then the opposite end (which in this case could be the tail), would have air inside that is progressively compressed during the sea entry process by the wall of water entering from the end that the water was coming in, leading to a rapidly increasing air compression in the remainder of the cabin to several bars pressure at the point of rupture. So perhaps that is what the commentator was referring to? If that was the case then only one end of the cabin would have "exploded" and examination of the complete remains of the fuselage would likely confirm or deny that hypothesis?
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Old 12th Jan 2015, 09:23
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I guess "exploded" refers to the fact the fuselage was intact i.e. a pressure vessel. When it hits the water hard, the lower surface is first distorted up / inwards, markedly reducing the "volume" of the pressure vessel. Hence pressure rises beyond the structural limit and in itself causes failures.

Given the nature of impact, I suspect it also gets into complex fluid dynamics with shockwaves etc.

All fairly academic I would think?
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Old 12th Jan 2015, 10:12
  #1824 (permalink)  
 
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3km away from the tail section , does this seem a bit far away
3km is the length of a runway at a decent size airport, with the speed and force of impact together with water currents it isn't really that far.
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Old 12th Jan 2015, 10:16
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Does anyone know why they are keeping the CVRs under water?


Is it so that the sea water does not evaporate, and cause a salty residue?
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Old 12th Jan 2015, 10:24
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It's a bit silly and a little ignorant to be picking the eyes out of the Indonesian response to this incident. Maybe some of the bureaucratic actions regarding permits deserve criticism, but I would say the efforts of the search and recovery teams have been pretty impressive. Maybe they don't quite have the level of experience of their western counterparts, but don't underestimate Indonesians' intelligence, toughness, determination, sense of justice, sense of respect, marine skills, and desire to make this right.

If you are just going to take barely-informed pot shots from the sidelines, it says more about you than it does about them.
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Old 12th Jan 2015, 10:25
  #1827 (permalink)  
 
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Does anyone know why they are keeping the CVRs under water?

Is it so that the sea water does not evaporate, and cause a salty residue?
It's to minimise exposure to oxygen, which is the chemical agent of corrosion.
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Old 12th Jan 2015, 10:33
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"It exploded because of the pressure," he told reporters in the town of Pangkalan Bun on Borneo island, the search headquarters. "The cabin was pressurised and before the pressure of the cabin could be adjusted, it went down - boom. That explosion was heard in the area."

I am puzzled by this explanation and can only assume that the description given may have suffered some misunderstanding in translation. My guess is that the official is alluding to the sound of the aircraft impacting the ocean, and the pressure being that of the hydraulic surge that would have occurred on impact when water ingress through the ruptured underside of fuselage skin would have scoured through the interior, lifting the floor and bursting through fracture points developed at initial impact .

Some of the physics involved with water impacts was covered in post #3719 from the discussion of AF447 back in 2011.

http://www.pprune.org/tech-log/39510...ml#post6402729

The Hudson river landing (1549) is a good exemplar of the damage that hydraulic forces will induce even in seemingly benign situations (flat calm and smooth landing).

https://avtales.files.wordpress.com/...b-photos-2.pdf

Last edited by BJ-ENG; 12th Jan 2015 at 10:53. Reason: typo
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Old 12th Jan 2015, 10:36
  #1829 (permalink)  
 
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(Reuters) - There was no evidence to support the theory that an AirAsia airliner exploded before hitting water two weeks ago, an Indonesian transport safety investigator told Reuters on Monday.

"There is no data to support that kind of theory," said Santoso Sayogo, an investigator at the National Transportation Safety Committee.

Supriyadi, operations coordinator at the National Search and Rescue Agency, earlier told reporters that the wreckage indicated the jet "experienced an explosion" before impact due to a significant change in air pressure.
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Old 12th Jan 2015, 10:38
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Conflicting views between Barsarnas and Indonesia's Transport Safety Investigator thus far. I think it's a little previous calling an "explosion" at this point. All will likely be revealed soon.

No evidence that QZ8501 exploded before hitting water: Investigator - Channel NewsAsia
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Old 12th Jan 2015, 10:42
  #1831 (permalink)  
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Originally Posted by BJ-ENG
"It exploded because of the pressure," he told reporters in the town of Pangkalan Bun on Borneo island, the search headquarters. "The cabin was pressurised and before the pressure of the cabin could be adjusted, it went down - boom. That explosion was heard in the area."
That statement is being retracted now, by NTSC safety investigators.

http://www.todayonline.com/world/ind...plosion-theory
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Old 12th Jan 2015, 10:44
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I've just listened on the radio to an 'expert' in HKG saying that the aircraft exploded because it was forced by the storm to climb to a height at which the stress of the pressurisation inside the hull caused it to 'burst like a balloon'.
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Old 12th Jan 2015, 11:07
  #1833 (permalink)  
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This report in Bahasa says that Navy divers have seen the CVR but it's currently being pinned down by the wing and as a result, they haven't been able to retrieve it today. It's located not far from where they found the FDR, about 20 meters, but because the wing is heavy, they will have to use a "lifting bag" (balloon?) to raise the wing. Hopefully tomorrow it will be lifted (to the surface).

detikNews : Basarnas: CVR QZ-8501 Sudah Terlihat, Tertimpa Sayap Pesawat
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Old 12th Jan 2015, 11:12
  #1834 (permalink)  
 
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@bud leon
Nah mate, this recovery has been pretty abysmal thus far. Look at the photos of the tail section recovery. They won't know what scrape, scratch, break or tear resulted from the crash and which one from the recovery. No post mortems on the bodies recovered thus far... inexcusable. I don't care what religion or other make belief man in the sky you pray to, we (and you) need to know why this happened. Looking at your dead relatives body is what helps us do that. We'll only be a moment, thank you.

Then some rando indonesian investigator makes bizarre statements about exploding hulls, something which clearly they wouldn't have a clue about at this stage.

I can only hope that Airbus is taking the lead on reading out the recorders. And that someone leaks the information on them. Because by golly we'll never know what happened otherwise if Fernandes gets his financially linked buddies in government involved.
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Old 12th Jan 2015, 11:20
  #1835 (permalink)  
 
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physicus

Airbus will get a copy of the data pretty swiftly, as will other parties to the investigation. Unless the Indons are capable of creating a false version (I doubt it) the truth will out soon.
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Old 12th Jan 2015, 11:22
  #1836 (permalink)  
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Originally Posted by bud leon
It's to minimise exposure to oxygen, which is the chemical agent of corrosion.
Although they should have moved it from the salt water it was inevitably found in, to fresh water - the salt doesn't help corrosion either.
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Old 12th Jan 2015, 11:35
  #1837 (permalink)  
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Originally Posted by oldchina
Airbus will get a copy of the data pretty swiftly, as will other parties to the investigation. Unless the Indons are capable of creating a false version (I doubt it) the truth will out soon.
Anyone remember MI 185 and how the NTSC and NTSB (on behalf of Boeing) came to different conclusions on that one?
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Old 12th Jan 2015, 13:09
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I am fluent in Indonesian; I’ve seen and heard the original quote by the Barsanas chief.
Regrettably, there was no error in translation. He really is saying that, in his “analysis,” the plane “exploded” on impact with the water, and that the air pressure differential consequent to the impact caused the passengers’ bodies to be expelled from the plane.

Keep in mind that Soelistyo is not an accident investigator; he’s an ex-military general who now leads the mostly civilian search and rescue agency.
While Indonesia does have some good technical experts, Soelistyo is not one of them and there is unfortunately not a culture of message discipline here.
Expect more premature and cringe-worthy conclusions to be aired: The first was the meteorological agency; the second (and very much under-reported) was last Thursday’s announcement by Santoso Sayogo, the NTSC (Indonesia’s NTSB) lead investigator, that the ping locators will no longer needed, since the tail had been found — even though, at that point, no pings had been detected from the tail; and now Soelistyo’s gaffe.

The best reading of Soelistyo’s remarks is as a “just-so” story to explain the absence of victims’ bodies from the fuselage, which the Indonesian public widely expected to be still strapped into their seats. In remarks as recently as Sunday, Soelistyo repeatedly stressed that the recovery mission will prioritize recovery of victims’ bodies over that of the black boxes. Now he has to explain why the divers under his command surfaced with boxes and not bodies.

The NTSC’s Sayogo should be lauded for quickly rejecting Soelistyo’s speculation: “There is no data to support that kind of theory,” he said a few hours ago. You need some courage to do that to a general here — and one on whom your investigation depends for operational and logistical support.
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Old 12th Jan 2015, 13:25
  #1839 (permalink)  
 
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Just a minor correction - autopsies have been performed on some of the bodies, but not all (or even most). I gather family opposition is the main reason.
Yep, they're doing autopsies on all the foreigners, on presumption of family permission. Autopsies on the Indonesians only if the family permit. There was a church group onboard, so the ME might get higher consent rates than with more Muslims on board.
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Old 12th Jan 2015, 13:25
  #1840 (permalink)  
 
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Nah mate, this recovery has been pretty abysmal thus far. Look at the photos of the tail section recovery. They won't know what scrape, scratch, break or tear resulted from the crash and which one from the recovery. No post mortems on the bodies recovered thus far...
No professional investigator or materials engineer would be confused by scrapes or scratches from the recovery effort.

And post-mortems are performed for each and every body recovered so far. This was already explained before.

It's worth to re-quote bud leon:

"If you are just going to take barely-informed pot shots from the sidelines, it says more about you than it does about them."
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