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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 15th Jan 2015, 07:56
  #2061 (permalink)  
 
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I have not had time to think about what kind of aerodynamic forces would shape this 'hand'.
It is very hard to imagine that a horizontal stabilizer fails due to overload (or a "hand").
Having significantly less span than the wing, high "twisting" loads due to roll are impossible, the wings will stop the aircraft rolling fast enough to create significant loads on the stabilizer.
Any high up or down forces would immediately result in big AoA changes, at cruise speed that would mean enormous g-loads, which would most probably rip of the wings before the stabilizer.
So the only aerodynamic scenario I could call remotely likely would be an asymmetric actuator fault, meaning one elevator deflecting up and the other one deflecting down (commanded by the computers to counteract the pitching moment caused by the faulty actuator). Given the fact that there are two actuators per elevator, and we never experienced such scenario, I would not consider this likely.
Thinking of the Alaska Air trim actuator accident, a scenario like that might be possible, but that would have most likely also resulted in an in flight breakup and a much wider field of much smaller debris.

So I do (so far) not believe in any horizontal stabilizer failure scenario. It all looks more like the Aircraft hit the water first with the tail, which caused all the damage.

With respect to cutting the tail section, I found the upper skin panel just behind the pressure bulkhead very interesting (don´t have the link to the photograph currently): All stringers are buckled, so obviously there has been high up-bending loads on the tail. Either due to high forward momentum from the VTP with high horizontal deceleration, or due to impact forces on the tail from below, indicating an impact with high AoA. Cutting in that area is probably destroying some evidence...
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Old 15th Jan 2015, 08:47
  #2062 (permalink)  
 
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Originally Posted by glendalegoon View Post
someone mentioned clearing the BEANCOUNTERS from responsibility, blaming instead a lack of required standards

SO


Back in the beginning, there were no standards and we learned the hard way what had to be done to keep things safe and assure passengers there was as good a chance to get from A to B on an airliner as on a train, ship, car, or horse.

And they did it.

And then the regulators codified many of those same things.

BUT THEN came the cheapos. IF THE FAA or over seas version hasn't mandated it, then WE DON'T HAVE TO DO IT and can save money.

<snip>.

We have codification not only in transport but currency, food and many other areas of life because there have ALWAYS been 'cheapos', scammers, fraudsters and the rest of them. Don't kid yourself the past is a halcyon period where everyone did everything right without scrimping. Some areas it hurts the pocket, others it has often been lethal - food for example.


BBC News - 10 dangerous things in Victorian/Edwardian homes
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Old 15th Jan 2015, 09:12
  #2063 (permalink)  
 
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A real time empennage failure from the archives...

For those of you born too late, Google "MD 80 test flight crash" to find a youtube video of a intentional hard landing. The tail separates, and that's at about 1200 fpm descent from memory. Imagine hitting water instead of a runway with the gear down and its not too hard to expect to see exactly what is being seen in this debris field.
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Old 15th Jan 2015, 09:52
  #2064 (permalink)  
 
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If the EASA emergency AD relating to blocked AOA probes is relevant then this investigation could get very messy. I guess we will know soon enough.
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Old 15th Jan 2015, 10:48
  #2065 (permalink)  
 
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I just learned that indonesia is trying to decode the boxes themselves instead of sending them to established and respected labs in other countries.
What, exactly, does "trying to decode" mean?
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Old 15th Jan 2015, 10:48
  #2066 (permalink)  
 
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An important learning point for SLF arising from the Ethiopian crash off Comoros mentioned above (Ethiopian 961 in November 1996) is that there were a few survivors, but it was reported that many more might have survived but that they inflated their lifejackets before exiting, so couldn't get out (and probably blocked others). We're always told "don't inflate before exiting", and that's why,.
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Old 15th Jan 2015, 11:44
  #2067 (permalink)  
 
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Originally Posted by Low Flyer
What, exactly, does "trying to decode" mean?
The DFDR memory module contains a long string of 0’s and 1’s, called “bits”. Twelve bits comprise a “word”, many words are contained in a 1-second “subframe”, 4 subframes form a “frame”. The meaning of the thousands of words in a frame is defined in a “Decoding Document” that is submitted to the authorities when an airplane obtains it registration. The first word in each subframe contains the date and time of the subframe. Each of the subsequent words is dedicated to one or more of the thousands of parameters recorded.
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Old 15th Jan 2015, 12:43
  #2068 (permalink)  
 
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Originally Posted by Gysbreght View Post
The DFDR memory module contains a long string of 0’s and 1’s, called “bits”. Twelve bits comprise a “word”, many words are contained in a 1-second “subframe”, 4 subframes form a “frame”. The meaning of the thousands of words in a frame is defined in a “Decoding Document” that is submitted to the authorities when an airplane obtains it registration. The first word in each subframe contains the date and time of the subframe. Each of the subsequent words is dedicated to one or more of the thousands of parameters recorded.
In addition, before you can get to those 1s and 0s, you need to decompress the data, which is stored in a special and proprietary format which compacts the data to be able to store as much as possible in as small memory as possible.

The decoding document above is basically an OEM thing, but the FDR manufacturer is the one who knows how it's compressed. that's another set of special software required, with the right decoding info too.

I believe the 9/11 truthers have been trying for 12+ years to decode one of the "raw" FDR files from one of the aircraft that they somehow acquired, with no success because no-one who knows how to do it - which is a pretty closed community - has any interest in providing the information required. In this case, it's won't be the same reluctance, but it's a bit of an art, so if you've never done it before, even with the right info it might take a while ...
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Old 15th Jan 2015, 13:15
  #2069 (permalink)  
 
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Importance of locating ocean crashed rapidly

Quite some number of contributors have expressed the opinion that location of wreckage after and ocean accident is not particularly important. These opinions also extend to the relative importance of investigating the primary cause of the incident versus the blow by blow analysis of every aspect.

I think these attitudes are probably statistically appropriate, but they do not accurately reflect the general consensus and policy that has been adopted more or less since the start of aviation.

The statistical chances of surviving ditching in the ocean are very small. Yet, every passenger aircraft has life jackets, rafts, passenger safety briefings and so on. Clearly, it is the intention of the air travel industry to give the passengers at least a reasonable chance of surviving a ditching event.

In those circumstances, I find it extremely difficult to understand why a practical and effective systems to locate ditched or crashed aircraft have not been mandatory for many years. If you survive a ditching you will not survive for long in the ocean without rescue. Surely location is a vital ingredient? In addition, a collateral benefit would be to reduce resources being wasted on SAR.


For those that suggest that it is difficult or impossible to design an effective device for locating an ocean crash site; I would suggest you are as wrong as wrong could be. It would be a simple project even in grade school.


If it is our intention to abandon aircraft and passengers at sea, in the event of ditching, then please remove the emergency safety equipment and stop these pointless passenger safety briefings.
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Old 15th Jan 2015, 13:34
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Originally Posted by wheelsright View Post
For those that suggest that it is difficult or impossible to design an effective device for locating an ocean crash site; I would suggest you are as wrong as wrong could be.
For the scenario you draw up, there are ELT's and rafts. A survivable water landing and successful exit has been provided for. Now, is it sufficient to the task? In New York it was, but that was not "out at sea" but on a river in the biggest city in the nation. How many at sea ditchings have happened in the last 40 years that were survivable? What were the cues that got search and rescue teams to the location?
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Old 15th Jan 2015, 13:38
  #2071 (permalink)  
 
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If you survive a ditching you will not survive for long in the ocean without rescue. Surely location is a vital ingredient?
All transport aircraft are required to carry Emergency Locator Transmitters that can be manually deployed by the crew after a ditching. Therefore your point about the delayed rescue after a successful ditching are invalid. However, I'm not sure about the regulations regarding automatically deployed beacons that would be useful in the case of a crash rather than a ditching.

Distress radiobeacon - Wikipedia, the free encyclopedia

Last edited by Airclues; 15th Jan 2015 at 16:38.
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Old 15th Jan 2015, 13:51
  #2072 (permalink)  
 
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@A0283: "Before doing that, my line of thinking on water landing (before I read your reply, so there may be some duplication in it) was roughly thinking about two different and both basic scenarios."


I’m not sure how much more I can add to my previous post without getting too far away from the evidence we have seen so far.

Either of your scenarios are possible, though judging by the condition of the fuselage (slightly pancaked – side bulge flattened top) as shown in the latest underwater pics, it would have been at a very high rate of descent – so I think both unlikely. However, I also agree that the damage to the airframe looks less extensive than the pictures I have seen for the AF447 wreckage, though a lot of bits and pieces can separate when a journey of 4k to the seabed is involved.

Like others on this forum, I am minded to believe that QZ8501 experienced a similar aerodynamic event to that which occurred to AF447, with the airframe basically intact and in a stalled attitude until impact with the ocean. The more important questions that need answering are how did the aircraft enter the uncontrolled state, and why was it not possible for the crew to regain control – was it a technical failure, or was crew incapacitation a cause. However, unlike AF447, we do not need to wait 2 years for the data recorders to be recovered. Hopefully this information should be revealed in the coming weeks or months.

The following link is instructive in providing an idea of how an airframe, a B737) in this instance, crumples when subject to a test 30-ft/s impact velocity, albeit that in this case the impact is on a hard surface.

http://www.cs.odu.edu/~mln/ltrs-pdfs...-3ikus-elf.pdf
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Old 15th Jan 2015, 14:10
  #2073 (permalink)  
 
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Hard surface

As already reminded on this thread, water is a hard surface in such circumstances.

Let's now wait for the outcome of the FDR and voice recorder.
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Old 15th Jan 2015, 14:12
  #2074 (permalink)  
 
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The Strait Times reports on the divers conditions:

PANGKALAN BUN (AFP) - Clinging desperately to underwater ropes, an Indonesian search leader said his divers appeared to be "flying like Superman" as they scoured the seabed in the gruelling quest to recover bodies and wreckage from crashed AirAsia flight QZ8501.

"The current is so strong that it could rip open our masks or drag us into a whirlpool," said Totok Subagio, in charge of a group that this week found the plane's two black box flight recorders, after a lengthy, difficult search. Trained to swim to depths of 45 metres, the Indonesian navy's finest frogmen were drafted in to scour the seabed for wreckage of the Airbus 320-200 that went down in a storm on Dec 28 en route to Singapore.

But in the Karimata Strait between Indonesia's Sumatra island and Borneo island, they have had to contend with rough seas, powerful underwater currents, and weather that changes from bright and sunny one moment to cloudy and rainy the next. Grainy images from specialist Singaporean search equipment Wednesday showed the plane body resting on the seabed, with part of the Malaysia-based airline's slogan "Now Everyone Can Fly" painted on the red-and-white exterior clearly visible.

Divers now face the grim task of examining the main body of the aircraft in the hope of finding more of the 162 victims who were on board the plane, believed trapped inside the fuselage. Almost three weeks into the search, just 50 bodies have so far been retrieved. - 'Two-metre-high wave is a blessing' -
Ferdy Hendarto, head of the navy's local underwater rescue division, described how divers would descend along ropes attached to buoys on the sea's surface marking the locations of the plane's wreckage.

The currents are so strong they can be dragged sideways and at times appear to be "flying like Superman", he said. The search has been tough even for veteran divers, with some suffering nosebleeds after spending too long at depths of 30 meters. Conditions on the surface have also been rough, with some vomiting on their way out to hunt for the wreckage as their tiny boats were hit by waves four metres high.

"In that search area, a two-metre-high wave is a blessing," Subagio said.

Most days divers have had only a four-hour window in the early morning when they can search, before clouds obscure the sun and reduce visibility underwater, rendering search efforts impossible. In the hunt for the plane's two black boxes, divers equipped with devices able to detect the "ping" signals emitted by the devices would inch along the seabed, dropping weighted markers in areas where they picked up the signals.

Digging at the sandy sea floor where the boxes were believed buried, diver Rajab Suwarno succeeded in locating both the recorders, which contain a wealth of data crucial for determining what caused the crash.

One of the boxes - which are actually orange in colour and designed to survive underwater - was trapped under the remains of the aircraft, making it more difficult to retrieve. He described finding one of the boxes: "That morning the sunlight was penetrating the water, it was very clear. We moved some small debris aside and dug in the white sand - and, thank God, we found it."
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Old 15th Jan 2015, 15:39
  #2075 (permalink)  
 
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CVR & FDR update

From Pangkalan Bun (Indonesia) (AFP):

The boxes, which are actually orange in colour, have been flown to Jakarta, where Indonesia's National Transportation Safety Committee is leading a probe into the accident helped by experts from countries including France and the US.

Safety committee head Tatang Kurniadi said 174 hours of data had been downloaded from the flight data recorder, and two hours and four minutes from the cockpit voice recorder.
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Old 15th Jan 2015, 15:41
  #2076 (permalink)  
 
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Newly released photo shows additional parts of wreckage

http://www.straitstimes.com/sites/st...airsi1501e.jpg

From: AirAsia flight QZ8501: Divers hunt for victims in main body of plane - South-east Asia News & Top Stories - The Straits Times
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Old 15th Jan 2015, 16:37
  #2077 (permalink)  
 
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Wheelsright
I do not think that there is any example of a commercial aircraft being located other than by witness, ATC and/or conventional search.
This was my understanding too.
Perhaps someone knows if Sully's landing in the Hudson caused the aircraft ELT to work. I have not heard of any water landing/crash where the ELT worked.

I have only heard of military PLB's (SARBE) actually locating people. I was involved in the SAR for a P3 North of Malin head that nobody realized had crashed till we got a report from a small GA aircraft of hearing a PLB on 121.5.

I have only heard of one successful ELT alert that was the crash of a politician in the North US where apparently the ELT worked.
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Old 15th Jan 2015, 18:48
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It seems reasonable to assume that the tail section may have downflooded more slowly than the fuselage. We know that there are strong currents in the area. Assume w current of 1.7 knots and assume an hour for the empennage to flood to sinking point and it will be 1.7 miles from the fuselage.
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Old 15th Jan 2015, 20:09
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The statistical chances of surviving ditching in the ocean are very small. Yet, every passenger aircraft has life jackets, rafts, passenger safety briefings and so on. Clearly, it is the intention of the air travel industry to give the passengers at least a reasonable chance of surviving a ditching event.
Although surviving an ocean ditching may be statistically low nowadays, the rafts, life jackets, etc are a bit of a throwback to when a survivable ocean ditching was quite possible. Back in the days when aircraft were much slower and had better glide ratios, in the pre-jet age, ocean ditching happened enough to justify rafts and life jackets. Piston engine aircraft were overall less reliable, so might have to ditch in the ocean, while still somewhat flyable. In today's reliable, but fast jet aircraft, the few times things go wrong, there's a good chance they go very wrong. A compromise in air worthiness often is either non-catastrophic or catastrophic. In the old days, there was an in between, where life jackets and rafts might come in handy. You might call it "Semi-catastrophic".
I personally feel good about the life rafts, etc still being in use, even if they are a throwback.
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Old 15th Jan 2015, 20:44
  #2080 (permalink)  
 
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Originally Posted by Methersgate View Post
It seems reasonable to assume that the tail section may have downflooded more slowly than the fuselage. We know that there are strong currents in the area. Assume w current of 1.7 knots and assume an hour for the empennage to flood to sinking point and it will be 1.7 miles from the fuselage.
From a previous post:

"The current is so strong that it could rip open our masks or drag us into a whirlpool," said Totok Subagio, in charge of a group that this week found the plane's two black box flight recorders, after a lengthy, difficult search. Trained to swim to depths of 45 metres, the Indonesian navy's finest frogmen were drafted in to scour the seabed for wreckage of the Airbus 320-200 that went down in a storm on Dec 28 en route to Singapore.

But in the Karimata Strait between Indonesia's Sumatra island and Borneo island, they have had to contend with rough seas, powerful underwater currents, and weather that changes from bright and sunny one moment to cloudy and rainy the next."
The underwater currents are put at more than 5 knots. Not only is that relatively fast it will exert a considerable force on light weight aircraft parts such as the empenage plus some fuselage. It may well drag the empenage further and faster once it has started to sink.

I am actually surprised how close these pieces are to each other considering the strength of the subsurface currents.
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