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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 14th Jan 2015, 18:21
  #2021 (permalink)  
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Let's face it... hydrodynamic forces would be capable of anything
imaginable and unimaginable entering water at speeds from 100 kts
upwards. Including twisting and if the tail struck first, tearing it off.
lets see
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Old 14th Jan 2015, 18:21
  #2022 (permalink)  
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To Msunduzi

Surely how it hit the water, and what caused the damage seen is really of little matter.
It may or may not indicate if there was any control at the time it hit the water, but again, that won't help find the cause.
What is needed is the reason that caused the loss of control (not pointing to pilot involvement or not) at some 30k feet above the damage being looked at.
Maybe this is why they are not too worried about the "hacking up" of the wreckage?
My impression is that 'losing control at high altitude' would happen more often (probability wise and statistically), than things getting 'out of control' ( either by weather events (that's one reason why we have pilots who can put things right), or SA loss leading to a flip like the 747 years ago (where the pilot provided both cause and solution, albeit after a significant drop) ). If that is so, then you would have to divide the flight path in altitude steps, call it a 'ladder'. And ask for each step of the ladder what happens, and what the pilots' options are. Like posters do in the interesting stall discussions here. And that also includes the final splash. The whole plane hitting the water or large separate sections ... that points to different possible causes. Which you test by going up the ladder again. Both top and bottom of the ladder are relevant for 'solving' this accident.

On hacking up. Nobody knows what the cause was. Real hacking up would not start until after reading and analyzing the recorders and the investigation being further along the line. The only reason for hacking up now would be transportation requirements (bridges, roadwidth ..etc ... the diameter of the fuselage is 4.14 m ... one lane on western highways is something like 3 m...isn't it?)
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Old 14th Jan 2015, 18:47
  #2023 (permalink)  
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Maybe this is why they are not too worried about the "hacking up" of the wreckage?
I tend to agree. Before the tail was recovered, there was an official statement that the rescuers first priority was finding the casualties, the second was the black boxes.

The main interest in the wreckage, as reported, was about the position of the control surfaces (or "tail flaps" as it was reported) which could give valuable information about the airplane's last flying moments. Based on that information, the interesting pieces would IMHO be the actuators and the THS jackscrew.

Presumably the rescuers also took enough underwater photos and videos to enable them to establish the pre-recovery condition of the wreckage. I'd assume that to be standard practice in this kind of salvage jobs.
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Old 14th Jan 2015, 18:48
  #2024 (permalink)  
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To Lonewolf ...

@A0283: I see your points. Just a thought: once things fell apart, the movement of the water and "how long a given bit floats" may offer sufficient explanation for how the dispersal came about. Or not. You are more likely right in your estimates, as you've examined it in more detail.
At first thought. There might be two 'theoretical reasons' that could explain the 2,000 m. First floating, and second forward speed. But both start with hitting the water and losing the THS and the bottom of the tail with the APU.

On the first, floating. So you have an open tube ... which if it fills, will fill quickly ... if not, the plane might be weighed nose down and keep the open end up for a while (until the swell flows in) and might float around a bit ... at the 1-2 knots published current that distance would take roughly 30 minutes to 60 minutes.

On the second. The forward speed would combine losing the tail followed by skimming over the surface like a flat stone. At say 60-120 knots that would be roughly 2,000 m in roughly 0.6-1.2 min. The impression is that the plane went up and down quite vertical (not far from LKP) and pretty fast. So, that seems to be less probable.... In spite of the fact that the lower aft section may still have been attached (as mentioned, the aft top panel stayed connected to the tail/rudder section).

What it does not explain is the apparent stripping of most interior components..... Which gives a bit more probability on the side of a higher speed and above break up. Also, skimming has lower probability, when reviewing earlier widebody waterlandings.

Theory and practice can be quite different of course. But it gives some idea I guess. And no more than 'some' idea ... at this stage and with the publicly available information.

Last edited by A0283; 14th Jan 2015 at 18:53. Reason: Add ")"
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Old 14th Jan 2015, 19:29
  #2025 (permalink)  
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the wreckage looks very much less fragmented then i/we were expecting

reminds me of 2 tridents that went down with little or no forward speed

PI and ZT both had wreckage/fuselage compacting that looked somewhat like this with wings attached
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Old 14th Jan 2015, 19:46
  #2026 (permalink)  
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someone mentioned clearing the BEANCOUNTERS from responsibility, blaming instead a lack of required standards


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.

THE OLD GUYS shook their heads...they knew better. We are learning the same things over and over again that we knew 40 years ago.

all at the cost of passengers and crew.

So it is beancounters, because they have an excuse, an ENABLER in local regs that aren't as tight as a drum.
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Old 14th Jan 2015, 19:48
  #2027 (permalink)  
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Given the remarkable condition of the fuselage, an attempted but unsuccessful "controlled" ditch in gale conditions?
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Old 14th Jan 2015, 19:55
  #2028 (permalink)  
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There has been some discussion on hydrodynamic forces as cause for apparent damage.

By way of a reminder I would say that my understanding of hydrodynamic force is the forces acting in fluids in motion and not objects that impact fluids such as water. Accordingly unless someone pulls a stunt such as flying into Niagara Falls at their full fury then the question of hydrodynamic force does not really come into play.
The damage sustained to an aircraft impacting against any surface is caused by the dynamic force of the travelling aircraft and not by movement of the surface or depth of the water.
In this instance my money is on the in -flight loss of the empennage as a result of aerodynamic forces imposed upon it beyond its structural limititations.
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Old 14th Jan 2015, 20:35
  #2029 (permalink)  
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in this instance my money is on the in -flight loss of the empennage as a result of aerodynamic forces imposed upon it beyond its structural limititations.
I just would not have expected the remainder of the airframe to survive anything like to the extent it has. It appears borderline surviveable, and the fuselage (what is visible) still looks circular.
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Old 14th Jan 2015, 20:36
  #2030 (permalink)  
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Boomntown - doubt it. You would need a failure that left the pilots flying, but all radios disabled.
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Old 14th Jan 2015, 20:42
  #2031 (permalink)  
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A bean counters job is to count beans, not dictate morality and standards. Their jobs is to the best of their ability to come up with ways to legally save money. Failure to do that is not doing their jobs.

Its other peoples jobs to evaluate those recommendations and consequences of, and they should do that to the best of their abilities.

If some thing is serious enough, as a society we codify it.
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Old 14th Jan 2015, 20:43
  #2032 (permalink)  
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Wasn't there a theory going around that the inflated rear exit slide was at first attatched to the severed rear section causing it to float away while the main body sank immediately. The slide subsequently detatching in the swell so that the tail section sank some distance away?
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Old 14th Jan 2015, 20:52
  #2033 (permalink)  
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QUOTE:in this instance my money is on the in -flight loss of the empennage as a result of aerodynamic forces imposed upon it beyond its structural limititations.END QUOTE

Can anyone tell me if there has ever been a failure of the empenage in ANY Airbus Product? ;-)
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Old 14th Jan 2015, 20:56
  #2034 (permalink)  
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Aerodynamic and Hydrodynamic etc


With respect, nothing that I have seen so far leads me to believe that the main body of the aircraft was separated from the aft section prior to impact with the surface of the ocean. If it had separated then one would expect to see a more intact empennage; no burst bulkhead and more of the aft floor section still attached, or some remnants of floor frame. During a water impact, the hydrodynamic scour that occurs forces the floor section upwards, and in the process causes it to become detached from the side frames exactly what we see in this instance. Ok, the floor frame complex could have pulled out in one if aerodynamic separation was the cause, but that still does not explain the burst bulkhead. The most likely reason for the distance in separation is probably down to the fact that since this part of the intact aircraft probably made first contact with the water ( ie: the aircraft is in a pitched up attitude), the break that occurred between it and the main section was well developed by the time the lower skin of the the main fuselage failed, thus allowing hydraulic surge (impulse) to flow through the cabin in fractions of a second, particularly to the now open ended rear scouring everything in its way. Given that the APU and other heavy bits appear to have detached, plus maybe some level of buoyancy remaining (inflated rear exit slide ) in the aft section and a 5k current, it is not difficult to imagine the aft section drifting apart from the heavier main body. The rear end of the fuselage, as seen in latest photo, appears to show floor frames presumably pulled out from the missing aft section once the connections to the side frames failed. There is also the evidence of one of the data recorders being found under the wing. If the aft had detached in the air, then is it probable that the recorder be found under the wing?

Chronus: The terms used in the literature (NASA Langley Research Center vertical drop tests) for an airframe impact with water are often referred to as Hydrodynamic impact loading. In the past I have also come across the terms Hydrodynamic Ram effect or Hydraulic surge.
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Old 14th Jan 2015, 20:59
  #2035 (permalink)  
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Can anyone tell me if there has ever been a failure of the empenage in ANY Airbus Product? ;-)
American 587 is the most obvious with an in-flight loss of the VS, although in several instances (AF447, Perpignan) it was found floating alone after impact. Of course, that's not the full empennage...
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Old 14th Jan 2015, 21:15
  #2036 (permalink)  
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In this instance my money is on the in -flight loss of the empennage as a result of aerodynamic forces imposed upon it beyond its structural limititations
Basic stability means there is a downforce on the horizontal tailplane.

By definition therefore, if the horizontal tail is lost (as you say), the aircraft bunts - hard. Significant negative 'g'. In turn this would likely lead to a very high speed, near vertical impact. Not sure the wreckage supports that at all?

In fact, loss of tailplane can impose sufficient negative g that the wings then fail.
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Old 14th Jan 2015, 21:43
  #2037 (permalink)  
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Grrr re bj-eng

your 14th Jan 2015, 12:56 post
evidence of one of the data recorders being found under the wing
I suspect that report was made by someone strictly based on the shape of debris it was under. After all, the horizontal stabilizer is shaped very much like a wing and works the same way. To the casual observer or from a underwater photo of part of the structure, the differences would not be obvious without some sort of scale or other information.
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Old 14th Jan 2015, 21:48
  #2038 (permalink)  
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"Most comments on stalling are by those who have never stalled a swept wing jet at high altitude except once or twice in a simulator....."

Before we even get to attempting to practise stalling, in sims of dubious fidelity, how many airline crew posters on this forum have NEVER hand-flown their 'frame, at max mass for the max cruise altitude for that mass?

The "bungee cord" flight controls effect plus the momentum versus control effectiveness is indeed impressive, as is the "fright factor", in S&L controlled flight.

Yet I get the impression, due to some perceived prohibition on hand flying in RVSM airspace, that there are out there now, both F/Os and CAPTAINS who have never controlled their allocated craft in such conditions.

If this is indeed true, then we're all on our way to hell in a handcart if that is the xAAs and airline training departments' official policy.

Please, those of you out there still practising the art of airframe manager, prove to me that I'm wrong, and that EVERY current airline pilot has had the opportunity to hand fly a line aircraft full of SLF at max certified altitude/mass until he/she/it are fully aware of and comfortable with the handling characteristics.

If there are any exceptions to this fun experience, may I challenge whether that is a sensible state of affairs?

Which begs the question, per airframe kilometres/nautical miles, are we seeing a real increase in high-altitude LOC incidents/accidents since the introduction of RVSM and the perceived lack of practice in this environment, or is it just my (false) impression?
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Old 14th Jan 2015, 22:02
  #2039 (permalink)  
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More pictures there in the link.

Pictures & News Photos | Getty Images
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Old 14th Jan 2015, 22:05
  #2040 (permalink)  
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Photo citations

Would those posting photos please cite the source address? Thank you RetF4.

Tail location where discovered is no strong indication of impact location. Partial bouyancy, highest just after impact, is all that is required for drift. With any buoyancy at all the assembly would have been a vertical sail in the current. Some corroboration would be the current direction. Distance could be nothing more than rate of loss of buoyancy until seabed anchoring overcame current.

Last edited by Leightman 957; 14th Jan 2015 at 22:19. Reason: buoyancy rate
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