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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 18th Jan 2015, 01:51
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If they have a good idea of the cause but do not feel it urgent to release any information about it, can it be considered that the likely cause is something that does not pose an immediate risk to the operation of other aircraft of the type?
That is a reasonable inference.
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Old 18th Jan 2015, 02:16
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Warning reference to QZ 8501 autopsies below.





It has been reported today that autopsies have QZ 8501 passengers revealed impact injuries such as broken legs, but no burns. Source:

Divers sent to investigate pings from crashed AirAsia flight QZ8501 (apologies for mobile link).

I recall that AF447 pax also suffered broken legs from the upward impact of their seats.
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Old 18th Jan 2015, 09:39
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Unlike the AF crash i suspect this airbus hit the sea with some forward speed, cartwheeled and came apart.

I further suspect that this was a weather induced loss of control and at some stage an attempt at recovery was made, but the vertical rate of descent and space between cloud base and hard deck was insufficient

I very much doubt the weather was directly responsible the break up, but if they ended up in a viscous updraft and pitched down and cut the thrust it would be very easy to loose it and recovery in cloud with no visual reference, much turbulence and all manner of warnings going off......there but for the grace of god
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Old 18th Jan 2015, 11:12
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Vertical speed of about 10,000fpm is about 100kts straight down so coupled with 100kts forward it will not be pretty on hitting the ocean!
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Old 18th Jan 2015, 14:34
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Future search scenario's

The majority of posters appear to 'vote' for most likely scenario(s) (and versions of those) going like: ‘... an event or upset, leading to a (low speed) stall, no recognition of that stall, or impossible or too late to recover from that stall, and finally the plane hitting the water at an almost even ‘keel’ ...’

I have read interesting comments on other scenario’s though. So I hope those interested in other scenario’s will share comments or suggestions on the following ‘theoretical scenario’.

What would the damage look like, if an almost intact A320 would dive almost straight in?

Keeping in mind the special circumstance in the 8501 case, being that the water is only 28-30m deep. If you take the fuselage length of 37.50 m and subtract the waterdepth of say 29.00 m you get 8.5 m. Now assume that the nose reaches the seafloor. The tail part that ‘sticks out’ is about 8 m. That would roughly be around frame 68-70. Ergo, around the aft strong frame of the aft passenger door?

The exact angle of entry into the water will then determine how the tail section breaks off. Following the earlier ‘production break’ discussion, that could be either just in front, or just behind the aft passenger door. It could also provide a (the section moving ...forward, backward or sideways) break-up scenario for the components of the tail section.

It is possible to think of a path now, that leaves the vertical tail rather undamaged( we can try to match that with the visible fractures – of course trying to exclude damage caused by pulling the tail on board Crest Onyx). And losing the APU and the THS. Where perhaps (see earlier posted scenario’s) the tail section with tail floated before it became water logged, anchored, and overturned. But now the THS also floated before becoming water logged. And therefore it is possible it will be found a bit further away.

I did some tower diving in the past from 10-12 m. When you get in under even a small angle with the vertical, your spine is bent, quite a force, so would fuselage show a kind of water dampened whip 'reflex'. Always very complex to make dynamic stress calculations ... but ...

Answers to these questions might be of some assistence in future searches. Till this accident it seemed most likely, if anything was found on the surface, find vertical tail or rudder first. Would it help to give SAR crews a description of most probably objects to look for. Also helping to separate ocean garbage from aircraft components and fragments.
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Old 18th Jan 2015, 15:04
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@ A0283...

Not an expert but if as you suggest the aircraft "went straight in" then one would have to assume it is not in a "stalled" condition, thus probably hitting/entering the water at a substantial speed.

In this case it would most likely break apart in many small pieces upon hitting the water almost like hitting solid ground.

Last edited by Jet Jockey A4; 18th Jan 2015 at 16:07.
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Old 18th Jan 2015, 15:23
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@A0283
Answers to these questions might be of some assistence in future searches. Till this accident it seemed most likely, if anything was found on the surface, find vertical tail or rudder first. Would it help to give SAR crews a description of most probably objects to look for. Also helping to separate ocean garbage from aircraft components and fragments.
A vertical or close to dive into water would cause considerable damage to the nose of the aircraft and stresses would show that the aircraft hit something nose first.
Passenger injuries would show severe seatbelt injuries and seats would be broken away from the floor and compressed toward the front of the fuselage. I am not sure that pax would show the same broken legs that appear to be apparent in this case. There would also be more detritus from inside the fuselage.

[Theoretical Scenario]

The concertinering of the fuselage seems to show that the aircraft hit the sea surface belly first perhaps with a slight nose down to provide the hydraulic disconnection of the empenage at the pressure bulkhead. As pointed out several times the break line of the tail is not consistent so there may have been a one wing low and turning vector.
So as a theoretical scenario, loss of control, stall into a relatively flat spin. This would also fit with the descent rate, a dive would have been considerably faster more than 30,000 fpm.
From Stall/Spin " if the impact occurs nose down, at a high rate of descent which is typical of stall/spin scenarios, the G forces tend to be much higher, the aircraft does not slide much and there are resulting fatalities."

[/Theoretical Scenario]
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Old 18th Jan 2015, 15:28
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Originally Posted by A0283
What would the damage look like, if an almost intact A320 would dive almost straight in?
Millions of tiny bits'n pieces....

Whatever remained would show orthogonal/circumferantial crumple lines instead of longitudinal.

This one here pretty surely hit flat (with maybe a touch of bank angle). If anything rather a tad Nose Up rather than Nose Down. Especially the seat structures showed signs of vertical and pratically no visible longitudinal bending. The same with the folds in the fuselage/tail skin
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Old 18th Jan 2015, 16:09
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An interesting news article:

AirAsia flight QZ8501: Crash highlights perils of South-east Asia's crowded skies - South-east Asia News & Top Stories - The Straits Times
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Old 18th Jan 2015, 16:36
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Ask for a higher level on the Atlantic you will get a similar 'UNABLE DUE TRAFFIC' response. Then the article segways from that into apparently trying to blame ATC for the incident. Looking at the surveillance pictures showing the amount of traffic around 8501 - it takes a fair amount of hyperbole to call the airspace 'busy'.

As pointed out multiple times ATC has to meet separation standards that are enforced (often by automation 'snitch'ing to supervisors) Unless the flight crew states this is an urgent request to avoid weather, then the request will be treated as routine, so you will need to standby while the controller coordinates the level change with other sectors and the next air traffic unit. As I have said before 'communicate' in time can reduce pressure on 'aviate' later. If concerned take the weather avoidance then tell ATC what you are doing. Ideally do it into a space in the TCAS traffic picture . You have to balance the risk of the weather against the risk of loss of separation.
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Old 18th Jan 2015, 17:21
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I've had the opportunity to investigate a military accident (dive into water @550 knots 50 degrees ND, and to see the wreckage first hand of a 250 knot fly into the water in (near) level flight. In addition, I had the opportunity to participate in almost the entire AF447 thread. QZ8501 was not a dive into the water. A high speed dive would shatter the aircraft into its component bits & pieces with the leading component pieces more highly fractured than the trailing components (due to deceleration).

From the damage observed so far, the aircraft entered the water at very low forward speed in a near level, slightly left wing down attitude. The major velocity component was downward. By comparing the damage observed with AF447 and with some of the events of the Perpignan A320 accident, there is one glaring difference. The vertical stabilizer remained attached to the fuselage structure until the tail was crushed from beneath. Instead, the skin forward of the VS shows a small section of fore and aft force induced compressive wrinkling in addition to the vertical compressive force induced folding along the stringers lower down. Below that, the structure was shattered and is missing with damage extending further up the port side than the starboard side.

In other words, it hit the water slightly left wing down, with minimal horizontal velocity, in a flat attitude with relatively high vertical velocity. I'm open to differing opinions, but there is only one way I know of to put an aircraft into the water in this way, and that is a flat spin (as differentiated from a nose down spin).

Transport aircraft are not intentionally deeply stalled during flight testing nor are they spin tested let alone training pilots how to recover from a full stall or a spin. For this reason, if a spin is entered at altitude, it is likely to continue. Often flat spins in jets are not recoverable events and are dependent on the specific aircraft characteristics (mass distribution-types of control surfaces, general planform etc.)

I know some of you fly aerobatics including spins however, flat spins in larger aircraft have an additional hazard in that the crew is located far from the center of rotation, and thus even a modest rate of rotation in a spin creates disabling eyeballs out g effects. For example, in the F-14 front seat, you had to lock your shoulder harness at the beginning of the event or you would be folded over in your seat and unable to eject. I don't think A320 pilots would be particularly effective in recovering from a spin if they found themselves involuntarily staring at their kneecaps.

Assuming that the foregoing analysis is in the ball park, it will be very interesting to learn how this departure from controlled flight developed.
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Old 18th Jan 2015, 17:52
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@Machinbird: Your comments on flat spin are interesting, and it is possible to put some figures on the g load that a pilot would encounter using some basic physics. The acceleration during circular motion is 4 Pi squared times the radius for the motion times the square of the number of rotations per second. If the pilots are about 15 metres from the centre of rotation during a flat spin, and the aircraft was rotating about a vertical axis taking 3 seconds per rotation which is not unrealistic in this scenario then this gives a radial acceleration which after normalising to 10 m/s/s for 1G, leads to a g load in a direction facing the front of the aircraft (eyeballs out as you said), of over 6G. Any faster rotation than 3 seconds per turn would give even higher g loads which would likely render the pilot unable to react to the controls as you have detailed in your post. This calculation confirms your analysis if the aircraft did end up in a flat spin, despite this being a significant departure from the normal flight envelope. Nevertheless the FDR data should ultimately provide evidence as to whether the aircraft did end up in a spin following the event sequence at the time of loss of contact.
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Old 18th Jan 2015, 18:03
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With a few minutes to spare after an LPC, the instructor demonstrated how easy it was to spin an a320. The spin was totally classic albeit with an astonomic RoD. Recovery was similarly straighforward. I think the loss of altitude was about 6000'.
I am in no way suggesting that in real life things would be so simple, but it was an interesting and reassuring experience.
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Old 18th Jan 2015, 18:09
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For those drawn to the fake CVR recording on Youtube that has been linked to at least once, please don't think it's genuine - it's very clearly not from an A320, and is probably a recording from a different incident.


There is no audible Bank Angle warning in an A320 afaik.
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Old 18th Jan 2015, 18:29
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Originally Posted by macdo
With a few minutes to spare after an LPC, the instructor demonstrated how easy it was to spin an a320. The spin was totally classic albeit with an astonomic RoD. Recovery was similarly straighforward. I think the loss of altitude was about 6000'.
I am in no way suggesting that in real life things would be so simple, but it was an interesting and reassuring experience.
Of course that was without the out-of-spin g forces which may have made things a little more interesting.
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Old 18th Jan 2015, 19:11
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Originally Posted by macdo
With a few minutes to spare after an LPC, the instructor demonstrated how easy it was to spin an a320. The spin was totally classic albeit with an astonomic RoD. Recovery was similarly straighforward. I think the loss of altitude was about 6000'.
I am in no way suggesting that in real life things would be so simple, but it was an interesting and reassuring experience.
As has been pointed out, there has been no spin testing of A320s (!) to provide data on which to base a simulation. The reason the simulation behaved in a "totally classic" manner will have been precisely because that was how it was programmed to behave, similarly the recovery. Any reassurance you gained was based on an educated guess, at best!
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Old 18th Jan 2015, 19:55
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There have been several references to the Ethiopean 767 crash. It appears some think this was a controlled ditching. It was a higher speed impact with the water while the crew was engaged in a ongoing struggle with the hijackers right up to the moment of impact. It was not a controlled ditching.
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Old 18th Jan 2015, 19:57
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Engines

What chance would engines have remaining attached in a 3 second period flat spin? Pylons don't appear to be made to tolerate many lateral g's.
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Old 18th Jan 2015, 19:58
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Further to Ian W's comment:

Please excuse my ignorance, but do we have any evidence at this stage of any 'concertinering' of the fuselage or of any injuries (post mortem) other than broken limbs ?? Perhaps I've missed some latest photographs ??
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Old 18th Jan 2015, 20:59
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A couple of things...

First, it's so good to see some of the real professionals and experts back posting after so many have been quiet since the halcyon days of pprune (the AF447 threads come to mind of course). You -- and long time ppruners -- know who you are.

Second, whatever the cause(s) of this accident, the aircraft did not "explode" or come apart at altitude. A transport category jet aircraft without tail surfaces does not / cannot impact the surface in a near flat or near horizontal attitude. It would impact (whatever surface) nose first and at a vey high rate of descent. Very few large intact pieces would remain.

Lastly, as others have said in rebuttal to negative comments (including some slurs) against the Indonesians, their SAR, their ATC, and their investigative agency: Those of us Bules (Bahasa for foreigners) who have worked with them and for them recently agree that painting them as inept and/or corrupt is simplistic and inaccurate. The level of professionalism and commitment to improvement over the past few years is clear and obvious to other governments, ICAO, international corporations and individual aviation experts.

Last edited by grizzled; 18th Jan 2015 at 21:23.
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