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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 25th Jan 2015, 15:15
  #2501 (permalink)  
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Does this look like the horizontal stabilizer being lifted out of the ocean, only to have it drop back in to the sea due to the rope snapping?

Refer to 19 seconds (0:19) in to the video.

(I know the caption says fuselage, but it looks more like the horizontal stabilizer to me)


Last edited by training wheels; 25th Jan 2015 at 15:34.
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Old 25th Jan 2015, 15:29
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Spotted some slats there, so more likely the wing-fuse centre section.
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Old 25th Jan 2015, 15:31
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I suppose the idea of preserving forensic evidence has been completely disposed of now? It might have been better to leave the item down there, as is, rather than roll it over the stern of that boat. I really can't see how this can be considered, in any way, proper handling of crash wreckage where the cause is still officially unknown.

There does appear to be, at least, a small portion of the left wing still attached. ???
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Old 25th Jan 2015, 15:43
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That's what it looks like. The horizontal stabilizer.
Things get heavy as they are pulled out of the water. That's why you need a net to pull a fish out of the water, without breaking your line, when you catch a big one.
It's a tough recovery, and I'm sure they have to improvise as best they can, as the weather probably limits their ability to have all the equipment they need at the right place at the right time. God bless 'em.
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Old 25th Jan 2015, 15:58
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So what happens at FL380 and 205KIAS/Mach 0.67 15deg nose up, if full thrust is applied and there is compressor stall on the left hand engine? You now have full thrust on the right engine and drag from the left engine.
I'm assuming you're not a pilot? Multi-engine aircraft are designed / certified such that above Vmca speed (which is lower than takeoff speed), there will be sufficient control authority even with the most critical engine out and the other engine set to full thrust. So at M0.67 losing an engine (by itself) should not cause a fatal accident.

Now, at high-angle nose up, if the airspeed decays rapidly while conversely the AoA increases rapidly (resulting in a stall), then a one-engine-out situation at that point becomes deadly.
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Old 25th Jan 2015, 15:59
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The chord appears to be quite a bit longer than A320 THS, so it must have been the fuselage piece.
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Old 25th Jan 2015, 16:15
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Overspeed protection

Could somebody explain to a simple engineer how an air temperature "spike" would cause the aircraft to go into an overspeed protection? I've seen this theory posited to explain an automatic pull-up, but I can't see why the aircraft would, either correctly or erroneously, "think" it was overspeeding.
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Old 25th Jan 2015, 16:23
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Originally Posted by peekay4
I'm assuming you're not a pilot? Multi-engine aircraft are designed / certified such that above Vmca speed (which is lower than takeoff speed), there will be sufficient control authority even with the most critical engine out and the other engine set to full thrust. So at M0.67 losing an engine (by itself) should not cause a fatal accident.

Now, at high-angle nose up, if the airspeed decays rapidly while conversely the AoA increases rapidly (resulting in a stall), then a one-engine-out situation at that point becomes deadly.
Yes I am aware of the certification of twins and that many of them will reduce maximum available power on a good engine in asymmetric etc.,

But you then go on to agree with what I proposed.

As you are so experienced with A-320 you will know what the minimum safe operating speed is at FL360+. Give the aircraft being 15deg nose up and M0.67/ 205KIAS and autopilot out in AoA law (assuming similar behavior to the quoted report) as you say going asymmetric with a compressor stall one side and full thrust the other could be deadly. It's not only drag - there will be pitch up forces from the live engine and pitch down from the stalled engine. You could also consider what the 'safe control authority' is up in 'coffin corner' at greatly reduced airspeed and what happens if someone is too hasty applying 'full' control authority.
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Old 25th Jan 2015, 16:25
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TAS = IAS x sqrt( ISA Density / actual density)

TAS will remain largely over short term (KE) if W/V is unaltered.

Alter OAT alters density (Boyle IIRC?) so requires altered IAS.

Overspeed limits are in IAS terms, so if IAS changes due delta Temp, you can go into an "overspeed".

At altitude, you will be M limited, but again this is Temp dependant.

Clear as mud
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Old 25th Jan 2015, 16:27
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Originally Posted by HeavyMetallist
Could somebody explain to a simple engineer how an air temperature "spike" would cause the aircraft to go into an overspeed protection? I've seen this theory posited to explain an automatic pull-up, but I can't see why the aircraft would, either correctly or erroneously, "think" it was overspeeding.
It is important in many aircraft to avoid stresses due to shockwaves forming on the aircraft surfaces due to approaching the speed of sound. The speed of sound is dependent on the air pressure _and_ the temperature see Mach Number

So a sudden change up in temperature can convince the automatics that the aircraft is too close to the speed of sound and damaging shockwaves may be forming on the airframe and control surfaces. The automatics then do their best to recover back to below the limiting Mach No. The quickest way to do that is to pull up.


Just as an addition- going too fast and getting shockwaves build on various surfaces can lead to other interesting effects such as control reversals which could lead to dangerous effects.

Last edited by Ian W; 25th Jan 2015 at 16:38. Reason: addition in italics
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Old 25th Jan 2015, 16:35
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Yes, it is a pat of the right wing and fuselage

@md80fanatic there is a YouTube video shown from the perspective of on the boat. Just before the cable snaps the wreckage is high enough where the letter "C" is visible. This would make the visible portion of what was brought up as the forward fuselage and part of the right wing. No windows were visible also no idea as to the portion below the water. They will be using a crane in their third attempt.

Last edited by FlyerBabe; 25th Jan 2015 at 16:43. Reason: spelling.
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Old 25th Jan 2015, 16:46
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Isn't a, the speed of sound pretty well proportional to the Sq. Root of Abs. Temp?
If so aircraft Mach No. would decrease if Temp suddenly increased?

Have I got my knickers in a twist or am I correct
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Old 25th Jan 2015, 16:56
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Exactly what I was thinking - an increase in OAT increases the speed of sound, so the aircraft would be even further away from a Mach limit than before. And IAS is dependent on pressure, not temperature, so there'd be no effect on an IAS limit. I'm struggling to see why the aircraft would see any increased airspeed to protect itself from.

Last edited by HeavyMetallist; 25th Jan 2015 at 17:03. Reason: Typo
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Old 25th Jan 2015, 17:37
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Climb authorization

RF4 at 2502: it has been stated many times that his increase in FlL request was denied. It's highly unlikely that he would initiate a unauthorized climb to move up to optimum .

And Lost in S at 2515: He had been cleared to FL340 but there was never a response to that clearance. That tells me they never heard it. It also tells me they did not respond because they were already too busy dealing with the problem that caused the aircraft to climb unintentionally.

It is wrong to simply assume that 8501 did not receive the climb authorization, based on lack of acknowledgment. The clearance may have been received, and pilots therefore may have known that a climb was then allowed, but THEN got busy and were not able to acknowledge. The time bits are small and important.
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Old 25th Jan 2015, 17:48
  #2515 (permalink)  
 
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Clearances not acknowledged...

...can be the case when a third party overtransmits on the frequency or breaks in, preventing a timely response. Which happens quite a lot in that area due to frequency congestion and poor radio manners.
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Old 25th Jan 2015, 18:00
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Lifting what - wing or ths

Very fuzzy video again ... in some recent (not only aero) investigations images were deliberately fuzzed ... wonder if the same is true here.

If they are using the Crest Onyx again. Crest has a beam (width) of 14m.

You might consider that in your analysis.
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Old 25th Jan 2015, 18:10
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Did the cargo break loose and move aft causing nose high attitude/high rate of climb?

I have not seen any discussion about the cargo possibly breaking loose due to extreme turbulence (once they entered the level 4 or 5 Thunderstorm) moving the cargo tail aft position causing a nose high attitude = increased rate of climb.
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Old 25th Jan 2015, 18:12
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@A0283 the YouTube video from the second attempt to raise the fuselage where you can see the letter "C" is from the Crest Onyx. I can't post the link but you can find it by Googling...AIR ASIA JATUH LAGI ! I also know of someone working on the recovery on the Crest.
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Old 25th Jan 2015, 18:25
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Video link

>@md80fanatic there is a YouTube video shown from the perspective of on the boat.

Video link please. I'm not finding it. I can't imagine there was any real confidence that given previous video of the fuselage that it could be raised intact as there was no apparent remaining structural integrity.

Also, all the short fuselage video I have seen is the same shot, showing the right wing generally in place, but the left wing is not merely by low visibility with a distended fuselage section where the wing could be expected. Is there any other video or photos that clearly show that the left wing is absent?

Given the buoyancy of the vertical stab, the tail could clearly have drifted some distance given the current strength. I have assumed for the present that the fdr/cvr would have been found close to the impact site if they were torn out on initial impact. I too am puzzled that the recorders were found "under the wing. I realize "the wing" could have been in initially misidentified, but the number of divers during the late fdr search and in proximity to the recovery of the fdr and cvr makes it less likely that the HStab would be mistaken for a wing. We had an initial plot of the debris field but I have not seen an update. The absence so far of the relative positions of the fdr "wing", center fuselage section, cockpit and any other major components is frustrating given the time since their discoveries. Any links to debris location plots would be appreciated.

RE BG47, has a cargo manifest been published?

Last edited by Leightman 957; 25th Jan 2015 at 18:26. Reason: cargo manifest
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Old 25th Jan 2015, 18:48
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Spotted some slats there, so more likely the wing-fuse centre section.
For sure, yes.
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