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Air Asia QZ8501 SUB To SIN Crash - Part 9 (by American 767 Jan 8 2015 in Civil Aviation)

Ben Soriano

Quoting maxpower1954 (Reply 221 from thread 9): Are you talking about the TWA 707 that was bombed over the Ionian Sea in September 1974? Because the sudden climb and out of control descent is very similar.

Partially true. Except the steep climb was caused by stretched control cables, as quoted from here.

Quote:'It was determined that the detonation of an explosive device in the aft cargo compartment buckled and damaged the cabin floor in such a manner that one or more of the elevator and rudder system control cables was stretched and, perhaps, broken. The resultant displacement of control surfaces caused a violent pitch up and yaw and made the aircraft uncontrollable.'

The 320 is a FBW (I think the first) AC and would have had no such issue.

[Edited 2015-01-12 14:48:20]

[Edited 2015-01-12 14:51:29]

Quoting LovesCoffee (Reply 1): Partially true. Except the steep climb was caused by stretched control cables, as quoted from here. Quote:'It was determined that the detonation of an explosive device in the aft cargo compartment buckled and damaged the cabin floor in such a manner that one or more of the elevator and rudder system control cables was stretched and, perhaps, broken. The resultant displacement of control surfaces caused a violent pitch up and yaw and made the aircraft uncontrollable.' The 320 is a FBW (I think the first) AC and would have had no such issue.

The A320 series has mechanical backup of the rudder and horizontal stabilizer trim, in case of total electrical failure. It allows the pilot to maintain aircraft control until electrical power is recovered. The mechanical back up system is direct control cables from the pedals to the rudder and from the trim wheel to the HS trim hydraulic actuators.

Russ Farris

Quoting maxpower1954 (Reply 2): The A320 series has mechanical backup of the rudder and horizontal stabilizer trim, in case of total electrical failure. It allows the pilot to maintain aircraft control until electrical power is recovered. The mechanical back up system is direct control cables from the pedals to the rudder and from the trim wheel to the HS trim hydraulic actuators.

Russ, thanks for the correction. This may be a silly question, but does the mechanical backup have the ability to override the FBW system? In that case, stretched/damaged cables might actually cause an issue. Was the mechanical backup provided because the 320 was the first FBW AC and the technology, although thoroughly tested, was unproven in day to day operations?

[Edited 2015-01-12 15:47:53]

Quoting maxpower1954 (Reply 2): The A320 series has mechanical backup of the rudder and horizontal stabilizer trim, in case of total electrical failure. It allows the pilot to maintain aircraft control until electrical power is recovered. The mechanical back up system is direct control cables from the pedals to the rudder and from the trim wheel to the HS trim hydraulic actuators.

Thanks for that info - I didn't know the extent of the mechanical backup system.

Are their any commercial FBW aircraft that do not have the said mechanical backups?

Quoting LovesCoffee (Reply 3): This may be a silly question

Quoting maxpower1954 (Reply 2):

My bad - brain fart. My reading comprehension failed when I read your reply. Sorry.   

No problem LovesCoffee! But yes, I certainly think it's possible a massive disruption in the fuselage could cause the back up cables to move the control surfaces violently. Since they have found the FDR the answers should come fairly soon.

I'm not sure about backup systems on other FBW aircraft, the A320 is the only one I've flown.

Russ Farris

Quoting 777Jet (Reply 4): Are their any commercial FBW aircraft that do not have the said mechanical backups?

If memory servies the 380 does not have any mechanical backup. The manufacturer must then demonstrate equivalent safety. In other words the "non-mechanical backup" must be as safe a solution as a mechanical one.

Just read on news, Cockpit voice recorder is also retrieved.

Now we wait on news of the data readouts ...

Quoting litz (Reply 9): Now we wait

No we don't! We can create & debunk a half-dozen unfounded theories before they get those boxes read!  

I can consider six impossible things before breakfast!

It was said one, or both, of the recorders were being pinned down by airplane debris, which were originally said to be fuselage parts, then wing and/or engine parts. I've looked everywhere and can find no pictures of any of what was said to be covering these boxes. I can't even find a news article that goes into anything but "recorders found!", and now recovered. So what was it that was said to be 10m x 4m x 1.2m, and how was it moved/lifted/made to go POOF allowing the divers to finally retrieve the boxes?

Quoting md80fanatic (Reply 12): So what was it that was said to be 10m x 4m x 1.2m, and how was it moved/lifted/made to go POOF allowing the divers to finally retrieve the boxes?

Under water you can use balloons attach them to say, wreckage fill it with compressed air from the diver's oxygen bottles and then lift it out of the way. Sort of like an under water crane. They used such balloons to lift the vertical stabilizer to the surface.

Quoting md80fanatic (Reply 12): So what was it that was said to be 10m x 4m x 1.2m

A portion of one wing.

Quoting md80fanatic (Reply 12): I can't even find a news article that goes into anything but "recorders found!"

Google News is your friend: http://www.thejakartapost.com/news/2...e-2nd-black-box-airasia-crash.html

http://mg.co.za/article/2015-01-13-d...ver-airasia-cockpit-voice-recorder

Now we have unconfirmed reports that the fuselage has been found:

http://sputniknews.com/asia/20150113/1016827075.html

3km away from the flight recorders and tail section, if accurate. That would be... odd.

[Edited 2015-01-13 00:49:42]

DW has a mpa of the debris field:

http://www.dw.de/divers-in-indonesia...-cockpit-voice-recorder/a-18186925

Not sure why I get a 403 forbidden uploading images here...

A link to another map of the debris field: http://mobile.twitter.com/JackBoard/status/554831332249858048/photo/1

Second black box/cockpit recorder found



https://twitter.com/JackBoard

[Edited 2015-01-13 03:11:49]

Quoting spacecadet (Reply 14): 3km away from the flight recorders and tail section, if accurate. That would be... odd.

If accurate, it would also be helpful for the families.

Okay, thank you I suppose, I just thought there'd be more by now than a truly lame "map" (have they never heard of zoom?). Still a great deal of obfuscation going on and it seems to me that one of the most important things still unfound in this accident is absolute truth.

P.S. I truly didn't expect to see a slightly dirty but otherwise pristine CVR, after seeing what became of the part of the plane it was mounted in. The only part of those things that are G-shock certified is the large cylindrical section containing the memory. Usually the rest of the recorder shows sharp deceleration effects.   

Quoting spacecadet (Reply 14): 3km away from the flight recorders and tail section, if accurate. That would be... odd.

and 3 km from at least a large part of a wing, the part under which the boxes were found.
Yes, odd, for the moment at least.

Quoting lancelot07 (Reply 20): and 3 km from at least a large part of a wing, the part under which the boxes were found. Yes, odd, for the moment at least.

Reports from the field are trickling in... There is means to guarantee that the following make sense or accurate. This is a speculation warning.

From the description I am getting it appears that the horizontal stabilizer had separated from the rear fuselage, which separated from the rest of the aircraft, at around FL220 (where the recorded ADSB altitude is only GEO alt, and no more barometric). From the description of the SAR team, it is unclear if the FDR was found on the sea floor below the horizontal stabilizer or the aircraft wing.

1 FA found strapped to his seat, indicates that those onboard were anticipating something.

---
The above may be obvious to some already, and this news from 'inside'... gets me baffled once more...

OK... back to the media frenzy for me... *trying to keep my sanity*

Quoting mandala499 (Reply 21): speculation warning

Thank you, Mandala499, for this insight. If it's true the HS separated from the rear fuselage which separated from the rest of the aircraft at FL220, then that's huge. The FA having been found strapped to his seat is telling.

If what you speculate is true, that's quite an inflight breakup.  

Quoting mandala499 (Reply 21): 1 FA found strapped to his seat, indicates that those onboard were anticipating something.

Could he/she just have been anticipating turbulence?

It still sounds like in-flight upset of some sort is the most likely culprit, with overstress during the descent possibly leading to breakup before the plane hit the water.

If that's what happened I guess this wasn't just a simple stall like AF447 as in that kind of a flight condition there shouldn't be high enough forces to damage the aircraft so badly...

I wonder if some extreme weather phenomenon alone could have caused the in flight breakup.

Quoting md80fanatic (Reply 19): Still a great deal of obfuscation going on and it seems to me that one of the most important things still unfound in this accident is absolute truth.

It's only been 16 days.

For comparison, the ATSB report on QF32, which occurred on November 4, 2010, was released almost 3 years later on June 27, 2013, and that was an aircraft that was fully available to investigators at SIN from the day of the accident.

Quoting mandala499 (Reply 21):

Thanks Mandala ! Your speculation fits the few but growing number of facts.
Maybe the tail was overloaded while trying to recover from the dive you mentioned in an earlier thread.

Wouldn't the FAs buckle up in case of expected turbulances ?

Quoting mandala499 (Reply 21):

Thanks for reporting this.

Quoting spacecadet (Reply 23): It still sounds like in-flight upset of some sort is the most likely culprit, with overstress during the descent possibly leading to breakup before the plane hit the water.

That does sound plausible, especially given Pihero's comments about the descent angles in previous sections.

Also, the fuselage is reportedly not by the wings: http://www.ibtimes.com/airasia-fligh...-refuting-reports-mentions-1781730

This is showing some eery similarities to NW705, hopefully the FDR will clear this up in the next few weeks.

Quoting md80fanatic (Reply 19): Still a great deal of obfuscation going on and it seems to me that one of the most important things still unfound in this accident is absolute truth.

The obfuscation by the SAR team isn't helping. They, and the military brass seems to be seeking glory with every single discovery. Thankfully, they are not the ones doing the investigation, and sources from inside the search team has indicated that the locations reported are so far accurate.

Quoting western727 (Reply 22): If what you speculate is true, that's quite an inflight breakup.

I don't think we've seen something like this for a long while...

Quoting pvjin (Reply 24): If that's what happened I guess this wasn't just a simple stall like AF447 as in that kind of a flight condition there shouldn't be high enough forces to damage the aircraft so badly...

Well, -20000fpm, and the last recorded valid barometric info (I just received the info) on the ADS-B, was at FL235, with -15,681.25fpm, at the beginning of a tight left turn.
Seems that the load factor protection of the FBW had failed... the question is, what caused the failure.

Fwiw, in a "typical" overload condition with a postive G pull recovery from a dive, the horizontal stab will fail in a downward direction. The rest of the aircraft will subsequently pitch down, with the wings also failing in a downward direction. This is only a simplistic generalization, which may or may not apply in this case. What got the aircraft to this undesirable state in the first place is probably the more important question.

My hypothesis (based on little to no real information) from a previous thread still stands. An overspeed condition induced by penetrating a thunderstorm cell, a subsequent pitch up to reduce speed, and then a spin due to aircraft damage of some sort.

Quoting mandala499 (Reply 21): 1 FA found strapped to his seat, indicates that those onboard were anticipating something.

Yeah, anticipating turbulence while flying through a line of thunder storms....

Quoting mandala499 (Reply 28): Seems that the load factor protection of the FBW had failed

Does this normally degrade with degraded flight control law (normal to alternate to etc.) or is it supposed to always be present?

Quoting mandala499 (Reply 21): *trying to keep my sanity*

Hang in there. 

[Edited 2015-01-13 10:31:10]

Quoting whiteguy (Reply 30): Yeah, anticipating turbulence while flying through a line of thunder storms....

Obviously...  

Quoting hivue (Reply 31): Does this normally degrade with degraded flight control law (normal to alternate to etc.) or is it supposed to always be present?

If it goes to ALT with reduced protection (load factor protection available), the icing argument, makes sense, but doesn't explain the breakup...
If it goes to ALT with reduced protection then go into an upset, this needs opening the books (which I can't do effectively at the moment).

Quoting hivue (Reply 31): Hang in there.

The sad thing is the minister of transportation is dishing out silly and reactive policies at the moment which can kill the industry... and I (with a couple of other people) would have to face him off on national TV in 18 hours... wish me luck!

Quoting mandala499 (Reply 32): The sad thing is the minister of transportation is dishing out silly and reactive policies at the moment which can kill the industry... and I (with a couple of other people) would have to face him off on national TV in 18 hours... wish me luck!

Thanks for all of the info Mandala and good luck with him. If you do not mind me asking as I have not either been around long enough or noticed in the past, but what is your profession?

Quoting western727 (Reply 22): If it's true the HS separated from the rear fuselage which separated from the rest of the aircraft at FL220, then that's huge.

It certainly is.

Quoting mandala499 (Reply 32): wish me luck!

Good luck.  

Thanks for keeping us informed.   

Having followed the thread and the news for the last two weeks, I think it has now become apparent that the aircraft did indeed break up at circa FL 235.
There was a link provided to a presentation of stall testing that was joint Airbus and Boeing, it was 90 minutes but very informative, particularly about stalls at high Mach and AoA.
What particularly intrigued me was some of the detail. Stalls tests are done in good weather and the plane must be in level flight. In this configuration you would be expected to lose 5-7000 feet.
He did talk about a stall in a turn and if I remember correctly felt that it would be hard to predict the outcome and more instrumentation would be required to even attempt a test.
That got me thinking as the very early data Mandala gave us was that the aircraft was in a left turn throughout until right near the end.
So my thoughts turned to a high Mach stall in a left turn in poor weather conditions, surely you would have to sacrifice more height than the tests trying to overcome the stall and gain control in difficult conditions.
Perhaps in trying to gain control that over stressed the aircraft and it broke apart as that surely seems to be the case.

One question I really want know is what started all this, hopefully some info will come out soon that adds pieces to this complex jigsaw of information.

I am not saying this is what happened just some ramblings what might fit with some of the clues based on the info we have.

Quoting lowbank (Reply 35): That got me thinking as the very early data Mandala gave us was that the aircraft was in a left turn throughout until right near the end.

I have seen the data and there was a wide left 180 (with a stall in the middle) followed by... a tight left orbit before the data stopped.

It sounds horrendous and I just hope that the g-forces involved were such that it was over quick for them. I have to admit that I enjoy terbulance in a Boeing more than in an Airbus!

One thing I've noticed is both recorders were recovered with their mounting brackets intact, as well as surrounding framework ... to me, says two things ...

1) pretty good level of disintegration underneath the section of tail we saw recovered
2) that level of disintegration was enough to shatter the structures, but not enough to pulverize it.

Quoting mandala499 (Reply 32): The sad thing is the minister of transportation is dishing out silly and reactive policies at the moment which can kill the industry... and I (with a couple of other people) would have to face him off on national TV in 18 hours... wish me luck!

Heck! We're all relying on you to get thru' that ordeal with your sanity intact, to keep on keeping us informed...
I'm crossing everything.

Nb. The BBC earlier reported (parts of) the fuselage being 1.5km from the tail debris; has that now been confirmed as 3km?

Riv'

Quoting hivue (Reply 31): Quoting mandala499 (Reply 28):Seems that the load factor protection of the FBW had failed Does this normally degrade with degraded flight control law (normal to alternate to etc.) or is it supposed to always be present?

If I am reading this correctly (and if it's correct information):

http://www.airbusdriver.net/airbus_fltlaws.htm

load factor protection is normally available in every flight control law but Direct. (The site doesn't say whether this info applies to all AB FBW models.)

Quoting hivue (Reply 40): load factor protection is normally available in every flight control law but Direct.

Yeah, this is from wiki:

Direct law

Direct law (DIR) introduces a direct stick-to-control surfaces relationship:[4] control surface motion is directly related to the sidestick and rudder pedal motion.[1] The trimmable horizontal stabilizer can only be controlled by the manual trim wheel. All protections are lost, but the maximum deflection of the elevators is changed as a function of the aircraft current centre of gravity.[citation needed]

DIR is entered if there is failure of three inertial reference units or the primary flight computers, faults in two elevators, flame-out in two engines (on a two-engine aircraft) or when the captain's primary flight computer is inoperable.[4]

Hey, Buddy !
These new pieces of info don't gel with what had transpired before, :
1/- The only way the SAR team could say that there was a break-up at around 22 000 ft is that they have an accurate primary radar ( military) that detected it. It's never been said before : We just had a rather crummy pic of a radar screen without any other info except GS and VS.

Quoting mandala499 (Reply 21): I am getting it appears that the horizontal stabilizer had separated from the rear fuselage...

Quoting mandala499 (Reply 21): ... which separated from the rest of the aircraft, at around FL220

So if I understand correctly, they detected three separate pieces falling down on their own , right ?
You- or they - are saying either too much or not enough : Did they see more pieces or just the three ?
The reason is that the left turn, with or without the whole empennage is puzzling : Bar a - another - drastic structural failure like loss of ailerons / slat(s / flaps on the left wing, the only possibility is a free-falling left engine.

Quoting mandala499 (Reply 28): -20000fpm, and the last recorded valid barometric info (I just received the info) on the ADS-B, was at FL235, with -15,681.25fpm, at the beginning of a tight left turn.

2/- We already discussed the pattern of that descent - for lack of another word - and we've agreed, haven't we ? - that it looked more like a falling leaf type of descent than a straight high speed dive.

Quoting mandala499 (Reply 32): If it goes to ALT with reduced protection ...If it goes to ALT with reduced protection then go into an upset, this needs opening the books

3/- Why did it go to ALT in the first place ?
The initial climb to FL363 gave just a VS of 8 600 ft/mi, equivalent to a change of trajectory of just 11°, let's say less than 15°, which is far from the trigger pitch angle of 50° nose up for the abnormal / ALT without protection law.
It doesn't make sense at all.

Quoting mandala499 (Reply 36): I have seen the data and there was a wide left 180 (with a stall in the middle) followed by... a tight left orbit before the data stopped.

4/- Here again it doesn't gel with the infos : a tightening of the turn would be logically subsequent to - yet another - break-up, this time of the left wing

5/- the scattering of the wreckage so far doesn't seem to be indicating so many structural failures.

6/- I've already indicated in a previous post that the physics of the influence of an updraft are from a change in the *apparent* AoA, due to the combination of horizontal airstream and the vertical updraft vectors : It is in reality the change in the lift coefficient that brings the load factor. It would need a massive updraft to cause a structural failure, which I do not believe, considering all the weather data in our possession.

7/- finally, one has to make a - BIG ! - difference between g-load protection of the flight controls and the structural limit loads on the airplane structure, based on the TOW : deformation at 3.75 G plus a ratio of the aircraft actual weight - circa 60 tons - vs some 80 tons --> another factor of 4/3 which brings the integrity limit to 5 g.

Yes, still baffling.

Quoting hivue (Reply 40): If I am reading this correctly (and if it's correct information): http://www.airbusdriver.net/airbus_fltlaws.htm load factor protection is normally available in every flight control law but Direct. (The site doesn't say whether this info applies to all AB FBW models.)

You're correct... but add mech back up.

Mechanical law

In the mechanical law back-up mode, pitch is controlled by the mechanical trim system and lateral direction is controlled by the rudder pedals operating the rudder mechanically.[1]

Yes, forgot that A320 has that.

In the Aeroflot Flight 593 crash the g-forces that the high speed, high altitude stall produced were so great that the Captain could not reach the controls even though he was sat in his seat in front of the yoke.

This could be an explanation for no mayday call by the Air Asia pilots as the button for the mic is on the side stick.

Quoting mandala499 (Reply 36): I have seen the data and there was a wide left 180 (with a stall in the middle) followed by... a tight left orbit before the data stopped.

I am a bit confused as to whether a stall in a turn has been verified. Regardless, are we talking about the same physics that applied to this B52?:

http://en.wikipedia.org/wiki/1994_Fairchild_Air_Force_Base_B-52_crash

Quoting CF-CPI (Reply 46): I am a bit confused as to whether a stall in a turn has been verified

As far as *I* know, nothing has been verified....yet.

Mandala Thanks for the info and good luck !!!

One question for the pro´s here, is it possible to over stress the aircraft while in normal law? Is it possible to do it on ALT mode?

The seated FA means they had prepared for turbulence or were in the midst of it, and then something happened, they did not reduce the speed of penetration, so maybe it did not look as bad, they prepared the cabin and then the unexpected happened *what ever that may be.

TRB

Quoting mandala499 (Reply 21): From the description I am getting it appears that the horizontal stabilizer had separated from the rear fuselage, which separated from the rest of the aircraft, at around FL220 (where the recorded ADSB altitude is only GEO alt, and no more barometric). From the description of the SAR team, it is unclear if the FDR was found on the sea floor below the horizontal stabilizer or the aircraft wing.

I am far from convinced of this, I have given some details on the ADS-B data on previous threads.

The damage to interior components, the concertina fold of recovered overhead cabin interior, damage to seat legs, and the recovered doors from catering carts to me point to excessive vertical deceleration.

Been lots of accidents in transport category aircraft where the initial contact with ground or water has caused the aft fuselage to fail. We know the tail floats, the XL Airways, Armavia, and Gulf Air crashes all have the tail floating after impact.

Quoting mandala499 (Reply 21): 1 FA found strapped to his seat, indicates that those onboard were anticipating something.

Standard practice for turbulence.



[Edited 2015-01-13 14:55:10]