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bond007
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 5:31 pm

Quoting Brick (Reply 147):
If an aircraft banks steeply, the wing of the aircraft will block signals the to GPS antenna on the top of the fuselage and you'll lose GPS lock. Once you level out it can take some time for the GPS accuracy to come back. It's a common problem with aircraft that collect aerial photography or LiDAR data.

Bear in mind, since we are talking about whether the ADS-B GPS data is accurate, is that the accuracy/integrity of the data is known (and transmitted).

It would be highly improbable, except if there was an underlying software issue, that the GPS position data would be 'incorrect' ...i.e. an incorrect position was transmitted but the message data specified it was accurate.



Jimbo
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hivue
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 5:35 pm

Quoting therealswede (Reply 146):
Mandala hinted earlier that the rudder behaviour is being investigated, specifically from earlier flights.
Quoting FltAdmiralRitt (Reply 148):
Is it possible that the flight computer encountered combination of Flight Data sensor inputs that
confused it, and caused unexpected behavior from the controls. (obviously it would have to be
an undetected software glitch)

In these sorts of scenarios we likely would have already seen advisories to operators published by Airbus.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
Rivet42
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 5:43 pm

Quoting bond007 (Reply 150):
It would be highly improbable, except if there was an underlying software issue, that the GPS position data would be 'incorrect' ...i.e. an incorrect position was transmitted but the message data specified it was accurate.

Well, I wonder...
If one spends an hour or two tracking aircraft in FR24, it's not unknown for the plotted position to jump around a bit. I've never been able to determine whether that's due to the scanner receiving and decoding the data, the website, or the data itself. I live under the glide-slope for LHR 27R, with aircraft passing over my house at 3,500ft. Sometimes, the track on FR24 will be up to 1/2 mile 'off'. Not often, but it does happen. Very interested to know what may cause that.

Riv'
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dtw2hyd
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 5:54 pm

Quoting bond007 (Reply 150):
It would be highly improbable, except if there was an underlying software issue

Assuming there was no updraft, ignoring what was it designed for, can a A320 with 2xCFM56 engines carrying 160+ pax climb 12000 fpm?

Quoting bond007 (Reply 150):
that the GPS position data would be 'incorrect' ...i.e. an incorrect position was transmitted but the message data specified it was accurate.

There are possibilities where GPS approximates the location with higher margin of error, while it is tries to regain lock on satellites.

For the altitude discussion I think GPS is irrelevant, it appears barometric altitude is primary source to ADS-B, there could be secondary sources. Rules dictate both transponder and ADS-B has to use same source.
All posts are just opinions.
 
bond007
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 6:01 pm

Quoting Rivet42 (Reply 152):
If one spends an hour or two tracking aircraft in FR24, it's not unknown for the plotted position to jump around a bit. I've never been able to determine whether that's due to the scanner receiving and decoding the data, the website, or the data itself.

Presumably FR24 does not show any data relating to it's accuracy or integrity of the messages it decoded. AFAIK this information in transmitted in the message. I'm sure FR24 just strips out lat/lon, altitude, speed etc. and cares not so much about other data that would be very important for navigation purposes.

Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
flightsimer
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 6:14 pm

Quoting md80fanatic (Reply 91):
Look folks, if you insist of commenting on my post, why can't you engage your higher intellect first (not counting LTC8K6, he/she appears to have understood where I was going with it). For those who immediately see my moniker and think conspiracy ... well shame one you.   

I have never posted ANYTHING about AA191 on this thread, or other parts of this discussion relating to this accident. If you saw a post from "me" regarding it, you must have been dreaming it.   

Now then, back to thread ... Can you contemplate a force (from an acceleration downward) being placed on the engine pylon? The image I posted shows it in full detail (can't be argued against, it's a fact). Under many more g's (which a spin would generate) .... IMHO the engines would NOT stay attached.

Is that good enough?
Quoting md80fanatic (Reply 94):
Seriously?

That is the post (my first) you said was my second on the topic regarding AA191. Sorry, I'm trying to be patient but you guys/gals make it quite the challenge. Maybe it's a language thing? [Edited 2015-01-20 16:51:55]


Your credibility on this subject is completely gone in my view as you do not know what you have said. If you and everyone else would refer to Part 6 and your reply #168...

Air Asia QZ8501 SUB To SIN Crash - Part 6 (by jetblueguy22 Dec 31 2014 in Civil Aviation)#1

Quoting md80fanatic (Reply 93):
Can you actually perceive 3D? I ask because if you look close to the shading on the nacelle (literally a tapered cylinder) you can easily see that the engine is canted along the axis of my red line, based upon the shadow the sun is casting on it (clue ... compared shaded side to that of the fuselage ... which the engine is supposed to be parallel with). Again, I never said number 2 separated, that was you my friend.

The cross section of the DC-10's engine is not a tapered cylinder, It has a constantly varying cross section. I believe the accessories are located at the bottom of the engine, and when the plane is banked at the 100+ degree angle it was when that photo was taken, it makes it look like the engine outline points outwards in addition to the affects of the sunlight and its reflections.

Quoting LTC8K6 (Reply 105):

http://media.trb.com/media/photo/2011-08/64196703.jpg

AA191's starboard engine is clearly not crooked at all, imo.

This version of the photo not only shows that, it also shows the glare that causes the illusion.

Exactly!

Quoting md80fanatic (Reply 115):

Well, reading your "reasoned" responses leaves me with one wholehearted request ... YOU fly the planes and I will do the physics ... okay?

Please do not have any part of any physics which involve any aircraft I may fly as you clearly do not understand them.

Quoting md80fanatic (Reply 114):

This science is not up for debate, it's well proven. It was instrumental in mankind's landing on the moon and beyond

the science yes, your incorrect interpretations, no.

Quoting md80fanatic (Reply 116):
B777fan, how can you say, for certain that it would have separated prior to impact? Was it you who designed the DC-10 pylon? Do you know the forces expected in such a scenario? Are you keenly aware of the torsional strength of the alloy used, much less the actual makeup of the alloy? NO ... if ypu don't mind me saying.

i have history of structural metallurgy, and this is a textbook case. The photo is no illusion ... Forces in this direction were never anticipated, and thus not designed to resist.



And you did design the pylon?

You claim the metal of the pylon's two attachment points would not be strong enough to withstand the gravity, aerodynamic force or whatever it was you were trying to say, with the plane in the slip that it was, but yet it took EIGHT weeks for the crack in the left engines mount to finally degrade the metal to the point where it would fail.
Commercial / Airline Pilot
 
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par13del
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 6:23 pm

Quoting nm2582 (Reply 120):
At the very least, I hope there are no implications for aviation safety for other operators of the type worldwide.
Quoting hivue (Reply 151):
In these sorts of scenarios we likely would have already seen advisories to operators published by Airbus.

...and cause a panic? I'm inclined to believe that in the times that we live in today, they will run things by the OEM's involved before releasing info to the public which may create an irrational fear of flying.
We know that A320 a/c are flying daily with no accidents, just as we knew A330's with the suspect pitot tubes were flying daily with no issue, without researching all the past threads, I could easily imagine a bulletin being put out reminding operator of the recovery procedures to be performed if the pitots failed, indeed, during the numerous AF threads the DL flight and its crew performance was referenced, one could even ask if all the pitots have been changed out of the A330's in service?

Based on what they are saying about weather and it not being like AF447, one starts to think they are strictly looking at human factors.
 
tailskid
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 7:30 pm

RE; post #123
The "roll" which would encounter gyroscopic resistance is not a roll around the horizontal centerline of the plane; but rather a roll around the vertical centerline of the aircraft (the kind of "roll" which would be opposed by the vertical stabilizer.) 191 appears to be encountering that type of "roll" at the time of the picture.

From my POV, the ones who are not explaining themselves well enough are the people who attribute the angle of the #3 engine to glimmering sunlight or whatever. This reminds me of W. C. Fields - "are you going to believe your own eyes or are you going to believe what I'm telling you??"

Also, even if Engine #3 completely detached itself it would still be spinning (internally) "at high speed" when it made its touchdown.

I find this debate very interesting.

[Edited 2015-01-21 11:33:29]
 
tailskid
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 7:47 pm

Quoting mandala499 (Reply 141):
now the FOQA CF card is being looked for.

Is this data stored in non-volatile memory?
 
Rivet42
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 8:33 pm

Quoting flightsimer (Reply 155):
Please do not have any part of any physics which involve any aircraft I may fly as you clearly do not understand them.

  
I travel, therefore I am.
 
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gennadius
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 8:58 pm

Quoting tailskid (Reply 157):
Also, even if Engine #3 completely detached itself it would still be spinning (internally) "at high speed" when it made its touchdown.

Since this is already severely derailed from topic, I'll chime in. I think that the repeated point that many people have been trying to make here is that the No. 3 engine would not have had its data recorded (takeoff thrust, high rpm) until impact, just like all the parameters of the No. 2 engine were, if it had actually detached. Additionally, one would think that the investigation would have noted a small detail like a second engine detaching prematurely. Since it didn't, and since the data was recorded, and since the only "evidence" of this detachment that was presented was a coarse grained photograph that has been refuted in multiple ways, I suggest that we let this issue lie and let the thread get back on track.

[Edited 2015-01-21 12:58:50]
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675kts
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 9:07 pm

As interesting (and sometimes amusing) as all this is to read, does anybody have anything to bring this thread back on topic? I note a few reports of large flotation pontoons being prepared to raise the largest fuselage part yet no further underwater images of either the fuselage or cockpit section as yet.
 
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Aquila3
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 9:11 pm

Quoting tailskid (Reply 158):
s this data stored in non-volatile memory?

If it is a CF card, that is particular form of card that contains FLASH memory, that is, in a broad sense, non-volatile.
Did I miss anything or am I stating the obvious?
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LTC8K6
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 9:22 pm

Quoting Aquila3 (Reply 162):
FLASH memory, that is, in a broad sense, non-volatile

If you wanna call it that...  
 
Kaiarahi
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 9:30 pm

Regarding the continuous left turn, and reversion to alternate law, there were reports a number of years ago of FAC (flight augmentation computer) faults on A320s resulting in "runaway" rudder trim. From Youtube (not "runaway", but ... http://www.youtube.com/watch?v=MT0NJiRFA1s

My understanding (Pihero, Mandala499 correct me if I'm wrong) is that FAC failure will also result in a reversion to Alternate2, with a number of protections being lost.

[Edited 2015-01-21 13:31:41]
Empty vessels make the most noise.
 
tailskid
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 9:35 pm

Quoting Aquila3 (Reply 162):
Did I miss anything or am I stating the obvious?

It is I who missed something, not you. I wasn't aware that this stage of data storage existed.

This is kind of a big deal. May I suggest to the aviation community that these cards be put in a fire resistant container?  
 
LTC8K6
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 9:43 pm

Quoting tailskid (Reply 165):

It is I who missed something, not you. I wasn't aware that this stage of data storage existed.

This is an interesting read on Flight Data Monitoring/FOQA.

http://www.caa.co.uk/docs/33/CAP739.PDF

[Edited 2015-01-21 13:44:49]
 
LTC8K6
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 9:46 pm

 
Pihero
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 10:15 pm

Quoting Kaiarahi (Reply 164):
Regarding the continuous left turn, and reversion to alternate law, there were reports a number of years ago of FAC (flight augmentation computer) faults on A320s resulting in "runaway" rudder trim.

You could be onto something here.
Problem is : it requires loss of power to the FACs - flight augmentation computers which manage the rudder for coordinated flight and yaw damper.
I searched the net and found this :

"Safety Recommendation 2010-092
It is recommended that Airbus alert all operators
of A320-series aircraft of the possibility that an
electrical power generation system fault may not
be clearly annunciated on the ECAM, and may
lead to uncommanded rudder trim operation."
,

excerpt- from an AAIB reported incident on an A321 :here

A dual FAC failure seems to me one factor that could explain the event after the climb as it seems that the aircraft kept structural integrity all the way to the impact.

Another problem is that with both FACs failed, the flight control laws revert to ALT w/o protections.

It's not - obviously - the explanation. It just shows how drastic and how complicated the chain of events could have been on this accident.
Anyway, the failure(s) must have been severe, given how redundant the systems are on a modern jet.
It's one of the reasons I'd like to know whether the engines were running after / during the climb.
Contrail designer
 
Kaiarahi
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 10:27 pm

Quoting Pihero (Reply 168):
It's not - obviously - the explanation. It just shows how drastic and how complicated the chain of events could have been on this accident.

  

Quoting Pihero (Reply 168):
Another problem is that with both FACs failed, the flight control laws revert to ALT w/o protections.

I thought that even ALT2 had some protections left, but I'm always happy to learn.

Quoting Pihero (Reply 168):
It's one of the reasons I'd like to know whether the engines were running after / during the climb.

If they weren't, wouldn't there have been more systems failures than just the FACs (assuming the APU wasn't running)? How much airspeed does the RAT need (I realize it doesn't power the FACs)?
Empty vessels make the most noise.
 
hivue
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 10:34 pm

Quoting Pihero (Reply 168):
excerpt- from an AAIB reported incident on an A321 :here

Thanks. Very interesting.

This is worth a careful reading. It contains examples of some off-thread topics that previously have come up on this thread: "aviate, navigate, communicate" and the ability to manually fly modern airliners for extended periods of time at cruise altitude (FL360 in this case).
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
Pihero
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 10:44 pm

Quoting Kaiarahi (Reply 169):
If they weren't, wouldn't there have been more systems failures than just the FACs

Oh ! Yes !
What we call * ELEC EMER CONFIG (on BAT) * is no joke and at 60 kt indicated, I honestly doubt the RAT would deliver anything.

Quoting Kaiarahi (Reply 169):
I thought that even ALT2 had some protections left,

Sorry, problem of semantics : in ALT2, all protections are lost except load factor in pitch. Roll is in DIRECT mode, full authority ( Rudder is always in DIR in manual flight ).

[Edited 2015-01-21 14:47:32]
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Pihero
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 10:50 pm

Quoting hivue (Reply 170):
This is worth a careful reading. It contains examples of some off-thread topics that previously have come up on this thread: "aviate, navigate, communicate" and the ability to manually fly modern airliners for extended periods of time at cruise altitude (FL360 in this case).

Yes, but it would be a waste of time dealing with all the hijacking attempts on the thread !

But you're right : it is a good example of good CRM backing good SOPs.
Contrail designer
 
Kaiarahi
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Wed Jan 21, 2015 11:50 pm

Quoting Pihero (Reply 171):
Oh ! Yes !

Ouch!!

Quoting Pihero (Reply 171):
What we call * ELEC EMER CONFIG (on BAT) * is no joke and at 60 kt indicated, I honestly doubt the RAT would deliver anything.

That's what I thought.

If the information Mandala499 has gleaned about weather being no more than a secondary factor is correct, we can probably discard water/ice ingestion as the cause of a potential flameout. Which leaves?? - fuel contamination (there were reports of fuel issues at SUB at some recent point - I don't know if they were validated), and ??
Empty vessels make the most noise.
 
CabSauv
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 3:00 am

Quoting Kaiarahi (Reply 173):
Which leaves?? -

as you said, fuel could be an issue (as fuel starvation could cause a flameout, what could cause an issue with fuel flow to the engine ? - extreme temps ?)

If there was a compressor stall, which as I believe may be caused by e.g. extreme (cold) ambient temperature that may explain a bit of it, then again Madala499 mentioned that weather may not have been a major factor.

was there any update on the last few weeks or so to the auto throttle system / software ?

Gut feel is that there may be a history with the specific aircraft though.
 
rwessel
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 3:02 am

Quoting timpdx (Reply 110):

thx flightless, I do some 3D work for film/TV (and I am also a photographer, and have experience back to the film days), and I agree with your assessment of 191. That and the report that the engine was turning rpms and attached when the plane hit the ground. At the point of the flight where the photo was taken there is no centrifugal force, nothing pulling the engine away at 45 deg. 191 is on a curve headed towards the earth like a thrown rock.

Nor was there enough "crosswind" to cause any sort of structural issue. Assuming a 200kts velocity (it was lower), the apparent 35 degree relative wind (it looks like it's pretty perpendicular to the wing, which is swept 35 degrees), would have only been a cross wind of 100kts.

Quoting s5daw (Reply 125):
If a plane suddenly enters a column of rapidly raising air, doesn't that mean the AoA increases a lot in moment?

If the plane is cruising at 250 m/s (TAS) in calm air, and suddenly enters a column of updraft which is raising at 30 m/s, that would increase the AoA of the relative wind by 7 degrees. If I'm not mistaken AoA at cruise is not 0, according to some forum posts here it's about 5-6 degrees. Adding 7 degrees means the AoA is rapidly increased to 13 degrees. What is max AoA at cruise?

Most likely the aircraft would be cruising at 3-4 degrees alpha, and stall would be at around 14. But yes, a sudden updraft would increase alpha to the ~11 degree range, but would likely not stall the aircraft. And since the aircraft would have been trimmed for the 3-4 degrees cruise, and the tail would be producing negative load to keep the nose up, that updraft would immediately get the tail to rise and the nose would pitch down. Further, strong updrafts ten not to have edges that sharp, so the aircraft will start pitching down before it hit the full strength part of the updraft.

Quoting dtw2hyd (Reply 153):
Assuming there was no updraft, ignoring what was it designed for, can a A320 with 2xCFM56 engines carrying 160+ pax climb 12000 fpm?

Sure, just get the speed high enough and haul back on the stick. What an A320 *won't* do, is maintain that rate of climb for very long, since most of the energy for that climb is coming from the conversion of its forward velocity.
 
CO953
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 3:24 am

From what I am reading, we may be looking at a severe, short-term weather event and its interaction with the plane's sensors, and how those sensors interacted with the computers, and how those computers interacted, in a bifurcated, possibly entwined (but not necessarily quarantined) manner - firstly with the control surfaces and throttles, and secondly with the pilots - who were, in some degree, (either allowed intentionally by the computers, or alternately - and possibly intermittently - through the intentional, or default, abdication of control by said computers in totality or in part) afforded by the computer the opportunity throughout or partially throughout the emergency to input suggested corrections to how the computer was flying the plane, and to whether the computers allowed those inputs to be fully translated into action ... or whether those human inputs were blunted/overruled by the computers.
 
flightless
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 3:48 am

Someday I am going to diagram that sentence.

Someday... when I am really really freaking insomnio-bored.

(I *think* I agree with what you're saying, though)
 
LTC8K6
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 3:52 am

Quoting CO953 (Reply 176):
From what I am reading, we may be looking at a severe, short-term weather event

So far, it seems to be leaning towards weather not being a major factor.

I also think that early on, some posters pointed out that the plane did not actually seem to be in any severe weather at it's last known position.
 
spacecadet
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 4:28 am

Quoting dtw2hyd (Reply 140):
Then why bring irrelevant "most modern ATC systems" into simple ADS-B transmission and receiving/monitoring discussion?

Because if it's good enough for them, it's good enough for the people reading and replying to this thread, some of whom seem to believe ADS-B is less accurate than primary radar, and deriving its data from sensors on the airplane.

Quoting dtw2hyd (Reply 140):
AirNav Indonesian is not primarily dependent on ADS-B

Not relevant.

Quoting dtw2hyd (Reply 140):
it uses SSR/PSR for its primary ATC function

Not relevant.

Quoting dtw2hyd (Reply 140):
Like most AirNavs, Indonesia has capability to monitor ADS-B transmissions.

Very relevant, insofar as that is where the ADS-B data we have is (apparently) coming from.

Quoting dtw2hyd (Reply 140):
If it cannot get lock on minimum required satellites its accuracy will go down. A plane having problems will definitely have trouble locking GPS signal.

Please see this document: http://www.gpo.gov/fdsys/pkg/FR-2010-05-28/pdf/2010-12645.pdf

That document shows the FAA's requirements for ADS-B accuracy. Now, obviously this was not an American plane, but Airbus is not installing different ADS-B transponders for different countries - every A320 is going to be able to fly to any country where it's certified. So those same minimums apply.

The ICAO has a separate document (this site doesn't like me to link to it for some reason) that shows that ADS-B data should be accurate to within 1-3 meters.

There is no reason why a plane "having problems" would "definitely" have trouble locking onto a GPS signal. Unless you're trying to argue that the transponder was part of the cause of the crash. If it had nothing to do with the crash, there's no reason why it would suddenly stop working properly even as it continued sending data. You may as well say the same about every other electronic system on the plane, including the FDR. Stuff doesn't just randomly break - there has to be a reason for it.
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ComeAndGo
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 4:30 am

Quoting LTC8K6 (Reply 178):
Quoting CO953 (Reply 176):
From what I am reading, we may be looking at a severe, short-term weather event

So far, it seems to be leaning towards weather not being a major factor.

I also think that early on, some posters pointed out that the plane did not actually seem to be in any severe weather at it's last known position.

Then why did the pilots ask air traffic control for a climb to a higher flight level ?
 
mandala499
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 4:30 am

Quoting Kaiarahi (Reply 164):
Regarding the continuous left turn, and reversion to alternate law, there were reports a number of years ago of FAC (flight augmentation computer) faults on A320s resulting in "runaway" rudder trim. From Youtube (not "runaway", but ... http://www.youtube.com/watch?v=MT0NJiRFA1s

My understanding (Pihero, Mandala499 correct me if I'm wrong) is that FAC failure will also result in a reversion to Alternate2, with a number of protections being lost.

You got something there...
Ironically a local media called me today and asked about MELs related to:
AUTO FLT RUD TRV LIM (and 2)
ELAC 1 FAULT
Rudder travel limiter 2 fault identification and MEL Cat C allowances
AUTO FLT RUD TRV LIM SYS
FAC 2 FAULT

This... they said was from the aircraft's write up...

Quoting Pihero (Reply 168):
"Safety Recommendation 2010-092
It is recommended that Airbus alert all operators of A320-series aircraft of the possibility that an electrical power generation system fault may not be clearly annunciated on the ECAM, and may lead to uncommanded rudder trim operation.",

Uncommanded rudder command or rudder trim is being suspected.

Quoting Pihero (Reply 168):
A dual FAC failure seems to me one factor that could explain the event after the climb as it seems that the aircraft kept structural integrity all the way to the impact.

Another problem is that with both FACs failed, the flight control laws revert to ALT w/o protections.

It's not - obviously - the explanation. It just shows how drastic and how complicated the chain of events could have been on this accident.
Anyway, the failure(s) must have been severe, given how redundant the systems are on a modern jet.
It's one of the reasons I'd like to know whether the engines were running after / during the climb.

Dual FAC fail or fault could have caused reversion to ALTN NO PROT...
Even Yaw Damper failure could have caused the above.
If it's an FAC 2 fault only, I wouldn't suspect Yaw Damper failure...
But ELAC2, and FAC2 swap (with another aircraft) and the write ups... does raise my eyebrow...

Quoting Kaiarahi (Reply 169):
I thought that even ALT2 had some protections left, but I'm always happy to learn.

A320 has a different albeit similar reversion chain...
Dual FAC fail, Dual HYD (Green & Yellow) fail, Yaw Damper Failure = Pitch ALT (REDUCED PROT), ROLL DIRECT, YAW MECHANICAL

ALT NO PROT (ALTN 2) in A330 would translate in A320 to...
Pitch: ALT NO PROT
Roll: DIRECT
Yaw: ALT
This requires:
Double ADR Fail (with 1 fail not through self detection of VCAS or M disagree)
Triple ADR Fail
Double SFCC Fail
Double HYD fail (Green & Blue)

This is not what we seem to be looking at ALT RED PROT not ALT NO PROT.

Quoting Pihero (Reply 171):
What we call * ELEC EMER CONFIG (on BAT) * is no joke and at 60 kt indicated, I honestly doubt the RAT would deliver anything.

Let's just assume for the moment that the engines are running to the very end...   *hint hint*
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
LTC8K6
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 4:46 am

Quoting mandala499 (Reply 181):
Uncommanded rudder command or rudder trim is being suspected.

Sudden, or gradual?
 
 
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Moose135
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 5:07 am

Quoting ComeAndGo (Reply 180):
Then why did the pilots ask air traffic control for a climb to a higher flight level ?

Any number of reasons - maybe there was some turbulence, and they wanted a smoother ride, maybe it was to get to their optimum cruise altitude...
KC-135 - Passing gas and taking names!
 
michi
Posts: 266
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 5:14 am

Quoting ComeAndGo (Reply 180):

Requesting a climb is normaly not used to avoid bad weather.

They where filed for a higher FL. So asking for a higher FL is not suspicious.
 
ap305
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 5:41 am

The whole fac fail concept is way above my understanding but *If* this is indeed some form of outright system issue on the a320, it would be very very strange for it to cause a crash after 25 years of commercial service?     I sure hope it's not a design issue given the sheer number of passengers that these aircraft carry every day...
Racing, competing, is in my blood. It's part of me, it's part of my life; I've been doing it all my life. And it stands up before anything else- Ayrton Senna
 
benjjk
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 5:44 am

Quoting CabSauv (Reply 174):

Why the focus on the engines? A dual engine failure should not result in this.
 
RickNRoll
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 5:55 am

Quoting LTC8K6 (Reply 183):
http://news.detik.com/read/2015/01/2...-hilang-di-ketinggian-24-ribu-kaki

Translation (from google)

Jakarta - Transportation Minister Ignatius Jonan said AirAsia plane swooped quickly within 1 minute , then go down and disappear . What is the actual height of the peak of the AirAsia achieved and how the current altitude is lost ?

Of meeting materials document MoT with Commission V on Tuesday ( 20/01/2015 ) night obtained journalist , seen last minute based on radar data , as follows :
 
nm2582
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 6:11 am

Is there any scenario where the strong climb would be a desired and intentional response to a runaway rudder or rudder trim scenario? I'm not a pilot, but the only thing I could think of is a climb as an intentional and significant reduction in speed - but that seems like the last thing you'd want to do (reducing aileron authority and getting closer to a stall speed) when dealing with the initial phases of an out of control yaw.

If all protections were lost in pitch, and the FBW system was no longer maintaining altitude with 0 input on the side stick (I believe this would be a direct or mechanical mode, but again I'm not a pilot); would firewalling the engines generate the climb that was observed on radar? My gut instinct says no, that there wasn't enough power available to generate such a climb without a pitch input - but that loops back to, why would such a pitch input be desired/intentionally commanded?

Which makes me wonder if they had little or no control in both yaw and pitch....

I assume there would have been significant roll authority available, at least initially, in order for the radar observed flight path to be possible.

[Edited 2015-01-21 22:12:46]

[Edited 2015-01-21 22:23:24]

[Edited 2015-01-21 22:23:57]
 
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zeke
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 6:53 am

Quoting nm2582 (Reply 132):

One ***possibility*** is that they were already in a degraded law. I have been wondering if an Airbus pilot would continue a flight in a non-normal law (or if a degradation justifies a diversion); and I found this:

I have continued on before after a TAT probe failed, or a dual triple FMGC resets.

Quoting spacecadet (Reply 139):
The source for ADS-B data is GPS.

Actually the navigation system, the two GPS receivers are inputs for the mix GPS/IRS position. What is getting mixed up here is people are using radar data and ADS-B data interchangeably which is not correct.

Quoting dtw2hyd (Reply 140):
Thats it. Still cannot be used for Performance Based Navigation.

It is in Makassar.

Quoting Brick (Reply 147):
Once you level out it can take some time for the GPS accuracy to come back. It's a common problem with aircraft that collect aerial photography or LiDAR data.

RTK/survey issues are different than normal navigation. The A320 uses a mixed GPS/IRS position.

Quoting ComeAndGo (Reply 180):
Then why did the pilots ask air traffic control for a climb to a higher flight level ?

They were flight planned FL380

Quoting mandala499 (Reply 181):
Ironically a local media called me today and asked about MELs related to:
AUTO FLT RUD TRV LIM (and 2)
ELAC 1 FAULT
Rudder travel limiter 2 fault identification and MEL Cat C allowances
AUTO FLT RUD TRV LIM SYS
FAC 2 FAULT

The rudder travel limiter does not move the rudder.

Quoting mandala499 (Reply 181):
But ELAC2, and FAC2 swap (with another aircraft) and the write ups... does raise my eyebrow...

Mine too, you cannot just start moving computers from one aircraft to another without checking to see of they are compatible part number and compatible software version for the mod status of the aircraft.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
rheinwaldner
Posts: 1865
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 9:42 am

Quoting ap305 (Reply 186):
I sure hope it's not a design issue given the sheer number of passengers that these aircraft carry every day...

The mean-time-between-failure for any particular error condition is different. So any designed machine can have flaws that happen only in very rare cases. So rare, that the overall safety is not impacted notably (in other words: this particular error condition happened uniquely in the whole history of operation and not does stand out as repeated accident reason).

So it is alway possible that there are error conditions that happen so rarely, that they have:
a) not been found during testing/certification.
b) on the other hand are also not relevant to be considered for the ongoing operation of other aircraft of the same type.
Many things are difficult, all things are possible!
 
Pihero
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 9:43 am

Quoting mandala499 (Reply 181):
This... they said was from the aircraft's write up...

Hell !
That's another bloody good reason to access the QAR and get the monitoring data for these faults.
Get that minister to stop politicizing and start actions toward safety !

I need to get my hands on the 320 MEL as I don't recall multiple faults being allowed on the flight control systems.

Quoting CO953 (Reply 176):

From what I am reading,

A sentence that covers seven lines without a break... Possibly an A.net record... Please be nice to us non native English speakers as we can't understand

Quoting zeke (Reply 191):
Quoting mandala499 (Reply 181):
But ELAC2, and FAC2 swap (with another aircraft) and the write ups... does raise my eyebrow...
Mine too, you cannot just start moving computers from one aircraft to another without checking to see of they are compatible part number and compatible software version for the mod status of the aircraft.

I missed that one... T'was late. but I agree with you.
Contrail designer
 
BestWestern
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 10:23 am

Wow - leaky bucket in the Indonesian CAA these days.
Greetings from Hong Kong.... a subsidiary of China Inc.
 
LTC8K6
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 12:30 pm

Here is another plot posted on pprune with more info. Can't vouch for it's accuracy, but it seems to basically match what is leaking out.

 
s5daw
Posts: 348
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 12:42 pm

that is stall and spin all right… the key question is, what made them go up at 12.000 fpm…
 
dtw2hyd
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 12:52 pm

Quoting spacecadet (Reply 179):
Because if it's good enough for them, it's good enough for the people reading and replying to this thread, some of whom seem to believe ADS-B is less accurate than primary radar, and deriving its data from sensors on the airplane.

Let me try to explain why PSR is better than ADS-B/SSR with a normal day example.

A corrupt SSR transmission is like
Parent on the phone: Where are you?
Kid: I am at school (actually at a mall)

A corrupt ADS-B transmission is like a kid calling parent ahead to say he is at school, actually at a mall.

PSR is like someone having eyes on the kid.

If you are not able to see the difference, good luck.

Quoting spacecadet (Reply 179):
Very relevant, insofar as that is where the ADS-B data we have is (apparently) coming from.

Any kid on FR24 site can do the same.

All I am saying is you need corroborating evidence to confirm ADS-B/SSR data.

So far all leaks (ATC screen shot, ADS-B screen shot and today the presentation slide) showing from SSR/ADS-B. We need something from FDR to prove it.

Quoting spacecadet (Reply 179):
There is no reason why a plane "having problems" would "definitely" have trouble locking onto a GPS signal.

See upthread about explanation of GPS accuracy when banking steeply. Unless you are claiming QZ8501 was in a level flight all the way to sea level, GPS accuracy is questionable. Again for altitude discussion I think GPS is irrelevant.

Quoting spacecadet (Reply 179):
Quoting dtw2hyd (Reply 140):
AirNav Indonesian is not primarily dependent on ADS-B

Not relevant.

Quoting dtw2hyd (Reply 140):
it uses SSR/PSR for its primary ATC function

Not relevant.

Both are relevant because using ADS-B for monitoring is different from using for PBN.

Quoting spacecadet (Reply 179):
That document shows the FAA's requirements for ADS-B accuracy. Now, obviously this was not an American plane, but Airbus is not installing different ADS-B transponders for different countries - every A320 is going to be able to fly to any country where it's certified. So those same minimums apply.

ADS-B uses GPS for location data.
ADS-B uses barometric altitude (or other alternate sources like radio altimeter)
All posts are just opinions.
 
therealswede
Posts: 33
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 1:01 pm

Wow, that's interesting! Wonder how accurate it is, but it goes well with what Mandala has provided so far.
One of the (many) sad things, 38850 -> 0 in 2 minutes. Around 100 m/s average descent?
Once the initial stall, it never stopped dropping like a bomb it seems!?
Really sad story, but at least there seems to be a substantial technincal problem behind the accident.
 
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BaconButty
Posts: 825
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RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 1:33 pm

Quoting dtw2hyd (Reply 197):
All I am saying is you need corroborating evidence to confirm ADS-B/SSR data.

It's self-corroborating to a point. What I mean is, for e.g., both geometric and barometric altitude are provided.

Secondly, there's a stack of quality and integrity indicators passed - not just one. They're listed in appendix 1 (message element descriptions) here - it's well worth a read:
http://www.faa.gov/documentLibrary/m.../Advisory_Circular/AC%2020-165.pdf
You're looking at NIC, NACp, SIL, SILsupp, SDA, NACv, NICbaro, GVA - 8 parameters related to integrity and accuracy. Add to that you have vector information you can effectively sanity check each position against the previous via dead reckoning - or rather apply a kalman filter.
Down with that sort of thing!
 
Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: Air Asia QZ8501 SUB To SIN Crash - Part 12

Thu Jan 22, 2015 2:15 pm

Quoting baconbutty (Reply 198):
It's self-corroborating to a point. What I mean is, for e.g., both geometric and barometric altitude are provided.

Yes. That's why we use secondary radar and ADS.
The precision / accuracy of the system is extreme... and we trust it with our lives every hour of the day.

Quoting s5daw (Reply 195):

that is stall and spin all right

.
No, you can't say that based on these data : with a ground speed of 65 kt - ish - and a turn diameter well above 1nm = 1850 m or so, that's not even a tight turn. For a comparison, a rate one (standard turn ) at 60 kt has a diameter of 2/3 nm =1200 m with a bank angle of 10°.
Contrail designer

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