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Old 5th Jul 2009, 07:52
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I have reservations about a flat spin with no forward motion; but with the information publicly available it may be impossible to rule it out.
The theory of a flat spin is completly unfounded. I don't know where this idea started, but I guess it came from Bea's expression "with a high rate vertical acceleration".

Now think just one moment: If you would flat spin a widebody airliner (which I still believe is impossible), what acceleration happens during impact? In the spinning axis of the fuselage, right in the middle, there is nearly zero forward motion and heavy negative vertical acceleration. Perfect for the flat spin theory.

Now change to other parts of the aircraft, e.g. the tail. What acceleration appear there? Because of the rotational speed, there would be heavy decceleration to the side. Which is known to be not happened. Because the vertical stabilizer was found as a whole. It would have simply been clipped of the fuselage.

That's what Bea wanted to tell us: All forces they could assess where vertical decelleration. This happens in a relatively straight flight profile with high sink rate. There was some forward motion, too, I'm sure. But the forward decceleration was way slower and thus didn't deliver marks on the wreckage.

So, please, abandon the spin theory. It's useless.

Dani
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Old 5th Jul 2009, 07:53
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ttsce - really brief - for Inmarsat satellite frequencies the answer is "some" but not dramatically. The antenna tracking test for Inmarsat-M antennas was suited for a ship in very rough weather that would normally include a deluge. And that's in the same band as the new stuff.

JD-EE
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Old 5th Jul 2009, 08:16
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Personally I'll believe almost any scenario that does NOT require the airplane to have gone "straight down" when the problem occurred. I believe this lets out flat spin, and may even let out normal spins and spiral dives.

Why? Because if we believe the ocean current drift data and see where stuff was recovered on the 6th and back-plot it, it ends up about 30nm before the 02:10 ACARS fix. So if the problem happened instantly at 0210, the plane has to turn around in zero distance and cover 30 miles backward. Since it isn't likely it turned around in zero distance and it isn't likely the problem happened exactly at 02:10, the plane probably covered closer to 100+miles horizontally from failure to impact.

Now, let's come up with a failure scenario that starts at 02:13-02:14 or later and ends up 30nm south of the 02:10 fix.
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Old 5th Jul 2009, 08:32
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Now, let's come up with a failure scenario that starts at 02:13-02:14 or later and ends up 30nm south of the 02:10 fix.
- err, you mean like maybe they turned back towards the mainland following the 'problem', as previously mooted?
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Old 5th Jul 2009, 08:48
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Originally Posted by DJ77
My point is not to throw a judgment on the position relative to the weather. It is that the a/c was not riding on the airway centerline with the AP in NAV mode straight into the storm, as have been suggested earlier. The pilots almost certainly attempted deviations. I don't pretend this is a big piece of information either.
Looking at the flight path it seems the 2:10 position is the only one slightly off course. If that was due to systematic inaccuracy of the position records one would assume previous postions to be similarly off track.

Not beeing on centerline at 2:10 could be due to a decision to deviate, but could also be a result of the trouble that began around this time.
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Old 5th Jul 2009, 09:13
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Ttcse

"The rotational speed of a large aircraft in a spin or flat spin would be slow. Approximately 3-4 secs per rev?"

Unless my maths have let me down , with a revolution every 4 seconds, then the tail would have been rotating sideways at circa 100mph - this is a significant speed.

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Old 5th Jul 2009, 09:16
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ttcse,

Any guesses where the 'torsional' component of separation for the vs came from?
They could come from whatever twisting forces. During an impact, you experience tremendious forces, and the tail is the last one to get them passed on. They could also be in a slight turn.

The report says: "The distortions of the frames showed that they broke during a forward motion with a slight twisting component towards the left."

So, if they are right, the forward motion is bigger than the twisting. That couldn't be the case if in a flat spin.

Anyway, the discussion about spin or not is useless. Because it doesn't deliver a theory about the cause, only about the outcome. We are not interested how they crashed, but why they did (Boac, you remember our discussion in the THY/AMS thread?)

Dani
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Old 5th Jul 2009, 09:33
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So if the problem happened instantly at 0210, .

THE problem? Clearly ACARS is saying something is happening at 0210.
Yep, THE problem. Yes, we know that something started to happen around 0210 that looks a lot like pitot icing, but might be something else. But many have asked why pitot icing caused a problem here and it didn't for many other planes.

So I presume that the reports starting at 0210 are indications of Bad Things, but that they are not THE problem, since they don't seem to be sufficient by themselves. I presume THE problem (disorientation, food poisioning, both pilots asleep, pick a reason, whatever) occurred subsequently to the first 0210 report, but maybe before the last 0214 report. This is of course pure supposition - but at this point supposition is all that we have informaiton for.

the plane has to turn around in zero distance and cover 30 miles backward. Since it isn't likely it turned around in zero distance and it isn't likely the problem happened exactly at 02:10, the plane probably covered closer to 100+miles horizontally from failure to impact.

Keep in mind
1)that would be re-entering that cell(indications that particular one reached FL500) they just passed thru (when viewed from above) to go toward the south.
Yes it would. You will note I did not say they voluntarily turned around. I said "X marks the spot" was a spot on their track before the 0210 position. They got there somehow.

2)as they couldn't reach 100 miles in 4 minutes, how would you then explain the termination of messages at 02:14?
Explain? I don't, insufficient data. I can guess lots of things. Maybe they lost electrical. Maybe they crashed at 0214. Maybe something else happened. Keep in mind we don't know where they were at 0214. If the flat spin scenario will get you 'straight down' to the ground in 4 minutes starting at 0210, maybe some other spin will get you 30 miles south of 'straight down'.

While I try to figure out how to do that why don't you work on a solution for landing with mostly a vertical descent onto their belly upon arrival at the backtracked debris zone.
I already did that several posts back. Stall it in nose high at about a 45 degree glideslope. The acceleration vector will be about normal to the "down" direction in the cabin, and the tail hitting first will rip off the VS in the manner the BEA wants it to go.

Last edited by WhyIsThereAir; 5th Jul 2009 at 09:59.
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Old 5th Jul 2009, 09:59
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Could an attitude of 5 degrees nose up and power to CT (AFAIK A330 SOP for innacurate IAS above FL10) help inducing a stall to a heavy A330 at FL37? at certain ISA temps and fast A/C speeds?
B/R
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Old 5th Jul 2009, 10:09
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Dani

So, if they are right, the forward motion is bigger than the twisting. That couldn't be the case if in a flat spin.

Anyway, the discussion about spin or not is useless. Because it doesn't deliver a theory about the cause, only about the outcome. We are not interested how they crashed, but why they did (Boac, you remember our discussion in the THY/AMS thread?)

Dani
You are making statements that are totally unsupported.

What evidence is there that the rotational element in a flat spin is greater than the forward. None at all. You just 'invented' that 'fact'. A flat spin can easily have a fairly modest rotational element if the autorotational forces are small due to a number of factors. Speculation on a rate of rotation is fruitless, it is slower for larger aircraft but we cannot say how slow.

Your repeated assertion that large aircraft cannot flat spin is frankly valueless. You have no evidence to support that. The dynamic forces that create a flat spin in small aircraft can easily be scaled up. Also, several large aircraft have entered spins. If you enter a spin then all that is required to make it a flat spin is longitudinal force (e.g. power).

So 1. Large aircraft can spin. Many have. 2. A spin WILL flatten if you apply longitudinal force.

Therefore it is feasible to flat spin a large aircraft.

I am not saying that this is what happened but it would be foolish to dismiss it.
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Old 5th Jul 2009, 10:58
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I am amazed that not one of you responded to the obvious, that is, without the wreck and/or the CVR/FDR no one can draw any positive conclusions, everything is spectulation.
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Old 5th Jul 2009, 11:00
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To get back to reality.

The nominal life of the data recorders' under-water beacons is up very shortly.

Does anyone know ;

a: Any serious reports of the work being done in searching for the data recorders and their possibilities of success (including depth of water being searched) ?

b: Is the expected life "conservative" and whether it is likely that they will continue to operate (if they are so doing) for a reasonably longer time ?

AND,

I ASSUME, that if they give up the acoustic search for the data recorders that that will be the end of the serious search for the remains of the aircraft ?

Any sensible information gratefully received.

.
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Old 5th Jul 2009, 11:02
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So are the previous statements about bodies being "unclothed" and all exhibiting "typical flail injuries" normally associated with meeting the high speed airflow of airframe breakup, now being discounted? Surely post mortem examination of bodies is the most precise evidence available in this case. It should be possible to clearly establish whether a body was ejected into a high speed airflow and then fell at terminal velocity till it hit the sea...As opposed to a body that was inside an aircraft that struck the sea.
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Old 5th Jul 2009, 11:10
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ttsce - really brief - for Inmarsat satellite frequencies the answer is "some" but not dramatically. The antenna tracking test for Inmarsat-M antennas was suited for a ship in very rough weather that would normally include a deluge. And that's in the same band as the new stuff
Ships have no or little limitations in terms of space, weight or aeodynamics.
There is no comparison between a 20dB+ parabolic antenna (with tracking) on a ship and an a/c planar omnidirectional antenna.

So they do specifically state which satellite was in use and that basically puts them almost dead center under it. It would take something fairly dramatic for them to lose the satellite. A 30 degree or so change in attitude that was not corrected by the antenna steering logic could do it.
Steering logic ? are you sure Aero-L antennas (L band !) have tracking capabilities ?
Dead center or not does not make a difference, be it 35,800 or 37,000km, same thing.
Point is, the link is not 100% guaranteed, and while L band is a lot less sensitive to precipitations or proximity to the core of a storm than eg. Ku band, it still is not immune.
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Old 5th Jul 2009, 11:46
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My understanding (talking to an avionics development eng) is that the battery life of the FDR and CVR beacons is very conservative. As in most things in aviation, they are built with generous margin to ensure that they meet the specifications in any forseeable circumstances.
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Old 5th Jul 2009, 11:51
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320 driver:
What evidence is there that the rotational element in a flat spin is greater than the forward. None at all.
what? Definition of a flat spin is that there is no forward movement at all, while, at the same time, there is a great rotational movement. How do you define flat spin?

Of course, my statements are purely speculative, as are yours, as are all the others. I merely say that there isn't a widebody that ever has spun. Period.

ttcse urged my to deliver examples of other aircraft accidents, but I think it is your turn to show me one single accident where there was a spin. If you have ever tried to stall an airliner (real or in a sim), you see the slugishness, the inertia, that doesn't allow them to spin. It's more like a lazy spiral downwards.

If the aircraft is crippled to a certain extent, that may be different. Bea states that this was most probably not the case. Not crippled in this context is defined by still all important part where attached: fuselage, wing, stabilizers.

Dani
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Old 5th Jul 2009, 12:06
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320 driver:
My understanding (talking to an avionics development eng) is that the battery life of the FDR and CVR beacons is very conservative. As in most things in aviation, they are built with generous margin to ensure that they meet the specifications in any forseeable circumstances.
Hi,
It was my understanding also until I read lately a paper from the pinger manufacturer. The manufacturer opinion is that the pinger signal is expected to fade very quickly after operating for 30 days. I can't provide the link for it, as I didn't recorded it, but the sense of this statement was very clear: do not expect any signal lasting very long after the designed 30 days. Hence, the accoustic search will stop after 40-45 days because it would be useless to do otherwise.

If the accoustic search is unsuccessfull, the next step would focus on finding the airframe wreckage using adequate means. The BEA first examinations are not ruling out the existence of large pieces of wreckage at the bottom of the Ocean and its a good thing.

The very bad case would have been a shattered field of small wreckage making it almost impossible to precisely locate it but it doesn't fit with the impact clues revealed.
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Old 5th Jul 2009, 12:35
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what? Definition of a flat spin is that there is no forward movement at all, while, at the same time, there is a great rotational movement. How do you define flat spin?
That is NOT a definition of a flat spin. A flat spin is one where the attitude is close to the horizontal plane. Forward motion doesn't enter into it. It is entirely possible to have a flat spin with some forward motion.

Please stop posting comments that extend far beyond your knowledge.
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Old 5th Jul 2009, 12:42
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Dani

Air China span a 747 in a well documented incident off the coast of California.

Dai Davies talks extensively about risk of spinning large gets in 'Handling Tne Big Jets' which is regarded by most as the seminal work on large aircraft handling. If Dai Davies thinks there is enough spin risk to warrant writing about prevention and recovery then I suggest the risk is real.

Or are you prepared to tell us all that you think Dai Davies got it wrong?
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Old 5th Jul 2009, 12:43
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6G on a FBW?

My question now to the Airbus gurus here is does the airplane allow you to exercise your piloting skills to maximimun advantage in an untrained and or unplanned situation? Remember, I am a Boeing/Douglas guy. Can you pull as hard as may be required? The difference between hitting the ground/ocean and recovery may well be pull hard on the horizion.

I will leave this open for discussion. Obviously the TWA aircraft under Capt. Gibson's command survived a 6 g recovery. The B-727 was never designed for this load factor, and the airframe in question was retired.

I do not want to hear BS about airframe certifiaction standards, comparrison in G loadings, etc. I will supply a link soon to the TWA incident, but I would hope that all professional aviators on this thread are aware.''
To answer your question:
Even in ALT LAW 2, Pitch Control is identical to ALT LAW 1 where flight law is a Load Factor demand law, similar to Normal Law, with limited pitch rate feedback and gains, depending on speed configuration.

Low Speed and High Speed Stability is available but with Pitch Attitude Protection Lost.
There is no Bank Angle Protection.
And,
In case of 2 ADR failure, there is No Low Speed Stability;
In case of 3 ADR failure, there is No High Speed Stability.

I therefore would tend to suggest that one could only pull 2,5 G's except if, due to other associated failures, the aircraft would change to Direct Law and Pitch Inputs would be then directly commanded by the pilots.

In other words, only in Direct Law, pilots are allowed to pull more than 2,5 G's...

To answer mine:
IMHO, this means also, that due to High and Low Speed Stabilization (where the aircraft gives inputs to the flight controls to prevent stalling it [and therefore, spin it]) and also to the fact that AoA data is provided to BUSS - Back Up Speed Scale, via the IR part of the ADIRU, in order to enter a stall the aircraft would have to have changed to Direct Law.

FCOM Abnormal Procedures tells us that even in a situation where two IR's or 3 ADR's are lost, Flight Controls Laws would still be ALT LAW 2.
This leads to me thinking that Human Factors may have played a role in the outcome of this accident. Pure speculation I must concede, as most of the argumentation I've seen in this thread.
Easy to accept that, in the middle of the stressing Unreliable Airspeed Indication troubleshooting, the (unprotected/unguarded) IR's were disconnected by mistake (in step of ADR's) in an attempt to display Backup Speed Tape...the rest one can guess. That's much easier, for me, to accept that, than a total failure of aircraft systems, tail fin or brake apart in several pieces.

Ready (and maybe deserving) to be flamed, now...

P.S.- Here's a partial transcript of Airbus Publication: SAFETY FIRST of Dec 2007 written by Joelle Barthe (Flight Operations Engineer, Airbus Industrie)

(my bolding)

In order to decrease the crew workload in case of
unreliable speed, Airbus has developed the Back-
Up Speed Scale (BUSS) that replaces the pitch
and thrust tables. The BUSS is optional on
A320/A330/A340. It is basic on A380, being part
of the ADR Monitoring functions.
This indication is based on angle of attack (AOA)
sensor information, and is therefore not affected
by erroneous pressure measurements.
The BUSS comes with a new ADIRU standard
(among other new system standards), where the
AOA information is provided through the IRs and
not through the ADRs. This enables selecting all
ADRs off without loosing the Stall Warning
Protection.

The AOA information provides a guidance area in
place of the speed scale. When the crew selects
all ADRs OFF
, then:
The Back-Up Speed Scale replaces the PFD
speed scale on both PFDs,
GPS Altitude replaces the Altitude Scale on both
PFDs.
The Back-Up Speed Scale then enables to fly at
a safe speed, i.e. above stall speed and below
maximum structural speeds, by adjusting thrust
and pitch.

Last edited by aguadalte; 5th Jul 2009 at 13:44. Reason: to add a partial text of Airbus's Safety First Issue
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