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AF 447 Thread No. 5

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AF 447 Thread No. 5

Old 28th Jul 2011, 19:30
  #841 (permalink)  
bearfoil
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Yes, I get that, and thanks. You are a man of Faith, then?
 
Old 28th Jul 2011, 20:07
  #842 (permalink)  
 
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Faith? Hell no.

Bear,

I wrote about ACARS messages that would have been in the list as of day 1 of the reporting about this accident.
Or do you think that they had it all figured out by then already: - let's not tell about the ACARS messages that have to do with radar loss, cause you'll see, in about 2 years time we will have to cover up about bad quality radomes?
Facts, my friend, not faith.
We will not need to have the CVR available on Youtube to check for ourselves that the radome did not get blown away.

Whether ice crystals impacting on the windscreen will be audible on the CVR - who knows, the Cockpit Area Mike is not a marvel of audio quality, but processing logic can sometimes provide pleasant surprises.
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Old 28th Jul 2011, 20:11
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Doing nothing

PJ2
By the phrase, I was assuming a great deal on the part of the reader. What I meant was, other than maintaining level flight as best one can using pitch and manual thrust settings, (which would be those which existed just prior to the failure), one "does nothing" in terms of climbing/turning/descending etc. Above all else, one stabilizes the aircraft in level flight. There is absolutely NO reason to change anything during a UAS event.

Can I -- a non-pilot -- tentatively challenge this wording.

There seem to be at least two situations where the current settings would not be "those which existed just prior to the failure":
a) The s/w "correctly" changed something. [e.g. IIRC the thrust changes on a/p drop-out].
b) The s/w has "inappropriately" (in 20:20 hindsight) modified the previous status-quo prior to the fully-recognised UAS event. [e.g. as a "correct" response to erroneous airspeed values.]

In either case the pilot needs to revert to something like the settings in effect before the s/w acted. In this situation "one stabilizes the aircraft in level flight" and "there is absolutely NO reason to change anything during a UAS event" would seem to be mutually inconsistent.

BTW I suspect that our positions could be reconciled by some sort of differentiation between "simple" and "complex/compound" UAS events.

As a retired s/w engineer, and assuming dual pitot failure:
If the 2nd pitot failure occurring while the 1st pitot failure was being analysed the s/w developers can be forgiven for failing to handle it "well". Especially as the s/w development team probably believed/were-told that double in-flight pitot failures were vanishingly improbable.

This could easily cause a brief period of erroneous airspeed, leading to: thrust changes, trim changes and a/p drop-out. Leaving the plane some way from steady-state-cruise settings.
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Old 28th Jul 2011, 20:18
  #844 (permalink)  
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Peter H.

Where have you been? You are so welcome here, at least by the bear.

The time to trim back on theory is after the data, not prior.




What was a/c doing for the last fifteen seconds prior to a/p loss?

What did the PF do for fifteen seconds after a/p loss?


Everything has been done to Death, except..........
 
Old 28th Jul 2011, 20:32
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Thanks for your answer PJ2. As usual reading another post of yours is delightful.

Originally Posted by PJ2
..."doing nothing".... By the phrase, I was assuming a great deal on the part of the reader. What I meant was, one "does nothing" in terms of climbing/turning/descending etc....
The "great deal" assumption that the reader does not need explanations, may imply straight forward that he does not need the summarized "doing nothing" either, as if he knows the first, he knows the latter as well.....
...
I assumed the airplane was just about as easy to fly in Alternate 1 and 2 and Direct Laws as it was in Normal. I have done this in the simulator many times...
Perhaps at a high experience/professional level the protections of Normal, versus Alternate 1, versus Alternate 2, versus Direct, don't bring or mean much, particularly in smooth non-adverse weather....

But we know their purpose, and that their degree of absence and importance becomes even more obvious when the flying conditions are no longer friendly and/or simple. And the short 4 minutes or less between life and death on the AF 447 exacerbates that like nothing else would....

As I mentioned before a recent cross continental flight with heavy turbulence almost out of nowhere, made me think a lot more...

Originally Posted by PJ2
I have learned through discussions.... that maintaining level pitch and bank attitudes in the circumstances you describe, would be challenging and perhaps even very demanding depending upon the second-by-second series of sidestick inputs over a short period of time.
Between a 200 tone airplane, at M0.8, and a 5 grams paper made plane at a hand throw speed, there may be a huge difference in mass, inertia, size of wings, and power behind the motion, but they are paradoxically similar, if not identical, in the proportionality of the air lift to their mass/weight.

That being said, the challenge in maintaining the level flight is the turbulent air in large masses, at random speeds, and random change of directions, which creates the demanding situation, to which the second-by-second inputs of the side stick are only the pilot's plane control responses/reactions.

Among many others, it is these very situations that elevate one having the control of the stick in the cockpit, to the title of true airline pilot, as much as many years ago, just flying an airplane would, and therefore I strongly believe they're worth mentioning.

In light of this,you may agree that the use of "do nothing" calls for an update, as it may present the risk of telling selectively only part of the story, which means the risk of over simplifying - (edited: trivializing)....
....
As much as the tremendous progress in the science of making and controlling flying objects after of about 100 years - although more, or even a lot more, if we go back to daVinci, or Icarus.... - with each step, and each gain, the pushing forward of the boundaries of knowledge brings with them inherently, also the boundaries of the unkown. The AF 447 seem to be an apogee, or a burst of a collection of unknowns, of the current stage in technology, and industry, which like many of the past, came with a tremendous, undesired, and sad sacrifice. When resolved - and one has to recognize the resources allocated by the French Government, BEA, Airbus, and Air France, the Industry at large, the International community for the resolution - the solutions will be, along with many other elements another step forward in the knowledge and advancing of man.

And hey... , even this Forum, and these threads are somewhat a contribution, and part of that step forward, as meager as it may be, ....

Last edited by airtren; 28th Jul 2011 at 20:43.
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Old 28th Jul 2011, 20:59
  #846 (permalink)  
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I note a little angst arising between some of the posters.

Rest assured that, if I observe an excessively inappropriate post, I'll edit/remove it.

This doesn't extend to heavy handed moderating along any given party line eg I might not particularly like a particular style of post - however, so long as it generally complies with our requirements, my like/dislike is not a reason to censor it. Non-nasty banter and a bit of give and take is quite acceptable and the place would be boring without it.

If you, as an individual, take exception to a particular line of post, please either ignore the post and move on or, if you see the need, PM me and I'll review the complaint circumstances.
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Old 28th Jul 2011, 21:12
  #847 (permalink)  
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Peter;

Thank you for your thoughtful post.

Yes, I not only agree with your "notwithstanding", but know of at least one reasonable explanation for the immediate aft-stick movement.

Still, the key here is in the notion of "stabilizing the aircraft". One must absolutely establish control of the aircraft and one does what one must to maintain control, which also means avoiding those actions and changes which will de-stabilize the aircraft. So, for example, if there is a momentary apparent "loss of altitude", say 300ft (I am not citing a known example, I'm positing, here), the reaction could, (not 'would'), be to pull back and "regain" the altitude, from which one then levels off, sets power and gets out the QRH. I'm using quotation marks in this example because any such loss would almost certainly be an indication issue and not an actual loss of height, and in any case, such loss, real or merely indicated, is not serious and does not require instant response or correction when one is wrestling with another abnormality. Sure is easy to say and type, isn't it? My golly. We have to be so careful of hindsight bias when reading what is coming.

Of course, I, we, don't know if any of this occurred, but the notion does lie within what I would consider the "plausible" arena vice some of the theories placed out in the open for consideration by other contributors.
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Old 28th Jul 2011, 21:24
  #848 (permalink)  
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PJ2

I knew what you meant, from the git. However, lacking some explanatory, it is (perhaps), red meat for those ready to pounce. So you know, I am most grateful for your input. You and others have multiplied my meager knowledge manifold.

I come from a professional standpoint where it is not necessary to comfort the afflicted. More like afflicting the comfortable.

At no time do I believe it is appropriate to get personal. I hope my presence is not annoying to anyone, except to make my points, which I believe in.......

with great respect, Bear

(erm.....what was that back ss, then?)
 
Old 28th Jul 2011, 21:27
  #849 (permalink)  
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airtren;

Yes, the phrase "do nothing" doesn't really describe what one really does and should do when a UAS event occurs. One does something, but the goal is level, stable flight or a return to same with an establishing of the former cruise attitude and power - the goal isn't "5 degrees up, then sort it out" because that destabilizes the aircraft making it difficult to "find home" again.

Control in moderate to heavy turbulence is an issue dealt with in the FCOM - the SOP is clear: in addition to reducing Mach and disconnecting the auto-thrust, one also lets the speed and altitude wander slightly. How much is up to the pilot because the manuals cannot provide rules for everything. I've seen excursions between green dot and VMO, and +/- 300ft - the airplane "rides downhill or uphill" - it doesn't "fall"...(getting rid of the notion of the "air pocket" has been one of the toughest nuts to crack!) Temperature (SAT), wind shears of 60 to 80kts in short time periods, will result in all kinds of local instability which make control of the aircraft difficult, if only because it is tough to hang onto the stick in such conditions. So it's a factor, given all. My sense of it being a factor here is that it wasn't, or that it was light, possibly moderate but nothing more, but that's just me.
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Old 28th Jul 2011, 21:28
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Originally posted by BOAC ...
- this is NOT what the May BEA report said - perhaps you are 'clairvoyant' regarding the 28 July report? The stall warnings sounded BEFORE the climb.
We seem to have a difference of opinion over what happened following the AP/ATHR disconnect.

Ex BEA Note - From 2 h 10 min 05, the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row.
The graphic included with my post clearly indicates what is believed to have happened. The initial nose-up input was responsible for the double stall warning per the above quote, and if the attitude didn't change, then why did the AoA trigger the SW? The graphic(s) may be close to the truth or completely wrong, and remember you said, " [they] will pass rapidly into the 'factual' world - as pseudo FDR traces - when in fact they are supposition - guess-work - based on extremely limited information".

Nothings changed, and the 'facts' will supercede everything that this forum has promoted at each successive release of information by the BEA. Until then, I'm quite happy to be classed as 'clairvoyant'.
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Old 28th Jul 2011, 21:54
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Adr fault

The reason why ADR 1(2)(3) or ADR 1+2, 2+3 or 1+3 FAIL messages were absent is because the ADRs didn't fail.
They did send (CAS < 30Kts) a SSM(System Status Matrix) signal NCD and a value output of 0 Kts.


The SSM for digital on bus signals (Bit 31,30) of the ARINC word can have 4 states:
- NO (Normal Operation)
- FT (Functional Test)
- NCD (No Computed Data)
- FW (Failure Warning)

If a ADR failed (as detected by its own fault detection logic) the SSM is set to FW.
The FWC composes the exact ECAM warning, e.g. when ADR 1 and ADR 2 outputs a FW SSM then the FWC will send the warning NAV ADR 1 + 2 FAIL.

Since there is no crosstalk between ADRs, an ADR DISAGREE; ADR IAS DISCREPANCY or any other air data discrepancy can only be detected by a system which receives all 3 ADR ouputs, e.g. EFCS/AFS.

When all 3 ADRs signals are in NCD SSM state the value output is 0; so no difference between ADRs but also NO failure.
The logic I did post before did already show why the IAS discrepancy message was inhibited. (any ADR in NCD, dual ADR in NCD for 'frozen 'pitot)

Question is what will the FCPC do with the received NCD state of ADR?
Will it take the value of 0 Kts in account or ignore this ADR?
Maybe later today an answer?


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Old 28th Jul 2011, 22:41
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A33Zab,
Could we then think, as long as ADR DISAGREE was not present, that High and Low Speed Stabilities were at least available ?
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Old 29th Jul 2011, 00:03
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Le Point

Originally Posted by airtren
From listening to the interview, among the two interviewed pilots comments that I would mention, are references to the shortcomings of the "a/c to pilot information interface", the reviewing of procedures for such situations, and a dialog between Air France and other airline companies, on one side, and Airbus on the other, in that regard which is just at the beginning..
And some other comments made (I don't comment myself, just try to translate):
  • Pilots were fully aware of the weather situation. Weather situation had nothing of extreme, only relatively moderate turbulence.
  • Like a Boeing, the Airbus is a complex system, there are many computers, bugs and false indications are possible, and the user manual for the man-machine interface is not always understood.
  • The man-machine interface didn't work, it is the whole challenge, and the object of the coming legal battle.
  • Inappropriate maneuver has been applied, but we understand why such wrongly doing could take place.
  • It will be necessary to review the user manual.
  • It will be necessary to review the procedures to be applied in extreme situations.
  • The Airbus is different from any conventional aircraft in a way that it will maintain the last flight control order.
  • I've made hundreds of simulator sessions on this type, some with similar malfunctions.
Just one personal note : The last comment is from Gérard Feldzer. I have a doubt he has practiced UAS at cruise flight level, and exit from a full stall situation.
For the record, Feldzer is also the guy who, two years ago, was talking about Global Warming and Monster CB.
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Old 29th Jul 2011, 02:26
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Hello PJ2,

Thanks for your thoughtful reply.

The more I think about the "do nothing", the more I conclude that you were right when you wrote that Machinbrid was right that it is not the exact answer.

Originally Posted by PJ2

Machinbird
made a good point a while back in pointing out to me that "doing nothing" isn't the exact response and of course he was right.
Originally Posted by PJ2
airtren;
Yes, the phrase "do nothing" doesn't really describe what one really does and should do when a UAS event occurs. One does something, but the goal is level, stable flight
Knowing many of your posts, I know what you mean. But that is not the point.

Readers may come to this forum after a search hit, for a quick answer, and after a quick read, they don't come back to better understand, what is behind a certain statement.

I know well you didn't mean that, but the danger of the "do nothing" is that it gives the wrong message, that a pilot really does not have to do much, or know much, even when he gets the controls, as the A/C does everything by itself.

The "do nothing" resonates with a certain philosophy I disagree with, which is that modern airplanes don't require highly qualified and knowledgeable pilots. This is one of the reasons why a pilot when put in front of the controls, can loose it.

To me it's clear, that pilots of modern planes, need to be as good as the old days, old school pilots, PLUS also be technically so good as to understand well the various aspects of the new technologies used by the plane, so that any time can take best decisions.

A pilot in the cockpit needs to be like a Master/Champion chess player - understand well the situation on the chess board, and anticipate, see ahead, as many moves and combinations as possible.

A pilot, while the AP and A/THR are ON, and flight is in Normal Law, should follow closely the flight, particularly when the weather is problematic. He has to understand and anticipate all the possible scenarios that may develop, at any given point of time, based on a good knowledge of the A/C. and specifically the weaker points of the A/C. He needs be ahead of the game, ahead of all the other players, outside and inside the A/C, so that his reaction to anything that happens outside, or inside, is quick, to the point, very effective, and with immediate positive results.

When given the controls, he should be already aware of all of the conditions of the flight, before the control transition, and a quick assessment immediately after the transition, is only to confirm that all checks out. His subsequent actions should not be a guess, but rather a well known series of moves with a known ahead result, and driving to a known result.

Just an opinion,
airtren

Last edited by airtren; 29th Jul 2011 at 03:32.
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Old 29th Jul 2011, 03:35
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@Conf:

NO,

From 02:10:06 it was in Alternate 2 Law, after 02:10:16 this ALT 2 was latched.

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Old 29th Jul 2011, 03:38
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Cool

Hi,

A pilot, while the AP and A/THR are ON, and flight is in Normal Law, should follow closely the flight, particularly when the weather is problematic. It has to understand and anticipate all the possible scenarios that may develop, at any given point of time, based on a good knowledge of the A/C. and specifically the weaker points of the A/C. He needs be ahead of the game, ahead of all the other players, outside and inside the A/C, so that his reaction to anything that happens outside, or inside, is quick, to the point, very effective, and with immediate positive results.

When given the controls, he should be already aware of all of the conditions of the flight, before the control transition, and a quick assessment immediately after the transition, is only to confirm that all checks out. His subsequent actions should not be a guess, but rather a well known series of moves with a known ahead result, and driving to a known result.

Just an opinion,
airtren
Indeed ...
And in the case of the AF447 ... it's not really a surprise as it's many events of same nature on the same type of plane that happened in the years and months before the AF447 event .. well reported and published in many reports and testimonies of those concerned
So .. it must be normal that because the backup of experience and the care of Air France about the safety they have formed and warned their pilots about the scenario encountered by the AF447 .....
At least ... this is how it must be ..
Maybe the 3 interim BEA report will not show a so good picture ....
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Old 29th Jul 2011, 06:17
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airtren A pilot in the cockpit needs to be like a Master/Champion chess player - understand well the situation on the chess board, and anticipate, see ahead, as many moves and combinations as possible.
no chess master can look all day with all his skills to an automatic chess game/turnament to wait for the moment of a s/w bug

it was one of the fruits of this treat, to realize that even a champion needs training to hold his level (onbord training),

fly 10% of the time with your hands...
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Old 29th Jul 2011, 06:35
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Hi grity,

fly 10% of the time with your hands...
In over 7 years of AB FBW, I've never had any real time experience in ALT LAW. Plenty of "Direct Law" handling on previous Boeing & Lockheed types though. I bet it feels completely different to anything else I've tried.

How long did the PF have in order to practice that night before they stalled?
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Old 29th Jul 2011, 07:06
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Keeping it under control

Light, Moderate, or extreme -- doesn't really matter. What really matters is how prepared the pilot was to handle this unique situation. Hand flying in turbulence when everything goes out.
I am disturbed that it is not permissable to "hand fly" the aircraft in real life let alone the simulator/and or duplicate the "emergency" that they encountered in training.
I can't imagine a new guy, or inexperienced guy, being able to keep this thing under control under these conditions. Even if it was benign.

That's what training and testing is for. So far I see no evidence of it.
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Old 29th Jul 2011, 07:25
  #860 (permalink)  
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Originally Posted by mm43
We seem to have a difference of opinion over what happened following the AP/ATHR disconnect.
- yes, from the report of May, the 'difference' is that I am unable to ascertain exactly what sequence happened, while you appear to be able to! Anyway, 1230GMT today and hopefully we will know a lot more.

To summarise where I sit on AM 29 July:

The SW's following A/P disconnect are unexplained and a 'puzzle' - possibly due turbulence, possibly due to a low faulty IAS, possibly due to over-controlling in pitch or ???. It does not take a big pitch change at FL350 at that weight to push past the stall warning alpha - perhaps 'recovering' from a perceived drop in altitude?

The zoom climb, apparently 'unremarked' by either pilot, is a puzzle.

After the a/c 'flopped over' at FL380 and began to sink in a (possibly unrecognised) stalled condition - this is far less of a puzzle, due to their lack of experience of the 'impossible' full stall - as in PGF. My gut feeling is that from somewhere between 15 and 20k, they had insufficient altitude to recover anyway.

Why the AB software stops the stall warning when the a/c is deeply stalled defeats my logic.

My sincere hope, however, is that most FBW/software (particularly AB) pilots (and the training system) have had some quiet, contemplative and sobering thoughts over the last few months about what they need to think about and what the system might NOT do for them.
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