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-   -   AF 447 Thread No. 5 (https://www.pprune.org/tech-log/456874-af-447-thread-no-5-a.html)

bearfoil 3rd August 2011 21:12

Hi RBF, thanks.

Did you notice when PF mentioned "9000"? One second later he remarks:
"8000". That is 15,000 feet per minute! If he is accurate, (and most pilots are, at rating VSI with altitude) that is ~150 KNOTS vertical speed! Later, we hear "one would hope, as we are at 4000".

I am at a loss to understand their "nonchalance"?

speedbirdconcorde. Thanks for your reply Sir.

RetiredF4 3rd August 2011 21:22

DozyWannabe

Yellow : Elevator movement commanded
Green : THS begins following movement (autotrim)
Unfortunately the inputs are never held long or forcefully enough for the THS to make significant movements (remember it took over a minute of nose-up to go from cruise settings to full-aft), and the nose-down elevators last for 10-15 seconds at most - crucially they are immediately followed by a return to nose-up


could you point me to the indication, that the THS is moving? THS is the blue straight line on the bottom?

But by chance, how should THS move when after 15 sec. of SS ND the elevator peaks max at -15°NU (the magenta line)? Would the THS start moving prior elevators move to the ND range? How long is SS ND and in what magnitude required to get the elevator in a ND position?

ChristiaanJ 3rd August 2011 21:23


Originally Posted by henra (Post 6617374)
If you want to call something bogus it is the fact that they stopped above a certain AoA.

Let's not confuse the issue... they did not "stop above a certain AoA", but below a certain measured airspeed (< 60kts), because of the UAS.

What personally bothers me, is that the report does not stress sufficiently that the quoted "airspeeds" are those measured by the ADS and displayed in the cockpit and recorded on the FDR, and NOT the real airspeeds.

RetiredF4 3rd August 2011 21:23

Stall Recovery
 

A33Zab http://www.pprune.org/6616759-post1394.html
Stall Recovery
I know it has been posted several times before......

Stall Recovery FCTM.
ISSUE DATE: 15 JUN 10
It is the revised procedure (ISSUE DATE: 15 JUN 10). The old procedure was different with emphasize of gaining speed and maintaining altitude.
No sense to repaeat the new revised procedure again, everybody should know that one now, at least i hope so.

DozyWannabe 3rd August 2011 21:31


Originally Posted by airtren (Post 6617386)
They in fact, fall in the same category with the others, as the ability to recover or not recover does not change the character and source of the problem.

I'm not saying that the behaviour isn't problematic, I'm saying that I don't think that the return of the stall warnings is unambiguously triggered by the nose-down inputs. The only source that suggests that there was internal disagreement at the BEA is that one "La Tribune" article, and as such until I see some corroboration I'm going to be sceptical.

And if you think I'm being stubborn about press accuracy, you wait until you've spent a little more time on this board!


It is wrong to say that the failure of the SW to relay the correct information to the pilots does not matter because it was too late for them to recover anyway.
Again, I didn't say that it doesn't matter (I'm an engineer, I like to find things to fix!), I said I'm not 100% convinced it played a causal factor in this accident


It is bogus, because it was a Stall Warning giving the wrong indication relative to the PF actions
Based on the evidence of a single press article that almost certainly comes from within Air France (which as an entity would benefit financially and in PR terms from Airbus having to shoulder a larger percentage of the responsibility), I'm not buying that until I see some better traces - right now it looks ambiguous to me.


and relative to the state of the “a/c” relative to Stall.
That's fair - however as I said before, this is the only airliner to my knowledge that has been that far outside the envelope for that long, falling from that high - so at present it's not clear whether there is a deficiency in the stall warning design specific to the A330 (and by extension the entire Airbus FBW range), or whether this is something that needs to be examined on an industry-wide scale.


The message from the PF/NPF/CDB perspective was signaling a transition from NON STALL to STALL, when in fact the transition was from STALL to NON STALL.
Well, not quite - it was still stalled. If the nose-down inputs had been maintained before passing, say, 15,000ft on the way down then it might have stood a chance of coming out of the stall, but that's not a given. Remember that a stall warning is designed to activate before reaching the stall itself, so once it had picked up speed and the wings were unstalled, the warning would continue for a few seconds until it was out of the stall warning regime. That's not bogus, it's just a factor of the design.

Hypothetically, if they had successfully unstalled the wings, started bringing it back under control, but the extra couple of seconds of stall warning meant the difference between successfully pulling out of the recovery dive and crashing - would you be arguing deficient design on the part of the aircraft? Do you think Air France would?


You are missing the point, if you think, that the exact internal cause, or the mechanism of triggering the message matters. It does not matter, relative to the needs of the pilots, and state of the “a/c”.
It matters if you want to think about how to fix it. The guys who designed these systems didn't just slap it all together - everything they did had to fit a very strict set of criteria. There was a reason the logic was designed as it was and as such, any change is going to have to be considered very carefully.


In the same time, you’re making my point – if the internal mechanism was creating the condition in which the STALL Warning went silent...
Well, this is the thing - we've had two explanations doing the rounds - one, that the stall warning is inhibited by a software setting and the other is that once the airspeed has fallen that low that the AoA vane no longer functions. No doubt we'll find out if one, the other, both or neither is true in the coming weeks and months.


Which one would correspond to WSJ, and which NI? Media makes money from disseminating information, and scandals make money….But there is a gauge that each of us has, and in this case it is not the trash, that you could throw a Blanket Dismissal at.

This crash has been under investigation for more than 2 years now, and many following it had the ability to have a good enough understanding without being influenced by one press article, or another.
I don't know if you've noticed yet, but there is a small cabal of pilots, reflected in a number on here who have a kneejerk hatred of anything Airbus. This is in part based on press assertions made since the late '80s that Airbus was a prime mover in "taking pilots out of the loop". Some believe this was a deliberate attempt to deskill the job of airline pilot and undermine their livelihood. This is complete nonsense of course, but the press fed that rumour mill and made it what it is today, which is kind of ironic when one considers the short shrift most pilots give the majority of mainstream media articles on aviation.

I'm not that bothered about people who take the time to understand the issues, but when the press get it wrong, or chase a certain angle to get a juicier story, it pollutes the general public's understanding of the issues at hand, which is why you've still got a lot of people today thinking that the infamous 1988 crash of the A320 was caused because "the computer thought it was landing and overrode the pilot", or that "Airbus makes planes that use computers, Boeing still use good old-fashioned cables and hydraulics in their new designs". This bothers me because regardless of whether related to aviation or not, I can't stand people who should know better spreading misinformation.


What’s the today’s press and TV news in France? More of course... as there is more reaction by the parties involved....
Interestingly at the moment it's Air France that's making all the noise - Airbus seems to be keeping their cards very close to the chest at the moment.


So what if other planes don’t have it. Is the validation of other planes needed for Airbus?
It's helpful to stop the "If it ain't Boeing, I ain't going" crowd from crowing.

But ultimately the subject of Stall Warning is a prickly one - as far back as 1972 you have crashes caused in part because the pilots thought they were getting a false stick pusher activation, dumping the stick push and in doing so sealing the aircraft's fate.


There is one very simple, but also major reason to have it: Operating it in relative secrecy, when the results cannot be easily perceived by the entire team in the cockpit contributes to the type of AF 447 accident.
And there are equally plenty of major reasons not to, not least of which being what would happen if a back-driven sidestick was wired up in reverse during a critical stage of flight (which has happened). Others include the assistance in enforcing SOPs, crew roles and CRM given by having one person with their hand on the stick at any one time, the extra systems complexity and weight that setting up back-drive entails (the 777's backdrive system by its very nature has more potential points of failure as a result).

It has become a matter of personal preference really.


As we speak about this, I still have an unanswered question relative to the Airbus 330 stick functioning:

Is the control surface deflection proportional with the duration of a stick action in a certain position – if it is longer action in a certain position, is the deflection different than shorter action in that position?
In Normal Law you are commanding *rate* of movement in the axis rather than deflection. The FCU will do whatever it deems necessary with flight controls and thrust to get you the rate you're commanding. As you progress down through the laws, channels move from rate to deflection. In that case, I don't think the amount of time you hold the stick in a given position changes the deflection, but obviously the longer you hold the stick in position, the more time that deflected surface has to act, same as any other aircraft.

Lonewolf_50 3rd August 2011 21:33

bear, FFS, the transcript isn't parsed to fractions of a second, and he may have noted 8 grand in passing or nine grand in passing and approaching ten grand ... your division presumes a precision in your chosen "data points" that isn't in keeping with the accuracy you wish to assign to your RoD estimate.

If you make the denominator 0.75 seconds or 1.25 seconds to accomodate time to speak and delay between reading and speaking, what numbers do you arrive at? Keep moving your decimal fractions about until you get the numbers you are looking for?

Come on, bear, you know better than that! :=

Given that the FDR apparently produced some data points and readings around 10,000-11,000 fpm down (closer to the latter), such data is quite enough vertical velocity (or the vector along the negative z axis ) to evoke a grimace on anyone's face who is familiar with flying. There is no need to employ hyperbole and inaccuracy in attempt to craft further drama. There is drama aplenty without resorting to such. :=

JD-EE 3rd August 2011 21:44

airtren, in precisely what way were the stall warnings when the AoA was absurdly high in any way improper? The cessation of the stall warnings was improper; but, the warnings themselves were very proper. Or am I missing something rather serious?

bearfoil 3rd August 2011 21:47

You misunderstand. Perhaps utterly. My point is that on this flight deck there is just such a disregard for accuracy as you proclaim. So when you are in agreement, but by misunderstanding, it becomes FFS?

Lonewolf it is you who know better. Why announce two impressions of rate, and let it slide as if it matters not? Why announce it so close to the previous one, and let it "slide"? I submit you have a hair trigger when you read my posts. Read it again? In the interests of friendship?

Because we are to assume that the low level and rate are terrifying, and yet remain seemingly unimportant to the crew? Folla?

A33Zab 3rd August 2011 21:48

Stall warning:
 
Triggering a Stall Warning: "STALL STALL" is not the difficult part in the logic.

The challeging part is to trigger a stall warning when it is appropriate to do so
(for the flight condition & A/C Config.) and to prevent the spurious stall warnings.

It requires 25 pages of logic in the FWC ECAM system logic manual.

I'm not here to defend AIB, they can add another ECAM page logic if you like, but would that have made any difference after 54 sec of continuous warning?

This is how the game -to blame- is played.

mm43 3rd August 2011 21:51

CJ;

What personally bothers me, is that the report does not stress sufficiently that the quoted "airspeeds" are those measured by the ADS and displayed in the cockpit and recorded on the FDR, and NOT the real airspeeds.
Exactly, ... and if they had done so they would have provided the reason why they are different.

Lonewolf_50 3rd August 2011 21:56

bear, as a friend: please go back to the alleged mathematical operation you presented to us, and your choice of numerator and denominator, and consider how you derived those data points. Compare that sourcing to the FDR which BEA roots its estimates and data from.

Then consider the the FDR analysis came up with a RoD between 10,000 and 11,000 FPM (I suspect it varied early on, and stabilized (per Grity and henra's posts a few threads ago) as the bird descended into denser air and friction came into play, and an approach to terminal velocity. I am within 10% in that error band. I suppose I could go and find the 10,098 or 10,988, or whichever figure is cited as ultimate RoD, and please my pedantic little old self. No drama. henra I thin it was pointed out that the RoD would vary based upon air density, a couple of threads ago.

To arbitrarily add a 40% bonus for dramatic effect on dubious arithmetic grounds doesn't help in understanding.

So, my tone might have been edgy, but I know you've been around long enough to know how number manipulation works. (Heh, you have even complained about such things in various threads ... ;) )

HazelNuts39 3rd August 2011 21:57

Stall warning drop-out
 
Let's put this into perspective. Certification requirements, airplane systems design and airline pilot's training primarily seek to avoid stalling the airplane. Limiting myself to system design, there are first of all the various high-AoA protections in normal law. In the fairly remote failure condition of alternate law the only protection left is stall warning. Its function is to warn the pilot that AoA is exceeding a threshold close to AoA-stall, but sufficiently below it to allow the pilot to avoid stalling. At high Mach it is set to stay below the onset of buffet, which provides additional margin to the stall, and its function is amplified by the occurrence of aerodynamic buffet. In the words of the regulation (which doesn't apply in abnormal systems configurations) stall warning must continue until the AoA is reduced below the threshold at which it is triggered. It would seem that in almost all cases the system will do just that. The only case where it will not function as intended is when the stall warning is ignored, and nose-up commands are maintained, causing the AoA to increase to values (>40 degrees) at which the sensed airspeed is so corrupted that the AoA signal itself is considered unreliable or invalid.

P.S.

Originally Posted by grity
what can be a reason for UAS until the ice dedectors has no ise detected...

Ice detectors detect the formation of ice by freezing of liquid water, which in all probability was not present in the conditions of AF447. They work in cycles: unheated while collecting ice, heated to shed the ice. Ice particles do not adhere to non-heated surfaces, and are therefore not detected.

JD-EE 3rd August 2011 21:58

DozyWannabe - on page 114 look down to the 8th set of graphical elements, dark green titled "ASSIETTE (>D- A cabrer)[DA]". What is it?

When I try to translate it this seems to be an aircraft pitch trace. If so, at many times the PF had full nose up on the elevator the plane had a significant, 10 degrees or more, nose down attitude.

So I'd like to know what that line's title really means.

Please!

A33Zab 3rd August 2011 22:07

@JD-EE and others who want to trace......
 
If you want to trace and compare, don't forget to take the accelleration into account.
The - accelleration normale* - is the feedback (besides elevator servo deflection) to the FBW pitch channel.

* well not completely sure, awaiting english version.

DozyWannabe 3rd August 2011 22:13


Originally Posted by RetiredF4 (Post 6617547)
could you point me to the indication, that the THS is moving? THS is the blue straight line on the bottom?

You need to be zoomed right in, but you can see movement in the THS line after an elevator movement of any size. Unfortunately, due to the low resolution of the image in the PDF it only shows as a series of 1-pixel notches in the line, but there is definitely a correlation between elevator activity and those notches at that point. Earlier in the sequence , those notches appear just prior to movement of the THS in reaction to elevator movement. Even a small amont of elevator movement seems to trigger them, but the elevator commands need to be held for a significant amount of time before the THS will respond in anything other than increments which are barely perceptible at the resolution in which the graphs are presented.


But by chance, how should THS move when after 15 sec. of SS ND the elevator peaks max at -15°NU (the magenta line)? Would the THS start moving prior elevators move to the ND range? How long is SS ND and in what magnitude required to get the elevator in a ND position?
In all honesty I don't know, but if you look on page 111 of the French report, you can see the sidestick traces, directly below which is the elevator response, and directly below that is the THS, which gives a nice representation of how the autotrim works. Notably, the big THS movement happens during a time in which some quick "blips" of nose-down are made, but the overriding trend from the sidestick and elevators is for nose-up, and so the THS follows that.


Originally Posted by ChristiaanJ (Post 6617550)
What personally bothers me, is that the report does not stress sufficiently that the quoted "airspeeds" are those measured by the ADS and displayed in the cockpit and recorded on the FDR, and NOT the real airspeeds.


Originally Posted by mm43 (Post 6617596)
CJ;Exactly, ... and if they had done so they would have provided the reason why they are different.

Well, this is an *interim* report after all, and in the FDR traces, below the indicated airspeed (both "conventionelle" and "I.S.I.S"), they have included the ground speed trace, which gives a better picture of what the actual speed would have been.

@JD-EE - I'm pretty sure that "Assiette" can refer to pitch or trim, but in this case I think it means pitch. If it is a valid trace then yes, the nose fell down, but I suspect not in a controlled manner. In any case, the THS position, along with that of the elevators meant that as soon as the nose was down it would immediately come back up due to aerodynamic forces.

mm43 3rd August 2011 22:18

JD-EE;

ASSIETTE (>D- A cabrer)[DA] = Attitude trace, and you are right regarding the excursions into ND. Also check the Stall Warning trace below!

bearfoil 3rd August 2011 22:19

What is bear getting at? Merely this. The SW was alive for ~54 seconds, seemingly without effect re: crew actions. The loss of altitude was grave, the VSI reads were alarming, and yet there is a definite disregard for hard data to effect a recovery FROM STALL. The focus may not have been on STALL. Because we know what happened ( yet continue to gripe and argue about the hard data!), does NOT mean that is what the crew were addressing as their immediate challenge. The CAPTAIN is unsure about whether to PUSH or PULL!



Now all this is from a redacted and selective release of conversation absent tone, inflection, and strict sequence. The only explanation relative to 447's demise based on BEA has to do with how moronic and clumsy these gents acted. I do not for a second believe that to be the case. Instead, I choose the other option, one that makes more sense based on BEA and hopefully their honest representations of the Data, and not an attempt to slander the crew. A DIVE. TOO MUCH SPEED. A reliance on the g protections available in ALTERNATE LAW 2. The only thing they could not get is why she refused to climb when commanded, screw the STALL HORN.

rant, fading into........

@Lonewolf. Finally, It matters less than a gnat's whisker whether you 'get' or I 'get'. Our disagreement is nada. What matters is what THEY thought. I am not seeking drama, I am asking why would the crew speak twice of Altitude, than finally, "hoping a Pull Up, we are at 4000". ? I'm trying to wear their moccasins, in an effort to understand: Why the "Nonchalance"?

What matters is what they think of what THEY spoke! "@9000......@8000"

one second after the other. Does one of them not 'get' the VSI, and someone is trying to REMIND? At 8000, than 4000 feet?

To me, and it is a GUESS, it means they are worried about Overspeed, which means at any split second they can start a successful recovery, even at 4000 feet. No NEED to reload the wings, spend 10000 feet and then have to worry about tearing the wings OFF.

That is why, In my opinion, they were not speaking STALL!

As in: Captain : "N'est-ce pas possible!!" "****in A, we're STALLED"

JD-EE 3rd August 2011 22:22

Lone - "I empathize."

To say the least. Those guys are under incredible pressure. And based on what I see here with people apparently missing important clues they must be working VERY hard.

GarageYears 3rd August 2011 22:26


STALL WARNING
Quote:
Excerpt from BEA - 3 August 2011 ...

Finally, it should be noted that the warning sounded uninterruptedly for 54 seconds after the beginning of the stall, without provoking any appropriate reaction from the crew.
That statement can not be misconstrued. The crew never acknowledged the Stall Warning. The exception could be that they reacted to it inappropriately once stalled.
PEI_3721:

As much as new designs might enhance the salience of a warning, if the crew’s mental model has rejected the warning as being false, inappropriate, or unwarranted in the situation as perceived, then enhancement is of little point.
Remember ‘shut up gringo’ ?
Some other aircraft have, and for good reason, a stick shaker and stick pusher.
Now an electronic version of that sounds very simple, particularly if it repositions trim. However, remember that a ‘rush’ makes for poor law – similarly quick system changes and redesign might have pitfalls elsewhere.
Thus, let the designers think through their system; they probably evaluated such an option in the initial design - certification case to show why it is not required.
Finally all parties must ensure that any change fixes the problem, but do we actually know what the problem is, except perhaps human limitations in perception and understanding.
I am quite familiar with both stick-shaker and stick-pusher, however I suspect you are not really accepting that the system designers have generally NOT considered the region deep into a stall. Certification tests are carried out up to and approaching a stall, but never stalled. Trying that in a large transport category aircraft is not recommended or tested (except perhaps using computer modeling).

The stall warning systems currently on the aircraft are therefore designed as preventative devices - i.e. if you are hearing this, then things are starting to go wrong, so perform the appropriate actions.

Consider whether, in the normal course of aircraft operation, it seems likely that an aircraft would be *flying* with an IAS of 60knots and a stall-value AoA? Such a realm is easy for the armchair quarter-back to criticize... "why shut off the stall warning when the IAS drops below 60 knots" ---> because such a condition was/is inconceivable for 'normal aircraft operations'.

But my suggestion a page or so posts back now, was to introduce a new warning, not just an aural, but a bloody great block of text flashed across all glass displays in the cockpit every 5 seconds or so, suppressing all other warnings that may or may not be going off. "AIRCRAFT STALLED, AIRCRAFT STALLED, REDUCE AoA!"

As some other contributor noted, it's not very helpful hearing a "pull-up, pull-up" warning if you're fighting a stalled aircraft - if you're stalled with an AoA of 60+ degrees and vertical speed of -10kft/min then it would certainly not help much now would it?

In the Buffalo crash the pilot pulled through the stick-shaker, but in that case there were issues that were arguably deeply rooted at a skill level.

A simple question:

Would something per my suggestion - "AIRCRAFT STALLED, REDUCE AoA!" flashed in red text on the glass displays have alerted the AF447 crew that they were stalled? - triggered from AoA and V/S?

There are two possible answers - "NO" and "MAYBE" - if it is the latter then proceed with a human factors study, etc. I am not proposing a rushed introduction.

My personal opinion is we, as humans, are bombarded with technology today, but look at the trending.... we are moving away from email to Facebook, and T w i tter (with a limit of 140 characters per message), we TXT msg each other in short-hand code, our attention span is shrinking. When things go wrong we tunnel vision, shutting down our senses - therefore at moments of critical decision making we NEED the available technology to prioritize our input stream for us.

henra 3rd August 2011 22:27


Originally Posted by ChristiaanJ (Post 6617550)
Let's not confuse the issue... they did not "stop above a certain AoA", but below a certain measured airspeed (< 60kts), because of the UAS.

Agreed !
Was imprecise on my part.

Although the measured Airspeed was very likely a consequence of the AoA exceeding certain values leading to collapse of the flow around the pitot and not so much representing the real Airspeed.

JD-EE 3rd August 2011 22:28

Dozy "Well, this is the thing - we've had two explanations doing the rounds - one, that the stall warning is inhibited by a software setting and the other is that once the airspeed has fallen that low that the AoA vane no longer functions. No doubt we'll find out if one, the other, both or neither is true in the coming weeks and months."

Don't forget that with a very high AoA the airspeed indication is VERY spurious. You get some ram air into the drain and you get reduced air into the business orifice of the pitot. The AoA vane was probably working. And when the nose was 10 degrees down would have clarified the stall warning by showing the AoA was still way too high to fly.

(I suspect it would be wise to get that green line I've started harping about into your graph for thinking purposes. It may explain some of the cockpit psychology.)

RetiredF4 3rd August 2011 22:32

@DozyWannabe
 

DozyWannabe
In Normal Law you are commanding *rate* of movement in the axis rather than deflection. The FCU will do whatever it deems necessary with flight controls and thrust to get you the rate you're commanding. As you progress down through the laws, channels move from rate to deflection. In that case, I don't think the amount of time you hold the stick in a given position changes the deflection, but obviously the longer you hold the stick in position, the more time that deflected surface has to act, same as any other aircraft.
Could you reflect on my post post1433.html, please?
After your above statement i´m the more interested.


DozyWannabe
Quote:
Yellow : Elevator movement commanded
Green : THS begins following movement (autotrim)
Unfortunately the inputs are never held long or forcefully enough for the THS to make significant movements (remember it took over a minute of nose-up to go from cruise settings to full-aft), and the nose-down elevators last for 10-15 seconds at most - crucially they are immediately followed by a return to nose-up
could you point me to the indication, that the THS is moving? THS is the blue straight line on the bottom?

But by chance, how should THS move when after 15 sec. of SS ND the elevator peaks max at -15°NU (the magenta line)? Would the THS start moving prior elevators move to the ND range? How long is SS ND and in what magnitude required to get the elevator in a ND position?

If i read your above statement from post1436.html correctly, then elevator should be in "deflection channel" as you name it? Why does the elevator move only to 15°NU, even distinctive ND SS inputs where present (also not over prolonged time).

I hope, i didn´t get on your ignore list.

bearfoil 3rd August 2011 22:34

Hi Dozy. I think those Notches are what I took to be sawteeth, earlier.

"Serrata" if you will. I noticed two things. First I believe you are exactly right, each notch shows a 'command'. Also, they register as one second intervals on the timeline. What do you think?

JD-EE 3rd August 2011 22:37

Dozy "@JD-EE - I'm pretty sure that "Assiette" can refer to pitch or trim, but in this case I think it means pitch. If it is a valid trace then yes, the nose fell down, but I suspect not in a controlled manner. In any case, the THS position, along with that of the elevators meant that as soon as the nose was down it would immediately come back up due to aerodynamic forces."

Good, we're that far. Notice the correlation between the PF's nose up and the nose down the aircraft executed. What would that do to the PF's mind?

As a side not I vaguely remember some discussion back in 2009 about the aircraft's behavior if airspeed really does decrease well below stall. It might even have been in the context of place the plane in the air at zero airspeed. The conclusion was that the swept back wings would make the nose go down. The data presented from the FDR seems to indicate this is exactly what the plane did. ("Good plane", as she pats it on its metaphorical head.)

Could the pilot have had a problem admitting the plane was stalled even with the nose pitched down 10 degrees? It is very clear to me that the pilots were both pretty much mentally rejecting that #$)**#@_) stall warning. (Imagining irritated profanity in their thoughts.)

edit
(Is incidence emis par... the AoA? It looks like it. That would have been a GIANT clue.)

JD-EE 3rd August 2011 22:42

bearfoil, look at the graphs again. Is the real root cause the lack of a real AoA indication in the cockpit? That is rather hard for pilots to mentally reject. The AoA warning was easy for them to reject after training that it CAN happen spuriously. There is a hardware (design) error for you to consider.

DozyWannabe 3rd August 2011 23:03


Originally Posted by JD-EE (Post 6617697)
Good, we're that far. Notice the correlation between the PF's nose up and the nose down the aircraft executed. What would that do to the PF's mind?

The PF's inputs towards full nose-up begin at 2:11:40 and he's back against the stops at 2:11:42. The nose-down pitch doesn't begin until 2:11:45 and reaches 10 degrees nose-down (the lowest point it will ever reach) at approx 2:11:55. I might be being daft, but I see no correlation.

On top of that, if I pulled hard back and the aircraft's response was to pitch down in short order, recall of my Air Cadet days would suggest I might be stalled.

Am I missing something?

bearfoil 3rd August 2011 23:05

Hi JD-EE, The real root cause of what? Look, I think it is fascinating, this discussion re: AoA, Culture, and snarky repartee, ad nauseum.

The fact remains, the stage was set at AutoPilot disconnect, it becomes ever more clear. If the pilots were right, they would have recovered, and if they had grokked STALL soon enough, they would have recovered. But they were wrong, and kept expecting NU to solve their overspeed problem. It is certain. (my opinion only)

Three qualified Pilots ignore STALL WARNINGS and input near constant NOSE UP. Not an Approach to STALL recovery, (This is Not Colgan for silly sakes), and their mistake is clear to the hangers on, after the fact, Regardless the conclusion!

The initial PF saw Nose Up, Roll Left. The last one, Also PF saw Nose Up, Roll Left. None of the Pilots, NONE, grokked STALL.

Are you Pilot? High altitude, cruising, 500knots TAS. AP quits, must hand fly. Too much hand, a climb, a big climb. After Topping out, immediately see huge loss of altitude, and noise like you would not believe. Having heard one "bogus" fart from 447, I have huge airstream din, huge and continuing LOA, and I say "I think we have crazy speed!" They've seen UAS, so he isn't saying "Duff speed" he is saying "Way Fast".

There is no other way to see this, except to claim the boys were idiots.
That is perhaps the looniest opinion in two years of being here. Because there are some armchair pilots here (guilty) and pilots being who they are, everybody has a handle on it. The case is all but closed.

Nonsense.

See #1448

Thanks for all your input, I've learned much from you fund of expertise, and your way of presenting it.

takata 3rd August 2011 23:21

Hi JD_EE,

Originally Posted by JD_EE
we've had two explanations doing the rounds - one, that the stall warning is inhibited by a software setting and the other is that once the airspeed has fallen that low that the AoA vane no longer functions.

There is only one single and simple explanation:
If no alpha_probe real failure is declared and no particular phase inhibition is declared:
1) - Stall Warning alarm is working provided that at least one ADR_alpha_channel is valid. (e.g. turning OFF all ADRs imply that Stall Warning alarm is totally lost).
2) - ADR_alpha_channel is valid provided that its own ADR_airspeed_channel is > 60 kt.

Consequently, if all three ADR_airspeed_channels are < 60 kt => case 1) Stall Warning alarm is lost.

But, this may become circular:
If alpha increases and is reaching a very high level, pitot_probes starts to under-read airspeed (due to angle of airflow related to ram tube orientation). At one point, alpha can be so high that airspeed is falling under 60 kt, causing alpha_probes to display NCD (invalid) values, causing the complete loss of Stall Warning alarm.

Consequently, the measured airspeed could be < 60 kt while aircraft is actually flying at 100+ kt but at very high alpha. Hence, high alpha will cause invalid alpha and Stall warning alarm will drop off at much higher airspeed than designed.

mm43 3rd August 2011 23:21

@bearfoil;

You are dealing with a "cultural problem", and it is indicative of some attitudes that have developed over the last 40 years - or so.

This excerpt from an email, received from a French lady a few hours ago, may provide an insight into what I suspect you already know.

Do you know much about french-style education post 1968? Taking of initiatives, thinking for oneself, individual responsibility, curiosity of all things, CHECKING facts - have been deliberately educated out, the automated response and the supposition are supreme, the group action favoured. A few years ago government announced its intention of trying to return to the responsible individual attitude; put back the "jagged edge" which is the glue safeguarding democratic society, but which the unthinking have difficulty encompassing. It will be hard with more than two generations brainwashed. And then there are the "grandes écoles".

My Lebanese (but passionately pro de Gaulle) companion used to say of the French: "all the gear and no action".
Now, don't get me wrong! I'm not starting a "cultural" war.:ok:

3holelover 3rd August 2011 23:23

Bearfoil,
With respect,

Originally Posted by Bear
Are you Pilot? High altitude, cruising, 500knots TAS. AP quits, must hand fly. Too much hand, a climb, a big climb. After Topping out, immediately see huge loss of altitude, and noise like you would not believe. Having heard one "bogus" fart from 447, I have huge airstream din, huge and continuing LOA, and I say "I think we have crazy speed!" They've seen UAS, so he isn't saying "Duff speed" he is saying "Way Fast".

The man with his hand on the stick [PF] should have realized early on that, if that were the case, the aircraft would respond MUCH differently to his inputs. I seriously doubt that many pilots I've ever known could mistake the one for the other [stall - overspeed] after even a moment at the stick, even while blind.

Also, there were not 3 pilots mistaking that for most of their fall... only the one. At best the PNF had a few moments to explore it himself, but not the Capt.

In an earlier post you alluded to people calling them morons... I haven't heard that from anyone yet, have you? I doubt even the most myopic among us would deny that at worst, they were at the mercy of their training, SOP's and a damned difficult situation.

A33Zab 3rd August 2011 23:41

In english
 
English version

HazelNuts39 3rd August 2011 23:43


Originally Posted by takata
If alpha increases and is reaching a very high level, pitot_probes starts to under-read airspeed (due to angle of airflow related to ram tube orientation).

Correct, but don't forget that static pressures are affected also, reading high. Pitot minus static can become negative in extreme cases, as mentioned in one of the BEA reports.

boguing 3rd August 2011 23:52

Bearfoil
 
This will get deleted soon, I'm sure.

Bearfoil might be a Civil Engineer. They all fell asleep during Fluid Dynamics lectures on my degree course.

Not many months ago he was certain that the tail had fallen off. Mainly because it was made in Europe. We don't do glue as well as the Americans.

Put him on your ignore list. Worked for me.

The frustration rises when I see him quoted.

Hope this doesn't get me banned?

xcitation 3rd August 2011 23:54

Bear
IMHO they were convinced of overspeed. Nose up, give me all the stick back you got, why does she stop at pitch +16 deg, I want more. Deploy spoilers. Idle the engines. Crazy speed.

What made all three believe in overspeed. To the extent that they can ignore stall warnings, the UAS procedure, ignore the high pitch, low IAS, low ground speed, ambient noise changes. Was it the deceleration giving them the perception they were in a dive and PF thought the attitude indicators were wrongly showing +16.
Something made them all convinced of it. Did the PFD show the red black overspeed ladder?
Even a sceptic has to wonder if there was something else they saw that we do not.
I might believe one or maybe 2 had it totally and insanely wrong but not all 3 pilots.

DozyWannabe 3rd August 2011 23:55


Originally Posted by RetiredF4 (Post 6617684)
If i read your above statement from post1436.html correctly, then elevator should be in "deflection channel" as you name it? Why does the elevator move only to 15°NU, even distinctive ND SS inputs where present (also not over prolonged time).

I can't answer for sure, but I have a feeling that the trace in the FDR describes elevator position relative to THS position. I hope someone else will confirm/refute this, but if you compare the SS traces, the elevator traces and the THS traces it seems to make sense.


I hope, i didn´t get on your ignore list.
Franzl, I've never put a single person from a single forum of which I am a member on ignore list in my life! I'm quite capable of mentally filtering out waffle if I need to, and I've always operated under the assumption that even people who get on my nerves probably have something to teach me, so it would be ignorant of me to ignore them. :)

And even if I did - you're a long way from anywhere near the list that I'd contemplate putting on ignore!

takata 4th August 2011 00:07

Hi HazelNuts39,

Originally Posted by HazelNuts39
Correct, but don't forget that static pressures are affected also, reading high. Pitot minus static can become negative in extreme cases, as mentioned in one of the BEA reports.

Yes Sir! ... high alpha affects every probes, including, static and alpha probes!
Hence, airspeed is twice affected (did you try to derivate aircraft actual airspeed from ground speed and other parameters to see at which estimated (true) value airspeed was reading under 60 kt ?)
And V/S is also affected (obvious from graph)... and somewhat baro altitude...

This limitation of +60 KCAS for alpha validity would be due to good reasons, but I don't know which one... it seems to me easier to inhibit this alarm during specific phases when you don't need it (ground, rolling...) than doing it this way in relation with airspeed.

Shadoko 4th August 2011 00:36


Originally Posted by Shadoko
Think correct translation in English of aeronautic use of "gauchissement" is "wing warping".

Originally Posted by ChistianJ
Sorry... but you're wrong, unless you're talking about the "Wright Flyer" and aircraft from that age..
It may well be the logical original 'source' of the term in French aeronautical terminology, but today it just refers to "roll" or "roll angle".


Thank you for the correction. The word have been discussed without clear answer, so I tried with dictionaries : no knowledged people under hand ("lost" in the meddle part of France).
I understand you have a very fine knowledge of aeronautical wording, both French and English. If you do not mind, could you say what you think of AF447 conversations as they are transcribed (wording, technicity,...)? I am very surprised by them (but have no knowledge at this), even if there were an understandable "stress". When compared with those in the cockpit of the Airbus which landed on the Hudson (supposing the YouTube retranscription is valid: wwwDOTyoutubeDOTcom/watch?v=tE_5eiYn0D0). And if you don't want, for any reason, to write about that, I would understand. Thanks anyway.

HazelNuts39 4th August 2011 00:40


Originally Posted by xcitation
What made all three believe in overspeed.

The altitude tape scrolling down at an unusual rate, the 'vario' at the negative peg?

takata 4th August 2011 00:57

Hi mm43,

Originally Posted by mm43
This excerpt from an email, received from a French lady a few hours ago, may provide an insight into what I suspect you already know.

Your French lady's statement and her view on French "society" seems seriously connoted!
It should be taken it with a (big) grain of salt, excepted, maybe, the quote from her Lebanese (nonetheless pro-De-Gaulle) companion!
:}

PEI_3721 4th August 2011 01:17

GarageYears, re #1451
“I suspect you are not really accepting that the system designers have generally NOT considered the region deep into a stall.”

Quite possibly; particularly in the manner in which it is being discussed in this thread.
Certification considers a locked-in deep stall from aircraft geometry aspects, as with a ‘T’ tail, but the A330 stall appears to be ‘locked-in’ due the control system, predominantly trim holding a pro-stall condition. Certification, be it right or wrong, considers that the control condition should not be considered, or if so it is recoverable by crew action


Certification flight tests will examine all aspects of an aircraft’s stalling characteristics, including searching for a ‘deep stall’ on geometrically susceptible aircraft. However, the tests may not evaluate an extreme mis-trimmed condition outside of the normal flight envelope.

Modern designs aircraft have moved toward ‘preventative’ systems. Some stick pushers which I have flown should not to be argued with - high forces, but as in your example, a fearful pilot can overcome such systems. Thus the digital trend is towards avoidance / limiting, but as is being discussed this may not cover all non-normal conditions.
The probability of protective systems failing together with stall AOAs and mis-handling the aircraft clearly exceeds the probabilistic certification assumptions. This is ‘black-swan’ territory where the industry depends, either consciously or not, on the human rescuing the situation.
We celebrate many notable successes. Unfortunately we have to suffer failures; this hurts our pride, beliefs, and our professional standards, and correctly we search for a solution, but as I questioned earlier, do we understand the problem – all aspects of the problem.


I agree that we are bombarded by technology, automation, etc, but adding more to ‘encase’ the pilot will only increase the complexity of an already over complex operational environment.
If technology is to help then it should be in a form as you suggest, releasing the pilot from the technological cage and encouraging cognitive excellence; but if this is achieved via technology, we still have to consider what happens when that technology is unavailable.
In such circumstances the human is still best placed to evaluate and judge the situation; but the human might benefit from some generic skills training to improve awareness, managing surprise, and knowledge recall; aspects of higher professional standards perhaps.


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