AF 447 Thread No. 5
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Is it just my perception or is it that both FO's talk in vague terms. Lots of ambiguous references to up/down and to indicators. At one point is there confusion in what they are conversing about? I am not a native french speaker however at best the terminology sounds imprecise. Perhaps AF pilots have a verbal short hand? Did the pilots suddenly down shift from precise technical language only at the onset of problems?
Maybe just a red herring, but don't forget that the French also gesticulate (hands, general body language) a lot more - indeed a video would have been useful.
Another issue, as we see in recent posts, is that French has a plethora of different technical terms, which often (but not always...) mean exactly he same thing.
"Gauchissement" and "roulis" both refer to roll, either left of right (and NOT to "left rudder", a mistake that's already crept into several posts).
Same for "tangage" and "assiette" which both refer to pitch.
I should know.... I spent about half my life in France, and most of that in the aviation industry.... I still remember being baffled, when I first arrived here, by the confusing use of so many near-synonyms in documentation and reports.
Originally Posted by Shadoko
Think correct translation in English of aeronautic use of "gauchissement" is "wing warping".
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".
Please mis-trust so-called "technical dictionaries" like the plague.....
I still remember having to switch abrupty from French "Concorde" terminology to "helicopter" terminology (change of occupation, another story...). The "dictionaries" and "vocabularies" were less than useless. Asking a collegue was the usual solution....
CJ
Last edited by ChristiaanJ; 3rd Aug 2011 at 16:47.
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mm43 After your vertical red line, the roll position and heading direction show close relationship. (Actually, throughout, the relationship is clear.) So we see clearly an Heading change(s), relative to Roll. This is not indicative of Pilot overcontrol, imho, it shows rather an unstable a/c in the Lateral axis, as well as the Longitudinal. For the record, My reasoning is that to effect a change of direction of several degrees takes time, indicating rather a chronic condition than an acute one.
I have a 'gut-feeling' as well. I am confident in the Pilots, and the a/c. Those traces tell much, they tell the truth, and they have no axe to grind.
I do not mind in the least being upbraided, ignored, or marginalized. I do not have the credentials to dismiss anything, even myself.
I think it arrogant when sweeping statements are made by pros. I have an excuse.
My first reaction was to assume Pilot induced ROLL.
It is not, imo. The a/p had a similar pattern, at the end of its authority.
More than anything said of the excellent commentary, It is regrettable that esteemed posters would simply dismiss an artifact as irrelevant, or unimportant. Especially w/o supplying a reason, with explanation.
At first blush, the stick stirring and ROLL problems might seem to condemn the PF.
At every turn, to me, there is a simple explanation. It may have bearing it may not. I carry it with me as I read, and I think people are wandering too far into a blanket condemnation of the Pilot Crew. Also of the a/c.
Both sides are carrying and wearing their bias openly, and it seems objectively to me to be foolish.
I have a 'gut-feeling' as well. I am confident in the Pilots, and the a/c. Those traces tell much, they tell the truth, and they have no axe to grind.
I do not mind in the least being upbraided, ignored, or marginalized. I do not have the credentials to dismiss anything, even myself.
I think it arrogant when sweeping statements are made by pros. I have an excuse.
My first reaction was to assume Pilot induced ROLL.
It is not, imo. The a/p had a similar pattern, at the end of its authority.
More than anything said of the excellent commentary, It is regrettable that esteemed posters would simply dismiss an artifact as irrelevant, or unimportant. Especially w/o supplying a reason, with explanation.
At first blush, the stick stirring and ROLL problems might seem to condemn the PF.
At every turn, to me, there is a simple explanation. It may have bearing it may not. I carry it with me as I read, and I think people are wandering too far into a blanket condemnation of the Pilot Crew. Also of the a/c.
Both sides are carrying and wearing their bias openly, and it seems objectively to me to be foolish.
Last edited by bearfoil; 3rd Aug 2011 at 14:24.
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Stall Recovery
I know it has been posted several times before......
Stall Recovery FCTM.
ISSUE DATE: 15 JUN 10
STALL RECOGNITION
The flight crew must apply the stall recovery procedure as soon as they
recognize any of the following stall indications:
‐ Aural stall warning
The aural stall warning is designed to sound when AOA exceeds a given
threshold, which depends on the aircraft configuration and Mach number.
This warning provides sufficient margin to alert the flight crew in advance
of the actual stall even with contaminated wings.
‐ Stall buffet
Buffet is recognized by airframe vibrations that are caused by the non-stationary
airflow separation from the wing surface when approaching AOAstall.
When the Mach number increases, both the AOAstall and CL MAX will decrease.
The aural stall warning is set close to AOA at which the buffet starts.
For some Mach numbers the buffet may appear just before the aural stall warning.
STALL RECOVERY
‐ The immediate key action is to reduce AOA:
The reduction of AOA will enable the wing to regain lift.
This must be achieved by applying a nose down pitch order on the sidestick.
This pilot action ensures an immediate aircraft response and reduction of the AOA.
In case of lack of pitch down authority, it may be necessary to reduce thrust.
Simultaneously, the flight crew must ensure that the wings are level in
order to reduce the lift necessary for the flight, and as a consequence, the required AOA.
As a general rule, minimizing the loss of altitude is secondary to the
reduction of the AOA as the first priority is to regain lift.
As AOA reduces below the AOAstall, lift and drag will return to their normal values.
‐ The secondary action is to increase energy:
When stall indications have stopped, the flight crew should increase thrust
smoothly as needed and must ensure that the speed brakes are retracted.
Immediate maximum thrust application upon stall recognition is not appropriate.
Due to the engine spool up time, the aircraft speed increase that results
from thrust increase, is slow and does not enable to reduce the AOA instantaneously.
Furthermore, for under wing mounted engines, the thrust increase
generates a pitch up that may prevent the required reduction of AOA.
When stall indications have stopped, and when the aircraft has recovered sufficient energy,
the flight crew can smoothly recover the initial flight path.
STALL WARNING AT LIFT-OFF
If the aural stall warning sounds at liftoff, the flight crew must fly the
appropriate thrust and pitch for takeoff in order to attempt to stop the
aural stall warning and ensure a safe flight path.
The flight crew applies TOGA thrust in order to get the maximum available thrust.
Simultaneously, the pilot flying must target a pitch angle of 15 ° and keep
the wings level in order to ensure safe climb.
Then, when a safe flight path and speed are achieved, if the aural stall
warning is still activated the flight crew must consider that it is a spurious warning.
Stall Recovery FCTM.
ISSUE DATE: 15 JUN 10
STALL RECOGNITION
The flight crew must apply the stall recovery procedure as soon as they
recognize any of the following stall indications:
‐ Aural stall warning
The aural stall warning is designed to sound when AOA exceeds a given
threshold, which depends on the aircraft configuration and Mach number.
This warning provides sufficient margin to alert the flight crew in advance
of the actual stall even with contaminated wings.
‐ Stall buffet
Buffet is recognized by airframe vibrations that are caused by the non-stationary
airflow separation from the wing surface when approaching AOAstall.
When the Mach number increases, both the AOAstall and CL MAX will decrease.
The aural stall warning is set close to AOA at which the buffet starts.
For some Mach numbers the buffet may appear just before the aural stall warning.
STALL RECOVERY
‐ The immediate key action is to reduce AOA:
The reduction of AOA will enable the wing to regain lift.
This must be achieved by applying a nose down pitch order on the sidestick.
This pilot action ensures an immediate aircraft response and reduction of the AOA.
In case of lack of pitch down authority, it may be necessary to reduce thrust.
Simultaneously, the flight crew must ensure that the wings are level in
order to reduce the lift necessary for the flight, and as a consequence, the required AOA.
As a general rule, minimizing the loss of altitude is secondary to the
reduction of the AOA as the first priority is to regain lift.
As AOA reduces below the AOAstall, lift and drag will return to their normal values.
‐ The secondary action is to increase energy:
When stall indications have stopped, the flight crew should increase thrust
smoothly as needed and must ensure that the speed brakes are retracted.
Immediate maximum thrust application upon stall recognition is not appropriate.
Due to the engine spool up time, the aircraft speed increase that results
from thrust increase, is slow and does not enable to reduce the AOA instantaneously.
Furthermore, for under wing mounted engines, the thrust increase
generates a pitch up that may prevent the required reduction of AOA.
When stall indications have stopped, and when the aircraft has recovered sufficient energy,
the flight crew can smoothly recover the initial flight path.
STALL WARNING AT LIFT-OFF
If the aural stall warning sounds at liftoff, the flight crew must fly the
appropriate thrust and pitch for takeoff in order to attempt to stop the
aural stall warning and ensure a safe flight path.
The flight crew applies TOGA thrust in order to get the maximum available thrust.
Simultaneously, the pilot flying must target a pitch angle of 15 ° and keep
the wings level in order to ensure safe climb.
Then, when a safe flight path and speed are achieved, if the aural stall
warning is still activated the flight crew must consider that it is a spurious warning.
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mm43
I have noted before the "zipper" (railroad tracks) artifact on the traces.
First I saw it in THS position, then I noticed it appearing on other telltales.
I first thought it pointed to THS vibration. When I noticed it elsewhere, I changed my mind. I also considered it may be simply a poor representation of the data, and that in poor resolution.
Could it, since it represents to me a vibration, be a representation of a graphical evidence of BUFFET? I respect always your patience and objectivity. I also do not mind criticism, as you may know.
It is honest and has no agenda behind it.
edit: The Rudder deflection mates well with the ROLL, indicating "Co-ordinated" controls?
I have noted before the "zipper" (railroad tracks) artifact on the traces.
First I saw it in THS position, then I noticed it appearing on other telltales.
I first thought it pointed to THS vibration. When I noticed it elsewhere, I changed my mind. I also considered it may be simply a poor representation of the data, and that in poor resolution.
Could it, since it represents to me a vibration, be a representation of a graphical evidence of BUFFET? I respect always your patience and objectivity. I also do not mind criticism, as you may know.
It is honest and has no agenda behind it.
edit: The Rudder deflection mates well with the ROLL, indicating "Co-ordinated" controls?
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bearfoil:
If you are talking about the THS jamming or breaking in the nose-up lock position, think carefully before going round the houses again - look at this (again please excuse the low resolution, I only have the PDF to work with):
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.
If you are talking about the THS jamming or breaking in the nose-up lock position, think carefully before going round the houses again - look at this (again please excuse the low resolution, I only have the PDF to work with):
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.
Dozy:
At all, or by this particular crew? I find your confidence in your conclusion misplaced.
At about 10,000 fps, you'd have them at about 25,000 feet after 57 seconds from apogee. That's between two and two and a half minutes to get unstalled, get flying speed, and pull up at something less than 2.5 G.
(BOAC's point on "who would drop the nose 30 degrees" is a good one).
It is recoverable, but maybe not a lead pipe cinch, and it takes deciding that "we are stalled, let's unstall!" as the mind set. That seemed particularly absent in this crew if their verbal cues tell us the story.
Your personal conclusion is not supported by how aircraft work.
What is tragic, in this case, is that the crew remained "behind" the aircraft, and thus it crashed. (Whether or not the stall warning is why, or other reasons are why, or more in combination, is an unknown).
I am grateful for mm43 puttin his finger on something that has been bugging me for a while, in terms of "what would the recovery look like if a healthy nose down input was made?" There was some angular momentum to the right as it descended, that would sustain until corrected, which brings us to his point:
If the aircraft hadn't become relatively stabilized in the 15° NU attitude with the THS and the elevator positioned as we know, the chances of entering a spiral dive would have been high.
Particularly given the trouble the PF had flying wings level.
Old Carthusian:
From one pilot to another, referring to the bit I Italicized-- they are inter-related. As variables, they act upon one another. (Won't wander off into how dynamic feedback loops reinforce one another, that analogy is perhaps too far afield).
As noted before, we are in agreement on most of the human factors, specifically in re training.
As to necessary and sufficient issues:
If no pitot icing, no wreck. That should not be glossed over.
If stall warning doesn't cut out or clip at 60 knots (sensed) would that be a critical difference?
Maybe and maybe not.
The apparent non-recognition of stalled condition is a serious issue, which takes us back to training and recency of experience, and even possible mis diagnosis of their situation.
From what we know about the verbal interchanges (we can't see what anyone nodded at or pointed to with those artful Gallic hands
) there is some reason to believe that due to UAS influencing, hence lost confidence in air mass gauges, and something else (task saturation from trying to simply maintain straight and level?), the audio alerts, be they bogus or valid, became background noise within at least two brain housing groups ... and perhaps the Captain's as well. There's where we seem to agree on the psychology and task threshold piece.
The stall warning sounded continuously from the apogee of the climb (at which point the aircraft approached and entered stall) for 57 seconds, after which point the aircraft was already unrecoverable.
At about 10,000 fps, you'd have them at about 25,000 feet after 57 seconds from apogee. That's between two and two and a half minutes to get unstalled, get flying speed, and pull up at something less than 2.5 G.
(BOAC's point on "who would drop the nose 30 degrees" is a good one).
It is recoverable, but maybe not a lead pipe cinch, and it takes deciding that "we are stalled, let's unstall!" as the mind set. That seemed particularly absent in this crew if their verbal cues tell us the story.
It's a personal conclusion, but I think it's logical.
What is tragic, in this case, is that the crew remained "behind" the aircraft, and thus it crashed. (Whether or not the stall warning is why, or other reasons are why, or more in combination, is an unknown).
I am grateful for mm43 puttin his finger on something that has been bugging me for a while, in terms of "what would the recovery look like if a healthy nose down input was made?" There was some angular momentum to the right as it descended, that would sustain until corrected, which brings us to his point:
If the aircraft hadn't become relatively stabilized in the 15° NU attitude with the THS and the elevator positioned as we know, the chances of entering a spiral dive would have been high.
Particularly given the trouble the PF had flying wings level.
Old Carthusian:
This accident is more of a training and culture issue. It is also a psychological issue (I have some thoughts on this but am not going to speculate until I see the final report. I simply do not have the information to back up my suspicions). I will say this - the answer lies in how people react to situations not in how the aircraft is designed or how the man/machine interface operates.
As noted before, we are in agreement on most of the human factors, specifically in re training.
As to necessary and sufficient issues:
If no pitot icing, no wreck. That should not be glossed over.
If stall warning doesn't cut out or clip at 60 knots (sensed) would that be a critical difference?
Maybe and maybe not.
The apparent non-recognition of stalled condition is a serious issue, which takes us back to training and recency of experience, and even possible mis diagnosis of their situation.
From what we know about the verbal interchanges (we can't see what anyone nodded at or pointed to with those artful Gallic hands
) there is some reason to believe that due to UAS influencing, hence lost confidence in air mass gauges, and something else (task saturation from trying to simply maintain straight and level?), the audio alerts, be they bogus or valid, became background noise within at least two brain housing groups ... and perhaps the Captain's as well. There's where we seem to agree on the psychology and task threshold piece.
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Dozy
Many thanks, I am well past 'broken'. Thank you for not making a big deal. I say what I think, and since I have no conclusions, I am quickly able to change course, this is after all, a "knife-fight"!
Please notice on your depiction that the THS trace has 'serrata', to me indicating a command, but one insufficient to cause actual deflection.
They exhibit a consistent rate and amplitude, thus probably just an electronic telltale. Notice also the appearance of these saw tooths on either "side" of the normed line. This would say to me the "direction" of the command signal?
Lonewolf. "The problem PF had with ROLL". I know what you mean, but it carries an inference that he was not up to it. Can we agree that the ROLL, like the Pitch, was difficult for other than possible Pilot issues with aviating?
Can they have been convinced (for the most part) throughout the Descent, that they were wicked oversped, and not STALLED?
I think it is clear that is the case. "He's pulling UP". "I hope so, we're at 4000 feet!"
Many thanks, I am well past 'broken'. Thank you for not making a big deal. I say what I think, and since I have no conclusions, I am quickly able to change course, this is after all, a "knife-fight"!
Please notice on your depiction that the THS trace has 'serrata', to me indicating a command, but one insufficient to cause actual deflection.
They exhibit a consistent rate and amplitude, thus probably just an electronic telltale. Notice also the appearance of these saw tooths on either "side" of the normed line. This would say to me the "direction" of the command signal?
Lonewolf. "The problem PF had with ROLL". I know what you mean, but it carries an inference that he was not up to it. Can we agree that the ROLL, like the Pitch, was difficult for other than possible Pilot issues with aviating?
Can they have been convinced (for the most part) throughout the Descent, that they were wicked oversped, and not STALLED?
I think it is clear that is the case. "He's pulling UP". "I hope so, we're at 4000 feet!"
Last edited by bearfoil; 3rd Aug 2011 at 14:53.
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In this I agree with both BOAC and yourself - that had the situation been correctly recognised then recovery would be technically possible, but it would have required the training that it appears the pilots at the controls did not possess, or a *eureka* moment followed by instinctive flying.
Old Carthusian:
From one pilot to another, referring to the bit I Italicized-- they are inter-related. As variables, they act upon one another. (Won't wander off into how dynamic feedback loops reinforce one another, that analogy is perhaps too far afield).
As noted before, we are in agreement on most of the human factors, specifically in re training.
As to necessary and sufficient issues:
If no pitot icing, no wreck. That should not be glossed over.
If stall warning doesn't cut out or clip at 60 knots (sensed) would that be a critical difference?
Maybe and maybe not.
The apparent non-recognition of stalled condition is a serious issue, which takes us back to training and recency of experience, and even possible mis diagnosis of their situation.
From one pilot to another, referring to the bit I Italicized-- they are inter-related. As variables, they act upon one another. (Won't wander off into how dynamic feedback loops reinforce one another, that analogy is perhaps too far afield).
As noted before, we are in agreement on most of the human factors, specifically in re training.
As to necessary and sufficient issues:
If no pitot icing, no wreck. That should not be glossed over.
If stall warning doesn't cut out or clip at 60 knots (sensed) would that be a critical difference?
Maybe and maybe not.
The apparent non-recognition of stalled condition is a serious issue, which takes us back to training and recency of experience, and even possible mis diagnosis of their situation.
the audio alerts, be they bogus or valid, became background noise within at least two brain housing groups ... and perhaps the Captain's as well. There's where we seem to agree on the psychology and task threshold piece.
If this was the case, then similar things have happened in the past (e.g Kegworth, where the Captain's attempt to revisit the engine indications was interrupted by the radio - and the Mont St. Odile A320 accident, where the PF began to realise something was up with the altitude and vertical speed, but was interrupted by the PNF pointing out that they were off course laterally). Ultimately this comes down to CRM, and using it effectively.
@bear - The "serrata" you describe happen at the start of every THS movement on the graph, even when a large input is made and a smooth progression follows. The THS is behaving as it should, following the long-term trends of the elevator inputs. The reason you're seeing the "serrata" under AP control is because of the constant elevator and THS corrections that occur under autoflight. I'd be prepared to wager that close in, those traces don't look anything like as regular as they appear, and their apparent regularity is due to the limitations of the resolution and rounding maths in the rendering engine of the software used to draw the charts (which looks a lot like Microsoft Excel).
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If it follows their standard nomenclature, it will appear at:
http://www.bea.aero/docspa/2009/f-cp...90601e3.en.pdf
It is not there yet.
http://www.bea.aero/docspa/2009/f-cp...90601e3.en.pdf
It is not there yet.
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No English translation yet but there is a press release commenting on the report of the removal of the recommendation about the stall warning.
It is in the usual place on BEA site and says that this issue will be adressed by the specialist team(s) set up to look at human factors and man machine interface. They also point out that the warning was continuous for 54 seconds and they will investigate why no appropriate actions seem to have been taken in that time.
No surprises there.
It is in the usual place on BEA site and says that this issue will be adressed by the specialist team(s) set up to look at human factors and man machine interface. They also point out that the warning was continuous for 54 seconds and they will investigate why no appropriate actions seem to have been taken in that time.
No surprises there.
Last edited by badgerh; 3rd Aug 2011 at 17:04. Reason: Gramm-err
Attitude + Power = Performance Not Valid for Stall Recovery
AF447 has contributed substantial hindsight on this situation.
Three pilots over three minutes could not identify the stall problem; they thought they had another problem, likely overspeed, and were trying to solve that one.
It seems the VSI indication was dismissed.
But they did identify decreasing altitude at 9000 and 8000 and became rightly concerned. At that time the fifth digit had dropped from view. Perhaps that got their attention.
How is it that the altimeter display did not get their attention earlier?
As has been mentioned, on a round altimeter the winding hands would be quite obvious.
But an abnormal descent rate on a flat panel display does not grab the pilots' attention as well as a round altimeter.
Should we be coloring the altitude display red or orange for abnormal descent rates?
Three pilots over three minutes could not identify the stall problem; they thought they had another problem, likely overspeed, and were trying to solve that one.
It seems the VSI indication was dismissed.
But they did identify decreasing altitude at 9000 and 8000 and became rightly concerned. At that time the fifth digit had dropped from view. Perhaps that got their attention.
How is it that the altimeter display did not get their attention earlier?
As has been mentioned, on a round altimeter the winding hands would be quite obvious.
But an abnormal descent rate on a flat panel display does not grab the pilots' attention as well as a round altimeter.
Should we be coloring the altitude display red or orange for abnormal descent rates?
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BEA
For those people who want to know if the BEA has published the English version of the report, you can check the same way as I do. Access the Bureau d'Enquêtes et d'Analyses website, select News or Ongoing Investigations for Rio - Paris 2009, and all will be revealed. Even a caveman can do it.
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It seems the VSI indication was dismissed.
Even a caveman can do it
RBF:
Given that other gauges use the green amber red, why not?
Another way to think through this is to use three different colors, so that those three are not cognatively mixed with the colors on the speed display ...
But of all the suggestions I've seen in this discussion, this one leaps out to me as "Why Didn't I Think of That?" in spades. *tips cap*
Should we be coloring the altitude display red or orange for abnormal descent rates?
Another way to think through this is to use three different colors, so that those three are not cognatively mixed with the colors on the speed display ...
But of all the suggestions I've seen in this discussion, this one leaps out to me as "Why Didn't I Think of That?" in spades. *tips cap*
I wonder actually if the VS was 'high' enough to be either off scale or 'lurking' at the bottom and so not 'seen', since it is 'never there'?
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English Version
When the English Version is available, it will be announced and linked here:
BEA: Ongoing Investigations: Flight AF 447 on 1st June 2009
BEA: Ongoing Investigations: Flight AF 447 on 1st June 2009
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RBF
Are we absolutely certain they did not see it? If pre-occupied with an 'overspeed', they would be cognizant of VSI, but, like Altitude, they didn't remark on it till it went "critical"? Overspeed recovery involves an "abrupt" mitigation of descent, unlike any STALL recovery? Also, the VSI was fluctuating, so why trust it implicitly? I think they were flying in a 'blend' of IMC and "seat of pants". Unfortunately, they were relying perhaps a little on the way they "Felt"? So, again, OS wants instant 'g', to the "limit" (and it is available, with protections?). No pressure to endure a ND of 30+ degrees and taptoes to wait for wings 'reload'?
Are we absolutely certain they did not see it? If pre-occupied with an 'overspeed', they would be cognizant of VSI, but, like Altitude, they didn't remark on it till it went "critical"? Overspeed recovery involves an "abrupt" mitigation of descent, unlike any STALL recovery? Also, the VSI was fluctuating, so why trust it implicitly? I think they were flying in a 'blend' of IMC and "seat of pants". Unfortunately, they were relying perhaps a little on the way they "Felt"? So, again, OS wants instant 'g', to the "limit" (and it is available, with protections?). No pressure to endure a ND of 30+ degrees and taptoes to wait for wings 'reload'?
Last edited by bearfoil; 3rd Aug 2011 at 18:22.