AF 447 Thread No. 12
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Although you are right for this case in following PJ2' s early recomendation to do nothing, the conclusion that training in high altitude manual handling and stall avoidance or recovery training for such events is not necessary is premature.
AF 447 could have dropped into direct law as any aircraft in the future could do as well where control in all three axis has to be applied immidiately. Another day, another situation, anouher fault and we go again.
A pilot has to be trained to be able to grab the stick and maintain the necessary attitude througout the complete flight envelope and be able to recover from situations, when this flightenvelope is exceeded by whatever cause it may be.
In the video Confiture posted just some posts before, watch the loadfactor. It is below the normal 1g for 25 sec prior the stall entry and it is nearly consecutive 60 sec below 1 g after the stall enty. Even when pulling the loadfactor was below 1 g. The human body is unfamiliar and very succeptable to reduced g loading, and it is not known to be accompanied by stall. Without physical training expierience of such a situation, with unreliable airspeed, no AOA and no loadfactor indication, how should they have been fully aware of their situation? We are talking in hindsight here, we have analysed and studied all available material, have looked at the FDR second by second, studied books and all available sources and have now a totally different knowledge base then they had during that night.
We know that they did not react to the stall like they should have, but besides the possibility that they were not able to identify in being in a stall they may have reacted on their knowledge base, but didn't know how much nose down stick input was required, how long it was required and how 0 g really feel. "I have no control......" were Bonins words.
AF 447 could have dropped into direct law as any aircraft in the future could do as well where control in all three axis has to be applied immidiately. Another day, another situation, anouher fault and we go again.
A pilot has to be trained to be able to grab the stick and maintain the necessary attitude througout the complete flight envelope and be able to recover from situations, when this flightenvelope is exceeded by whatever cause it may be.
In the video Confiture posted just some posts before, watch the loadfactor. It is below the normal 1g for 25 sec prior the stall entry and it is nearly consecutive 60 sec below 1 g after the stall enty. Even when pulling the loadfactor was below 1 g. The human body is unfamiliar and very succeptable to reduced g loading, and it is not known to be accompanied by stall. Without physical training expierience of such a situation, with unreliable airspeed, no AOA and no loadfactor indication, how should they have been fully aware of their situation? We are talking in hindsight here, we have analysed and studied all available material, have looked at the FDR second by second, studied books and all available sources and have now a totally different knowledge base then they had during that night.
We know that they did not react to the stall like they should have, but besides the possibility that they were not able to identify in being in a stall they may have reacted on their knowledge base, but didn't know how much nose down stick input was required, how long it was required and how 0 g really feel. "I have no control......" were Bonins words.
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vilas,
I agree. But how do you detect it early if you don't have active side stick controls fitted? See Page 4.
http://icatee.org/wp-content/uploads...zu110722en.pdf
"At 1 h 00 min 27 (point n°2), the PNF manually disengaged the AP by pressing the takeover pushbutton on the side-stick. A pitch-up input on the PNF’s side-stick going as far as 3⁄4 to stop was recorded for 6 seconds. This input was accompanied by an input to bank to the right then left. The PNF stated that he did not remember these inputs."
This knee jerk reaction initiated and sustained till it didn't matter anymore caused the problem. It was one off irrational act for want of procedural knowledge. You cannot keep trying it out to perfection. Just don't do it is enough.
http://icatee.org/wp-content/uploads...zu110722en.pdf
"At 1 h 00 min 27 (point n°2), the PNF manually disengaged the AP by pressing the takeover pushbutton on the side-stick. A pitch-up input on the PNF’s side-stick going as far as 3⁄4 to stop was recorded for 6 seconds. This input was accompanied by an input to bank to the right then left. The PNF stated that he did not remember these inputs."
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Goldenrivett
I am not against active side stick. I remember having read 7 or eight years back airbus gave very serious consideration to this but never implemented it. But the side stick is on one side so unless you kept your hand there you may still miss it. In AF447 they were flying without looking at PFD for most part and that I find very strange. It was a clear case of mental confusion may be caused by fear because they knew something was terribly wrong and were unable to figure it out. As you know average inputs into side stick are very small and a startled response in pitch has the possibility of causing excessive destabilisation. Nothing happens if you don't do anything for a few seconds to investigate.
I am not against active side stick. I remember having read 7 or eight years back airbus gave very serious consideration to this but never implemented it. But the side stick is on one side so unless you kept your hand there you may still miss it. In AF447 they were flying without looking at PFD for most part and that I find very strange. It was a clear case of mental confusion may be caused by fear because they knew something was terribly wrong and were unable to figure it out. As you know average inputs into side stick are very small and a startled response in pitch has the possibility of causing excessive destabilisation. Nothing happens if you don't do anything for a few seconds to investigate.
It's very old ground now, but to re-introduce the counterpoint, there is no evidence whatsoever that interconnected CCs are more likely to aid stall recovery and independent SSs.
In fact there are more fatal stall accidents in aircraft with CCs than with SSs.
A CC that is full-back-in-the-PM's-stomach is not a factor in recovery. I can't think of any such accidents where one crew member took action and pushed the stick away from his/her stomach and fully-forward to get the nose down in order to unload then unstall the wing.
In the few accidents I am aware of, the CC remained near/at full aft position until impact.
The problem is not "CC vs. SS" and therefore the solution is not the interconnection of the latter. The data just isn't there, whereas both a working stall warning throughout the entire flight regime and a THS that stops moving with the first stall warning do have data and therefore cause for further examination as does the installation of an AoA indicator.
In fact there are more fatal stall accidents in aircraft with CCs than with SSs.
A CC that is full-back-in-the-PM's-stomach is not a factor in recovery. I can't think of any such accidents where one crew member took action and pushed the stick away from his/her stomach and fully-forward to get the nose down in order to unload then unstall the wing.
In the few accidents I am aware of, the CC remained near/at full aft position until impact.
The problem is not "CC vs. SS" and therefore the solution is not the interconnection of the latter. The data just isn't there, whereas both a working stall warning throughout the entire flight regime and a THS that stops moving with the first stall warning do have data and therefore cause for further examination as does the installation of an AoA indicator.
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It's a moot point anyway, stall warning and buffeting were very well present.
It's self explanatory for anyone who has a slightest clue about flying but I guess I have to bring it down to level understandable to average PPRuNer: if one is below desired altitude, one has to climb to it. If one is above desired altitude, one has to descend to it.
Originally Posted by alf5071h
It is impossible to gain a full understanding of what the aircraft is doing from a small set of two or three lights.
Originally Posted by vilas
Below is the link to SAFO on stall recovery. Actual accidents you will have to google.
Issue with approach to stall recovery that emphasizes minimum altitude loss is not that it's wrong (it isn't) but that it is too narrow in scope. It does not prepare one for high altitude event, full stall, or low altitude event with mistrimmed stabilizer. So my type now has universal procedure that lays burden on the pilot; thrust - as required, trim - as required. Better be sure you make it right first time.
Originally Posted by seagull967
This crew never knew they stalled.
Originally Posted by seagull967
I somewhat agree with you, but I think that if you saw an AoA guage with a CLEARLY defined "red zone" and you are in it, with proper training, a pilot might just do the right thing.
Originally Posted by vilas
AF447 pilots at that point of time did not have the training and technique to deal with the situation.
Originally Posted by vilas
They put the aircraft beyond extremes of flight envelope. You cannot have training solutions to recover from that.
Originally Posted by vilas
The main point of training must be that in Airbus alternate law never grab the stick and apply pitch inputs.
Originally Posted by Retired F4
It is below the normal 1g for 25 sec prior the stall entry and it is nearly consecutive 60 sec below 1 g after the stall enty. Even when pulling the loadfactor was below 1 g. The human body is unfamiliar and very succeptable to reduced g loading, and it is not known to be accompanied by stall. Without physical training expierience of such a situation, with unreliable airspeed, no AOA and no loadfactor indication, how should they have been fully aware of their situation?
Originally Posted by Goldenrivett
I agree. But how do you detect it early if you don't have active side stick controls fitted?
Lufthansa A320 incident at Frankfurt.
Questions?
Originally Posted by vilas
In AF447 they were flying without looking at PFD for most part and that I find very strange.
On salience of position...
The Airbus SS movement is measured in cm's so visual displacement cannot be accurately judged. In terms of tactile sense, if an SS is interconnected, one cannot know by feel or sight where the "null" point is. Small SS movements can result in significant changes in flight path. The initial SS displacements which occurred in AF447 to pitch the aircraft up eventually to 15deg would have been momentary, (meaning 'not steadily applied' but varying), and perhaps 2 cm's, 4 at the most. CC movement for the same result is as you say, small...may be the same numbers but in inches. Approximately...
It is only during the stalled-descent that one sees full-aft CC displacement in the accidents I was thinking of and by then if full-forward CC or SS isn't held in until the wing begins flying again, the airplane does not recover. Some call that a deep stall, but I'm old-fashioned because these stalls are recoverable whereas a deep stall is not; AF447 was recoverable; some say (and have calculated) down to FL100.
The Airbus SS movement is measured in cm's so visual displacement cannot be accurately judged. In terms of tactile sense, if an SS is interconnected, one cannot know by feel or sight where the "null" point is. Small SS movements can result in significant changes in flight path. The initial SS displacements which occurred in AF447 to pitch the aircraft up eventually to 15deg would have been momentary, (meaning 'not steadily applied' but varying), and perhaps 2 cm's, 4 at the most. CC movement for the same result is as you say, small...may be the same numbers but in inches. Approximately...
It is only during the stalled-descent that one sees full-aft CC displacement in the accidents I was thinking of and by then if full-forward CC or SS isn't held in until the wing begins flying again, the airplane does not recover. Some call that a deep stall, but I'm old-fashioned because these stalls are recoverable whereas a deep stall is not; AF447 was recoverable; some say (and have calculated) down to FL100.
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Originally Posted by PJ2
The Airbus SS movement is measured in cm's so visual displacement cannot be accurately judged. In terms of tactile sense, if an SS is interconnected, one cannot know by feel or sight where the "null" point is.
It's very old ground now, but to re-introduce the counterpoint, there is no evidence whatsoever that interconnected CCs are more likely to aid stall recovery and independent SSs.
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Clandestino
Pilot pulls back on side stick and instead of seeing the result on attitude only monitors bank. Isn't that strange instrument flying? Sure in alternate law he had to do only that provided he had not given any pitch input. The actions were not logical but panic stricken, perhaps not coming from rational part of the brain but primal.
Pilot pulls back on side stick and instead of seeing the result on attitude only monitors bank. Isn't that strange instrument flying? Sure in alternate law he had to do only that provided he had not given any pitch input. The actions were not logical but panic stricken, perhaps not coming from rational part of the brain but primal.
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Ah, so easy to sit in your chair in front of your computer and think "that would not have happened to me..." Maybe you're right. Maybe. I know for a fact I could get a very high percentage to do the same thing this crew did with the right set up. Nothing like the wisdom of hindsight bias to make it all seem so obvious.
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Pilot pulls back on side stick and instead of seeing the result on attitude only monitors bank. Isn't that strange instrument flying? Sure in alternate law he had to do only that provided he had not given any pitch input. The actions were not logical but panic stricken, perhaps not coming from rational part of the brain but primal.
All circumstantial except for one thing. Just why was AF447 oscillating in roll during those first 30 seconds?

Who here has had experience with any form of PIO?
Virtually no one
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Clandestino
For Finnegan's sake, it reaches 1.5 g in initial pullup, gets to +0.6 G minimum and then mushes between +0.75 and + 1.25 G for the rest of the flight. It's nothing unusual even for airliner!
For Finnegan's sake, it reaches 1.5 g in initial pullup, gets to +0.6 G minimum and then mushes between +0.75 and + 1.25 G for the rest of the flight. It's nothing unusual even for airliner!
Expieriencing continuous below one g for first consecutive 25 seconds and later for uninterrupted 60 seconds is unusual, whatever you say otherwise. And for this crew it might have been more unusual to decrease the g to 0g as needed for recovery for even longer time, as they never had been exposed to such a situation.
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Machinbird
PIO as the word suggests doesn't happen. It is made to happen. Again we come back to the same point. First you make irrational pitch input then create PIO in roll and forget about the pitch totally and a training programme that caters for all this, You may have to select commercial pilots from aerobatic teams.
PIO as the word suggests doesn't happen. It is made to happen. Again we come back to the same point. First you make irrational pitch input then create PIO in roll and forget about the pitch totally and a training programme that caters for all this, You may have to select commercial pilots from aerobatic teams.
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If I understand your brief explanation correctly then you are suggesting that PF keeps the PM informed of his SS movements verbally, in order to enhance their mutual SA of the control input?
If they had active SS fitted, then the cross wired controller's input would have been cancelled out by the other side's controller and the problem recognised during taxi checks with Zero roll commands. (More easily recognised than Left / Right confusion).
http://aviationweek.com/technology/a...mmercial-debut
But you're right, why should we discuss ideas about how to improve such a perfect system.
Last edited by Goldenrivett; 16th Feb 2015 at 14:19. Reason: extra link
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Machinbird
PIO as the word suggests doesn't happen. It is made to happen. Again we come back to the same point. First you make irrational pitch input then create PIO in roll and forget about the pitch totally and a training programme that caters for all this, You may have to select commercial pilots from aerobatic teams.
PIO as the word suggests doesn't happen. It is made to happen. Again we come back to the same point. First you make irrational pitch input then create PIO in roll and forget about the pitch totally and a training programme that caters for all this, You may have to select commercial pilots from aerobatic teams.
BTW, I think your statement about the irrational pitch input is backwards with the creation of roll PIO. In AF447, The roll PIO started immediately. The pitch excursion followed in the next few seconds.
There have been videos of other Airbus pilots who have a large amplitude (High Gain) control technique that may well be a hazard when suddenly confronted with an unexpected drop to a roll direct condition-particularly if it happens in cruise. I do not know for a fact that this is an actual problem, but logic tells me that it should cause those people problems in that circumstance.
To suggest that a Pilot In the loop Oscillation (PIO) is made to happen is deceptive. Yes the pilot is driving the oscillation due to his control inputs.
No he is not doing it deliberately. He is merely using the controls in the manner that he has been accustomed to and is getting an unexpected and undesired result. The unusual behavior grabs your full attention. This attention grab pulls the pilot out of his trained response pattern. It is as if a poisonous snake has suddenly been dropped onto your flight deck-it demands your full attention.
If you have never experienced a PIO, count yourself fortunate. They are rare but dramatic. The A320 has experienced roll PIO resulting in a missed approach on several occasions. I would not be surprised if the FCS has subsequently had its software modified in subtle ways to reduce the likelihood of future occurences.
Stopping a PIO is usually easy-just get out of the loop-let go of the controls. Then when the aircraft stabilizes, gently apply only the minimum control input necessary to achieve your objective. Has anyone reading this actually received training in this subject?
From what I am able to observe. the subject of PIO/APC is an aviation myth to most pilots. Something they will never confront and do not need to know about. Trying to explain PIO to professional aviators who have never seen it is like talking in a vacuum.

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Originally Posted by Goldenrivett
But you're right, why should we discuss ideas about how to improve such a perfect system.
What is the point of the discussion? If those who are making bold statements about it have no idea about: aerodynamics, aeroplane systems, aeroplane performance, instrument flying, multi-crew operations, state of the pilot training today, that moderate turbulence starts at 0.5G so 0.25 is light or that ten degree roll is really insignificant even in transport aeroplane terms, then it really says a lot about the participants in the discussion but not much about the subject matter.
Originally Posted by Goldenrivett
If I understand your brief explanation correctly then you are suggesting that PF keeps the PM informed of his SS movements verbally, in order to enhance their mutual SA of the control input?
Originally Posted by Wing Commander Spry
Communication, an utterly vital element to Crew Resource Management regardless of aircraft type. Whenever we find ourselves in a situation of ‘unease’ we need to be vocal about what we are thinking but also what we are doing. Once others are aware of your concerns they can be addressed.
Originally Posted by Vilas
You may have to select commercial pilots from aerobatic teams.
Originally Posted by vilas
Pilot pulls back on side stick and instead of seeing the result on attitude only monitors bank. Isn't that strange instrument flying?
Originally Posted by vilas
The actions were not logical but panic stricken, perhaps not coming from rational part of the brain but primal.
Originally Posted by Seagull967
Ah, so easy to sit in your chair in front of your computer and think "that would not have happened to me..."
RHS: 6900 hrs, 6064 on type
LHS: 14 268 hrs, 6161 as captain on type, type rating examiner.
What little we know so far is that it can happen to anyone.
Who here has had experience with any form of PIO?
Virtually no one
Virtually no one

Not sure if that's going to further the debate or not......

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Machine,
RE APC, well put. It has even caught low gain pilots off guard, particularly when coupled with a startle situation or a sudden ramp up in a tight tracking task. Flight test pilots have seen it, and the NRC even stated that there has not been one FBW or augmented hq aircraft that has not had at least one APC event during either flight test or in operation.
RE APC, well put. It has even caught low gain pilots off guard, particularly when coupled with a startle situation or a sudden ramp up in a tight tracking task. Flight test pilots have seen it, and the NRC even stated that there has not been one FBW or augmented hq aircraft that has not had at least one APC event during either flight test or in operation.
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Originally Posted by Clandestino,
Another point that in modern MRJT or LRJT, what your significant cockpit other as PF, AFCS or even you yourself are doing with controls is of no interest to you as long as the aeroplane follows the desired flight path. Whether control input is appropriate is checked on PFD, not by looking at or touching the yoke.
Another point that in modern MRJT or LRJT, what your significant cockpit other as PF, AFCS or even you yourself are doing with controls is of no interest to you as long as the aeroplane follows the desired flight path. Whether control input is appropriate is checked on PFD, not by looking at or touching the yoke.
"The biggest drawback of the “passive” sidesticks now used in civil aircraft is the lack of control feedback from the aircraft or the other pilot."
"This ensures both sidesticks move together in response to both pilot and autopilot commands, providing crew situational awareness equivalent to conventional pilot controls, says BAE."
"But the biggest advantage claimed for active over passive sidesticks is that both pilot and copilot controls track each other at all times. “This provides good situational awareness between the pilots—they can both see and feel their sidesticks moving,” says Taylor."
Active Sidestick Controls Make Commercial Debut | Technology content from Aviation Week
Originally Posted by Clandestino
If those who are making bold statements about it have no idea about: ...... multi-crew operations,
If those who are making bold statements about it have no idea about: ...... multi-crew operations,
Last edited by Goldenrivett; 18th Feb 2015 at 14:45. Reason: extra quotes