AF 447 Thread No. 10
Ahhhhhh..... back to the control law logic and implementation.
From Doze:
I don't think that's entirely accurate.
Best I can tell from the reversion sequence, the "autotrim" for the THS is in effect until in DIRECT law ( or maybe sub-law 2 (c) iv /sarc off). So the system will attempt to achieve 1 gee corrected for pitch attitude. Have I read that wrong? And I also see an implementation that trims the THS in order to reduce the stick inputs required to maintain the gee required to maintain the previously commanded pitch attitude. NOT A PURE ATTITUDE HOLD mode many of us were used to in A/P -assisted modes.
So relaxing stick with a positive pitch attitude would "normally" result in increasing THS until the AoA functions kick in. Their "mode" didn't have the AoA "protections", if I read that law correctly.
I must agree that manually flying a basic jet at high altitude and a mach near 0.85M is not nearly as benign as the same IAS at 15,000 or 20,000 feet. That mach doofer causes some strange things, and your TAS is much higher so you muct be gentle and use measured inputs. So being a low altitude glider pilot may not satisfy the criteria.
Still a sad, sad example of airmanship and systems knowledge and crew coordination.
From Doze:
It won't do anything unless the pilot asks it to though!
Best I can tell from the reversion sequence, the "autotrim" for the THS is in effect until in DIRECT law ( or maybe sub-law 2 (c) iv /sarc off). So the system will attempt to achieve 1 gee corrected for pitch attitude. Have I read that wrong? And I also see an implementation that trims the THS in order to reduce the stick inputs required to maintain the gee required to maintain the previously commanded pitch attitude. NOT A PURE ATTITUDE HOLD mode many of us were used to in A/P -assisted modes.
So relaxing stick with a positive pitch attitude would "normally" result in increasing THS until the AoA functions kick in. Their "mode" didn't have the AoA "protections", if I read that law correctly.
I must agree that manually flying a basic jet at high altitude and a mach near 0.85M is not nearly as benign as the same IAS at 15,000 or 20,000 feet. That mach doofer causes some strange things, and your TAS is much higher so you muct be gentle and use measured inputs. So being a low altitude glider pilot may not satisfy the criteria.
Still a sad, sad example of airmanship and systems knowledge and crew coordination.
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LW
The Three? ASI. This is about velocity, not attitude, or altitude. This would be expected with UAS, speeds being misleading, depending on rate and simultaneity of ICE blockages....
It also clearly tells us that the crew are not cognizant of UAS; if they were, they would not be so alerted to a needed correction......they would mistrust the speeds.... not act on them.
It also sets the tone for the throttle obsession PF demonstrated on the way up...
He is seeking a speed to settle on, not a PITCH. He does not tumble to PITCH until later on....
from gums...
This crew, but especially PF Bonin, was not madly pulling on the stick from the loss of A/P, not at all. PITCH increased incrementally, and PF was not cognizant of its dangerous trend, each time he relaxed, he felt one gee...even when increasing, it was seemingly "benign"....
His "I have no control of the plane..." happened after the THS migrated to essentially full (-)....
That does not explain his lack of concern with the Attitude increase, but he was focused on speed, and Roll....
I will repeat myself for the umpteenth time, this crash started with a vengeance at loss of speeds, not with "Full aft Stick"....
We are not certain at all the crew was aware of UAS until 2:10:22, sixteen seconds after loss of a/p. By that time, and imo, the die was cast. After STALL, it's all jelly beans, and pub blather.
EDIT LONEWOLF
You and I do not know if it was recorded, or not. Only BEA know that, and they are not saying....
PL : Watch your speed Watch your speed
PR: ok ok ok I'm going back down
PL: According to the three you're going up, so you go back down
PL: You're at ... go back down
PR: ok ok ok I'm going back down
PL: According to the three you're going up, so you go back down
PL: You're at ... go back down
It also clearly tells us that the crew are not cognizant of UAS; if they were, they would not be so alerted to a needed correction......they would mistrust the speeds.... not act on them.
It also sets the tone for the throttle obsession PF demonstrated on the way up...
He is seeking a speed to settle on, not a PITCH. He does not tumble to PITCH until later on....
from gums...
So relaxing stick with a positive pitch attitude would "normally" result in increasing THS until the AoA functions kick in. Their "mode" didn't have the AoA "protections", if I read that law correctly.
His "I have no control of the plane..." happened after the THS migrated to essentially full (-)....
That does not explain his lack of concern with the Attitude increase, but he was focused on speed, and Roll....
I will repeat myself for the umpteenth time, this crash started with a vengeance at loss of speeds, not with "Full aft Stick"....
We are not certain at all the crew was aware of UAS until 2:10:22, sixteen seconds after loss of a/p. By that time, and imo, the die was cast. After STALL, it's all jelly beans, and pub blather.
EDIT LONEWOLF
In the next minute, for whatever discussion and control input went on, and as we've discussed numerous times before, a correction to the person at the controls (PR) to do something with pitch is not recorded.
Last edited by Lyman; 4th Mar 2013 at 16:53.
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I guess it depends on how the phrase is interpreted. Commanding a pitch attitude with the stick will cause autotrim to maintain the pitch attitude at the point the stick was released to the best of its ability.
Put more simply, autotrim is active in all laws and sub-laws except Direct (and MAN PITCH TRIM ONLY).
Releasing the stick effectively commands attitude in Normal Law and all modes of Alternate. Releasing at a given pitch attitude will cause the flight control logic to gradually release the elevator demand used to acquire that pitch attitude as the trim takes up the slack.
It's different to other implementations, but in terms of airliner ops it makes sense. The fact that it works cannot be denied.
Best I can tell from the reversion sequence, the "autotrim" for the THS is in effect until in DIRECT law ( or maybe sub-law 2 (c) iv /sarc off).
So relaxing stick with a positive pitch attitude would "normally" result in increasing THS until the AoA functions kick in.
It's different to other implementations, but in terms of airliner ops it makes sense. The fact that it works cannot be denied.
Last edited by DozyWannabe; 4th Mar 2013 at 17:29.
Salute!
TNX, Doze for confirming my understanding of the THS.
However, the big point I have trying to make for 2 years is that the flight control laws for the 'bus use the basic gee command, but corrected for the pitch attitude.
The biggie is "effectively commands attitude". In other words, it will use 0.87 Nz at a pitch attitude of 30 degrees. So without increasing power, the speed/AoA changes and the THS keeps on keeping on to maintain the 30 deg pitch attitude until the jet reaches the AoA protections - HANDS OFF!!. This has an insidious effect, as "normal" jets would require more and more back-stick to maintain the attitude due to increasing AoA as it slows down. Again, I must remind all that our first FBW system was a blend of AoA and Nz. So we noticed that we had full back stick and nothing was happening with the nose once we hit the AoA limit for that gee. At max AoA, we were one Nz gee command.
TNX, Doze for confirming my understanding of the THS.
However, the big point I have trying to make for 2 years is that the flight control laws for the 'bus use the basic gee command, but corrected for the pitch attitude.
Releasing the stick effectively commands attitude in Normal Law and all modes of Alternate. Releasing at a given pitch attitude will cause the flight control logic to gradually release the elevator demand used to acquire that pitch attitude as the trim takes up the slack.
Hi Lyman;
Re your observation in Post #816 that, "AoA can be derived, . . ."
Hm, I don't think so. I'm not an aeronautical engineer but how can AoA be "derived"?
Lonewolf_50;
Re, "How do you train someone (Captain Dubois) when the info to train him with doesn't exist? Further that lack of data points, the flight sims can't be soundly programmed to give "what it does when stalled" training."
It is true that approach-to-stall recovery training isn't the same as training to get a transport aircraft out of a stall. However the guidance in FCTMs is clear, that a high descent rate that cannot be arrested indicates that the aircraft is stalled and the AoA must be reduced.
"This leaves any pilot, not just Captain Dubois, lacking a chance to be in a full stall situation in a training scenario. Granted, stall prevention is the general training focus, for good and valid reasons."
While there is little to no actual flight data on aircraft behaviour in a full stall, that does not mean that the simulator is demonstrating entirely and completely unreliable or incorrect behaviour. The degree to which behaviour is or isn't replicated may be more apparent to engineers than to pilots who must recover the airplane. What I'm saying here is, I think an A330 Level D simulator is useful and not irrelevant. Airbus and the BEA must have thought so because they replicated AF447 and in the Final Report even drew graphs in comparison with AF447's flight data.
What was missing in AF447 was the acceptance that the airplane was stalled, and the knowledge and/or comprehension that the wing must be unloaded, the AoA reduced in order to recover, and that for this to occur the only way is to point the nose down.
Re, (my bolding), "To sum up: I don't think he'd "seen that before" and thus was playing catch up from the moment he entered the cockpit. Had what he saw, as you suggest, been something he recognized as a stalled A330 -- something "he'd seen before" -- my estimate is that he'd have directed Bonin to make stall recovery control inputs rather than the directions he did give him."
Yes, I agree with you on all points. Given a full understanding of the problem (the stall), it's what flight crews would do. The puzzle is in why an altimeter reducing by a thousand feet every 3 seconds while the nose was pointed up, didn't register and that fact is purely for hindsight speculation.
Re, "It is also my estimate that CVR transcripts would have included some rather forceful language, to include such bon mots as "merde, we're stalled, get the &$^# nose down!" or words to that effect."
Yes, I have to agree that's how someone would say it!
Dozy;
It is neither practically nor philosophically merely just an "iterative example of how technology has changed." It is a far more complex human phenomenon that requires the respect of awareness. Technology changes who we are and if we are blind to that, we are blind to its dangers while lauding its benefits.
That said, I should have thought the reason obvious; - because the old-fashioned way worked and saves lives on occasions when technology gives up and hands a mess over to the human pilot who can competently, safely take over and live to enter the snag in the log book.
You already know I have no problem with automation and all technological advances just so long as one knows one's craft and can do the job when the bytes and pixels quit - in other words, one is competent at one's job as a pilot and never lets anyone think that technology should be respected. Understood, yes!, but never respected and that means knowing how to fly and think regardless of technology.
Re your observation in Post #816 that, "AoA can be derived, . . ."
Hm, I don't think so. I'm not an aeronautical engineer but how can AoA be "derived"?
Lonewolf_50;
Re, "How do you train someone (Captain Dubois) when the info to train him with doesn't exist? Further that lack of data points, the flight sims can't be soundly programmed to give "what it does when stalled" training."
It is true that approach-to-stall recovery training isn't the same as training to get a transport aircraft out of a stall. However the guidance in FCTMs is clear, that a high descent rate that cannot be arrested indicates that the aircraft is stalled and the AoA must be reduced.
"This leaves any pilot, not just Captain Dubois, lacking a chance to be in a full stall situation in a training scenario. Granted, stall prevention is the general training focus, for good and valid reasons."
While there is little to no actual flight data on aircraft behaviour in a full stall, that does not mean that the simulator is demonstrating entirely and completely unreliable or incorrect behaviour. The degree to which behaviour is or isn't replicated may be more apparent to engineers than to pilots who must recover the airplane. What I'm saying here is, I think an A330 Level D simulator is useful and not irrelevant. Airbus and the BEA must have thought so because they replicated AF447 and in the Final Report even drew graphs in comparison with AF447's flight data.
What was missing in AF447 was the acceptance that the airplane was stalled, and the knowledge and/or comprehension that the wing must be unloaded, the AoA reduced in order to recover, and that for this to occur the only way is to point the nose down.
Re, (my bolding), "To sum up: I don't think he'd "seen that before" and thus was playing catch up from the moment he entered the cockpit. Had what he saw, as you suggest, been something he recognized as a stalled A330 -- something "he'd seen before" -- my estimate is that he'd have directed Bonin to make stall recovery control inputs rather than the directions he did give him."
Yes, I agree with you on all points. Given a full understanding of the problem (the stall), it's what flight crews would do. The puzzle is in why an altimeter reducing by a thousand feet every 3 seconds while the nose was pointed up, didn't register and that fact is purely for hindsight speculation.
Re, "It is also my estimate that CVR transcripts would have included some rather forceful language, to include such bon mots as "merde, we're stalled, get the &$^# nose down!" or words to that effect."
Yes, I have to agree that's how someone would say it!
Dozy;
Quote:
Originally Posted by Machinbird
Generations of pilots learned to fly smoothly by a proper use of the trim controls. The Airbus architecture minimizes the value of this skill...
Originally Posted by Machinbird
Generations of pilots learned to fly smoothly by a proper use of the trim controls. The Airbus architecture minimizes the value of this skill...
Originally Posted by Dozywannabe
"Well yes, but that doesn't make the Airbus FBW system bad, dangerous or worse than anything else - it's just an iterative example of how technology has changed. I don't mean to sound disrespectful, but isn't there a hint of 'why can't they just do it the old-fashioned way' about that point?"
That said, I should have thought the reason obvious; - because the old-fashioned way worked and saves lives on occasions when technology gives up and hands a mess over to the human pilot who can competently, safely take over and live to enter the snag in the log book.
You already know I have no problem with automation and all technological advances just so long as one knows one's craft and can do the job when the bytes and pixels quit - in other words, one is competent at one's job as a pilot and never lets anyone think that technology should be respected. Understood, yes!, but never respected and that means knowing how to fly and think regardless of technology.
Last edited by PJ2; 4th Mar 2013 at 18:26.
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The biggie is "effectively commands attitude". In other words, it will use 0.87 Nz at a pitch attitude of 30 degrees. So without increasing power, the speed/AoA changes and the THS keeps on keeping on to maintain the 30 deg pitch attitude until the jet reaches the AoA protections - HANDS OFF!!.
This has an insidious effect, as "normal" jets would require more and more back-stick to maintain the attitude due to increasing AoA as it slows down.
It's undoubtedly an aspect that's different than what went before, but time has shown that it's simple, reliable and works just fine.
Again, I must remind all that our first FBW system was a blend of AoA and Nz. So we noticed that we had full back stick and nothing was happening with the nose once we hit the AoA limit for that gee. At max AoA, we were one Nz gee command.
Hi PJ2, and regards!
That said, I should have thought the reason obvious; - because the old-fashioned way worked and saves lives on occasions when technology gives up and hands a mess over to the human pilot who can competently, safely take over and live to enter the snag in the log book.
...never lets anyone think that technology should be respected. Understood, yes!, but never respected and that means knowing how to fly and think regardless of technology.
Conversely when an argument is made that technology should not be respected, following that path runs the risk of negating one of the biggest motivators for wanting to understand something, does it not? In my experience, learning and understanding a subject becomes much easier and more rewarding if respect for and interest in that subject already exists.
Last edited by DozyWannabe; 4th Mar 2013 at 19:09.
gums:
I think that the Left Seat Pilot activated that, by calling the Captain. 
Lyman:
Lyman, I am not so sure about that.
PL: According to the three you're going up, so you go back down
I'd say, within the context of that passage, the gent in the left seat was referring to ALTITUDE and CLIMB, since SPEED display systems at this point weren't showing any useful information.
They were in UAS at the time, so there was no good info according to the three ASIs then available to them. Does my reasoning make sense to you?
Three being VSI, altimeter, and something related to the FD. (And I may be utterly wrong.)
PJ2:
The temptation for me to run yet again down that rat hole of "why no AoA gauge in the cockpit?" shall be resisted. 
Roger. Perhaps at the very least this can be grown into at least some procedural training for future crews? We shall see. The original simulators I flew for instrument training some three decades ago were hardly Level D sims, but I sure got graded on my instrument flying in them anyway. Some training was indeed achieved, though I got no style points.
Thanks for the course correction, PJ2. As usual, a pleasure.
... maybe sub-law 2 (c) iv
Lyman:
The Three? ASI. This is about velocity, not attitude, or altitude. This would be expected with UAS, speeds being misleading, depending on rate and simultaneity of ICE blockages.
PL: According to the three you're going up, so you go back down
I'd say, within the context of that passage, the gent in the left seat was referring to ALTITUDE and CLIMB, since SPEED display systems at this point weren't showing any useful information.
They were in UAS at the time, so there was no good info according to the three ASIs then available to them. Does my reasoning make sense to you?
Three being VSI, altimeter, and something related to the FD. (And I may be utterly wrong.)
PJ2:
However the guidance in FCTMs is clear, that a high descent rate that cannot be arrested indicates that the aircraft is stalled and the AoA must be reduced.
What I'm saying here is, I think an A330 Level D simulator is useful and not irrelevant. Airbus and the BEA must have thought so because they replicated AF447 and in the Final Report even drew graphs in comparison with AF447's flight data.
Thanks for the course correction, PJ2. As usual, a pleasure.
Last edited by Lonewolf_50; 4th Mar 2013 at 19:28.
Regards, Dozy;
"The old-fashioned way" then being just a reference to the way trim is handled - okay thanks for your clarification - I hadn't read carefully enough. In other words, use the pickle-switches...manually trim all the time when one is manually flying.
Yes, I'd probably agree with the requirement when manually flying as trimming was one tactical feedback loop that I do recall on the Boeings, Douglases and Lockheeds. At the same time, I don't recall it being a transition or operational problem on the A320.
Now I never went back to manual trim airplanes so can't speak for that direction of a transition.
I wonder if the B787 is full-time auto-trim...can't recall at the moment.
No the system hasn't by itself handed over a mess, that's an autoflight function 
and of course the comment therefore doesn't apply.
Bit OT, but "respect" means trust and belief in reliability and integrity of that which one grants one's respect. That has nothing to do with interest in and / or understanding something although for some it may be a motivator. I do not and never will trust technology per se and do not unconditionally believe in it or its nature but I use it every day and for the most part understand the simpler bits within a consumer's competency.
LW;
LOL...I can assure you that a Level D sim doesn't make it look any more stylish...
Yes, I agree, I think there is a definite training advantage to seeing 15deg ND and a descent rate of 15,000fpm if only to realize that it (in extreme circumstances, much the same as other unusual attitudes), may be necessary and it doesn't break the airplane. If one is in a corner, I think overspeeding the airframe is preferable to stalling it.
There are some thoughts that recovery from this stall was possible even below FL150 had the wing been aggressively unloaded and the AoA reduced. Up higher it took about 40". Down lower I'd hazard a guess that it would take a lot less time and therefore altitude, (thicker air). The elevators were effective in the sim all the way down even against a -13deg THS, and it always wound towards the ND position with steady ND SS. The FPA would have been available at that time on this flight (IIRC) and could have shown them the descent angle. But by that time, the stick and the elevators were almost continuously full-up.
To be certain, I was referring only to the autotrim function on the FBW Airbus system - no other aspect of it.
Yes, I'd probably agree with the requirement when manually flying as trimming was one tactical feedback loop that I do recall on the Boeings, Douglases and Lockheeds. At the same time, I don't recall it being a transition or operational problem on the A320.
Now I never went back to manual trim airplanes so can't speak for that direction of a transition.
I wonder if the B787 is full-time auto-trim...can't recall at the moment.
However to the best of my knowledge the autotrim system in and of itself has never given up and handed a mess to the pilot.
and of course the comment therefore doesn't apply.Bit OT, but "respect" means trust and belief in reliability and integrity of that which one grants one's respect. That has nothing to do with interest in and / or understanding something although for some it may be a motivator. I do not and never will trust technology per se and do not unconditionally believe in it or its nature but I use it every day and for the most part understand the simpler bits within a consumer's competency.
LW;
Perhaps at the very least this can be grown into at least some procedural training for future crews? We shall see. The original simulators I flew for instrument training some three decades ago were hardly Level D sims, but I sure got graded on my instrument flying in them anyway. Some training was indeed achieved, though I got no style points.
Yes, I agree, I think there is a definite training advantage to seeing 15deg ND and a descent rate of 15,000fpm if only to realize that it (in extreme circumstances, much the same as other unusual attitudes), may be necessary and it doesn't break the airplane. If one is in a corner, I think overspeeding the airframe is preferable to stalling it.
There are some thoughts that recovery from this stall was possible even below FL150 had the wing been aggressively unloaded and the AoA reduced. Up higher it took about 40". Down lower I'd hazard a guess that it would take a lot less time and therefore altitude, (thicker air). The elevators were effective in the sim all the way down even against a -13deg THS, and it always wound towards the ND position with steady ND SS. The FPA would have been available at that time on this flight (IIRC) and could have shown them the descent angle. But by that time, the stick and the elevators were almost continuously full-up.
Hail, hail the gangs all here!
DOZE!!! I still don't think you understand my point about the insidious effect of the 'bus autotrim WRT the gee command and pitch attitude.
Gotta tellya, that if the AF447 crew had a gut understanding of the system, we wouldn't all be here talking about it.
I still see 'bus drivers talking about "commanding" a pitch attitude. WRONG! They command a gee and when reaching desired pitch they release the stick and the THS "autotrims" to maintain the gee for that pitch attitude. In the 'bus, these are very small pitch attitude changes and nothing like the ones we commanded in the Viper. I will grant you that. But basic aero and the controls law prevail. I am not all that sure that the basic 'bus driver understands that.
Up to me, I would demo the control laws down at 15,000 feet or so to eliminate mach effects. Pull up to 10 degrees and watch the trim wheel move as you relax the stick to hold that attitude. Hmmmm. Wait until the AoA protection displays and such kick in and let'er rip! Nose goes down and commanded gee changes, etc. etc.
No need to do a no sierra approach to stall, as the AoA protection limits seem very conservative to me when looking at the manuals.
In the Viper, we would demo the autotrim and have Joe Baggodonuts look back and observe our "THS". Pull up and relax the stick. Eventually get to the AoA limit and see the tail moving more and more until it was commanding full nose down. We commanded trim gee that was not corrected for pitch attitude like the 'bus.
@ PJ
In wings level flight, AoA can be derived from the pitch and the inertial velocity vector regardless of the air data probes/cones. The Sluf and Viper HUD had a "zero sight line" cross, and usually the flight path marker ( FPM) was below it ( negative gees was something else, heh heh). That was your AoA in wings level flight.
I'll still maintain that a HUD with the FPM displayed WRT pitch lines would have provided a big clue as to what was happening. The doggone thing shows exactly where the jet is going without regard for airspeed, altitude, attitude, roll angle, gee, AoA, ad nauseum. Also neat for final approach in crappy weather.
With back stick, the pilot would have seen decreasing FPM angle and moved the stick forward well before the AoA alarms went on. In other words, it would have been like looking out the windshield in daytime, CAVU, with nice scenery in front.
I am still disappointed that many think the 'bus stick commands a pitch attitude and not a small delta in the gee command to reach the desired pitch.
DOZE!!! I still don't think you understand my point about the insidious effect of the 'bus autotrim WRT the gee command and pitch attitude.
Well yes, but that's exactly what it's supposed to do, and pilots converting to the FBW Airbus series are trained on that aspect of the behaviour.
I don't know if "insidious" is the right word, as the behaviour is drilled into pilot training from the start. From a piloting perspective it's essentially "point and forget", and it applies whether commanding positive pitch, negative pitch or levelling off.
It's undoubtedly an aspect that's different than what went before, but time has shown that it's simple, reliable and works just fine.
I don't know if "insidious" is the right word, as the behaviour is drilled into pilot training from the start. From a piloting perspective it's essentially "point and forget", and it applies whether commanding positive pitch, negative pitch or levelling off.
It's undoubtedly an aspect that's different than what went before, but time has shown that it's simple, reliable and works just fine.
I still see 'bus drivers talking about "commanding" a pitch attitude. WRONG! They command a gee and when reaching desired pitch they release the stick and the THS "autotrims" to maintain the gee for that pitch attitude. In the 'bus, these are very small pitch attitude changes and nothing like the ones we commanded in the Viper. I will grant you that. But basic aero and the controls law prevail. I am not all that sure that the basic 'bus driver understands that.
Up to me, I would demo the control laws down at 15,000 feet or so to eliminate mach effects. Pull up to 10 degrees and watch the trim wheel move as you relax the stick to hold that attitude. Hmmmm. Wait until the AoA protection displays and such kick in and let'er rip! Nose goes down and commanded gee changes, etc. etc.
No need to do a no sierra approach to stall, as the AoA protection limits seem very conservative to me when looking at the manuals.
In the Viper, we would demo the autotrim and have Joe Baggodonuts look back and observe our "THS". Pull up and relax the stick. Eventually get to the AoA limit and see the tail moving more and more until it was commanding full nose down. We commanded trim gee that was not corrected for pitch attitude like the 'bus.
@ PJ
In wings level flight, AoA can be derived from the pitch and the inertial velocity vector regardless of the air data probes/cones. The Sluf and Viper HUD had a "zero sight line" cross, and usually the flight path marker ( FPM) was below it ( negative gees was something else, heh heh). That was your AoA in wings level flight.
I'll still maintain that a HUD with the FPM displayed WRT pitch lines would have provided a big clue as to what was happening. The doggone thing shows exactly where the jet is going without regard for airspeed, altitude, attitude, roll angle, gee, AoA, ad nauseum. Also neat for final approach in crappy weather.
With back stick, the pilot would have seen decreasing FPM angle and moved the stick forward well before the AoA alarms went on. In other words, it would have been like looking out the windshield in daytime, CAVU, with nice scenery in front.
I am still disappointed that many think the 'bus stick commands a pitch attitude and not a small delta in the gee command to reach the desired pitch.
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Can we not see the copilots pulled up into a 11 degree nose up attitude that obviously would stall the airplane. Then they held back SS to maintain the stall until impact with the ocean. No pilots I know would do this so why did they do it?
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Originally Posted by Dozy
It won't do anything unless the pilot asks it to though!
Will cease at alpha prot in Normal Law but will go all the way In AF447 Law ... Find the logic ?
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I think I know but Airbus training needs to include how degrading automation needs to let people understand the level of automation they are at.
1.. They are told they are in ALT Law,
2.. Know the A/THR has disconnected, and
3.. Pull back on the SS, and with
4.. Stall Warning ring in their ears, they
5.. Do nothing right!
It may well all be put down to lack of appropriate training, but even then, "You can lead a horse to water, ... but?"
Last edited by mm43; 5th Mar 2013 at 17:39. Reason: spelling!
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Just an analogy:
The FCOM says about High Angle of Attack Protection:
When I first read that, I just thought - well, that's logical, and went on reading. Prior to the two incidents, I never realized that, when this happens in cruise and the SS is not pushed forward, the airplane zooms up 3000 ft.
I don't think AF447 will happen again - until everyone has forgotten all about it.
P.S.
Had the pilots of the AF 'level bust' incident been told about the THY incident?
The FCOM says about High Angle of Attack Protection:
Under normal law, when angle of attack becomes greater than alpha-prot, the system switches the elevator control from normal mode to a protection mode in which the angle of attack is proportional to the sidestick deflection. (...) If the pilot releases the sidestick the angle of attack returns to alpha-prot and stays there. (...) To leave the angle of attack protection the sidestick must be pushed (...) forward.
I don't think AF447 will happen again - until everyone has forgotten all about it.
P.S.
Had the pilots of the AF 'level bust' incident been told about the THY incident?
Last edited by HazelNuts39; 5th Mar 2013 at 08:54. Reason: P.S. added
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HazelNuts39
For how long does the AoA "stay there"? (Alpha Protection) what does it take to gain Nose Down?
"Push the stick forward"?
How far forward? Does THS freeze, or ennable the protection?
At the outset, just after loss of auto, Bonin commanded a climb. Two seconds later... "STALLWARN.....cricket, cricket, Master Caution......" and from Robert, "What was THAT?.....". Was he referring to the SW, or to BUFFET? That would qualify an exceedance of Alpha Prot, especially with an assistance from WindShear? (updraft). Is this the reason Pitch remains in gee? ALII (b)?
I think I read here that forward stick must be fully forward, something we do not see from Bonin? Once discouraged from applying forward stick by the recurrence of inappropriate STALL warn, would he desist from further attempts?
How does THY pertain to 447?
(...) If the pilot releases the sidestick the angle of attack returns to alpha-prot and stays there. (...) To leave the angle of attack protection the sidestick must be pushed (...) forward.
"Push the stick forward"?
How far forward? Does THS freeze, or ennable the protection?
At the outset, just after loss of auto, Bonin commanded a climb. Two seconds later... "STALLWARN.....cricket, cricket, Master Caution......" and from Robert, "What was THAT?.....". Was he referring to the SW, or to BUFFET? That would qualify an exceedance of Alpha Prot, especially with an assistance from WindShear? (updraft). Is this the reason Pitch remains in gee? ALII (b)?
I think I read here that forward stick must be fully forward, something we do not see from Bonin? Once discouraged from applying forward stick by the recurrence of inappropriate STALL warn, would he desist from further attempts?
How does THY pertain to 447?
Last edited by Lyman; 5th Mar 2013 at 10:33.
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Howdy...
For purposes of discussion, say A/P had dropped, and the aircraft had remained in NORMAL LAW. Is this same circumstance then also possible? Is this protection available in ALII (b) ? Or, only "g prot" ? The "G" had reached +1.65 in the climb, at (prior to) 7000 FPM .......
Is it possible for this Aircraft AoA to exceed Alpha Prot in Auto?
One last, for now, What is the possibility that PF believed the aircraft had remained in NORMAL LAW until he heard his mate declare at 2:10:22: "Lost speeds, Alternate Law..." ??
Any possibility? If not, what was his alert to LAW change?
For purposes of discussion, say A/P had dropped, and the aircraft had remained in NORMAL LAW. Is this same circumstance then also possible? Is this protection available in ALII (b) ? Or, only "g prot" ? The "G" had reached +1.65 in the climb, at (prior to) 7000 FPM .......
Is it possible for this Aircraft AoA to exceed Alpha Prot in Auto?
One last, for now, What is the possibility that PF believed the aircraft had remained in NORMAL LAW until he heard his mate declare at 2:10:22: "Lost speeds, Alternate Law..." ??
Any possibility? If not, what was his alert to LAW change?
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jc, your opinions aren't helping explain this to a layman.
The dual problems of training and proficiency have been beaten to death. I am trying to make neutral and helpful replies. Where I fail to do so, please help explain to this layman.
Our friend algobotur initiated his inquiry with a seeming belief in AutoPilot as a tool and a fail safe. I have tried to explain to him how that is an invalid approach to take in understanding this tragic accident.
The dual problems of training and proficiency have been beaten to death. I am trying to make neutral and helpful replies. Where I fail to do so, please help explain to this layman.
Our friend algobotur initiated his inquiry with a seeming belief in AutoPilot as a tool and a fail safe. I have tried to explain to him how that is an invalid approach to take in understanding this tragic accident.
... and doing a very fine job at that !
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Lyman,
I'm somewhat reluctant to reply to your questions, because the 'level bust' incidents have been discussed at length in various threads and have no relation to AF 447.
Since the High AoA protection is not available in ALT 2b. it can only occur if the airplane remains in Normal law.
Yes, it is possible for AoA to exceed Alpha Prot in Auto. IIRC that occurred in the Turkish level bust due to turbulence. The AP disconnects when that occurs.
Your last question - if the PF failed to notice the indications on the PFD and ECAM and did not hear the PNF's announcement, it is possible he was not aware of the law change.
I'm somewhat reluctant to reply to your questions, because the 'level bust' incidents have been discussed at length in various threads and have no relation to AF 447.
Since the High AoA protection is not available in ALT 2b. it can only occur if the airplane remains in Normal law.
Yes, it is possible for AoA to exceed Alpha Prot in Auto. IIRC that occurred in the Turkish level bust due to turbulence. The AP disconnects when that occurs.
Your last question - if the PF failed to notice the indications on the PFD and ECAM and did not hear the PNF's announcement, it is possible he was not aware of the law change.
AZR:
merci beaucoup (You are making me blush!
)
Hazelnuts39:
I hate to agree with that, but I must agree based on the last century of manned flight.
merci beaucoup (You are making me blush!
) Hazelnuts39:
I don't think AF447 will happen again - until everyone has forgotten all about it.