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Thread: Air France Off the Hook on AF447

  1. #21
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    Yes, but they were misleading at 2h 10min 05. When the idea to pull up first came to mind.



    Not if you refuse to look carefully at the FDR and see how very far from 'pulling up the whole time' it really was. Then the discussion can't be had.
    Evan, he was pulling up all the time on average, and I am talking about short-term moving average, not just overall...

    Now, ok, in a "traditional" plane (including Boeing FBW), you pull say 1/4 back and the plane quickly stabilizes at the new AoA and eventually it will reach its new speed of equilibrium for that AoA (after the phugoid oscillations if not dampened by the pilot or the FBW).

    Now, in an Airbus in normal or alternate law, pull back 1/4 and it means keeping more than 1G, there is no equilibrium to be reached ever with the control pulled anything back. Even in normal law when the speed goes down it transitions from G-on-stick to pitch-rate-on-stick so in both cases it would keep pitching up indefinitely, if it's not by protections (most of them lost in alternate law) or physical limitations (like stalling).

    Now, the pilot when hand-flying (the same than a driver when driving) is part of a closed-loop control system. You just don't put the elevator at 1/4 back and leave it there. You have a performance goal in mind (remember that conversation???) and compare the actual performance with the desired performance and make the necessary adjustments in the control. That's why you see the pilots moving the yoke or stick almost all the time in an approach to landing. Now, what was the performance goal that this pilot had in mind again???? Because the way that he was beating mayonnaise with the stick has no rational correlation with him trying to achieve any specific performance. The point is not what was the instantaneous position of the stick at each second. The point is that by doing what he did with the stick he actively performed an unsustainable skyrocketing climb (and he might have lost the speeds but the other 8 instruments were consistent with this crazy climb) and, when a warning that is actually an APPROACH to stall warning sounded, he pulled up again sending the pitch up again and the AoA with it and actively stalling the plane, and kept pulling up on average whcih made the AoA increase to 40 degrees, ignoring the fact that the pitch was showing 10 deg up, the vertical speed was 10K fpm down, the altimeters were unwinding like crazy, and did I mention the stall warning that since the first "stall" announcement at the top of the climb was sounding uninterruptedly for 30 seconds?

    Say that you drive the car in a road that is straight but a bit uneven and there are gusting crosswinds. You will need to make permanent adjustments to keep the car on the desired lane, and you will compare the actual track of the car with the desired track (i.e. keep the lane) to make continuous adjustments in the steering wheel. If you start to move the steering wheel all over the place but with a clear average to the left, you will very soon depart the road and then declare "but I was NOT turning left all the time".

    Even the pilot admitted that "I was pulling up all the time". While if you read the fine print that is not exactly what he did at each instant, it is clear that that was his main focus and what he did on average (again, even short-term moving average).

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  2. #22
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    Evan, he was pulling up all the time on average, and I am talking about short-term moving average, not just overall...

    Now, ok, in a "traditional" plane (including Boeing FBW), you pull say 1/4 back and the plane quickly stabilizes at the new AoA and eventually it will reach its new speed of equilibrium for that AoA (after the phugoid oscillations if not dampened by the pilot or the FBW).

    Now, in an Airbus in normal or alternate law, pull back 1/4 and it means keeping more than 1G, there is no equilibrium to be reached ever with the control pulled anything back. Even in normal law when the speed goes down it transitions from G-on-stick to pitch-rate-on-stick so in both cases it would keep pitching up indefinitely, if it's not by protections (most of them lost in alternate law) or physical limitations (like stalling).

    Now, the pilot when hand-flying (the same than a driver when driving) is part of a closed-loop control system. You just don't put the elevator at 1/4 back and leave it there. You have a performance goal in mind (remember that conversation???) and compare the actual performance with the desired performance and make the necessary adjustments in the control. That's why you see the pilots moving the yoke or stick almost all the time in an approach to landing. Now, what was the performance goal that this pilot had in mind again???? Because the way that he was beating mayonnaise with the stick has no rational correlation with him trying to achieve any specific performance. The point is not what was the instantaneous position of the stick at each second. The point is that by doing what he did with the stick he actively performed an unsustainable skyrocketing climb (and he might have lost the speeds but the other 8 instruments were consistent with this crazy climb) and, when a warning that is actually an APPROACH to stall warning sounded, he pulled up again sending the pitch up again and the AoA with it and actively stalling the plane, and kept pulling up on average whcih made the AoA increase to 40 degrees, ignoring the fact that the pitch was showing 10 deg up, the vertical speed was 10K fpm down, the altimeters were unwinding like crazy, and did I mention the stall warning that since the first "stall" announcement at the top of the climb was sounding uninterruptedly for 30 seconds?

    Say that you drive the car in a road that is straight but a bit uneven and there are gusting crosswinds. You will need to make permanent adjustments to keep the car on the desired lane, and you will compare the actual track of the car with the desired track (i.e. keep the lane) to make continuous adjustments in the steering wheel. If you start to move the steering wheel all over the place but with a clear average to the left, you will very soon depart the road and then declare "but I was NOT turning left all the time".

    Even the pilot admitted that "I was pulling up all the time". While if you read the fine print that is not exactly what he did at each instant, it is clear that that was his main focus and what he did on average (again, even short-term moving average).
    Gabriel, I concede that the aircraft was pitching up the entire time. I believe his intention might have been initially to regain lost altitude and arrest sink rate and then to climb to FL37, and his performance goal was to expedite that climb as much as possible. I am only concerned with the first 45 seconds or so of the event, because, if a crew can't stabilize and establish clear situational awareness by then, we should expect situational awareness to entirely degrade, mental performance to entirely degrade and, after that, anything can happen. In short, it can never go that far.

    So, I'm asking you to do two things that you thus far refuse to do: 1) concentrate on the first 45 secs (the first two pages on the FDR) and 2) look at it carefully. What do you see?

    You see variable pitch inputs (load factor commands) that include forward stick inputs. He is not 'pulling up the entire time'. He seems to be attempting to maintain an expedited but sustainable climb angle (with an unpracticed and panicked hand). There are initially two stall warnings, one at 2h 10min 10 and another 3 secs later. The warnings then cease for another 45 secs or so (in other words, for the rest of the time period we are concerned with). Immediately following these warnings, the thrust is removed from thrust lock and placed in full CL (N1 goes from around 80% to around 100%), which, along with the abatement of the stall warnings, may have led the pilot to think the climb was sustainable. He wouldn't have been wrong about that. The initial climb was sustainable. The aircraft did not stall. Then, following the instruction of the senior F/O, the pilot enters a period of decreased pitch attitude (from 12deg down to 6deg) and decreased vertical speed (from 7000fpm down to 1100fpm). This trend then continues for about 25 secs (to the end of the period I am concerned with).

    Yes, he is still pitching up the entire time, but clearly his intention is not to climb the entire time or to continuously increase the angle-of-attack. Your interpretation of a 'crazy, continuous pull up into a stall' does not synch with reality. What happens after this crucial time interval does appear crazy (I suspect he began following the FD's which had suddenly reappeared since a procedure wasn't there to assure they were switched off), but, as I've said, if it ever gets to that point we have to consider the game lost anyway.

    So, if you have any interest in understanding what might have driven his initial mistakes (and thus find ways to create defenses against them), look more closely at the FDR. If you want to just call it 'crazy' and describe his actions in absolute terms, then don't bother.

  3. #23
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    Quote Originally Posted by elaw View Post
    Can you provide a list?


    It's funny... this thread got me to thinking about something and it is this: in an airliner, is it *ever* appropriate to hold the column/stick at its rearward stop for more than 5 or10 seconds? Ever? Ever? I mean when flying of course, maybe there's some reason to do it on the ground.
    In a CFIT escape situation, the memory item calls for the stick to be held full aft until such time as we're out of CFIT danger. The caveat being that we're talking about an envelope-protected aircraft.

  4. #24
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan
    concentrate on the first 45 secs
    Ok in the first 45 seconds...he pulled up moderately aggressively in a manner consistent with causing a stall, when "the correct procedure" was to maintain a reasonably stable attitude. This is absolutely one of the wrongest things you can do and goes against almost all fundamentals.

    Then after 45 seconds, he pulled up in a different aggressive manner consistent with causing a stall. This, also, is absolutely one of the wrongest things you can do and goes against almost all fundamentals.

    I get your hair-splitting on variations within a relentless pull up, and your attempt to discern the coveted "thought process"...nevertheless it is STILL totally whacko-wrong regardless of your timeslice, and probably irrelevant that they had different thoughts at different times....what they did was hellaciously wrong most of the time, and I am just an uber-ass-hat-unqualified-parlour-talker and pretty sure I would have done better.
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    My simplistic take on this accident is that the confusion and stress caused by a failure in some systems and the move to a joystick led to a loss of an adherence to first principles. I asked quite recently if the artificial horizon worked independently and was assured that it does. Similarly, in this case the altimeter was delivering reliable data. The failure by three highly trained pilots to assess and interpret the information from these two sources and to act accordingly is difficult to understand. To return to the joystick.This is tucked away and gives little in the way of visual clues as to any egregious mishandling. I would suggest that if the three pilots had seen a yoke being pulled back against the stops, a very large mutual thought bubble containing the word "stall" might have appeared.

  6. #26
    Senior Member Evan's Avatar
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    Quote Originally Posted by pegasus View Post
    My simplistic take on this accident is that the confusion and stress caused by a failure in some systems and the move to a joystick led to a loss of an adherence to first principles. I asked quite recently if the artificial horizon worked independently and was assured that it does. Similarly, in this case the altimeter was delivering reliable data. The failure by three highly trained pilots to assess and interpret the information from these two sources and to act accordingly is difficult to understand. To return to the joystick.This is tucked away and gives little in the way of visual clues as to any egregious mishandling. I would suggest that if the three pilots had seen a yoke being pulled back against the stops, a very large mutual thought bubble containing the word "stall" might have appeared.
    1) The altimeters are dependent on airspeed data and are thus compromised by a pitot failure. The error is on the order of approximately 300ft. The vertical speed indicator is also erronous. The only 'good' basic flight instrument on the PFD is the artificial horizon. That is why the procedure must stress the need to fly by pitch, not by any of the other instruments.

    2) During the critical first minute, the stick was never pulled back to the stop. That is a myth that perpetuates on internet forums, including this one. This only occurred after the plane was fully stalled. Also, the stick inputs were very active, ranging from backward (nose up) to forward (nose down). Watching the stick movements would not have told the story. Watching the artificial horizon would have however.

  7. #27
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    1) The altimeters are dependent on airspeed data and are thus compromised by a pitot failure. The error is on the order of approximately 300ft. The vertical speed indicator is also erronous. The only 'good' basic flight instrument on the PFD is the artificial horizon. That is why the procedure must stress the need to fly by pitch, not by any of the other instruments.
    Do you mean that the 3 altimeters and 2 vertical speed indicators did not capture the essence of the zoom climb with the altimeters winding up quickly and the vertical speed indicator showing thousands of feet per minutes up? (besides the artificial horizon showing an attitude that is unsustainable at those altitudes).

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  8. #28
    Senior Member Gabriel's Avatar
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    First 20 seconds starting at AP disconnect (red vertical line).

    Click image for larger version. 

Name:	AF447 FRD.JPG 
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    It's forums. The answers you get don't relate to the point that is being made. In basic airmanship, if you saw the pilot sawing back and forth with the yoke and the altimeter was unwinding in a frightening way, the artificial horizon would be the first point of reference to restore a safe attitude. The absence of this visceral response poses the question - are they flying or trying to manage a system. Or has the balance between the two been lost?

  10. #30
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    Do you mean that the 3 altimeters and 2 vertical speed indicators did not capture the essence of the zoom climb with the altimeters winding up quickly and the vertical speed indicator showing thousands of feet per minutes up? (besides the artificial horizon showing an attitude that is unsustainable at those altitudes).
    No. I mean they are unreliable and will give misleading indications, specifically, that you are now in a descent and must command some load factor to regain your previous flight level. This will result in increased pitch, a departure from level flight and a speed reduction. This is where it begins to go wrong.

    What you want is to maintain your current flight path with as little deviation as possible. That requires you to focus on the artificial horizon, not the altimeter, not the VSI.

  11. #31
    Senior Member Evan's Avatar
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    Quote Originally Posted by pegasus View Post
    are they flying or trying to manage a system?
    Yes.

  12. #32
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    Quote Originally Posted by Evan View Post
    No. I mean they are unreliable and will give misleading indications, specifically, that you are now in a descent and must command some load factor to regain your previous flight level. This will result in increased pitch, a departure from level flight and a speed reduction. This is where it begins to go wrong.

    What you want is to maintain your current flight path with as little deviation as possible. That requires you to focus on the artificial horizon, not the altimeter, not the VSI.
    According to yourself, he was going to pull up anyway because he had decided to climb to 37000 ft.
    If he attempted to correct a 300 ft deviation with such a zoom climb, he lacked basic airmanship
    Now, if he instead attempted to climb to 37000 ft with that zoom climb, he lacked basic airmanship.

    (when I say "lacked" I mean at that specific moment, which can be the result of reacting under terror, shutting down the rational mind, or just lacking that airmanship in the first place)

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  13. #33
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    According to yourself, he was going to pull up anyway because he had decided to climb to 37000 ft.
    If he attempted to correct a 300 ft deviation with such a zoom climb, he lacked basic airmanship
    Now, if he instead attempted to climb to 37000 ft with that zoom climb, he lacked basic airmanship.

    (when I say "lacked" I mean at that specific moment, which can be the result of reacting under terror, shutting down the rational mind, or just lacking that airmanship in the first place)
    No, according to me he might have made intial pitch-up inputs to arrest a false descent and regain his current flight level, then he might have decided to continue climbing to his desired flight level. Two separate intentions, but the first one has him departing the stable (in pitch) flight path, so it could open the door for further improvisation.

    If he had it installed in his mind that, when the auropilot suddenly disconnects during cruise, and a quick crosscheck of airspeeds shows a disagree, to maintain level flight by pitch attitude and only pitch attitude and to do nothing else (aside from the FD and thrust lock issues) for 1-2 minutes, this wouldn't have happened. Without such a memorised procedure, with only 'airmanship', that leaves the door wide open for stealth, deception and poor judgment, and, as you well know, there are pilots up there vulnerable to deception with potentially poor judgement under fire.

    Gabriel. do you disagree with either of these statements:

    1) The altimeters are dependent on airspeed data and are thus compromised by a pitot failure. The error is on the order of approximately 300ft. The vertical speed indicator is also erronous. The only 'good' basic flight instrument on the PFD is the artificial horizon. That is why the procedure must stress the need to fly by pitch, not by any of the other instruments.

    2) During the critical first minute, the stick was never pulled back to the stop. That is a myth that perpetuates on internet forums, including this one. This only occurred after the plane was fully stalled. Also, the stick inputs were very active, ranging from backward (nose up) to forward (nose down). Watching the stick movements would not have told the story. Watching the artificial horizon would have however.

  14. #34
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    Gabriel. do you disagree with either of these statements:
    Yes I do. With both of them.

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  15. #35
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    Yes I do. With both of them.
    Well then I give up.

  16. #36
    Senior Member Gabriel's Avatar
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    Let me clarify a bit. Your statements are quite black and white, and capricious at some points.

    The only "perfect" instruments in the PFD were the AI. The altimeters and vertical speed indicators were "good enough". And you can't miss 1.5G. Oh, and the AIs were perfect too, right?. Not doing anything crazy when the AP disconnects is basic airmanship. Even if you want to climb or something, first stabilize and get your wits. There was more than enough information on those 3 PFD to get feedback and not do what the pilot did. The FDR plot as I posted it in my previous post is a testament of that.

    During the 1st minute? What's magical in a minute? You want to only focus in what happened before the stall because, you claim, that by then the situational awareness that we could not expect that the pilot would pull aggressively up when the stall warning sounded shouting "stall" in plain English. Then I offer you the first 20 seconds where the pilot actively entered that zoom climb and let it happen (because the story could have been that he unintentionally pulled up too much and when he saw the pitch, altitude and vertical speed going up as crazy he corrected, but that's not what happened). Please integrate the stick input during the first 20 seconds. How do you explain that? How do you explain that he keeps a mostely nose-up input for 20 seconds while the parameters are showing a climb that is off the charts? So I propose that the situational awareness was out of the window already by 20 seconds. Or by 2 seconds. Sure, he did timidly let the nose go down after the PM told him to do so. But by when he stabilized the energy situation had horribly deteriorated that even in a mild descent in slightly less than 1G the stall warning AoA was exceeded (by the way, the plane stopped climbing but the pitch attitude was still excessive, ESPECIALLY if the plane is not climbing). They were behind the power curve by then and the only way out was to trade potential energy for kinetic energy, i.e. trade altitude for speed. It was an unsustainable climb (even if you say it wasn't) and the only way to recover from such is to undo the climb. It would have taken quite e bit of situational awareness to void the stall warning at that point, it would have NOT taken barely any situational awareness to react to the stall warning by pushing the nose down. But I want to focus in the first few seconds again. And I said this a gazillions of times. I don't trust this pilot to apply any memory item or procedure under stress. The way he reacted was irrational. And he reacted irrationally since the beginning of the event. His situational awareness did not deteriorate during the event. It was never there since the AP disconnected. Why? I don't know. It could be that he just didn't have the tools in his toolbox. Or it may be that the tools feel out the toolbox the minute that the fit hit the shan.

    Why I didn't say all this in my previous reply? Because I've already said it many times. That's why I've said a few days ago, just like you did now, "I give up". But I am a fool.

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  17. #37
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    Let me clarify a bit. Your statements are quite black and white, and capricious at some points.

    The only "perfect" instruments in the PFD were the AI. The altimeters and vertical speed indicators were "good enough". And you can't miss 1.5G. Oh, and the AIs were perfect too, right?. Not doing anything crazy when the AP disconnects is basic airmanship. Even if you want to climb or something, first stabilize and get your wits. There was more than enough information on those 3 PFD to get feedback and not do what the pilot did. The FDR plot as I posted it in my previous post is a testament of that.

    During the 1st minute? What's magical in a minute? You want to only focus in what happened before the stall because, you claim, that by then the situational awareness that we could not expect that the pilot would pull aggressively up when the stall warning sounded shouting "stall" in plain English. Then I offer you the first 20 seconds where the pilot actively entered that zoom climb and let it happen (because the story could have been that he unintentionally pulled up too much and when he saw the pitch, altitude and vertical speed going up as crazy he corrected, but that's not what happened). Please integrate the stick input during the first 20 seconds. How do you explain that? How do you explain that he keeps a mostely nose-up input for 20 seconds while the parameters are showing a climb that is off the charts? So I propose that the situational awareness was out of the window already by 20 seconds. Or by 2 seconds. Sure, he did timidly let the nose go down after the PM told him to do so. But by when he stabilized the energy situation had horribly deteriorated that even in a mild descent in slightly less than 1G the stall warning AoA was exceeded (by the way, the plane stopped climbing but the pitch attitude was still excessive, ESPECIALLY if the plane is not climbing). They were behind the power curve by then and the only way out was to trade potential energy for kinetic energy, i.e. trade altitude for speed. It was an unsustainable climb (even if you say it wasn't) and the only way to recover from such is to undo the climb. It would have taken quite e bit of situational awareness to void the stall warning at that point, it would have NOT taken barely any situational awareness to react to the stall warning by pushing the nose down. But I want to focus in the first few seconds again. And I said this a gazillions of times. I don't trust this pilot to apply any memory item or procedure under stress. The way he reacted was irrational. And he reacted irrationally since the beginning of the event. His situational awareness did not deteriorate during the event. It was never there since the AP disconnected. Why? I don't know. It could be that he just didn't have the tools in his toolbox. Or it may be that the tools feel out the toolbox the minute that the fit hit the shan.

    Why I didn't say all this in my previous reply? Because I've already said it many times. That's why I've said a few days ago, just like you did now, "I give up". But I am a fool.
    It's because we are talking at cross purposes. My purpose is twofold. 1) to try to make sense of what he did (and I have, in theory, and it's not just my theory) and 2) to suggest methods for creating a reliable pilot response that neither slows nor accelerates during that critical minute or so.

    So, one the first purpose, I'm stated it as clearly as I can. Yes, we all know that he zoom climbed. I think that was his intention. The climb was likely exaggerated by unpracticed skills and/or panic but WAS sustainable. He succeeded. I see this as the opposite of a rapid descent instinct during a decompression event. The instinctive need to get to a safer flight level. It was the wrong thing to do. It was poor airmanship. You don't have to keep making that point. I've never disputed that. But perhaps it can be explained...

    On the second purpose, you say the altimeters and VSI's were "good enough". Good enough for what? To maintain flight level without slowing or accelerating? No. Not if you fly by them. They will compel you to increase your pitch and thus decrease your speed. If your hand isn't practiced at this flight level (and most aren't) you might over-control. Will that result in a 7000fpm climb to a higher flight level? No. That would require a different intent. Will it cause you to lose your previous 'known' place in the speed envelope with no airspeed reference. Yes.

    Seriously Gabriel, of all the pilots interviewed on their UAS incidents prior to AF447, how many got out of thrust lock? How many switched off the FD's? How many maintained level flight and their 'known' place in the speed envelope? Perhaps a procedure is needed here...

  18. #38
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    Gabriel, of all the pilots interviewed on their UAS incidents prior to AF447, how many got out of thrust lock? How many switched off the FD's? How many maintained level flight and their 'known' place in the speed envelope? Perhaps a procedure is needed here...
    Evan: Do I hear your right?...Bonin wanted to do a reasonable climb, but since he was out of practice, he mistakenly initiated a climb that was a bit to aggressive???

    Can you maybe give me a simple black or white, yes or no?

    I'm with you on that much.

    Where I lose you (and maybe join Gabe), is that super mega uber ultimate basic airmanship is that the overly aggressive climb should have PROMPTLY been adjusted to a FDnH climb with more than adequate (albeit imperfect) instrumentation.

    The attitude indicator, the altimeter, the DGINS were extremely adequate to discern an aggressive-great-way-to-stall climb from a FDnH climb.

    Just can't give your "thought" much credence past 5 seconds unless it was total freak out loss of ALL RATIONAL THOUGHT for pretty much the final couple of minutes of flight.
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  19. #39
    Senior Member Evan's Avatar
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    Quote Originally Posted by 3WE View Post
    Evan: Do I hear your right?...Bonin wanted to do a reasonable climb, but since he was out of practice, he mistakenly initiated a climb that was a bit to aggressive???

    Can you maybe give me a simple black or white, yes or no?
    It's a theory I find reasonable, as opposed to the theory that he lacked the most fundamental airmanship, which I find unreasonable.

    Where I lose you (and maybe join Gabe), is that super mega uber ultimate basic airmanship is that the overly aggressive climb should have PROMPTLY been adjusted to a FDnH climb with more than adequate (albeit imperfect) instrumentation.
    I don't think he was in a FDnH mood for some reason. I think he was executing what we might call an "emergency climb", probably trying to get the maximum possible climb rate. He pretty much did. The stall warning was momentary. Mostly he stayed within the edge of the performance envelope.

    The attitude indicator, the altimeter, the DGINS were extremely adequate to discern an aggressive-great-way-to-stall climb from a FDnH climb.
    Agreed. I never tried to suggest anything to the contrary. My concerns with the unreliable instruments concern an attempt to arrest a false sink rate and 'regain' lost altitude, which might lead to further improvisation. They have nothing to do with concealing a determined climb like this.

    Just can't give your "thought" much credence past 5 seconds unless it was total freak out loss of ALL RATIONAL THOUGHT for pretty much the final couple of minutes of flight.
    Open your mind, then try it.

    The "total freakout" seems to occur about a minute after the loss of autopilot. This, to me, is more mysterious. He had climbed to 37,500. He had agreed to "go back down". He had reduced his pitch commands and pitch had reduced back to around 6° ANU. He had 216kts airspeed and AoA was around 5°. Then, for some reason, he pulled back up into a 3000fpm climb, reaching almost 18° ANU pitch. His inputs were still never full stop and many were reductions including three forward pushes well past neutral, so it doesn't seem to be a Renslow-type freakout. My only guess is that he was following the FD's which did suddenly reappear at that time and were giving instructions similar to his stick inputs. Had they followed a procedure and switched them off...............

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