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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
    Member ATLcrew's Avatar
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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.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  5. #25
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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.

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