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  • #31
    No deal.

    Originally posted by Sweet Monkey River Flight School Del Norte Manual
    As there is usually some wind variably, there will be attitude and airspeed checks, up and down pitch adjustments, right and left roll adjustments and left and right yaw adjustments. Most of this will be done with minimal thought. Most of the thinking will focus on whether the attitude, airspeed and flight is healthy and why it became unhealthy and triggered a stall warning.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    • #32
      Originally posted by 3WE View Post
      No deal.
      You forgot:

      Originally posted by Sweet Monkey River Flight School Del Norte Manual
      As airplanes are not all the same, and avionic features and aerodynamic behaviors differ, there will be sufficient type-specific knowledge required in addition to attitude and airspeed checks, up and down pitch adjustments, right and left roll adjustments and left and right yaw adjustments. Some of this thinking will focus on whether the selected Vref is 20kts lower the stall warning reference speed selected by the reference speeds switch. Some of this thinking will focus on whether the aircraft is or isn't susceptible to tail stalls. There will also be training on the effect of sudden, unexpected events altering the performance envelope of the human mind and why such events should be minimized through type-specific training.

      Comment


      • #33
        Originally posted by Evan View Post
        You forgot:
        You misread.

        Earlier in the thread I state that 16 to 17 degrees AOA = a stall and Gabriel says AOA is the only thing I can think about.

        Please tell me what % of planes stall at other AOAs and situations where measured, monitored and yes, adjusted pitch inputs (possibility downward and along with airspeed, power and configuration awareness) are incorrect procedures?

        Also, please list instances where relentless pull ups are apropriate.

        Maybe just before crashing, but I think Gabe even disagrees with that with his insistence on AOA reductions.
        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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        • #34
          And fixed:

          Originally posted by Evan’s black and white behind the keyboard from a safety bubble flight school
          Wipe your mind of basic aerodynamics and memorize and barf back procedures so when, on a dark stormy night, UAS confuses you and you demonstrate no knowledge of 172 or Airbus stall behavior, which by uncanny coincidence are rather similar.
          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

          Comment


          • #35
            Originally posted by 3WE View Post
            Most of the thinking will focus on whether the attitude, airspeed and flight is healthy and why it became unhealthy and triggered a stall warning.
            The moment that the stickshaker is triggered and caught you by surprise (and chances are that it will catch you by surprise or you would have done something to avoid it in the first place) is THE WORST MOMENT IN EARTH to start figuring out why attitude, airspeed and flight become unhealthy.

            The moment that the stickshaker activates, you know the first level of why: The AoA is too high, and you need to reduce it. So reduce it, return to a stabilized healthy flight (which very well my include adding thrust, but not always, adding thrust would have been impossible or would have not made a difference in Detroit, Barajas, AF and Colgan -where in fact they did add thrust- if you don't also reduce the AoA), and then investigate what went wrong.

            It is the difference to die with the last words being "what is it doing now" and recovering first, then asking "why was it doing that", and not dying.

            And Evan, by all means, go and learn the type-specific details, but there is no airplane in the World where reducing the AoA is not the right procedure to recover from a stall or approach to stall, and there is no plane in the World where the elevator (including elevator trim) is not the main means to control (and hence to reduce) the AoA. There is no plane in the world where doing like the Colgan and AF pilots is appropriate in the situations that they were facing, not even in the little Cessna 172s where they first learned to fly and first learned stalls.

            --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
            --- Defend what you say with arguments, not by imposing your credentials ---

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            • #36
              Originally posted by Gabriel View Post
              The moment that the stickshaker is triggered and caught you by surprise (and chances are that it will catch you by surprise or you would have done something to avoid it in the first place) is THE WORST MOMENT IN EARTH to start figuring out why attitude, airspeed and flight become unhealthy.

              The moment that the stickshaker activates, you know the first level of why: The AoA is too high, and you need to reduce it. So reduce it, return to a stabilized healthy flight (which very well my include adding thrust, but not always, adding thrust would have been impossible or would have not made a difference in Detroit, Barajas, AF and Colgan -where in fact they did add thrust- if you don't also reduce the AoA), and then investigate what went wrong.
              To provide context of how much time they had from ~2000 feet, it was ~30 seconds from initial stick shaker to ground impact. From the video, it looks to me that his initial pull up reaction cost them 15-20 seconds of bleeding off more speed at which time it was too late to do anything to save them. Not much time to do anything other than react at those speeds and altitudes.

              I can't even imagine the SO PNF making any difference fighting for controls in that short time frame and we know in this case from the conversation in the flight deck, that there is no way she would have had the confidence (or understanding) to do that.

              Comment


              • #37
                Originally posted by Gabriel View Post
                The moment that the stickshaker activates, you know the first level of why: The AoA is too high, and you need to reduce it.
                Except in this case. The AoA was fine. It didn't need to be reduced. Pitch remained below 10° @ 130kts. The problem that brought on stickshaker was entirely airspeed, specifically maintaining a 20kt safety margin above normal Vref to allow for potential ice contamination.

                And Evan, by all means, go and learn the type-specific details, but there is no airplane in the World where reducing the AoA is not the right procedure to recover from a stall or approach to stall.
                And Gabriel, of course I realize that. You have to read my actual words and not 3WE's trolling satires of them.

                The VERY BEST upset avoidance procedure is to never fly into an upsetting situation. Because upset recovery doesn't always go so well. Because humans.

                Comment


                • #38
                  Originally posted by Evan View Post
                  Except in this case. The AoA was fine. It didn't need to be reduced.
                  You are wrong.
                  The problem that brought on stickshaker was entirely airspeed, specifically maintaining a 20kt safety margin above normal Vref to allow for potential ice contamination.
                  You are wrong.

                  The stickshaker is ALWAYS activated by AoA. The margin to allow for potential icing contamination is also in AoA, and it is equivalent (in this plane) to 20kts at 1G, as long as the wing is clean. If the wing is iced up, you carrying more weight than the "official" weight of the plane at the moment (beacuse of the weight of the ice), and the wing is producing less lift at any AoA (because of the wing), then the stickshaker with the ice switch on may very well activate moroe than 20 knots faster than it normally would with the switch off and a clean wing.

                  But the stickshaker activated, and it did so because the AoA was too high, and if that bothereed the pilot and he wanted to make the stickshaker stop, he had to reduce the AoA in some way or another. Adding thrust to increase the speed while keeping either the pitch or the altitude constant would have done so, since the AoA would have needed to be reduced to keep either the pitch or the altitude in a context of increasing speed.

                  Now, it is easy for us to say NOW that they were 20 knots faster than the "normal" stickshaker speed. But it took the NTSB an engineering performance simlation to know that. They did not know that they were 20 knots faster than the 1G stickshaker speed (ice switch off). Neither would have you, or me or Sully.

                  The crew had turned the ice switch on for a reason (because they were flying in conditions that were potentially prone to icing) and the ice switch adds the margin on the stall AoA for a reason. If you say "ok, the stickshaker activated early because we have the ice switch on, but there is no risk, we are 20 knots faster due to the margin", you are overriding the safety feature than the change in the stickshaker, in the airspeed indicator, and in the Vref speeds are supposed to provide. You don't do that. Reacting immediately to the stickshaker activation in the correct way is the only correct move (unless you judge it to be false). There is only 1 correct way to react to it (or, let me correct that, more than one, as long as all of them mean reducing the AoA), and pulling hard on the yoke is certainly not among them.

                  The VERY BEST upset avoidance procedure is to never fly into an upsetting situation. Because upset recovery doesn't always go so well. Because humans.
                  Agreed 100%, but then avoiding the upset can also go wrong. Because humans.

                  --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                  --- Defend what you say with arguments, not by imposing your credentials ---

                  Comment


                  • #39
                    Originally posted by Gabriel View Post
                    The moment that the stickshaker is triggered and caught you by surprise (and chances are that it will catch you by surprise or you would have done something to avoid it in the first place) is THE WORST MOMENT IN EARTH to start figuring out why attitude, airspeed and flight become unhealthy.
                    Sorry for the lack of clarity- Addresing the stall warning with full power, monitoring, adjusting, and maybe just maybe a touch of nose over, is done with minimal thinking...automatic as Evan likes to see, but it’s ok to think about 172 methods even if you are in an airliner.

                    THEN, AFTER things are healthy...

                    THEN think and analyze why you got into the predicament.

                    I believe you describe something similar in your further comments.

                    Agree.
                    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                    Comment


                    • #40
                      Originally posted by Gabriel View Post

                      The stickshaker is ALWAYS activated by AoA.
                      You are wrong. The speed reference switch increases the stall SPEED by 20kts. Yes, that equates to triggering stickshaker at a lower AoA (eristic argument), but almost-critical AoA did not activate the stickshaker here, so there was no need to reduce AoA. The stickshaker was activated by AoA + speed margin. I understand why it exists. I understand that IF the wing is iced, that is a wise precaution. But the wing wasn't iced, the AoA wasn't critical and thus...

                      The moment that the stickshaker activates, you know the first level of why: The AoA is too high, and you need to reduce it.
                      Is wrong. In this case you don't know the first level of WHY. Let me tell you why that seemingly technical distinction is important here.

                      The incident occurred because the F/O set the Vref bugs for a normal (non-icing-condition) speed of 118kts. The PIC set the reference speeds switch to INCR, but I'm 99.99% sure he did that as a checklist item, not understanding the ramifications (see: Type-Specific Training). When the stickshaker activated well above the bug, HE DID NOT KNOW THE FIRST LEVEL OF WHY. Because the AoA (pitch and speed) appeared healthy AND he wouldn't have expected the stickshaker to magically compensate for contamination (see: SAAB 340 and every stickshaking thing he'd ever flown before). So his mind had to either invent an answer, or panic because it had none.

                      I'm not arguing with you about the REACTION to stickshaker being all wrong. I'm trying to point out that there was a stealth factor involved that could very well have shattered his situational awareness and could very well explain the very wrong thing that he did. Not excuse it (when blaming the company), but explain it. If you don't take that into consideration (as the NTSB specifically has) you can't ever make any sense out of this.

                      I feel pretty sure if you could go to pilot heaven and ask him "why did you do that", he would say "I can't explain it. I don't even know what happened." But the important thing is what we do to prevent it from happeneing again. Teaching stall-avoidance alone will not do. There is no universal airmanship that, alone, is adequate for modern airliners. Without PROFICIENT type-specific knowledge of avionics and particular behaviors of the type you are entrusted with, you are an accident waiting to happen. Because, human.

                      Comment


                      • #41
                        Originally posted by Evan View Post
                        You are wrong. The speed reference switch increases the stall SPEED by 20kts. Yes, that equates to triggering stickshaker at a lower AoA (eristic argument), but almost-critical AoA did not activate the stickshaker here, so there was no need to reduce AoA. The stickshaker was activated by AoA + speed margin.
                        Whaaaaaat?????? I don't understand what you are saying.

                        1- The sticksahker is activated by AoA. Which AoA depends on the position of the "ice" switch (which I guess is the INCR that you mention). How much the speed will be increased depends mainly on a) wight and 2) load factor. It is not a "20 knots across the board" offset because it is an angle of attack offset, not a speed offset (to the point that it is actually tested, both in icing and non-icing conditions, at 1.5Gs and the speed obtained is then corrected backwards with the sqrt of the load factor to obtain what would be the speed at 1G, which is the used to establish other refeence speeds, like Vref, Vr, etc.).
                        2- There was no need to reduce the AoA????? So would you propose to keep flying happily with the stickshaker shaking, pulling the stichsahker CB, or setting the reference speeds to non-INCR in conditions that could be conductive to icing? Do I need to remind you of the previous accidents that triggered this change / improvement in defining stall speed and reference speeds in icing conditions?
                        3- Almost critical AoA not activating the sticksahker... well it was the AoA that would have been critical had the plane accreted ice as specified in 14 CFR part 25. In hindsight, it was not critical, but you have to consider that it is when you are in that situation because you just don't know so you go conservative. And I agree that he probably don't understand that, now when the stickshaker goes out you have basically 2 options: a) Execute the recovery procedure or b) judge it false, and I would recommend that if you believe it is false, you still execute the recovery procedure if it is safe to do so and then confirm or correct your judgement based on the result. In any event, pulling up is not the right response to a stickshaker, no matter what.

                        I feel pretty sure if you could go to pilot heaven and ask him "why did you do that", he would say "I can't explain it. I don't even know what happened."
                        Possibly. But other options that I consider not less likely are:
                        - "I pulled up because I thought it was a tail stall"
                        - "My intention was to add full thrust and keep a pre-established pitch attitude, as per the defined approach-to-stall recovery procedure, but I was sloppy and could not execute it with precision and the plane started to roll violently one way or the other which I also tried to compensate for together with trying to control the pitch, and it was more than I could handle".
                        - "I panicked that we were going to crash and I just wanted to gain altitude as quickly as possible".

                        --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                        --- Defend what you say with arguments, not by imposing your credentials ---

                        Comment


                        • #42
                          Originally posted by Gabriel View Post
                          Whaaaaaat?????? I don't understand what you are saying.
                          I added all those caveats in my last post, but in essense, just as the AFM calls for a 20kt increase in reference speeds for icing conditions, the system in the INCR position calculates a lower threshold AoA that will increase the onset of barberpole (and thus stickshaker) on the speed tape by 20kts in flaps 5-15 configuration. If ice is detected and the reference speeds switch is not in the INCR position, a message on the engine display prompts the pilot to switch it there. It doesn't explain what it does or how it works or instruct the pilots to also reset the bugs accordingly, only proper training does this, so if the pilots are not familiar with the function of the reference speeds switch, and just follow the switch prompt, they are in for a surprise. We don't like surprises. We don't want to startle pilots, especially fatigued ones at critical phases of flight. If you want to ignore the point I'm making, so be it, I'll just have to give up.

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                          • #43
                            And I am not ignoring it. I am agreeing with it. But, as always, is not one thing or the other. It is one thing AND the other. The pilot should haven better trained to know what the INCR does (type specific) and whould not have reacted as he did upon the stall warning (universal).

                            --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                            --- Defend what you say with arguments, not by imposing your credentials ---

                            Comment


                            • #44
                              Originally posted by Gabriel View Post
                              But, as always, is not one thing or the other.
                              But when have I ever said that? All I've been saying all along is that it's NOT just the one thing (basic airmanship).

                              Comment


                              • #45
                                Evan, do you have any source for this? In particular, do you have access to an AFM, FCOM or training manual?

                                I added all those caveats in my last post, but in essense, just as the AFM calls for a 20kt increase in reference speeds for icing conditions, the system in the INCR position calculates a lower threshold AoA that will increase the onset of barberpole (and thus stickshaker) on the speed tape by 20kts in flaps 5-15 configuration.
                                I don't think that this is correct. I found no 100% solid info, but from the AAR and other loose pieces information I found in the internet, I am more convinced than before that it is 100% an AoA thing and hence the Vref speed for icing conditions have to be specifically chosen from a table which is affected by airplane weight and configuration, and the speed at which the stickshaker will activate will depend on that (weight and config) and also load factor, because it will activate when it reaches a given AoA (which AoA? depends on config and ref speeds switch position) and, once you have the AoA, the speed at which it activates (with the wing clean) is affected by the weight and load factor as given by L=nW=1/2*r*v^2*CL*S (L: lift, n:load factor, W: weight, r: air density, v: true airspeed, CL: coefficient of lift which is a function only of AoA, S: reference area (fixed value, normally the wing area in clean config).

                                So, in the same way that Vref is not one fixed value (because Vsr is not a fixed value), I don't believe that the increase will be a fixed value (because the increase in Vsr will not be a fixed value).

                                --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                                --- Defend what you say with arguments, not by imposing your credentials ---

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