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Did we almost lose another Air France widebody?

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  • Did we almost lose another Air France widebody?

    The benefits of hard envelope protections under windshear. A mostly unforseeable windshear situation left the crew of an A340 unable to climb, nearing the end of the runway with nothing but pitch to work with. Normal law protections allowed them to make the most of it without stalling. The aircraft initially remained at 5ft AGL with 13deg of pitch. They entered alpha protect in the process and remained there until the runway end when the tailwind decreased and the aircraft began to climb—passing the runway end at 58ft AGL.

    Hate to imagine what a stall would do in this scenario.

    http://avherald.com/h?article=4d03af41&opt=0

  • #2
    Originally posted by Evan View Post
    The benefits of hard envelope protections under windshear. A mostly unforseeable windshear situation left the crew of an A340 unable to climb, nearing the end of the runway with nothing but pitch to work with. Normal law protections allowed them to make the most of it without stalling. The aircraft initially remained at 5ft AGL with 13deg of pitch. They entered alpha protect in the process and remained there until the runway end when the tailwind decreased and the aircraft began to climb—passing the runway end at 58ft AGL.

    Hate to imagine what a stall would do in this scenario.

    http://avherald.com/h?article=4d03af41&opt=0
    Yep. Terrain escape, windshear escape in an Airbus is quite piece of cake: Firewall the throttles (if not already there) and pull back to the stops on the sidestick. Let HAL do the rest.

    But it CAN be done in "traditional" planes too: Here you have a 747:

    The investigator confirmed, that the thrust reversers for engines #2 (inner left) and #3 (inner right) indicated unlocked during the takeoff roll beyond V1 leading to the automatic retraction of leading edge flaps in accordance with the system design. The stick shaker activated at 12 feet, the crew levelled off at 35 feet, picked up speed and then resumed the initial climb.

    https://avherald.com/h?article=4198598d&opt=0

    --- 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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    • #3
      Loss of a significant amount of lift on rotation during the takeoff caused by the automatic LE flap retraction logic retracting the Group ‘A’ LE flaps on receipt of spurious thrust reverser unlock signals from the no. 2 and no. 3 engines.
      Wowsers! What's it doing now, eh?

      I thought you would cite that one time in the sim when you rode out the wave of stickshaker activation (BoeingBobby owes his his simulated life for that one). But flying by buffet, that might have you beat. I thought you could hardly feel it in a 747. The thing is, I have to wonder how many line pilots have aerobatic skills like that vs how many would have stalled it. I know that zero percent would have stalled the A340. Not even the relentless ones.

      Nice to know they AD'd that 747 system behavior out.

      Comment


      • #4
        Originally posted by Evan View Post
        I know that zero percent would have stalled the A340. Not even the relentless ones.
        You can still screw up in an Airbus. Ask Air France, Air France and that acceptance flight with the washed/frozen AoA vanes that I don't remember the airline.

        Bu yes, under normal conditions, in normal law, and if you are not at alpha max with idle trees below the height of the trees, relentlessly pulling up is what will give you the best chance of avoiding a [sound of impact] line in the CVR transcript, and it is more reliable than a pilot using their skills to modulate the elevator so as to keep the AoA around the stickshaker onset.

        This is how a relentless pull-up works in an Airbus, demonstrated by a rock star (and pilot):

        https://www.youtube.com/watch?v=ei_IY8VymbU

        And this is how a youtbe star (and 737 instructor) does it in a 737:

        https://www.youtube.com/watch?v=4qsFI9l0bJk

        --- 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


        • #5
          Originally posted by Gabriel View Post

          You can still screw up in an Airbus. Ask Air France, Air France and that acceptance flight with the washed/frozen AoA vanes that I don't remember the airline.

          Bu yes, under normal conditions, in normal law, and if you are not at alpha max with idle trees below the height of the trees, relentlessly pulling up is what will give you the best chance of avoiding a [sound of impact] line in the CVR transcript, and it is more reliable than a pilot using their skills to modulate the elevator so as to keep the AoA around the stickshaker onset.

          This is how a relentless pull-up works in an Airbus, demonstrated by a rock star (and pilot):

          https://www.youtube.com/watch?v=ei_IY8VymbU

          And this is how a youtbe star (and 737 instructor) does it in a 737:

          https://www.youtube.com/watch?v=4qsFI9l0bJk
          The A320 video is an old one. It still confuses me when he releases the full-right bank input to the hard limit and it rolls to level. I always thought it only rolled back to the 'soft' limit of 33 deg if you released the stick. Perhaps ATL can set us straight on that.

          The 737 video brings up another question: how well do you have a feel for buffet in the 747 when the stick shaker is going off?

          Comment


          • #6
            Originally posted by Evan View Post
            The A320 video is an old one. It still confuses me when he releases the full-right bank input to the hard limit and it rolls to level. I always thought it only rolled back to the 'soft' limit of 33 deg if you released the stick.
            I also noted that, I think Bruce just made a mistake there. The video is clearly edited in a way that what Bruce is speaking and what the plane is doing are not happening simultaneously.

            --- 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


            • #7
              Originally posted by Evan View Post
              ***The thing is, I have to wonder how many line pilots have aerobatic skills like that vs how many would have stalled it.*** (+weaselly airbus envelope protection comment)***
              1. Slow flight and careful AoA management are not aerobatic skills.

              2. They are SUPER DUPER INCREDIBLY BROAD FUNDAMENTAL SKILLS, THAT I BELIVE ARE AN ACTUAL PART OF RECURRENT TRAINING

              3. I have no phugoid clue if they are written in a QRH, or what form the memory checklist takes....I'm sure they are written SOMEWHERE, but I also file them in cowboy-improvisation stuff where the verbiage from the 172 POH might work pretty damn good.

              4. VERY FEW Boeing pilots would stall their unprotected plane. Probably no more than have stalled the wondorous SORT OF protected, SORT OF unstallable Airbae.

              Boeing Bobby, care to pile on, or are you too busy making popcorn?
              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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              • #8
                Originally posted by 3WE View Post
                Slow flight and careful AoA management are not aerobatic skills.
                No they are not. However:

                The pilot flying, having significant experience with aircraft buffeting due to aerobatics flying, continued to fly the aircraft with the captain, remaining pilot monitoring, calling out aircraft height.
                Line pilots without aerobatics experience (or perhaps aggie experience) do not have 'significant experience with aircraft buffeting'. This pilot had a good instinctive feel for it and used it to fly at the very edge of the envelope. That's great but not really something to rely on in general.

                On the other hand, in a situation where getting every ounce of AoA can be the deciding factor, the Airbus FBW will cut you off a safe margin below what is left. So, best case scenario is probably an unprotected aircraft with a crack pilot at the helm. But note: actual pilots may vary...

                Also note: actual performance of actual pilot under stress and/or panic may vary.

                Comment


                • #9
                  Originally posted by Evan View Post
                  On the other hand, in a situation where getting every ounce of AoA can be the deciding factor, the Airbus FBW will cut you off a safe margin below what is left. So, best case scenario is probably an unprotected aircraft with a crack pilot at the helm.
                  I doubt it. It's like saying that in a situation where getting every ounce of AoA can be the deciding factor in an unprotected plane you can still get away by using the margin between the stickshaker an the actual stall. In reality it doesn't work like that. Remember that the lift-vs-AoA curve flattens at the critical AoA so as you approach the critical AoA the lift doesn't increase as much by farther increasing the AoA.

                  And remember too that lift doesn't depend only on the AoA but also on the speed squared. The drag spikes as you approach the critical AoA, so possibly all that you gain by increasing the AoA that extra degree you lose it with the speed not gained.

                  And that's not all. At around the critical AoA the aileron effectiveness is severely impaired, the adverse yaw skyrockets, and the roll damping is destroyed. That's why many times in a critical AoA situation the plane suffers sever roll excursions which in turn require large roll inputs which means large aileron and roll spoiler deflections that reduce drag lift and increase drag even more.

                  I don't think there is any additional performance to be squeezed after the stickshaker or after alpha max.

                  --- 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


                  • #10
                    Originally posted by Gabriel View Post
                    I don't think there is any additional performance to be squeezed after the stickshaker or after alpha max.
                    I believe you, but I don't think Sully does.

                    Comment


                    • #11
                      Originally posted by Evan View Post
                      Line pilots without aerobatics experience (or perhaps aggie experience) do not have 'significant experience with aircraft buffeting'. This pilot had a good instinctive feel for it and used it to fly at the very edge of the envelope. That's great but not really something to rely on in general.
                      Somehow, I think that Airbus "buffeting" feels (and requires different inputs) than 152 arerobat and Pitts buffeting....

                      Nevertheless, you dismissed that pilots practice slow flight which is beneficial to this situation and I believe that almost all of them may have the ability to use cowboy improvisation to watch their speed, AOA and stall warnings and execute a dang good almost-highest-performance drag it over the fence maneuver.

                      Repeating, as we have seen with Airbus pilots (as well as Boeing ones), there are a rare exceptions.

                      Gabieee does have an oft-cited DC-9/MD-80 example where the technique was less than optimal.



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

                      Comment


                      • #12
                        Originally posted by 3WE View Post

                        Somehow, I think that Airbus "buffeting" feels (and requires different inputs) than 152 arerobat and Pitts buffeting....

                        Nevertheless, you dismissed that pilots practice slow flight which is beneficial to this situation and I believe that almost all of them may have the ability to use cowboy improvisation to watch their speed, AOA and stall warnings and execute a dang good almost-highest-performance drag it over the fence maneuver.
                        That was a 747, but whatever. You can argue with the final report if you'd like.

                        That had nothing to do with watching airspeeds or neglecting fundamentals. But then your mantra about me 'despising' these things also has nothing to do with logic or reality, so...

                        We are talking about escape maneuevers from dire situations where the only way out is to flirt with the onset of stall. Join us.

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                        • #13
                          Originally posted by Me
                          Somehow, I think that Airbus and 747 "buffeting" feels very different (and requires different inputs) than 152 arerobat and Pitts buffeting....

                          Happy now?


                          Originally posted by Evan View Post
                          We are talking about escape maneuevers from dire situations where the only way out is to flirt with the onset of stall. Join us.
                          You pull up very aggressively to specific, high-performance attitudes, monitor and adjust...I remember when they used to teach that and when Gabriel said that procedure was a bit too rote and a bit too blind to stall behavior...because in fact you were flirting stalling.

                          I recall that this provided near optimal performance.

                          I also believe that slow flight practice is a good thing (as long as you pause and think about 'escape maneuvers'.

                          Indeed computer monitored system to stop the AOA at a near optimum performance just above stall can probably slightly out perform a human, as well as simplifying the human's life.

                          Ironingly, there's a theory that someone was relying on this protection when he did his own extremely relentless pull up (even thought his pull up was not 100% full as you cite).

                          I hope pilots continue to occasionally practice slow flight and maybe even aggressive-but-carefully measured, critical pull ups.

                          Repeating- Gabiee's DC-9/MD-80 example is an interesting case (involving WTF/What's it doing now startle aspects). One follow up is improved automatic warning systems.

                          What's new for me to join in on? If there's something TRULY new here, I'll join in. If it's the same old Evan bashing stupid human pilots and calling for more checklists and training and automation, not really interested.
                          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                          • #14
                            Originally posted by 3WE View Post
                            What's new for me to join in on? If there's something TRULY new here, I'll join in. Unless it's the same old Evan-bashing, not really interested.
                            Once again, we aren't talking about 'slow flight' or 'stupid human pilots'. We're talking about windshear at healthy airspeeds and erroneous slat retraction at healthy airspeeds. We are talking about escape maneuvers at full thrust. So you probably can't whinge about me 'bashing pilots' or 'disdaining fundamentals' here, so it probably doesn't interest you.

                            Comment


                            • #15
                              Originally posted by Evan View Post
                              We're talking about windshear at healthy airspeeds and erroneous slat retraction at healthy airspeeds. We are talking about escape maneuvers at full thrust.
                              Call it whatever the phugoid you want. It's an aggressive, measured pull up to harvest all the energy you possibly can and turn it in to altitude.

                              And you avoided the key question of "what's new", so I still conclude that I was right the first time, you are in it to bash the pilots and spew procedures, big words, acronyms, and admonishment.

                              Delta 191 pulled up too little.
                              Colgan and Air France and the guys in Detroit pulled up too much.

                              If I recall this incident, they guys pulled up adequately...amazing how that worked, but not particularly new. I blame the pilots training and experience for the good outcome. You blame luck.
                              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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