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ATR-72 crash at PKR, Nepal. Many fatalities feared.

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  • #46
    Something to think about/rampant speculation: There were reports of strange altitude data on this flight ==> Something significantly wrong with the pitot/static system? ==> A speed readout telling the pilots were faster (and higher?) than they were?

    Evan, Thanks for rounding the corners, but they WEREN’T in a steep bank when the stall occurred.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    • #47
      Originally posted by 3WE View Post
      Something to think about/rampant speculation: There were reports of strange altitude data on this flight
      Source?

      Evan, Thanks for rounding the corners, but they WEREN’T in a steep bank when the stall occurred.
      Concur, but the possibility still exists that a moderate increase in bank just below stall warning may have triggered an accelerated stall.

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      • #48
        Another mystery to focus on is: why the runway change? I still haven't seen any winds data except for reports that they were negligable. If it wasn't a tailwind issue, then what?

        One theory I have is that the instructor pilot wanted to see the F/O fly the visual circle-to-land before granting her the PIC rating. The CVR would reveal that.

        And then there's the mystery of the pitch-up just before the stall. A go-around? A Renslow maneuver at stall warning? An altitude or speed adjustment prior to stall warning? Or just a coordinative error?

        One clue is that there is no evidence of a power increase in the ground or cabin video audio. That would be the first (correct) reaction to a critical altitude stall warning on the ATR.

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        • #49
          ATRs will ATR. Or Pilots will pilot.


          --- 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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          • #50
            Pitot-Static?

            Originally posted by Evan View Post
            Source?
            Comments at AvHerald about altitude data enroute. (Which have been explained as a transponder issue, not_pitot-static.)

            It’s a stretch and requires additional Swiss holes: Pilot not_monitoring, maintenance splicing a hose? Stuff slightly more likely than meteors. Very unlikely, but so are plane crashes. Wanton speculation based on the question “was ANYTHING unusual observed before the crash”.

            By the way, Gabriel thinks the pilots pulled up a little (as shown in the video) to go around. Do you know that, in itself, could cause an accelerated stall…and the cabin video shows a bit of turbulence…another potential g-loading to increase AOA.
            Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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            • #51
              Originally posted by Gabriel View Post
              ATRs will ATR. Or Pilots will pilot.

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


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

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              • #52
                And ice will ice. Except there was no ice in the Nepal crash.

                --- 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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                • #53
                  Originally posted by Gabriel View Post

                  And ice will ice. Except there was no ice in the Nepal crash.
                  Similarities, nonetheless- ATRs seem to bite.

                  Another similarity: that fuselage and lower tail section area is sadly resilient…low level, or flight levels, it seems to survive.
                  Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                  • #54
                    Originally posted by 3WE View Post
                    Similarities, nonetheless- ATRs seem to bite.
                    The ATR-72 has a higher wing loading than comparable t-props, with the exception of the Q400. Not so forgiving to steep turns and pull-ups.

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                    • #55
                      Originally posted by Evan View Post
                      The ATR-72 has a higher wing loading than comparable t-props, with the exception of the Q400. Not so forgiving to steep turns and pull-ups.
                      Here we go again.
                      Can you please explain what you mean, exactly? How is it any less forgiving than, I don't know, let's say the Piper Tomahawk like the one in my avatar which has a much lower wing loading?

                      --- 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


                      • #56
                        Originally posted by Gabriel View Post

                        Here we go again.
                        Can you please explain what you mean, exactly? How is it any less forgiving then, I don't know, let's say the Piper Tomahawk like the one in my avatar which has a much lower wing loading?
                        Interesting turn in the conversation.

                        Its is probably easier (and takes less altitude) to RECOVER in a Tomahawk, and the big turboprops do seem a bit nasty…conversely, 172s and A-300s seem somewhat spin resistant.

                        And, I would hate to be riding a Jetstream, Brasilia or Saab or Tomahawk or A-300 or 777 that was stalled at the exact place the ATR stalled in Nepal or China.

                        On the other spectrum, a 172 deliberate, coordinated accelerated stall pops out of the turn to roughly straight and level FDnH flight, and 150 aerobat snap rolls are slow motion beauty.

                        And we’ve stalled plenty of 172s out of base-to-final turns.

                        I’d certainly expect wing loading to affect handling, but it’s ummm, not black and white.
                        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                        Comment


                        • #57
                          Originally posted by Gabriel View Post

                          Here we go again.
                          Can you please explain what you mean, exactly? How is it any less forgiving than, I don't know, let's say the Piper Tomahawk like the one in my avatar which has a much lower wing loading?
                          Just that higher wing loading results in elevated stall speed and diminished sustained turn performance at low speeds. I think this is a factor in a circle-to-land approach, especially where the bank angle might require steeper adjustment.

                          Remember, factor, not cause. A higher wing loading is less forgiving to low speeds and that threshold of error is amplified by bank angle or any maneuver that increases G force.

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                          • #58
                            What I mean is that, when dropping below a given airspeed, a higher wing loading will stall earlier.

                            Here is my current speculation:

                            Probable cause: The failure of the crew to monitor airspeed and maintain a safe margin above stall for maneuvering.

                            Contributing factor: The unfamiliarity with both pilots to a non-precision visual approach in manual flight.

                            The scenario: The decision to fly the circle-to-land comes late and is not briefed. While flying the approach for the first time, both pilots are focused (tunneling) on landmarks and navigation. The power is set (no autothrottle) to sustain a low approach speed while maintaining low level flight but airspeed is not constantly monitored. The turn to final is initiated too close to the landmark (Bhadrakali Temple, atop a hill). The light sustained bank degrades airspeed while the pilots focus on vertical and lateral navigation, maintaining altitude while losing maneuvering margin in speed. While crossing the old runway adjacent to the VPNK VOR, the instructor pilot realizes that the arc of the turn will miss the new runway alignment. One of two things occur:

                            A) The instructor pilot calls for go around while the a/c is just above stall warning threshold at elevated AoA. The PF makes an overly aggressive and sustained pitch input that causes an asymmetric stall which is unrecoverable at low altitude.

                            or

                            B) The instructor pilot tells the PF to increase the turn radius to save the approach while the a/c is just above stall warning threshold at elevated AoA. The additional wing loading causes the plane to enter an accelerated stall which is unrecoverable at low altitude.

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                            • #59
                              Originally posted by Evan View Post
                              What I mean is that, when dropping below a given airspeed, a higher wing loading will stall earlier.
                              There is a huge problem with what you are saying. I don't have time now for one of my long rants about aerodynamics. Suffice to say that Vref is required to have a margin above 1G stall warning speed (not just 1G stall speed), that that margin is % of knots, and that the bigger the number of knots for the stall warning the bigger the number of knots in the % margin.

                              Of course, when you say "given airspeed", if you try to fly an ATR and a Piper Cub at 60 knots, it is not the same. Nor is flying a fully loaded ATR or an almost empty ATR at 90 knots. But what's the significance of that? Pilots don't fly the same fixed speed regardless of the airplane type or weight.

                              --- 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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                              • #60
                                Originally posted by 3WE View Post

                                Interesting turn in the conversation.

                                Its is probably easier (and takes less altitude) to RECOVER in a Tomahawk, and the big turboprops do seem a bit nasty…conversely, 172s and A-300s seem somewhat spin resistant.

                                And, I would hate to be riding a Jetstream, Brasilia or Saab or Tomahawk or A-300 or 777 that was stalled at the exact place the ATR stalled in Nepal or China.

                                On the other spectrum, a 172 deliberate, coordinated accelerated stall pops out of the turn to roughly straight and level FDnH flight, and 150 aerobat snap rolls are slow motion beauty.

                                And we’ve stalled plenty of 172s out of base-to-final turns.

                                I’d certainly expect wing loading to affect handling, but it’s ummm, not black and white.
                                Plenty of Cessnas 172 (or similar) have lost lateral control installs. And the reasons why some planes are better at keeping the wings level in a full stall have nothing to do with wing loading. But almost any plane (including the Cessna 150 or the Piper Cub, or the P51) will react the opposite to your intention if you try to correct a wing drop in a stall with opposite aileron.

                                --- 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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