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

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  • #16
    Originally posted by Gabriel View Post
    From AvHerald:
    While anything is possible, I believe the #1 video to be genuine. The passenger filming is Sonu Jaiswal. He was on the passenger lists I was able to find and there are several articles mentioning him and the other Indians on the flight. The camera wasn’t through the window at the very end so the bank or the ground rushing up can’t be seen. But you can geolocate with some landmarks seen outside the window and you can make out the position of the plane when the camera comes away a few seconds before the plane falls out of the sky. They are initially headed west (downwind trajectory) and go across the north side of the Bhadrakali Temple. Then they are seen headed south (base) and you can see the Pokhara Football Stadium. You can even make out they are over the northeast area of the old airport before the camera turns away from the window. In fact, you can see the river gorge that they fall into though a bit north of their resting position. The next action would have been the left for final, and is about when they went down.

    https://www.zoomnews.in/en/news-deta...e-crash-1.html
    Attached Files

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    • #17
      Originally posted by xspeedy View Post

      While anything is possible, I believe the #1 video to be genuine. The passenger filming is Sonu Jaiswal. He was on the passenger lists I was able to find and there are several articles mentioning him and the other Indians on the flight. The camera wasn’t through the window at the very end so the bank or the ground rushing up can’t be seen. But you can geolocate with some landmarks seen outside the window and you can make out the position of the plane when the camera comes away a few seconds before the plane falls out of the sky. They are initially headed west (downwind trajectory) and go across the north side of the Bhadrakali Temple. Then they are seen headed south (base) and you can see the Pokhara Football Stadium. You can even make out they are over the northeast area of the old airport before the camera turns away from the window. In fact, you can see the river gorge that they fall into though a bit north of their resting position. The next action would have been the left for final, and is about when they went down.

      https://www.zoomnews.in/en/news-deta...e-crash-1.html
      That is an image of the old Pokhara airport (VNPK). AFAIK, the crash occurred on approach to the new Pokhara International Airport (VNPR). If this image were taken on a heading of around 180deg, an immediate final turn to 120 would be required to align with the new runway 12/30.

      I can't find access to VNPR plates but I would speculate that the visual approach flown here was to overfly the VNPK VOR and then turn steeply 60deg to final. The crash site would indicate that the stall occured at about the moment of this steep turn.

      BTW - Pokhara International just began operations two weeks ago. Could this be a contributing factor?

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      • #18
        Originally posted by Evan View Post

        That is an image of the old Pokhara airport. AFAIK, the crash occurred on approach to the new Pokhara International Airport. If this image were taken on a heading of around 180deg, an immediate final turn to 120 would be required to align with the new runway 12/30.

        BTW - Pokhara International just began operations two weeks ago. Could this be a contributing factor?
        Correct. They were over the old airport for the end of the base leg before a turn onto final for 12 of the newly opened airport. I can’t say that they were on final when they fell. They may have been on the base right before a turn or attempting a turn for final. If you look at the crash position, it is pretty much in line with 12.

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        • #19

          Originally posted by xspeedy View Post

          Correct. They were over the old airport for the end of the base leg before a turn onto final for 12 of the newly opened airport. I can’t say that they were on final when they fell. They may have been on the base right before a turn or attempting a turn for final. If you look at the crash position, it is pretty much in line with 12.
          If true, that's a pretty steep turn for a passenger transport. So it could be an accelerated stall when the a/c was already close to the stall warning regime. Shades of the Lear crash at Teterboro...

          We're probably dealing with pilots entirely unfamiliar with this approach.

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          • #20
            Evan, pilots don't need to be familiar with every approach they fly, especially not visual approaches. Most approaches are flown for the first time in a plane, not in the sim.

            --- 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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            • #21
              Originally posted by xspeedy View Post
              While anything is possible, I believe the #1 video to be genuine.
              I also think it is genuine. I just copied what Simon (AvHerald) said. And it would not be the first time that I fall in the trap of a deep fake. So I simply suspended my opinion.
              It could be, for example, another Yeti ATR approaching the same airport and runway. It could even be the same pax if it is a person that normally commutes between these 2 cities for work.

              I am not saying that I think the above. Just explaining why I just don't feel totally confident of my opinion.

              --- 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


              • #22
                Originally posted by Gabriel View Post
                Evan, pilots don't need to be familiar with every approach they fly, especially not visual approaches. Most approaches are flown for the first time in a plane, not in the sim.
                A factor Gabe, not a primary cause. The same way it might be a factor at Lukla or Paro to an unfamiliar pilot. Again, I don't have eyes on the actual VOR approach for this new airport, but it appears to involve some aggressive maneuvering turning final and throw that on top of fatigue, sloppy airmanship, misconfiguration, mechanical issues or what have you, and you have a smoking hole. If they were already slow and/or at an elevated AoA coming up to the turn, as it appears in the video, but not yet in stall warning, then the turn could prove fatal. What I would call an unforgiving approach and one I would want to rethink going forward.

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                • #23
                  Originally posted by Evan View Post
                  The same way it might be a factor at Lukla or Paro to an unfamiliar pilot.
                  Except that Lukla and Paro are among the few approaches where you do require a special specific training and qualification. While Pokhara is surrounded by terrain, it is in an ample valley and not really high (some 2500 ft). NOTHING similar to Lukla (committed to land, no go around possible after certain point, very short runway, very slopped runway, almost 10K ft high) or Paro (following a narrow valley, involving a quite sharp turn in very short final where you level the wings just before touchdown, 7300 ft high, lots of risks if you have to go around).

                  That said, acknowledged the "factor not primary cause" disclaimer. But a lot of planes, including big ones, turn base to final.

                  --- 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


                  • #24
                    Originally posted by Evan View Post
                    If true, that's a pretty steep turn for a passenger transport. So it could be an accelerated stall when the a/c was already close to the stall warning regime. Shades of the Lear crash at Teterboro...

                    We're probably dealing with pilots entirely unfamiliar with this approach.
                    Where is the evidence of a steep turn? Your detachment from reality (including bike rides) is showing again.

                    The one good video (still posted at AvHerald) looks pretty level until the stall like maneuver.

                    What I want to know is how we have press conferences with dozens of reporters and cameras and officials and questions flying around at Mach 2 and we don't know if the aircraft reported a problem to ATC...guess we'll have to wait for the final report.

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

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                    • #25
                      Originally posted by 3WE View Post
                      Where is the evidence of a steep turn?
                      Find a map of Pokhara. Satellite view. Find the VNPK VOR at the Southeast end of the field. Pin that. Now find VNPR. Draw a line on the extended centerline to that pin. Pretty much a straight line. Now study the passenger video. The heading is right around due south, 180deg. That makes the turn to final RWY 12/30 a 60deg immediate steep turn. Now study the time in that passenger video that elapses after the camera is turned away from the window. Pretty much the runway length, placing that turn just about at the VPNK VOR. A steep 60deg turn to final.

                      All speculation at this point but my speculations are always based on evidence.

                      Originally posted by Gabriel
                      Except that Lukla and Paro...
                      Yes, it is not Lukla or Paro! But what do they all have in common...?

                      Most approaches are flown for the first time in a plane, not in the sim.
                      These are unforgiving visual approaches requiring the pilots to be 100% in the game. Add a factor of error and anything can happen. Pokhara doesn't have the terrain issues but if I am correct about the final turn it does become significantly less forgiving than the most-likely straight-in approach to VNPK that, up until two weeks ago (how many arrivals for this crew?) was SOP.

                      What we see on the phone video is most likely a stall. What causes it? Either exceeding critical angle in (almost) level flight or it's an accelerated stall that occurs in the turn.

                      But a lot of planes, including big ones, turn base to final.
                      Steep turn to final, plus [factor of error and/or failure]

                      Comment


                      • #26
                        Originally posted by Evan View Post
                        What causes a stall?
                        Exceeding the critical angle of attack. And the . is a period.

                        Either exceeding critical angle in (almost) level flight or it's an accelerated stall that occurs in the turn.
                        What? There is no "either". I mean, I think I know what you are trying to say, the plane stalls at different speeds at 1G vs more (or less) Gs, but always at the same AoA. You can be flying straight and level very close to the stall speed and make a turn with a steep bank and not stall. You just need to not pull back. Of course you will not be able to maintain altitude (no matter what: if you don't pull back because you don't pull back, if you pull back because you will stall).

                        Steep turn to final, plus [factor of error and/or failure]
                        Is your speculation that the left turn was commanded first to make the turn to final, and then went out of control? Even if that was the case, the plane apparently went out of control before there was any steep turn. I am saying so because they seem to have already a good crank of right aileron when they had a quite shallow bank of some 15 degrees, which has almost no effect on load factor and stall sped. And yet the plane kept banking left despite the sustained right aileron input.

                        I want to make clear that this is what I think I am seeing in the video after enlarging, but the quality of the enlarged stills is very poor. The video is in 720p and the airplane covers just a small fraction of the frame, so the resolution is terrible.

                        In any case, the FDR was recovered and hopefully was functional (the crash was not hard enough to destroy a black box). SO hopefully we will learn, not soon, but in due time.

                        --- 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


                        • #27

                          Originally posted by Evan View Post

                          Find the VNPK VOR at the Southeast end of the field.
                          Perhaps off-topic and not germane to this accident, as apparently other other flights safely make this approach, but what is the effect of tall trees so close to a navaid facility? In particular, the stand of trees 75' to the north-west, and a tree to the northeast that is over-growing the roof of the facility.

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                          • #28
                            Originally posted by Gabriel View Post
                            You can be flying straight and level very close to the stall speed and make a turn with a steep bank and not stall. You just need to not pull back. Of course you will not be able to maintain altitude.
                            Oh, you’re doing it to me again… Why would an experienced pilot not pull back in a turn to final at very low altitude?


                            Is your speculation that the left turn was commanded first to make the turn to final, and then went out of control?
                            Perhaps, but combined with some unknown error or failure. It appears that the pitch is high before the turn, so perhaps they were too slow, near stall already. This is an ATR-72. Even at Vref+0 the manual restricts max bank angle to 30deg (and I think 5deg at VSR). If you are correct about the rudder deflection, perhaps the left engine was out. Etc etc.

                            What is the critical difference between a stall in level flight and an accelerated stall in a sudden steep turn?

                            No warning.

                            Comment


                            • #29
                              Originally posted by Evan View Post
                              That makes the turn to final RWY 12/30 a 60deg immediate steep turn.
                              Again, THE outside video of THE PLANE STALLING does NOT SHOW a steep bank.

                              The video from INSIDE the (WRONG) plane does NOT SHOW a steep bank…it shows a bunch of floorboard.

                              And where in the hell did you get a 60 degree bank? Why not 50? 70? 63.5493?

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

                              Comment


                              • #30
                                Originally posted by Evan View Post

                                What is the critical difference between a stall in level flight and an accelerated stall in a sudden steep turn?

                                No warning.
                                I believe the official warning systems function exactly the same.
                                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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