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Air Niugini plane misses runway, lands in sea off Micronesia island

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  • #46
    Originally posted by Gabriel View Post
    My question since the beginning was just why having 3 whites is listed among the reasons. It is not. I do agree with the other reasons listed and then some.
    Perhaps they are referring to the combination of being off glideslope while seeing potentiai IMC ahead. But what troubles me more is that the report fails to cite the immense violation of handing over instrument monitoring entirely from the PF to the PM, something that clearly happened here and was a major cause of the accident.

    2 red - 2 white means you are at most within 15' (=0.25 degrees) of the nominal glide slope. If you see at least 1 of each color you are at most within 35' (=0.58 degrees) of the glide slope.
    Note that anything else than 15' gives you 3 lights of 1 color, meaning that you can see 3 white if you are barely more than 1/4 of a degree above the nominal glide slope.

    HENCE the word precision.
    This is probably true of the 737 and most conventional aircraft, but, for the sake of accuracy, it isn't a universal truth. Unlike ILS, which receives signals from optimally-placed antennas and uses software to interpret these into a precise cockpit display of position, PAPI works via a direct relationship between the light source and the pilot's eyes. Thus, the accuracy varies significantly depending upon the position of the pilot relative to the longitudinal centerline of the aircraft and also the deck angle during the approach. This is why PAPI is not accurate on aircraft like the 747 with high cockpits placed further aft or with aircraft like Concorde that require a steeper pitch angle on approach. I see the value of PAPI where ILS isn't available (or at least the GS portion isn't), but why rely on it when you have a more precise indication on the PFD?

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    • #47
      Originally posted by Evan View Post
      but why rely on it when you have a more precise indication on the PFD?
      Who's relying on it?

      My guess is that PAPI's are used two ways: 1) Kind of helpful when the ILS is out and you don't have something computer-generated. 2) A way to allow you to look out the window a bit more while you double-confirm with instruments that you are on the glidepath.
      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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      • #48
        Originally posted by 3WE View Post
        Who's relying on it?

        My guess is that PAPI's are used two ways: 1) Kind of helpful when the ILS is out and you don't have something computer-generated. 2) A way to allow you to look out the window a bit more while you double-confirm with instruments that you are on the glidepath.
        Indeed, but in this case the ILS glideslope signal was available and quickly went from a half dot high to beyond two dots low. A quick peek at the PFD would have told them that they were far below the glideslope when there was still time to go around.

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        • #49
          Originally posted by Evan View Post
          Indeed, but in this case the ILS glideslope signal was available and quickly went from a half dot high to beyond two dots low [deliberate deletion] A quick peek at the PFD would have told them that they were far below the glideslope when there was still time to go around.
          As Gabieeee explained, a quick peek at the PAPI would also tell them they were below the glideslope when there was still time to go around.

          As Gabieeee also explained, a quick peek at the VSI, a quick peek at the altimeter, a quick listen to bitching Bob/Betty should also have provided some good information to suggest a go-around.

          As Gabieeee theorized, some misleading view out the window might have "told" the PF that things were fine...conversely, the PNF should have been seeing that things were not fine and used basic CRM to 'order' a go around...unless they were enjoying the view out the front window too much, themselves.
          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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          • #50
            Originally posted by 3WE View Post
            As Gabieeee explained, a quick peek at the PAPI would also tell them they were below the glideslope when there was still time to go around.

            As Gabieeee also explained, a quick peek at the VSI, a quick peek at the altimeter, a quick listen to bitching Bob/Betty should also have provided some good information to suggest a go-around.
            Not if the PAPI has suddenly disappeared into a rainy white void, as I think the case was here. Before disappearing, the PAPI told them they was a bit high (imprecisely). After the PAPI disappeared the PIC seems to have overestimated the correction, with nothing to gauge it by.
            Except, um... instruments. He seems to have assigned the instruments part entirely to his FO, who seems to have temporarily lost his voice. He seems to have been 100% focused on the task of regaining visual contact with the runway.

            If he was adamant about continuing (and thus a gambling man, gambling with the lives of others), I would have as least expected him to assign the visual contact part to his FO and concentrated himself at least partially on the instruments, not vice versa.

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            • #51
              Originally posted by 3WE View Post
              As Gabieeee explained, a quick peek at the PAPI would also tell them they were below the glideslope when there was still time to go around.

              As Gabieeee also explained, a quick peek at the VSI, a quick peek at the altimeter, a quick listen to bitching Bob/Betty should also have provided some good information to suggest a go-around.
              Not if the PAPI has suddenly disappeared into a rainy white void, as I think the case was here. Before disappearing, the PAPI told them they were a bit high (imprecisely). After the PAPI disappeared the PIC seems to have overestimated the correction, with nothing to gauge it by.

              Except, um... instruments. He seems to have assigned the instruments part entirely to his FO, who seems to have temporarily lost his voice. The PIC seems to have been 100% focused on the task of regaining visual contact with the runway.

              If he was adamant about continuing (and thus a gambling man, gambling with the lives of others), I would have at least expected him to assign the visual contact part to his FO and, as PF, concentrated himself at least partially on the instruments, not vice versa.

              Comment


              • #52
                Originally posted by Evan View Post
                Not if the PAPI has suddenly disappeared into a rainy white void, as I think the case was here. Before disappearing, the PAPI told them they were a bit high (very precisely). After the PAPI disappeared the PIC seems to have overestimated the correction, with nothing to gauge it by...
                1. Fixed.

                Originally posted by Evan View Post
                ...Except, um... instruments. He seems to have assigned the instruments part entirely to his FO, who seems to have temporarily lost his voice. The PIC seems to have been 100% focused on the task of regaining visual contact with the runway.

                If he was adamant about continuing (and thus a gambling man, gambling with the lives of others), I would have at least expected him to assign the visual contact part to his FO and, as PF, concentrated himself at least partially on the instruments, not vice versa.
                2. Indeed. It appears that bad CRM may be a significant issue here. Ideally someone's MOSTLY working the window, but frequently peeking at instruments, with someone else MOSTLY watching the instruments with a frequent peek out the window.
                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                Comment


                • #53
                  Originally posted by Evan View Post
                  He seems to have assigned the instruments part entirely to his FO
                  And yet the "report" seems curiously uninterested, even dismissive, of this decision. Even though it would appear to be a causal factor of the accident. Is it not the first rule of a monitored approach in IMC that the PF flies the plane based on the primary instruments?

                  Originally posted by Evan View Post
                  If he was adamant about continuing (and thus a gambling man, gambling with the lives of others), I would have as least expected him to assign the visual contact part to his FO and concentrated himself at least partially on the instruments, not vice versa.
                  Indeed.

                  Comment


                  • #54
                    Originally posted by Evan View Post
                    I see the value of PAPI where ILS isn't available (or at least the GS portion isn't), but why rely on it when you have a more precise indication on the PFD?
                    Do you propose that the pilot stays focused on the ILS (which by the way becomes unusable too sensitive close to touchdown) until the 50 ft call on the numbers and then transition in a split second to the visual flight for the last 5 seconds of the flare and landing? Unless you are executing an autoland, the last part of the approach and the landing are ALWAYS visual. Yes, the PF still has to monitor the instruments but the view out of the windscreen is the main focus for lateral and vertical flight path management.

                    --- 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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                    • #55
                      Originally posted by Evan View Post
                      Not if the PAPI has suddenly disappeared into a rainy white void, as I think the case was here. Before disappearing, the PAPI told them they was a bit high (imprecisely).
                      Can you stop playing with words and define what you mean with precision, accuracy and on-slope?

                      --- 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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                      • #56
                        Originally posted by Evan View Post
                        He seems to have assigned the instruments part entirely to his FO.
                        Right, because "monitor the airspeed" means "I am assigning the whole instruments part to you".
                        The fact that he stopped monitoring the instruments (or that he did keep monitoring them but disregarding the indication because he was either confused or, as you hypothesized, had other plans in mind) doesn't mean that he assigned that task to the FO.

                        --- 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


                        • #57
                          Originally posted by Gabriel View Post
                          Do you propose that the pilot stays focused on the ILS (which by the way becomes unusable too sensitive close to touchdown) until the 50 ft call on the numbers and then transition in a split second to the visual flight for the last 5 seconds of the flare and landing? Unless you are executing an autoland, the last part of the approach and the landing are ALWAYS visual. Yes, the PF still has to monitor the instruments but the view out of the windscreen is the main focus for lateral and vertical flight path management.
                          Are we talking about visual conditions or are we talking about what happened here? They lost visual contact (obviously). Again, if you are adamantly going to land anyway (because you are a 20K hour genius airman who is above the rules of caution), unike PAPI, the ILS still works in IMC. There's this thing called 'autoland'...

                          Can you stop playing with words and define what you mean with precision, accuracy and on-slope?
                          ILS gives you an accurate scale with a moving icon that allows you to see how far and at what rate you are deviating and how far need to correct your path. PAPI doesn't. But that's ok because PAPI is for visual conditions, so it is a less precise aid for that purpose. But if you see that you are high on the PAPI, and then you lose visual contact, you have no precise reference other than ILS to correct your path. You, might, for example, overcompensate, quickly dropping well below the glideslope at a high sink rate and settle for a survivable splashdown (mostly survivable). But I'm against that.

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                          • #58
                            Originally posted by Gabriel View Post
                            Right, because "monitor the airspeed" means "I am assigning the whole instruments part to you".
                            The fact that he stopped monitoring the instruments (or that he did keep monitoring them but disregarding the indication because he was either confused or, as you hypothesized, had other plans in mind) doesn't mean that he assigned that task to the FO.
                            He flew a 737NG into the water. How do you do that with an eye on the PFD?

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                            • #59
                              Originally posted by Evan View Post
                              Are we talking about visual conditions or are we talking about what happened here? They lost visual contact (obviously). Again, if you are adamantly going to land anyway (because you are a 20K hour genius airman who is above the rules of caution), unike PAPI, the ILS still works in IMC. There's this thing called 'autoland'...
                              Sorry, I thought that you had stopped talking about the specific conditions of this case when you started to talk about the Concorde and they 747.
                              But even then, staying in this case and your description of the possible gambling scenario, I still don't get what the 3 whites have to do with their decision (or lack thereof) to go around.

                              --- 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


                              • #60
                                Originally posted by Evan View Post
                                ILS gives you an accurate scale with a moving icon that allows you to see how far and at what rate you are deviating and how far need to correct your path. PAPI doesn't. But that's ok because PAPI is for visual conditions, so it is a less precise aid for that purpose. But if you see that you are high on the PAPI, and then you lose visual contact, you have no precise reference other than ILS to correct your path. You, might, for example, overcompensate, quickly dropping well below the glideslope at a high sink rate and settle for a survivable splashdown (mostly survivable). But I'm against that.
                                The problem is not really the precision, accuracy, bias, offset. error, uncertainty, repeatability, reproducibility or how many measurement categories the digital PAPI has compared with the analog indication of the ILS.

                                If you are following the PAPI and lose it and do nothing about that, you will get more or less the same outcome than in you are following the ILS and lose it and do nothing about that.

                                --- 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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