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

  1. #41
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    I see a lot of reasons to execute a missed approach at that point and any point thereafter. I just don't see 3 whites being one of them. 3 whites means that you are a little bit high, equivalent to more or less half dot in the glide slope, and is not a criteria to cal the approach not-stabilized. Also, think that the PAPI is not an analogical indication, it is digital. There is nothing between 2 whites (on slope) and 3 whites (a bit high). When flying 2 whites - 2 red, you don't know how close you are from 3 whites or 3 reds until you see them, so the minor correction (allowed and expected in the stabilized approach criteria) is expected to begin only AFTER seeing the 2 whites.
    So the report considers anything but two whites and two reds at the MAP to be a go-around but you don't. I don't know what the stabilized criteria is with regard to PAPI, but I like the idea of being STABILIZED at that point.

  2. #42
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    So the report considers anything but two whites and two reds at the MAP to be a go-around but you don't. I don't know what the stabilized criteria is with regard to PAPI, but I like the idea of being STABILIZED at that point.
    I am telling you what it is and what it is not. You don't need to believe me though. You used to be good at googling stuff.

    Here you have 1 example:

    An approach is stabilised when all of the following criteria are met:

    1. The aircraft is on the correct flight path
    2. Only small changes in heading/pitch are necessary to maintain the correct flight path
    3. The airspeed is not more than VREF + 20kts indicated speed and not less than VREF
    4. The aircraft is in the correct landing configuration
    5. Sink rate is no greater than 1000 feet/minute; if an approach requires a sink rate greater than 1000 feet/minute a special briefing should be conducted
    6. Power setting is appropriate for the aircraft configuration and is not below the minimum power for the approach as defined by the operating manual
    7. All briefings and checklists have been conducted
    8. Specific types of approach are stabilized if they also fulfil the following:
      1. ILS approaches must be flown within one dot of the glide-slope and localizer
      2. a Category II or III approach must be flown within the expanded localizer band
      3. during a circling approach wings should be level on final when the aircraft reaches 300 feet above airport elevation; and,
      4. Unique approach conditions or abnormal conditions requiring a deviation from the above elements of a stabilized approach require a special briefing.

    An approach that becomes unstabilised below 1000 feet above airport elevation in IMC or 500 feet above airport elevation in VMC requires an immediate go-around.
    https://www.skybrary.aero/index.php/Stabilised_Approach

    If 3 red or 3 white at any point below 1000 or 500 ft was a criteria to call an approach not-stabilized, then about every approach would be required to be called not-stabilized, a go-around would need to be initiated, and the landing would only occur when the pilot declares fuel emergency and uses his PIC prerogative power to deviate from any regulation if he deems doing so is needed for safety reasons.

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  3. #43
    Senior Member Evan's Avatar
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    Quote Originally Posted by Gabriel View Post
    I am telling you what it is and what it is not. You don't need to believe me though. You used to be good at googling stuff.
    Used to be...?

    I think the thing to understand here is that the first P in PAPI is a bit fatuous. "Precision" is not exactly what you are getting here. I don't know precisely how much deviation you are getting from three whites, but If you ask BoeingBobby, he might tell you three whites on the 74 is on glideslope and two reds and two whites is a bit low and three reds is seriously low. What those lights are telling you is actually a type-specific thing. But it's a moot issue here because the crash is the result of the instability of the approach from that point onward, and the loss of visual contact. I'm not arguing with you on the definition of 'stable' and of course I understand the thing is not on rails and some minor deviation must be tolerated. But I think it is reasonable for the report to point out that, high on the PAPI and looking at potential IMC ahead in the windscreen, there is little excuse for continuing.

  4. #44
    Senior Member Gabriel's Avatar
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    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.

    BUT, more important than that, there is no pink light and no 2.5 whites. You go from 2 and 2 to 3 and 1. 3 and 1 is the FIRST indication that you get that you are not PERFECTLY on-slope.

    Again, I agree that a go-around should have been initiated for more than one reason, reasons that range from common sense to classic airmanship to mandatory procedures and requirements.

    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.

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  5. #45
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Gabriel View Post
    ***My question since the beginning was just why having 3 whites is listed among the reasons.***
    -It is linked to a cool, insider acronym.
    -It is linked to a specific, black and white (excuse me, red and white) procedure (as opposed to the broad fundamental concept that your altitude management has gone to hell (below minimums) with 10+ indications that would work in numbers from 150 to 1011 and most points in-between.)

    Concur that there's a few other things that should have caught folks attention first and that some sort of improper DUAL fixation on a visual illusion seems like a good guess as to the root cause.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  6. #46
    Senior Member Evan's Avatar
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    Quote 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?

  7. #47
    Senior Member 3WE's Avatar
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    Quote 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.

  8. #48
    Senior Member Evan's Avatar
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    Quote 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.

  9. #49
    Senior Member 3WE's Avatar
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    Quote 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.

  10. #50
    Senior Member Evan's Avatar
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    Quote 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.

  11. #51
    Senior Member Evan's Avatar
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    Quote 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.

  12. #52
    Senior Member 3WE's Avatar
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    Quote 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.

    Quote 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.

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    Quote 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?

    Quote 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.

  14. #54
    Senior Member Gabriel's Avatar
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    Quote 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.

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    Senior Member Gabriel's Avatar
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    Quote 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?

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    Senior Member Gabriel's Avatar
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    Quote 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.

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  17. #57
    Senior Member Evan's Avatar
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    Quote 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.

  18. #58
    Senior Member Evan's Avatar
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    Quote 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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    Senior Member Gabriel's Avatar
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    Quote 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.

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  20. #60
    Senior Member Gabriel's Avatar
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    Quote 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.

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