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Flydubai Flight 981 Crashes on Landing in Rostov-on-Don, Russia

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  • Originally posted by Evan View Post
    Is that directed at me or at every Boeing engineer and NTSB crash investigator who has never logged an hour of stick time yet understands human factors better than most pilots?

    Quality pilots will admit this and respect procedure. Those are the ones that don't fly into the ground.

    i doubt boeing's "engineers" are writing procedures based on their vast experience in human factors, and as for NTSB "crash investigators," it sure is easy to armchair the whole shebang AFTER the crash and declare who did what wrong. they too are not writing procedures, though their findings may lead to how and what procedures are written.

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    • Originally posted by Evan View Post
      Is that directed at me or at every Boeing engineer and NTSB crash investigator who has never logged an hour of stick time yet understands human factors better than most pilots?

      Quality pilots will admit this and respect procedure. Those are the ones that don't fly into the ground.
      Yes Evan, when I wrote the word "you", I wasn't meaning you. I was meaning every Boeing Engineer and every NTSB crash investigator. You are perceptive. Just like I agreed with LS-D744 that it's proper to totally ignore procedure and not push the nose over ever at all since the ground is so close. Instead it's better to hit aircraft with which you have a traffic conflict and go ahead and stall the plane.

      Indeed, quality pilots respect procedure. As do most forum parlour talkers. It's just that quality pilots also respect fundamentals. Most forum parlour talkers also respect fundamentals, except for some who can't control themselves and have to react at the suggestion that it might be a good idea to be careful about aggressive nose-overs at low altitudes.
      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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      • Originally posted by 3WE View Post
        ...it might be a good idea to be careful about aggressive nose-overs at low altitudes.
        You see, you are still not getting the essence of human factors. We don't know yet what happened here but 3WE, I'm going to go out on a limb and say that the pilots here knew that pointing the nose at the ground at low altitude was a bad idea. What you can't seem to grasp is that they might have thought pointing the nose down from a steep climb was a good idea, and that they might have thought the nose was going up when it was going down. Do I have to explain this to you again? Fatigue, frustration, skipped procedure, underslung thrust, motor skill errors, abrupt changes in attitude and G-force, IMC, the human vestibular sensory system... that's an equation for lost situational awareness. These guys just abandoned an approach; do you really think they intended to enter a dive?

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        • Originally posted by Evan View Post
          You see, you are still not getting the essence of human factors. We don't know yet what happened here but 3WE, I'm going to go out on a limb and say that the pilots here knew that pointing the nose at the ground at low altitude was a bad idea. What you can't seem to grasp is that they might have thought pointing the nose down from a steep climb was a good idea, and that they might have thought the nose was going up when it was going down. Do I have to explain this to you again? Fatigue, frustration, skipped procedure, underslung thrust, motor skill errors, abrupt changes in attitude and G-force, IMC, the human vestibular sensory system... that's an equation for lost situational awareness. These guys just abandoned an approach; do you really think they intended to enter a dive?
          Evan, while I agree what you said above in principle, I don't think that your scenario fully fits there.

          The change in attitude was of say 75 degrees. That is way too much in any direction. Even if the pilots thought that they were way too nose up, I will go out on a limb and say that they didn't think that they were 75 degrees nose up. Also, I understand the inversion issue, but I don't think that that is compatible with -1G. That is something that the vestibular sensory system cannot miss, or it is irrelevant, because you will feel it in all your bodies. It is the feeling of being hanging upside down. You can't miss -1G (now, you can think that you are not accelerated, at 1G inverted, or accelerated to -1G, that's a different story).

          I don't thin that the -75deg, -1G pitch was an intentional response to the attitude that they judged wrongly due to disorientation (in other words, that they reacted correctly, or even intentionally to a wrong situation). For me the -75deg, -1G was not intended. Disorientation may have been part of this, but I think (almost hope) that there is more to it that an intentional response to it, something like a runaway trim or a pilot unkowingly holding the thumb on the trim button.

          --- 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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          • Originally posted by Gabriel View Post
            Evan, while I agree what you said above in principle, I don't think that your scenario fully fits there.

            The change in attitude was of say 75 degrees. That is way too much in any direction. Even if the pilots thought that they were way too nose up, I will go out on a limb and say that they didn't think that they were 75 degrees nose up. Also, I understand the inversion issue, but I don't think that that is compatible with -1G. That is something that the vestibular sensory system cannot miss, or it is irrelevant, because you will feel it in all your bodies. It is the feeling of being hanging upside down. You can't miss -1G (now, you can think that you are not accelerated, at 1G inverted, or accelerated to -1G, that's a different story).

            I don't thin that the -75deg, -1G pitch was an intentional response to the attitude that they judged wrongly due to disorientation (in other words, that they reacted correctly, or even intentionally to a wrong situation). For me the -75deg, -1G was not intended. Disorientation may have been part of this, but I think (almost hope) that there is more to it that an intentional response to it, something like a runaway trim or a pilot unkowingly holding the thumb on the trim button.
            I also suspect runaway trim might be involved (hell of a time for it, and on a fairly new airplane). As usual we've got multiple arguments going here and I am trying to point out the human factor in general, which seems to be too easily dismissed with all this talk about 'rules-of-thumb' and 'flying-the-plane'. But I'm not convinced that this was pure somatogravic-induced error.

            But on that point, the negative G-forces you speak of can actually bring on and perpetuate the sense of pitching up:
            Originally posted by Wikipedia
            Inversion illusion

            An abrupt change from climb to straight-and-level flight can stimulate the otolith organs enough to create the illusion of tumbling backwards, or inversion illusion. The disoriented pilot may push the aircraft abruptly into a nose-low attitude, possibly intensifying this illusion.
            According to the English translation of the latest report, the yoke was pushed into a nose-down position. That doesn't really match a runaway trim scenario, where you would expect the PF to fight the trim (unless the yoke forces that pulled it there were too strong to overcome)...

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            • I think that the Wikipedia quote is talking more about an angular illusion (pitch) than an acceleration one (Gs). I don't think that -1G can be confused with positive Gs.

              By the way, can you please give the link or name of the article?

              --- 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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              • Originally posted by Gabriel View Post
                I think that the Wikipedia quote is talking more about an angular illusion (pitch) than an acceleration one (Gs). I don't think that -1G can be confused with positive Gs.

                By the way, can you please give the link or name of the article?
                Somatogravic illusion is a pitching illusion caused by the gravitational effects of acceleration combining with the earth's gravitational field to mislead the vestibular system's perception of spatial orientation. In this case it is an illusion of upward pitch brought on by acceleration forces. A sudden level-off can also create this illusion. The illusion can be sustained as long as the aircraft continues to accelerate (as in a nose down dive).

                And, as I keep pointing out here, there is plenty of precedent for this. This shouldn't come as news to any airline pilot. A number of plane crashes and upsets have been attributed to this human factor.

                One example, Afriqiyah Airways Flight 771, included a study of the phenomena by the investigation. I suggest you read Appendix 6, Study of Spatial Disorientation found in part 4 of the final report (page 9 on the pdf): http://www.caa.ly/finalReport/FINAL_5A-ONG-4.pdf

                I'm posting here both a quote from that report and a plot that approximates the pilot's perceived pitch against the actual pitch during that accident sequence. Also note how the sequence itself resembles the FlyDubai flight path.

                The Wikipedia link is here. But there is a lot more on the subject, including a Skybrary page.
                Attached Files

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                • Based on the FlyDubai videos which I know aren't the most scientific source, it seems to me there's a significant difference between this accident and the one you cite.

                  In the graph you posted, after the go-around is initiated the aircraft pitches upward as you'd expect, to a max. nose-up angle of about 11 degrees. The pitch then decreases apparently due to the pilot (going totally against his training) reacting to his sense of balance. But the decrease is fairly gradual and only goes to about 8 degrees nose-down before (seemingly) the pilot realizing something is wrong and pulling up (note the pitch trend reverses right at the end of the graph).

                  From the videos, in the FlyDubai case it appears the nose-down pitch was much greater... I'd estimate around an order of magnitude greater. While I don't have numbers to back this up, I'd suspect the rate of pitch change in the Afriqiyah Airways accident was enough to cause only a small change in vertical G force. But the rate in the FlyDubai one might well have been enough to cause the pilots/pax to experience negative G's, and that's a condition that will quickly get *everyone's* attention!
                  Be alert! America needs more lerts.

                  Eric Law

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                  • Originally posted by elaw View Post
                    Based on the FlyDubai videos which I know aren't the most scientific source, it seems to me there's a significant difference between this accident and the one you cite.

                    In the graph you posted, after the go-around is initiated the aircraft pitches upward as you'd expect, to a max. nose-up angle of about 11 degrees. The pitch then decreases apparently due to the pilot (going totally against his training) reacting to his sense of balance. But the decrease is fairly gradual and only goes to about 8 degrees nose-down before (seemingly) the pilot realizing something is wrong and pulling up (note the pitch trend reverses right at the end of the graph).

                    From the videos, in the FlyDubai case it appears the nose-down pitch was much greater... I'd estimate around an order of magnitude greater. While I don't have numbers to back this up, I'd suspect the rate of pitch change in the Afriqiyah Airways accident was enough to cause only a small change in vertical G force. But the rate in the FlyDubai one might well have been enough to cause the pilots/pax to experience negative G's, and that's a condition that will quickly get *everyone's* attention!
                    Yes, the Afriqiyah Airways accident was not as extreme, but the phenomena is what I am trying to convey. Both pilots realized something was wrong because the ground suddenly filled the windows, two seconds prior to impact. Tatarstan Airlines Flight 363 was much more extreme, if you need a more similar case. In that case, the pitch went from +25 to -75 over a period of 45 seconds and the crew still flew it into the ground. How many negative G's is that?

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                    • Originally posted by Evan View Post
                      Yes, the Afriqiyah Airways accident was not as extreme, but the phenomena is what I am trying to convey. Both pilots realized something was wrong because the ground suddenly filled the windows, two seconds prior to impact. Tatarstan Airlines Flight 363 was much more extreme, if you need a more similar case. In that case, the pitch went from +25 to -75 over a period of 45 seconds and the crew still flew it into the ground. How many negative G's is that?
                      Point taken!

                      Although... +25 to -75 over a period of 45 seconds, that's about -2 degrees per second - I suspect that's not enough to induce negative G at all.

                      I found a study analyzing passenger comfort during various terminal-area maneuvers (http://ntrs.nasa.gov/archive/nasa/ca...9760008693.pdf) where most responded "neutral" on a scale from "very comfortable" to "very uncomfortable" (page 125) for a 2-degree-per-second pitchover maneuver. I suspect the rating would have been considerably lower had the pax experienced negative G's.
                      Be alert! America needs more lerts.

                      Eric Law

                      Comment


                      • Originally posted by elaw View Post
                        Point taken!

                        Although... +25 to -75 over a period of 45 seconds, that's about -2 degrees per second - I suspect that's not enough to induce negative G at all.

                        I found a study analyzing passenger comfort during various terminal-area maneuvers (http://ntrs.nasa.gov/archive/nasa/ca...9760008693.pdf) where most responded "neutral" on a scale from "very comfortable" to "very uncomfortable" (page 125) for a 2-degree-per-second pitchover maneuver. I suspect the rating would have been considerably lower had the pax experienced negative G's.
                        No, the entire event, from initiation of go-around to game over, took 45 seconds. The actual pitch manuever was quite abrupt.

                        I think you're missing the essence of this though. It's not a stealth thing in which it goes unnoticed. It is quite noticeable, of course. The issue is the perceived orientation vs the actual one. Both pilots and pax are going to sense something discomforting, but they may sense it to be the opposite of what is actually happening

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                        • Originally posted by elaw View Post
                          From the videos, in the FlyDubai case it appears the nose-down pitch was much greater... I'd estimate around an order of magnitude greater. While I don't have numbers to back this up, I'd suspect the rate of pitch change in the Afriqiyah Airways accident was enough to cause only a small change in vertical G force. But the rate in the FlyDubai one might well have been enough to cause the pilots/pax to experience negative G's, and that's a condition that will quickly get *everyone's* attention!
                          We have more info than that. We know the FlyDubi first pitched up for the go-around. We don't know how much, but a typical go-around is perhaps 15 degrees, and some speculate that these guys pitched up harder. We also know, as it was officially reported by the investigators, that they crashed with more than 50deg nose down. That gives you a total pitch change of some 65 degrees nose down. We also know (again officially released by the investigators) that they achieved -1G.

                          --- 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


                          • Originally posted by Evan View Post
                            In that case, the pitch went from +25 to -75 over a period of 45 seconds and the crew still flew it into the ground. How many negative G's is that?
                            That's 100 deg in 50 seconds (to make it easy), 2 degrees per second (if it was evenly distributed). Unless that happened at a quite high speed, that rate of pitch rate doesn't require a negative G at all. A take-off standard pitch rate is 3 deg per second and you are not anywhere near 3G*.

                            (Why 3G? In the FlyDubai accident they reached -1G. That is 2Gs below the non-accelerated flight at 1G. 3Gs is also 2Gs from 1G, just in the other direction. At a given speed, it takes the same pitch rate to produce the same change in Gs to either direction).

                            --- 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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                            • Evan, I am not sure of this, but I think that this illusion that you mention is related with the direction of the apparent acceleration vector, and it is what the simulators use to fool you and make you think that the plane is accelerating forward (take-off run) or backwards (or decelerating, landing run).

                              The longitudinal acceleration and the gravity pull (that is comparable to a 1G acceleration) combine to create and apparent G vector. It is impossible to discern if the tilt of the apparent G vector is due to being tilted or being in the combination described below. When the plane accelerates for take-off, you feel that you are thrown against the seat back, and of course you also feel your wight pressing your butt on the seat cushion. As the airplane rotates and establishes itself on a steady climb at constant speed, you are only under the gravity now (no more acceleration) but you still feel the same because, being the plane tilted nose-up, the gravity has a "seat back" component and a "seat cushion" component.

                              This illusion caused several accidents when taking off in IMC or into the darkness. If the pilot feels (or sees in the AH) that the nose is a bit too much up, he will lower it a bit, but the sensation will be as if it didn't move because now, with a lower pitch and climb gradient, the plane, under the same thrust that it had before, will accelerate, and the push due to that acceleration at a lower pitch will replace the previous push of the gravity at a higher pitch. If the pilot is fooled by this illusion, he will keep pushing down and down, more and more pitch-push being replaced by more and more acceleration push. By when he notices that the nose is way too down it may be too late.

                              Now, this illusion doesn't work if:
                              - The pitch rate changes quickly, because the inner ear is quite good at detecting quick changes in pitch rate (not so much in pitch itself).
                              - If the maneuver is accompanied by a significant reduction in G forces due to the pitch down, because a reduction of the G forces below 1G is naturally by our body with a falling sensation, so that would be a very strong cue for the pilot that the nose is going down indeed.

                              Something similar can happen in an approach: While descending at constant rate and speed you feel pushed forward by the gravity (that, in the tilted plane, had a forward component). If the nose goes up slowly, the "nose up" motion can be totally missed, and the forward pull would still be there (now due to the deceleration instead of the gravity component) and, if undetected (and no AT), the plane would loose speed, stall, spin, crash, burn, die.

                              The FlyDubai had a very strong change in pitch rate and a very strong reduction (inversion, in fact) of the normal acceleration. It looks to me that they could not miss the cue that the plane was pitching violently nose-down.

                              --- 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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                              • Originally posted by Gabriel View Post
                                The FlyDubai had a very strong change in pitch rate and a very strong reduction (inversion, in fact) of the normal acceleration. It looks to me that they could not miss the cue that the plane was pitching violently nose-down.
                                That's my feeling as well. I wasn't aware of the -1G thing before but I'd sure expect the sensation of -1G would override any illusion that the plane was flying straight and level.

                                Unless... the weather was really *that* severe? But even in "garden variety" severe weather, you might experience -1G for a fraction of a second, not long enough for the plane's pitch to change 65 degrees.
                                Be alert! America needs more lerts.

                                Eric Law

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