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  • British Airways fly-by salute, or...

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

    Something's not cricket here. PIO?

  • #2
    Originally posted by Evan View Post
    https://www.youtube.com/watch?v=IkGTg_UOBNY

    Something's not cricket here. PIO?
    It looks intentional, based on the spoiler inputs (and the lack of screams inside the plane).

    --- 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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    • #3
      Originally posted by Gabriel View Post
      It looks intentional, based on the spoiler inputs (and the lack of screams inside the plane).
      The only other thing I can imagine is a flight control issue, perhaps an issue with the flight stick or perhaps something delaying pilot commands to the control surfaces, perhaps resolved by a priority take-over. But I don't have any precedent for that. So it's looking to me like PIO.

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      • #4
        Originally posted by Gabriel View Post
        It looks intentional, based on the spoiler inputs (and the lack of screams inside the plane).
        Diverted to Malaga due to strong winds

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        • #5
          It was a go-around from 300 ft in the middle of a tight turn.
          https://flightaware.com/live/flight/...835Z/EGLL/LEMG

          I would still not call it PIO in the traditional way since I see no overshooting due to inertia and lack of dampening, at least in the last couple of oscillations that were captured from inside the plane. It looks more like the pilot (or autopilot) overcorrecting the TRACK while trying to keep the plane in the very narrow space between the Spanish airspace and the Rock, both of which they are not allowed to overfly.

          --- 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


          • #6
            Originally posted by Gabriel View Post
            It was a go-around from 300 ft in the middle of a tight turn.
            https://flightaware.com/live/flight/...835Z/EGLL/LEMG
            121kts

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            • #7
              Originally posted by Evan View Post
              121kts
              Groundspeed. They had like 25 knots of headwind on final.

              Metars:
              LXGB 251050Z 09023G33KT 9999 FEW025 16/10 Q1032 NOSIG=
              LXGB 250950Z 08026G36KT 9999 FEW022 16/10 Q1032 TEMPO SCT022=
              LXGB 250930Z 09025G35KT 9999 FEW020 16/10 Q1031 BLU TEMPO SCT020 WHT=

              --- 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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              • #8
                Originally posted by Gabriel View Post
                Groundspeed.
                Aha.

                Comment


                • #9
                  https://twitter.com/British_Airways/...elo-vientos%2F

                  --- 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


                  • #10
                    Lee wave rotor?

                    Comment


                    • #11
                      Originally posted by pegasus View Post
                      Lee wave rotor?
                      Looks like you are the winner!!!

                      https://www.youtube.com/watch?v=tjv3xBB-HmY

                      https://www.youtube.com/watch?v=3BkOgZPjZX4

                      --- 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


                      • #12
                        Originally posted by Gabriel View Post
                        Us glider pilots know a thing or two about wave, A fellow pilot has flown 1000km and returning to home base using the phenomenon.Incidentally, I think there is an error in the Mentour presentation, the lee wave rotor was created by a Northerly wind not one from the South.

                        Comment


                        • #13
                          Originally posted by Gabriel View Post
                          Looks like you are the winner!!!

                          https://www.youtube.com/watch?v=3BkOgZPjZX4
                          Great video. I'd love to see a DFDR plot of this event, to see how A/P handled the roll excursions. My guess is that there would be very little, if any, rudder involved. I also wonder if the autopilot inputs were excessive or poorly timed. Has there ever been a case of auto-pilot induced occillation?

                          Comment


                          • #14
                            Originally posted by Evan View Post
                            My guess is that there would be very little, if any, rudder involved.
                            Probably, especially if it was on AP.

                            I also wonder if the autopilot inputs were excessive or poorly timed. Has there ever been a case of auto-pilot induced oscillation?
                            It shouldn't. APs (even old analog ones) have at least what is called a PID control system (Proportional-Derivative-Integrator). Modern digital APs have even more robust control logic, but basically this kind control system has a target bank angle, in function of the difference between the target and actual bank angles it establishes a target roll rate, and in function of the difference between the target roll rate and the actual roll rate it establishes a control input. In other words, even if the AP wants the plane to roll to the right towards a specific bank angle (say it is in a left turn and wants to return to wings level), the control input may be to the left if the plane is already rolling to the right towards the target at a rate higher than the target rate. And the target roll rate diminishes as you approach the target bank (and becomes zero at the target). With the parameters correctly set, an AP should be at least critically dampened and should not have PIO. Now, being this a digital AP, there can be a bug or some specific circumstances or combination of variables that was not foreseen when developing the code. But it would be strange that it had not surfaced until this week. The A320 has too many years in service for something like this to remain hidden.

                            What is strange here is that in the video you can clearly see that the control inputs to "level the wings" persist even after the plane has already overshot the wings-level condition, as if it intentionally wanted to bank to the other side now. That is not PIO.

                            That's why I said that it looks more like the pilot (or autopilot) over-correcting the TRACK while trying to keep the plane in the very narrow space between the Spanish airspace and the Rock, both of which they are not allowed to overfly. Like a PIO but not in roll but in track (which is colloquially called "sewing").

                            I am totally speculating now, but perhaps the AP was set in a lateral mode that it would track a VOR radial or the ILS LOC, which become more sensitive as you approach the station (because you cover more angular deviation from the same lateral deviation). Old APs were known to have problems with that, causing "sewing" (and human pilots too), so the practice was to change the AP from NAV to HDG when you were close to the station. But new APs should be immune to that. They know the distance to the station so they know what is the actual lateral deviation for a given angular deviation. They also have INS information to integrate in the logic and even without all that, given the TAS (which they know) they could easily "reverse-calculate" the actual lateral deviation from the speed that the angular deviation changes when the plane changes the heading during the maneuver.

                            Now say that. for whatever reason, this was not the case. Say that the AP had a strike of "nostalgia" for the old APs, or that something went wrong with the tricks to prevent "sewing" or that the human pilot was blindly following the commands of the FD (which should also be immune to sewing, but say that it was not). This would very nicely explain why so many roll "excursions" (that were at the same time well controlled so the plane never exceeded the normal bank angle limits) and suddenly everything stopped.... the instant the pilot selected HDG mode.

                            I'd also love to see the FDR (and CVR would be interesting too, if not funny). But since this apparently didn't even qualify as an incident, chances are that we will never know.

                            --- 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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                            • #15
                              Originally posted by Gabriel View Post
                              This would very nicely explain why so many roll "excursions" (that were at the same time well controlled so the plane never exceeded the normal bank angle limits) and suddenly everything stopped.... the instant the pilot selected HDG mode.
                              This is sort of along the lines of what I was thinking. The roll occillations just so abruptly stop, as if something in the flight control authority has suddenly changed, like a mode change, for instance. Or perhaps that is the nature of rotor turbulence caused by a large Spanish rock. I wouldn't know.

                              I was thinking that, since the initial roll excursion was uncommanded (an upset rather than an intention), would the AP logic—up to a point— simply rely on the aircraft's lateral stability to restore wings level (no flight control inputs)? And if that point is around 33 bank, would something in the logic THEN command a counter-rolling flight control movement? Because that is what appears to be happening in the video showing the delay in the spoiler deployment. I wouldn't expect such a delay from the autopilot unless it was intentionally delayed.

                              The A320 normal law in roll requires a pilot in manual flight to maintain full stick deflection to exceed 33 of bank. It also introduces THS limits at this point. So perhaps there is a similar functional threshold in autoflight at this bank angle.

                              Is it possible that there is a bit of an oversight in some flight control algorithm that only reveals itself in this rare combination of circumstances? Something that can lead to A/P-induced occillation... until another mode is selected or the A/P is disconnected (something I might expect the pilots to do if this was happening under autoflight)... ?

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