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British Airways fly-by salute, or...
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Originally posted by Evan View Post
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Originally posted by Gabriel View PostIt looks intentional, based on the spoiler inputs (and the lack of screams inside the plane).
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It was a go-around from 300 ft in the middle of a tight turn.
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 ---
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Originally posted by Evan View Post121kts
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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--- 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 pegasus View PostLee wave rotor?
British Airways BA492 Gibraltar Aborted landing 25th Feb 2019 Film from inside the aircraft from about 7 minutes out of Gibraltar. Starting at 05:30 we hit s...
--- 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 PostLooks like you are the winner!!!
British Airways BA492 Gibraltar Aborted landing 25th Feb 2019 Film from inside the aircraft from about 7 minutes out of Gibraltar. Starting at 05:30 we hit s...
https://www.youtube.com/watch?v=3BkOgZPjZX4
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Originally posted by Gabriel View Post
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Originally posted by Evan View PostMy 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 oscillation?
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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Originally posted by Gabriel View PostThis 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 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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