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Thread: A380 Rudder Reversals

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    Senior Member Evan's Avatar
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    Default A380 Rudder Reversals

    Overcontrol?

    Should this be a go-around?

    Some big gusts at Düselldorf yesterday...

    https://www.youtube.com/watch?time_c...&v=roS6oFjCDhc

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    Overcontrol? No.

    Should this be a go-around? How many times have we discussed what you should almost always not_do AFTER touchdown- except in very grossly obvious cases- like a school bus full of nuns taking the runway?

    Some big gusts at Düselldorf yesterday... Yes.

    https://www.youtube.com/watch?time_c...&v=roS6oFjCDhc
    Ok, I love a good crosswind video, but you are extra out of touch in recent days.

    Looked like a very nicely executed properly-controlled landing, and your use of the insider-jargon buzzwords "rudder reversal" is very off base.

    However...

    I will acknowledge that I am arm-chair perplexed as to why there was sustained full left rudder (NOT_a rudder reversal) AFTER a what looked like a very nice touchdown...

    Full left rudder that was totally appropriate at first, but then which seemed to result in some big time swerves and that always amazing sideways sliding that airliner landing gear seems to tolerate so well.

    Now, all of that being said- as a mature, parlour-talking ass-hat:

    1. You have the highly compressed telephoto view of the world that may not represent reality.
    2. Who says those swerves are any worse than what you see on your typical crosswind YouTube?
    3. I wasn't sitting there in the cockpit (nor am I A-380 rated)...maybe the full left rudder was exactly (or maybe even not exactly) what was indicated from where they were sitting (restating, I am sitting in a chair in front of a computer).
    4. Or maybe it was a human-factor's brief hiccup of holding left rudder a couple of seconds too hard. (Please update us on how your drivers-ed program or tricycle riding is going to understand the occasional need for corrective control inputs.)

    Finally- where in the hell do you get the idea to go-around? It was a beautiful touchdown, I'm sure all the spoilers popped and the plane settled, but you want them to power up because they are swerving on the runway a bit?...I'm thinking that is probably not_a good choice...
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    Senior Member Evan's Avatar
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    Quote Originally Posted by 3WE View Post
    I will acknowledge that I am arm-chair perplexed as to why there was sustained full left rudder (NOT_a rudder reversal) AFTER a what looked like a very nice touchdown...
    Ok, try it again with your eyes open.

    One thing this video shows us is the power of that enormous full rudder, which needs to be handled carefully. It's hard to tell how much deflection is involved with the telephoto distortion, but it has a very significant impact on yaw. After the bounce, it goes quickly to right deflection and the aircraft veers aggressively back across the centerline to the right. The amount of rudder input here seems excessive but I realize the winds were extremely challenging yesterday. I wouldn't want to be piloting that approach. And they certainly got it sorted out. But it makes me wonder about how well they are training crews on rudder for these jumbos, which rarely need much at all.

    The hard touchdown without the right mains (and subsequent bounce) leads me to question a go-around, but also was the turbulence worthy of abandoning this sooner.

    From what I can tell, the weather wasn't necessarilly better at the nearby alternates.

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    Quote Originally Posted by Evan View Post
    Ok, try it again with your eyes open.

    One thing this video shows us is the power of that enormous full rudder, which needs to be handled carefully. It's hard to tell how much deflection is involved with the telephoto distortion, but it has a very significant impact on yaw. After the bounce, it goes quickly to right deflection and the aircraft veers aggressively back across the centerline to the right. The amount of rudder input here seems excessive but I realize the winds were extremely challenging yesterday. I wouldn't want to be piloting that approach. And they certainly got it sorted out. But it makes me wonder about how well they are training crews on rudder for these jumbos, which rarely need much at all.

    The hard touchdown without the right mains (and subsequent bounce) leads me to question a go-around, but also was the turbulence worthy of abandoning this sooner.

    From what I can tell, the weather wasn't necessarilly better at the nearby alternates.

    Really?

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    ***But it makes me wonder about how well they are training crews on rudder for these jumbos, which rarely need much at all.***
    Wait a second...WOW...do you realize that this goes all the way back to your overly warped thoughts on AA-587.

    While I do not know what the FCOM and memory checklist says for the specific A-380 model in the video...

    ...I have a super incredibly vivid memory of an A-320 pilot (here I think?) saying something to the effect of this (regarding crosswind landings).

    "Use rudder as-appropriate to manage yaw".

    AND, FAR BE IT FROM ME TO THINK I MIGHT HAVE ANY ABILITY TO HANDLE BOEING BOBBIE'S 747....I'm going to run my mouth off and say that I bet the man USED to use some rudder inputs of significance during cross wind landings.

    And my eyes are just fine as I see a very well controlled descent and touchdown (reference your comment that they should have gone around sometime before the flare).

    As I said, I always love watching videos like this...apparently you do not...Videos like this are laden with remarkable rudder, elevator and aileron inputs...and some back-and-forth swerving on the ground.

    The search feature (as well as the 'list-similar-videos' feature) on YouTube is your friend.

    Repeating- get out of the protective bubble...ride the tricycle fast and turn it hard...learn to drive a car...go to the airport fence on a windy day (just steer clear of the photographers- as the world can be a dangerous place).

    Footnote: I am now laughing at the ironing that probably the worse crosswind I ever experienced as an airline passenger...we broke the right main shimmy damper on a 737.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    Really?
    Yeah, obviously the German Aviation authorities should have shut down all the airports that day, as pilots are not capable of the pictured wind conditions...
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    Senior Member Evan's Avatar
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    Quote Originally Posted by 3WE View Post
    Wait a second...WOW...do you realize that this goes all the way back to your overly warped thoughts on AA-587.
    You mean the NTSB's "warped" thoughts? Yes, indeed it does.

    This landing appears to have a bit of overswing involved and may be the result of what that report described as 'Aircraft-Pilot Coupling' (APC), the trigger being the turbulence, which led to overcontrol/overswing.

    The report is quick to point out the Aircraft-Pilot Coupling does not indicate poor airmanship, it's just an observed phenomenon.

    Also, it doesn't appear to be a typical crosswind landing, where a more-or-less steady-state rudder input is involved, but rather a sudden strong gust requiring quick corrective rudder input. That is identified as a common trigger for APC.

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    Also, it doesn't appear to be a typical crosswind landing, where a more-or-less steady-state rudder input is involved, but rather a sudden strong gust requiring quick corrective rudder input.
    Yes, I recall from 172 school how we distinguished steady-state crosswinds from gusty ones. Totally different procedures- and much time practicing both during separate lessons.
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    Quote Originally Posted by 3WE View Post
    Yeah, obviously the German Aviation authorities should have shut down all the airports that day, as pilots are not capable of the pictured wind conditions...

    Really, Really!?

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    You mean the NTSB's "warped" thoughts? Yes, indeed it does.
    No.

    Their thoughts included his training to use rudder for upset recovery and cited the force and pedal deflections that were involved.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    Really, Really!?
    Well...blue font really.
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    Quote Originally Posted by 3WE View Post
    Well...blue font really.

    I forgot the code, remember I am an old fart. Does blue equal sarcasm?

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    1. ...a bit of overswing...
    2. ...APC...
    3. ...Blah blah blah, APC blah blah blah...
    1. So what is the difference between 'a bit of overswing' and 'a reversal'? Did we maybe use the wrong word earlier?
    2. If you say something dumb, try to look smart with big words and acronyms.
    3A. And yes, dig yourself a deeper hole on how the pilots should have made rudder inputs.
    3B. Repeating from above- try running the bicycle down a hill with a few curves and bumps...and then start asking yourself if the big words and acronyms have any relation.

    Confession: The more I think about it, I don't believe I was ever trained in the technique of a steady-state crosswind landing...Me stupid...defer Boeing Bobby for explanation.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    Senior Member 3WE's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    I forgot the code, remember I am an old fart. Does blue equal sarcasm?
    I have explained it to you twice previously...and you do sometimes read my posts, and might be able to make some inferences?
    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 BoeingBobby View Post
    I forgot the code, remember I am an old fart. Does blue equal sarcasm?
    Changing the subject- I am amazed at all of the swerving and sliding that SEEMS to be depicted on these crosswind videos...

    ...did you ever do crosswind landings that resulted in 'impressive sideways movement'.

    Sometimes it seems like there's two variations and no middle ground.

    Variation 1: A well-timed crab kickout with a nice SLIGHT upwind wing dip and relatively straight touchdown.
    Variation 2: Rather nasty-looking sideways touchdown. (Although I believe more and more that it only LOOKS nasty- sure the passengers would feel some swerves, but not a near-death expereince).

    -Heck, a little back and forth swerving on a typical takeoff is pretty common from my experience in 23A.
    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 3WE View Post
    Changing the subject- I am amazed at all of the swerving and sliding that SEEMS to be depicted on these crosswind videos...

    ...did you ever do crosswind landings that resulted in 'impressive sideways movement'.

    Sometimes it seems like there's two variations and no middle ground.

    Variation 1: A well-timed crab kickout with a nice SLIGHT upwind wing dip and relatively straight touchdown.
    Variation 2: Rather nasty-looking sideways touchdown. (Although I believe more and more that it only LOOKS nasty- sure the passengers would feel some swerves, but not a near-death expereince).

    -Heck, a little back and forth swerving on a typical takeoff is pretty common from my experience in 23A.

    Me? Never! All of mine were like butter! cough...cough

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    Senior Member Evan's Avatar
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    Quote Originally Posted by 3WE View Post
    1. So what is the difference between 'a bit of overswing' and 'a reversal'?
    A reversal, which we are witnessing here, is a successive cyclic rudder deflection from one direction to the opposite direction without first centering it in the neutral position. It doesn't appear to be full rudder deflection reversals but who knows. The structural danger in doing this probably isn't present at landing speeds, but overcontrol can result and this can lead to further occillations, as I believe we seeing here.

    An overswing results when a rapid rudder input is applied. An overswing is a sideslip angle that is initially greater than the steady-state sideslip angle resulting from the same rudder input and occurs because of the slightly underdamped nature of the airplane’s motion in the yaw axis.

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    Senior Member Evan's Avatar
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    Quote Originally Posted by 3WE View Post
    No.
    Yes. You should read the report some time instead of living in denial of the fact that a large transport aircraft rudder is not designed to be used like that of a Cessna.

    If you don't trust the NTSB, you can read the same thing from Boeing, Airbus and the FAA.

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    I would love to hear from Gabriel, but I'm guessing that once the nose gear is down, the nose friction is going to provide the overriding force controlling direction in these cases. In the video above, it only looks like the main gear skidded sideways just a small bit on the outside of two of the swerves (there was a small puff of rubber smoke on 2 of the main gears wheel assemblies). The rest of the "sliding" is actually the plane zig zagging on the runway with the main wheels following the track of the nose, just like a car would.

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    Quote Originally Posted by 3WE View Post
    Well...blue font really.
    The sarcasm was so obvious that I didn't even realize about the blue font.

    --- 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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