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Thread: A380 Rudder Reversals

  1. #61
    Senior Member Evan's Avatar
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    Quote Originally Posted by Schwartz View Post
    Hi Evan,

    I may be remembering incorrectly, but I thought in the one case of the New York crash there were several contributing factors:
    1) The pilot made several alternating full deflection rudder control inputs unnecessarily to deal with wake turbulence
    2) The A300 did NOT have fly by wire and thus the rudder inputs at high speed were extremely sensitive to control inputs and it was easy for the pilot to call for full deflection. My understanding is that in most fly by wire jets, the controls are dampened at higher speed meaning the pilot has to provide a lot more pressure at the limit of the pedals to get a full deflection
    3) The pilots were trained by AA to aggressively deal with wake turbulence which was unnecessary in large airliners

    In this case:
    1) The A380 is fly by wire and undoubtedly the rudder controls are quite different from the A300 that crashed
    2) This plane was landing at low speed and not at full maneuvering speed
    3) I don't see anywhere near full rudder deflection. The A380 looks like it has two separate control surfaces on the rudder and the first few larger deflections before touchdown only involve one of the surfaces. Once the plane is down, the two segments seem to operate together, but again no where near full deflection.

    So, it doesn't seem like any the conditions that caused the A300 NY crash were present here.

    EDIT: Just to add here, this landing looked ugly because the pilot overcompensated on the first couple oscillations. It was similar to a car at high speed who over swerves at first to avoid something that fell out of the car ahead. You can't even do a full steering deflection, but it can cause loss of control or an ugly looking swerve oscillations for a few seconds while the driver recovers. This is what it looks like to me.

    One question I have for the big pilots, is the nose wheel steering and rudder coordinated by the computer when landing one of these big jets?
    Ugh... ok, I'm sorry, I guess I need the red font here... This incident has nothing to do with risk of structural fin failure. I've said this several times already. Can we please all get that much straight?

    What concerns me here is improper use of rudder, in reversals, doublets, whatever you prefer to call them.

    Why?

    Because they are unnecessary and unsuited to large transport aircraft and tend to result in pilot-induced occillations, overcontrol, overswing and, yes, structural failure.

    Because when a pilot uses aggressive rudder like this it is an indication of either a) panic and bad instincts, b) improper training and understanding of rudder on large transport aircraft and/or c) aircraft-pilot coupling resulting from a triggering event, in this case a sudden wind shear. gust, call it what you will.

    Because the pilot who broke AA587 and killed everyone on board had also displayed such behavior of several occasions prior to that crash and nobody took it too seriously.

    Because since then EVERY pilot should understand the SIMPLE FACT that rudder on these aircraft is not intended, nor designed, to be used in this manner. It is there for steady state inputs to compensate for crosswinds and engine failure and occasionally for very careful manuevering.

    Never for roll, unless in a very high AoA where ailerons are no longer effective, because phase lag leads to PIO and overcontrol and structural failure...

    Not needed for torque compensation or turn coordination. Not a Cessna.

    Never used in large alternating reversals as seen here.

    Not a wise alternative to go-around when roll alone cannot align you with the runway, for reasons that this video makes painfully obvious.

    Because what a pilot displays a methodology involving rudder reversals in a situation like this (which is not structurally dangerous to the fin) there is a good chance that it may be repeated at higher speeds, perhaps in wake turbulence, where it is structurally dangerous, in an aircraft with 400+ souls on board.

    Essentially, and for all the above reasons, because it is alarming pilot behavior.

    The non-FBW A300 has a rudder travel limiter. All modern transport aircraft limit rudder deflection as airspeed increases. It is not exclusively a FBW thing. It won't save the structure from deliberate abuse however...

  2. #62
    Member ATLcrew's Avatar
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    Quote Originally Posted by 3WE View Post
    Furthermore, speculation of the magnitidue of A from a telephoto youtube is problematic at best. I have yet to see Gabby, Bobby, Schwartzy, ATLie nor 3BSie stating that it is clear to them that this was a structurally significant landing.
    Actually, the airplane will tell you if the landing was "structurally significant". There is a report that can be pulled up, or will be generated automatically, depending on software configuration.

  3. #63
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    Ugh... ok, I'm sorry, I guess I need the red font here... This incident has nothing to do with risk of structural fin failure. I've said this several times already. Can we please all get that much straight?

    What concerns me here is improper use of rudder, in reversals, doublets, whatever you prefer to call them.
    We have it straight, and 'nothing to do with' is an absolute statement...it's you that is claiming all around rudder mismanagement.

    You; however, are obsessed with rudder reversal (and your additional terms).

    Personally- I hope airline pilots think nothing of doing rudder reversals. Personally, I think I feel them on just about every takeoff and landing...little swerve left...little swerve right.

    I see this same behaviors from semi-trucks, busses, cars, bicycles and Mattel Big wheels.

    I do concur; though, I very rarely see reversals from my computer keyboard.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  4. #64
    Senior Member Evan's Avatar
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    Quote Originally Posted by 3WE View Post
    Personally- I hope airline pilots think nothing of doing rudder reversals.
    Well, professionally, Airbus, Boeing, the NTSB, the FAA and hopefully most airlines pilots do not share your wishes.

    Quote Originally Posted by Boeing
    Boeing aircraft are not designed to a requirement of full authority rudder reversals from an “over yaw” condition. Sequential full
    or nearly full authority rudder reversals may not be within the structural design limits of the aircraft, even if the airspeed is below
    the design manoeuvring speed. There are no Boeing Procedures that require this type of pilot input. It should also be pointed out
    that excessive structural loads may be generated in other areas of the aircraft, such as engine struts, from this type of control input.

  5. #65
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    Two words for you Evan, Cross control.

  6. #66
    Senior Member 3WE's Avatar
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    Quote Originally Posted by ATLcrew View Post
    Actually, the airplane will tell you if the landing was "structurally significant". There is a report that can be pulled up [snip].
    ...if we only had a web-link to these reports we could do so much more to help the industry.
    Last edited by 3WE; 10-11-2017 at 03:09 PM. Reason: Change font color to blue to indicate sarcasm.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  7. #67
    Senior Member 3WE's Avatar
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    Quote Originally Posted by Evan View Post
    Well, professionally, Airbus, Boeing, the NTSB, the FAA and hopefully most airlines pilots do not share your wishes.
    Mr. Black and White:

    -Not all rudder reversals are full-deflection reversals- except in your obsessive mind. (Yeah, it would appear that one reversal happened here)
    -Hard right rudder as you are shooting towards the left of the runway is a reasonable practice.
    -Holding hard left rudder to get to the center of the runway in a crosswind scenario is a reasonable practice.
    -Sometimes people over-steer a bit. AND THEN: Alert, situationally-aware operators manage the over steer...(sorta like what happened here)

    This is a significant problem with car drivers who are not paying attention and drift right, and then over-correct to the left, and sometimes lose control and/or have head on collisions with oncoming traffic. For these cases, I do think that improvements to recurrent training and situational awareness are in order.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  8. #68
    Senior Member 3WE's Avatar
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    Boeing Bobby and ATLCrew: Please note the instructions below on how you are supposed to operate your aircraft and it's rudder:

    Quote Originally Posted by Evan View Post
    The rudder is there for steady state inputs to compensate for crosswinds and engine failure and occasionally for very careful maneuvering.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  9. #69
    Senior Member Evan's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    Two words for you Evan, Cross control.
    Involving cyclic rudder reversals?

  10. #70
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    Quote Originally Posted by Evan View Post
    Involving cyclic rudder reversals?
    I was not there so I can't tell you what he did or why. What I can tell you is that if it is gusty you do what you need to do.

  11. #71
    Senior Member 3WE's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    ***you do what you need to do.***
    Oh hell no! 1. You cannot be trusted and 2. The proper methods are right here for you to read for yourself.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  12. #72
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    Quote Originally Posted by 3WE View Post
    Oh hell no! 1. You cannot be trusted and 2. The proper methods are right here for you to read for yourself.

    Now I know about the blue...

  13. #73
    Senior Member 3WE's Avatar
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    By the way...

    Who here has ridden on a Jestream 31?
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  14. #74
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  15. #75
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    Quote Originally Posted by BoeingBobby View Post
    That kid reminds me of someone else at that age way more than he should.

  16. #76
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    Quote Originally Posted by ATLcrew View Post
    That kid reminds me of someone else at that age way more than he should.

    Scary isn't it? Me too.

  17. #77
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    Not that impressive. Extending the flaps by gravity? Come on! Any 5 y/o knows better.

    --- 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 ---

  18. #78
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    Quote Originally Posted by Gabriel View Post
    Not that impressive. Extending the flaps by gravity? Come on! Any 5 y/o knows better.
    It's not in blue font, so I guess you are just a killjoy. You probably don't like puppies either!

  19. #79
    Senior Member Gabriel's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    It's not in blue font, so I guess you are just a killjoy. You probably don't like puppies either!
    It was a joke, blue font or not. When I say a joke during a spoken conversation I don't talk with blue font either.
    "Any 5 y/o knows better" should have been a good hint.

    --- 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 ---

  20. #80
    Senior Member 3WE's Avatar
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    Quote Originally Posted by BoeingBobby View Post
    Scary isn't it? Me too.
    The question is if young ATL and Bobby participated in internet discussion forums and liberally doled out advice to the aviation industry. / blue font.
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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