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  • #46
    3BS, NO FOOTNOTE FOUND.

    but, it doesn't make a difference. every twin engined commercial aircraft that has been certified, was certified to fly on ONE engine, including on takeoff with full thrust.

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    • #47
      Originally posted by Gabriel View Post

      But they do have yaw damper, don't they?

      I do wonder if the AP / yaw-damper are capable of handling a high thrust-asymmetry situation without pilot input on the pedal or rudder trim.
      AFAIK the yaw damper is limited to 3deg rudder deflection from the trimmed position. That assumes it is operative. The classics have a single yaw damper which is not required for dispatch. And this is Indonesia.

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      • #48
        Originally posted by TeeVee View Post
        THE FOOTNOTE IS THERE.

        but, it doesn't make a difference. every twin engined commercial aircraft that has been certified, was certified to fly on ONE engine, including on takeoff with full thrust, AS LONG AS THE ‘PILOTS’ MAINTAIN A MINIMUM CONTROLLABLE AIRSPEED.
        1. Fixed
        2. Footnote- Quit being like me, go back and read more carefully.
        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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        • #49
          Yaw damper Blah, Blah, Blah
          Contrasted with Evan’s disdain for rudder use...
          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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          • #50
            Note: We are going to be embarrassed if this is something other than a pilot-botched scenario of losing control of an asymmetrically-powered airplane.
            Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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            • #51
              Originally posted by TeeVee View Post
              every twin engined commercial aircraft that has been certified, was certified to fly on ONE engine, including on takeoff with full thrust.
              Yes, but not necessarily without pilot intervention* (or inappropriate pilot intervention). Again, I don't know if the AP will or will not keep control of the plane by itself in a highly asymmetric thrust situation.

              *FOOTNOTE: And as 3WE said, only as long as you keep the speed above Vmc

              --- 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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              • #52
                The All Nippon NH140 upset incident in 2011 illustrates both how a pilot not concentrated on flying can fail to recognize an increasing roll upset and how quickly it can result in a near-inverted dive. The PF didn't recognize the situation and intervene until the bank angle was at 50deg, and the angle reached 80deg before arresting. When he reacted to stickshaker and then directed his attention away from roll and to the rudder trim, the roll once again increased to 132deg! The pitch angle was -35deg and the speed reached M.82. The max VS was 440fpm. The loss of altitude was a bit over 6000ft.

                The entire duration of the incident from the onset of roll from level to the restoration of level flight was 40 seconds!

                This incident also illustrates the limited capability of the AP to compensate for roll excursions. The AP was in LNAV and moved the yoke to a maximum of 22deg before reaching its limit. The aircraft continued to roll beyond the bank angle alert at 35deg. Nevertheless, the AP remained engaged in LNAV until the pilot manually operated the yoke, causing AP to transition to CWS ROLL.

                So, it's clear to see how even a half minute of inattention by the PF in IMC can take things from an undetected roll due to thrust assymmetry to a near inverted dive.

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                • #53
                  Originally posted by Evan View Post
                  •••So, it's clear to see how even a half minute of inattention***.
                  I have the solution:

                  1. Every 15 seconds, a railroad like dead-man button must be pushed.

                  2. This cues the PF to go though a Japanese-style scan of attitude, speed, altitude heading, power, and navigational status.

                  3. Every minute, the PM does the same, INCLUDING SECONDARY ITEMS...


                  https://youtu.be/9LmdUz3rOQU

                  This would have helped Hui Theiu Lo maintain 777 Airspeed while landing on a beautiful sunny afternoon, too.



                  Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                  Comment


                  • #54
                    Originally posted by Evan View Post
                    This incident also illustrates the limited capability of the AP to compensate for roll excursions. The AP was in LNAV and moved the yoke to a maximum of 22deg before reaching its limit. The aircraft continued to roll beyond the bank angle alert at 35deg. Nevertheless, the AP remained engaged in LNAV until the pilot manually operated the yoke,
                    The problem is not so much roll excursions but if there is a continuos "force" (moment) inducing the roll and if the AP is "strong enough" to overcome it. I am quite sure that if you have a sudden huge but short-lived roll excursion, the AP will be able to level the wings back afterwards.

                    In the incident you mentioned, the pilot accidentally did an outrageous rudder trim input when he mistook the door switch with the rudder trim switch, activating it twice and keeping it activated during several seconds the second time, causing an enormous rudder deflection that I am quite sure at that speed was a much stronger asymmetry than an engine at TOGA and the other at idle.

                    And yet, they lost 600ft in 40 seconds, not more than 10K feet in less than 30 seconds. And, the pilot did many things wrong, but let's recognize that he was able to recover from his own mistake alone (he was the only pilot in the cockpit at that moment).

                    That said, I agree with the core of your message, a slow and subtle roll excursion can very quickly become a major upset with the airplane diving inverted. 5-degrees-per-second roll, which "nothing" in terms of roll rates, will become 100 degrees of bank (hence inverted) in 20 seconds, surely accompanied by a very low nose too. If at that point the pilots freak out and pull up, well, up is more 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 ---

                    Comment


                    • #55
                      Originally posted by Gabriel View Post
                      In the incident you mentioned, the pilot accidentally did an outrageous rudder trim input when he mistook the door switch with the rudder trim switch, activating it twice and keeping it activated during several seconds the second time, causing an enormous rudder deflection that I am quite sure at that speed was a much stronger asymmetry than an engine at TOGA and the other at idle.
                      The maximum rudder deflection was 5deg. Yes, that's a lot at M.72. How that compares to a climb thrust asymmetry is hard to say because we don't know the degree of asymmetry, but I'm also considering that the upset might have been preceeded by loss of airspeed, stickshaker and a full TOGA thrust assymmetry.

                      And yet, they lost 600ft in 40 seconds, not more than 10K feet in less than 30 seconds. And, the pilot did many things wrong, but let's recognize that he was able to recover from his own mistake alone (he was the only pilot in the cockpit at that moment).
                      6000ft, not 600ft.

                      And consider that the pilot never sensed the increasing roll. When he looked at the door video and realized that the PIC was having trouble with the door lock, he glanced over and saw his mistake with the rudder trim switch. Only then did he think to check the attitude on the PFD. If he hadn't done this, it might have become unrecoverable (recovery required exceeding the 2.5G design limit). If the Indonesian crew had not detected the upset until 15-20 secs into the dive, I think the scenario might fit.

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                      • #56
                        Originally posted by 3WE View Post

                        1. Fixed
                        2. Footnote- Quit being like me, go back and read more carefully.
                        who puts a FOOTnote in middle of the post?

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                        • #57
                          By the way, TeeVee and Bobby, how are the Dolphins doing?

                          This is an indirect answer to "Who puts a footnote in the middle of a post" [wink].
                          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                          • #58
                            no clue about dolphins. i'm a seahawks fan and clearly we pranged the season

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                            • #59
                              Originally posted by TeeVee View Post
                              no clue about dolphins. i'm a seahawks fan and clearly we pranged the season
                              Hmmmm .... I'm stilll a 49ers fan. My season ended ... again ... after the first few rounds.
                              My photos on Flickr www.flickr.com/photos/geridominguez

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                              • #60
                                Latest non-news from AvHerald:

                                On Feb 2nd 2021 the KNKT chairman said in a press conference, that reports distributed by western media about a possible autothrottle malfunction causing asymmetric thrust are wrong. However, the KNKT sent 5 pieces of debris, including the autothrottle unit (but not identifying the other parts), to the USA and UK for further examination stating they want to find out why an autothrottle parameter changed. He re-iterated they don't know why that parameter changed and need confirmation from the parts sent to the USA and UK and the CVR. The maritime search for the CVR is still ongoing.
                                Don't you love the openness of those guys?

                                --- 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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