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AP: Cubana Crashes on Takeoff From Havana

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  • #31
    Originally posted by Evan View Post
    Or overcontrol. Stomping on the rudder instead of "squeezing" it
    I don't think so, unless the overcontrol consisted on stomping the rudder towards the dead engine, and in that case I would not call it overcontrol.

    Can you map out a hypothetical sequence for falling under vmca? This was a pretty full flight so I assume Vr was in the neighborhood of 140kts and vmcg was around 110kts, and I assume the good engine (assuming engine failure here) was left at TO thrust (or at least MCT). Can you guesstimate vmca here?
    I can't

    --- 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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    • #32
      It's been raining in Miami for a whole week now!

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      • #33
        Originally posted by Gabriel View Post
        I don't think so, unless the overcontrol consisted on stomping the rudder towards the dead engine, and in that case I would not call it overcontrol.
        From what I've read, stomping on the rudder away from the dead engine can overpower the thrust assymetry and get you into serious trouble. That's a powerful rudder.

        I'm actually leaning towards #2 reverser deployment though. If those old target reversers are not fully stowed, aerodynamic forces can deploy them.

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        • #34
          Originally posted by Gabriel View Post
          I can't
          You might find this interesting:

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          • #35
            Originally posted by LH-B744 View Post
            'Knowledgeable' people don't necessarily have to be bad people. But envy is a bad attitude. And if you ask me, after four decades in Germany, this country is full of envy!
            "How is he able to.." or "Why does he know..." is one of the worst German problems.

            My opinion? Common sense does not only appear in the richest families or in the highest political circles. Sometimes I think just the opposite is the case...!

            PS: Only a few hours ago, there was a documentation on German TV, "Why Hitler lost the War.". I don't know if he was really stupid or insane. Fact is, he was not able to stay nine years at school, thus, he never graduated from school. But then, they showed how Adolf, who infact never was more (and due to education never could be more) than a "Gefreiter", treated "his" Generals. As if they were stupid or insane. Hitler must have thought that Washington is an unimportant village. Thus, Hitler declared war on the United States of America.

            In more than 1 case, "knowledgeable" is the contrast to the highest political circles.

            So let me get this straight, The Mexican pilots were watching a German television documentary about Adolf Hitler while they were taking-off and that's why they crashed? I didn't see that in any of the articles published over here. See the press here really is "fake" news. They never tell us the real poop!

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            • #36
              Originally posted by Evan View Post
              From what I've read, stomping on the rudder away from the dead engine can overpower the thrust assymetry and get you into serious trouble. That's a powerful rudder.
              Home base: "The stupid pilots messed up".

              If I flew a plane (or rode a bicycle) I would NEVER make a mistake nor crash.

              Official Audio for "Don't Stop Believin'" by JourneyListen to Journey: https://Journey.lnk.to/listenYDWatch more Journey videos: https://Journey.lnk.to/liste...
              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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              • #37
                Gabriel, have you read through this link yet?



                It may have nothing to do with this accident but it is very interesting in understanding how Vmca is calculated by engineers (looking to minimize the fin dimension while adhering to the FARs) and how they arrive at the speed publishd in the AFMs. I've always thought Vmca was a constant value, indifferent to weight, and this is true with wings level, but to accomplish design goals the AFM values are calculated using a slight bank angle of 3-5° to allow for minimum slideslip and thus lower drag, and with the bank angle weight does become a factor (lowering the Vmca as weight increases when banking toward the dead engine; increasing the Vmca when banking away from the dead engine. The other interesting thing is how with bank angle toward the dead engine in excess of 5°, speed must increase sharply to avoid fin stall. Read through it. I'd like to get the engineer's interpretation of this.

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                • #38
                  Originally posted by Evan View Post
                  Gabriel, have you read through this link yet?
                  Yes. I need more time to write an answer. I have some deadlines now so this will need to wait for a while.

                  --- 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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                  • #39
                    Here is a quick way to give a complete answer.
                    I 100% endorse the following video:
                    This video uses a Yaw Axis Simulator to demonstrate the effects of engine failure on multi-engine airplanes. It examines moments and centripetal force, defin...


                    It is much better than the "paper"you linked that seems to mix heading, yaw and sideslip.

                    --- 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


                    • #40
                      Originally posted by Gabriel View Post
                      Here is a quick way to give a complete answer.
                      Quick?

                      The dissertation poster links to an hour long video and calls it quick?

                      That being said, it does appear complete! (and you are consistent)

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

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                      • #41
                        But what about the Television show? Should they really have been watching T.V. while they are flying? Gee, we would get in trouble if we did that.

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                        • #42
                          Originally posted by 3WE View Post
                          Quick?

                          The dissertation poster links to an hour long video and calls it quick?

                          That being said, it does appear complete! (and you are consistent)

                          /friendly razz.
                          Well, it took me 20 seconds to post it here...

                          Answering a bit Evan's original request for comment...

                          There is a lot to discuss here, more or less like with stalls, or maneuver speed. Lots of misunderstandings, like that Vmc is not the speed below which the plane will uncontrollably spiral to the ground in a worst-case-asymmetric-thrust scenario. The plane can keep flying down to the point where the tail stalls, a wing stall, or you run out of aileron authority. And the speed at which that will happen is not strongly dependent on bank angle.

                          If you are at a given speed with an engine out and the other at a given power and have 100% of rudder applied and that's barely enough to keep zero sideslip, then the bank angle will dictate whether you turn in one direction, in the other direction, or don't turn, but you are equally safe (or at risk of) loosing control in either case, even if with the wings levels you cannot stop the rotatation (so we say that you are below the wings-level Vmc) or you have 3 deg bank into the good engine and you flight straight an level (in that case the same speed now would be the Vmc).

                          In other words, fly at the "zero sideslip Vmc" with therudder fully deflected, zero sideslip, and whatever bank angle is required to hold the heading (typically 3 deg). If you reduce the bak a little bit (for example to wings level) the plane will turn into the dead engine and there is nothing that you can do about it. Some say "that's because the wings-level Vmc is faster than the wing-down Vmc". I say "that's because you are turning for God's sake!!!" You see, if you have symmetric thrust and have the rudder that is required to keep zero sideslip (that is, neutral) and bank the plane, the plane will also "turn and there is nothing you can do about it".

                          The caveat about how Vmc is defined, and how the tails and rudders are designed based on that, is not so much that the engineers take advantage of the 5 degrees of bank that the FARs allow, but that they (we?) take advantage of the sideslip that is not even mentioned but indirectly accepted by the FAR. So they (we?) can reduce the tail and rudder and accept some sideslip that will add lateral lift to the tail beyond what rudder alone could do, and hence get a slower speed than the "zero sideslip Vmc", that in my opinion should be the definition of Vmc. Note also that there is no requirement for the plane to be able to climb an Vmc with one engine out. For transport category planes, the plane needs to be able to climb at V2 (which needs to be greater than Vmc), but that's a different story.

                          --- 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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                          • #43
                            Originally posted by Gabriel View Post
                            ...V subscript nitpicky this, V subscript nitpicky that, caveat, FAR...
                            Seems that engine failures cause instances of airspeed decay and, unfortunately, control loss with some frequency.

                            The late Richard Collins suggested that single engine planes had lower fatality rates from engine failures.
                            Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                            • #44
                              Originally posted by BoeingBobby View Post
                              Gee, we would get in trouble if we did that.
                              Liar - I've seen the pics- modern cockpits have 6? TVs and you ARE expected to watch them at least SOME of the time...right?
                              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                              • #45
                                Originally posted by 3WE View Post
                                Liar - I've seen the pics- modern cockpits have 6? TVs and you ARE expected to watch them at least SOME of the time...right?
                                Now that IS a good one!

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