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Thread: AP: Cubana Crashes on Takeoff From Havana

  1. #41
    Senior Member BoeingBobby's Avatar
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    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.

  2. #42
    Senior Member Gabriel's Avatar
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    Quote 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 ---

  3. #43
    Senior Member 3WE's Avatar
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    Quote 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.

  4. #44
    Senior Member 3WE's Avatar
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    Quote 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.

  5. #45
    Senior Member BoeingBobby's Avatar
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    Quote 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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