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  1. #11
    Senior Member Lawrence's Avatar
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    Default Re: Interesting vid on Boeing crashes

    You would think raising the engines would greatly affect the laminar flow on the lifting surface of the wing(top)

    The tops of the engines would have a massive effect by delivering disturbed airflow and act as a brake

  2. #12
    tweakedgeek tweak'e's Avatar
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    Default Re: Interesting vid on Boeing crashes

    Quote Originally Posted by zqwerty View Post
    I would have thought that raising the engines with respect to the centre of gravity would have made the plane have more of a tendency to fly level rather than gain height and stall as compared to the original model. This can't be the reason that the MCAS was put on.

    Having the engines lower, as in the original model, would have put more of a turning moment around the centre of gravity and lifted the nose.
    i havn't bothered to watch the whole vid, but the bigger engines means they hang lower down, which tends to make the nose push up when power is applied. the MCAS is to automatically trim the aircraft to counteract that by pushing the nose down.

    the procedure for MCAS failure is the same as runaway trim, which is something they all train for. however the strange warning lights tends to cause confusion and makes pilots overlook the basics, which is they are having to counteract, with the stick, a runaway trim. part of the issue is many pilots do very few hours hand flying and tend to loose their feel for an aircraft.

    as mentioned above, there is multiple factors at play. a very poorly implemented system which made it extremely powerful, used a single sensor and no redundancy. this is now fixed by a software update.
    but there is also the human factor of pilots not having enough hand flying experience and not following the procedure.
    Tweak it till it breaks

  3. #13
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    Default Re: Interesting vid on Boeing crashes

    The LEAP engine nacelles are larger and had to be mounted slightly higher and further forward from the previous NG CFM56-7 engines to give the necessary ground clearance. This new location and larger size of nacelle cause the vortex flow off the nacelle body to produce lift at high AoA. As the nacelle is ahead of the C of G, this lift causes a slight pitch-up effect (ie a reducing stick force) which could lead the pilot to inadvertently pull the yoke further aft than intended bringing the aircraft closer towards the stall. This abnormal nose-up pitching is not allowable under 14CFR §25.203(a) "Stall characteristics". Several aerodynamic solutions were introduced such as revising the leading edge stall strip and modifying the leading edge vortilons but they were insufficient to pass regulation. MCAS was therefore introduced to give an automatic nose down stabilizer input during elevated AoA when flaps are up.
    http://www.b737.org.uk/mcas.htm

  4. #14
    VoidMaster
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    Default Re: Interesting vid on Boeing crashes

    Ugh, seems really klugey to me, something I have learned is to be avoided when designing electronic circuitry and probably everything else as well.

    [A kludge or kluge (/klʌdʒ, kluːdʒ/) is a workaround or quick-and-dirty solution that is clumsy, inelegant, inefficient, difficult to extend and hard to maintain. This term is used in diverse fields such as computer science, aerospace engineering, Internet slang, evolutionary neuroscience, and government.]

    It smells to me of "upper-level" management/middle-management pushing through changes against the advice of engineers etc and then running for cover when things go bad like the 'O' Rings on the space shuttle debacle.
    Last edited by zqwerty; 19-04-2019 at 01:11 PM.
    It's not the least charm of a theory that it is refutable. The hundred-times-refuted theory of "free will" owes its persistence to this charm alone; some one is always appearing who feels himself strong enough to refute it - Friedrich Nietzsche

  5. #15
    Soaring like a chicken prefect's Avatar
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    Default Re: Interesting vid on Boeing crashes

    I think the 737 sits abnormally low you can see on the latest non Max versions the engine has a squashed bottom. It looks like the 737 design had run to the end of its life and should have been replaced by a new 797 design. Although people have incredibly short memories about this stuff an example when Toyotas were getting stuck at full throttle it was soon forgotten. De hav Comet was still produced after some horror crashes
    Its amazing how Potatoes give us chips,fries and Vodka.

    Get your s*** together every other vegetable.

  6. #16
    Wrinkly Member! B.M.'s Avatar
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    Default Re: Interesting vid on Boeing crashes

    I read the local aviators opinions and respect them.

    My view is that the “You Beaut” “Fly by Wire” technology has a lot to answer for.

    A friend who flew 777’s for Qantas once told me that he could fly a 777 upside down if he had to, but an Airbus would refuse, saying he was “operating outside of parameters”.

    Times Change.

    However, talking of the engine placement, I can “Vaguely” remember an incident years ago when some hijackers wanted to go somewhere and wouldn’t listen to the pilot who said he didn’t have any where near enough fuel. The outcome was that he wound up ditching in the sea.

    I can’t recall the outcome or finer details, but I do recall there was pressure within the industry to have the engines mounted above the wings because his landing was perfect until the engines hit the water.

    Someone reming me of the details.

    However, years ago we had the legendary Chesley Sullenberger land a Airbus A320 in the Hudson River with no casualties.

    Naturally I had to have my friend who flew 777’s on about this, and he responded: That flying would be some of the best ever, and will go down in history. I tip my hat to him. But I bet he couldn’t do it again.

    We’ll never know.
    Global Warming is Mann made.
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  7. #17
    Senior Member fred_fish's Avatar
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    Default Re: Interesting vid on Boeing crashes

    Quote Originally Posted by B.M. View Post
    Someone reming me of the details.
    https://www.youtube.com/watch?v=WE2Yn0cipTY
    I feel a hot wind on my shoulder
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  8. #18
    Wrinkly Member! B.M.'s Avatar
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    Default Re: Interesting vid on Boeing crashes

    Quote Originally Posted by fred_fish View Post
    That's it, thanks Fred,
    Global Warming is Mann made.
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  9. #19
    Senior Member piroska's Avatar
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    Default Re: Interesting vid on Boeing crashes

    Quote Originally Posted by B.M. View Post
    I can “Vaguely” remember an incident years ago when some hijackers wanted to go somewhere and wouldn’t listen to the pilot who said he didn’t have any where near enough fuel. The outcome was that he wound up ditching in the sea.
    , but I do recall there was pressure within the industry to have the engines mounted above the wings because his landing was perfect until the engines hit the water.

    Wrong.
    Landing on the sea is difficult because it's not flat, there are waves and such.
    He was tilted too much and the wing touched and the plane flipped and came apart. Amazingly a few did survive.

    https://en.wikipedia.org/wiki/Ethiop...nes_Flight_961

    You can watch the landing if you want (Crashlanding)
    Ex-pctek

  10. #20
    Soaring like a chicken prefect's Avatar
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    Default Re: Interesting vid on Boeing crashes

    Quote Originally Posted by piroska View Post
    Wrong.
    Landing on the sea is difficult because it's not flat, there are waves and such.
    He was tilted too much and the wing touched and the plane flipped and came apart. Amazingly a few did survive.

    https://en.wikipedia.org/wiki/Ethiop...nes_Flight_961

    You can watch the landing if you want (Crashlanding)
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