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Thread: What is the mechanism whereby a symmetrical airfoil provides lift? Is it wing inciden

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    Default What is the mechanism whereby a symmetrical airfoil provides lift? Is it wing inciden

    What is the mechanism whereby a symmetrical airfoil provides lift? Is it wing incidence, or are other factors involved?

    "Fly Southern, Y'all"

    bushp04

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    A barn door is symmetrical, and can generate lift. You might think of it as deflecting the oncoming air downward, which it does (though there's a little more to it). Pretty much anything like that, so long as it has a sufficiently positive angle of attack will generate lift (think paper airplane). You might also want to see this Wiki article. You might also find this article helpful.

    Wing incidence is merely the angle of the wing with the fuselage and generates no lift at all, by itself. Angle of attack, the angle of the wing with respect to the relative airflow is the lift generator, whether the wing is symmetrical or not, but cambered wings are more efficient at generating lift than the symmetrical ones.

    A wing can generate lift in any pitch attitude (relative to the earth), even straight down. You might look in the Real Aviation Tutorials & FAQs section below at the Glossary (there's more good info there too).
    Last edited by lnuss; 12-17-2018 at 09:09 PM.

    Larry N.

    As Skylab would say:
    Remember: Aviation is NOT an exact Science!

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    Hey Larry, please forgive the long delay in response. I appreciate your response. It had been so long since your reply that I had to do reverse-research to help myself remember how I had come to develop the question in my initial post.

    Take care,
    Len

    "Fly Southern, Y'all"

    bushp04

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    A wing is curved and angled. But what provides most of the lift is the profile in cross section. The wing is thick at the front, and becomes thinner towards the back. That is what provides most of the lift.
    The curve (camber) of the wing also plays a big role.
    The effect of these two is that the air going past underneath the wing travels a smaller distance then that above the wing.
    The air "splits" at the front of the wing. Some pasing over it, some pssing under it. But, they are at the end of the wing agin at the same time.
    As the air over the top travels a greater distance then the air underneath, but in the same amount of time, the air over the top travels faster. (and sort of gets 'stretched out').
    And air travelling faster is at a lower pressure. (or in other words, air that is 'stretched out' has the molecules further apart, meaning lower pressure.)
    lower pressure above the wing then underneath it meant: The wing gets sucked up.

    It's a small difference in pressure, but this applies to every square centimeter of wing surface. So in total the suction sucking the wings up is very strong. (And the faster you fly, the stronger the wings are sucked upwards.
    The wings are attached to the aircraft body, so that then gets pulled up by the wings.

    By making the angle (incidence) more or less you can adjust the amount of lift only slightly.

    A paper aircraft also has this curve ( or camber). (It can be altered by running edge of wing between two fingernails).
    And the fold at the 'leading" edge makes the wing thick at the front and thin near the back where it's just one sheet thick. Which greates the same sort of wing cross section as a real plane, thiker at the front, and slowl becoming thinner towards the back.

    Anything will lift off if you add enough thrust. Even a barn door or a brick. (think hurricane). But calling that flying is not really correct. It's definitely not controlled flight.

    Look up principles of aerodynamics and fixed wing aircraft. Plenty of good books and internet articles about the subject. With images of for example cross sections of various wings that make things much more clear. Also images there of the effects that lift, thrust, and gravity working at the same time have on a flying fixed wing aircraft.
    Last edited by il88pp; 06-03-2019 at 12:35 PM.

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    Quote Originally Posted by bushp04 View Post
    Hey Larry, please forgive the long delay in response. I appreciate your response. It had been so long since your reply that I had to do reverse-research to help myself remember how I had come to develop the question in my initial post.

    Take care,
    Len
    You're welcome, Len. Hope it helps.

    il88pp, you're providing a generic description that often works, but Len was talking about a symmetrical airfoil which doesn't have the shape you're talking about (neither does a barn door, which can be flown given the right setup). You might check out the references in my earlier post.

    Larry N.

    As Skylab would say:
    Remember: Aviation is NOT an exact Science!

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    Larry's links are great references. NASA also has a good site on theories of lift, including dispelling some of the common ones that aren't correct, or over simplified. They also have Java Applet that you can play with.

    https://www.grc.nasa.gov/WWW/K-12/airplane/lift2.html

    https://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html

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    In the Flight Simulator I can make a BRICK fly at supersonic speeds and then land at 5 kts (with a 5 kt head wind). Not 'real' you might say? (you are RIGHT...so now you get it?).
    Chuck B
    Napamule
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    Hi Loki, Napamule, and il88pp please excuse the long delay in response to your posts. Before June, I thought I was headed back this way, but some very unfortunate circumstances prevented it (the biggest of which I lost my best buddy (my age) to a sudden and unexpected death.

    Now, I've got to put NASA's theories of lift, etc., behind me and get back to simming to get my mind straightened out. I'll start a new thread about that subject. Meanwhile, thanks to you all.
    Len
    bushp04

    P.S. Loki, I did read the NASA links--very informative--before getting knocked back to the basics.
    Last edited by bushp04; 07-12-2019 at 09:52 AM. Reason: Add notes

    "Fly Southern, Y'all"

    bushp04

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    Welcome back, Len. Sorry to hear of the loss of your friend. I just lost my best friend recently, too, so I feel with you.

    Larry N.

    As Skylab would say:
    Remember: Aviation is NOT an exact Science!

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    Anything will lift off if you add enough thrust. Even a barn door or a brick. (think hurricane). But calling that flying is not really correct. It's definitely not controlled flight.
    Just think F-4 Phantom II. Put enough thrust...
    It's (relatively) controlled flight. Usually.
    Think about the story of Randy "Duke" Cunningham and his RIO trying to egress N. Viet Nam after getting either a very close call or a hit by a SAM. The plane, on fire from the SAM strike, would roll inverted, he would become very religious, he'd get the plane upright again and become a fighter pilot again, the plane would then roll inverted, lather, rinse, repeat.
    He made it to the Gulf of Tonkin before the fire aboard finally got too close and the RIO ejected them both before he got cooked.
    In any event, "controlled flight", mostly

    He went on to found the Top Gun, or Fighter Weapons School. Glad he survived!

    So: you put enough thrust behind a brick, you've got the Phantom

    Pat☺

    Had a thought...then there was the smell of something burning, and sparks, and then a big fire, and then the lights went out! I guess I better not do that again!
    Sgt, USMC, 10 years proud service, Inactive reserve now

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