China's transport, tanker & heavy lift aircraft

Discussion in 'Air Force' started by Totoro, Sep 10, 2005.

  1. Tirdent
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    Tirdent Junior Member
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    The exact airfoil sections are not known (though it would probably be possible to find out for the Il-76 with some digging...), but we do know one (the Y-20) has modern supercritical airfoils while the other (Il-76) does not.

    Wings with supercritical airfoil sections have a characteristic appearance from certain angles if you know what to look for*. It became obvious that the Y-20 has supercritical airfoils based on photos pretty early on, whereas the Il-76 certainly does not (quite apart from anything else its design simply pre-dates the introduction of this technology - I think the first Soviet aircraft was the An-124).

    * Supercritical airfoils reduce drag due to the formation of shocks on the upper surface of the wing at transonic speed. Air flows faster over the top of the wing than the aircraft's forward speed in order to generate lift, so in Mach 0.8 cruise the local flow velocity will be >Mach 1.0. In fact, in some STOL aircraft with elaborate slotted flap systems it can be comfortably supersonic during final approach to landing, which may be a source of considerable community noise!

    Conventional airfoil shapes generally produce an extremely pronounced "suction peak" (overspeed) not far aft of the leading edge, which (at transonic speed) terminates with a strong shock that causes a lot of drag. A supercritical airfoil spreads its suction out further aft along the wing chord (they are sometimes called "back loaded" for this reason) and has a weaker terminating shock as a result. This is done by having the site of maximum airfoil thickness further to the rear which creates a marked concave "dent" on the lower surface of the wing that is pretty obvious on some Y-20 photos.

    https://www.sinodefenceforum.com/ch...heavy-lift-aircraft.t197/page-326#post-490381

    https://www.sinodefenceforum.com/ch...heavy-lift-aircraft.t197/page-327#post-490383

    Trivia: a very similar approach is used in laminar airfoils for subsonic aircraft, the first of which famously was the P-51. However, mass production surface finish in WWII was nowhere near good enough to take advantage of laminar flow, in fact the performance benefit in the Mustang came from an unintentional "supercritical effect" at high speeds.
     
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  2. jobjed
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    jobjed Captain

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    Ohhh, you're talking about the Il-76, I thought you were talking about the C-17, where ambiguity of relative modernity exists.
     
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  3. Interstellar
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    Interstellar Junior Member
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    The new tanker made its first flight today.
     
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  4. Deino
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    Deino Lieutenant General
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    Congrats ... and you know me: I want images !!!! :)
     
  5. by78
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    by78 Brigadier

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    Here they are... :)

    (1500 x 629)
    [​IMG]

    (1500 x 629)
    [​IMG]

    (1500 x 623)
    [​IMG]
     
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  6. SinoSoldier
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    SinoSoldier Colonel

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    Unfortunately, they are Photoshopped.
     
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  7. by78
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    by78 Brigadier

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    LOL! You are right!! Well, this is embarrassing, but I can't edit the post with a warning now. :oops:
     
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  8. SinoSoldier
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    SinoSoldier Colonel

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    If the rumors are true however we wouldn't have to wait long before blurry pictures of a yellow-skinned Y-20 pops up.
     
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  9. asif iqbal
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    asif iqbal Brigadier

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    The thing is already out there for goodness sake why do these Chinese fanboys insist on doing photoshop? As if it’s like a dream come true ?

    I mean look at the refuelling pod at the tail seriously someone is meant to believe this ? Its done in paint by a 3 year old
     
  10. Bltizo
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    Bltizo Moderator
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    To irritate people like us :)
     
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