J-20 5th Gen Fighter Thread VI

Discussion in 'Air Force' started by siegecrossbow, Sep 4, 2017.

  1. Biscuits
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    Biscuits Junior Member
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    Well, that’s a different type of mission. If those targets present themselves, then J-20 can seal club them quickly. But that scenario would likely only come up later on when a hypothetical enemy’s attack has already been blunted.

    Hunting down stealth fighters, stealth bombers and high end 4.5 gen would still be the main activity.
     
  2. by78
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    More high-resolution images.

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  5. longmarch
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    longmarch Junior Member
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    I wish Zhuhai this kind of good weather, but never gonna happen :(
     
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  7. siegecrossbow
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  8. Inst
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    Inst Senior Member

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    Lowest thrust figures for the J-20 come from AL-31F, i.e, just the stock AL-31F at around 250kN combined. The WS-10 figures range from 132 to 140kN, both of which are relatively low.

    If we go by best case to best case figures, it's 197kN vs 140kN, which gets us to roughly 40% thrust boost, which is still a lot.
     
  9. manqiangrexue
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    manqiangrexue Captain

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    Yeah, I know how you got those numbers; I'm saying they're not correct. Reread my comment you quoted and you'll see why it's wrong to use stock old/early AL-31F or WS-10X numbers on J-20. To think that J-20 might be powered by a 125kN AL-31F when J-10 uses a 137kN AL-31FN3 is just... not... smart. WS-10X figures might have been usable if it weren't for the AL-31FM2 providing 145kN thrust with the Chinese unlikely to downgrade the engine for its premier fighter just for indigenization (especially at a time when relations with Russia are very warm). That's why I said that the lowest realistic thrust for J-20A is 145kNx2 but it could be a bit higher.

    I have seen some unreliable sources talk about a 197kN figure for WS-15; I have also seen some talk about a 220kN figure. They don't make sense to me. Most sources seem to center on 180kN and have previously (in the comment you quoted) outlined why it doesn't make sense to me for them to keep the engine still in prototype phase trying to get numbers that high rather that release it at 180kN (or even 170kN if they're having trouble) and open the bottleneck for J-20B production.

    Could you post the sources you have for 197kN so we can better understand why you seem to have such high regard for a number that the rest of us generally view as a fanboy rumor?
     
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  10. Air Force Brat
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    In the first photo, he is 'standing" on the left rudder, note the high degree of differential in rudder deflection, of the left and right rudder! This gives a clue into the highly sophisticated FCS of the J-20. The high degree of deflection on the left rudder creates a great deal more drag than the more lightly deflected right rudder, increasing drag on the left rudder and pulling the nose through to the left...

    and yes, if he was rolling to the right, the right rudder would then have a much higher degree of deflection than the left aileron.

    So this is a "very aggressive" maneuver at a relatively low airspeed, you very seldom see such large control deflections on jet aircraft even during heavy maneuvering. I would suggest he is likely around 250Kts, bleeding to around 200Kts as he makes a relatively agreesive pitch up, then begins the roll, which as you can see is very agressive, the right aileron is deflected downward, increasing lift (and drag) on the right wing. The left aileron is deflected upward, decreasing lift (and drag) on the left wing...

    Hence the heavy rudder deflection to overcome "adverse aileron yaw", so this aileron deflection, creates a very strong yawing moment to the right, so heay aileron deflection is necessary to overcome adverse aileron yaw.

    The greater rudder deflection on the "boot side rudder" is also outboard of the center line, effectively increasing its aerodynamic leverage with a larger "moment arm".
     
    #5960 Air Force Brat, Oct 20, 2019
    Last edited: Oct 20, 2019
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