J-20 5th Gen Fighter Thread V

Discussion in 'Air Force' started by Deino, Apr 17, 2015.

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  1. zaphd
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    zaphd New Member
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    It's not only about T:W ratio. That argument would hold if you had only lift induced drag, but at supersonic speeds you have stuff like wave drag, which doesn't depend on weight. It's a highly unlinear situation.
     
  2. latenlazy
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    latenlazy Colonel

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    Yes, but if the plane is designed for supercruise, then induced drag isn't the limiting factor.
     
  3. Hyperwarp
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    Hyperwarp Captain

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    Its not just about the T/W ratio. It depends on how draggy the J-20 design is. An example would be YF-22 vs YF-23. Despite the same engines the YF-23 was much better at supercrusing.

    Lot depends on the dry thrust of the engine. F119 officially can produce at least 155kN in full afterburner. Unofficially it is even higher. Dry thrust is lower but I've heard rumors that the F119 can produce as much thrust as a AL-31F in full afterburner. About 115kN - 120 kN dry vs the 122kN of the AL-31F in full AB. In-contrast the 117S can produce only 86kN max dry thrust and its not clear how long it can sustain that. We don't know how much max dry thrust the current Salut engines can produce.

    The EF, Rafale, Gripen can supercruise at around Mach 1.2 with 4 AAM. EF can supercruise with 2x ASRAAM + 4x AMRAAM and one centerline drop tank. But remember these are much smaller planes and shorter range. We don't know the exact supercruise values for the Su-35S either. How much and how long can is supercruise with 8x AAM hanging from the pylon and that assuming it actually can.
     
  4. latenlazy
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    latenlazy Colonel

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    Again, if the J-20 is designed for supercruise, then the limiting factor isn't induced drag, but T:W ratio, which changes with fuel load. In so far as we care about thrust, it is through how thrust acts on mass.
     
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  5. Hyperwarp
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    Hyperwarp Captain

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    Lets do a crude, unscientific calculation. Lets use the F-22 with F119 and J-20 with 117S. I am using the 117S because we know the dry thrust.

    Assuming max dry thrust of the F119 to 120kN (probably higher) and max supercruise of Mach 1.7-1.8. The max dry thrust of the 117S is 86kN.

    Now the BIG IFs! Assuming drag is irrelevant and the F-22 and J-20 weighs the same, then the theoretical max supercruise for the J-20 will be around Mach 1.2 - 1.3 at most. But we do not know the weight of the J-20. J-20 is larger than the F-22.
     
  6. taxiya
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    taxiya Major
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    Hi b787, as you always do, again this time you stretched my post to fit your thought, or inserted your imagination to my mouth.

    Did I say anything (agree or disagree) about that CNN article? No, I did not. I was purely commenting about CNN's credibility and ethics regardless their words based on my past experience. If the same words were said by somebody else, I will give more considerations. But from CNN, No. It's just that.
     
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  7. shen
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    shen Senior Member

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    Don't know what you are talking about. Narrow waist of area ruled aircraft is not to compensate for the bugle of intakes. Narrow waist is compensating for the wings, which is always the widest part. Intake bulges is in fact often used as a component of area ruling. Compare the original F-102 design (not the production model) vs the fully area ruled F-106.

    F-22 is not a great example of area ruled airframe either. F-35 is a much better example, necessary due to lower thrust to weight ratio, the same reason J-20
     
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  8. taxiya
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    taxiya Major
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    Latenlazy asked "cross section", and you answered "length". If I ask you color, you will tell me it is cold?

    Please stop your usual practice of distraction, changing subject, diversion, twisting other's meaning, goal-post moving etc. etc. It does not look smart on you and it is a torture of the rest of us. May all Gods of all human-beings have mercy on all of us including you.
     
  9. Air Force Brat
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    Air Force Brat Brigadier

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    You're spot on here son, and I am in 150% agreement with you, and furthermore, I still do NOT believe China is going to thow away money to buy SU-35s, when they have NO real interest in OVT, and they build better Flankers anyway??? just my honest opinion?? if I'm wrong about the SU-35s I will issue a public apology and retraction. Brat
     
  10. vesicles
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    vesicles Major

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    Amen to that! The Chinese officials have not said a single thing about it. I will accept it when I see the Su-35 in PLAAF color.

    I will sign that apology form with Brat if that ever happens... I am totally fine with it since I have been wrong plenty times in my life. In fact, I have been wrong way more than when I've been right.

    Even IF the PLAAF will buy the Su-35 in the future, I still do not think it is the right thing to do. I still maintain that they should tough it out on their own. It's not about pride or ego. It's about throwing away the crutches and be on your own.
     
    #3410 vesicles, Nov 3, 2016
    Last edited: Nov 3, 2016
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