TWR and Wing Loading issues with the JF-17

Discussion in 'Air Force' started by Mohsin77, Mar 7, 2019.

  1. Mohsin77
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    Mohsin77 Junior Member
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    Whenever we hear a PAF official speaking about the JF-17, they usually compare it to the Viper. Leaving aside avionics, the hopes of all pilots in the PAF is that the Thunder will one day match the maneuverability of the Viper, as dictated by the culture within the PAF pilot community, which still places a special emphasis on dogfighting. They realize BVR combat is necessary, but the CCS in Sargodah will never de-emphasize WVR, I think, unlike NATO.

    Regarding this ambition/hope, I have some concerns regarding the Wing Loading and Thrust/Weight ratio of the JF-17. I made a table comparing the values of the Viper-C Block 50 with the Block I. Obviously the Block III's values are incomplete, but let's use Block I to see what the delta is currently. Please see attached:

    viper vs jf17.PNG

    (if there are any errors in these calcs please let me know)

    The publicly available stats for the Block I, place it far behind the Viper-C in TWR and slightly behind in Wing Loading. The question is, will the Block III be able to close this gap much?

    The Block III's WS-13E has been estimated as having 22.5K lb max thrust, and is reported to be lighter, which should improve the TWR. Also, there are reports of more composite materials being used in the airframe, which will also reduce the weight, thus potentially improving TWR and Wing Loading (provided no other weight gains.)

    The wing area on the Block II has already increased slightly, with the F/A-18E style enlarged LEX, which will help in this regard. It is possible more airframe changes (which are rumoured) have been made for the Block III, but at this point, I doubt the shape will change much.

    What this means, basically, is that the simplest way to get both the TWR and Wing Loading to improve for the Block III, is with a substantial weight reduction, via composites and replacing mechanical components with electronics (e.g. full FBW). All else being equal, the required reduction in weight will need to be 3,000 lbs in order to get into the Viper's regime, which is the oft-stated ambition of the PAF. That means almost 20% of the Block I's empty weight has to be shed.

    But is that even possible at this stage?
     
  2. siegecrossbow
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    siegecrossbow Brigadier
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    My understanding is that Block III will primarily improve the radar (changing to AESA) and there is no reliable information on whether it will be re-engined with WS-13E. Typically, an improvement in avionics corresponds to an increase in weight even with use of composites, so I don't think there will be a significant increase in the thrust to weight department. However, I think superior avionics mean more for the potency of a fighter than agility or maneuverability, especially in this day and age.
     
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  3. Mohsin77
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    Mohsin77 Junior Member
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    Hmm, that's disappointing. I was really hoping the Block III would end up matching the Viper's agility.

    But yes, avionics must be given priority these days...
     
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  4. gelgoog
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    gelgoog Senior Member
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    Don't expect it to reach similar performance parameters. You have to see the engine has a lot lower thrust. You have to remember the MiG-29 was the competitor to the F-16 in that era and it had to use two of those engines to do it. While this could be kind of mitigated with a good airframe design the Chinese aircraft industry was simply not there yet at that time. The closest analog I could make in the Western sphere would be the Grippen (JAS 39C) which has a single F-18 engine. But the Grippen has a much more sophisticated airframe. Compare that with the JF-17.

    The Grippen C has more wing area and agility, a similar empty weight, but much more maximum takeoff weight.

    To make something with a similar powered engine as the F-16 you would be better off just buying the J-10. The JF-17 is in a different weight category altogether. Depending on the progress of engines in that weight class in China and Russia it could be you would be better off making a larger aircraft which can use a AL-31/WS-10 class engine in the next iteration. The Swedes went with the Super Hornet engine in the Grippen E which is now entering production but I can't think of an engine with similar performance parameters in China or Russia right now that you could simply drop onto the JF-17. So I think Pakistan should aim for something either uses a single AL-31/WS-10 or its successors for its next aircraft.

    To make something really competitive with the aircraft in that class entering production right now you would need to use something like a single AL-41F or perhaps the WS-15. The engine alone needs to have a thrust-to-weight ratio of 9:1 or better.
     
    #4 gelgoog, Mar 7, 2019
    Last edited: Mar 7, 2019
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  5. Mohsin77
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    Mohsin77 Junior Member
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    I was banking on composites + WS-13E to solve this problem. Anything else would be a developmental nightmare. And we need these jets in the air ASAP, as you can see from the news. And I totally agree re: the Grippen, I really like that jet. I'm glad the Indians went for the Rafale instead.
     
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  6. gelgoog
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    gelgoog Senior Member
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    If the problem is having something ASAP I think the best option is to simply continue manufacturing what you already have the production pipeline setup to build. Things like the radar upgrades also seem to be a low hanging target you could reach. These could significantly increase the combat capability especially with more modern missiles and some sort of helmet cuing system. That would mitigate the disadvantage in terms of aerobatic performance. Materials and engine improvements would both take longer and require different suppliers for major components. Depending on how long Block III would take I would probably build more Block II aircraft if those could be built faster. You can't exactly easily increase the wing area or engine thrust. While there are upgrades for the RD-33 family engines like the RD-33MK those should only provide like an 8% performance increase at best. I don't know how many of those have already been incorporated in the RD-93. If they already incorporated most of the improvements then I can't think of any existing program that could be used for this.

    So if Pakistan is really concerned in increasing its combat aircraft capabilities in a short timeframe with a reasonable budget, I think they should just build whichever JF-17s they can build right now and possibly order J-10C aircraft from China. This has a better upgrade path in terms of engines and it also has more payload capability so it can use more advanced weapons.
     
    #6 gelgoog, Mar 7, 2019
    Last edited: Mar 7, 2019
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  7. Mohsin77
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    Mohsin77 Junior Member
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    Yes I agree, in fact the PAF ordered extra Block IIs as it is waiting for Block IIIs. Integrating HOBS/HMDS will mitigate the WVR performance as well.
     
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  8. TerraN_EmpirE
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    TerraN_EmpirE Tyrant King

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    This is a myth. Take another look at the Grippen, Rafale, Typhoon, F35 The latest off the line are all very maneuverable machines. The training is also working to maintain DACT.
    However JF17 as the other have pointed out is limited by it's off the shelf power plan and limits of materials.
    if it was that easy it would have already been done.
    F16 is a wonder of aviation as @gelgoog points out Russian Aviation couldn't match it would put going to a twin engine design. Even then the product never matched F16 in production numbers. Despite being now 40 years old an currently out of active production, it's still getting attention for new buys. India before this recent conflict was looking at seriously buying and production of a variant for its air forces the F21.
    JF17 was never meant to match the F16 "Viper" it was to be a new light fighter to phase out the residual 3rd gens like the F7 and Mirage III.
    About the only fighter I think could match F16 in what it does are either another F16, a up to date Mig29, FA18, F35 Or J10.
     
  9. Brumby
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    Sorry guys this may be digressing a bit from the topic. Why isn't Pakistan buying J-10C?
     
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  10. gelgoog
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    gelgoog Senior Member
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    I am not an expert on that. But IIRC the Pakistani government is trying to reduce the number of combat platforms to keep costs down. It also wants to build its own equipment. Probably to increase self-reliance and also to reduce costs. That is the likely reason why the J-10 has not been purchased so far despite the Chinese trying to sell it more than once.
     
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