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What is up with the J-31?

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  • SteveDaPirate
    replied
    Originally posted by Versus View Post
    When you are having an unlimited supply of fuel, you don't need to be efficient. True statement that eastern engines are crude and primitive, but they fit into the tactics of large numbers to counter sophisticated opponent.
    When I think of unlimited fuel I tend to think of Western doctrine more than Eastern. Unlimited fuel requires aerial refueling assets, and the East just doesn't seem interested in buying very many. The Chinese have ~20 Xian H-6Us, and the Russians operate only ~20 Ilyushin Il-78s along with some buddy tanking with fighters.

    Meanwhile, the USAF alone has north of 500 KC-135s, and a few KC-10s and still contracts with private companies to provide refueling services as well. The USMC has ~80 KC-130s, and both the USMC and Navy use fighter buddy tanking, and refueling kits with V-22s.

    If anything, I would expect Eastern engine design to focus on efficiency even over performance, since they seem to like to operate their aircraft on internal fuel rather than gassing them up en-route to a target.

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  • Skywatcher
    replied
    Originally posted by citanon View Post
    The J31 is an example of trying to copy the F35 and failing because you can't make the engine. The impact on combat load and internal fuel must be severe. The Chinese are probably developing it as a cheap stealthish option for local air defense and light attack. It's a defensive weapon not an offensive one.

    Also, it's in a much earlier state of development than the J20. Notice the absence of apertures for anything useful.
    The sole flying J-31 is the production version what the X-35 and YF-22 are to the Lightning II and Raptor (I don't even know how functional the avionics are)

    Well, the Chinese want something that's more optimized for A2A, so that makes it lighter than the F-35, since the fuselage isn't so voluminous. Though I expect that its normal takeoff weight and MOTW to drastically expand once mission creep/future upgrades come up.

    The R-33s are a temporary measure (apparently the production WS-13Es have 10+ tons of thrust each).

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  • Versus
    replied
    When you are having an unlimited supply of fuel, you don't need to be efficient. True statement that eastern engines are crude and primitive, but they fit into the tactics of large numbers to counter sophisticated opponent. Engine is at least five times more harder to construct than the aircraft itself. They are super complicated devices.

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  • gunnut
    replied
    Originally posted by Stitch View Post
    Yeah, but that's SUPPOSED to be a mid-range engine; the Navy specified back in the '70's when the F-404 was being developed that they wanted a deliberately conservative design for the F-18 because reliability & serviceability are at the top of their list for aircraft engines, not all-out performance & thrust. The F-18 (both the first-gen and the Super) have always been a bit under-powered compared to other front-line fighters, but this was a deliberate strategy to emphasize reliability (very important when you are hundreds of miles from your floating airfield). The F-414 was developed, in part, to remedy the F-404's shortcomings (lack of thrust & SFC).

    And the next-gen Gripen will be using the F414.
    Maybe the Chinese are going with a conservative design also. Decrease power output to improve the reliability of their not-so-reliable engines.

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  • Stitch
    replied
    Originally posted by gunnut View Post
    By the way, 19000 lb class is without afterburner, right? That's still pretty impressive. Gripen's F-404 engine only produces 12000 lb thrust dry yet it's able to supercruise with external stores.
    Yeah, but that's SUPPOSED to be a mid-range engine; the Navy specified back in the '70's when the F-404 was being developed that they wanted a deliberately conservative design for the F-18 because reliability & serviceability are at the top of their list for aircraft engines, not all-out performance & thrust. The F-18 (both the first-gen and the Super) have always been a bit under-powered compared to other front-line fighters, but this was a deliberate strategy to emphasize reliability (very important when you are hundreds of miles from your floating airfield). The F-414 was developed, in part, to remedy the F-404's shortcomings (lack of thrust & SFC).

    And the next-gen Gripen will be using the F414.

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  • SteveDaPirate
    replied
    Originally posted by gunnut View Post
    Have we figured out what powers the J-20 yet?
    Apparently it is currently powered by the WS-10G which is aiming to deliver 35,000lbs of vectored thrust, but apparently has issues with developing thrust quickly, and with reliability, as during tests in 2010 it only lasted for about 30 flight hours. In April of 2015, the J-11D made its first flight with a new version of the WS-10 that featured improved reliability with thrust in the 26,000lbs region.

    It is supposed to be replaced by the WS-15 currently in development that is aiming to achieve 40,000lbs of thrust.

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  • gunnut
    replied
    Originally posted by Stitch View Post
    The posting on Chinese websites of possible performance data for the Shenyang Aircraft Corporation (SAC) FC-31 fifth-generation fighter indicates it could pose a commercial threat to Western and Russian fighter manufacturers.

    http://www.janes.com/article/54677/s...-leaked-online

    So, the engines are only in the "19,000 lbs. class"? That's about half the thrust of the F-119, and less than half the thrust of the F-135; no wonder it has two of them! They sound like they're roughly equivalent to a '60's-era P&W TF-30 low bypass-ratio turbofan.
    Engine has always been a problem for the Chinese, be it automotive engine or aviation engine. Can't make one that rivals Japan or the West. By the way, 19000 lb class is without afterburner, right? That's still pretty impressive. Gripen's F-404 engine only produces 12000 lb thrust dry yet it's able to supercruise with external stores.

    Have we figured out what powers the J-20 yet?

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  • citanon
    replied
    Originally posted by Stitch View Post
    The posting on Chinese websites of possible performance data for the Shenyang Aircraft Corporation (SAC) FC-31 fifth-generation fighter indicates it could pose a commercial threat to Western and Russian fighter manufacturers.

    http://www.janes.com/article/54677/s...-leaked-online

    So, the engines are only in the "19,000 lbs. class"? That's about half the thrust of the F-119, and less than half the thrust of the F-135; no wonder it has two of them! They sound like they're roughly equivalent to a '60's-era General Electric TF-30 low bypass-ratio turbofan.
    The J31 is an example of trying to copy the F35 and failing because you can't make the engine. The impact on combat load and internal fuel must be severe. The Chinese are probably developing it as a cheap stealthish option for local air defense and light attack. It's a defensive weapon not an offensive one.

    Also, it's in a much earlier state of development than the J20. Notice the absence of apertures for anything useful.

    Leave a comment:


  • Stitch
    replied
    Shenyang FC-31 fighter performance 'leaked' online

    The posting on Chinese websites of possible performance data for the Shenyang Aircraft Corporation (SAC) FC-31 fifth-generation fighter indicates it could pose a commercial threat to Western and Russian fighter manufacturers.

    http://www.janes.com/article/54677/s...-leaked-online

    So, the engines are only in the "19,000 lbs. class"? That's about half the thrust of the F-119, and less than half the thrust of the F-135; no wonder it has two of them! They sound like they're roughly equivalent to a '60's-era P&W TF-30 low bypass-ratio turbofan.
    Last edited by Stitch; 22 Sep 15,, 20:09. Reason: Wrong manufacturer!

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  • SteveDaPirate
    replied
    Originally posted by Stitch View Post
    Along those lines, my understanding is that the exhaust plume from the J-58's on the SR-71 actually reflected radar, and had a radar signature all of their own; I'm guessing the RCS of the SR-71, due to the rudimentary stealth measures it incorporated, was probably about the same as the RCS from it's exhaust plume(s).
    According to SENIOR CROWN SR-71

    Although most news reports characterize the SR-71 aircraft as `radar evading', in point of fact, however, the SR-71 was one of the largest radar targets ever detected on the FAA's long-range radars. The FAA was able to track it at ranges of several hundred miles. The explanation offered was that the radars were detecting the exhaust plume.
    It appears the designers were well aware of the fact and attempted to reduce the RCS by adding Cesium to the fuel.

    http://www.foia.cia.gov/sites/defaul...0001458639.pdf

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  • gunnut
    replied
    According to the analysts from Taiwan, the J-31 conducted brief demonstrations at the air show. It went through some basic maneuvers, rolls, turns, but nothing fancy. The J-31 is probably at the early X-35 stage of development. After landing, the J-31 was taxied to a covered shelter, away from public eyes.

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  • Stitch
    replied
    Originally posted by SteveDaPirate View Post
    Doesn't a big plume of particulate matter light up a radar screen? I would think clean burning engines would be a prerequisite to a stealth aircraft.
    Along those lines, my understanding is that the exhaust plume from the J-58's on the SR-71 actually reflected radar, and had a radar signature all of their own; I'm guessing the RCS of the SR-71, due to the rudimentary stealth measures it incorporated, was probably about the same as the RCS from it's exhaust plume(s).

    Attached Files

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  • gunnut
    replied
    I thought the black smoke from jet engine indicates incomplete combustion. Is it possible that the Mig pilot kicked in the afterburner and the extra fuel did not fully burn off?

    Talk about black smoke, check out these early B-52s, most likely with J-57 engines using water injection for takeoff performance:

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  • Jimbo
    replied
    Originally posted by SteveDaPirate View Post
    Doesn't a big plume of particulate matter light up a radar screen? I would think clean burning engines would be a prerequisite to a stealth aircraft.
    Could the particulates possibly be from flying through dirty air close to the ground? I don't know, but it seems to me flying through smoggy air is going to result in some smokey air coming out of your engines.

    I looked up some images of other planes with the same type of engine and it seems to be a little hit or miss on photos with and without smoke of the flying craft. Anybody have a better idea on these engines that are able to discuss?

    Though it seems to me that not getting a new engine in your brand new fighter that is supposed to have reduced IR and radar signature is a big compromise.

    Edit: somewhat ninja-ed by Stitch above so those jets do generate quite a bit of visible smoke regardless of air quality.
    Last edited by Jimbo; 18 Nov 14,, 18:59.

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  • Stitch
    replied
    Originally posted by SteveDaPirate View Post
    Doesn't a big plume of particulate matter light up a radar screen? I would think clean burning engines would be a prerequisite to a stealth aircraft.
    That is one very noticeable difference between Eastern bloc engines and Western engines; those engines (the RD-93's) remind me of the old GE J-79's from the '60's/'70's. I was watching a video of a Polish F-16C Block 52+ flying with one of their MiG-29's, and the difference between the engines was very noticeable:



    www.youtube.com/watch?v=c-UHWJf0Gk0

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