J-XY/J-35 carrier-borne fighter thread

tphuang said:

I don't think that would be possible.

In civilian world, a generational leap normally results in 15% fuel consumption improvement and that normally requires increasing the bypass ratio (check the GTF engine for A321NEO vs the VK-2500 for A321CEO). Let's say RD-93 was really bad for its generation and WS-19 is pretty good for its generation. Even so, I would say a 25% bump in T/W ratio (from 8t to 10t) + 20% gain in fuel consumption would be monumental improvement. Decreasing by 40% is quite unlikely unless WS-19 suddenly became a high bypass engine.

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Bypass ratio isn’t the only way to improve engine efficiency. If you can improve the compression ratio of the HPC section and turbine inlet temperature you will also get greater efficiency. In fact those are arguably the primary factors for driving efficiency, with bypass ratio being a secondary factor. HPC compression ratio drives how much energy you can extract from your airstream and TIT drivers how efficiently you can recover energy from your turbine. For example, the F135 has a slightly better specific fuel consumption compared to the F100 but a smaller bypass ratio, while attaining 40%+ gain in thrust. In theory an F135 based engine that has the same bypass ratio as the F100 would probably have even higher thrust and better fuel economy. But in exchange it would lose a lot in jet exit velocity, and thus top attainable speed.

The limiting factor in a jet turbine is the total energy extracted from your free stream. What’s competing for your energy budget isn’t actually total thrust vs fuel economy but total mass flow + fuel economy vs jet velocity. You can spend that energy budget on maximizing total mass flow over time, or maximizing jet exit velocity. The latter is going to get both less total mass flow (thus thrust) and less energy recovery per unit of mass flow mostly because you are expelling the thermal energy from combustion to the jet stream, essentially to ensure a faster reaction mass, rather than recovering it with your turbine to move more mass quantity with your fan. So in theory it’s possible to improve both total thrust and fuel efficiency, but what you lose is top attainable speed. Which is why we probably shouldn’t expect the WS-19 to have both better fuel economy and more thrust, because even if you have higher hpc compression and higher turbine inlet temperature to improve your energy budget and energy recovery, you’re likely trading away the ability for the engine to supercruise if you keep the bypass ratio the same to net the gain in energy budget for greater mass flow and fuel efficiency with a larger fan section.

ZeEa5KPul said:

It's not that big of a deal, they can be buddy refueled by J-15s equipped with drop tanks acting as ad hoc tankers or a dedicated stealth tanker.

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Yes.

But if the combat capability of J-XY is highly dependent on J-15 or other aircrafts, then it will have very limited purposes.

for RD-93, the max thrust without afterburner is 50kNf@75 kg/(kN·h), and 84kNf@188kg/(kN·h) fuel consumption rate

iantsai said:

That means a 2250kg/h fuel consumption for each engine at full thrust. For twin-engine J-XY it's a doubled 4.5t fuel/h.

Let's assume the engines consuming would be average 80% of max fuel consumption rate during an operation, then it's 3.6t fuel consumption per hour.

Suppose the combat range is 1000km with a 20 minutes stay at the battle field, then a standard operation would take an about 2.5h interval. Then the total fuel consumption would be 9 tons.

With 12.5t empty weight and 25t MTOW and 9t fuel consumption/2.5h operation, the J-XY would have 25-12.5-9=3.5t max payload left, with the weight of the pilot and necessary redundant fuel included.

This is not a very impressive number.

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25t mtow and 12.5t empty weight are pretty bad estimates of J-xy, and assuming a 16t empty weight is a bit pessimistic. Also assuming that the engines operate at 80% of full dry thrust and each provide the full 88/95kn of thrust for the entire mission is out right wrong, as the thrust of the engines change pretty drastically with regard to its working conditions (Mach number, ambient air temperature, altitude, etc) so your calculations are of very little help. Mission fuel consumption and range are not so simply calculated and we should do well to avoid being overly confident in dishing out such claims when there are little to no accurate data to use.

Scchwerter_ said:

for RD-93, the max thrust without afterburner is 50kNf@75 kg/(kN·h), and 84kNf@188kg/(kN·h) fuel consumption rate

25t mtow and 12.5t empty weight are pretty bad estimates of J-xy, and assuming a 16t empty weight is a bit pessimistic. Also assuming that the engines operate at 80% of full dry thrust and each provide the full 88/95kn of thrust for the entire mission is out right wrong, as the thrust of the engines change pretty drastically with regard to its working conditions (Mach number, ambient air temperature, altitude, etc) so your calculations are of very little help. Mission fuel consumption and range are not so simply calculated and we should do well to avoid being overly confident in dishing out such claims when there are little to no accurate data to use.

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I recall that years ago pb said that the J-XY/35 would have:
-MTOW of 29-30t
-operating empty weight of 14t
-internal fuel of 7t
-total payload (internal weapons bay and external payload) capacity of 8t

Blitzo said:

I recall that years ago pb said that the J-XY/35 would have:
-MTOW of 29-30t
-operating empty weight of 14t
-internal fuel of 7t
-total payload (internal weapons bay and external payload) capacity of 8t

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iirc that was around 2017-18 period? Original post was gone along with cjdby forum, but assuming PB’s figures are true (I think they’re quite likely to be within the ballpark since he has been proven as a credible source) then it doesn’t look too bad IMO. 14t empty weight would be quite an achievement regarding the ver 1.0 had an empty weight of 12.5t, and the current J-xy is most likely larger in size, had to be designed to be carrier-based, and most likely have much more internal avionics and sensors than the 1.0 which was little more than a demonstrator.

Also, if we’re going to do calculations based off of inaccurate estimates (personally I do not like this) then I’d like to point out that the mig-29 has a 2100km range with internal fuel and centerline tank providing a total of 5700kg. If the J-xy has ~7t of fuel and has the benefit of operating with no external stores (as opposed to the centerline tank carrier by the mig-29) then I have a hard time believing that the internal range of the J-xy won’t be substantially larger than 2100km. Add to that the fact that 5th gen fighters generally carry ordinance in weapon bays which doesn’t add to the drag of the airframe unlike previous jets, imo the J-xy will likely have at least a descent (and maybe an outstanding) mission radius when carrying weapons internally.

Scchwerter_ said:

iirc that was around 2017-18 period? Original post was gone along with cjdby forum, but assuming PB’s figures are true (I think they’re quite likely to be within the ballpark since he has been proven as a credible source) then it doesn’t look too bad IMO. 14t empty weight would be quite an achievement regarding the ver 1.0 had an empty weight of 12.5t, and the current J-xy is most likely larger in size, had to be designed to be carrier-based, and most likely have much more internal avionics and sensors than the 1.0 which was little more than a demonstrator

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I have a feeling that the numbers for the FC-31 per the image in my post #1889, represents a "missionized" FC-31 V2 configuration. I'm not sure if the proper flying airframe would have been fully rated or demonstrated for it.

I'm not sure if we ever had OEW numbers for the original FC-31 V2.

The MTOW from the FC-31 V2 is increased from 28t to 29-30t for J-XY/35, while the payload remains the same.

Of note, the combat radius of FC-31 V2 was listed as 1200km, and I would be surprised if J-XY/35 was lower than that.

Scchwerter_ said:

for RD-93, the max thrust without afterburner is 50kNf@75 kg/(kN·h), and 84kNf@188kg/(kN·h) fuel consumption rate
25t mtow and 12.5t empty weight are pretty bad estimates of J-xy, and assuming a 16t empty weight is a bit pessimistic.

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25t mtow and 12.5t empty weight is based on what you estimated in #1874...

Scchwerter_ said:

for RD-93, the max thrust without afterburner is 50kNf@75 kg/(kN·h), and 84kNf@188kg/(kN·h) fuel consumption rate
Also assuming that the engines operate at 80% of full dry thrust and each provide the full 88/95kn of thrust for the entire mission is out right wrong, as the thrust of the engines change pretty drastically with regard to its working conditions (Mach number, ambient air temperature, altitude, etc) so your calculations are of very little help. Mission fuel consumption and range are not so simply calculated and we should do well to avoid being overly confident in dishing out such claims when there are little to no accurate data to use.

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During a flight the engine would not always working with the max thrust output, so presuming that the overall fuel consumption as 80% of the max military thrust(without aftreburner) is reasonable.

If you won't accept this estimation, then please use your own model and make some calculation.

iantsai said:

25t mtow and 12.5t empty weight is based on what you estimated in #1874...


During a flight the engine would not always working with the max thrust output, so presuming that the overall fuel consumption as 80% of the max military thrust(without aftreburner) is reasonable.

If you won't accept this estimation, then please use your own model and make some calculation.

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yeah no, if you don’t understand the difference between versions of FC-31 and the current J-xy then it’s your job to figure it out. As to your model being wrong I said that because the gross thrust that an engine can produce varies wildly according to the conditions, simply using the “rated” thrust and TSFC to calculate a number and times it by 0.8 is no where near a proper estimate. For your information the rd-33 has a claimed installed max thrust of around 7400kgf at S.L. and M0.25, but the figure drops to 4000kgf at 8km and M0.8 (which is much closer to a real life cruising altitude and mach number) As I said go figure, my claim is that these calculations are too complex to be made based on public information, and I have now twice given reason as to why your model is no where near accurate.

Blitzo said:

I'm very confused.

How does sortie rate not have significant relevance to the missions of sea control and airspace control, that would be required of Chinese carriers?

....

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Here's my guess.
wikipedia says the Ford carrier can do, "160 sorties per day for 30-plus days, with a surge capability of 270 sorties per day."
However...
We all know jet planes are super high maintenance. For every hour of flight time there is a ton of hours a plane spends in the hangar getting fixed on by an aircraft mechanic. Just because the catapults on an aircraft carrier can sustain a sortie rate of 160 per day doesn't mean the aircraft mechanics on board can keep up with that. Who knows maybe the actual sortie rate of a carrier is only 80 per day when factoring the human capacity of aircraft mechanics?

A rough size comparison.