Chengdu next gen combat aircraft (?J-36) thread

[Tomboy]

I have a feeling that J-36 would not enter service until VCE becomes available, I did some rough estimates and found that the range improvements offered by VCEs and also the additional cooling capacity/power generation and potentially additional bypass air for fluidic TVC is just too good to ignore. IMO a WS-15 powered J-36 would be massively handicapped by range, power generation and possibly even maneuverability. Not having VCE impacts the J-36 alot more than J-XDS IMO as J-36 is literally built around range and its massive sensor suite while I think J-XDS might actually be able to enter service ahead of J-36 with advanced WS-15 derivatives. I'd personally estimate J-36 to enter service in the early 2030s assuming VCE engine dev is similar to US efforts.

 

[siegecrossbow]

I have a feeling that J-36 would not enter service until VCE becomes available, I did some rough estimates and found that the range improvements offered by VCEs and also the additional cooling capacity/power generation and potentially additional bypass air for fluidic TVC is just too good to ignore. IMO a WS-15 powered J-36 would be massively handicapped by range, power generation and possibly even maneuverability. Not having VCE impacts the J-36 alot more than J-XDS IMO as J-36 is literally built around range and its massive sensor suite while I think J-XDS might actually be able to enter service ahead of J-36 with advanced WS-15 derivatives. I'd personally estimate J-36 to enter service in the early 2030s assuming VCE engine dev is similar to US efforts.

Early 2030s is already very optimistic. Lots of work ahead.

 

[Blitzo]

I have a feeling that J-36 would not enter service until VCE becomes available, I did some rough estimates and found that the range improvements offered by VCEs and also the additional cooling capacity/power generation and potentially additional bypass air for fluidic TVC is just too good to ignore. IMO a WS-15 powered J-36 would be massively handicapped by range, power generation and possibly even maneuverability. Not having VCE impacts the J-36 alot more than J-XDS IMO as J-36 is literally built around range and its massive sensor suite while I think J-XDS might actually be able to enter service ahead of J-36 with advanced WS-15 derivatives. I'd personally estimate J-36 to enter service in the early 2030s assuming VCE engine dev is similar to US efforts.

VCEs would certainly greatly improve the J-36's overall capabilities relative to being powered by WS-15s, but the question should be whether WS-15 powered J-36s offer a sufficiently improved capability relative to other existing platforms to induct them in limited numbers until a VCE powered variant is ready.

I also doubt a VCE will be ready for induction by early 2030s.

 

[siegecrossbow]

VCEs would certainly greatly improve the J-36's overall capabilities relative to being powered by WS-15s, but the question should be whether WS-15 powered J-36s offer a sufficiently improved capability relative to other existing platforms to induct them in limited numbers until a VCE powered variant is ready.

I also doubt a VCE will be ready for induction by early 2030s.

It’s worth inducting with WS-15 just so that pilots can develop new tactics around the platform so there is less of a learning curve when other pieces are falling into place.

 

[Blitzo]

It’s worth inducting with WS-15 just so that pilots can develop new tactics around the platform so there is less of a learning curve when other pieces are falling into place.

I agree, much like how J-20s with WS-10s (or even the Al-31s) provided a much needed paradigm shift to the PLAAF even though the initial batches had inferior subsystems (including avionics) and less sophisticated materials than later batch J-20s (let alone J-20A with WS-15), I expect J-36s with interim engines to provide a similar uplift in capability that it would be worthwhile (if not essential) to procure them.

 

[Tomboy]

I did some very rough calculations using the Breguet Range Equation:

Assuming J-36 as a massive, blended body aircraft with large wing area would have a L/D ratio ~30 percent better than J-20(IMO I think it's a bit conservative considering J-36 has 3 times as much wing area, no additional control surfaces, flexible aircraft skin and could use TVC for trim), that J-36 has 55k lbs(25 tons) of fuel and a empty mass(including payload) of 75000lbs(35 tons) and J-36 uses the same WS-10C engine has the base J-20. Also, assuming both J-20 and J-36 would be running their engines at the same power setting.

J-20 right now seems to have a fuel quantity of 26000lbs(12 tons) of fuel and a MTOW of ~82000lbs or 37 tons which means when "empty" the J-20 will have a mass of 56000lbs(25 tons).

Now with this equation:


Since we don't really know the specific fuel consumption of WS-10Cs we could just cancel out the term by dividing them

R(J-36)/R(J-20)=2/3*1.3*(ln(130,000lbs/75,000lbs)/ln(82000lbs/56000lbs))=1.25

J-20 has a combat radius of around 1100nm, so the rough calculations say J-36 would have a combat radius of around 1400nm and this is with old WS-10C. Realistically with intended VCEs, all the aerodynamic trickery and massive use of composites and 3D printed aerostructure I think J-36 could have a combat radius above 2000nm.

IMO, the VCE that is intended to be used by J-36/J-XDS wouldn't have too much of a thrust improvement over WS-15 but would massively focus on cooling capacity/power generation and fuel efficiency. So I think it's pretty reasonable to assume that the new engine would be in the 18tf class(Especially when WS-15 is already in the 160kN-170kN class), accounting in thrust loss from intakes and nozzles etc, this would give J-36 around a TWR of ~1.1 at combat weight. Coupled with very low wing loading(~180kg/m^2 at combat load which is comparable to WW2 era turnfighters ie. Bf-109G's wingloading is 196kg/m^2) should in theory give J-36 a very good sustained turn rate and energy retention although it might be a bit lacking in instantaneous turn rate.

Cross posted from SPF

 

[AndrewS]

Cross posted from SPF

J-20 empty weight is significantly less than 25 tonnes. It's being listed at 17 or 20 tonnes.

Plus factor in a pair of drop tanks at the beginning of each flight, for both the J-20 and J-36.

Engines for the first J-36 will almost certainly be WS-15 class.

Variable cycle engines would offer a 10% improvement in thrust and 20% improvement in fuel efficiency?

 

[ACuriousPLAFan]

Cross posted from SPF

Firstly, where did the J-36 fuel capacity (25 tons) and empty weight + payload (35 tons) figures originate from?

Secondly, the calculations are done by assuming that the production J-36 would still be using WS-10C.

Given that the WS-15-powered J-20As are expected to enter serial production this year (if not already and no latter than next year), which means that by the time when the J-36 is ready to enter LRIP stage (which should be no latter than the mid-2030s), the WS-15 would've long been ready for the J-36 as well. In this regard, being an all-encompassing upgrade over the WS-10C, I certainly expect that the WS-15 is also better in this regard.

Moreover, 1400 nautical miles = ~2592 kilometers of combat radius is still pretty good by itself. The F-47's purported combat radius of 1000+ nautical miles = 1852+ kilometers - Even by rounding off that value to ~2000 kilometers, that's still shy of ~500 kilometers.

As for the combat radius jump from 1400 nautical miles to 2000+ nautical miles (which is ~3704 kilometers) with the usage of VCE/ACE-based WS-XX instead of WS-10C/15 - What's the basis for such inference?

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In the meantime, I do expect that the J-XDS will have equivalent combat radius as the F-47.

 

[AndrewS]

Just a thought.

If the J-36 can fit the PL-17, couldn't this be launched at a distance of 500km against aircraft still on the ground?

 

[Tomboy]

Firstly, where did that J-36 fuel capacity (25 tons) originate from?

It's just an estimate based of a 60-ton MTOW, I think it's a pretty fair assumption considering that's a whopping ~42 percent fuel fraction, compared to a large flying wing design like B-2 which has around ~50 percent. Normal fighters right now have anywhere between 25-30 percent(Yes, MiG-31 has a fuel fraction of 45 percent but that's literally because the entire plane is just a fuel tank with engines bolted to it) at MTOW. However real numbers could be even higher with novel light weight fuel tanks etc.

Secondly, the calculations are done by assuming that the production J-36 would still be using WS-10C.

We don't have spec on WS-15 powered J-20, so calculations are done with WS-10C since the equation requires specific fuel consumption of the engine but by comparing it to J-20 which conveniently also use WS-10C we could cancel the term out and find a range relative to J-20's range as a base estimate.

As for the combat radius jump from 1400 nautical miles to 2000+ nautical miles (which is ~3704 kilometers) with the usage of VCE/ACE-based WS-XX instead of WS-10C/15 - What's the basis for such inference?

As for this, VCE engines(AETP program) was advertised to increase fuel efficiency by up to 25 percent(And this was relative to an already very efficient engine, the F-135) I just assumed Chinese efforts would amount to at least this amount of fuel saving and probably quite a bit more due to WS-10C being compared here would be 2 generations out of date. Also, the estimate that L/D ratio of J-36 would only be 30 percent better than J-20 considering its tailless blended body config with massive wing area is rather conservative and realistically I believe it could offer more aerodynamic efficiency improvement over J-20. If you account into these changes a combat radius of 2000nm becomes rather realistic.