PRC VCE and low bypass engines (fighters, tactical jets, UAVs, others)

[tphuang]

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中发天信 has passed validation on 1000 kgf turbofan engine in Nanchang. It has improved fuel economy & thrust efficiency. This company's previous XX850 turbojet engine was China's first 10kN class aeroengine with FADEC, currently used in high altitude/high speed large UAV. Looks like this is similar in thrust and can be used for even longer ranged drone.

 

[RadDisconnect]

Something came to mind, since thrust of WS-15 has been a point of discussion. Back in July 2023, Chinese netizens in Chengdu recorded the J-20A with WS-15 doing a full AB takeoff, video here. Here is also a comparison with the F-22 from EAA Airventure 2015, which is also in July so also represent similar hot temperature conditions.

This is interesting because I think this can let us make a first order estimate on WS-15 thrust performance, and I'm assuming that the J-20A weighs similar to F-22 empty at about 20,000 kg (44,000 lbs) while carrying about 10,400 kg (23,000 lbs) of fuel, with the J-20A fuselage longer while the wings are a bit smaller, and the nacelles also has less volume since it wraps around the engines more closely than on the F-22. This means that, at full fuel and no weapons, F-22 is about 28,100 kg (62,000 lbs) while J-20 is about 30,400 kg (67,000 lbs).

So based on timing these footage, the F-22 is wheels up in about 15 seconds from brake release to wheels up, while the J-20 from the footage is about 17-18 seconds, it seems. Given the weight difference assumed (I'm assuming that the J-20A took off with full internal fuel), then that is consistent with WS-15 having a similar installed thrust as the F119 while the J-20A has a higher takeoff weight. If we want to give the J-20A the benefit of the doubt and assume that the slightly lower aspect ratio wing increases rotation and takeoff speed slightly. So, 160-170kN would be my estimate, which is just at F119 level or maybe a tad higher.

Also, essentially the same class as the izd.30 (AL-51F-1) for the Su-57M as well, which is a 16.5 metric ton thrust (162kN) engine.

 

[latenlazy]

Something came to mind, since thrust of WS-15 has been a point of discussion. Back in July 2023, Chinese netizens in Chengdu recorded the J-20A with WS-15 doing a full AB takeoff, video here. Here is also a comparison with the F-22 from EAA Airventure 2015, which is also in July so also represent similar hot temperature conditions.

This is interesting because I think this can let us make a first order estimate on WS-15 thrust performance, and I'm assuming that the J-20A weighs similar to F-22 empty at about 20,000 kg (44,000 lbs) while carrying about 10,400 kg (23,000 lbs) of fuel, with the J-20A fuselage longer while the wings are a bit smaller, and the nacelles also has less volume since it wraps around the engines more closely than on the F-22. This means that, at full fuel and no weapons, F-22 is about 28,100 kg (62,000 lbs) while J-20 is about 30,400 kg (67,000 lbs).

So based on timing these footage, the F-22 is wheels up in about 15 seconds from brake release to wheels up, while the J-20 from the footage is about 17-18 seconds, it seems. Given the weight difference assumed (I'm assuming that the J-20A took off with full internal fuel), then that is consistent with WS-15 having a similar installed thrust as the F119 while the J-20A has a higher takeoff weight. If we want to give the J-20A the benefit of the doubt and assume that the slightly lower aspect ratio wing increases rotation and takeoff speed slightly. So, 160-170kN would be my estimate, which is just at F119 level or maybe a tad higher.

Also, essentially the same class as the izd.30 (AL-51F-1) for the Su-57M as well, which is a 16.5 metric ton thrust (162kN) engine.

Given the number of unknown factors like lift coefficient at takeoff, what each plane’s takeoff weight is etc this is really not a useful exercise. Far too many ifs to limit the range of error bars.

 

[latenlazy]

Something came to mind, since thrust of WS-15 has been a point of discussion. Back in July 2023, Chinese netizens in Chengdu recorded the J-20A with WS-15 doing a full AB takeoff, video here. Here is also a comparison with the F-22 from EAA Airventure 2015, which is also in July so also represent similar hot temperature conditions.

This is interesting because I think this can let us make a first order estimate on WS-15 thrust performance, and I'm assuming that the J-20A weighs similar to F-22 empty at about 20,000 kg (44,000 lbs) while carrying about 10,400 kg (23,000 lbs) of fuel, with the J-20A fuselage longer while the wings are a bit smaller, and the nacelles also has less volume since it wraps around the engines more closely than on the F-22. This means that, at full fuel and no weapons, F-22 is about 28,100 kg (62,000 lbs) while J-20 is about 30,400 kg (67,000 lbs).

So based on timing these footage, the F-22 is wheels up in about 15 seconds from brake release to wheels up, while the J-20 from the footage is about 17-18 seconds, it seems. Given the weight difference assumed (I'm assuming that the J-20A took off with full internal fuel), then that is consistent with WS-15 having a similar installed thrust as the F119 while the J-20A has a higher takeoff weight. If we want to give the J-20A the benefit of the doubt and assume that the slightly lower aspect ratio wing increases rotation and takeoff speed slightly. So, 160-170kN would be my estimate, which is just at F119 level or maybe a tad higher.

Also, essentially the same class as the izd.30 (AL-51F-1) for the Su-57M as well, which is a 16.5 metric ton thrust (162kN) engine.

Just to specify maybe the most direct factor that would make this estimation method unreliable, we don’t know what the available pitch force at takeoff condition is for each plane. The F-22’s pitching force from 0 airspeed is a combination of direct vectored thrust and aerodynamic loading, but the J-20’s pitching force at 0 airspeed is dependent only on aerodynamic loading. Available pitching force at 0 airspeed for a plane without TVC will be more constrained than for a plane with TVC, since the latter will have available pitching force from the moment the engine lights up while the former needs to build up airspeed before it has available force to pitch.

 

[RadDisconnect]

Given the number of unknown factors like lift coefficient at takeoff, what each plane’s takeoff weight is etc this is really not a useful exercise. Far too many ifs to limit the range of error bars.

Yes there are some unknown factors but overall, both aircraft have a similar aspect ratio wing, but are static unstable aircraft, and lift coefficient at takeoff are roughly similar. And the F-22 in demos takeoff at full fuel, and I assumed the J-20A was as well, but that may be too much of an assumption on my part.

As far as TVC goes, it helps with earlier or faster rotation but actual takeoff doesn’t depend on it, and in fact not following the TOLD for the F-22 just because of TVC is not advised because early rotation and wheels up was responsible for a crash landing that took 5 years to repair.

Again I caveated it that this is a 1st order estimate, so I wasn’t being deliberately unfavorable for either aircraft.

 

[latenlazy]

Yes there are some unknown factors but overall, both aircraft have a similar aspect ratio wing, but are static unstable aircraft, and lift coefficient at takeoff are roughly similar. And the F-22 in demos takeoff at full fuel, and I assumed the J-20A was as well, but that may be too much of an assumption on my part.

How do you know both aircraft lift coefficient at takeoff are roughly similar? One is a narrower aspect ratio wing with a long coupled canard delta and the other is traditional configuration. One’s wings are notably thicker than the other. “Similar” is doing a lot of unearned work here imo.

As far as TVC goes, it helps with earlier or faster rotation but actual takeoff doesn’t depend on it, and in fact not following the TOLD for the F-22 just because of TVC is not advised because early rotation and wheels up was responsible for a crash landing that took 5 years to repair.

Faster rotation changes the lift coefficient. You are reaching a different part of your lift curve at a different rate if you can rotate faster. At most you’re talking about a 1-2 second difference in takeoff time (based on my own assessment of your shared clips, and the J-20 clip is *very* grainy), so even if all your other parity assumptions are right single digit degrees of early rotation (say from a TVC assist on the margins) will count for a lot. Heck, even a difference in engine thrust ramp up time (which itself may or may not have anything to do with differences in engine characteristics since this is also shaped by local air conditions at takeoff) would wash out any meaningful precision based on this method of estimation. These are the kinds of issues I’m referring too when I talk about error bars being too wide.

Again I caveated it that this is a 1st order estimate, so I wasn’t being deliberately unfavorable for either aircraft.

My critique is not about which aircraft is favored. The method of estimation here is a bit like trying to eyeball RCS while fudging a bunch of visually identifiable factors that are obviously different. I really don’t think this is a meaningful method to estimate anything.

 

[tphuang]

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F406 turbofan engine with 600kg thrust and max height of 15km was displayed in 2025/9. It can also be used for HALE/high speed integrated UCAV + emergency rescue industrial drones. Top speed is mach 0.85. Engine dry weight is 134kg. It had maiden flight on 2026/5 and can be used for 1.5 to 4t drones. Also developed by 天府轻动 & engine had first ignition in 2024/12. Development cycle was only 8 months up until that time. 天府轻动 is also developing 60kW hybrid motor & 100 kgf turbojet engine as part of this series of product.

 

[BoraTas]

The 2 stage LPT is bizarre though. I'd expect the WS-21 to be a 3-7-1-1. In fact even the RD-33 family it's related to never had a 2 stage LPT configuration.

It may be loading its LPCs and fan aggressively necessitating two LPT stages for the desired characteristics. IMO the WS-21 is way too divergent from the original WS-13 or RD-33. They made right call renaming it as the WS-21.

 

[_killuminati_]

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