J-XY - maybe J-35 - next generation carrier-borne fighter


manatee988

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FC-31 is not a large heavyweight fighter, it’s medium sized. WS-10 is a larger engine, and in a twin engine configuration would be for a large fighter. For example, the medium-weight J-10C uses a single WS-10B.

Hopefully someone on the forum can recommend some good books/materials for you to read to further your understanding of military aviation?
I see. So theoretically if the WS-15 is successfully produced it could make FC-31 a single engine aircraft like the F-35?
 

iantsai

Junior Member
Registered Member
I'm not an expert on aeronautical engineering. Can anyone explain why they would put an low powered engine in the FC-31? Why not the WS-10 or something? Is it size or fuel consumption or something else?
SAC failed the 5th generation fighter aircraft biding competition to the CAC in late 2000s. Then it decided to develop a new 5th gen stealth fighter aircraft by itself.

But, if it designed another heavy fighter aircraft like J-20, there would be almost no chance for the new aircraft to be accepted by the PLAAF.

And also, at that time WS-10 was not yet entering batch production, the only available engine for a heavy aircraft was AL-31, which was needed by both J-10s and J-20s.

Therefore SAC would more probably lose the competition for the engine supply if they designed a self-developed fighter requiring AL-31s.

So SAC designed an medium aircraft with two RD-33/93 engines, aimed the international 5th gen medium fighter aircraft market. This was the origin of FC-31 and why it wasn't equipped with larger AL-31/WS-10 engine.
 

GTI

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I see. So theoretically if the WS-15 is successfully produced it could make FC-31 a single engine aircraft like the F-35?
FYI a single WS-10C could do the same thing as well (or B, with even lower performance)…

Yes… But no, you would end up designing a new aircraft. The fuselage would be have to be drastically redesigned - which would affect other aerodynamic properties, which will require further redesign (e.g. wings and vertical stabilisers). By the time you are done, you would have a whole new fighter on your hands.
 

iantsai

Junior Member
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for RD-93, the max thrust without afterburner is [email protected] kg/(kN·h), and [email protected]/(kN·h) fuel consumption rate

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.
I forgot to add another enterprising presumption: the WS-19 engine has ONLY 60% fuel consumption rate of the RD-93 engine.
 

tphuang

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I forgot to add another enterprising presumption: the WS-19 engine has ONLY 60% fuel consumption rate of the RD-93 engine.
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.
 

sunnymaxi

Junior Member
Registered Member
I'm not an expert on aeronautical engineering. Can anyone explain why they would put an low powered engine in the FC-31? Why not the WS-10 or something? Is it size or fuel consumption or something else?
both are different category engines. WS-10 is large and high thrust engine. WS-19 is medium thrust engine.

you need to understand one thing, high thrust is not everything in engine. durability , reliability , T/W ratio , advance materials and life hours are the most essential parts. WS-19 is the product of latest Chinese breakthroughs in materials and Metallurgy. and the better engine than any WS-10 variant except WS-10C. can super cruise , better fuel consumption.
 

iantsai

Junior Member
Registered Member
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.
I see.

But If I presume the new WS-13+/WS-19's fuel consumption rate being 85% of RD-93 and the overall operation fuel consumption rate at average 80% of full thrust(without afterburner) fuel consumption rate, then we could calculate the total fuel needed for a 2.5 hours flight operation to be:

75(kg/kNfh) * 50kNf / 1000 *0.85 * 0.8 * 2 * 2.5h = 12.75t (per 2.5h flight).

This result of calculation denied J-XY being an EW 12.5t, MTOW 25t and combat range 1000km fighter, which requires the aircraft to fly more than one hour to reach the battle field, stay/fight/patrol for 20 minutes and then return to the carrier.

Let's suppose the aircraft having 600km combat range, which requires it to fly 40 mins to the battle ground and fight for 20 mins and fly back. Then it's 1.66h flight. The fuel consumption would be:

75(kg/kNfh) * 50kNf / 1000 *0.85 * 0.8 * 2 * 1.67h = 8.52t (per 1.67h flight).

This fuel consumption would leave an acceptable 4 tons payload, about 3 tons ammunitions after 1t reserved 15 min fuel.

Also we could calculate the available ammunition capacity when the combat range set to 800km:

75(kg/kNfh) * 50kNf / 1000 *0.85 * 0.8 * 2 * 2h = 10.2t (per 2h flight).

There is about 1.3t ammunition payload capacity left considering the 1t/15min reserved fuel.

Hard to feel optimistic for the range of a medium twin engine fighter.
 

Blitzo

Lieutenant General
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There is an AVIC reference for some of the specifications for FC-31 V2 from zhuhai a few years back.
(Yes, use the left column in Chinese given the right side used a machine translation, no need to point it out everytime)

I'm unsure if the real aircraft would have been fully rated for this performance, but I suspect the J-XY/35 probably would not be far.

jl4cGud.jpg
 

ZeEa5KPul

Major
Registered Member
I see.

But If I presume the new WS-13+/WS-19's fuel consumption rate being 85% of RD-93 and the overall operation fuel consumption rate at average 80% of full thrust(without afterburner) fuel consumption rate, then we could calculate the total fuel needed for a 2.5 hours flight operation to be:

75(kg/kNfh) * 50kNf / 1000 *0.85 * 0.8 * 2 * 2.5h = 12.75t (per 2.5h flight).

This result of calculation denied J-XY being an EW 12.5t, MTOW 25t and combat range 1000km fighter, which requires the aircraft to fly more than one hour to reach the battle field, stay/fight/patrol for 20 minutes and then return to the carrier.

Let's suppose the aircraft having 600km combat range, which requires it to fly 40 mins to the battle ground and fight for 20 mins and fly back. Then it's 1.66h flight. The fuel consumption would be:

75(kg/kNfh) * 50kNf / 1000 *0.85 * 0.8 * 2 * 1.67h = 8.52t (per 1.67h flight).

This fuel consumption would leave an acceptable 4 tons payload, about 3 tons ammunitions after 1t reserved 15 min fuel.

Also we could calculate the available ammunition capacity when the combat range set to 800km:

75(kg/kNfh) * 50kNf / 1000 *0.85 * 0.8 * 2 * 2h = 10.2t (per 2h flight).

There is about 1.3t ammunition payload capacity left considering the 1t/15min reserved fuel.

Hard to feel optimistic for the range of a medium twin engine fighter.
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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