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

[Deleted member 24822]

What’s even the point of Mach 3. I never understood the obsession with it.

Round number syndrome. It's a signpost to display progression that's easier to get excited over than some vagueish notion of improving fundamentals

 

[iBBz]

Weird strawman. The CFM-56 is incomparable to the WS-15 and nobody says the J-36 is a Mach 4 aircraft. Your comment on thrust is flat out wrong and if you believe that you need to read more on jet engines. Top speed is where thrust equals drag. Regardless of the thrust curve more thrust means a higher top speed. The only exception is when the engine is temperature or pressure limited which I don't think is the case for the WS-15 at Mach 2.2.

Well if your argument is top speed is where thrust equals drag, why wouldn't the CFM56 work in this case? Instead of doing the "You don't know what you are talking about" or the "I don't think the WS-15 maxes out at M2.2", provide a logical counter argument that at least attempts to use some math and physics.

Ke= 1/2mv^2. This means you can EITHER choose to favour increasing the velocity of the jet or the mass airflow while providing the same amount of energy. The reason you choose a different engine for the job, is because you want your jet speed to be as close as possible to the forward motion of the plane. This isn't possible because of drag, so the jet will always have to be slightly faster than freestream, and there will be some rubbing between the jet and the free stream. That is part of the reason you need different engines for different applications.

You wandering into irrelevant things. The fact is the F-15 was faster despite being optimized for things that the B-58 weren't. It couldn't sustain that speed for long because it didn't have 45 tonnes of fuel and it was a draggier aircraft at all speeds.

The B-58 was aerially refueled five times if I remember correctly, and it sustained an 8+ hour supersonic flight without a gram of titanium, only aluminum and fiberglass. That is a testament to how important drag is, because with the wrong geometry, you would need titanium and body maintenance after supersonic flights, such as in the case of the F-15.

If you are actually claiming this then you should really stop writing and do not discredit yourself further. One of the biggest revelations of the Vietnam war was that the speed wasn't that important. 4th gens were designed around sustained transonic turns, energy maneuverability, high-AoA and nose authority. They had much higher low-AoA drag coefficients compared to previous aircraft because of their oversized wings, control surfaces and ample vortex generation features. The F-16 has a glide ratio around 8:1 when clean for example. The F-18 is even worse. It is so bad that once McDonnell Douglas attempted to market how little performance the aircraft lost when bombs were attached (actually, the airframe is so draggy that the drag from the bombs wasn't that important)

Speed wasn't important and drag was so high, but the F-15 could somehow push M2.4+ with less than 50k lb of thrust?
The F-15 had oversized wings? Its wing span is just 13 meters, over 2 meters less than the Su-27.
Form, skin friction, and wave drag from the armament had little importance on the total drag of the aircraft?

What M5+ ? Stop your strawmans.

Strawmans like your "The only exception is when the engine is temperature or pressure limited which I don't think is the case for the WS-15 at Mach 2.2" nonsense.

Hmm yes, PLAAF and USAF won't use their most survivable aircraft in contested air space. Air warfare is all about launching cruise missiles and less survivable aircraft are better for contested airspace. I was holding myself from being sarcastic but I don't think you realize what you are advocating for.

Yea because Afghanistan, Iraq, Syria, Libya etc. all had S-300s hunting USAF aircraft, but somehow they miraculously failed due to EW. These make for nice bedtime stories.

 

[EmoBirb]

According the the Christmas Salt Bae (folk I got the Christmas first flight rumor from) AI will be a strong focus of the CHAD series of aircraft. In fact this will offer a generation gap advantage compared with fifth gen aircraft. Remember how J-20/F-35 are easy to fly but difficult to fly well? Won’t be a problem on sixth gen since a lot of real time decision making is optimized through the use of AI.

Makes a lot of sense, although I wonder if you couldn't just drop the second crewmember at that point and have an AI WSO/Co-pilot. But maybe I'm overestimating what AI could do in the 2030s or what the purpose of the second crewmember is on the CAC next gen.

 

[leibowitz]

Makes a lot of sense, although I wonder if you couldn't just drop the second crewmember at that point and have an AI WSO/Co-pilot. But maybe I'm overestimating what AI could do in the 2030s or what the purpose of the second crewmember is on the CAC next gen.

The second crew member could be a round tin can that makes beeping noises when it's excited or sad. May come with a holoprojector

 

[EmoBirb]

Round number syndrome. It's a signpost to display progression that's easier to get excited over than some vagueish notion of improving fundamentals

Imo in this day and age efficient supercruise at decent speeds is far more impressive than outright top speed. Even an aircraft like the MiG-31 rarely operates at it's absolute top speed.

 

[siegecrossbow]

Makes a lot of sense, although I wonder if you couldn't just drop the second crewmember at that point and have an AI WSO/Co-pilot. But maybe I'm overestimating what AI could do in the 2030s or what the purpose of the second crewmember is on the CAC next gen.

My guess is that work load for commanding a small air fleet is beyond the scope of AI for now.

 

[Iron Man]

Yes, sustained turns are mainly influenced by those two. If an aircraft's altitude and speed are stable, it means the vertical component of the lift matches its weight and its thrust matches the drag. And the lateral component of lift is what turns the aircraft.
The formula for lift is 1/2 * coefficient of lift * air density * lifting area * velocity^2. An oversized wing means a smaller coefficient of lift is needed which means the aircraft would need a smaller angle of attack while turning. This is important because the coefficient of drag does not increase together with the coefficient of lift as the AoA increases. Airfoils tend to have an optimum point below 10 degrees. Anything above 15 degrees tends to be very inefficient. An example:

View attachment 144418

The goal with the 4th gens was having them efficient while pulling high G forces. They were very draggy while cruising but they had much less drag than the 3rd gens while pulling, let's say, 6 Gs. The third gens needed massive control surface deflections and an AoA near their stall points to generate such lifts. The 4th gens didn't.

A higher thrust helps the sustained turn performance from the other side. It allows the aircraft to be draggier while turning. Everything same, an aircraft with higher thrust would be able to use a higher AoA without losing energy. Thrust to weight ratio is actually not a great representation for this unless one is comparing aircraft of the similar size. Heavier aircraft need less of it because the surface area increases slower than the mass (scaling law). The J-36 having a TWR around 1 at its weight is quite huge.

So there are no practical physical limitations keeping a J-36 from being able to dogfight an F-22? I'm not saying it was designed to do so but just wondering if the large size alone automatically rules out such a hypothetical scenario.

 

[leibowitz]

So there are no practical physical limitations keeping a J-36 from being able to dogfight an F-22? I'm not saying it was designed to do so but just wondering if the large size alone automatically rules out such a hypothetical scenario.

Yes there are practical physical limitations, like the F-22s lack of sufficient internal fuel to ensure enough loiter time ivo the J-36

 

[EmoBirb]

My guess is that work load for commanding a small air fleet is beyond the scope of AI for now.

Totally fair.

I have to admit, while I'm not a huge fan out utilizing AI for warfare, for ethical reasons, I find the idea of having an built-in AI co-pilot/WSO/RIO (whatever) very interesting and quite frankly appealing.

Unless HAL tries to fly you into a mountain or shoots at friendlies

 

[latenlazy]

What’s even the point of Mach 3. I never understood the obsession with it.

Chasing blackbird clout. Rankism.