I’ll also point out that the F-22 has fixed, not variable inlets, meaning that DSI is not necessarily a barrier to performance, and the F-22’s designer reported that the F-22 is capable of Mach 2.42+.

The Su-57, in contrast, has variable inlets, which probably compromise its stealth more than the F-22’s fixed and the J-20’s DSI, but suggest greater high-speed engine power.

This is, of course, a standing hypothesis, but it seems to fit the data well. The F-22, J-20, and Su-57 are designed as high-speed stealth fighters. In the J-20 and Su-57’s case, the need for speed has compromised their stealthiness to an extent (and for that matter, if you’re going to repeatedly superheat your aircraft, the stealth coatings are almost a waste of time). The F-35, in contrast, is going in a different direction, where it wants to stay subsonic, and thus IR stealthy, and exploit excellent sensors, both radar and IR.

Mach 3 isn’t such a big challenge, ultimately. The technical specifications on the F-15 show that Boeing has an air superiority aircraft, albeit of the fourth generation, that can achieve Mach 3 speeds.

And as I’ve explained, there are real tactical advantages to having a very-fast stealth fighter, namely in the ability to plonk IR missiles or interceptor missiles further.

I think that’s the entire point of Sino-Russian reduced stealth in LO or VLO. The point isn’t to completely evade detection, or to end up being stealthy enough to get into a dogfight where you die to HOBS-missiles anyways, but the point is to be stealthy enough to defeat the smaller radar seekers on medium-range air-to-air missiles. Your opponent may see you, he (and it’s usually a he) may even be able to track you, but he won’t be able to hit you.

Think drag, not thrust. Even in the Su-57’s case, it has a slightly higher fineness ratio than the F-22, as well as a higher wing sweep than the F-22. The F-22 is generally believed to have a Mach 1.8 supercruise, but it’s also rumored that it’s achieved Mach 2 supercruise. Remember, the Concorde was supercruise capable with only a .4 T/W ratio. The MiG-25, likewise, was a 20k ton empty-weight fighter that could achieve Mach 3 with engines producing only 100 kN of thrust each.

Just a question. Using a linear drag equation (as opposed to detailed non-linear, i.e, Cd drops as speed increases), the Su-57 seems to be able to hit a max speed of around Mach 2.7 or 2.8.

Is this the real secret of the Su-57? I.e, it’s “stealthy”, in terms of being LO, but it’s willing to sacrifice stealth for speed?

We know with the F-22, it’s supposed to be able to reach Mach 2.45, presumably at altitude, but it avoids hitting high speeds due to damage to composites and stealth coatings. With the J-20, we recently received a report that it’s capable of a Mach 2.9 max speed. With regard to the Su-57, the report of Mach 2.1 supercruise implies that it should be able to hit Mach 2.76 (as a minimum).

Is that the actual secret of the Su-57; it’s less a replacement for the Su-27, and more a replacement for the MiG-31?

That’s to say, let’s say the Su-57 is engaging F-35s. Since the F-35 is relatively slow and unagile, it has a relatively low NEZ factor. The Su-57, once the F-35 has been detected, scoots rapidly at the F-35, reaching its maximum speed of Mach 2.7, then loosing R-74 IR missiles at the F-35, hopefully from outside its targeting, but not detection range. It then zoom climbs, attempting to shed off as much speed as possible, then dives to resume its maximum speed, outrunning retaliating AIM-120s.

I’m also wrong about the J-20 vs F-22 scenario, the Block II Sidewinders have a reported range of about 40 km. Actual range is likely to be closer to 50 km. There’s also the FY-80, which has a rumored range of 80 km, but it’s an export missile and the 80 km is only rumored. The PL-10 ASR is only supposed to have around 20 km of range.

Hmmm, hold on a bit, there’s a claim that the PL-10 ASR can reach 60km from Chinese television.

https://www.youtube.com/watch?time_continue=159&v=7uyr4gmPhFs

Need to check out the reliability of the claim.

@Haarvala:

The last time the Chinese weren’t getting swatted out of the skies was WW2, where Nationalist Chinese pilots were fighting alongside the Americans in boom-and-zoom jets. It seems to have rubbed off; when the Russians put the Su-27s up for sale, the Chinese didn’t actually want it and wanted the MiG-25s or MiG-31s instead, but the Russians didn’t want to sell them, as they were nuclear-capable or could be retrofitted to such.

If you look at the fineness ratios of Chinese fighters, they seem to have a fetish for speed, and moreover, most of their aircraft are well-radared for the technology level. Doctrinally, they don’t seem as affected by the cult of the dogfight as the Americans or the Russians, and it’s to their benefit given developments in HOBS.

Re: QuantumFX:

When it comes to F-22 vs J-20, you’ll have to remember that when it comes to fights between stealth jets, it’s actually the missile seeker that’s the limiter. Take the AIM-120D, for instance. It has a nice 180 km range, which, when combined with the F-22’s stealth advantage, can allow the F-22 to put the J-20 within NEZ before the J-20 can see it. However, the problem is, the AIM-120D is X-Band and is far smaller than the APG-77. If we assume the APG-77 can track the J-20 starting at 40 km, given the J-20’s relatively poor stealth, the AIM-120D’s seeker will likely need 20km to do so. So the F-22 will have to flash its radar at the J-20 to maintain a data-link lock, ruining the element of surprise, and cuing the J-20 to launch its own PL-12s.

There’s also the fact that the J-20 is actually better sensored than the F-22; the J-20 has EODAS, whereas the F-22 has no IRST systems onboard at least until an MLU. Especially if the F-22 opts to supercruise, it’ll end up being lit up on the EODAS simply from skin heating.

Also, via SDF, we have a claim that the J-20 can achieve 3000 km/h speeds. It’s not that impossible; the J-20 was designed for supercruise with only 174 kn of thrust. The VTech drag estimates show that the J-20 can achieve almost Mach 2 supercruise due to having a very low total drag. Increasing engine power from 174 to 280 would yield a 27% increase in speed, or Mach 2.5, and a further boost to 360 kn would yield Mach 2.88 speeds.

As a stealth fighter, this speed would only be useful when it comes to escape; the Mach 3 would blow through the stealth coatings and light the J-20 up on IR sensors. Still, it does help to explain why the Chinese half-assed it on the rear aspect stealth; if you can vamoose reasonably effectively (NEZ is reduced to 50 km or less), why bother with rear stealth?

For the speculated weight (16000kg), the J-20 actually looks as though it has excellent T/W and wingloading at 60% fuel, although still behind the Eurocanards and lagging the F-22 in T/W.

If the speculated weight is accurate, when the WS-15 becomes mature, the J-20 will likely gain additional wing area in later versions, so IR stealth is improved not by moving the engines into the body, but by moving the body around the engine.

Re:J-15, the J-15 is a 4th gen aircraft that’s going to be pretty obsolete against F-35s. It has its advantages; it’s more capable than the Super Hornet given that it’s built off a Flanker base, not a Hornet base, but who cares when both the SH and J-15 are obsolete. It is possible that the Chinese naval aviation program is floundering, but a few things:

first, the Chinese are just starting with naval aviation; they don’t have experience and you can’t tell whether accidents are because the carrier sucks, the aircraft sucks, or the pilots suck. Second, in an actual military scenario, the Liaoning is going to go down extremely quickly; given the relative strength of the USN and the PLAN, it’ll simply get overwhelmed by sheer numbers and other tools, such as the DF-21D and DF-26 are much better suited for anti-carrier ops. The fundamental role of carriers is as coastal bombardment or amphibious landing support, and the most likely target (Taiwan) is actually close enough to the Chinese mainland that you don’t need a carrier.

So you have to think of the Chinese carrier fleet more as play / training than as actual use.

Also, one other thing. The J-15 is supposed to have AESA radar, while the Su-33s, iirc, are either Pulse Doppler or PESA. The J-15s, if they work as designed, are actually superior to the Su-33s by virtue of electronics.

You have to understand, the claim is 3 m^2 detection range, when tankers, AEW&C, and bombers can easily hit 20 m^2 and thus be detected at a longer distance. The ground-based target in the other video is a bleeding 50,000 m^2 warship, for christ’s sake.