This is a problem of argumentative logic and perspective. First we’d have to define what “closed the gap” means. After all it’s hard to argue that both China and Russia jumping from 4th generation platforms to 5th generation platforms isn’t closing some sort of gap if the US doesn’t at the same time come up with something new. Then we need to consider what would qualify as hard evidence, for or against, because simply suggesting that there is no hard evidence for does not equate to hard evidence against. Finally, we need to consider what Amiga500 pointed out, which is that the F-22 is a 15-20 year old design, which is to say that it has not moved anywhere technologically since its prototype was finalized.

Now, if by the “development of Stealth Fighters” you mean what might be coming next, we’ll have to wait and see won’t we? After all, to use your standard of hard evidence, we don’t yet know what the US will come up with next and whether Russia and China will match it in a reasonable amount of time, or even if either country might get ahead of the US in those developments.

On a side note, I’m curious to hear what you’re referring to when you mention contrary evidence.

There are a couple of arguments to be made here, as always.

Regarding the age of the F-22, although it is an older design, a number of joint exercises has shown to allied pilots, that stealth really works.

There are published and unpublished reports that indicate that allied pilots had difficulty detecting, tracking and locking on to the F-22.

This is a good indicator that the F-22 as a platform works to an X extend.

based on that, we have to make speculations about the T-50, F-35, J-20 and J-31.

I understand where people are coming from when they say that technology has moved on and hence newer designs are better than older ones, but when it comes to military performance, newer designs have to prove that.

Getting warned IRST is looking for you is not exactly easy… It is passive. It doesn’t emit anything.

I see you are assuming the other side is not emitting anything.. what if they are?

The RCS of an object does not change with range.

What does change is the reflected radar energy that returns to the radar source.

serves me right for being pedantic before.

Yes, you are right, but it changes nothing, just makes it scientifically correct, the F-16 shows up as an equivalent object of 1m² RCS at 100km

I can’t understand why some guys here don’t accept that Russians achieved similar level of RCS on fighter like US.
When 0,1 – 1 sq m value was reported they said it’s on the same level as f-16/SH.
When Davidenko give 0,3 – 0,4 sq m value for F-22 – they said he don’t know the real Raptor RCS.
When we have russian designers value comparsion to the ball (LM like comparsion), the maths didn’t work and value is of course incorrect.
Such a behaviour is characteristic for fanboys.
F-22A is not as new fighter as PAK FA. YF-22 had first flight in 1990, F-22A in 1997, and PAK FA in 2010.
Even if Russian had some deficiency in LO technology, 20 years is a lot of time to do great progress.
But some guys here think that only US has some incredible and magic level of technology, which can not be achieved by any other country through the next 100 years.
In reality LO fighter was shoot down by old Russian SAMs … (for sure it was accidental event).

No. At least speaking for myself, I said the 1m² RCS is indicative of a clean F-16 at 100km and that for some time that was the target to beat.

You need to remember that the first time people had trouble detecting a jet fighter plane (which was not even LO) was when the US fighters came up against the MiG-21.

It was too small for the eye to pin point in the sky and it was too small head on to be picked up by the radars of the era. Hence 1m² at 100km was awesome for a plane like the F-16.
Also be reminded that MALE UAVs have a very low radar signature not necessarily only due to shaping but because they are very small in general in comparison to a fighter plane.

Whooaaa Whoaaa hoooa!

A weather radar won’t detect a single rain drop! Diffraction, numbers of droplet and scattering signal is what makes what they see! It’s not my favorite topic but I am pretty sure you did stumble here. otherwise nice post 😉

Yeah ok, not exactly, but the radiation will scatter off individual droplets and bounce off of them back. The image displayed on the screen as cloud formation is actually comprised of the droplet scattering regions. The radar can even tell you the type of rain and if it’s rain, ice or snow because of their different size.

S-ducts, RCS, “F-22 is better”, “PAK-FA is not a real stealth”, so many years of sterile debate…

More pics!

sigh.. here we go.

The whole VLO principal is based on what is referred to as “clutter rejection region” .. it is something that exists in all DSP parts of a working radar.
Essentially to put it simply, a radar “sees” everything within its effective range, which is dominated mainly by power.

Therein lies the problem. The radar sees everything and that constitutes hundreds of millions of things. Bugs, birds, planes, echoes, droplets of rain, weather formations (sometimes), even background radiation known as noise appears more prominent in certain wavelengths.

The modern DSP behind the raw power of the RADAR, decided which of what the radar “sees” is something that needs to appear legitimately on the radar screen.

hence the DSP will have to “cut” or “reject” a vast number of all the things the Radar sees.

This is the basket the Americans have put all their eggs in. They have made the RCS (or claim to) of their planes so small that looks like a bug to a radar.
A normal radar’s DSP has no choice but to reject this as clutter and hence it doesn’t show up.

A look into weather Radar technology would quickly show you that exist radar systems out there that pick up cloud formations depending on the size of their rain drops or droplets. Universities regularly conduct experiments on LOS detection affected by rain drop sizes, and these sizes are determined by radar.

That is why an RCS discussion is interesting. It is an interesting topic to ponder about and see the engineering choices made and what their impact is on the future usability of said aircraft designs.

photos you can find in google, a meaningful discussion not so much

it says PAKFA has a RCS 15 times smaller than Su-27 and F-22 has a RCS of 0.4-0.3 squared meters according to Alexander Davidenko
Su-27 has a RCS between 10 to 15 squared meters

This is what google translate does with the first paragraph of that link. How accurate is the translation?

“The creators of the fifth generation fighter T-50 (promising aviation complex tactical aircraft – PAK FA) failed repeatedly to reduce visibility of the aircraft radar compared to current Russian Army samples. Such information is contained in the published patent on the “multi-purpose aircraft” Company “Sukhoi” in the illustrations which depicted resembling PAK FA airframe.”