Su-57 Stealth Fighter: News #6

GarryB wrote:I would think if they developed stealthy sawtooth engine nozzles that they could fit them to either engine... as both would probably benefit wouldn't they?

There is more to engine stealth than just the nozzle (the F-35 has blockers for instance), but I guess it would help and see no reason why it would not be compatible with the older engines...

Stealthflanker wrote:Isn't the radar blocker already part of the plan from the day 1 of Su-57's inception ?

Correct

This is the patent with the radar blockers, the cross section is taken right before the compressor:

From Army 2020

Haters will claim that not only russian ships, but also russian planes generate huge plumes of "smoke"

Isos wrote:

kvs wrote:

william.boutros wrote:

Isos wrote:

This image settles that the fans will be visible and that blockers need to be installed.

Only if the radar is located above the plane of the jet.   For any ground radar they are invisible.   As for being detected in
the air by other jets, that was never the objective of stealth.

It's the opposite. If the enemy radar is above the su-57, its signal will bounce on the wing and never go inside the engine.

If it is bellow the su-57, the signal will go inside but will bounce ten times before coming back.

The only time the radar's signal will go inside and bounce on the engines is when the radar is at the same altitude.

But even then, su-57 will be supercruising so the air intakes of the engine will be smaller, and the radar blocker will have two fonction. From what I understood it will be similar to this drawing with the radar blocker being the movable part in front of the engine.

That graphic is totally irrelevant for the Su-57. It misses completely the scoops at the base of the intakes. So the little zig zags will not be
easily zagging back to the line of sight of the radar. And in fact, the radar beam will bounce off the scoop bottom before it gets inside the intake.

Opposite.

Isos wrote:I shared the graphic to show that the intake must be smaller at supersonic speed for air flow not for radar.

Su-57 will have a radar blocker that will also control de air flow. And it will be placed like the moving thing above the "auxilliary door" on the graphic.

But yes that graphic has nothing to do with su57. It's about Concorde.

Those are the variable ramps of an adjustable supersonic intake, they have nothing to do with radar blockers. The trajectories are the supersonic shocks. Radar blockers are placed right before the engines and were represented in the patent as a mesh. Some images of real radar blockers below:




As you can see, they can share functions with the inlet vanes of the engine. And given modern compressor blades are composite, the actual return from them can be a far cry from what it would be expected in legacy designs...

@Isos:

I see no conflict between what I posted and the patent, in fact it specifies a series of possibilities on how to implement the blocker, with a mix of radial, cylindrical and mesh structures. Maybe I misunderstood you referring the variable ramps as the blocker?

The fan art you post looks related to mesh screens for take off, they seem too thin, forward positioned and movable, just like the screens in the Flanker. IMHO this is not what the blocker looks like, it is in place all the time from what we know and very close to the engine.

My understanding is that the front blades of the engine in the Blackjack have RAM coatings too to reduce radar return...

They know what they are doing...

Isos wrote:Again that's just what I undertood. I never saw anything in english or real pictures of them.

Anyway the design is already hiding half of the engine. But like Garry said the little amount of signal going in will bounce multiple times in the intakes made out of stealthy design and will be absorbed so much that it won't have any power to go back to enemy radar. And that's only if the enemy radar is at the same altitude which won't be the case most of the time and the su-57 can just go bellow 500m and hide the intakes with the wings...

Fair enough. I agree the compressors only get exposed in certain conditions, but with the blocker they freed the pilot to fulfil the mission without caring about that or being tactically limited, I think it is the right thing to do

RCS measurement of an Su-57 model in Voronezh.

I found this image laying around in my harddrive but i forgot where i got it in the first place.

When is this photo from?

Unlike prototypes and even serial, this mock-up has a serrated radome... Did they find it unnecessary?

jaguar_br wrote:When is this photo from?

Unlike prototypes and even serial, this mock-up has a serrated radome... Did they find it unnecessary?

It's been sitting on my hard drive for maybe 1-2 years now. Anyway the model being tested is the static T-50 KNI.

Regarding serrations It's not necessarily need to be visible in final production. It can be internal.

Stealthflanker wrote:Regarding serrations It's not necessarily need to be visible in final production. It can be internal.

In fact the radome for the Su-57 appears to be different to that of other models until now. AFAIK serrated edges are needed where there is an electrical discontinuity in the fuselage, those panel covers that do not need permanent access can be closed so that continuity is not lost. Maybe the increased reliability of the AESA makes frequently accessing the radome and hence serrated edges unnecessary?

LMFS wrote:

In fact the radome for the Su-57 appears to be different to that of other models until now. AFAIK serrated edges are needed where there is an electrical discontinuity in the fuselage, those panel covers that do not need permanent access can be closed so that continuity is not lost. Maybe the increased reliability of the AESA makes frequently accessing the radome and hence serrated edges unnecessary?

It would still be needed mainly to give better sidelobes for the antenna and perhaps part of edge treatment against structural mode RCS. There still be discontinuities present however as the radome and airframe is made out of different materials. But this can be handled by something like RAM tapes or coat to weaken or absorb the diffraction RCS. Same goes for the canopy supporting frame.

Stealthflanker wrote:It would still be needed mainly to give better sidelobes for the antenna and perhaps part of edge treatment against structural mode RCS. There still be discontinuities present however as the radome and airframe is made out of different materials.  But this can be handled by something like RAM tapes or coat to weaken or absorb the diffraction RCS. Same goes for the canopy supporting frame.

Well, I am now aware I was oversimplifying, obviously the radome is transparent so there is no way it could have electrical continuity with the rest of the fuselage if it was not a composite structure... but looking the RCS measurement model and comparing the radome with the models we know it can be appreciated that it may be as you say, an internal detail. The radome joins the fuselage in a square angle and it would create return if the rear part of the radome did not create an impedance adaptation. But then, electrical continuity must be provided, so I guess my point remains that it is a part that is not meant to be opened frequently. I think there was an old development by some US manufacturer to create covers with special gasket materials that guarantee conductivity without the need of taping or coating, that may be another option.

Could you further explain the part about side lobes and structural mode RCS? I didn't understood that.

As to the canopy, AFAIK it is handled as a continuous conductive surface isn't it?

BTW, do you know why the Su-35 and Su-57 (and other modern planes) have some strakes or longitudinal lines around the radome, is it related to removing static charges in absence of the pitot tube?

Combat Approved, finally in English: the Su-57 especial

https://www.youtube.com/watch?v=UkHRZ8FZGN4

LMFS wrote:Combat Approved, finally in English: the Su-57 especial

Ever wondered why they gave it the number 57? How about this?

at 20:30 the guy says "if you add 22 and 35, you get 57"

A good image of the radome and the internal serrated edges: