Sukhoi Su-57 / T-50 / PAK FA - flight testing and development Part II [2012-current]

[Deino]

In his 63rd, he managed to withstand 9G for 20 sec. Man hard like a rock.

''Bogdan Sergey Leonidovich. Honored Test Pilot of the Russian Federation, Reserve Colonel, Hero of Russia (2011). Since 2000 - Head of the Flight Service of the Sukhoi Design Bureau. Born in 1962 in the city of Volsk, Saratov region. He served in a number of regions of Russia, in Mongolia, and took part in the operation in Syria.He likes to joke that he has been afraid of heights since childhood. Regularly goes to the fitness club, swimming pool and gym. Plays hockey and football. Climbed on Elbrus.''


View attachment 752833

Sorry, and even if I admire this man as a pilot is this really relevant to the topic?

Praising a certain pilot for his fitness at a certain age has nothing to do with the Su-57 and even more - like several of your posts - smell a lot like too much pro-Russian bias!

 

[QuadroFX]

Agree.

 

[AGS-1787]

I find it strange Sukhoi is still using a HUD when they have apparently build a HUD into the visor of the helmet. I understand the need of a HUD on prototype aircraft and the serial models when the helmet is still in development but it would be strange if they keep the HUD after the helmet is ready. Seems like it would be very confusing and messy for the pilot when two HUDs are overlapping plus the cost and weight is unnecessary. Plus removing the HUD gives a better field of view as it takes up a lot of cockpit real estate.

There was a recent f-35 accident where a bunch of screens went bad, including the helmet display due to lighting strike. The only available screen was a tiny back-up hsi. The pilot was so confused by the screens messing up that he ejected. It might be for redundancy. I figure when the pilot is looking straight to the hud; the imagery from the helmet should fade out. Unlike the rendering.

 

[AGS-1787]

Gloss black, bright green and bright white is an effective camouflage? Or bright white and grey like on SU-24s? Sukhoi might as well put a disco ball on their aircraft and paint them pink. I have seen Sukhois in real life and I have seen F-15s, Mirages, F-16s, F-18s, ect Russian aircraft are much easier to see. I have also always been into art so I understand perfectly well how colors work against backgrounds.

Which one of these two aircraft blend in better with the sky, the bright green/white/black SU-34 or the grey Rafale. Sukhoi does NOT use naturally occurring colors for their paint schemes nor does Sukhoi use any soft blending or natural texturing. Every one of Sukhois paint schemes (besides the SU-30SM) uses bright, glossy, not naturally occurring colors with rough edges and too much contrast.

I understood the white coloring for su-24, tu-22, tu-160 was to help with the nuclear flash. It was not just for show. I think the Russians are the least inclined people to do flashy camouflage; they still use that light blue colors in their cockpits based on ergonomic studies. Sukhoi has used some flashy camos for their demonstrators like su-35,37. Regarding the su-57; I don’t know how effective it is for missile sensors; but they seem to have used for their production aircraft so they might have a reason other than trying to make it look cool.

 

[AGS-1787]

Do you know the story behind eggplant camo and who proposed it, to start with? I believe you don't.

Flateric what was the story behind it? I never heard of it. I was under the impression that it was for navy aircraft

 

[Galaxy]

There was a recent f-35 accident where a bunch of screens went bad, including the helmet display due to lighting strike. The only available screen was a tiny back-up hsi. The pilot was so confused by the screens messing up that he ejected. It might be for redundancy. I figure when the pilot is looking straight to the hud; the imagery from the helmet should fade out. Unlike the rendering.

That is what i figured and what makes sense. If they are planning on keeping both then at least the HMD would turn off when looking forward otherwise it can be discombobulating.

Still if lighting strikes an aircraft and it fries most of the electronics it goes to reason both the HUD and HMD will be inoperable so in my opinion it’s just a waste of money. Moreover, I believe multiple redundancy systems are already built into the HMD.

There was an interview with a EF-2000 test pilot and he spoke about the EF-2000s future cockpit and the removal of the HUD and its benefits one of which was the ability to increase the size of the LCDs and I believe he mentioned visibility too.

It would be really nice if the Russian helmet incorporated some features of the Striker II such as showing a 3D dome type image of air defense threats. Very useful for the pilot to navigate i between gaps in air defense.

Here is an example:

 

[Elysium]

I find it strange Sukhoi is still using a HUD when they have apparently build a HUD into the visor of the helmet. I understand the need of a HUD on prototype aircraft and the serial models when the helmet is still in development but it would be strange if they keep the HUD after the helmet is ready. Seems like it would be very confusing and messy for the pilot when two HUDs are overlapping plus the cost and weight is unnecessary. Plus removing the HUD gives a better field of view as it takes up a lot of cockpit real estate.

Eh, I think these AR helmets are a sidegrade (or even downgrade) compared to regular HUDs and 2D screens. I used to work developing software for radiologists, and a couple of years ago everybody was saying 3D and AR/VR is the future, and nobody is going to stare at traditional sliced MR images, everybody is going to view these 3D scans as 3D reconstructions through AR glasses.
Guess what?
Other than an enthusiastic minority, doctors saw no point in this and continued to look at cross-sectional slices through boring old 2D monitors.

 

[Galaxy]

Eh, I think these AR helmets are a sidegrade (or even downgrade) compared to regular HUDs and 2D screens. I used to work developing software for radiologists, and a couple of years ago everybody was saying 3D and AR/VR is the future, and nobody is going to stare at traditional sliced MR images, everybody is going to view these 3D scans as 3D reconstructions through AR glasses.
Guess what?
Other than an enthusiastic minority, doctors saw no point in this and continued to look at cross-sectional slices through boring old 2D monitors.

Those helmets provide quicker data, better field of view, and new capabilities such as visualization of air defense threats. There is no question they enhance survivability and situational awareness. It’s like saying old flip phones are better than the newest iPhones or dial up internet is better than 5G.

When people are used to doing things a certain way it’s hard to break old habits. I too refused to adapt to new technology but then changed my mind when familiar with new systems.

 

[DWG]

I find it strange Sukhoi is still using a HUD when they have apparently build a HUD into the visor of the helmet. I understand the need of a HUD on prototype aircraft and the serial models when the helmet is still in development but it would be strange if they keep the HUD after the helmet is ready. Seems like it would be very confusing and messy for the pilot when two HUDs are overlapping plus the cost and weight is unnecessary. Plus removing the HUD gives a better field of view as it takes up a lot of cockpit real estate.

It depends what you're showing on them. Symbology can be either fixed in relation to the aircraft, fixed in relation to the external world, or fixed in relation to a manoeuvring target. When it's external and off to the side, the HMD is the obvious display system. When it's fixed in relation to the aircraft - things like the velocity vector, then there are two options - display virtually fixed symbology in the HMD, or fixed symbology out of the HUD. External and to the front, you need to decide which system is going to show it, because both is asking for confusion.

But symbology isn't the only thing shown for the pilot, we also have FLIR imagery. The HMD is the only game in town for looking through the aircraft F-35 style, but for fixed forward imagery such as a Nav FLIR, is the HMD up to displaying at the necessary resolution and precision? If it isn't, then you may want to duplicate things with a higher resolution HUD.

Or it might just be a conservative approach to redundancy.

 

[Elysium]

Those helmets provide quicker data, better field of view, and new capabilities such as visualization of air defense threats. There is no question they enhance survivability and situational awareness. It’s like saying old flip phones are better than the newest iPhones or dial up internet is better than 5G.

When people are used to doing things a certain way it’s hard to break old habits. I too refused to adapt to new technology but then changed my mind when familiar with new systems.

A better and more direct analogy would be a VR headset vs a laptop screen. VR got introduced, wowed everyone, then everyone decided to go back to boring screens. Please refrain from using poorly constructed analogies in the hope of quickly winning arguments in the future.

All of that information can be conveyed just as well through that big 2d touchscreen in the middle of the cockpit, and in a much more informative, although less flashy manner.
Technological pragmatism wins over technology for technology's sake.

These dome type images you showed would be readable much more accurately and to a greated distance around the aircraft on a 2d map-type screen.

 

[Avimimus]

I might be a bit conservative - but when looking at the FLRAA proposed cockpit layouts with one giant touch screen for all of the cockpit instruments and interfaces - then looking at the retention of some analogue dials and switches in 1990s Russian designs... I'd feel more comfortable with both the tactile feedback of actual switches/buttons and the redundancies that exist in having multiple separate instruments.

I get that the headsets offer significant improvements to situational awareness (e.g. FLIR imagery displayed in the actual direction the sensor if facing, ensuring the HUD is visible no matter where the pilot is looking), but I'm not sure it has to replace all other sources of information.

 

[Willythekid]

...

 

[Squirrel]

​

I understood the white coloring for su-24, tu-22, tu-160 was to help with the nuclear flash. It was not just for show. I think the Russians are the least inclined people to do flashy camouflage; they still use that light blue colors in their cockpits based on ergonomic studies. Sukhoi has used some flashy camos for their demonstrators like su-35,37. Regarding the su-57; I don’t know how effective it is for missile sensors; but they seem to have used for their production aircraft so they might have a reason other than trying to make it look cool.

M.Strelets told some details earlier ... From 15:20

View: https://www.youtube.com/watch?v=aDXNDA5xuS4


@Deino

About pilots on this topic...I think that is not bad to mention some test pilots ( Sukhoi,KnAAZ or even military from 929 GLITs from Akhtubinsk /4th TsBP-PLS from Lipetsk ), because they certainly can tell us interesting details and info about Su-57, especially in the interviews. If we can write about pilot's helmets, maybe we shoud write about test pilots and their stories.Of course ,in that comment there was no data/info about Su-57 from S.B. ,sorry for that.

 

[haavarla]

Those helmets provide quicker data, better field of view, and new capabilities such as visualization of air defense threats. There is no question they enhance survivability and situational awareness. It’s like saying old flip phones are better than the newest iPhones or dial up internet is better than 5G.

When people are used to doing things a certain way it’s hard to break old habits. I too refused to adapt to new technology but then changed my mind when familiar with new systems.

Yeah about that.... IF they work as advertized. L M would want you to strongly believe that.
But there is the issue of glitch, latency, software bug and system crash. Take your pick, or pick them all and you can't go wrong.

 

[yeetmahboi]

Yeah about that.... IF they work as advertized. L M would want you to strongly believe that.
But there is the issue of glitch, latency, software bug and system crash. Take your pick, or pick them all and you can't go wrong.

And if you don't advance, your progress flatline.
New tech will be adopt. Early on, not a lot of things "work as advertised". Eventually fixes will be rolled out.

 

[haavarla]

And if you don't advance, your progress flatline.
New tech will be adopt. Early on, not a lot of things "work as advertised". Eventually fixes will be rolled out.

I get that.
But the whole helmet capability has been for yeeeeaaars hyperboled. we are not anywhere near what they want it to be. I was around here last two decade on various forums. Whish i could put up some of the riddiculous claims back then.

 

[Galaxy]

Yeah about that.... IF they work as advertized. L M would want you to strongly believe that.
But there is the issue of glitch, latency, software bug and system crash. Take your pick, or pick them all and you can't go wrong.

With that attitude why even bother developing anything? Might as well just get Mig-23s out of storage then or just drive 50 year old cars since they are simple. Also just because some US/European systems have/had some bugs doesn’t mean Russian systems will have all the same issues especially considering how western arms manufacturers over complicate systems to squeeze maximum profit from buyers and often use unproven or never before used technology that takes longer to mature.

Even if the Russian helmet does have issues, what is the problem? Every system ever created has had issues, that is why it takes years of R&D and testing to find out potential problems and correct them. If the Ukraine war taught us anything, it’s that the Russians are very adaptive and can improvise and adapt quickly.

The Russians have three years fighting Ukraine and NATO (and yes they are fighting NATO as NATO admits to providing weapons, global intelligence, training, targeting information, planning, logistics, repairs, ect) the end result is that Russia has faced Patriots, NASAMs, S-300s, F-16s, upgraded MiG-29s, SU-27s, SU-24s, Storm Shadows, ATACMs, HIMARS, various radar systems, jammers, Abrams, Leopards, ect. The Russians not only experienced these threats but adapted and learned from them…literally. This is, the Russians got to examine fully intact or partially intact NATO systems, they have had opportunities to experience NATO electronics warfare systems as well as see how comparable Russian systems work against the adversary, the Russians have gathered intelligence on what frequencies NATO systems operate, their flight profiles, weak points, and tactics.

These are not easy systems to overcome especially with NATO in the background helping make the systems more deadly. With that said the Russians have more knowledge in three years than they had in 50 years on understanding NATO systems and how to learn from and counter them.


What I’m trying to say is that the Russians have experienced these systems and are now adapting their weapons systems to counter the threats so even if there are glitches early on it’s still worth it, if these systems such as the helmet can visually show the pilot where the threats are then it’s a huge win.

Imagine the survivability if the pilot can see a Patriot and then visually see air defense gaps in Patriot systems and then even have the helmet lock onto and show incoming missiles or even ‘look through’ the aircraft (use cameras slaved to the aircraft/helmet). Imagine the pilot not needing to take his eyes off a threat and having better efficiency.

It’s like the AL-51 with flat nozzles, I’m willing to bet that the Russians were never seriously considering using flat engines until after the Ukraine war. After all that engine was already tested on a T-50 in 2017 but with round nozzles and yes I’m aware the Russians played around with flat nozzles since 1989 but it was never a serious idea. Maybe I’m wrong and they planned the flat nozzles well before 2022 but perhaps it was meant for a future aircraft like a heavy bomber? Point is, once you face a serious opponent you start to be creative and think outside the box and do things you normally would not. Do flat nozzles pose a challenge? Yes but they also drastically lower RCS and IR emissions which is worth any drawbacks in cost or minor thrust loss, same with the helmet, yes it may have glitches and cost more but that is worth it.

The other option is possibly having SU-57s shot down, pilots killed or captured and NATO examining the wreckage while interrogating the pilot for classified information. Not only would it be a propaganda blow but the Russians would be humiliated and it would be expensive. It’s like the Russians using dumb bombs early in the war, they lost a lot of aircraft and pilots by being cheap and frankly stupid by using expensive and sophisticated aircraft to do a job that a WW2 aircraft could do. They finally adapted by outfitting old bombs with glide kits and satellite navigation. As they finally figured out that it was more cost effective and safer to use glide bombs than losing entire squadrons worth of aircraft to drop dumb bombs.

 

[AGS-1787]

So they already addressed the rear radar visibility with the new exhaust, are they planing on making the cockpit glassing frameless? Is that even an issue?

 

[Galaxy]

So they already addressed the rear radar visibility with the new exhaust, are they planing on making the cockpit glassing frameless? Is that even an issue?

They had 14 years to address the canopy issue… it’s final and yes it is an issue for two reasons. 1, the two pieces causes a discontinuity with three extra seams from the canopy bow plus screws holding the bow in place and 2, the shape itself is not ideal. There is a reason the F-22, J-20, F-35, J-35, KF-21 and TAI TF have a trapezoid style shapes.

Maybe in a future upgrade it will change but I doubt it. In my opinion it seems engineers are clashing, you have forward thinking engineers that push for modern design and then you have old fart dinosaurs that only care about cost and maneuverability for air shows or at the minimum they can’t except that times are changing. It only makes sense, I can’t see why else some panels are serrated while others are not or why some parts of the aircraft looks modern while other parts look not so modern.

 

[AGS-1787]

I think the framed cockpit is a compromise they made, If Google Translate is correct...they chose the conventional design for strength, pilot protection, to be able to achieve high speeds and sustain them. But I was wondering if they were working on a new design since the su-27 at first had the same sliding design and later they changed it.

 

[Galaxy]

I think the framed cockpit is a compromise they made, If Google Translate is correct...they chose the conventional design for strength, pilot protection, to be able to achieve high speeds and sustain them. But I was wondering if they were working on a new design since the su-27 at first had the same sliding design and later they changed it.

That sounds like archaic thinking from engineers that probably date back to and are stuck in the Cold War. Not sure what they would mean by strength, do they think that bird strikes happen often? Typical Soviet thinking, where they spend time, money and effort on something trivial that means little when it comes to capabilities (green cockpits, ekranoplan, ect). Ask any pilot if he wants a stronger canopy or one with lower RCS that has better battlefield survivability and 99.999% will want a canopy/aircraft with lower RCS.

Engineers should worry more about missiles strikes than bird strikes and less about obsessions with maneuvering at the cost of RCS.

There may be one way an SU-57 may get a single piece canopy and that is if India decides to get back into the program by infusing billions into the program by demanding a more modern canopy with lower RCS, but that is unlikely now as the west “rules based order” is threatening every country for having any relations with Russia and especially threatening countries that have ties militarily or economically to Russia; but remember, the west claims no country should threaten or dictate terms to other countries and that every country should be free to have relations with whoever they choose….unless you are Russia, China, Iran, North Korea, Belarus, ect then….well it’s complicated and it’s best not to ask “exceptional” countries too many questions.

Humor aside, the only real problems a single piece canopies can create are weight issues but that is still insignificant when you factor the weight of aircraft itself. The other problem is in difficulty in manufacturing but so many countries have already created single piece canopies that I don’t even think it’s even an issue. If Russia can create en entirely modern aircraft, and AESA radars and new avionics and missiles and engines then something as simple as a canopy is nothing.

 

[Null]

Maybe in a future upgrade it will change but I doubt it.

Well if they go this route with the Su-57 it would

 

[Galaxy]

Well if they go this route with the Su-57 it would
View attachment 753076

That is an unmanned drone based on SU-75 and has nothing to do with the topic of SU-57 or its canopy

 

[TMA1]

I think null is saying that sukhoi is thinking forward with the newer designs and that the su-57 may ultimately take on some major improvements even beyond megapolis.

 

[Galaxy]

I think null is saying that sukhoi is thinking forward with the newer designs and that the su-57 may ultimately take on some major improvements even beyond megapolis.

It’s too late in the game for major improvements, the SU-57 is already in production. It’s a huge waste of money to start implementing changes now. Although the SU-75 has superior stealth characteristics which is odd considering the SU-75 is just a side project of Sukhoi with no government funding.

 

[PeregrineFalcon]

Rather than using Soviet tables estimating the F-15C, the actual manual is available. The F-15 with the OWS is clearly able to pull 9g without any placard limit underneath. Only without OWS, F-15 is placard limit to 7.33g.
View attachment 752777

Note for the OWS, there are no "peacetime" g-limits. I don't know where the Soviets got the numbers for their tables, but the F-15 with OWS can pull 9g up to a certain weight


F-15 flight manual does not have any ITR charts, only STR charts so don't know where you're getting those turn numbers from. There are no published E-M diagrams that shows max turn rate for different Ps like seen for F-16C. Especially if numbers are from the Soviet estimates, those charts are again estimates which are off. This is F-15C turn rate with original F100-PW-100, which is actually weaker than the F100-PW-220 that most are equipped with (the F100-PW-220 usually have dynamic thrust equal to 102% engine trim for F100-PW-100).

Soviets actually overestimated the F-15 performance, the real EM numbers are worse, and I don't know the reasoning behind their estimates and certain limitations.
The ITR numbers for the F-15C are coming from the aeronautical engineers that have available data for such calculations, including the planes Clmax, which is 1,1 if I remember correctly (I know that the Su-27 Clmax is 1,85, which is considerably higher, and that is one of the main reasons for superior ITR and STR performance).

F-15C with the F100-PW-220 is also heavier so the slightly higher dynamic thrust numbers are negated by additional weight.



For example, Su-27 at 20 tones (with 4 missiles) can sustain 9G at 10000ft, but the clean F-15C with F100-PW-220 and 16,7 tones can't (it can sustain around 8,5G's).
Again, in this configuration F-15C has superior T/W ratio and lower wing loading, and still, it has worse performance which only highlights the aerodynamic efficiency of the Su-27 layout.

But the F-15 aerodynamic configuration only has superficial similarities to F-22, it may look similar but there are no sharp LERX to generate strong vortices, so this kind of comparison not useful they have quite different Cd and Cl curves and characteristics. So not going to take these numbers as indications of anything.

You have claimed without any data that the LERX-blended wing body layout is going to increase the overall drag of the plane in a turn.
I have given you the real-world example where we have same-generation, same-class fighters and how they compare with their respective aerodynamic layouts. You can't find better example than that!
F-22 is continuation and improvement of the F-15 configuration (no LERX, close coupled engines), and so is the Su-57 in relation to the Su-27 (LERX, blended wing body, engines placed apart).

F-22 doesn't have LERX, it has sharp inlet chins which generate vortices, but the effective lifting surface of the chin is miniscule in comparison to the real LERX.

F-15 sharp inlet edges also generate vortices, along with the wing root extension:

I hear the argument from patent about able to recover from TVC malfunction but that's not even relevant failure mode of F-22, the nozzle when in failure mode always forces itself in neutral position and F-22 control surfaces are specifically sized to recover from any condition TVC puts it in. Maybe if F119 has gimbal TVC like AL-41F1 that can lock at a certain position it would be more relevant but that's not how the nozzle is designed.
A design feature useful for one aircraft is not always applicable to another.

It is understandable that in the case of TVC malfunction nozzles are going into neutral position, that is a safety measure for all TVC nozzles, no matter the type of the nozzle. If the nozzle locks up in any position, other than neutral, there is hardly any measure that could save the plane.
Can you provide the data for the conditions where conventional F-22 aerodynamic controls (horizontal tails) can recover the plane from the post stall region?

I'm pretty sure that Sukhoi engineers know more than you about this subject, and about specific conditions they have in mind when they made the claim.



From this chart, we can see that even with the TVC, the F-22 has rudimentary roll/yaw control at 60 degrees AoA.
At that AoA, the plane cannot perform a full 360-degree roll (the Su-57 can, with roll rates that are significantly faster) because the aerodynamic control surfaces lack control authority, even with the help of the TVC that is controlling the pitch. Without TVC, the F-22 is positioned between the F-15 and F-16 in this regard.
There is an objective reason why the aerodynamic control surfaces placed in front of the center of gravity have better authority and controllability at high AoA. According to Sukhoi's chief test pilot, Юрий Ващук, only two Russian operational planes can achieve supermaneuverability without TVC: the Su-30SM and the Su-57. The Su-35S is more maneuverable and a much more capable dogfighter than the Su-30SM, but without TVC, it cannot exploit the post-stall region.

With addition of the canards Flanker series has unlocked the post stall region in totally controlled manner:

View: https://www.youtube.com/watch?v=AYKWMXAfKRA&t=1s


The plane in question is a former Su-37 that had a new, improved FCS installed; however, the engines with the TVC were removed and replaced with the standard AL-31F. That is the reason they have used the old Su-35 nomenclature. The same improved FCS is used for the Su-30MK/SM versions, and that plane can also perform all those maneuvers without TVC (other flanker versions can't).
We can see that even without TVC, the Su-35 can match the F-22 in the post-stall region, and in some instances, it even surpasses it. The Su-57 can also perform all those maneuvers without TVC, but with the TVC engaged, the plane has faster initial rotational rates and better controllability.

Papers from Song Wencong can explain about design rationale behind J-20, not useful to extrapolate the performance of other aircraft with different geometries and shapes.

Actually, in that paper it was generalized about the types of control surfaces based on the relative position of the pitch control surfaces with respect to the aircraft's center of mass, and they were categorized in to the positive load pitch down control surfaces, and negative pitch down control surfaces.
As seen and tested, control surfaces placed in front of the Cg do have advantages under high AoA/post stall conditions.

Reasoning is clear, because your argument seems to be that because of Su-57's wide fuselage, the lift distribution is less on the wings and more from the centroplane to reduce peak bending moment. Yet the overlay of the planforms between F-22 and Su-57 aren't dramatically different from each other.

My argument is in agreement with the Sukhoi statements:

RU2400402C1 - Multimode high maneuverability aircraft of integral aerodynamic configuration - Google Patents

FIELD: aircraft engineering. SUBSTANCE: proposed aircraft comprises airframe wherein central part 2 smoothly fairs with backswept outer wings 3, nose part 1 and tail part 6 wherein all-moving vertical tail 4 and horizontal tail 5 are arranged. Canopy 10 is arranged in airframe hose 1...

patents.google.com

EFFECT: uniform distribution of air load and increased load bearing qualities of airframe.

It is less useful to look at the planform of the plane to make such conclusion, it is much more useful to look the planes from another perspective:



Su-57 is basically a flying wing with inlets and engines slapped beneath it.
F-22 and J-20 fuselage layout is basically the same. Big, boxy midsection with enormously long and curved air ducts that take up most of the useful space. Chinese had strict requirements for long range, and it is obvious why the fuselage is so much bigger/longer compared to both, F-22 and Su-57. You can't go around it if you apply the same configuration F-22 does.

And whatever differences in spanwise lift distribution, does not come close to making up for difference in structural depth. Because, tensile stresses scale inversely with area moment of inertia, which increases with the square of structural depth, and there is no denying the Su-57 structural depth is much thinner, especially in the area of peak loads at the wings.

Even considering all this, yes it's perfect possible Su-57 weighs less than F-22. Yet highly doubt it can weigh significantly less without certain compromises, for instance, max overload at allowable weights.

Планер многорежимного высокоманевренного самолета

Изобретение относится к летательным аппаратам тяжелее воздуха

poleznayamodel.ru

"The prior art discloses a multi-mode aircraft airframe that comprises a wing with consoles and a center section combined with the middle section of the fuselage, and empennage. The fuselage includes a crew cabin, compartments for accommodating fuel, equipment, and landing gear. The airframe contains at least one turbojet engine installed in a nacelle located in the tail section of the fuselage, with an air intake attached to it with an air supply channel behind it. The airframe frame is made with longitudinal and transverse elements fastened to the corresponding panels. The wing consoles and the center section are made of caisson type, and the tail section of the fuselage and its part between the crew cabin and the center section are made of semi-monocoque type. The said airframe is disclosed in utility model RU, 4109, U1, 1997.

The following can be pointed out as disadvantages of the known technical solution. When arranging cutouts in the lower part of the fuselage for cargo compartments in the known design, it becomes necessary to reinforce the cutouts with additional power elements, such as beams, which inevitably entails a significant increase in the mass of the airframe and a deterioration in the flight and technical characteristics of the aircraft as a whole.

The problem, which the invention is aimed at solving, consists in ensuring the necessary strength and rigidity of the airframe with a slight increase in its weight in the presence of large-sized cutouts for cargo compartments in the lower part of the fuselage. In this case, a technical result is achieved consisting in the redistribution of stresses arising in the power elements of the airframe from external loads due to the rational arrangement of the power elements of the airframe.

The specified technical result is achieved by the fact that in a multi-mode highly maneuverable aircraft of an integrated aerodynamic layout containing a fuselage, the middle part of which is smoothly interfaced with the swept wing consoles, the head part of the fuselage and its tail part, the whole-rotated vertical and all-rotational horizontal tailings located in the rear middle part of the fuselage part of the fuselage is integrated with the center wing and is made flattened in the vertical direction, and its outer surface in The native direction is formed by a set of aerodynamic profiles with high building heights, which ensure that the built-in cargo compartments are placed inside the fuselage, while the upper surface of the fuselage is conjugated with the external surface of the lamp and expanding from the lamp to the rear of the fuselage of the aircraft with a decrease in curvature."



You can't compare apples and oranges and talk about structural depth when you don't have the same load distribution and you don't have the same structural layout.
When we look at the photo above, the area behined the F-22 and J-22 cockpit is basically set of holes, curving and going all the way to the engines.
Area behind the Su-57 cockpit is made of solid structure, so in combination with the more uniform load distribution you don't need huge structural depth for the same strength requirements.

If that wasn't the case, Su-57 would need considerable amount of strengthening, and since it is the bigger plane, and since it has considerably more sensors placed all around the airframe that add weight, it would need to be considerably heavier than F-22, which is not the case.

Here is the Su-27 patent document:

RU2173654C2 - Airframe of multimode monoplane - Google Patents

FIELD: heavier-than-air flying vehicles. SUBSTANCE: airframe has a wing with outer panels center section combined with middle fuselage which includes also crew cabin and compartments for fuel, equipment and retracted undercarriage legs. One or two engine nacelles are located in tail fuselage...

patents.google.com

EFFECT: reduced mass at retained strength

The basis of the invention is the rationalization of the structural power scheme of a multimode airframe from the point of view of its weight perfection, i.e., solving the problem of weight reduction while ensuring the necessary strength.

If that blended wing-body layout is so fragile, we wouldn't be able to watch this plane do this:

View: https://www.youtube.com/watch?v=lKgyywH7TN8&t=126s


That is flying laboratory Su-27UB bort number 503, renamed to Su-30MK. Su-27UB alone is around 1,5 tone heavier, and it is hauling 7,5 tones of ordinance in addition to internal fuel. If we account for 50% of fuel, that is 30 tones takeoff weight!

And TT requirements for the Su-57 are more demanding compared to the Su-27 regarding weight and G load.

As far as airshow performance, F-22 usually ends their demo with more than half fuel, while Sukhoi demos generally start their demos at 56% fuel or less.

On the other hand, if the Flanker or Felon would fly with the full internal fuel load, F-22 and F-15 would need to fly with at least three external fuel tanks, in addition to 100% of internal fuel to match the ferry range of the Sukhoi planes. It would be interesting to see their performance under such fuel load.
At the latest air shows where the F-22 is performing minimal radius turn in the first section of the demo, it is finishing 360 deg. circle on average in about 22 seconds, which is about 16,3 deg/s, which is totally in line with that weight.

 

[Null]

It’s too late in the game for major improvements, the SU-57 is already in production. It’s a huge waste of money to start implementing changes now. Although the SU-75 has superior stealth characteristics which is odd considering the SU-75 is just a side project of Sukhoi with no government funding.

I know the Su-57 like the Su-75 did not come with a detachable cockpit as its patent but what amount of money is considered huge just having it replaced to function as a drone for a later redesign? This isn't something that is super crazy like changing the aircraft to an S-duct.

 

[RadicalDisconnect]

Soviets actually overestimated the F-15 performance, the real EM numbers are worse, and I don't know the reasoning behind their estimates and certain limitations.
The ITR numbers for the F-15C are coming from the aeronautical engineers that have available data for such calculations, including the planes Clmax, which is 1,1 if I remember correctly (I know that the Su-27 Clmax is 1,85, which is considerably higher, and that is one of the main reasons for superior ITR and STR performance).
F-15C with the F100-PW-220 is also heavier so the slightly higher dynamic thrust numbers are negated by additional weight.
...
For example, Su-27 at 20 tones (with 4 missiles) can sustain 9G at 10000ft, but the clean F-15C with F100-PW-220 and 16,7 tones can't (it can sustain around 8,5G's).
Again, in this configuration F-15C has superior T/W ratio and lower wing loading, and still, it has worse performance which only highlights the aerodynamic efficiency of the Su-27 layout.

Your Cl_max is completely wrong and way off for the F-15, it's not 1.1, it's actually much higher at 1.6 based on flight testing. Where did you get 1.1 from? So much for Soviets "overestimating". You should not accuse me of making things up when your own information is so wrong.

https://web.archive.org/web/20100324104138/https://www.nasa.gov/centers/dryden/pdf/87983main_H-1243.pdf

https://aviationarchives.net/AGARD%20F-15%20Performance.pdf

And while Su-27 has higher Cl_max of 1.85, also has higher wing loading of 322kg/sqm at 20,000kg while F-15C at 36,000lb weight which has similar AB duration has wing loading of 59.2lb/sqft or about 289kg/sqm, which is proportionally similar to the difference in Cl_max, so the ITR (proportional to product of wing loading and Cl_max) at these weights is not substantially different for F-15C.

Your numbers completely ignore or misrepresent the weights, and Soviet turn chart comparing Su-27 with F-15 is at 18,920 kg for Su-27 which equates to 2xR-27, 2xR-73, and a bit more than 1,800kg of fuel with Su-27 empty weight of 16,380kg. With only that much fuel, an F-15C, which weighs 29,000lbs empty, with 4xAIM-7 weighs 35,000lbs. But with similar TSFC of 1.9 kg/kgf*h (or lb/lbf*h) in full AB, the F-15 has better afterburner duration with that fuel load so for similar AB duration weight should be 34,500lbs.

Also, your F-15C chart with F100-PW-220 engines shows 37,000lb weight, so the 35,000lb weight with F100-PW-100 is better approximation subsonic, but still underestimated because of higher dynamic thrust of -220 engines.


The 9g sustained turnrate chart for Su-27 is for 2xR-27, 2xR-73, and 2,600kg fuel. And at 37,000lbs or about 16,800kg the F-15C with 4xAIM-7 would actually carry a bit more fuel. For similar AB duration, F-15C with 4xAIM-7 will have just under 36,000lb weight. And keep in mind, at that weight Su-27 requires g-override while F-15 has no limitations at that weight.
Note: per the manual in the station loading section the F-15C with F100-PW-100 weighs 28,500lbs and -220 engines each weigh about 200 lbs more.

You have claimed without any data that the LERX-blended wing body layout is going to increase the overall drag of the plane in a turn.
I have given you the real-world example where we have same-generation, same-class fighters and how they compare with their respective aerodynamic layouts. You can't find better example than that!
F-22 is continuation and improvement of the F-15 configuration (no LERX, close coupled engines), and so is the Su-57 in relation to the Su-27 (LERX, blended wing body, engines placed apart).

F-22 doesn't have LERX, it has sharp inlet chins which generate vortices, but the effective lifting surface of the chin is miniscule in comparison to the real LERX.

What I specifically said is that fuselage lift, being a very low aspect ratio surface, can cause greater induced drag when turning. Of course this depends on condition and not meant to be a broad sweeping statement claiming it's necessarily better or worse.
The F-22 is not a continuation of the F-15, any more than Su-57 is a continuation of Su-27. In fact F-22 is made by completely different company from F-15. You also make comparison using data that is flat out incorrect as shown above. If you want to talk about data, then present the correct data.

F-22 does have a LERX, the sharp edges between the intake lip and the wing generates vortices, which is the whole point of a LERX. The way a blunt shape like the F-15 wing root fairings do not. What's funnier, the NASA paper that you got the image from literally calls the F-22 having a LERX (the paper calls it LEX, "leading edge extension") which is what Lockheed calls it too.

https://ntrs.nasa.gov/api/citations/20000052124/downloads/20000052124.pdf

I’m pretty sure Lockheed knows more about their own aircraft than you when describing it.

It is understandable that in the case of TVC malfunction nozzles are going into neutral position, that is a safety measure for all TVC nozzles, no matter the type of the nozzle. If the nozzle locks up in any position, other than neutral, there is hardly any measure that could save the plane.
Can you provide the data for the conditions where conventional F-22 aerodynamic controls (horizontal tails) can recover the plane from the post stall region?
I'm pretty sure that Sukhoi engineers know more than you about this subject, and about specific conditions they have in mind when they made the claim.
From this chart, we can see that even with the TVC, the F-22 has rudimentary roll/yaw control at 60 degrees AoA.

And yet the F-22 was specifically designed to recover without TVC or malfunctioned TVC. From two sources, Aronstein, Hirschberg, Piccirillo, Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter. Arlington, Virginia: American Institute of Aeronautics & Astronautics. ISBN 978-1-56347-282-4.
"The YF-22 was designed to be fully controllable as well as capable of recovery from any angle of attack within its flight envelope without the use of thrust vectoring. Thus the YF-22's tail surfaces were not appreciably smaller than they would have been if Lockheed had elected not to use vectoring at all."


Also Jay Miller, Lockheed Martin F/A-22 Raptor, Stealth Fighter. Hinckley, UK: Midland Publishing. ISBN 1-85780-158-X. page 34
"As discussed previously, the YF-22A's flight control system was designed to utilize the engine nozzles in the pitch axis. Pitch control, therefore, was provided by a combination of symmetric movement of the horizontal stabilators and thrust vectoring (TV). There were no flight control system AoA limits, and there was sufficient nose-up trim capability to permit flight at extreme AoAs. By utilizing thrust vectoring in the pitch axis, it was possible to reduce the area of the horizontal tail. But, it was still large enough to ensure there was adequate nose-down pitching moment capability to preclude the possibility of a deep stall at high AoAs with thrust vectoring off or in the event of a dual engine failure."

Also the F-22 horizontal stabilators are actually larger than the YF-22 ones for better stealth shaping and test pilot Jon Beesley who did the high AoA testing reported in 2000 that F-22 has more control power than predicted (calling it "a nice problem to have"). You can argue that making these control surfaces so large is unnecessary and overengineered or whatever, but this is what it was designed to.
"Lateral directional control [on F-22] remains good above fifty degrees AOA, but horizontal tails are working hard to provide that control, moving differentially like the webbed feet of a dick paddling through water. (Differential tail is the primary yaw control device. This control technique was pioneered back on the YF-22 in 1990 and works very well.) Although these excessive differential tail movements make for great video, they indicate different aerodynamics than predicted. Actually, we have more control power than we originally thought - a nice problem to have. The first control law update tuned the flight control system to the real aerodynamics, so this characteristic no longer occurs."

https://imgur.com/SDIJRdn

View: https://webcitation.org/6RGU0iAEq?url=http://i.imgur.com/SDIJRdn.jpg

I'm pretty sure Lockheed engineers know more than you about this subject too. Sukhoi describes design rationale as it applies to their own T-50/Su-57 design, but when it comes to characteristics about F-22, pretty sure Lockheed has a better idea of what it can do.

You can't compare apples and oranges and talk about structural depth when you don't have the same load distribution and you don't have the same structural layout.
When we look at the photo above, the area behined the F-22 and J-22 cockpit is basically set of holes, curving and going all the way to the engines.
Area behind the Su-57 cockpit is made of solid structure, so in combination with the more uniform load distribution you don't need huge structural depth for the same strength requirements.

If that wasn't the case, Su-57 would need considerable amount of strengthening, and since it is the bigger plane, and since it has considerably more sensors placed all around the airframe that add weight, it would need to be considerably heavier than F-22, which is not the case.

You don't understand the difference between "holes" and structural holes. A "hole" that is a closed structural loop, or "closed section", does not have the same structural properties as a hole with an open loop, or "open section". The latter is structurally much weaker than the former. Also, there is a reason that for carrying loads, most of the material is concentrated at the edges to increase area moment of inertia.
On F-22 and J-20, the top surface of the "hole" created by the intake ducts and engine compartments are closed sections with top surfaces of the bulkhead still taking structural loads. Meanwhile, the weapons bay on the Su-57 between the engines are open sections because their bottom surfaces are bay doors that take very little load, which is why there is a great reduction in structural depth. This mean that holes for the engine compartment is different from holes such as a weapons bay, because a weapons bay hole is not a closed loop structure. And then there is torsion, where the issue is especially severe for shear stresses of an open section.

Then there is also where the open section holes are placed, on Su-57 they are placed in some of the highest stressed parts of the aircraft along the wing root chord, while on F-22 and J-20 they are placed mostly in front of the wings, so those highest stressed parts have full structural depth.

On the other hand, if the Flanker or Felon would fly with the full internal fuel load, F-22 and F-15 would need to fly with at least three external fuel tanks, in addition to 100% of internal fuel to match the ferry range of the Sukhoi planes. It would be interesting to see their performance under such fuel load.
At the latest air shows where the F-22 is performing minimal radius turn in the first section of the demo, it is finishing 360 deg. circle on average in about 22 seconds, which is about 16,3 deg/s, which is totally in line with that weight.

Don't have the weights for F-22 or Su-57, but for F-15C with 3 external tanks it would have ferry range almost exactly matching ferry range of the Su-27, but neither can maneuver well in this configuration. Assuming F-15C has the same quantity of fuel as Su-27 at normal internal capacity of 5,200kg and 4 AAMs, then the two aircraft have very similar T/W ratio (1.12 for F-15C and 1.07 for Su-27). F-15 with 3 external tanks would weigh about 57,500lbs, no turn charts but there's a similar one for F-15E with CFTs and bombs loaded, and max sustained turn tops out at 6.6g, which is only slightly higher than max g of 6.4g that Su-27 can sustain at max internal fuel given the subsonic overload condition.

 

[F-14ATomcat]

Soviets actually overestimated the F-15 performance, the real EM numbers are worse, and I don't know the reasoning behind their estimates and certain limitations.
The ITR numbers for the F-15C are coming from the aeronautical engineers that have available data for such calculations, including the planes Clmax, which is 1,1 if I remember correctly (I know that the Su-27 Clmax is 1,85, which is considerably higher, and that is one of the main reasons for superior ITR and STR performance).

F-15C with the F100-PW-220 is also heavier so the slightly higher dynamic thrust numbers are negated by additional weight.

View attachment 753078

For example, Su-27 at 20 tones (with 4 missiles) can sustain 9G at 10000ft, but the clean F-15C with F100-PW-220 and 16,7 tones can't (it can sustain around 8,5G's).
Again, in this configuration F-15C has superior T/W ratio and lower wing loading, and still, it has worse performance which only highlights the aerodynamic efficiency of the Su-27 layout.



You have claimed without any data that the LERX-blended wing body layout is going to increase the overall drag of the plane in a turn.
I have given you the real-world example where we have same-generation, same-class fighters and how they compare with their respective aerodynamic layouts. You can't find better example than that!
F-22 is continuation and improvement of the F-15 configuration (no LERX, close coupled engines), and so is the Su-57 in relation to the Su-27 (LERX, blended wing body, engines placed apart).

F-22 doesn't have LERX, it has sharp inlet chins which generate vortices, but the effective lifting surface of the chin is miniscule in comparison to the real LERX.

F-15 sharp inlet edges also generate vortices, along with the wing root extension:

View attachment 753086

View attachment 753087



It is understandable that in the case of TVC malfunction nozzles are going into neutral position, that is a safety measure for all TVC nozzles, no matter the type of the nozzle. If the nozzle locks up in any position, other than neutral, there is hardly any measure that could save the plane.
Can you provide the data for the conditions where conventional F-22 aerodynamic controls (horizontal tails) can recover the plane from the post stall region?

I'm pretty sure that Sukhoi engineers know more than you about this subject, and about specific conditions they have in mind when they made the claim.

View attachment 753100

From this chart, we can see that even with the TVC, the F-22 has rudimentary roll/yaw control at 60 degrees AoA.
At that AoA, the plane cannot perform a full 360-degree roll (the Su-57 can, with roll rates that are significantly faster) because the aerodynamic control surfaces lack control authority, even with the help of the TVC that is controlling the pitch. Without TVC, the F-22 is positioned between the F-15 and F-16 in this regard.
There is an objective reason why the aerodynamic control surfaces placed in front of the center of gravity have better authority and controllability at high AoA. According to Sukhoi's chief test pilot, Юрий Ващук, only two Russian operational planes can achieve supermaneuverability without TVC: the Su-30SM and the Su-57. The Su-35S is more maneuverable and a much more capable dogfighter than the Su-30SM, but without TVC, it cannot exploit the post-stall region.

With addition of the canards Flanker series has unlocked the post stall region in totally controlled manner:

View: https://www.youtube.com/watch?v=AYKWMXAfKRA&t=1s


The plane in question is a former Su-37 that had a new, improved FCS installed; however, the engines with the TVC were removed and replaced with the standard AL-31F. That is the reason they have used the old Su-35 nomenclature. The same improved FCS is used for the Su-30MK/SM versions, and that plane can also perform all those maneuvers without TVC (other flanker versions can't).
We can see that even without TVC, the Su-35 can match the F-22 in the post-stall region, and in some instances, it even surpasses it. The Su-57 can also perform all those maneuvers without TVC, but with the TVC engaged, the plane has faster initial rotational rates and better controllability.



Actually, in that paper it was generalized about the types of control surfaces based on the relative position of the pitch control surfaces with respect to the aircraft's center of mass, and they were categorized in to the positive load pitch down control surfaces, and negative pitch down control surfaces.
As seen and tested, control surfaces placed in front of the Cg do have advantages under high AoA/post stall conditions.



My argument is in agreement with the Sukhoi statements:

RU2400402C1 - Multimode high maneuverability aircraft of integral aerodynamic configuration - Google Patents

FIELD: aircraft engineering. SUBSTANCE: proposed aircraft comprises airframe wherein central part 2 smoothly fairs with backswept outer wings 3, nose part 1 and tail part 6 wherein all-moving vertical tail 4 and horizontal tail 5 are arranged. Canopy 10 is arranged in airframe hose 1...

patents.google.com

It is less useful to look at the planform of the plane to make such conclusion, it is much more useful to look the planes from another perspective:

View attachment 753106

Su-57 is basically a flying wing with inlets and engines slapped beneath it.
F-22 and J-20 fuselage layout is basically the same. Big, boxy midsection with enormously long and curved air ducts that take up most of the useful space. Chinese had strict requirements for long range, and it is obvious why the fuselage is so much bigger/longer compared to both, F-22 and Su-57. You can't go around it if you apply the same configuration F-22 does.

Планер многорежимного высокоманевренного самолета

Изобретение относится к летательным аппаратам тяжелее воздуха

poleznayamodel.ru

"The prior art discloses a multi-mode aircraft airframe that comprises a wing with consoles and a center section combined with the middle section of the fuselage, and empennage. The fuselage includes a crew cabin, compartments for accommodating fuel, equipment, and landing gear. The airframe contains at least one turbojet engine installed in a nacelle located in the tail section of the fuselage, with an air intake attached to it with an air supply channel behind it. The airframe frame is made with longitudinal and transverse elements fastened to the corresponding panels. The wing consoles and the center section are made of caisson type, and the tail section of the fuselage and its part between the crew cabin and the center section are made of semi-monocoque type. The said airframe is disclosed in utility model RU, 4109, U1, 1997.

The following can be pointed out as disadvantages of the known technical solution. When arranging cutouts in the lower part of the fuselage for cargo compartments in the known design, it becomes necessary to reinforce the cutouts with additional power elements, such as beams, which inevitably entails a significant increase in the mass of the airframe and a deterioration in the flight and technical characteristics of the aircraft as a whole.

The problem, which the invention is aimed at solving, consists in ensuring the necessary strength and rigidity of the airframe with a slight increase in its weight in the presence of large-sized cutouts for cargo compartments in the lower part of the fuselage. In this case, a technical result is achieved consisting in the redistribution of stresses arising in the power elements of the airframe from external loads due to the rational arrangement of the power elements of the airframe.

The specified technical result is achieved by the fact that in a multi-mode highly maneuverable aircraft of an integrated aerodynamic layout containing a fuselage, the middle part of which is smoothly interfaced with the swept wing consoles, the head part of the fuselage and its tail part, the whole-rotated vertical and all-rotational horizontal tailings located in the rear middle part of the fuselage part of the fuselage is integrated with the center wing and is made flattened in the vertical direction, and its outer surface in The native direction is formed by a set of aerodynamic profiles with high building heights, which ensure that the built-in cargo compartments are placed inside the fuselage, while the upper surface of the fuselage is conjugated with the external surface of the lamp and expanding from the lamp to the rear of the fuselage of the aircraft with a decrease in curvature."

View attachment 753107

You can't compare apples and oranges and talk about structural depth when you don't have the same load distribution and you don't have the same structural layout.
When we look at the photo above, the area behined the F-22 and J-22 cockpit is basically set of holes, curving and going all the way to the engines.
Area behind the Su-57 cockpit is made of solid structure, so in combination with the more uniform load distribution you don't need huge structural depth for the same strength requirements.

If that wasn't the case, Su-57 would need considerable amount of strengthening, and since it is the bigger plane, and since it has considerably more sensors placed all around the airframe that add weight, it would need to be considerably heavier than F-22, which is not the case.

Here is the Su-27 patent document:

RU2173654C2 - Airframe of multimode monoplane - Google Patents

FIELD: heavier-than-air flying vehicles. SUBSTANCE: airframe has a wing with outer panels center section combined with middle fuselage which includes also crew cabin and compartments for fuel, equipment and retracted undercarriage legs. One or two engine nacelles are located in tail fuselage...

patents.google.com

If that blended wing-body layout is so fragile, we wouldn't be able to watch this plane do this:

View: https://www.youtube.com/watch?v=lKgyywH7TN8&t=126s


That is flying laboratory Su-27UB bort number 503, renamed to Su-30MK. Su-27UB alone is around 1,5 tone heavier, and it is hauling 7,5 tones of ordinance in addition to internal fuel. If we account for 50% of fuel, that is 30 tones takeoff weight!

And TT requirements for the Su-57 are more demanding compared to the Su-27 regarding weight and G load.



On the other hand, if the Flanker or Felon would fly with the full internal fuel load, F-22 and F-15 would need to fly with at least three external fuel tanks, in addition to 100% of internal fuel to match the ferry range of the Sukhoi planes. It would be interesting to see their performance under such fuel load.
At the latest air shows where the F-22 is performing minimal radius turn in the first section of the demo, it is finishing 360 deg. circle on average in about 22 seconds, which is about 16,3 deg/s, which is totally in line with that weight.

Interesting points however no aerodynamic configuration is perfect, it is like women, what you get in one you can not get in another.

Same is in airplanes, even a very advanced fighter will not fly as low and slow as an agricultural aircraft, even with Thrust vectoring.

All fighter aircraft are designed upon a mission profile, weapons reach and sensor ability.

Su-57 prioritizes speed and agility, but it does not mean these requirements are harmonizing, if I want something fast I will take boom supersonic over Su-57.

Stealth aircraft also are not so aerodynamic, their flat surfaces and faceting is peculiarly not low drag.

What I mean is Su-57 was designed upon a military tactic that if well executed will mean Su-57 will beat the rival aircraft, however in life nothing is like in lab conditions and life is more chaotic, so aircraft get losses.

In war you always will have losses, that was factored also in the design of Su-57, sadly Su-57 has a very low production rate, so in war it will not be highly effective, The Americans then consider J-20 a higher threat because its larger deployment and production numbers.

If Russia does not produce more than 300+ Su-57s by 2035 I consider the aircraft a failure despite it is a nice looking aircraft, I think Su-75 if it is produced in numbers will bring all the research and money poured into Su-57 into real success, otherwise sadly Su-57 as beautiful it is and agile will have a very low impact in aviation history.

same was MiG-29 a beautiful aircraft very agile and fast but as long as loses are higher than the production numbers and the victories are more than the loses a fighter is a failure.

Su-27 has eclipsed MiG-29 due to higher production numbers and lower loses per victories considering MiG-29 was supposed to build 2 or 3 MiG-29s per each Su-27 built.

F-16 was then highly successful.

I do not mean F-16 is better than MiG-29, simply the program was more effective only that and Su-57 seems to be not really effective in that regard.

 

[F-14ATomcat]

Your Cl_max is completely wrong and way off for the F-15, it's not 1.1, it's actually 1.6 based on flight testing. Where did you get 1.1 from? So much for Soviets "overestimating". You should not accuse me of making things up when your own information is so wrong.

https://web.archive.org/web/20100324104138/https://www.nasa.gov/centers/dryden/pdf/87983main_H-1243.pdf

https://aviationarchives.net/AGARD%20F-15%20Performance.pdf

View attachment 753117
View attachment 753118

And while Su-27 has higher Cl_max of 1.85, also has higher wing loading of 322kg/sqm at 20,000kg while F-15C at 36,000lb weight which has similar AB duration has wing loading of 59.2lb/sqft or about 289kg/sqm, which is proportionally similar to the difference in Cl_max, so the ITR (proportional to product of wing loading and Cl_max) at these weights is not substantially different for F-15C.

Your numbers completely ignore or misrepresent the weights, and Soviet turn chart comparing Su-27 with F-15 is at 18,920 kg for Su-27 which equates to 2xR-27, 2xR-73, and a bit more than 1,800kg of fuel with Su-27 empty weight of 16,380kg. With only that much fuel, an F-15C, which weighs 29,000lbs empty, with 4xAIM-7 weighs 35,000lbs. But with similar TSFC of 1.9 kg/kgf*h (or lb/lbf*h) in full AB, the F-15 has better afterburner duration with that fuel load so for similar AB duration weight should be 34,500lbs.
Also, your F-15C chart with F100-PW-220 engines shows 37,000lb weight, so the 35,000lb weight with F100-PW-100 is better approximation subsonic, but still underestimated because of higher dynamic thrust of -220 engines.
View attachment 753120

The 9g sustained turnrate chart for Su-27 is for 2xR-27, 2xR-73, and 2,600kg fuel. And at 37,000lbs or about 16,800kg the F-15C with 4xAIM-7 would actually carry a bit more fuel. For similar AB duration, F-15C with 4xAIM-7 will have just under 36,000lb weight. And keep in mind, at that weight Su-27 requires g-override while F-15 has no limitations at that weight.

Su-27 is well known to be more agile than the F-15, they proved it when a pair of Su-27s flew to the USA, they had mock combat with F-15s and the Su-27 won.

In real life F-15 has better combat record but Su-27 is much more effective as a dog fighter, but an aircraft is not only agility but avionics and tactics, so yes F-15 is a good aircraft but as a dog fighter Su-27 is better, but if you consider weapons, avionics or radar well both aircraft are comparable

 

[Ainen]

In real life F-15 has better combat record but Su-27

I think Ukraine should've shown that it's kinda meaningless in system fight.

Flanker, depending on side and weapon system, can be either a pinata without any ability to fight back(old Soviet flanker in Ukrainian service) or a very efficient bomber (same Ukrainian flanker with GBU-39s), almost untouchable by even the best GBADs.

Add "some" system advantage, and modern weapons/electronic, and flanker E (as well as any flanker on RU side which even flew a2a) gets a perfect air to air record without a single loss.

Put contemporary f-15 into same situation, results won't change.
The only fighter that has shown some ability to reverse odds since Vietnam was the foxbat, and everyone knows why.

 

[F-14ATomcat]

I think Ukraine should've shown that it's kinda meaningless in system fight.

Flanker, depending on side and weapon system, can be either a pinata without any ability to fight back(old Soviet flanker in Ukrainian service) or a very efficient bomber (same Ukrainian flanker with GBU-39s), almost untouchable by even the best GBADs.

Add "some" system advantage, and modern weapons/electronic, and flanker E (as well as any flanker on RU side which even flew a2a) gets a perfect air to air record without a single loss.

Put contemporary f-15 into same situation, results won't change.
The only fighter that has shown some ability to reverse odds since Vietnam was the foxbat, and everyone knows why.

In Ukraine is Su-27 versus Su-27 with lots of propaganda from both sides.

Ukraine also is a very complex air war, in the Gulf war of 1991 Iraq did not get new weapons, but In Ukraine there is constant resupply of weapons.

While I do not follow the war, for the little I have seen both sides lie,

Do I think F-15s or F-16 will do better than Su-27? well I have not seen it, the F-16s are there and I have not seen anything amazing, Su-57s also have not shown a lot of success, in my opinion the only good fighter of that war is Su-35.

Do I think Russia has destroyed a lot of Soviet built Ukrainian Su-27s and MiG-29s? I think so otherwise you will not get resupply of MiG-29s and F-16s.

But has Su-57 shown to be a super weapon? No i have not seen it, at least not now but that is my point of view and only later we will know in my humble opinion.

 

[Saber]

In Ukraine is Su-27 versus Su-27 with lots of propaganda from both sides.

Su-35 is a whole different beast than Su-27. you are also forgetting that this is active wartime, and you aren't getting active information on successful or unsuccessful flights by aircraft for either nation, we won't know what the Su-57 and S-70 were up to for this war for likely a very long time.

 

[RadicalDisconnect]

When we look at the photo above, the area behined the F-22 and J-22 cockpit is basically set of holes, curving and going all the way to the engines.
Area behind the Su-57 cockpit is made of solid structure, so in combination with the more uniform load distribution you don't need huge structural depth for the same strength requirements.

Again you're not understanding the difference between an open section hole and closed section hole. In fact, see this for how dramatic the difference is between a close section (similar to an engine bay compartment) and an open section (similar to a weapons bay).

https://vtechworks.lib.vt.edu/server/api/core/bitstreams/a22a7c38-1e42-4db4-9651-e90d5a138bf2/content

Sukhoi themselves identified the risk on the T-50/Su-57 design of this open section structural hole of having large weapons bay between the engines and along the wing root chord. They chose to take this risk because of their desire for large internal payload, but clearly this isn't for free with no downsides. "Not needing structural depth" is extremely misleading because Sukhoi themselves acknowledged that they had to design around that constraint.

Another thing that affects structural weight is service life, Soviet fighters like Su-27 had quite short service life of 4,000 hours while F-15 was rated at 8,000 hours, and same for F-22. Recently the Russians increased aircraft service life to 6,000 hours which should be what Su-57 is too.

Now this isn't to say tradeoffs are necessarily bad. For example, F-22 is designed to pull 9g at takeoff weight with full internal fuel and weapons which require a very strong structure. If Su-57 does not have to pull 9g at takeoff weight with full internal fuel because it's not considered a situation that's expected to occur, then it may save weight and improve performance elsewhere. But again that's still a tradeoff, nothing is "free".

 

[F-14ATomcat]

Again you're not understanding the difference between an open section hole and closed section hole. In fact, see this for how dramatic the difference is between a close section (similar to an engine bay compartment) and an open section (similar to a weapons bay).

https://vtechworks.lib.vt.edu/server/api/core/bitstreams/a22a7c38-1e42-4db4-9651-e90d5a138bf2/content

View attachment 753124

Sukhoi themselves identified the risk on the T-50/Su-57 design of this open section structural hole of having large weapons bay between the engines and along the wing root chord. They chose to take this risk because of their desire for large internal payload, but clearly this isn't for free with no downsides. "Not needing structural depth" is extremely misleading because Sukhoi themselves acknowledged that they had to design around that constraint.

Now this isn't to say tradeoffs are necessarily bad. For example, F-22 is designed to pull 9g at takeoff weight with full internal fuel and weapons which require a very strong structure. If Su-57 does not have to pull 9g at takeoff weight with full internal fuel because it's not considered a situation that's expected to occur, then it may save weight and improve performance elsewhere. But again that's still a tradeoff, nothing is "free".

The weapons bays are different, on the F-22 they are wider. but on the Su-57 they are narrower and the fuselage does not have side weapons bays.

The Su-57 must have a good design otherwise it will not maneuver as it does, Both designs are good, add by being the engines farther apart there is less need to vector the nozzle, and with the new nozzle I think they will vector less in many directions reducing the forces that can torn apart the fuselage.

 

[RadicalDisconnect]

The weapons bays are different, on the F-22 they are wider. but on the Su-57 they are narrower and the fuselage does not have side weapons bays.

The Su-57 must have a good design otherwise it will not maneuver as it does, Both designs are good, add by being the engines farther apart there is less need to vector the nozzle, and with the new nozzle I think they will vector less in many directions reducing the forces that can torn apart the fuselage.

It's not just shape of weapon bays but also where they are placed, on F-22 and J-20 they are mainly put in front of the wings, while on Su-57 they run along the entire wing where the peak loads happen. This is a structurally riskier approach that Sukhoi themselves stated in their design patents. The benefits to this is a larger internal payload capacity, but the structural risk is undeniable here.

But as stated, the tradeoffs aren't necessarily bad. But that's not the same as claiming that the design is "perfect" with no tradeoffs whatsoever like what some posters here are claiming.

 

[Trident]

Again you're not understanding the difference between an open section hole and closed section hole. In fact, see this for how dramatic the difference is between a close section (similar to an engine bay compartment) and an open section (similar to a weapons bay).

There is a very simple yet effective display on this issue in the Deutsches Museum in Munich: a pair of round-section steel tubes are mounted end-on to the wall, with handle bars on the other end. One of them is a normal, closed tube, the other cut open lengthwise in a narrow slot from the handles to the wall - the difference in the force required to twist them with the handles is amazing!

Another thing that affects structural weight is service life, Soviet fighters like Su-27 had quite short service life of 4,000 hours while F-15 was rated at 8,000 hours, and same for F-22. Recently the Russians increased aircraft service life to 6,000 hours which should be what Su-57 is too.

One thing I'd note on this point is that you need to be aware such a comparison of flight hours between aircraft designed by and for radically different entities can only ever be a rough guide. An hour in one case need not be exactly the same as an hour in the other, because the kind of flying and resulting loads contained in one hour is an assumption specified by the customer or regulations that may vary wildly between countries and aircraft type. In Western parlance, it is therefore becoming more common to use the less confusing term flight cycles instead of flight hours, since even an hour of real flying might not exactly correspond to a structural flight hour.

This is most obvious when comparing different types of aircraft: an hour of F-22 flying (real or structural) is going to involve drastically different loads than an hour of 787 flying. And even between different aircraft in the same category, significant differences can occur - the F-22 will in turn be radically different to the A-10, even though both are combat aircraft of roughly the same size. Likewise the A320 and 787, simply by flying shorter missions the Airbus has a much higher proportion of more demanding take-offs and landings per hour. Similar differences are bound to occur between fighters designed in places with such disparate operational practices as the US and Russia.

Last but not least, the assumptions written into the spec the airframe is designed against can prove to be wrong! The F-16 was designed to last X number of flight hours, with the kind of loads involved in one flight hour derived from F-4 operational experience. This turned out to be a poor reflection of real usage, since the pilots, delighted with the vastly improved maneuverability of the F-16, took advantage of its 9g capability *far* more often than anticipated. As a result, the aircraft would not have lasted anything like X flight hours as originally designed and had to undergo the FalconUP structural reinforcement programme to keep them in the air for the required time.

Now this isn't to say tradeoffs are necessarily bad. For example, F-22 is designed to pull 9g at takeoff weight with full internal fuel and weapons which require a very strong structure. If Su-57 does not have to pull 9g at takeoff weight with full internal fuel because it's not considered a situation that's expected to occur, then it may save weight and improve performance elsewhere. But again that's still a tradeoff, nothing is "free".

When comparing aircraft with markedly different fuel fractions at full tanks (e.g. Su-27S and F-15C) you also have to bear in mind that a g-load at X% internal fuel is going to be significantly more onerous on the aircraft with the higher capacity. I know you did that correctly earlier, but it bears mentioning again.

 

[Ainen]

Do I think F-15s or F-16 will do better than Su-27? well I have not seen it, the F-16s are there and I have not seen anything amazing, Su-57s also have not shown a lot of success, in my opinion the only good fighter of that war is Su-35.

Su-57 is a relatively dark page of this war. Public info on their operations comes only from Ukrainian sources.

But an interesting aspect of this plane(and, slight offtopic, something I suspect USN is interested in doing) - unlike other current-gen fighters, su-57 is the only one that is very clearly ahead of 4th-gen aircraft in every single regard.
If it fails at something compared to them, its current platform maturity; otherwise, the basics are simply hopeless. That includes su-35.

 

[F-14ATomcat]

It's not just shape of weapon bays but also where they are placed, on F-22 and J-20 they are mainly put in front of the wings, while on Su-57 they run along the entire wing where the peak loads happen. This is a structurally riskier approach that Sukhoi themselves stated in their design patents. The benefits to this is a larger internal payload capacity, but the structural risk is undeniable here.

But as stated, the tradeoffs aren't necessarily bad. But that's not the same as claiming that the design is "perfect" with no tradeoffs whatsoever like what some posters here are claiming.

Let us remember aircraft are tools, if we see that we can comprehend any design, without absolute concepts.

No aircraft can do everything for such reason you have different types.
What I meant is any tool has a range of uses, and same is any aircraft.

can I ask Su-57 to fly as low as an agricultural aircraft? No we can not.
Can I ask Su-57 carry as many people as B-787? No we can not.

So Su-57 is designed to solve some tasks therefore its configuration has pros and cons.
Ideally aircraft are designed to be used in certain way it will guarantee to be effective.

Same is the weapons bays, the Russian logic was to make a fuselage that had some camber and generated lift and blended with the wing in the same way F-14 and MiG-29 were designed, they decided that was the basic configuration, this as well as you have mentioned generates problems and solutions.

F-22 has other logic, it is a F-15 type, both have advantages and disadvantages, but depending how an aircraft is flown you will get the success you need.

The interesting things is the innovations seen on Su-57, Levcons, the side weapons bays that work as aerodynamic fences and still carry a single short range AAM, and now the new flat nozzle, in my opinion it is a very innovative design.

The only problem i see on it is its low production numbers.

The main weapons bays are designed to help retain the F-14 type fuselage lift while still carrying weapons and allowing for a very small radome and canopy cross section.

Is it better than other fighters? it will depend how the other fighters are flown, the avionics they have and weapons they use, absolute concepts are impractical because aircraft are tools designed to solve problems, and each aircraft solve different problem thus it has compromises, pros and cons.

 

[RadicalDisconnect]

By the way none of this is to take away from the Su-27 or Su-57 designs. In fact I think aerodynamically the Su-27 is overall more advanced than the F-15, and in fact the Flanker is more comparable to the F-16 in that regard.
And I think the Su-57 is overall most maneuverable fighter in the world, thanks to the TVC and the potent aerodynamic design. Only thing is that in supercruise with existing AL-41F1 it doesn't measure up yet with a clean Typhoon or F-22 just yet, but we'll see how the AL-51F1 stacks up. I just find some of the claims here exaggerated or based on outright incorrect information (grossly understating the F-15 Cl_max for example) and drawing conclusions from airshows with unknown aircraft weights and configurations. And also handwaving away any tradeoffs or technical risks when Sukhoi themselves acknowledged them.