Sukhoi FSW Fighters from S-22 / S-32 to S-37 / Su-47 Berkut

[hs1216]

What happened to the S-37's FSW? ???

 

[sferrin]

What happened to the S-37's FSW? ???

The Russians discovered the FSW isn't all it's cracked up to be.

 

[Ogami musashi]

What happened to the S-37's FSW? ???

Maybe you seek for a more precise answer so here it is:

The FSW poses in its very basic layout a great problem that i shall explain here hoping not to go to much into details:

Lift may lift the plane (wow) but it also does proportionnaly increase the stress on the wing.
With molecules striking the wing, for a given surface, the only way to increase lift is make them strike the surface faster or to make more and more of them striking to surface of the wing.
All of this translate into stress in the wing.

A wing may seem rigid, but it's not, it actually twist and bend around an axis known as Shear axis.
This axis can be viewed as starting form the center of the root of the wing, extending till the tip of twing barely then crossing the chord of the wing at his center (this is not really like that but for explanation it will be ok).

Lift is expressed in its all at a point, the center of pressure (pressure on the wing=stress).
When heavy lift is expressed, the tip of the wings being less stiff than the root, has tendancy to pitch by herself up and down (just imagine either the Leading edge or Trailing Edge pitches as if they were taking AOA)
It founds that on Aft swept wings the center of pressure is behind that shear axis so the wing's Trailing edge bends(pitches down) first.
As she bends first, lift is reduced then the wing return to its normal position until we get at certain speeds but we'll let this for now.


On a forward swept wing the problem is that the center of pressure is just in front of the shear axis, wich means the wing's Leading edge bends (actually she pitches up, like taking Angle of attack)up and here comes the real problem, as she bends up, just to oppposite of the aft swept wing (not surprising considering we talk about a wing put in the opposite way..) the lift INCREASES thus the pitching moment increases , and increases, and increases until the wing breaks.

This is know as Wing divergence (when the wing starts to behave aerodynamicaly differently and at its own rate than the rest of the lifting parts of the plane) and it is a very dangerous problem.

This problem is not only dangerous, it just make the wing dragging more and more (more AOA=more drag).

When does lift(=stress on wing) is the highest? in supersonics and at high G loads.

Sukhoi started with a challenge, they had to fix the problem of that wing, the wing was to stay relatively dependant on the fuselage...the meant this by usage of stiff carbone composites but...THEY FAILED.

The planes showed divergence just not only in supersonics but also in the modest loads it has every endured (that's to say: 5G's, the plane was limited to 5g's), so sukhoi did say "okay no problem! let's put titatium on the wings!" LOL, 1 more ton added to that plane!

1 more ton=more AOA needed for the same lift=more drag, more AOA=more divergence risks=No way plane.

The plane was not only not able to go supercruise (even with hypothetic AL-41) but not able to pull a lot of G's sustained so i'll let you guess what were the possiblities with that plane..


That's not to say the FSW is a bad design, it had some potential but just like with the X-29 the compromises needed to control that divergence problem just resulted in bad performance.

We'll need to wait more to see a FSW supersonic plane!

Ah by way, some echos away in the sukhoi design plant resonate saying the S-37 was a pushed program, it was already dead born but his designer pushed for it..
According to thoses same reports, the S-32 (the first design for the russian navy, with flat nozzles and wing tip nacelles) was more performant..rumours? true? who knows..


I guess i missed my goals of not going into details..

 

[flateric]

"The most important problem of this bastard is not weight, but jolting. The matter is that this (FSW) scheme has a congenital defect which no one can get rid of. In a break point of a forward edge very strong vortices form which descend from the left and right consoles approximately in chessboard order. Frequency and intensity of these vortices makes flight on this pepelatz (notorious alien spaceship from soviet movie Kin-Dza-Dza, image attached, comments are unnesessary) reminds driving a oxcart on a stone blocks. Americans have tried it on the X - 29 and have spat upon this scheme (and informed the whole world about these problems). But Russians have their own pride,<...>. So we have what we have. "
"Wing fuel tanks have continous leaks - they have to use pans to collect it"

Anonimous insider at avia.ru forum

Other source discusses exact vortices generation process (in his words, it's more complicated), but confirms resulting problems.

I even remember scetch of vortices drawn by unnamed Sukhoi engineer in Russian PopMech edition, but not have this issue on hands now.

 

[frank]

But what did happen to the S-37s wing? I missed something.

What happened to the S-37's FSW? ???

 

[Ogami musashi]

Flateric, if you can find the documentation ,i'd be glad.

I've read the X-29 reports, and do not remember those vortices problems but my memory is shorter than a nintendo Nes one.

Though i didn't say the problem was weight, i said (one of) the problem was divergence wich is quite common for FSW(and was mentionned in X-29) and that trying to fix it with titanium added weight.


Just to clarify.

 

[flateric]

But what did happen to the S-37s wing? I missed something.

Whole Ogami post was about it, Frank. Wing composite construction structurally got serious damage due to divirgence. Wing carry-through structure assembly was replaced with Ti one.

 

[Sundog]

The other problem with forward swept wings is even with advanced aero-structures, you're still limited to M=1.7 . Any speed above that and a standard wing with rearward sweep is better since the FSW would still be weight prohibitive above that speed to counter-act the wing's natural pitching moment/twist.

I don't know if there is any evidence to support it, but my understanding is Grumman's ATF proposal had a forward swept wing and it also was placed last in the initial competition. I know there is the painting of the Grumman FSW with the large canard, but I don't know if that was actually their submission.

 

[sferrin]

The other problem with forward swept wings is even with advanced aero-structures, you're still limited to M=1.7 . Any speed above that and a standard wing with rearward sweep is better since the FSW would still be weight prohibitive above that speed to counter-act the wing's natural pitching moment/twist.

I don't know if there is any evidence to support it, but my understanding is Grumman's ATF proposal had a forward swept wing and it also was placed last in the initial competition. I know there is the painting of the Grumman FSW with the large canard, but I don't know if that was actually their submission.

I've always had the impression that was the case too if for no other reason that nothing else has ever come forward. Rockwell was another who's apparent ATF entry had been out there for all to see as well. As for the FSW I remember reading an interview with one old aeronautical engineer back before the ATF concepts had been revealed along the lines of "what do you think they might be like?" When they brought up the FSW the engineer said "no way". When the interviewer mentioned the X-29 the engineer laughed and said "yeah, we need to drag that thing (the FSW) out about every forty years or so to remind us why it's a bad idea."

 

[lantinian]

Great insight into this FSW guys. I will some of this was a more public knowledge. In my country even the image of the S-37 was enough to trigger speculation about the Russians finally showing their answer to the F-22 and how better it was compared to the US fighter.

Things like "It even flew one weak before the Raptor" were bad comments enough and artist rendering of S-37s shooting F-22 just added to the propaganda of the officials of MiG and Suhoi.

With all the lack of money in aerospace in Russia the last decade, one wanders if those funds spend on the S-37 development would now have been put elsewhere...

lantinian

 

[flateric]

Vadim Lukashevich (www.buran.ru) has uploaded some 3D models of C-32 (Su-27KM) at Novosti Kosmonavtiki (News Of Cosmonautics) magazine forum, http://www.novosti-kosmonavtiki.ru/phpBB2/viewtopic.php?t=1406&start=1380 It was pre-C-37 carrier-based fighter (Vadim was involved in design), Soviet answer on F-14D with stealth tech elements. Updated info on C-32 with first scetchy 3D model (it had numerous mistakes) appeared recently at Segey Babain site http://www.testpilot.ru/russia/sukhoi/s/37/index.htm - based mostly on Lukashevich information. Chief designer was Pogosyan. Interesting details reported are ejectable from the depth up to 15 meters pilot's capsule, giving pilot ability to survive in the open waters up to 3 days, and unusual wing folding mechanism (details will appear in final version of 3D model). Last one was subject Vadim's candidate's degree.

3D model was made by Vadim and Mikhail Pavlov.

 

[Ogami musashi]

Very interesting! thank you flateric.

 

[Archibald]

Excuse my ignorance... this project would the "missing link" between Su-27 and Su-47 FSW demonstrator ? ???

 

[Ogami musashi]

The C-32 was the first model presented to the Russian navy.

There's one famous picture of the presentation of the RC mock up to officials, the configurations was the same than the 3D pictures aboves but wings tip had Sorbstiya nacelles on each sides.

The project then evolved in the C-37 configuration and did not interested anybody anymore.

I don't know what happened between the C-32 and C-37.

 

[overscan (PaulMM)]

S -32 (Su-27KM) carrier-based fighter

Preliminary operations on creation of the heavy fighter of the fifth generation for VVS and PVO began at the end 1979 within the framework of program I -90 (“the fighter 1990- X of years”). In 1981 g. the special-purpose comprehensive program of the creation of fighters 90 X yr. was affirmed by the decision of government. Works on the creation of multipurpose tactical fighter headed MMZ Mikoyan. On the recollections the O. S. Samojlovich, Silaev (minister OF [MAP] - [prim].SB) insisted so that Sukhoi KB would participate in this work on the competition with KB Mikoyan. However, E. Ivanov decisively was rejected, after saying that Su-27 - this is a fighter 90 X of years. The potential possibilities of aircraft are such, that to the end of century will not be created not one machines, which could exceed Su-27 and its modifications.” OKB [im]. OF P.O. Sukhoi was charged the development of attack aircraft for the program Sh -90 (“the attack aircraft 1990- X of years”). Nevertheless, when in 1983 OF OKB Simonov headed M. p., he makes decision about the initiative-taking development of the fighter of new generation. The designation of project - S-22, similar to index of one of the modifications of fighter-bomber Su-17, made it possible to conduct works without the premature publicity. Simonov was the large enthusiast of aeroplane design with the sweptforward wing, and he decides to use it on the new fighter. The major advantages of this layout are: a notable increase in the lift-drag ratio during the maneuvering, especially with the low speeds; large lift in comparison with the sweptback wing, which has identical area, and, therefore, also large load capacity (to 30%); a increase in the flying range in the subsonic modes due to the smaller trim drag: the best controllability at the low subsonic velocities (and, as a result, improvement [VPKH]); a improvement in the conditions for work of wing mechanisation (which also reduces takeoff and landing distances); smaller stalling speed; the improved antispin characteristics; a increase in the internal volumes of glider, especially in the sites of the joint of wing and fuselage, which provides the best conditions for the formation of internal loading compartments. there was in this diagram significant shortcomings. The attempts to use it undertook even in the middle 40- X yr. - Ju-287 (Germany), [LL]- E p. v. Tsybin. Elastic positive wing divergence was principal restriction (twisting and the subsequent destruction of wing). The wings from the aluminium and even steel alloys air-blast in the supersonic wind tunnels were destroyed. Attempts at the increase in the rigidity of the wing, which has traditional metal construction, led to the inadmissible increase of mass. The use of composite materials made it possible to fight with the twisting with the aid of the specially oriented coil of [uglevolokna]. By this was assigned the special arrangement of the flexural axes of wing (by the directed twisting strain), which compensate fors by the turning of cross sections a increase in the angles of attack at the bend. Also deteriorated, in comparison with the MFI layout, characteristics at supersonic speeds, which was caused by drag divergence and by large displacement of aerodynamic focus. Unacceptable aerodynamic buffeting was another shortcoming in the diagram. It appeared with the rendezvous of two incident vortex flows: one - from wing leading edge, another - from the near-fuselage rolls. In the course of the tests of the experimental aircraft of X -29, created by American company Grumman Of aircraft Of corporation and passed tests with 1984- GO on 1992 on the base “Edwards” in California, means for dealing with this phenomenon so they were not found. To conquer the buffeting expected with the aid of that finished on the series Su-27 and MiG-29 technologies of the droop nose of leading wing edge, which was used also on S-22. Works headed chief designer V. S. Konokhov. S-22 was executed according to canard configuration forward sweep, had one engine and takeoff weight in the limits of 20-24 tons. The complete package of working documentation was released on it. However, in the course of designing the aircraft it was explained that the construction of machine was overloaded. This required the radical revision of project, creation actually of new fighter. After considering work experience and being based on the existing scientific technical reserve, in OKB OF P.O. Sukhoi they approached the development of the new twin-engined forward sweep fighter, which received the index “S-32”. The development of design headed chief designer [M]. a. Pogosan. On one of the versions Of S.32 it was intended to equip with two RD -79M turbofans (2 X of 18,500 kg) with the system of the thrust vector control (modernised version of engine RD-79, created for the VTOL aircraft Yak-141). Subsequently was accepted the solution to establish to the fighter the engines of the fifth generation AL -41f (2 x of 20.000 kg), supplied with TVC. With new turbofan it would obtain the ability to accomplish prolonged cruising supersonic flight without the use of a afterburner: with the creation of the aircraft Of S.32 the most serious attention it was given to questions of reduction in the radar distinctness (in this region OKB [im]. OF P.O. Sukhoi it had available significant experience, obtained in the course of developing the heavy bombers, in particular - aircraft T -4MS). The specific contribution to the formation of the configuration of FSW fighter introduced the design project leader [NPO] “Zvezda” G. Severin, who proposed the fundamentally new concept of the catapult seat of the variable geometry, the ensuring to pilot the possibility of conducting maneuverable dogfight with considerably the higher, than on the previous fighters, g-forces. This made it possible to maximally use maneuverable advantages of aircraft with the sweptforward wing. The program of the building of aircraft carriers in THE USSR collected the revolutions (two aircraft carriers - “Tbilisi” and “Varyag” they were already in to float, atomic “Ul'yanovsk” it was already placed); therefore in carrier-based aviation of prospect they were good. To the ship-based derivative of the fighter, named Su-27KM and was released preliminary design in 1988 g. it was proposed BY VMF as a deep modification of Su-27 c.c. - 33). The need for superiority of the new aircraft over analogue - F -14D most up-to-date at that moment determined installation of two engines and maximum takeoff weight - to 40 tons. But the takeoff of so heavy a aircraft from the ramp was complex, and catapult had to appear only in “Ul'yanovsk”. Was also problem with fastening of catapult to the front rack of aircraft - on Su-27K the rack has the rear drag strut, which with the acceleration worked in tension, while because of the layout on Su-27KM the strut of front rack was from the front, and it worked on the compression. Therefore basic mode had to be takeoff from the ramp. But calculations showed that the aircraft does not manage to collect the necessary velocity with the acceleration on the deck without the catapult, necessary for the takeoff without the sag of lower than the edge of deck. Here and it had to rescue FSW, that has the higher bearing capacities at the high angles of attack and furthermore on BRAIDS the disruption began from the higher angles. All this made it possible to realise ballistic takeoff from the ramp, i.e., at the moment of gathering from the ramp the lift of wing still less than the weight of aircraft, and it moves not as aircraft, but as the deserted stone, along the ballistic trajectory (with the angles of attack, close to the critical for FSW, continuing acceleration due to th e engines operating on the afterburner. [Dostignuv] of the peak of trajectory, aircraft begin to be squandered down, the sag could be 10-15 metres from the upper point in the trajectory, but to the count of the increasing velocity and very high angle of attack FSW it " caught” machine, and in the descending branch of trajectory, approximately at the level of the shear of ramp, ballistic trajectory passed into the normal climbing flight. The schematic FSW with the developed of mechanisations and the dual tail assembly thus appeared, since the [sorokatonnyj] aircraft with the common wing with the takeoff from the ramp simply would fall outside - lift effectiveness at the high angles of attack of common wing it did not be sufficient for the creation of the required lift. Stalling in common wing begins with the smaller angles of attack in comparison with FSW. Machine had to have landing hook and added outer planes of wing. It was intended to use elements 'Stealth' in the configuration of machine - for this, in particular, fins were sloped inward. Aircraft it was planned to equip phased array radar. During May of 1989 g. with the resolution of the military- industrial commission of Council of Ministers in the number of other themes the development Su-27KM was closed, and [NIER] and OKR for S -32 continued in basic due to the personal means OKB. At the end 1980- X began work on preparation for building of the test batch of aircraft. With the attraction of Irkutsk aircraft plant were intended to gather 3 units - 2 “flying” even 1 for the static tests. After 1991, when the defence expenditures of Russia sharply were reduced, it was necessary to limit to two experiment machines. However, subsequently financing program actually ceased. In these conditions OF OKB found the possibility to continue works in the initiative-taking order on its own means. In the beginning 1990- X of years was constructed only one “experimental” aircraft, which received index “S -37”. For the first time the photo of model S -32 was published in the journal “herald of air fleet” (March-April 1996 g.)

Rough translation of the Airwar.ru page

 

[flateric]

Me was dumb and tired, but Paralay was smart and enthusiastic.
So, here goes S-47 cockpit...
http://paralay.com/maks/91.jpg

Other Paralay pics from MAKS 2007 are here http://paralay.com/maks2007.html

 

[flateric]

This IS NOT S-37/Su-47. This is S-32 (Su-27KM) - that's clearly described at Vadim's site.

 

[flateric]

After 10 years of the maiden flight, we have ability to look at Su-47 a little bit closer...Still can't understand what so hell secret about its skin panels and their black color of which insiders make strange manipulations with eyeballs.

 

[rousseau]

That photo you taken while you were lying under abdomen would be rare and more interesting ;D

 

[archipeppe]

That photo you taken while you were lying under abdomen would be rare and more interesting ;D

Absolutely, especially for the label "OKB SUKHOI" written in cyrillic on left side of the aircraft.

 

[flateric]

Guys, didn't you see these are screenshots?

 

[archipeppe]

Guys, didn't you see these are screenshots?

Of course.
Did you have the original video?

 

[flateric]

Yes. Stills are from DVD that in turn an TV-Rip from last Strike Force weekly TV show.
All Su-47 related stuff lasts about 6 seconds)))

 

[flateric]

That photo you taken while you were lying under abdomen would be rare and more interesting ;D

Rousseau, regarding aircrafts term used is 'underbelly'. Never wanted to lie under someone's abdomen...
If these were my photos, I would be now at large building at Lubyanka waiting for some LO's favorite pentothol martinis...

 

[flateric]

Vadim Lukashevich's team has finished unprecedented work on C-32 / Su-27KM model - now it shows her unusual folded wings configuration. Note that Su-47 wing panel lines are repeating fold line pattern initially planned for C-32.

Higher resolution images aviable free at http://www.buran.ru/htm/news.htm
Free 3D model 3D Studio MAX 9 for http://www.buran.ru/htm/3d-model.htm

Two first GIFs are animated! Behold!

 

[Ogami musashi]

Thank you, what a beautiful plane. If only this configuration worked...

 

[flateric]

Su-47 at the shop + her fuselage engine section made of titanium (belongs to the uncompleted sistership) + freeflight drop model + aeroelastic stability tests model

 

[hs1216]

I've always wondered why the s-37 used D30 engines from the mig-31, and not the standered AL-31 type engines typical of the flanker family?

 

[flateric]

Because bird is damn heavy, I think.

 

[overscan (PaulMM)]

It was designed around R-79M or AL-41F with MUCH higher thrust than AL-31F.

 

[flateric]

...and because there were no spare AL-41Fs, they took these monsters...

 

[flateric]

Finally - a big article on Su-27KM that appeared by efforts of my friend Vadim Lukashevich in November issue of PopSci Russian Edition

http://paralay.com/su27km.html

In Russian so far...

Mostly, it's a history of Sukhoi's Chief Designer Mikhail Simonov efforts to made Su the only carrier fighter of the fleet and beat the more suitable for that, smaller, MiG-29K. One of first efforts to minimize storage size of navalized Su-27 went so far as to fold her vertical tails and staggerring aircrafts in a two-level vertical rows in the carrier's hangar...

The sad truth of Su-27KM and its successor, Su-47, is it's disastrous survivability - composite forward-swept, highly loaded, magically tapered wing just could not survive any sufficient damage, and even if pilot could bring bird back to the desk, the whole wing should be replaced - with a prices up to 6 million roubles per wing in 1991 prices (with exchange rates of 5 roubles for one dollar AFAIR in the end of 1990)

 

[Ogami musashi]

The SU-27KM was designed AFTER the S-37??

Is there any info on that article about aerodynamic performance of the SU-27KM?

 

[flateric]

The SU-27KM was designed AFTER the S-37??

Is there any info on that article about aerodynamic performance of the SU-27KM?

1). Sorry for my poor language - of course I did mean 'predecessor'.
2). Nope so far

 

[overscan (PaulMM)]

I think you meant successor.

Predecessor means "one that comes before"

 

[flateric]

D'oh!

 

[Matej]

There's one famous picture of the presentation of the RC mock up to officials, the configurations was the same than the 3D pictures aboves but wings tip had Sorbstiya nacelles on each sides.

I think that the first public information about S-32 was this photo (sorry for the bad quality, but it is the best what I can provide) published in Vestnik Vozdushnovo Flota.

 

[flateric]

Matej, it's not actual S-32...just look at the intakes...one of many iterations in between..

 

[Matej]

Eh, my formulation was not exact. I wanted to say that it was first public photo of soviet/russian FSW fighter that time under development, so something from S-32 family, not exactly S-32/Su-27KM.

 

[flateric]

Yes, that's the fact) Two guys were heavily *%^*%& for this leak. But, it's Navy fighter obviously with arresting hook...with absolutely non-Navy colors...