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

[flateric]

...

 

[chuck4]

Is there confirmation the long ventral strakes under the wing roots are missile bays?

 

[flateric]

it was known from insiders back in late 2009 - even before T-50 external view was declassified on maiden flight

 

[Wil]

hello friends


In reference to the object that can be seen in these images:


http://imageshack.us/a/img32/5023/blockerpakfa1.jpg


http://imageshack.us/a/img21/6820/t50323hires3.jpg


an user of KP forum has said that "it is an IGV (Inlet Guide Vane)". It seems to me this device is a combination of IGV and radar blocker.


¿What do you think? Thanks in advance...!

More info in spanish of PAK FA (and photos), here:

http://espacial-org.blogspot.com.ar/search/label/PAK%20FA

 

[Bill Walker]

My sources tell me the under wing fairings just outboard of the main gear wells contain actuators for leading edge flaps on the wing centre section. I have seen a sketch showing the actuator and the drive linkage, but I think it was in a Powerpoint, not available on the web.

 

[flateric]

My sources tell me the under wing fairings just outboard of the main gear wells contain actuators for leading edge flaps on the wing centre section.

BS

 

[chuck4]

My sources tell me the under wing fairings just outboard of the main gear wells contain actuators for leading edge flaps on the wing centre section. I have seen a sketch showing the actuator and the drive linkage, but I think it was in a Powerpoint, not available on the web.

Unless the actuator consist of a thousand gerbils pulling on a string, I can't imagine why it would need a fairing so long.

 

[Wil]

Hello Friends!


Five new 2013 calendars of PAK FA, in high resolution, ~7 MB.
Unknown author.


http://espacial-org.blogspot.com.ar/2012/12/mas-calendarios-2013-del-sukhoi-pak-fa.html


Enjoy!

 

[Trident]

Wasn't that drawing with the actuator & linkage a speculative illustration, made by a member of this forum literally days after the first flight back in 2010? Seems to have taken on a life of its own in the meantime!

 

[Wil]

Hello!


A nice pic of PAK FA #1, © Pavel Noddlov. Enjoy!

 

[Bill Walker]

My sources tell me the under wing fairings just outboard of the main gear wells contain actuators for leading edge flaps on the wing centre section. I have seen a sketch showing the actuator and the drive linkage, but I think it was in a Powerpoint, not available on the web.

Unless the actuator consist of a thousand gerbils pulling on a string, I can't imagine why it would need a fairing so long.

Don't shoot the messenger, I'm just repeating a theory I heard in a briefing on the aircraft about a year ago. The actuator is quite large and has a fairly long stroke with a bellcrank mechanism to gear down the stroke (increasing the force), suggesting the LE flaps are used at very high speeds. Anybody else have a different story?

 

[flateric]

Anybody else have a different story?

Theory is BS and comes from someone who knows absolutely nothing about aircraft construction and modern state of actuators tech. These pods are equipped with clearly visible doors and hold one Izd.760 short-range AAM each.

 

[overscan (PaulMM)]

Take it from me, its definitely an SRAAM weapons bay.

 

[saintkatanalegacy]

There are patents a few pages back for that if you want references

 

[Wil]

Hello!


Another great image of PAK FA, August 2012, © Alex Vorivoshin.


best wishes!!

 

[flateric]

an user of KP forum has said that "it is an IGV (Inlet Guide Vane)". It seems to me this device is a combination of IGV and radar blocker.

it was discussed dozens. hundreds. zillion times in last two years. it was known FOR AGES HOW radar blocker would look like
THERE IS NO RADAR BLOCKER INSTALLED YET ON ANY OF FLIGHT VEHICLES

 

[Radical]

Out of curiosity, wouldn't radar blockers have a negative effect on engine performance due to complications with airflow through such blockers?

 

[flateric]

there's always a compromise...

 

[Sundog]

Out of curiosity, wouldn't radar blockers have a negative effect on engine performance due to complications with airflow through such blockers?

Complications? No. In fact, they could help by controlling the airflow into the engines. However, they'll add weight and drag/pressure loss. However, the trade-off is what is the weight/flow losses due to the fan blockers versus the weight/flow losses of serpentine ducts that would be the engineering question.

 

[bipa]

Agree. It is very difficult to tell and most likely case-dependent: probably there is no ultimate definite truth about blockers vs. serpentine ducts.

Both solutions (blockers and serpentine ducts) are mainly a matter of minimizing thrust/drag penalty (over a certain set of flight regimes), volume and weight, while pursuing a given RCS reduction target (which itself is aimed at certain frequency bands and aspect angles). Other criteria like sturdiness or serviceability may also be of importance.

My (rather uneducated) gut feeling is that serpentine ducts concepts may reach better overall compromises between T/D and RCS, but at higher volume (and possibly weight) toll. OTOH blockers seem like a compact "bolt-on" solution, but it's probably an engineering nightmare to manage their T/D and RCS efficiencies (let alone both together) over a wide range of situations.

 

[chuck4]

I think for compact aircraft like fighters, serpentine ducts, by bending in this way and that inside the fuselage, required more internal room, and imposes constrains on internal layout. Both of which adds indirectly to structural weight. So it's not clear to me serpentine duct would be the better solution for all fighter requirements. I think it depends on the designer's perception of the comparative marginal benefit of last measure of stealth, and the marginal benefit of light and less bulky fuselage structure, which translates to higher agility, acceleration, range, and potentially better aerodynamics.


It seems to me the f-22 and f-35 opted for pursuit of last measure of stealth, j-20 and j-31 took their cue from f-22, the t-50 opted for lighter, simpler and less bulky structure in pursuit of higher range and kenematic performance.

 

[TaiidanTomcat]

I think for compact aircraft like fighters, serpentine ducts, by bending in this way and that inside the fuselage, required more internal room, and imposes constrains on internal layout. Both of which adds indirectly to structural weight. So it's not clear to me serpentine duct would be the better solution for all fighter requirements. I think it depends on the designer's perception of the comparative marginal benefit of last measure of stealth, and the marginal benefit of light and less bulky fuselage structure, which translates to higher agility, acceleration, range, and potentially better aerodynamics.


It seems to me the f-22 and f-35 opted for pursuit of last measure of stealth, j-20 and j-31 took their cue from f-22, the t-50 opted for lighter, simpler and less bulky structure in pursuit of higher range and kenematic performance.

At the same time though its very hard to say that the F-22 compromised much agility, acceleration, range, and aerodynamics. It seems to have the best of both worlds...

 

[Sundog]

I think for compact aircraft like fighters, serpentine ducts, by bending in this way and that inside the fuselage, required more internal room, and imposes constrains on internal layout. Both of which adds indirectly to structural weight. So it's not clear to me serpentine duct would be the better solution for all fighter requirements. I think it depends on the designer's perception of the comparative marginal benefit of last measure of stealth, and the marginal benefit of light and less bulky fuselage structure, which translates to higher agility, acceleration, range, and potentially better aerodynamics.


It seems to me the f-22 and f-35 opted for pursuit of last measure of stealth, j-20 and j-31 took their cue from f-22, the t-50 opted for lighter, simpler and less bulky structure in pursuit of higher range and kenematic performance.

Actually, serpentine ducts can make it easier to package everything within a given volume. For instance, the F-22's serpentine ducts made it easier to incorporate the side weapons bays, minimizing surface area, whereas the T-50 has to use under surface pods, increasing surface area, to incorporate the short range missile bays. As usual, everything is a trade off and both aircraft probably come close to meeting their requirements. Also, the T-50 wouldn't be considered simpler than an F-22 structurally speaking.

 

[overscan (PaulMM)]

I think for compact aircraft like fighters, serpentine ducts, by bending in this way and that inside the fuselage, required more internal room, and imposes constrains on internal layout. Both of which adds indirectly to structural weight. So it's not clear to me serpentine duct would be the better solution for all fighter requirements. I think it depends on the designer's perception of the comparative marginal benefit of last measure of stealth, and the marginal benefit of light and less bulky fuselage structure, which translates to higher agility, acceleration, range, and potentially better aerodynamics.


It seems to me the f-22 and f-35 opted for pursuit of last measure of stealth, j-20 and j-31 took their cue from f-22, the t-50 opted for lighter, simpler and less bulky structure in pursuit of higher range and kenematic performance.

Actually, serpentine ducts can make it easier to package everything within a given volume. For instance, the F-22's serpentine ducts made it easier to incorporate the side weapons bays, minimizing surface area, whereas the T-50 has to use under surface pods, increasing surface area, to incorporate the short range missile bays. As usual, everything is a trade off and both aircraft probably come close to meeting their requirements. Also, the T-50 wouldn't be considered simpler than an F-22 structurally speaking.

As I understand it the undersurface SRAAM pods actually help the shape to get nearer the ideal area rule for minimum drag. I am pretty sure the T-50 config is driven more by supercruise than you might imagine.

 

[Sundog]

As I understand it the undersurface SRAAM pods actually help the shape to get nearer the ideal area rule for minimum drag. I am pretty sure the T-50 config is driven more by supercruise than you might imagine.

Undoubtedly. They wouldn't place them to create more drag. That's simply a matter of you have to place the bays somewhere and you aren't going to place them where they cause more problems. The area rule (wave drag) for all super cruise aircraft is critical, so that will be one of the design drivers.

 

[Radical]

I think for compact aircraft like fighters, serpentine ducts, by bending in this way and that inside the fuselage, required more internal room, and imposes constrains on internal layout. Both of which adds indirectly to structural weight. So it's not clear to me serpentine duct would be the better solution for all fighter requirements. I think it depends on the designer's perception of the comparative marginal benefit of last measure of stealth, and the marginal benefit of light and less bulky fuselage structure, which translates to higher agility, acceleration, range, and potentially better aerodynamics.


It seems to me the f-22 and f-35 opted for pursuit of last measure of stealth, j-20 and j-31 took their cue from f-22, the t-50 opted for lighter, simpler and less bulky structure in pursuit of higher range and kenematic performance.

Actually, serpentine ducts can make it easier to package everything within a given volume. For instance, the F-22's serpentine ducts made it easier to incorporate the side weapons bays, minimizing surface area, whereas the T-50 has to use under surface pods, increasing surface area, to incorporate the short range missile bays. As usual, everything is a trade off and both aircraft probably come close to meeting their requirements. Also, the T-50 wouldn't be considered simpler than an F-22 structurally speaking.

As I understand it the undersurface SRAAM pods actually help the shape to get nearer the ideal area rule for minimum drag. I am pretty sure the T-50 config is driven more by supercruise than you might imagine.

I was always under the impression that the T-50 is better area ruled and less draggy than the F-22 considering its similar layout to the YF-23. The fact that the T-50's fuselage is comprised of pods (forward fuselage, engines, SRAAM bays) might make it easier to area rule than a big blocky body like the F-22's. I think I read somewhere that Sukhoi or Putin claimed the T-50 will have greater supercruise and max speed than the F-22.

 

[Sundog]

I was always under the impression that the T-50 is better area ruled and less draggy than the F-22 considering its similar layout to the YF-23. The fact that the T-50's fuselage is comprised of pods (forward fuselage, engines, SRAAM bays) might make it easier to area rule a big blocky body like the F-22's. I think I read somewhere that Sukhoi or Putin claimed the T-50 will have greater supercruise and max speed than the F-22.

I seriuosly doubt the T-50 will supercruise much faster than an F-22. Of course, it all gets down to what your definition of supercruise is at this point, as there is a thermodynamic limit and the F-22 is close to it, unless you're going to start building the entire plane out of Titanium, or if you're only supercruising for 20 to 30 minutes, instead of an hour. We would need more information on how they're defining it to know how much truth is in the statement. Also, the top speed statement again comes down to, at what altitude, for how long, and how much faster is faster?

Don't get me wrong, of all the 4.5/5th gen fighters, the T-50 is my favorite design, aesthically speaking, after the YF-23, and I'm sure it will be quite a capable aircraft. But some of the claims made by any side are sometimes superfluous with regard to operational capability and how they will actually be used.

 

[chuck4]

Actually, serpentine ducts can make it easier to package everything within a given volume. For instance, the F-22's serpentine ducts made it easier to incorporate the side weapons bays, minimizing surface area, whereas the T-50 has to use under surface pods, increasing surface area, to incorporate the short range missile bays. As usual, everything is a trade off and both aircraft probably come close to meeting their requirements. Also, the T-50 wouldn't be considered simpler than an F-22 structurally speaking.

I think that is backwards. Serpentine ducts only make it seemingly easier to package things because it forces the fuselage to be appreciably more volumnious to accommodate the ducts. If volume is really good give a straight ducted design a similarly volumnious fuselage and look how much easier and more efficient still would the packaging be. T-50 has to have the pods because its fuselage's otherwise enclosed volume is appreciably smaller.

 

[Wil]

Hello boys...!

...one more, © Dmitry Yakovlev. Nice!

 

[flateric]

14/01/13 (c) Sergey Sanin

 

[Radical]

I was always under the impression that the T-50 is better area ruled and less draggy than the F-22 considering its similar layout to the YF-23. The fact that the T-50's fuselage is comprised of pods (forward fuselage, engines, SRAAM bays) might make it easier to area rule a big blocky body like the F-22's. I think I read somewhere that Sukhoi or Putin claimed the T-50 will have greater supercruise and max speed than the F-22.

I seriuosly doubt the T-50 will supercruise much faster than an F-22. Of course, it all gets down to what your definition of supercruise is at this point, as there is a thermodynamic limit and the F-22 is close to it, unless you're going to start building the entire plane out of Titanium, or if you're only supercruising for 20 to 30 minutes, instead of an hour. We would need more information on how they're defining it to know how much truth is in the statement. Also, the top speed statement again comes down to, at what altitude, for how long, and how much faster is faster?

Don't get me wrong, of all the 4.5/5th gen fighters, the T-50 is my favorite design, aesthically speaking, after the YF-23, and I'm sure it will be quite a capable aircraft. But some of the claims made by any side are sometimes superfluous with regard to operational capability and how they will actually be used.

True, but the T-50's better area ruling isn't just limited to benefiting supercruise because it can also improve acceleration and other maneuvering performance. In addition, the T-50 has a wide flat fuselage with a flat area between the nacelles to add body lift. It seems like the T-50 with its better lift generation, lower drag and bleed will seriously outclasses the F-22 in maneuvering performance.

 

[chuck4]

Until the Russians come up with something better than the AF-31 or its derivatives, F-22 will have a decided advantage in installed power. Either F-22 will be able to carry more fuel for greater range, combat persistence, and longer supercruise, or will have better T/W ratio.

Also, F-22 has a big wide flat surface not between its engines, but under its engines. But more importantly, by pulling its engines close to the centerline, F-22 probably has smaller roll moment of inertia, thus may well have faster roll rate, thus might well be more agile.

Furthermore, look at the planform of the F-22. Even along the length axis, the F-22 seems to have its main concentrations of mass pulled closer to the center of mass than the T-50, while having its elevators further from the center of mass. So one might guess the F-22 also has lower moment of inertia about the pitch axis as well, while having greater pitch authority from its elevator. So F-22 might be more agile and responsive in pitch as well.

Without real numbers, just guessing from visual inspection, all sorts of outcomes in comparative evaluations are possible.

 

[kcran567]

Until the Russians come up with something better than the AF-31 or its derivatives, F-22 will have a decided advantage in installed power. Either F-22 will be able to carry more fuel for greater range, combat persistence, and longer supercruise, or will have better T/W ratio.

Also, F-22 has a big wide flat surface not between its engines, but under its engines. But more importantly, by pulling its engines close to the centerline, F-22 probably has smaller roll moment of inertia, thus may well have faster roll rate, thus might well be more agile.

Furthermore, look at the planform of the F-22. Even along the length axis, the F-22 seems to have its main concentrations of mass pulled closer to the center of mass than the T-50, while having its elevators further from the center of mass. So one might guess the F-22 also has lower moment of inertia about the pitch axis as well, while having greater pitch authority from its elevator. So F-22 might be more agile and responsive in pitch as well.

Without real numbers, just guessing from visual inspection, all sorts of outcomes in comparative evaluations are possible.

Chuck, that is a great assessment of the F-22. I never understood why the Russians think that the Centro plane is a good idea. The F-22 is better in all the ways you described. I'm not being biased, but that is the truth. The mass of the F22 and F-35 is located more centrally which is critical for fighter agility. The F-35s blending gets progressively smaller until you get to the stub wings, which are the thinnest part. on the T-50, its the exact opposite. Large masses outboard of the center-line That is more akin to the SR-71, having the engines outboard. Great for high speed, but negatively affects agility. Look at video of the A-12. The T-50 actually has a similar all moving tail. And as you mentioned the F-22s flat fuselage is a lifting surface, probably more efficient than the T-50. The F-35 and F-22 fuselage are supercritical airfoil shaped, curving upward along the bottom, the T-50 is just a flat pancake slab. The T-50 also has more wetted area which is less efficient.


The T-50 is interesting, but highly flawed. Has anyone here ever heard the (theory) that many Russian aircraft are purposely downgraded compared the western/US/European aircraft? Some even say many planted tech has led the Russians to go down some wrong design paths in the past. IE- the T-10 SU-27 prototype being based on the Rockwell design because the Russians mistakenly thought the "Gothic" wing shape and the Rockwell was a better design. Some of the tech on the Rockwell design was transferred to help them take the wrong path. Eventually, they had an expensive redesign process which cost them both money and time. Personally, I think the Russians chose the layout of the T-50 as being an next generation of the su-27 family overall design. They were familiar with it, and happy with it, but I still feel it is inferior to the F-35/22 aero shape.

 

[flateric]

Chuck, that is a great assessment of the F-22. I never understood why the Russians think that the Centro plane is a good idea.

ask that Grumman guys with F-14

Great for high speed, but negatively affects agility. Look at video of the A-12. The T-50 actually has a similar all moving tail. And as you mentioned the F-22s flat fuselage is a lifting surface, probably more efficient than the T-50

did you calculate lift coefficent via eye? agility? you yet to see what T-50 can do when current envelope restrictions will be dropped. so far, compare footage of Su-35 culbits at last shows to what Raptor can "(and can't) do

Has anyone here ever heard the (theory) that many Russian aircraft are purposely downgraded compared the western/US/European aircraft? Some even say many planted tech has led the Russians to go down some wrong design paths in the past. IE- the T-10 SU-27 prototype being based on the Rockwell design because the Russians mistakenly thought the "Gothic" wing shape and the Rockwell was a better design. Some of the tech on the Rockwell design was transferred to help them take the wrong path. Eventually, they had an expensive redesign process which cost them both money and time.

what an interesting BS

Personally, I think the Russians chose the layout of the T-50 as being an next generation of the su-27 family overall design. They were familiar with it, and happy with it, but I still feel it is inferior to the F-35/22 aero shape.

inferior in terms of what? measured in what? in your 'feelings'?

 

[flateric]

054 Red is on her way to Moscow (by her own)

 

[kcran567]

Flateric, I like the T-50 too. But was just trying to compare the design comparison trade-off between the centroplane concept and the flat, reverse airfoil, supercritical lifting fuselage as what is found on the F-22/35 with the mass mostly in the center-line vs. the mass outboard the center-line as in T-50. Just expressing an opinion. If F-14 flat pancake centroplane was so good and efficient on the F-14, how come we did not see its incorporation into the F-22, or any of the current American 5th Gen fighters or Chinese fighters. Only the Russians are using the centroplane as far as i know.

 

[Deino]

054 Red is on her way to Moscow (by her own)

Interesting to see that #04 has its number in RED !

 

[overscan (PaulMM)]

kcran567 your observations are very naive and easily turned around.

"The T-50 configuration is clearly superior in agility because the widely spaced engines increase the effectiveness of thrust vectoring. The F-22 and F-35 with their inboard engines can't generate the same roll rates".

In truth, there are pluses and minuses of each layout, but neither layout is clearly superior by eyeballing it. The design driver for inboard engines and boxy fuselage is stealth, not agility. In fact I believe the T-50 configuration is potentially more agile in almost every respect, which would accord with my gut feelings as to the design drivers.

 

[overscan (PaulMM)]

Traditional measures of manouverability we all know:

-
Wing loading
T/W ratio
Maximum climb rate
Maximum instantaneous turn rate
Specific Excess Power (Ps)
-

Note some more modern definitions of agility:

-
Pitch Agility
Time to pitch to maximum load factor plus time to pitch from maximum to zero load factor (i.e. how fast you can get to maximum pitching)

T90
Time to roll into and capture a 90 degree bank angle change (i.e how fast you can get into a high rate turn)

Torsional agility
turn rate divided by T90

Axial agility
The difference between minimum and maximum Ps available at a given flight condition divided by the time to transition between the two levels.


These newer measures relate to how quickly you can transition from one state to another. The Su-27 had excellent manouverability using traditional measures but compared to the F-16 for instance it was slower to reach maximum roll rate due primarily to the higher aspect ratio wing. Likewise, an excellent T/W ratio with an engine that takes 30 seconds to get to maximum thrust may be less use in combat situations than an engine with a lower T/W ratio which can get to maximum thrust in 10 seconds.

 

[2IDSGT]

kcran567 your observations are very naive and easily turned around.

"The T-50 configuration is clearly superior in agility because the widely spaced engines increase the effectiveness of thrust vectoring. The F-22 and F-35 with their inboard engines can't generate the same roll rates".

In truth, there are pluses and minuses of each layout, but neither layout is clearly superior by eyeballing it. The design driver for inboard engines and boxy fuselage is stealth, not agility. In fact I believe the T-50 configuration is potentially more agile in almost every respect, which would accord with my gut feelings as to the design drivers.

I asked a former GD engineer (aerodynamics) once about the widely spaced engines and TVC. He said something to the effect of "control along the flight axis (using surfaces) is generally better than control along the aircraft axis (using vectored thrust). He figured the wide-spaced engines were more about Russians sticking with what they know than about providing control authority.