Objective comparison of F-22's and the T-50's aerodynamics?

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disconnectedradical

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Unread post04 Jan 2013, 08:03

I know that a lot of information regarding both airframes is classified, but given that we have high quality images of both the F-22 and the T-50, I think we can make some reasonable assumptions, estimates, extrapolations, and comparisons about the merits of each aircraft's aerodynamic shape.

Here are some pretty basic questions. Which aircraft appears to be overall less draggy? More specifically, at which regimes is each airframe better at? Which one has better adherence to area ruling? Which is more effective at generating lift and at what speeds?

If possible, I would like to minimize discussion on the powerplants and assume that both aircraft uses similarly rated engines. This isn't unreasonable; the so-called Type-30 engine that is supposed to supersede the interim 117 engine in the 2020 time frame is rated roughly the same as the F119. My reason for isolating this variable is that I strictly want to compare the merits of these two aircraft's aerodynamic qualities.
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neurotech

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Unread post04 Jan 2013, 18:13

disconnectedradical wrote:I know that a lot of information regarding both airframes is classified, but given that we have high quality images of both the F-22 and the T-50, I think we can make some reasonable assumptions, estimates, extrapolations, and comparisons about the merits of each aircraft's aerodynamic shape.

Here are some pretty basic questions. Which aircraft appears to be overall less draggy? More specifically, at which regimes is each airframe better at? Which one has better adherence to area ruling? Which is more effective at generating lift and at what speeds?

If possible, I would like to minimize discussion on the powerplants and assume that both aircraft uses similarly rated engines. This isn't unreasonable; the so-called Type-30 engine that is supposed to supersede the interim 117 engine in the 2020 time frame is rated roughly the same as the F119. My reason for isolating this variable is that I strictly want to compare the merits of these two aircraft's aerodynamic qualities.

The problem with this question is that there is nobody who would have access to the F-22 classified data and the same for the T-50.

Considering a F-22 can go from 60,000 ft, to a crater in under 60 seconds in idle power, tragically for the pilot. The F-22 would be considered Very Low Drag compared to other jets.

I asked a similar question a while ago, about how to analyze the performance of a T-50. The answer I received was basically that a RC model jet wouldn't give usable data, and the CFD modeling is not likely to give objective data, that would compare to actual flight test data.
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haavarla

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Unread post04 Jan 2013, 20:46

No doubt the Stabz on T-50 are low drag, perhaps even less drag than F-22 Stabz.
The angle on the PF wing are slightly more sharper sweeped back.

But then again the IRIST dome in front of Canopy produce drag..

The Pak-Fa T-50 seems to have a slightly larger Wing/body blended fuselage. Which gives it more lift surface(both wing and body).
This gives both Pros and Cons.
Pros in better range and Agility, but perhaps more drag as well.
Its impossible to calculate any results, but seen from a frontal view, the T-50 sure look sleek enough.
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firstimpulse

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Unread post05 Jan 2013, 18:43

In general, the PAKFA is optomised more for manuverability, and the Raptor is more about speed. I get to this conclusion not by looking at the aerodynamic details, but really what the respective manufactures of the craft care about.

The Russians have almost always prefered impressive agility over raw power/speed, and they've had to lean heavily in this direction over the past four or five decades because their electronics and engines simply don't measure up to their American counterparts.

That said, it would be very strange for the PAKFA to not be just as or more manuverable than the Raptor, and equally strange for the T-50 to be as steathy as the F-22.
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Unread post05 Jan 2013, 22:11

I think your wrong..
firstimpulse wrote:In general, the PAKFA is optomised more for manuverability, and the Raptor is more about speed. I get to this conclusion not by looking at the aerodynamic details, but really what the respective manufactures of the craft care about.

The MiG-25 is not very maneuverable, compared to the F-4 or F-15. The original Su-27 had to be redesigned because it would have had less maneuverability compared to the F-15. The Su-30 series with thrust vectoring came much later on. I think it first major demo of the TVC was in the Rockwell MBB X-31
firstimpulse wrote:The Russians have almost always prefered impressive agility over raw power/speed, and they've had to lean heavily in this direction over the past four or five decades because their electronics and engines simply don't measure up to their American counterparts.

Have you ever seen a MiG-29 up close? The F-16 & F/A-18 are more agile, but the MiG-29 has a better thrust to weight ratio. The MiG-28 doesn't count as it is an American design in non-Russian service :D That and its actually the F-5E except in Top Gun.
firstimpulse wrote:That said, it would be very strange for the PAKFA to not be just as or more manuverable than the Raptor, and equally strange for the T-50 to be as steathy as the F-22.

Maneuverability is about design choices. Stealth is about technology such as coatings and what materials are used for skins on the jet. I would be surprised if the T-50 could match the stealth of the F-22.
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haavarla

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Unread post05 Jan 2013, 22:56

Correct neurotech.
Its all about what requirements and thus design of choice. See Mig-25 and later Mig-31 and you get the point. Its what you want to acheive. The VVS wanted a very fast interceptor woth good range, and behold they got it.

The VVS has given its recommendation to Sukhoi, the requirements and all the fluffy stuffy specs.
The rest is up the Sukhoi i guess.
I'd say just by looking at the thing, its a well blended of different philosophy. It looks pretty fast and manuverable.
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Unread post06 Jan 2013, 18:11

disconnectedradical wrote:I know that a lot of information regarding both airframes is classified, but given that we have high quality images of both the F-22 and the T-50, I think we can make some reasonable assumptions, estimates, extrapolations, and comparisons about the merits of each aircraft's aerodynamic shape.
neurotech wrote:The problem with this question is that there is nobody who would have access to the F-22 classified data and the same for the T-50.
We don't need secret specifications in order to see what's visible, so I'll get it started...
  • Although it looked to me at first as if the T-50 had less backsweep in its leading edges, it's now pretty clear that its sweep is about the same as F-22's.
  • F-22's tail fins are larger, especially proportionally. T-50's entire slanted (not really "upright" or "vertical" on these planes) tail fins move, whereas F-22's have only a section at the back which does, making two of T-50's fins' movable control surfaces bigger than their F-22 counterparts despite total fin size being smaller.
  • T-50's nozzles, and thus the pivot points for thrust vectoring, are farther back, which would put them farther from the center of gravity. Meanwhile, F-22's tail fins, especially the horizontal ones, trail farther back (at least proportionally speaking), so the point at which they'd apply their force to turn the plane is farther back, and thus farther from the center of gravity.
  • T-50 is wider, which normally means more drag, particularly due to the fact that the main contributor to its width is the middle body, not wider wings. The wings are about the same size even though T-50 is bigger overall.
  • T-50 has a trench along the belly between the engine tunnels. F-22's belly is flat and smooth.
  • There's not really anything in front of F-22's air intakes except the cockpit and nose. T-50 has a wide, forward-protruding surface over the top of each intake. If I'm not mistaken, part of that also moves, presumably more to control airflow into the engines than to control the plane.
  • Where the wings join the central body (the wing root), on the bottom surface, T-50 has a distinct inner corner angle, making a clear place to say the side of the plane's body ends and the wing begins. F-22's wing root seems more blended with the body along the lower surface.
  • Drawing a line from wingtip to wingtip to separate the front and back of each plane, you'd find that a lot more of the T-50 is in front of that line than is behind it, whereas the front and back are more even on F-22.
  • The back of the T-50 is more abrupt and less tapered off, with two fins, two nozzles, and a thick stumpy stinger all roughly lined up with each other instead of the skinnier stinger and just the fins hanging out by themselves behind it like on the F-22.


What I infer from the above observations will have to come later because I don't have much time right now, but at least there are some real observable differences to infer effects from...
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haavarla

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Unread post06 Jan 2013, 20:38

The T-50 got a sharper back sweep angle of Main wings compaired to F-22.

Its called LEVCON. And they can move as elevators. Meaning its control surfaces, they move independently from each other, not optimizing airflow into the air intakes.

On takeoff/rotation we can see them function like carnards in a similar way(they points slightly upwards), see pic below.

The last pics show a T-50 parked at the side by a Su-27UB/Su-30.
Alltough the Flanker has a elevated canopy, we can clearly see the effort done by Sukhoi do make the T-50 as sleek as possible and pretty opted for higher Mach numbers. I would not speculate on any given numbers, but it give us a nice picture.
My point is, even this Flanker shown here has a good high Mach performance all things concidered. Then add all the extra thrust from the 117 engines, (12.500kgf vs 15.000kgf).
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PAK-FA_comparisons.jpg
su27t50f22comp1.jpg
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PAK-FA T-50 and Sukhoi 30 2.jpg
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neurotech

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Unread post06 Jan 2013, 21:51

delvo wrote:
neurotech wrote:The problem with this question is that there is nobody who would have access to the F-22 classified data and the same for the T-50.
We don't need secret specifications in order to see what's visible, so I'll get it started...

What I infer from the above observations will have to come later because I don't have much time right now, but at least there are some real observable differences to infer effects from...

Not disagreeing, or saying that any particular inference is incorrect. I was more referring to actual flight test data. We don't know what the tightest radius turn of a F-22, and at what airspeed. The corner airspeed of a F-16 or F/A-18 is in the -1 or -100, but no F-22 manual, especially not the -1 has released publicly. Then there is the ability of a jet to maintain energy in a turn, again, not released for the F-22. Sukhoi hasn't released this data for the PAK-FA either. The PAK-FA quite possibly has a operational T/W greater than 1:1, depending on fuel load, and ordinance.

There is a limit to how far the new 117/117S can go before really bad things happen. If the engine gets pushed too hard, it will either over-temp or have a compressor stall, or worse yet, a AB blowout induced "pop surge" which can result in either an engine fire, or a catastrophic hot-stage failure, in which using the K-36D ejection seat would become a real option. For the above reasons, all new engines have DEEC/FADEC that reduces the possibly of a catastrophic failure significantly. The AL-41/117 does have a FADEC, however that does not mean that over-optimistic limits couldn't result in an catastrophic failure. Non-DEEC J79 powered F-4s did occasionally have compressor stalls in afterburner, and NATOPS covers how to recover, but its still a major emergency for the pilot.
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haavarla

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Unread post06 Jan 2013, 22:50

I don't have any info on how long duration the 117S/117 engines can run on full AB.

But pls keep in mind that there are vids out there where jets like the Su-35S with its 117S engines use full AB(more or less) for a full 12min display over a 100.000 crowd of people. Do you think the Russian EAA, pilots and commanders are willing to just risk it if they was not confident in their products.
Anyway, the 117S like all other jet engines cannot sustain a very long duration on full AB due to the fact that the fuel consumption and fuel amount will act like a limiter on itself. So i think this is a none issue eighter way.
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firstimpulse

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Unread post07 Jan 2013, 00:02

neurotech wrote:I think your wrong…

We’ll have to agree to disagree. The MIG-25 was designed mostly to shoot down SR-71s, and personally I’d call it the exception, not the rule. I very much doubt the Luftwaffe pilots who flew the Fulcrum would agree with you when you say the Viper could outturn them. I’ve heard the Hornet has an impressive instant turn rate, but I also have heard its sustained turn wasn’t nearly as hot. Thrust vectoring is a moot point- neither the West nor East had it operational before the Cold War ended, unless you would count the Harrier.

But I'm getting off-topic with all this...
:|
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neurotech

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Unread post07 Jan 2013, 00:13

haavarla wrote:I don't have any info on how long duration the 117S/117 engines can run on full AB.

But pls keep in mind that there are vids out there where jets like the Su-35S with its 117S engines use full AB(more or less) for a full 12min display over a 100.000 crowd of people. Do you think the Russian EAA, pilots and commanders are willing to just risk it if they was not confident in their products.
Anyway, the 117S like all other jet engines cannot sustain a very long duration on full AB due to the fact that the fuel consumption and fuel amount will act like a limiter on itself. So i think this is a none issue eighter way.

I'd be surprised if it was "full" afterburner for 12 minutes, but the Sukhoi has a lot of gas inside. The pilot does monitor the EGT during flight, so if it was getting too high, the pilot could land immediately. Unlikely they'd push the known engine envelope at an air show. It can be even simple demo flights, not just airshows, that result in mishaps, such as the YF-22 flyby mishap.

What I was commenting on is that if the Sukhoi said "We need 40,000lb thrust per engine" (~ thrust of a F119 in the F-22) and the NPO Saturn engineers adjusted the FADEC for a test flight to test at a higher t/w ratio profile or max. speed dash or something along those lines, then a major mishap could occur.

I don't mean to suggest that the Russians have the monopoly on demonstration flight mishaps. The YF-16 prototype was damaged during practice for an airshow, and two F-20 demonstrators crashed during airshow practice.
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Unread post07 Jan 2013, 06:31

There are several ways to increase more thrust. I suspect Saturn went about the same way with the 117 as they did with the 117S engine.
Namly the increased the air intake size for more air to the fan compressors. Also they increased the fan blade diameters on the compressors too. And installed a more efficient low/high preassure fuel pump. And on top of this they installed a more complex FADEC system to control the engines.

The air intakes on the PF are rather large, and we don't know if they increased the forward compressor fan blades even more on the 117 engines to acheive more thrust.
The very notions that they would sacrifice TBO and full AB duration in order to run the engine hotter is not a good compromise, so i'm very sceptical about such approach.

Saturn made some very imprresive modification on the AL-31F engines over the years. No doubt the metalurgy has improved as well. like the cooling ability on the fan blades etc.
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Unread post07 Jan 2013, 06:35

Here is an interesting pics regarding the control surfaces and TVC on the Pak-Fa.

"PAK FA has highly relaxed longitudinal stability which is good for better trans-sonic lift to drag characteristics (L/D), supersonic L/D capabilities, low-speed lift characteristics and take-off and landing characteristics.
But highly relaxed longitudinal stability demands high pitch down control capabilities (specially at high AOA) and because positive load pitch down control surfaces (such as vertical stabilizers that are placed behind CG) tend to saturate under high AOA conditions, using negative load pitch down control surfaces (such as LEVCON that is placed in front of CG) is more effective.
The other thing is directional stability and controllability.
PAK FA has very small vertical stabilizers (decreased RCS, drag and weight), because relaxing static yaw stability and applying all moving rudders in combination with LEVCON and TVC can give very good results.
At high AOA vertical tails and rudders are placed in the low energy wake of the wing and fuselage. At certain AOA deflecting LEVCON`s can postpone creation of fuselage wake so the rudders can maintain effective. At some point (when further increasing AOA) low energy wake will form so the rudders become ineffective. Using asymmetrical LEVCON deflection can produce rolling or yawing moments at high AOA.
When we look at the photo we can see that the right LEVCON is deflected further, producing more negative pressure than the left one. The right wing has less deflected wing leading edge compared to left wing and aileron trailing edge is up (decreasing lift and applying negative pressure). There is also asymmetrical horizontal tail and TVC deflection and all that results in rolling/yawing motion to the right side.
At high AOA that would cause controlled wind-axis roll. One more thing is LERX vortex. Asymmetric LEVCON deflection will create differential/asymmetric vortex pressure distribution which in turn will cause additional yawing moments. In other words we will have controlled differential vortex pressure points. At high AOA`s asymmetric LEVCON deflection in combination with other control devices such as TVC can increase stability/controllability and yawing moment/rate and can generate direct side force (extreme maneuverability). And in case of TVC malfunction LEVCON represents an alternate form of pitch/yaw control that can provide redundancy.
"
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Unread post14 Jan 2013, 18:52

Based on available figures (i.e. guesswork), the T-50 has a lower wing loading, which should count in its favor one way or another.
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