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

Anything goes, as long as it is about the Lockheed Martin F-22 Raptor
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disconnectedradical

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Unread post25 Jun 2015, 13:49

tacf-x wrote:
haavarla wrote:Those air intakes on T-50 sure looks interesting!

http://www.findpatent.ru/img_show/2733949.html


Upon translating the texts of the patent I have come to the conclusion that the Pak-Fa uses a 4 shock system with one wedge of the caret being moveable and the other caret wedge being fixed. Apparently each wedge turns the flow 3 times before the terminal shock at the throat. This would appear to give a much higher pressure recovery than the F-22 at mach numbers well above 2 but I am not quite so sure about how the F-22 handles the flow. I know the F-22 generates 2 adjacent oblique shocks on a caret intake but between those two shocks and the terminal normal shock I am not quite sure what happens. Also, there seems to be only one actuator behind the VG caret wedge which implies that the turning angles relative to each prior ramp are fixed on both wedges save for one on the VG wedge that results from the actuator. That would actually help reduce complexity vs. the F-15 and F-14. However most of the intake is actually fixed saved for a few degrees of freedom. That and there are probably still issues with shear layers forming between the caret wedge shocks at off-design mach numbers in a manner akin to the F-22 and F/A-18E.

In any case, this aircraft, like the F-22, should not have much problem with spillage even when the shock-on-lip critical starting conditions aren't achieved.


After reading the PAK FA patent it seems to be true that its inlet uses a 4 shock system (3 oblique and 1 normal, it seems). Interestingly I visited UCLA a few days ago and overheard a guy talking about the F-22 inlet, and he said that the F-22 has at least 2 shocks and likely has a compression ramp in front of the normal shock instead of more oblique shocks since the inlet ramp is a continuously curved surface instead of discreetly angled ramps like in the PAK FA. He mentioned that a compression ramp is probably a better at pressure recovery because it's closer to isentropic, though the envelope is more limited because surface geometry is fixed. He also said something about using the back pressure to control shock position and angle.
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collimatrix

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Unread post27 Apr 2018, 03:20

So, what's with the teeny-weeny vertical stabs on the SU-57? They're not just small compared to the F-22, they're small compared to the SU-27 as well. On top of that, the SU-27 has ventral fins and the SU-57 does not.
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Unread post27 Apr 2018, 03:26

collimatrix wrote:So, what's with the teeny-weeny vertical stabs on the SU-57? They're not just small compared to the F-22, they're small compared to the SU-27 as well. On top of that, the SU-27 has ventral fins and the SU-57 does not.


A concession to LO.
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Unread post27 Apr 2018, 13:40

They are also all moving
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Unread post28 Apr 2018, 00:07

popcorn wrote:
A concession to LO.


Are you sure? Part of the rationale for making the butterfly tail so gigantic on the YF-23 was that the tail would need to move very, very little. This would mean that the amount of control deflection even for extreme maneuvers would change the planform alignment of the entire platform very little. And like the YF-23, the SU-57 has all-moving vertical surfaces.
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Unread post28 Apr 2018, 00:21

collimatrix wrote:Are you sure? Part of the rationale for making the butterfly tail so gigantic on the YF-23 was that the tail would need to move very, very little. This would mean that the amount of control deflection even for extreme maneuvers would change the planform alignment of the entire platform very little. And like the YF-23, the SU-57 has all-moving vertical surfaces.

In the YF-23 those were also the primary pitch contributors as well. If you look at the YF-23 from the side the vertical component is fairly small
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Unread post28 Apr 2018, 20:41

sprstdlyscottsmn wrote:
collimatrix wrote:Are you sure? Part of the rationale for making the butterfly tail so gigantic on the YF-23 was that the tail would need to move very, very little. This would mean that the amount of control deflection even for extreme maneuvers would change the planform alignment of the entire platform very little. And like the YF-23, the SU-57 has all-moving vertical surfaces.

In the YF-23 those were also the primary pitch contributors as well. If you look at the YF-23 from the side the vertical component is fairly small


Good point.


I'm still not sure I buy the idea that the tiny stabs on the SU-57 are a concession to LO. F-22 has hugenormous vertical stabs, and it's almost certainly more LO than the SU-57.

I think the lack of ventral fins on the SU-57 is noteworthy too. Even the J-20, still has ventral fins.
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Unread post29 Apr 2018, 01:50

collimatrix wrote: F-22 has hugenormous vertical stabs, and it's almost certainly more LO than the SU-57.

The verticals on the F-22 use rudders, the verticals on the T-50 are all moving.
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Unread post29 Apr 2018, 14:15

Those F-22 verticals are enormous! I'd say they're very close to and F-16 wing, judging by the F-22 and F-16's I saw on static display at an airshow last year. Aren't those same enormous control surfaces key to its maneuverability?

I'll concede they were hideous on the YF-22A, almost as bad as the cockpit location LOL. But they're still big on the production F-22, which is quite different vs. the T-50/SU-57. Yes, yes I understand they're all moving on the SU-57 and that small due to LO considerations.. but I wonder if size is really everything here?

Likely not. Certainly angle, RAM coating etc play a big role. Whatever the case, it makes you wonder if these birds switched verticals how things would be different...
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Unread post30 Apr 2018, 00:10

Making vertical tails as physically small as possible would appeal to those not as advanced in the art and science of LO.
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Unread post02 May 2018, 05:35

popcorn wrote:Making vertical tails as physically small as possible would appeal to those not as advanced in the art and science of LO.


If it were a simple matter of the tails just being smaller, I would agree. But it isn't.

On the F-22 the entire leading edge of the vertical stabilizer is fixed, so that means it will reflect radar waves at a predictable angle. On the SU-57, the vertical stabilizer moves. Not only does this mean that the vertical stabilizer can reflect radar waves at a variety of angles, all of which need to be accounted for in LO optimization, but it also means that there is another reflective surface to account for, the interface between the fuselage and the vertical stabilizer.

I'm not sure it's a net gain for LO.
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Unread post29 Jun 2018, 02:33

ATF Program:

Competing engine demonstration/validation programs launched September 1983.

YF-119 and YF-120 (Variable Cycle) engines developed before any airframes, completed prototype engines in the late 1980s/early 1990s.

We had two 5th Generation engine prototypes already to go for the prototype aircraft, static and flight tested.

4 prototypes, 2 x YF-22 and 2 x YF-23 were ordered for evaluation of both engine types from P&W and GE.

In addition to generational leaps in pure thrust in mil and AB, the engines also had to have evolutionary FADEC and integration with the aircraft DFLCS, as well as VLO characteristics in RF and IR spectrums.

The engines preceded the airframes.

Sukhoi PAK-FA program:

They used AL-41F1 (117) derivative of the AL-31 from the Su-27, but know it isn't going to be the final production engine. Cart before the horse.

Many statements about when the AL-41F3/FU (30) will be ready, including in this very thread by the banned guy who implied special insight into the program. Where are we at in JUN2018?

They're testing an Su-57 with one AL-41F1 and one AL-41F3....

We had superior engines in 1988 folks, 3 decades ago. The basis for the next generation engine was already prototyped with the YF-120, and we're already well ahead on the 6th Generation engine that is Adaptive Cycle, advanced materials, substantial improvements over F119 and F135 in all aspects, 50k thrust rated.

It's almost sad. What nation is going to make the engines to propel the targets for our fighters? And you want to talk about aerodynamics? No engine, no plane. Sure, you can do "...super maneuverability demos for school-aged kids that have almost no relevance to combat." in the words of a senior Russian aerospace engineer, but what's going on with Russian military aviation?
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Unread post29 Jun 2018, 21:36

lrrpf52 wrote: "...super maneuverability demos for school-aged kids that have almost no relevance to combat." in the words of a senior Russian aerospace engineer

I'd love to read that for myself. Any source?
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Unread post29 Jun 2018, 23:22

juretrn wrote:
lrrpf52 wrote: "...super maneuverability demos for school-aged kids that have almost no relevance to combat." in the words of a senior Russian aerospace engineer

I'd love to read that for myself. Any source?

It's on video that seems to have never been meant for exposure to the US. One of their senior aerospace engineers gives a very dispassionate, sober analysis of the F-22, especially the F-35, with a little mention of the PAK-FA.

It was all translated with sub titles. You can tell they had a very keen awareness of the systems and what actually matters with the 5th Generation aircraft, versus what most of the public focuses on.

There are several statements that really stick out in the interview:

1. First, we should say that in US and our press, it was subject to all kinds of attacks, kicks, criticism, etc. They claimed that something is wrong, that it was this and that, expensive, etc. For the most part, these kicks were unjustified, and made by people who were far from specialists in these areas.

2. What should be said is that this is a huge event in the history of aviation development/manufacture. One should also remember that F-35 is already 2nd 5th Generation fighter in United States, and third from perspective of low radio-location visibility because 1st was F-117, then F-22 Raptor (that is only 179 units of them), and now F-35. We should also directly say that this fighter, according to its technical-tactical stats, has all the potential to repeat the success of F-16 fighter, which set the standards for a light fighter military machine in its class.

3. "What we noticed with F-35 is that for first time in combat systems development, they put same emphasis on software as hardware development, looking like more in the software. One can debate about hardware, but software in this plane is close to perfect, with very promising capabilities. In general, this plane should be looked at as link between these promising operative systems. Network-centric warfare.

4. Our conclusion is that they're focusing on air combat axiom that has been true since World War I: He who sees first, wins."

https://youtu.be/ScM_rN9a-js
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Unread post29 Jun 2018, 23:51

Thanks for this, lrrpf52.

Beyond the nationalistic chest thumping (see my sig), it would be really interesting to see what are the conversations like behind closed doors about the F-35, and what it enables, in places like Russia and China. What do their official reports say about it, things like that.
And judging by their propaganda media, they've got a major case of sour grapes going on.
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