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

collimatrix · by **collimatrix** » 27 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.

popcorn · by **popcorn** » 27 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.

sprstdlyscottsmn · by **sprstdlyscottsmn** » 27 Apr 2018, 13:40

They are also all moving

collimatrix · by **collimatrix** » 28 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.

sprstdlyscottsmn · by **sprstdlyscottsmn** » 28 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

collimatrix · by **collimatrix** » 28 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.

sprstdlyscottsmn · by **sprstdlyscottsmn** » 29 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.

mixelflick · by **mixelflick** » 29 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...

popcorn · by **popcorn** » 30 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.

collimatrix · by **collimatrix** » 02 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.

juretrn · by **juretrn** » 29 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?

juretrn · by **juretrn** » 29 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.

zero-one · by **zero-one** » 24 Jul 2018, 09:17

Don't they always say Russians are better at airshows? But even in a Demo the Raptor looks superior.

What makes it turn that fast even with fewer control surfaces and supposedly lower T-W ratio

wrightwing · by **wrightwing** » 24 Jul 2018, 10:22

zero-one wrote:

Don't they always say Russians are better at airshows? But even in a Demo the Raptor looks superior.

What makes it turn that fast even with fewer control surfaces and supposedly lower T-W ratio

Larger control surfaces, higher T/W ratio.

zero-one · by **zero-one** » 24 Jul 2018, 11:06

wrightwing wrote:Larger control surfaces, higher T/W ratio.

Thats what I thought. But I'm having a hard time finding the dimensions for both. If you have some I'd really appreciate it.

This is also why I find the 39,600 pound empty weight for the Su-57 a little dubious. I reckon it should weigh a little higher than that.

Militaryfactory.com has it slightly higher at 40,700+ lbs.
but the F-22 on that site weighs just 31,900 lbs so I'm skeptical