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
  • Author
  • Message
Offline

disconnectedradical

Forum Veteran

Forum Veteran

  • Posts: 581
  • Joined: 31 Dec 2010, 00:44
  • Location: Irvine, CA

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.
Offline

collimatrix

Active Member

Active Member

  • Posts: 149
  • Joined: 10 Jul 2016, 15:27

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.
Offline
User avatar

popcorn

Elite 3K

Elite 3K

  • Posts: 7505
  • Joined: 24 Sep 2008, 08:55

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.
"When a fifth-generation fighter meets a fourth-generation fighter—the [latter] dies,”
CSAF Gen. Mark Welsh
Offline

sprstdlyscottsmn

Elite 3K

Elite 3K

  • Posts: 3642
  • Joined: 10 Mar 2006, 01:24
  • Location: Phoenix, Az

Unread post27 Apr 2018, 13:40

They are also all moving
"Spurts"

-Pilot
-Aerospace Engineer
-Army Medic
-FMS Systems Engineer
Offline

collimatrix

Active Member

Active Member

  • Posts: 149
  • Joined: 10 Jul 2016, 15:27

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.
Offline

sprstdlyscottsmn

Elite 3K

Elite 3K

  • Posts: 3642
  • Joined: 10 Mar 2006, 01:24
  • Location: Phoenix, Az

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
"Spurts"

-Pilot
-Aerospace Engineer
-Army Medic
-FMS Systems Engineer
Offline

collimatrix

Active Member

Active Member

  • Posts: 149
  • Joined: 10 Jul 2016, 15:27

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.
Offline

sprstdlyscottsmn

Elite 3K

Elite 3K

  • Posts: 3642
  • Joined: 10 Mar 2006, 01:24
  • Location: Phoenix, Az

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.
"Spurts"

-Pilot
-Aerospace Engineer
-Army Medic
-FMS Systems Engineer
Offline

mixelflick

Elite 2K

Elite 2K

  • Posts: 2472
  • Joined: 20 Mar 2010, 10:26
  • Location: Parts Unknown

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...
Offline
User avatar

popcorn

Elite 3K

Elite 3K

  • Posts: 7505
  • Joined: 24 Sep 2008, 08:55

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.
"When a fifth-generation fighter meets a fourth-generation fighter—the [latter] dies,”
CSAF Gen. Mark Welsh
Offline

collimatrix

Active Member

Active Member

  • Posts: 149
  • Joined: 10 Jul 2016, 15:27

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.
Offline

juretrn

Senior member

Senior member

  • Posts: 364
  • Joined: 31 Jul 2016, 01:09
  • Location: Slovenia

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?
Russia stronk
Offline

juretrn

Senior member

Senior member

  • Posts: 364
  • Joined: 31 Jul 2016, 01:09
  • Location: Slovenia

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.
Russia stronk
Offline

zero-one

Elite 1K

Elite 1K

  • Posts: 1731
  • Joined: 23 Jul 2013, 16:19
  • Location: New Jersey

Unread post24 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
Offline

wrightwing

Elite 2K

Elite 2K

  • Posts: 2918
  • Joined: 23 Oct 2008, 15:22

Unread post24 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.
PreviousNext

Return to General F-22A Raptor forum

Who is online

Users browsing this forum: No registered users and 2 guests