Stealth and Aero Shaping: F-35 Versus F-22

The F-35 compared with other modern jets.
  • Author
  • Message
Offline

stereospace

Forum Veteran

Forum Veteran

  • Posts: 691
  • Joined: 21 Nov 2009, 17:35
  • Location: Columbia, Maryland, USA

Unread post10 Nov 2010, 00:23

Prinz_Eugn wrote:The F-22 block fuselage was a deliberate design decision early on in the program, mostly for simplicity reasons (cheaper to produce, get to RCS target). Take a gander at the YF-23 or even the PAK FA and see how blended those designs are. Pretty much every non-stealth design in recent memory has had more wing-body blending than the F-22, which should tell you there is a reason for it. . Getting away with more complex fuselage features like that (better airflow at normal flight regime) and still meeting RCS requirements is why I think the F-35 shouldn't be thought of as a half-baked F-22 design.


So, if I understand, you're saying the complex blending on the underside of the F-35 results in, "better airflow at normal flight regime", correct? Interesting. I would think the flat surface of the F-22 would experience less turbulence. It's obvious it would be cheaper to build since it's less complex, and it seems a flat surface would be stealthier (angle of incidence equals angle of reflection). The aerodynamic gains must be worthwhile, though it seems counterintuitive.
Offline
User avatar

popcorn

Elite 5K

Elite 5K

  • Posts: 7724
  • Joined: 24 Sep 2008, 08:55

Unread post10 Nov 2010, 01:52

I can see a strong family resemblance between the 2 jets.
"When a fifth-generation fighter meets a fourth-generation fighter—the [latter] dies,”
CSAF Gen. Mark Welsh
Offline

jeffb

Banned

  • Posts: 438
  • Joined: 16 Feb 2010, 08:00
  • Location: Australia

Unread post10 Nov 2010, 04:10

stereospace wrote:
Prinz_Eugn wrote:The F-22 block fuselage was a deliberate design decision early on in the program, mostly for simplicity reasons (cheaper to produce, get to RCS target). Take a gander at the YF-23 or even the PAK FA and see how blended those designs are. Pretty much every non-stealth design in recent memory has had more wing-body blending than the F-22, which should tell you there is a reason for it. . Getting away with more complex fuselage features like that (better airflow at normal flight regime) and still meeting RCS requirements is why I think the F-35 shouldn't be thought of as a half-baked F-22 design.


So, if I understand, you're saying the complex blending on the underside of the F-35 results in, "better airflow at normal flight regime", correct? Interesting. I would think the flat surface of the F-22 would experience less turbulence. It's obvious it would be cheaper to build since it's less complex, and it seems a flat surface would be stealthier (angle of incidence equals angle of reflection). The aerodynamic gains must be worthwhile, though it seems counterintuitive.


Early mockups of the F-35 had a flat bottom as well. APA pointed to the new "bumpy" bottom to claim that ah-ha, some of the stealth aspects of the F-35 have been compromised to fit everything in. Without access to an F-35 on-a-stick to do radar comparisons it's hard to say if that's true or not. As you point out LM claim that the changes to the bottom surface don't adversly affect it's stealth characteristics, if that's true then you might be looking at the evidence that stealth isn't about shape, shape, shape and coatings anymore. I assumed, as soon as I saw the F-22 years ago, that they'd improved the coatings dramatically over those used on the F-117, obviously the technology is evolving very quickly. Makes you wonder how the opposition is doing with it.
Offline

jimraynor

Newbie

Newbie

  • Posts: 16
  • Joined: 30 Jan 2010, 01:21
  • Location: New Jersey

Unread post10 Nov 2010, 04:50

Regardless of whether the "bumpy" bottom adversely affects stealth, every source out there says the F-35 is less stealthy than the F-22.
Offline

Tinito_16

Forum Veteran

Forum Veteran

  • Posts: 764
  • Joined: 31 May 2007, 21:46

Unread post10 Nov 2010, 06:53

Remember that the F-35 was designed to be mass-produce-able, i.e. by definition it wasn't going to have all the bells and whistles as far as stealth and speed that the F-22 has. Those are among the most expensive elements of a fifth-generation fighter. Not that it isn't stealthy or fast, it is. Just not to to the all out extreme that the Raptor was designed to be. And anyways, they probably got some of the stealth back just on improved computers and simulations. Remember, the F-22's design was finalized about 10-15 years before the F-35's was. Following Moore's Law, computer processing power increased exponentially (x1,000 +) in that time. You tell me that doesn't make a difference in cost to stealthiness...
"Like the coldest winter chill, heaven beside you...hell within" Alice In Chains
Offline

Prinz_Eugn

Forum Veteran

Forum Veteran

  • Posts: 961
  • Joined: 03 Aug 2008, 03:35

Unread post10 Nov 2010, 17:09

I don't really think the F-35 is stealthier than the F-22, it would be completely surprising if it was from more than a couple angles. The problem I have is that the F-22 is put on a pedestal and the F-35 is just assumed to be worse (worse aerodynamics particularly). The F-22 has various design boo-boos they didn't predict until they actually started flying them (clipped wingtips, reshaped stabs), just like the F-15 (clipped wings, dogtooth on the h. stab), and the F-4 (just... just look at an F-4).

As people have pointed out, the F-35 was designed over a decade later, which entails magnitudes of difference in the computing power available, plus all the lessons from the F-22 program. Thinking that the F-35 does not have any design improvements and the F-22 is the absolute pinnacle of everything aircraft design is kind of ridiculous to me.
"A visitor from Mars could easily pick out the civilized nations. They have the best implements of war."
Offline

wrightwing

Elite 3K

Elite 3K

  • Posts: 3697
  • Joined: 23 Oct 2008, 15:22

Unread post10 Nov 2010, 18:52

Prinz_Eugn wrote:I don't really think the F-35 is stealthier than the F-22, it would be completely surprising if it was from more than a couple angles. The problem I have is that the F-22 is put on a pedestal and the F-35 is just assumed to be worse (worse aerodynamics particularly). The F-22 has various design boo-boos they didn't predict until they actually started flying them (clipped wingtips, reshaped stabs), just like the F-15 (clipped wings, dogtooth on the h. stab), and the F-4 (just... just look at an F-4).

As people have pointed out, the F-35 was designed over a decade later, which entails magnitudes of difference in the computing power available, plus all the lessons from the F-22 program. Thinking that the F-35 does not have any design improvements and the F-22 is the absolute pinnacle of everything aircraft design is kind of ridiculous to me.


You also have to factor in the cost of implementation. Just because you can design something, doesn't mean that it will be cost effective. The F-35's stealth advantages are in ease of maintenance more than in lower RCS than the F-22.
Offline

Prinz_Eugn

Forum Veteran

Forum Veteran

  • Posts: 961
  • Joined: 03 Aug 2008, 03:35

Unread post10 Nov 2010, 19:24

Exactly. Which I think is an example of substantial improvement over the F-22's design- a practical level of Stealth that doesn't devour the MX budget.
"A visitor from Mars could easily pick out the civilized nations. They have the best implements of war."
Offline

f35phixer

Active Member

Active Member

  • Posts: 166
  • Joined: 13 May 2009, 22:38

Unread post10 Nov 2010, 22:38

Prinz got to it before me, Who says F-35 ISN'T Better!!!!!!!!!! You Might be surprised :devil:
Offline

exorcet

Active Member

Active Member

  • Posts: 154
  • Joined: 07 Oct 2009, 15:35
  • Location: US

Unread post10 Nov 2010, 23:08

stereospace wrote:
Prinz_Eugn wrote:The F-22 block fuselage was a deliberate design decision early on in the program, mostly for simplicity reasons (cheaper to produce, get to RCS target). Take a gander at the YF-23 or even the PAK FA and see how blended those designs are. Pretty much every non-stealth design in recent memory has had more wing-body blending than the F-22, which should tell you there is a reason for it. . Getting away with more complex fuselage features like that (better airflow at normal flight regime) and still meeting RCS requirements is why I think the F-35 shouldn't be thought of as a half-baked F-22 design.


So, if I understand, you're saying the complex blending on the underside of the F-35 results in, "better airflow at normal flight regime", correct? Interesting. I would think the flat surface of the F-22 would experience less turbulence. It's obvious it would be cheaper to build since it's less complex, and it seems a flat surface would be stealthier (angle of incidence equals angle of reflection). The aerodynamic gains must be worthwhile, though it seems counterintuitive.

Now that I think about it, the curved surface under the fuselage could just be there to shape the area distribution for supersonic drag.
Subsonic, I don’t see any obvious benefits, but they may do something to the boundary layer. A long flat surface usually just lets the BL build up.
f35phixer wrote:Prinz got to it before me, Who says F-35 ISN'T Better!!!!!!!!!! You Might be surprised :devil:

Well, the two planes have two different purposes, and price was a bigger concern for the F-35. It would be surprising if the F-35 was better than the F-22 in the supersonic regime considering that that is what the F-22 specializes in. The reverse is true as well.
Offline

stereospace

Forum Veteran

Forum Veteran

  • Posts: 691
  • Joined: 21 Nov 2009, 17:35
  • Location: Columbia, Maryland, USA

Unread post11 Nov 2010, 00:34

exorcet wrote:Now that I think about it, the curved surface under the fuselage could just be there to shape the area distribution for supersonic drag.


Could you explain/expound on that a little? Thanks!
Offline

exorcet

Active Member

Active Member

  • Posts: 154
  • Joined: 07 Oct 2009, 15:35
  • Location: US

Unread post11 Nov 2010, 05:08

It's the area rule

http://en.wikipedia.org/wiki/Area_rule

http://www.aerospaceweb.org/question/ae ... f102-1.jpg

To minimize the supersonic drag coefficient, the change in area along the length of the aircraft should be smooth (example, having a tubular fuselage with a pair of wings jutting out of the sides is much worse than having a fuselage that narrows along the chord of the wing).

There are a number of ways to control the area distribution. The F-102 used the method I described above, but the inverse it also true; instead of narrowing some section of the plane, you can make a different section wider. The bumps on the underside of the F-35 might make the area distribution more like the "ideal" curve in the F-102 photo (though the ideal shape changes slightly with different Mach numbers). I'm pretty sure that the bumps on the underside of the F-22's wings are there for supersonic drag reduction.
Offline

Rapec

Enthusiast

Enthusiast

  • Posts: 80
  • Joined: 15 Jun 2007, 10:13
  • Location: Poland

Unread post11 Nov 2010, 09:28

Hello

exorcet wrote:Subsonic, I don’t see any obvious benefits, but they may do something to the boundary layer. A long flat surface usually just lets the BL build up.


I'm no expert in aerodynamics but on the other hand those "bumps" may leadto BL seperation, which increased drag and IMHO is far more worse situation than slow BL build up along fuselage.

exorcet wrote:I'm pretty sure that the bumps on the underside of the F-22's wings are there for supersonic drag reduction.


I've never heard of applying the area rule to aircraft's wings. In my opinion those bumps serve as fairings to ailerons and flaperons drives.

Regards
Last edited by Rapec on 11 Nov 2010, 09:32, edited 1 time in total.
Offline

Rapec

Enthusiast

Enthusiast

  • Posts: 80
  • Joined: 15 Jun 2007, 10:13
  • Location: Poland

Unread post11 Nov 2010, 09:31

Double post, my fault.
Offline

exorcet

Active Member

Active Member

  • Posts: 154
  • Joined: 07 Oct 2009, 15:35
  • Location: US

Unread post11 Nov 2010, 15:50

Rapec wrote:I'm no expert in aerodynamics but on the other hand those "bumps" may leadto BL seperation, which increased drag and IMHO is far more worse situation than slow BL build up along fuselage.


That's certainly possible, although I don't know how that would slip through the design process unnoticed/unchanged.

I've never heard of applying the area rule to aircraft's wings. In my opinion those bumps serve as fairings to ailerons and flaperons drives.


The rule applies to everything, as long as the area along the lenght varies smoothly, you're good. You don't really apply the area rule to the fuselage, or to the wings, it has to account for the entire plane.
PreviousNext

Return to F-35 versus XYZ

Who is online

Users browsing this forum: No registered users and 10 guests