YF-22 vs YF-23

I don't know if this was ever posted before.
There is a good paper by Lockheed's program manager Serman Mullin on the ATF

http://secure.afa.org/Mitchell/reports/MP9_ATF_0612.pdf

Spurts, I have a question about YF-23 and its wing trailing edge design.


Since the YF-23 basically has a diamond shaped wing, and the trailing edge of it is forward swept at about 40 or 45 degrees. Is it possible that do to that great forward sweep (seems emphasis was more for stealth factor) it would suffer more adverse yaw or even proverse yaw than if its ailerons were designed more perpendicular to the oncoming wind? And if it did indeed suffer more, wouldn't that further handicap the V tail (I will refer to it as "ruddervators") for the pitch (lateral) axis, since no separate vertical tails were technically designed for the yaw (vertical) axis? Could they also solve that issue (adverse/proverse yaw) by "unsymmetrical" aileron deflection instead of using a rudder or ruddervator?

Also, at high AOA wouldn't the V tail also have to be used somewhat for roll moments (longitudinal axis). Is it possible the ailerons might not be too effective at high AOA?

So I'm looking at the top view of the wing and I think you are alluding to the fact that due to the sweep of the actuator line the ailerons would not deploy perpendicular to the airflow. Under normal circumstances the increased lift comes with increased drag and adverse yaw.

With the YF-23 the deflected aileron also "scoops" the air toward aircraft centerline due to the sweep line of the actuator. This would produce some direct sideforce, but it would be the same if the aileron is defected up or down. The only difference is that the down control will produce a tad more due to greater total net AoA. These side forces are just a little behind the CG. The lower aileron producing a greater side force out behind the CG would actually help mitigate some of the adverse yaw I would think. I can't begin to guess about the magnitude of these forces. This would need a fun wind tunnel experiment. In the end I doubt there was any problem with control on the YF-23.

Thanks for the reply,




Was just wondering if they (USAF) wanted to play it "safe" in selecting the YF-22. I had a book from decades ago, that basically stated the AF wanted a F-15 extrapolated for stealth for the ATF--- and that is pretty much what they got with the F-22.

@eloise
I know logic dictates us to believe that the B-2 is stealthier than the F-22. And believe me I am inclined to believe that as well. However publicly released RCS figures say they are the same. And until I read anything that may suggest otherwise, I think my bias is justified

Published RCS figures is a single number.
RCS of an aircraft isn't a single value.
You can only see the significant differences between F-22 and B-2 on a radar scattering chart.
such as

The Lockheed concept for 6th gen only copied the V tails from the YF-23 and practically nothing else.

Why do you think these 6 gen concepts either copy the V-tails or have no tails?

You can only see the significant differences between F-22 and B-2 on a radar scattering chart.

I understand that, but since we dont have that chart we can't safely say how much better the B-2's RCS is. For all we know they could be similar, with negligible differences in most radar bands. Even if the B-2 offers the edge in RCS against LF radars, we don't know if the YF-23 will offer those same advantages as well.

Why do you think these 6 gen concepts either copy the V-tails or have no tails?

Because they offer certain advantages in RCS. I accept that. I can even accept that the YF-23 may have slightly lower RCS than the YF-22 or even the F-22.

But in the same breath, why has nobody adopted the pelican tail design, the X-32 almost adopted it before going to a conventional tail design. I think its because the slight reduction in RCS is too small to justify disadvantages like weight and the inability to use them for yaw and pitch at the same time.

And whos to say that there are no parts of the YF-22 that are better suited for stealth than the YF-23.

Hm I think Paul Metz in some interview said they achieved 2400km/h and were forbidden to go faster (F-22 testing).

The exact quote (which Paul Metz gave on one of the zillions of Discovery/TLC/History channel documentaries back in the late 90s/early 00s) was, "It's fast. I mean it's REALLY fast. The top speed is classified but it'll do sixteen hundred miles per hour."

@eloise
I know logic dictates us to believe that the B-2 is stealthier than the F-22. And believe me I am inclined to believe that as well. However publicly released RCS figures say they are the same. And until I read anything that may suggest otherwise, I think my bias is justified

Published RCS figures is a single number.
RCS of an aircraft isn't a single value.
You can only see the significant differences between F-22 and B-2 on a radar scattering chart.
such as

The Lockheed concept for 6th gen only copied the V tails from the YF-23 and practically nothing else.

Why do you think these 6 gen concepts either copy the V-tails or have no tails?

1. There is no weight disadvantage with the v-tail. The traditional tail design is the heavier and more complicated design. 4 electro-hyrdraulic actuators to control 4 surfaces, versus one-half of that to control 2 surfaces with the v-tail. The traditional design is also more expensive to manufacture and tool: piece price & tooling. The traditional design is likely more weighty.

2. The aerodynamics of the v-tail offer less drag. Had the YF-23 had a traditional tail like the YF-22, I doubt it's speed would be classified 30 years later.

3. V-tails have been around a very long time in aviation. The YF-23 used a flight control system that used all of the surfaces to achieve a desired action. Far more advanced than anything else ever flown to date.

4. The v-tail is stealthier

5. I doubt the YF-23 was only slightly better in LO than the YF-22. It was a magnitude in order smaller in IR because of the ingenious V-tail and trough design. Probably only the B-2 would have a smaller IR signature. That's amazing for a fighter. Considering the proliferation of IR sensors among our potential adversaries. The F-22 basically has no IR suppression at all. It relies on attacking enemies from the front and the fuselage blocking the IR signature from the front aspect.

I understand that, but since we dont have that chart we can't safely say how much better the B-2's RCS is. For all we know they could be similar, with negligible differences in most radar bands. Even if the B-2 offers the edge in RCS against LF radars, we don't know if the YF-23 will offer those same advantages as well.

The F-23 v-tail arrangement doesn't have a corner edge reflector in side aspect, while F-22 does. So even though F-22's corner edge is angled and shaped for stealth, it's still not as good as F-23 which does not have a corner edge there at all. That's physics. On the other hand, even F-23 side aspect probably isn't as good as B-2 since that has no tail.

So for stealth, B-2 is better than F-23 which is better than F-22, although all are still very good.

But in the same breath, why has nobody adopted the pelican tail design, the X-32 almost adopted it before going to a conventional tail design. I think its because the slight reduction in RCS is too small to justify disadvantages like weight and the inability to use them for yaw and pitch at the same time.

RCS benefit from a v-tail is not small. How is a v-tail heavier? Nothing from an engineering perspective says that arrangement is heavier than a 4 tail arrangement. Compare total area of v-tail with total area of horizontal plus vertical tail. F-23 bigger tail span does mean more bending moment, but F-22 horizontal tails are on booms that sticks behind the mains structure and needs to have beefier structure too, so you can't just make direct comparison.

Before fly-by-wire, v-tails are a problem because you get a lot of yaw and roll coupling, but with fly-by-wire that's not an issue anymore. Also v-tail might also be a problem for very low carrier landing speeds.

The F-22 basically has no IR suppression at all. It relies on attacking enemies from the front and the fuselage blocking the IR signature from the front aspect.

That's not really true, F-22's 2D nozzles do help cool the exhaust and flattens the plume which dissipates IR better. It's not as good as YF-23 exhaust trench but better than conventional nozzles.

Edit: Fix quoting mistake.

Comparing the F-22 to YF-23 or even a hypothetical F-23 (while an entertaining thought experiment) is at this point meaningless (even though I have enjoyed reading the discussion). We're comparing a known quality and quantity (F-22) to something that is half know (YF-23) and to something that is partially fantasized (F-23).

Would the YF-23 had been the better aircraft for the USAF? We will never know. Would the hypothetical F-23 be as good as everyone here wants it to be? Again we'll never know. If all factors outside the aircraft and program being equal, the F-23 most likely would have met the same fate as the F-22; dramatically neutered numbers and capabilities reduced for cost reasons.

Another thing is that people point to concept art of Lockheeds 6th gen fighter as "proof of validation" for the YF-23. Oh hey looks like strikingly similar to the YF-23 there for it must have secretly been the winner. Look at how many conceptual designs have been made throughout the years. How many existing or current aircraft look like those artist concepts and renderings?

1. There is no weight disadvantage with the v-tail. The traditional tail design is the heavier and more complicated design. 4 electro-hyrdraulic actuators to control 4 surfaces, versus one-half of that to control 2 surfaces with the v-tail.

https://www.airspacemag.com/military-av ... c=y&page=2

The bigger hydraulic pumps and cylinders needed to operate the larger surfaces would end up adding at least 200 pounds to the design.

If a meager 200 lbs was enough for them to back off from the design, then that could mean that reduction in RCS is too small to justify this tiny weight increase. I can't imagine them giving up on far superior RCS readings for a tiny 200 pound weight increase.

2. The aerodynamics of the v-tail offer less drag. Had the YF-23 had a traditional tail like the YF-22, I doubt it's speed would be classified 30 years later.

The F-22's top speed is also classified, the YF-22's top speed? classified too. In fact both YF-22 prototypes were tested to faster top speeds than both YF-23 prototypes.

3. V-tails have been around a very long time in aviation. The YF-23 used a flight control system that used all of the surfaces to achieve a desired action. Far more advanced than anything else ever flown to date.

And yet, achieved less maneuverability, was tested to a lower top speed. Listen, I'm not saying the YF-22 was faster, it could be, but I'm not going there. V tails have been around for some time, you're right, but why is no one using them.

4. The v-tail is stealthier,

We don't know that for sure. If it was far superior than a conventional tail then why is no one using it. We often give TVC a bad rep because it only offers slightly better performance than conventional tails, but at least that technology has actually made its way to production variants of many front-line fighters. Absolutely no one HAS considered V tails a worthwhile investment.

5. It was a magnitude in order smaller in IR because of the ingenious V-tail and trough design. The F-22 basically has no IR suppression at all. It relies on attacking enemies from the front and the fuselage blocking the IR signature from the front aspect.

Tell that to the Typhoon, Rafale, F-15, F-16 and F/A-18 pilots who carry the best integrated and podded IRST who are getting ripped apart by the Raptor in BVR simulation. The F-35 also uses conventional tails and is killing IRST equipped fighters whole sale.

The F-23 v-tail arrangement doesn't have a corner edge reflector in side aspect, while F-22 does.

Yes I understand that, but how much better? Some people may be thinking that it is in orders of magnitude better. Maybe -60 db. Personally I believe that the difference was negligible, -45 db perhaps.

RCS benefit from a v-tail is not small. How is a v-tail heavier? Nothing from an engineering perspective says that arrangement is heavier than a 4 tail arrangement.

Those were not my words. Boeing said that.
https://www.airspacemag.com/military-av ... c=y&page=2
They had a delta design for the X-32. But then the Navy requested for increased maneuverability. So they chose between Pelican and conventional tail. They went with Pelican, however it became heavier and went back to conventional tail.

That's not really true, F-22's 2D nozzles do help cool the exhaust and flattens the plume which dissipates IR better. It's not as good as YF-23 exhaust trench but better than conventional nozzles.

Personally I think the YF-23's trench has most of its advantages in max AB. the visible plume will be shorter from the bottom and side angles.

But in mil power or low AB, both designs offer comparable IR suppression. Again I go back to the Report where 1 F-22 went up against 8 F-15Cs with Aim-9X and won. If you don't believe the article, thats fine, I believe it and unless I see a credible article directly disputing it, I'll continue to believe it.
https://fightersweep.com/2526/helmet-mo ... -the-f-22/

Without JHMCS or HMIT, the F-22 has already shown it can fare just fine. In an engagement eight years ago, two F-22s were to take off and engage eight F-15Cs from the 65 AGRS, all equipped with AIM-9X and JHMCS. One of the Raptors ground-aborted, so the second jet took off single-ship as fragged. The engagement started beyond visual range and finished within visual range, with the Raptor killing all eight of its opponents before any were able to even get a shot off.

I understand that, but since we dont have that chart we can't safely say how much better the B-2's RCS is. For all we know they could be similar, with negligible differences in most radar bands. Even if the B-2 offers the edge in RCS against LF radars, we don't know if the YF-23 will offer those same advantages as well.

You don't have the chart for F-18 E/F vs F-35 either, but it is quite safe to say F-35 offer much better RCS.
B-2, F-23 have no acute corner when viewed from the side, F-22 does, so the formers will have much better side RCS, it is physics.
No angle between the vertical and horizontal tails also eliminate the traveling wave return effect from that part. Secondly,the smallest control surface on F-23 is bigger than the smallest control surface on F-22, that also delay the low frequency (mie region) effect.

But in the same breath, why has nobody adopted the pelican tail design, the X-32 almost adopted it before going to a conventional tail design. I think its because the slight reduction in RCS is too small to justify disadvantages like weight and the inability to use them for yaw and pitch at the same time.

And whos to say that there are no parts of the YF-22 that are better suited for stealth than the YF-23.

Agility was very important by the time ATF program was running, pelican tail is less maneuver and possibly very complex in term of control and that add risk to development.
Can you name one feature of F-22 that is more suited for stealth than F-23?
If you can't then it is an empty argument

If a meager 200 lbs was enough for them to back off from the design, then that could mean that reduction in RCS is too small to justify this tiny weight increase. I can't imagine them giving up on far superior RCS readings for a tiny 200 pound weight increase.
And yet, achieved less maneuverability, was tested to a lower top speed. Listen, I'm not saying the YF-22 was faster, it could be, but I'm not going there. V tails have been around for some time, you're right, but why is no one using them.

4. The v-tail is stealthier,

We don't know that for sure. If it was far superior than a conventional tail then why is no one using it. We often give TVC a bad rep because it only offers slightly better performance than conventional tails, but at least that technology has actually made its way to production variants of many front-line fighters. Absolutely no one HAS considered V tails a worthwhile investment.

No one? V-tail may be inferior to conventional tails in maneuverability but in term of signature, it is absolutely superior, it is used a lot on UAV where stealth is required

Tell that to the Typhoon, Rafale, F-15, F-16 and F/A-18 pilots who carry the best integrated and podded IRST who are getting ripped apart by the Raptor in BVR simulation. The F-35 also uses conventional tails and is killing IRST equipped fighters whole sale.

That is a bit disingenuous to use an example of conventional legacy fighters versus stealth fighter to prove a point about IR signature between 2 stealth aircraft

Personally I think the YF-23's trench has most of its advantages in max AB. the visible plume will be shorter from the bottom and side angles.
But in mil power or low AB, both designs offer comparable IR suppression.

Even in mil power or low AB, the exhaust gas doesn't cool down to ambient temperature right at the end of the flame length, so the design of F-23 will give them much greater distance to cool down to before they could be viewed by ground or air sensor at lower altitude.

Again I go back to the Report where 1 F-22 went up against 8 F-15Cs with Aim-9X and won. If you don't believe the article, thats fine, I believe it and unless I see a credible article directly disputing it, I'll continue to believe it.
https://fightersweep.com/2526/helmet-mo ... -the-f-22/

Without JHMCS or HMIT, the F-22 has already shown it can fare just fine. In an engagement eight years ago, two F-22s were to take off and engage eight F-15Cs from the 65 AGRS, all equipped with AIM-9X and JHMCS. One of the Raptors ground-aborted, so the second jet took off single-ship as fragged. The engagement started beyond visual range and finished within visual range, with the Raptor killing all eight of its opponents before any were able to even get a shot off.

there is fair reason for him not to believe that. The more official article didn't have these bits

Can you name one feature of F-22 that is more suited for stealth than F-23?
If you can't then it is an empty argument

Can you show us a legitimate straight from Northrop Grumman and McDonnell Douglas paper about how the YF-23 or F-23 would have been better in this regard? Most if not all people (here and else where) will agree that the YF-23 is or at the very least would have been more stealthy. The F-35 which has been touted to be more stealthy than the F-22 uses many design elements from the F-22 (albeit more refined).





The F-22 is already considered VLO and pretty much set a very high standard to meet or overcome. So given that the F-35 is considered to be more stealthy than the F-22 and that the F-35 uses more refined design elements of the F-22, how much more stealthy is the YF-23 or hypothetical F-23 is to the F-35?