The Cobra is still of no tactical value. And the YF-17 was doing it years ago.

Assuming that you`re refering to the “hang and look” maneuver the YF-17 did a decade before the Flanker. Then why telling this nonsense that it had no tactical value when the Vice president of the Northrop corp. in his article “Evolution of the hybrid wing YF-17/F-18” wrote about COMBAT MANEUVERS such as “hang and look”. I wonder what makes YOU to say the contrary? Do you at least have a clue of what maneuver he is talking about? Was the Northrop YF-17 doing the high AOA manuever testing just for fancy to amuse the crowd in the seventies?Anyway, tell us please what angles of attack were achieved in the “hang and look” manuever. thanks

Yes, the characteristics of a delta is based on the function of the leading edge swept angle, but the strength and breakdown characteristics are highly sensitive to the leading edge radius and trailiing edge conditions.

Apparently, you seem to agree with my previous statement that delta wings are mainly defined by the function of the leading edge sweep. But there is still your “controversial” convention. I say, the F-22 wing has low wing sweep which is neither characterized by LE flow separations nor it has a zero deg TE angle(-20deg whereas the TE of the Su-27 is 15deg). But when counting the whole aerodynamic configuration, we have to consider the F-22 nose/intake chines and nose chine/strakes of the Su-27. The flow field about the Su-27 main wing at non-zero angle of attack is dominated by the complex 3D separated flow as well as the flow about the F-22, bcs of two strong vortices generated by the large, sharp with variable camber leading edge extensions(LE angle~70deg). The high swept angle forewing of the Su-27 attached to the main wing (to form double-delta wing) consistently altered the aerodynamic characteristics of the main wing, but no one ever called it the double-delta wing.:)

I don’t know why you keep quoting those aiaa papers as if somehow that mean you fully understand what they meant. Have you ever consider that some here wrote some of those or similar papers you just quoted?

I`m sorry, but I never considered that and when I`ve read your remarks, rather I doubted you ever read them.

Especially looking at cambers and nose chine, the lift progression is very different.I don’t dare to say i know the aerodynamics of F-22 (it is classified) what is say is that your points don’t make thoses aeros “not good”.
.

Ogami, I never said that F-22 horiz. stabs are not good. I`ve said they have to be so “BIG” to be good!!! That is different, isn`t it? The F-22 aerodynamics layout is neither classified nor a breakthrough, rather a compromise because of stealth planform alignment.
The F-22 nose and intake chines are not very effective in maintaining stable vortex structures when compared to variable cambered lerx of YF-17, F/A-18, F-16, Su-27, Mig-29. They apparently miss shape properties, well described in that above mentioned article. All the lift job does the wing, no doubt a real masterpiece with complex camber, slightly twisted down leading edge of the outboard wing section with anhedral. When you analyze the aerodynamics changes from the YF-22 to F-22, you`ll get a clear picture what were LM engineers improving and why.

Alright Martin, let’s start with the most basic…tell me why the wing on the F22 is not a delta wing? Any self-respecting aerodynamicist in the world with any credibility calls it a delta wing. Tell me what the definition of a delta wing is then? That i like to learn.

The leading edge sweep is the crucial and primary factor for creating the delta wing vortex structure. The aspect ratio of delta wings is defined as AR = 4/tan(D), AR<3, where D is the leading edge sweep angle. Delta wings are mainly characterized by sweep angles around 60deg (or higher) which are better suited for supersonic cruising and known for the non-linear aerodynamics. Both the F-22 and Su-27 have the same LE sweep angle of 42degree which is not a delta wing!!. The F-22 has a trapezoidal wing planform just like the Su-27. The equation AR=B^2/S should not be applied(misleading), bcs you still get low-aspect ratio(as deltas) when you design a trapezoidal wing with e.g. LE/TE 20deg. See my point?

source of the AR equation

Prediction of Delta Wing Leading-Edge Vortex Circulation and Lift-Curve Slope
http://pdf.aiaa.org/jaPreview/JA/1997/PVJAIMP2193.pdf

best regards
martinez

Your pompous and dismissive attitude is sadly typical of those who just cannot comprehend a reality in which their beloved Flanker is not the be-all and end-all of aerodynamic achievement..

Thanks a lot for opening my eyes:) , I highly apprieciate that you pointed out at this AIAA article. I`ve been looking such an article(US source) for some time. This has to be the “unshakable” evidence for many of my arguments from now on.

That the YF-17 routinely performed a maneuver which today would immediately be recognized as the cobra is not a “belief,” it is a fact..

I`m not sure whether you read or not the whole article, but apparently you did not understand a think from it. Do not worry, I explain. The article very nicely describes the YF-17 flight performance due to its hybrid wings. The figure 21 shows the yaw rate/angle of attack envelope obtained during the YF-17 flight test program. They say that those high angle of attack “combat maneuver” such as high “G” barrel rolls and “hang and look” maneuvers never exceeded these limits!!!. That basically proves what I`m telling here from the beginning. The YF-17 performed those combat manuevers up to 52deg AOA only!!! what is not even a half of “controversial” COBRA manuever(120 deg AOA). As you probably have seen many times on airshows/aeroexhibitions, the F-18 pilots like to show “brutal” pull-up maneuvers what is actually the part of the heritage(hybrid wings) comming from the YF-17 development. Although these are manuevers performed by any other 4-gen fighters these days…Rafale, Eurofighter, Mirage, Mig and Sukhoi.

Unfortunately, that article isn’t free, and I’m not personally inclined to contribute $25 to your education.

Now, it is time to educate you!! :rolleyes:
What makes the Cobra maneuver possible?
http://pdf.aiaa.org/preview/1993/PV1993_183.pdf
Unsteady aerodynamics of combat aircraft maneuvers
http://pdf.aiaa.org/preview/1997/PV1997_3647.pdf
Estimation of aircraft models in Cobra maneuvers through dynamic inversion
http://pdf.aiaa.org/preview/1994/PV1994_3494.pdf
The Cobra maneuver as a minimum time problem
http://pdf.aiaa.org/preview/1997/PV1997_3586.pdf
Problems of Manoeuvring at Post-Critical Angles of Attack
http://pdf.aiaa.org/preview/CDReadyMASM03_582/PV2003_395.pdf
High-Alpha Flight Maneuverability Enhancement of a Twin Engine Fighter-Bomber Aircraft for Air Combat Superiority Using Thrust-Vectoring Control
http://pdf.aiaa.org/preview/CDReadyMGNC06_1305/PV2006_6056.pdf

End of Cobra story
Best regards
Martinez

[QUOTE=ogami musashi;1077602]

Quite an assertion, as the hor. tail effecitivity at thoses AOA is dependant on his position relative to the speed vector, and that the wake of the wings depends on the flows behavior.

Do we still need to play with words? I`m quit bored….please read my remarks twice, you`ll understand what I`m talking about. I`m done hear.

best regards
Martinez

Please, do not patronize me. I am well aware of the difference between an aircraft’s name and the name of an airshow maneuver, thank you.

As SOC as mentioned in this forum on more than one occasion, the YF-17 routinely performed this maneuver during airshows in the 1970s. It wasn’t called the “cobra” back then (SOC may know for sure); the name wasn’t given to it until Pugachev started performing it in the Flanker…years later.

Believe what you want, I’m not going to stop you, but unlike gravity and the wind, you don’t have a shred of evidence for your belief. I wonder how long it will take that someone older come and starts claiming that cobra was performed in 60-ies by the F-104 then you would probably believe him too. I doubt he remembers a …., when he played with a duck during that time.:rolleyes: