Forum: Modern Military Aircraft

Good day, I was just cruising through some old photos on Lockheed Matin Codeone web sight When I came across this image.

Can you guys guess what it is?

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Without going to CodeOne? Dunno, an early ATF concept from GD?

You are correct. http://www.yf-23.net/GD.html

@1st503rdsgt. Oh very good, you know your stuff. All Codeone said was that it was early ATF design.

I was just looking through some of the ATF aviation art to see who designed it. I couldn't figure it.

http://www.yf-23.net/galleries/ATFconceptart.html

Oh tacf-x found it! Kudos!

No offense but I think this belongs in the Modern Aircraft section not the F-35 forum.

@taxf-x.....Your probably right, but since it was a really slow F-35 news day I thought I would throw something out there to liven things up. I really liked the inward vertical stabalizers on this model. I wonder why they didn't adopt them for the F-22 and F-35?

Wow. Almost 27 years ago! Hard to believe it's been that long.

alloycowboy wrote:

@taxf-x.....Your probably right, but since it was a really slow F-35 news day I thought I would throw something out there to liven things up. I really liked the inward vertical stabalizers on this model. I wonder why they didn't adopt them for the F-22 and F-35?

I'm not even close to being an aerodynamic expert... but I wonder how it would fair with the vortices created at high AoA?

A problem the F/A-18 faced was that the canted tails were flooded with the vortices coming off of the LERX at high alphas and then weakened and exploded into turbulent flow which caused aeroelastic structural issues such as fluttering and buffeting that matched the natural frequency of the stabs which caused resonance that resulted in serious structural fatigue and potential failure. I presume that is what you are worried about. In that case the inward stabs should avoid that problem by not being directly downstream of such turbulent flow.

I'm a junior in Aerospace engineering so I'm just now getting to the good stuff with fluid flow mechanics and all that. I'm not quite an expert but that is my input at least.

alloycowboy wrote:

@1st503rdsgt. Oh very good, you know your stuff. All Codeone said was that it was early ATF design.

I was just looking through some of the ATF aviation art to see who designed it. I couldn't figure it.

http://www.yf-23.net/galleries/ATFconceptart.html

It was an educated guess. As a technology historian I was able to pick out a few things in the picture.

1. It appears to show a date in 1985.

2. It looks kinda like an F-16.

3. It appears to be an attempt at LO.

tacf-x wrote:

A problem the F/A-18 faced was that the canted tails were flooded with the vortices coming off of the LERX at high alphas and then weakened and exploded into turbulent flow which caused aeroelastic structural issues such as fluttering and buffeting that matched the natural frequency of the stabs which caused resonance that resulted in serious structural fatigue and potential failure. I presume that is what you are worried about. In that case the inward stabs should avoid that problem by not being directly downstream of such turbulent flow.

I'm a junior in Aerospace engineering so I'm just now getting to the good stuff with fluid flow mechanics and all that. I'm not quite an expert but that is my input at least.

Enjoy the rest of your education, your into the fun part.

[quote="sprstdlyscottsmn"][quote="tacf-x"]A problem the F/A-18 faced was that the canted tails were flooded with the vortices coming off of the LERX at high alphas and then weakened and exploded into turbulent flow which caused aeroelastic structural issues such as fluttering and buffeting that matched the natural frequency of the stabs which caused resonance that resulted in serious structural fatigue and potential failure. I presume that is what you are worried about. In that case the inward stabs should avoid that problem by not being directly downstream of such turbulent flow.

The old Northrup XP530 originally had a conventional single verticle stab, but the lerx rendened the XP530 unstable, due to the high angle of attack blanking out the vertical stab. At that time the aircraft received twin vertical stabs canted outward to maintain yaw stability at very hign angles of attack. The first time I saw the F-18 do a slow speed dirty high alpha pass, I nearly dropped my dentures. The inward canted tails proved to be wholly ineffective for the same reason as the single vertical stab. The vortices on the YF-17 "burst on both sides at the vertical stabs causing the airframe buffet and structural fatique. The fix was a longitudal fence, which prevented the vortices from "bursting" on the vertical stabs, problem solved.

Forum: Modern Military Aircraft

Name the airplane