F-35 vs F-16

[Exorcet]

There will be separation issues only if air off the bottom separates and remains that way when it gets to the LERX, but that would make them pointless. I wouldn't expect much separation at all over the top of the fuselage. Maybe there is a little bit of vortex formation on the sides of the inlets, but I don't think they will have a big effect.

 

The F-15 doesn't seem to have any issues.

 

And of course there is the F-35 image itself a few posts up.

[aaron886]

This results in a less than optimal leading edge for the air to work itself around in the fuselage area, resulting in seperation and a low L/D ratio.

 

This has the same ring of authenticity as the "air cushion" explanation of ground effect. :music_whistling:

[Hummingbird]

There will be separation issues only if air off the bottom separates and remains that way when it gets to the LERX, but that would make them pointless. I wouldn't expect much separation at all over the top of the fuselage. Maybe there is a little bit of vortex formation on the sides of the inlets, but I don't think they will have a big effect.

 

The F-15 doesn't seem to have any issues.

 

And of course there is the F-35 image itself a few posts up.

 

So you're saying that you're not seeing the difference between the F-16, -18 & F-15 here? To me it's quite clear and pronounced.

 

Edited May 13, 2015 by Hummingbird

[Sierra99]

The F-35 has Chines instead of LERX.

 

Lets try this again...

 

Where do you see chines on the F-35? Are you sure you are referring to the right part?

 

Sierra

[Emu]

I think he's referring to the horizontal split running along the aircraft. It's sort of a chine I guess.

[Exorcet]

So you're saying that you're not seeing the difference between the F-16, -18 & F-15 here? To me it's quite clear and pronounced.

Separation was mentioned specifically, I don't think the F-35/15 type fuselage will see significantly more separation than aircraft with larger LERX.

 

While your images do show more vapor, I wouldn't try to judge the actual vortex strength from images alone. At the very least you'd want images of the planes flying in the same conditions, but even then it's not going to be very good for quantitative analysis. I'll agree that larger LERX leads to a larger vortex, but that does not necessarily mean greater efficiency across the board.

[tflash]

So you're saying that you're not seeing the difference between the F-16, -18 & F-15 here? To me it's quite clear and pronounced.

 

 

If you can "see" lift than you have a sixth sense, I only see a vortex, imho a little bit high over the wing to really contribute to lift, but that's just an opinion. Fact is that the Lerx acts as a giant airbrake in these manoeuvres, weather this generates extra lift seems to me highly debatable, I would rather think the aircraft is vertically losing altitude in high AOA.

[aaron886]

You are looking at a low-pressure vortex (hence the condensation,) which is essentially what lift is. But again, I agree that this is a weak analysis. Too many factors involved. For what it's worth, there is a point past which having a stronger LEX vortex is a detriment rather than an advantage.

 

Lets try this again...

 

Where do you see chines on the F-35? Are you sure you are referring to the right part?

 

Sierra

 

Sounds kind of demanding... :huh:

Look at the shadow caused by the "lip" above the intake. (Above where it says Danger Jet Intake.) That "lip" is called a chine.

[Hummingbird]

Edited May 14, 2015 by Hummingbird

[Exorcet]

Does that source contain information more specific about LERX design? Those general points make sense, but they don't really give any method for ranking designs. The closest would be the reference to breakdown AoA. Also, fuselage lift isn't solely vortex dependent. Even the CL graph you posted isn't if it's for the entire plane. The vortices will help draw freestream air over the wings/fuselage.

[Basher54321]

This is from a 1972 GD F-16 presentation by Harry Hillaker:

 

 

 

 

Improved things for that F-16 configuration sure back then - however that is no basis for any real comparison with another airframe.

[Sierra99]

Sounds kind of demanding... :huh:

 

Well, first time I asked the question the post disappeared...Not demanding, curious.

 

Look at the shadow caused by the "lip" above the intake. (Above where it says Danger Jet Intake.) That "lip" is called a chine.

 

LOL...Those little things...I'm not sure those meet the definition of a Chine but if you can show me something official that refers to those as Chines and I'll buy it. I think you'll find they fall into the category of strakes.

[aaron886]

LOL...Those little things...I'm not sure those meet the definition of a Chine but if you can show me something official that refers to those as Chines and I'll buy it. I think you'll find they fall into the category of strakes.

 

Er... ok. :dontgetit:

 

This is a chine: http://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/A-12_Nose_View.jpg/1280px-A-12_Nose_View.jpg

 

This is a strake: http://www.b-domke.de/AviationImages/Typhoon/Images/Typhoon_ZJ924_12461.jpg

 

Often (and sometimes inappropriately) interchanged terms. I could be reading into it too much, but your tone comes across as a bit condescending and rude.

[Hummingbird]

Does that source contain information more specific about LERX design? Those general points make sense, but they don't really give any method for ranking designs. The closest would be the reference to breakdown AoA. Also, fuselage lift isn't solely vortex dependent. Even the CL graph you posted isn't if it's for the entire plane. The vortices will help draw freestream air over the wings/fuselage.

 

It has nothing to do with fuselage lift, which certainly isn't vortex dependant (as you rightfully point out), it's all about the increase in lift gained over the main wings by the addition of large LERXs, esp. on blended wing designs where the vortice is unobstructed along the entire length of the a/c.

 

Also we're not just talking a single vortex here, the F-16 enjoys the benefits of several vortices generated at certain flight attitudes:

 

 

 

In regards to fuselage lift the F-16 enjoys an advantage over the F-35 here quite simply due to its more aerodynamically optimized shape, mostly in the form of an airfoil (no worries about radar deflection in the design here), which results in a higher L/D ratio. Crucially on the F-16 the air starts by impacting a sharp leading edge ensuring a smooth transition over & under a carefully curved surface for the rest of the airframe. By comparison on the F-35, with the exception of the nose (& wings but we're talking fuselage area only here), the airstream is first met by two large air intakes, the result of which is a given.

 

In short at certain AoAs the F-35 might (and I put high emphasis on the word "might" here) enjoy more lift overall from its fuselage due solely to its larger surface area, but it will gain this a lot less efficiently.

Edited May 15, 2015 by Hummingbird

[BronzeBuddha]

Hummingbird, are you seriously trying to compare vortex strength and lift characteristics of low aspect ratio aircraft by eyeballing?

 

That is absurd.

[Hummingbird]

Hummingbird, are you seriously trying to compare vortex strength and lift characteristics of low aspect ratio aircraft by eyeballing?

 

That is absurd.

 

No, I'm doing what we're all doing here (except you atm): Debating the design of the F-16 & F-35 in detail.

 

Until specific figures are presented on the F-35 we're all making educated guesses at best in regards to its specific performance, but this thread is about comparing these two aircraft, thus we have to go by what we have and thankfully information on the F-16 is readily accessible.

 

Also wether or not an aircraft benefits from a strong vortex effect can actually be eyeballed in certain situations.

[Bucic]

In regards to fuselage lift the F-16 enjoys an advantage over the F-35 here quite simply due to its more aerodynamically optimized shape, mostly in the form of an airfoil (...)

Aby drawings to back this claim (airfoil)?

[Hummingbird]

Aby drawings to back this claim (airfoil)?

 

How about actual real life pictures?:

[Hummingbird]

And some from underneath & behind (fuselage airfoil shape is esp. noticable on last picture):

[Bucic]

Ah. I thought you meant something different. Disregard.

[Hummingbird]

Oh np, glad that cleared it up :)

 

A couple more for the collection, cause you can never have enough pictures of this beauty :D

 

[Bullfrog_]

your tone comes across as a bit condescending and rude.

 

It does, and if your going to ask for something... it's better to avoid it.

[tflash]

How about actual real life pictures?:

 

Ah, these are the better arguments! Keep them coming, Hummingbird!

[tflash]

F-16AM MLU isn't it? I guess F-16C Bock 30 and F-16A MLU are the real dogfighters, the Block 40-50 being more heavy? I can imagine the F-35 matches the latter when loaded, but would have difficulties against a clean Block 30 or MLU.

[Basher54321]

F-16AM MLU isn't it? I guess F-16C Bock 30 and F-16A MLU are the real dogfighters, the Block 40-50 being more heavy? I can imagine the F-35 matches the latter when loaded, but would have difficulties against a clean Block 30 or MLU.

 

No idea - in a 1v1 BFM exercise you might see this - did hint at a Navy Aggressor pilot recently converting to the F-16A B15 about getting some HUD footage when hes up against F-35s ha :)