F-35 vs F-16

[Basher54321]

The F-35 may or may not have the advantage aerodynamically over the F-16 and other 4th generation aircraft but is the incremental difference in performance justifying the cost of the program?

 

what sources and cost calculations have you looked at?

 

He does make some compelling points beyond the intrinsic quality of the plane itself.

 

Please list them.

 

 

I am not sure it makes it a reliable tool to fight with. You just have to look at today's car...

Even if it's technically solvable, it is at such cost that you basically have to gut other parts of your military to keep it relevant.

 

In that sense, less is more. You will find this in every field of expertise and war is all about expertise.

 

Not if more gives you the large tactical advantage you were aiming for.

Who says it wont be reliable - most jets flying these days depend on solid state tech and software. The F-16 and F-117 have depended on it just to fly for over 30 years.

[mvsgas]

Hummingbird

IIRC, a couple of day ago you mention wing loading and you compared the F-16C to the F-35A.

Now, I do not know how to get the wing loading since I have no idea ho much body lift both aircraft have. But to be accurate on both aircraft, wouldm't we have to compare them with similar configurations?

 

What I mean is in order for the F-16C to have similar capabilities to the F-35A we would have to add the weight to the F-16C of the HTS pod, Sniper Pod, two external wing tanks (370g or 600g and conformal tanks) 2 bombs, and 2 AIM-120 and then compared to the F-35A carrying same fuel load and same weapons. We would have to also specify which block (block 42 has a different weight than block 40, even on the same country) and we need to specify what country F-16 ( i.e. Block 52 from ROK have different weight than USAF block 52 AFAIK, different internal equipment).

[Exorcet]

What do you mean?

I guess I never answered this.

 

The F-35's performance as is fighter appears to be about even to 4th gen aircraft. It's not specifically meant to supercruise and the focus on agility wasn't as high as with the F-22, EF-2000, etc. It will be a deadly fighter today, I expect fighters in the coming decades will outclass it in air to air unless overall performance remains about where it is now.

[GGTharos]

The F-35's performance is based in the fact that it's a strike fighter, not an air to air fighter. It just happens to be ok in that role as well.

[Exorcet]

The F-35's performance is based in the fact that it's a strike fighter, not an air to air fighter. It just happens to be ok in that role as well.

Yes, agreed.

[mvsgas]

I guess I never answered this.

 

The F-35's performance as is fighter appears to be about even to 4th gen aircraft. It's not specifically meant to supercruise and the focus on agility wasn't as high as with the F-22, EF-2000, etc. It will be a deadly fighter today, I expect fighters in the coming decades will outclass it in air to air unless overall performance remains about where it is now.

 

Thanks

[Emu]

Based on Desert Storm, modern air-to-air encounters seem to be dominated by avionics, weapons technology and training rather than manoeuvrability. If manoeuvrability was the over-riding factor, Iraqi MiG-29s would surely have done much better. If you look at other aircraft development, most time and effort seems to be placed on avionics, e.g. the EF2000 is having an AESA developed but no one much cares about TVC, the Rafale also went for an AESA upgrade with little interest in TVC. I could be wrong but I don't think the Chinese are incorporating TVC on the J-20/31 either. Most encounters will be fought BVR and far-WVR pre-pass. They'll also be many vs many, so even in a dogfight, being able to out-manoeuvre another plane still means that you'll be in front of another one. Then you have the whole HOBS/LOAL/HMCS thing.

[Bucic]

Hummingbird

IIRC, a couple of day ago you mention wing loading and you compared the F-16C to the F-35A.

Now, I do not know how to get the wing loading since I have no idea ho much body lift both aircraft have. But to be accurate on both aircraft, wouldm't we have to compare them with similar configurations?

 

What I mean is in order for the F-16C to have similar capabilities to the F-35A we would have to add the weight to the F-16C of the HTS pod, Sniper Pod, two external wing tanks (370g or 600g and conformal tanks) 2 bombs, and 2 AIM-120 and then compared to the F-35A carrying same fuel load and same weapons. We would have to also specify which block (block 42 has a different weight than block 40, even on the same country) and we need to specify what country F-16 ( i.e. Block 52 from ROK have different weight than USAF block 52 AFAIK, different internal equipment).

This!

 

Few more notes from me (in reply to some Hummingbird's points):

- LERX do not translate directly into lift increase. Any comparisons involving comparing LERX area is invalid right from the start.

- The effect of LERX at low AoA that would involve lift increase is strictly dependent on their design. See MiG-29 vs F-16. And it's always a secondary effect!

- To say that F-16 has a 'lift-optimized' fuselage to undermine the same effect of F-35's fuselage is just gibberish.

[Basher54321]

Hummingbird

IIRC, a couple of day ago you mention wing loading and you compared the F-16C to the F-35A.

Now, I do not know how to get the wing loading since I have no idea ho much body lift both aircraft have. But to be accurate on both aircraft, wouldn't we have to compare them with similar configurations?

 

 

Probably referring to wing loading only using the wing ref area and range of operating weights - in this case the F-16C B50 and F-35A do have a similar range.

 

F-16 derives a lot of extra lift from body/vortex /tail lift that the above doesn't account for - however the F-35 also being an unstable lifting tail design uses some similar methods. Adding pylons to either complicates things much further - so a true comparison needs Lock Mart to send some EM charts over.........which I'm sure they will :)

[mvsgas]

So, would it be fair to say non of us got the necessary information to tell which aircraft would be better at what?

[Basher54321]

So, would it be fair to say non of us got the necessary information to tell which aircraft would be better at what?

 

The info is very limited regarding figures and can't be used to tell you much e.g. actual thrust curves, how the inlets affect the thrust , or how much drag there actually is in the variable flight circumstances etc etc. You can make guesses based on whats out there sure.

 

Even if you did a 3D model and put it into a wind tunnel - turn performance can be affected by the programming of flight surfaces such as the LEFs/TEFs for example - how would you know what that is?

 

Considering the known performance reductions you get with other aircraft (& other issues) its fair to say that with an internal loadout A-G only you do get benefits RE drag/fuel consumption/RCS (and a big deal over M1 concerning drag. )

 

Pilot quotes from USAF/USN etc might be better if you want to trust them.

[Hummingbird]

This!

 

Few more notes from me (in reply to some Hummingbird's points):

- LERX do not translate directly into lift increase. Any comparisons involving comparing LERX area is invalid right from the start.

- The effect of LERX at low AoA that would involve lift increase is strictly dependent on their design. See MiG-29 vs F-16. And it's always a secondary effect!

- To say that F-16 has a 'lift-optimized' fuselage to undermine the same effect of F-35's fuselage is just gibberish.

 

 

We're not just talking about LERX area, which adds more lifting surface, but more crucially we're talking about its' effects over the main wing area, and the effects on the F-16 (& F-18) are very pronounced as they enjoy a large increase in lift due to the strong vortex that their LERX provides over the main wing. You need to look no further for evidence than the heavy vapor trails noticable over the wings on either aircraft as they pull tight turns:

 

 

Some details on the F-18C's LERX:

 

The F-35 does not enjoy this to the same effect, so calling it gibberish is just, well gibberish..

Edited May 11, 2015 by Hummingbird

[Bucic]

We're not just talking about LERX area, which adds more lifting surface, but more crucially we're talking about its' effects over the main wing area, and the effects on the F-16 (& F-18) are very pronounced as they enjoy a large increase in lift due to the strong vortex that their LERX provides over the main wing. You need to look no further for evidence than the heavy vapor trails noticable over the wings on either aircraft as they pull tight turns:

 

http://www.heraldo.es/galerias-imagenes/wp-content/uploads/2015/01/f-16.jpg[/im g]

 

Some details on the F-18C's LERX:

http://i.imgur.com/pyjNv.jpg[/img ]

 

The F-35 does not enjoy this to the same effect, so calling it gibberish is just, well gibberish..

I'm not denying the importance of LERX in high-performance fighters. I'm arguing the way you use LERX in your statements.

 

Still waiting for the specifics on A/C configurations you claim are worth comparing. Without this the whole discussion is futile.

[Emu]

If you look at the intakes, they have a LERX, and integrally, they form part of the LERX for the wing I believe.

 

[Basher54321]

The sides of the intakes have supposedly been shaped to induce vortex e.g.

 

 

Don't make assumptions on that though because the amount of visible vortex generated depends on a few things.

[Bullfrog_]

The F-35 has Chines instead of LERX.

[tflash]

I really wonder on what data your claims are based Hummingbird. The idea that the F-35 would have no lifting body characteristics is strange, as much as not taking into account that the F-35 engineers not only had access to all necessary knowledge available for F-16 but could make use of tremendously higher computing power to calculate the lift.

 

This allows for a very complex shape, not only optimized for stealth, but also for aerodynamics in a very broad flight regime span.

 

Edited May 11, 2015 by tflash

[Exorcet]

I really wonder on what data your claims are based Hummingbird. The idea that the F-35 would have no lifting body characteristics is strange, as much as not taking into account that the F-35 engineers not only had access to all necessary knowledge available for F-16 but could make use of tremendously higher computing power to calculate the lift.

 

This allows for a very complex shape, not only optimized for stealth, but also for aerodynamics in a very broad flight regime span.

 

The claim more specifically is the F-35 body has a lower CL (CLA?) than the F-16's. Flatter, sharper surfaces are better for producing stagnation and vortices respectively, but I'd hesitate to estimate actual values just by looking.

 

The F-35 might lose out if there is a lot of flow rolling up along the sides from underneath because that flow will be at low pressure and also be on a surface that faces downward (though only at a small angle). On the F-16, the vortices rolling off the large LERX's flow to the top of the plane where they contribute to lift.

 

I can see a logical basis for the argument being made, I'm just not convinced of it. I can't say what is correct without a good CAD model of either plane or some hard data.

[ФрогФут]

We're not just talking about LERX area, which adds more lifting surface, but more crucially we're talking about its' effects over the main wing area, and the effects on the F-16 (& F-18) are very pronounced as they enjoy a large increase in lift due to the strong vortex that their LERX provides over the main wing. You need to look no further for evidence than the heavy vapor trails noticable over the wings on either aircraft as they pull tight turns:

 

 

Some details on the F-18C's LERX:

 

 

The F-35 does not enjoy this to the same effect, so calling it gibberish is just, well gibberish..

The proportion of wing/LERX produced lift is very dependent on AoA and Mach number. So it is pretty useless to roughly count wing load. Only thing, that will really tell about the plane is Cy (lift coefficient)/Cx(drag coefficient) vs AoA and Mach.

[tflash]

Yes, but also take unto account the flatter, inward bulged, wide belly of the F-35. The F-16 has a round belly, not very optimal to generate lift. That is why it badly needs the Lerx imho, since its wings are not that big either. With current computers they can much better calculate the forces and flows that occurs in a multitude of flight attitudes then what they could in the 60ties, I guess. I'm not so sure, eg, that the Lerx is that effective when the aircraft is in a sideslip.

[Exorcet]

Yes, I point to the F-16 intake as a glaring weakness when it comes to lifting body design. It would not surprise me if it was on the lower end of lifting ability, but again it's extremely difficult to say anything definite just from looking.

 

CFD and computing capability has indeed grown hugely from the 60's, although even back then there were wind tunnels, scale model testing, etc. In some cases you could see a flow pattern just as well as you could today on a computer, but wind tunnel iterations are slow because you need to build physical models. Your observations may also be limited to areas that are easy to observe.

[Basher54321]

Yes, I point to the F-16 intake as a glaring weakness when it comes to lifting body design. It would not surprise me if it was on the lower end of lifting ability, but again it's extremely difficult to say anything definite just from looking.

 

 

 

The generated lift is relative to how much weight/drag there is - so yes almost impossible to guess from looking at a frame.

 

 

May I be allowed to bring this topic back for a comment? I was deeply involved in the development and flight testing of the F-16 for many years, so have first hand knowledge of this topic for that airplane. You may be surprised to know that the lift provided by the F-16 fuselage is a very significant portion of the total lift. Every flight condition is different, but at one critical condition, 0.95M 10,000 ft, the fuselage provides 45% of the total lift at 9g. The percentage is even higher at some other conditions. Considering the F-35 wide flat-bottom fuselage, I would guess it provides at least as much lift, probably more.

 

Fuselage lift is extremely important in reducing the weight of an airplane. If the wing had to provide all the lift, its weight would be much greater. Similarly, the fuselage weight would be much greater if it did not have lift to help support it. The structural weight could easily double without fuselage lift.

 

http://www.f-16.net/forum/viewtopic.php?t=7491

[Hummingbird]

There's no doubt that the F-35's wide body will produce lift, and no small amount either. But by the nature of its boxy design it will do it less efficiently than what we traditionally refer to as a lifting body design. This is true for the same reason that a matchbox won't be as aerodynamically efficient as a flat airfoil shaped piece of material with the same weight & bottom surface area. The latter will produce more lift than the other, and more efficiently as well.

Edited May 12, 2015 by Hummingbird

[Exorcet]

The F-35 fuselage may be boxy, but it's not a box. A matchbox fails to produce lift because the upper corner produces an extreme pressure gradient resulting in separation. The F-35 has no such issue because air can simply pass through the front face of the "box" (the inlets). Also, if the matchbox had wings, those would provide a favorable pressure gradient behind the sharp corner and reduce the likelihood of flow separation while also accelerating air to reduce pressure and increase lift.

[Hummingbird]

The F-35 fuselage may be boxy, but it's not a box. A matchbox fails to produce lift because the upper corner produces an extreme pressure gradient resulting in separation. The F-35 has no such issue because air can simply pass through the front face of the "box" (the inlets). Also, if the matchbox had wings, those would provide a favorable pressure gradient behind the sharp corner and reduce the likelihood of flow separation while also accelerating air to reduce pressure and increase lift.

 

Of course it was an exaggerated comparison in order to promote a better understanding for others.

 

The F-35's main problem is the fact that the intakes are in between the wings and the fuselage and not below. 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.