F-35B Grounded

[marcos]

No, actually the only names I pay attention to in this forum are the trolls. That's you, not Exorcet. I'm afraid you're compensating.

You probably have the same IP address as Exorcet, because whenever he trolls, you're always there too.

 

I post 'maximum range' figures with supporting evidence, I then get told that those range figures could be pessimistic/optimistic/different without any supporting evidence. You see the problem with that? During the Cold War, such wings were referred to as 'defector proof' for a reason.

[Cali]

Cali, I'm sure in can 'glide' too, just not very far. During the Cold War, such wings were referred to as 'defector proof'.

 

That's the thing, do you know what the glide ratio is for it?

[marcos]

That's the thing, do you know what the glide ratio is for it?

Nope but I do know that it's range per lb of fuel isn't great even when the engine is working relative to any number of 4th and 4.5th gen aircraft including, as examples, the Typhoon and Rafale, and I've shown this with published figures. The difference between the F-35C and the F-35A wrt range also shows the importance of wing area/loading*. The F-35A and B have very poor wing loading figures and the C's is mediocre. So I feel I have enough information to make a valid inference on its gliding capabilities.

 

*If you look at the F-35C, it has a 15% longer range than the F-35A despite weighing almost 20% more and having <8% more fuel load.

 

You posted it, as I said in my last post.

I posted it with supporting evidence. You then disagreed with nothing but conjecture.

 

So what altitude is the F-35 flying at?

The altitude that makes the figure look best for export I'd imagine.

 

 

And if we take the F-16 and F-35 and give them similar fuel fractions

 

F-35: ~11000 lbs fuel

F-16: ~9000 lbs fuel

 

1000 lbs weapons

 

F-16 TWR = ~1

F-35 TWR = ~1.03

The problem is that I used to run by that same argument in the past too, however it falls down because the F-35 simply doesn't go as far with 1000lb of fuel as an F-15/16/18/22/Rafale/Typhoon. A case shown by the fact that a Typhoon has a better range with 11,000lbs of fuel than an F-35A with 18,000lbs of fuel. Those are the figures we have at the moment. If they can be shown to be wrong with supporting evidence, then fine, but please don't come back with nothing more than conjecture and hypothesis.

 

The wing loading is irrelevant already for the most part. What matters is acceleration and turning performance, but that's harder to find or figure out. WL and TWR can be used to approximate performance, but they aren't very good. You can't get acceleration without force and those two ignore drag, so when you plug into F=ma you're basically making wild guesses (on top of not knowing the exactly weight of the plane when it's maneuvering or the thrust it's making at speed/altitude).

It doesn't really completely ignore drag though and if you weren't so hopelessly out of your depth you'd realise the strong correlation between wing loading and drag during any manoeuvre.

 

Cd = Cd0(M) + k(M)Cl^2

 

Cl = 2L/(Density*Wing Area*v^2)

 

So the smaller the wings, the higher the required lift coefficient and the greater the drag. Sure wing design has an impact on lift vs drag, but you'd can't seriously expect it to overcome a situation of 100lb/ft^2 vs 60-80lb/ft^2. And that's why I think the currently available figures on range are probably correct.

 

If you look at the F-35C, it has a 15% longer range than the F-35A despite weighing almost 20% more and having <8% more fuel load, because it has bigger wings. Hopefully that should exemplify the affect of wing loading in a way completely unbiased to the F-35.

 

What I can say is that the F-35 planform does not have large sweep, which is generally good for the lift slope. I don't know the airfoil so who knows what the cl is, but we could probably look to other fighters for an idea. But then be left lost as to what the body lift is.

Overly simplistic statement. The Cl changes according to what is required during flight at any time via AoA adjustments. The variables are the Cd0 and k, which will change with wing design as well as Mach number.

 

This, in summary, is mathematically why I'm inclined to believe the figures currently published. Intuitively I also suspect that Lockheed wouldn't sell the F-35 short by understating its range - that's just bad marketing.

 

Going back to the SH, an AR of 4 seems to be partially responsible for it being one of the slowest fighters around.

The other main reason being the high BPR required to achieve the necessary thrust with a single engine formerly based on a design with only 80% of the low speed thrust.

 

 

IN SUMMARY:

 

My statements regarding range are based on hard facts about known wing loading figures and published figures for range, which are both in agreement with each other.

 

Your counter statements are based on hypotheses about unknown wing parameters (that you can't even provide an order of magnitude mathematical argument for) and the fact that you believe Lockheed may have understated the range of a plane they're trying to sell on the global market.

 

Conversation is over.

Edited January 31, 2013 by marcos

[GGTharos]

The requirement for the F-35B is fairly simple: The Marines (and whoever else uses it) want an aircraft they can use from some form of FARP.

 

For this, they give up a bunch of things; they might not want as much range, they might prefer faster turn-around at a FARP.

 

As for stealth being a 'small' advantage, tell that to USAF/USN who are rather worried about actual stealth aircraft and their effect on AMRAAM.

 

As for the IRST > F-22/F-35 deal, it has already been shown/commented/etc by people who actually do the fighting that this isn't the case, but you can do your own research on this. :)

[bengo]

More bad news :

http://www.flightglobal.com/news/articles/reduced-f-35-performance-specifications-may-have-significant-operational-impact-381683/

[GGTharos]

Sounds like sensationalism.

 

The baseline for comparison is a clean F-16, vs. what configuration of F-35? At what altitude?

 

Did the F-35's specs suddenly drop, or is it that they haven't changed, but someone's reading from specs that were put in the contract ages ago, and the F-35 still 'performs like a combination of a Viper and Hornet'?

[Exorcet]

Nope but I do know that it's range per lb of fuel isn't great even when the engine is working relative to any number of 4th and 4.5th gen aircraft including, as examples, the Typhoon and Rafale, and I've shown this with published figures.

You've guessed this based on public figures (another point, what's not public? I'm sure not everything is).

 

I've pointed out multiple times that you've used figures that at least partially represent just about the best a plane could do without doing the same for the F-35.

 

Granted it's probably impossible to make a like comparison because the info just isn't there, however that doesn't mean you can pretend otherwise.

The difference between the F-35C and the F-35A wrt range also shows the importance of wing area/loading*. The F-35A and B have very poor wing loading figures and the C's is mediocre. So I feel I have enough information to make a valid inference on its gliding capabilities.

 

*If you look at the F-35C, it has a 15% longer range than the F-35A despite weighing almost 20% more and having <8% more fuel load.

This is a better use of wing loading since it eliminates many variables that you have to deal with when comparing across different aircraft, but that still means wing loading doesn't say much when comparing different aircraft.

 

You're again making assumptions about range figures, but honestly in this case it's probably not so bad since public figures on the F-35 are probably handled in a similar manner. I think the assumption made here is valid.

 

 

 

I posted it with supporting evidence. You then disagreed with nothing but conjecture.

I'd expect you to read your own sources. I even went to Wiki and pulled up the articles it cited to show you the flaws in your reasoning. So again, if you want the supporting evidence, you have to read it.

 

The altitude that makes the figure look best for export I'd imagine.

Which a plane with no weapons or a plane fully loaded that is flying a profile to take full advantage of stealth as opposed to range?

 

Actually, what nation would ask for only one range, especially for a multirole fighter? Everyone knows it's going to vary depending on what you're carrying and how you're flying.

 

So basically you don't know what the F-35 range figure means, so you can say with certainly how far the plane can fly other than saying it's at least the numbers you've found.

 

 

 

The problem is that I used to run by that same argument in the past too, however it falls down because the F-35 simply doesn't go as far with 1000lb of fuel as an F-15/16/18/22/Rafale/Typhoon.

It's heavier than them (except the 22, which also does not have a well defined range, so that's already knocked out of consideration) so it's expected that it won't go as far on the same amount of fuel. This is why fuel is measured in fuel fraction, and the F-35 beats them all in that area if I recall. At least the F-35A does.

 

A case shown by the fact that a Typhoon has a better range with 11,000lbs of fuel than an F-35A with 18,000lbs of fuel.

For Eurofighter's sake, that EF-2000 would be competitive in terms of range with a F-35 if the EF was flown with 18,000 lbs of fuel.

 

Range goes with ln(m_i/m_f)

 

And again, until you're comparing like situations, range numbers are very vague.

 

Combat radius:

 

• Ground attack, lo-lo-lo: 601 km (325 nmi)
  
• Ground attack, hi-lo-hi: 1,389 km (750 nmi)
  
• Air defence with 3-hr combat air patrol: 185 km (100 nmi)
  
• Air defence with 10-min. loiter: 1,389 km (750 nmi)
  

http://en.wikipedia.org/wiki/EF-2000

 

 

And even those four bullets are vague. No mention of payload, and for the ground attack profiles no mention of duration.

 

 

 

Those are the figures we have at the moment. If they can be shown to be wrong with supporting evidence, then fine, but please don't come back with nothing more than conjecture and hypothesis.

Exactly, we need to go with what we have, and what we have contains a lot of question marks. You can't answer things that have no known answer. This applies to the F-35's range and agility, and in all likelihood the EF-2000 and Rafale as well.

 

On the other hand, while we don't have hard numbers for some of these things, we do have reports from the test program.

 

http://www.defensenews.com/article/20110516/DEFSECT01/105160302/F-35-Tests-Proceed-Revealing-F-18-Like-Performance

 

And it's been said quite a few times how the F-35 is at least on par with current fighters. Even the B model.

 

 

during any manoeuvre.

I see this:

Cd = Cd0(M) + k(M)Cl^2

 

Cl = 2L/(Density*Wing Area*v^2)

Where is CD_w? If we're talking any maneuver, and we're talking fighters, leaving out CD_w is something you can't do. Airliners aren't even supersonic but they can't afford to have wings thick enough to seat passengers because they actually need to get where they are going

 

A. before a week has elasped

 

B. without 15 times their weight in fuel

 

You're missing skin friction too, and ignoring any body lift or drag, as well as lift contributed by the tail if the aircraft is unstable.

 

So the smaller the wings, the higher the required lift coefficient and the greater the drag. Sure wing design has an impact on lift vs drag, but you'd can't seriously expect it to overcome a situation of 100lb/ft^2 vs 60-80lb/ft^2. And that's why I think the currently available figures on range are probably correct.

Only your cl is dictated by your airfoil unless you don't care how fast the plane is going to end up being. This works for M > .3 (well, not really, it never works, but you could do this at low speeds if you were OK with being a terrible engineer), but fighters can barely fly in this regime so there is no point working in subsonic, incompressible flow. Fighters fly at trans/supersonic speed which puts more constraints on airfoil choice.

 

When you have an airfoil that will let you reach your desired cruise speed and not hinder your max speed and acceleration you back out the wing size.

 

Also, even when we're talking about low speed, you'd still be wrong to simply slap the largest wing possible on the plane. You would want a smaller wing. Yes, a smaller wing with a higher cl airfoil (assuming L/D is the same). Why? Aspect Ratio.

 

CD(M> .3) = CD0 + CD_i + CD_f

 

Aspect ratio to infinity takes CD_i, CD_f(actually, no), and weight to 0 *EDIT mistake, you'd take AR to infinity with constant area*

Area to infinity takes CD_f to infinity, and weight to infinity, and structural issues to infinity.

 

But keep in mind that in practice small wings have limitations, such as critical Re and space for fuel. Like most things in engineering it's a balance and you can't really afford to go for one thing over all else.

 

If you look at the F-35C, it has a 15% longer range than the F-35A despite weighing almost 20% more and having <8% more fuel load, because it has bigger wings. Hopefully that should exemplify the affect of wing loading in a way completely unbiased to the F-35.

Again this only applies to F-35 A/B/C comparisons because in this case you can be sure that CD0 is 99.999999999999% identical across planes, thrust is 99.999999999999% identical across planes.

 

You don't have this luxury when comparing F-35's to EF-2000's. Which one turns better?

 

F-35 has 85 lb/ft^2 and 1.07 lbf/lb, or well any number around those

 

EF-2000 has 64 lb/ft^2 and 1.13 lbf/lb, or well, any number around those

 

F=ma

 

a=F/m

 

m = known

 

F = sqrt((T-D)^2 + (L-W)^2)

 

T = unknown

D = unknown

L = unknown, except during cruise when it's = g*m = W (although we don't W if we don't know the exact state of the aircraft)

 

So, no one knows the answer.

 

Overly simplistic statement. The Cl changes according to what is required during flight at any time via AoA adjustments. The variables are the Cd0 and k, which will change with wing design as well as Mach number.

OK, I said lift slope so all of that is addressed. The lift slope is typically constant until stall.

 

 

 

The other main reason being the high BPR required to achieve the necessary thrust with a single engine formerly based on a design with only 80% of the low speed thrust.

I'm not sure what you're referring to here? You mean that the F/A-18 is based on the F-17 that is based on the F-20 which was single engine?

 

Or the F135 vs the F119? The F119 has 90% of the F135's dry thrust. I'm a bit lost here.

 

If the latter, yes the F-35 probably won't have as high an exhaust velocity as some other other fighters, but with high BPR and a big fan you usually get good mileage when it comes to acceleration. And we know the F-35 is good for at least M 1.6, which puts makes it competitive with current fighters when they're carrying weapons.

 

To extend combat range without air refueling, the F-16C UCAV can increase fuel

load using the 2300 pound cockpit fuel tank previously mentioned or 600 gallon wing

fuel tanks. However, F-16 pilots prefer the standard 370-gallon wing fuel tanks because

the 600-gallon wing tanks severely limit aircraft performance.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA367242 pg 37

 

Also on that page is a range vs payload chart.

 

 

IN SUMMARY:

 

My statements regarding range are based on hard facts about known wing loading figures and published figures for range, which are both in agreement with each other.

Your taking things and not understanding them, or ignoring what's wrong with them.

Your counter statements are based on hypotheses about unknown wing parameters (that you can't even provide an order of magnitude mathematical argument for) and the fact that you believe Lockheed may have understated the range of a plane they're trying to sell on the global market.

I'm telling you what's wrong with what you said, and then waiting for you to do the same, though I'll only use facts as facts.

Conversation is over.

You're free to leave without asking. Edited January 31, 2013 by Exorcet

[marcos]

F-35 has 85 lb/ft^2 and 1.07 lbf/lb, or well any number around those

 

EF-2000 has 64 lb/ft^2 and 1.13 lbf/lb, or well, any number around those

 

This perfectly illustrates the futility of this conversation. I'm just constantly correcting outright BS.

 

F-35A: 47,550lb/460ft^2 = 103lb/ft^2

 

F-35B: 45,800lb/460ft^2 = 100lb/ft^2

 

F-35C: 54,550lb/668ft^2 = 82lb/ft^2

[Exorcet]

F-35A: 47,550lb/460ft^2 = 103lb/ft^2

 

F-35B: 45,800lb/460ft^2 = 100lb/ft^2

 

F-35C: 54,550lb/668ft^2 = 82lb/ft^2

T = L = D = ?

 

And you'd be wrong with all of those numbers as soon as the first drop of fuel was sent to the combustor and out the back of the jet.

 

Though maybe you be right again if it hooked up with a KC-135... but then you'd be wrong again after the next planck time.

 

And you might be wrong even when the plane is sitting in it's parking space if it only needs 70% fuel to complete it's mission.

[marcos]

F=ma

 

a=F/m

 

m = known

 

F = sqrt((T-D)^2 + (L-W)^2)

This equation is nonsense. Why you're relating F=ma to a force not in the direction of acceleration I have no idea. If we're talking about a turn.

 

Lsin(theta) = mg

 

Lcos(theta) = mv^2/r

 

tan(theta) = mgr/mv^2

 

L = mg/{arcsin (arctan[mgr/mv^2])}

 

In level cruise:

 

L=mg (approximately)

 

Cl = 2L/(Density*Wing Area*v^2)

 

Therefore large wing area = smaller Cl

 

Cd = Cd0(M) + k(M)(Cl^2)

 

So you're shit out of luck son. It's a squared term and you already lose out on mass too.

 

An F-35A with full internal fuel weighs 40% more than a Typhoon, so L is 40% higher.

 

The Typhoon's wing-loading is 62% that of an F-35A, so that puts the Cl at 2.26 times that of a Typhoon.

 

Therefore Cl^2 is 5.1 times higher.

 

The typical variance in k for a fighter* is about 50% (0.14 to 0.21) at M=0 to M=0.75 so that won't correct it.

 

So let's gauge a ballpark value for Cl:

 

L=(47750/2.2)*10*10 = 2170454N

 

Cl = (2*2170454)/(1.225*42.71*300^2) = 0.922

 

Say k = 0.16 at 300m/s

 

kCl^2 = 0.136

 

Values of Cd0 for fighter aircraft* at 300m/s vary from 0.01 to 0.018, so the term is small in comparison.

 

kCl^2 is the dominant value in the drag equation and with a 50% variance in k you can't counteract a 5.1 deficit in Cl^2 incurred by excessive weight and poor wing area. Even assuming the planes are empty for argument's sake, Cl^2 is still 2.14 times higher for the F-35, which can't be counteracted by k varying between 0.16 and 0.2 at 300m/s. The delta sweep of the Typhoon is also better for wave drag due to the Area Rule.

 

There ends your case regardless of whether you continue typing or not.....:music_whistling:

 

 

*Jet Propulsion p183 ISBN 0 521 596742, Nicholas Cumpsty, Chief Technologist Rolls-Royce, Professor of Aerothermal Technology at University of Cambridge and director of the Whittle Laboratory 1989-1999

 

Edited January 31, 2013 by marcos

[Phantom88]

Head of LM F-35 Program retires

 

http://www.defensenews.com/article/20130131/DEFREG02/301310027?utm_source=twitterfeed&utm_medium=twitter

[Exorcet]

This equation is nonsense. Why you're relating F=ma to a force not in the direction of acceleration I have no idea. If we're talking about a turn.

 

Lsin(theta) = mg

 

Lcos(theta) = mv^2/r

 

tan(theta) = mgr/mv^2

 

L = mg/{arcsin (arctan[mgr/mv^2])}

 

In level cruise:

 

L=mg (approximately)

 

Cl = 2L/(Density*Wing Area*v^2)

 

Therefore large wing area = smaller Cl

 

Cd = Cd0(M) + k(M)(Cl^2)

 

So you're shit out of luck son. It's a squared term and you already lose out on mass too.

 

An F-35A with full internal fuel weighs 40% more than a Typhoon, so L is 40% higher.

 

The Typhoon's wing-loading is 62% that of an F-35A, so that puts the Cl at 2.26 times that of a Typhoon.

 

Therefore Cl^2 is 5.1 times higher.

 

The typical variance in k for a fighter is about 50% (0.14 to 0.21) so that won't correct it.

 

So let's gauge a ballpark value for Cl:

 

47

 

True, my mistake not accounting for gravity properly. As for T and D, they very much matter in a turn (though I was not focusing solely on turns) because they'll determine whether you can sustain it or not. I suppose a 6 g turn is a 6 g turn, but if the result of the turn is ending up at 5 knots it's not useful.

 

Your CD term still don't have wave drag though, so it's not exactly helpful. Both drag and lift completely ignore the fuselage as well. And your arbitrary use of full fuel doesn't do much for accuracy either, even if it simplifies the comparison.

 

So you still don't know how these planes are going to perform.

[marcos]

I'll let you off with that since I hadn't finished my post. Now please re-read the rest.

[Exorcet]

Not much has changed. You're still arbitrarily using 100% fuel wieight, which is about the least realistic number you could use besides 0. You're right about the delta planform being generally better for wave drag, but you completely ignored the airfoil which plays a significant role in L/D and the fuselage, again (but I'll give you that the EF-2000 looks better there, when it's not carrying weapons).

 

Cd_i is also only dominant in the drag equation because wave drag isn't there. It is dependent on aspect ratio which is where the F-35 has an advantage over the EF. The EF's wing area and sweep will also hurt it when it comes to skin friction drag and lift slope. Lift slope is important because the AoA will not only impact the wings, but the body (and everything else outside of the aircraft, like weapons). However, the list slope penalty given to the EF by it's sharp sweep would be reduced if it was in a configuration where it had enough of a wing loading advantage over the F-35.

 

By the way if you posted the message when you were half done to get around the login time out on the forum, why not give a heads up in post?

[Weta43]

Just to save anyone that missed it missing the link ...

 

Reduced F-35 performance specifications may have significant operational impact

 

The Pentagon's decision to reduce the performance specifications for the Lockheed Martin F-35 Joint Strike Fighter will have a significant operational impact, a number of highly experienced fighter pilots consulted by Flightglobal concur. But the careful development of tactics and disciplined employment of the jet may be able to mitigate some of those shortcomings.

 

"This is going to have a big tactical impact," one highly experienced officer says. "Anytime you have to lower performance standards, the capability of what the airframe can do goes down as well."

 

The US Department of Defense's decision to relax the sustained turn performance of all three variants of the F-35 was revealed earlier this month in the Pentagon's Director of Operational Test and Evaluation 2012 report. Turn performance for the US Air Force's F-35A was reduced from 5.3 sustained g's to 4.6 sustained g's. The F-35B had its sustained g's cut from five to 4.5 g's, while the US Navy variant had its turn performance truncated from 5.1 to five sustained g's. Acceleration times from Mach 0.8 to Mach 1.2 were extended by eight seconds, 16 seconds and 43 seconds for the A, B and C-models respectively. The baseline standard used for the comparison was a clean Lockheed F-16 Block 50 with two wingtip Raytheon AIM-120 AMRAAMs. "What an embarrassment, and there will be obvious tactical implications. Having a maximum sustained turn performance of less than 5g is the equivalent of an [McDonnell Douglas] F-4 or an [Northrop] F-5," another highly experienced fighter pilot says. "[it's] certainly not anywhere near the performance of most fourth and fifth-generation aircraft."

 

At higher altitudes, the reduced performance will directly impact survivability against advanced Russian-designed "double-digit" surface-to-air missile (SAM) systems such as the Almaz-Antey S-300PMU2 (also called the SA-20 Gargoyle by the North Atlantic Treaty Organization), the pilot says. At lower altitudes, where fighters might operate in for the close air support or forward air control role, the reduced airframe performance will place pilots at increased risk against shorter-range SAMs and anti-aircraft artillery.

 

Most egregious is the F-35C-model's drastically reduced transonic acceleration capabilities. "That [43 seconds] is a massive amount of time, and assuming you are in afterburner for acceleration, it's going to cost you even more gas," the pilot says. "This will directly impact tactical execution, and not in a good way."

 

Pilots typically make the decision to trade a very high rate of fuel consumption for supersonic airspeeds for one of two reasons. "They are either getting ready to kill something or they are trying to defend against something [that's trying to kill] them," the pilot says. "Every second counts in both of those scenarios. The longer it takes, the more compressed the battle space gets. That is not a good thing."

 

While there is no disputing that the reduced performance specifications are a negative development, there may be ways to make up for some of the F-35's less than stellar kinematic performance.

 

Pilots will have to make extensive use of the F-35's stealth characteristics and sensors to compensate for performance areas where the jet has weaknesses, sources familiar with the aircraft say. But engagement zones and maneuvering ranges will most likely be driven even further out against the most dangerous surface-to-air threats.

 

In an air-to-air engagement, for example, tactics would have to be developed to emphasize stealth and beyond visual range (BVR) combat. If a visual range engagement is unavoidable, every effort would have to be taken to enter the "merge" from a position of advantage, which should be possible, given the F-35's stealth characteristics.

 

Once engaged within visual range, given the F-35's limitations and relative strengths, turning should be minimized in favor of using the jet's Northrop Grumman AAQ-37 distributed aperture system of infrared cameras, helmet-mounted display and high off-boresight missiles to engage the enemy aircraft. If a turning fight is unavoidable, the F-35 has good instantaneous turn performance and good high angle of attack (50°AOA limit) performance comparable to a Boeing F/A-18 Hornet, which means a similar strategy could be adopted if one finds him or herself in such a situation.

 

Lockheed, for its part, maintains that the F-35 has performance superior to that of any "legacy" fighter at high altitudes. "Having flown over 4000 hours in fighter jets, I will tell you the F-35's capability at altitude, mostly driven by the internal carriage of those weapons, as a combat airplane, this airplane exceeds the capabilities of just any legacy fighter that I'm familiar with in this kind of regime," says Steve O'Bryan, the company's business development director for the F-35 during a January interview.

 

But much of the discussion is theoretical at this point, the F-35 has not been operationally tested, nor have tactics been developed for the aircraft's usage. How the aircraft will eventually fare once fully developed and fielded is an open question.

http://www.flightglobal.com/news/articles/reduced-f-35-performance-specifications-may-have-significant-operational-impact-381683/

Edited February 1, 2013 by Weta43

[pyromaniac4002]

Well there's an awful lot riding on this 'stealth capability', probably too much. Take away stealth and the F-35 is a bad plane that nobody would want, especially the B variant.

 

When the UK and others signed up to the B variant, they were given the illusion that it would be the same as the other two but VTOL. It turns out to be nowhere near the truth.

 

1) It's STOVL, providing the problem of recovery landings on aborted mission.

 

2) Its range sucks.

 

3) It can't carry any standoff weapons internally. Not the JSOW or JSOW-ER. It can't carry 2000lb bombs internally either. The A and C can do both these. As for JASSMs or Storm Shadows, not even close.

 

4) Dogfight - can't do it.

 

5) Survivability - stealth yes, but only one engine (and blows up in lightning).

 

Funny that the Chinese, for all their alleged blind copying, weren't stupid enough to built a single-engined carrier plane. Credit where credit is due.

 

I don't think the BVR advantage will play out as well as it does in training with 90-100% simulated success rates for AMRAAMs and WVR a Rafale M will f*ck an F-35.

 

As regards interdiction and denied access areas. Even assuming the F-35B has the range to reach them, without external tanks, why bother when I can launch a KEPD 350 from 500km away and not even have to access the airspace. Or even a Tomahawk/MdCN from maybe 2000km away.

 

SEAD? Can the F-35 carry HARMs internally? Nope. Certainly not the B variant.

 

Whilst it has all this supposed stealth image thing going for it. I don't see it being the magic bullet, mostly because the people building it either weren't thinking, or made so many compromises to achieve stealth and STOVL that mission capability was sacrificed in a big way.

 

Stealth - yes. STOVL - yes. Capable fighter - no.

 

You're missing the point of the F-35 program entirely. It's an F-16/AV-8B replacement for the 5th gen world. It's not something that was ever meant to completely dominate in a particular area, much less in every aspect like you seem to berate it for. It's multirole for the era of stealth aircraft. The F-16 is far and away the most flexible and widely-employed (which is itself a significant measure of success) aircraft flown by Western society today and the last few decades, and when you look at the plane itself, it was never an exceptional dogfighter on par with an F-15, nor was it as capable a bombing platform as even an F-111 (assuming it would have been given similar avionics upgrades over the years as the F-16 has). They're aiming for the mark that the F-16 hit, and considering the unequivocal success it had throughout its service life, it's certainly not a bad goal to pursue. The F-35 is absolutely a capable fighter, it's just not particularly exceptional in any one regard.

 

I think you're really excessively discounting the advantages of employing low-observable aircraft. Sure, you can't fit a HARM in the weapons bay. Why the hell would you want to if you could drop a vastly more cost-effective SDB on the same target to achieve the same lethality and even less of the risk? (SEAD with HARMs outside of a SAM's range is great, but if you can see the aircraft coming, you can still do something about it, like perhaps send up a couple of your own fighters.)

 

Anyways, if you want to launch a stand-off weapon, there's certainly no disadvantage incurred by launching it from an F-35 rather than a Rafael M. A standoff weapon is something employed in spite of the abilities of the dropping aircraft; the only benefit you could actually have is how many of them you can fit on the plane and how far that plane can carry them before needing aerial refueling. They're used when the aircraft itself is incapable of effectively attacking the target. Obviously, if you're looking for future expandability, you want a plane that can fulfill more of its missions with less reliance on specialized weaponry instead of something like the Rafael M which will need those munitions to do the same job from day one.

 

Bottom line, stealth technology is clearly going to be part of the future of air combat. It's still very cost-prohibitive and annoying with all the development issues at this point in time, so it might seem much more desirable to ditch a few F-35s in favor of some F/A-18E/Fs or Typhoons which will more than hold their own in today's skies. Ultimately though, the growing pains come with the territory of developing a new generation of combat aircraft. Our long-term defense interests are better served by investing in the F-35 and other projects like it rather than copping out for a few 4.5-gen replacements in the meantime. Obviously, we can't bankrupt ourselves building the F-35, but your pessimism for the development process and downplaying of its abilities (you act as if the stealth aspect was just a cool little party piece) is really doing a disservice to what I'm sure will prove to be a very successful aircraft in due time.

Edited February 1, 2013 by pyromaniac4002

[Cali]

Nope but I do know that it's range per lb of fuel isn't great even when the engine is working relative to any number of 4th and 4.5th gen aircraft including, as examples, the Typhoon and Rafale, and I've shown this with published figures. The difference between the F-35C and the F-35A wrt range also shows the importance of wing area/loading*. The F-35A and B have very poor wing loading figures and the C's is mediocre. So I feel I have enough information to make a valid inference on its gliding capabilities.

 

You can feel that way all you want, but that doesn't mean you are right. There are a lot of calculations that go into being able to glide. You have airspeed, thrust, fuel weight and munitions weight. You would be surprised at some things that happen when they aren't suppose to.

[Exorcet]

what I'm sure will prove to be a very successful aircraft in due time.

 

The F-35 should also be a lesson for the future. Consolidating multiple weapons into one has its benefits, but I think cramming a STOVL fighter into all of this went too far. The F-35B should have been a separate plane. Or maybe had its commonality requirement loosened, I'd prefer the former though so that LM could focus on the A/C versions. AF/Navy aircraft have been done before, and the philosophies of the A and C are probably closer to each other than either is to the B's since the B accepts giving up range, load, and performance in order to fill a niche roll.

 

There's probably also something to learn about managing a project of this size as well. Testing while under going production does not seem to be working, and I'm sure a number of other issues have contributed to the problems the program has faced. I don't think the JSF is a failure yet, but there should be visible improvements in efficiency in any future project of similar scale.

[marcos]

Not much has changed. You're still arbitrarily using 100% fuel wieight, which is about the least realistic number you could use besides 0.

Nope. Read the whole thing carefully. If necessary, feel free to recalculate yourself using whatever fuel load you desire.

 

You're right about the delta planform being generally better for wave drag, but you completely ignored the airfoil which plays a significant role in L/D and the fuselage, again (but I'll give you that the EF-2000 looks better there, when it's not carrying weapons).

And you've completely ignored the fact that at a typical range-extending cruising speed of Mach 0.8 or less, wave drag is insignificant, hence why civil airliner wing profiles are clearly not selected with wave drag reduction in mind.

 

 

The vast majority of the lift is down to the wings:

 

http://www.britannica.com/EBchecked/topic/11014/airplane

 

In flight the airfoil of the wing normally produces the greatest amount of lift, but propellers, tail surfaces, and the fuselage also function as airfoils and generate varying amounts of lift.

 

http://search.yahoo.com/r/_ylt=A0oG7h8lkwtRE0gAV.5XNyoA;_ylu=X3oDMTE0bTNobWo2BHNlYwNzcgRwb3MDMwRjb2xvA2FjMgR2dGlkA0FDQlkwMV85OA--/SIG=14ub57cum/EXP=1359741861/**http%3a//www.southampton.ac.uk/~jps7/Aircraft%2520Design%2520Resources/Brandt%2520Introduction%2520to%2520Aeronautics/Ch4Wing%26Airplane.doc

 

An aircraft fuselage is usually relatively long and slender and therefore does not produce much lift.

 

It's also apparent that the F-35 has a far larger fuselage with a rounded underbelly to accommodate the bomb bays and the extra fuel it burns.:D It's empirically obvious that it won't beat the Typhoon on L/D here either but if you offer evidence to the contrary in the form of mathematical proof, go ahead.

 

Cd_i is also only dominant in the drag equation because wave drag isn't there.

Rubbish. It's dominant because maximum range is attained at subsonic cruising speeds where wave drag isn't a major factor as I've already shown.:megalol:

 

It is dependent on aspect ratio which is where the F-35 has an advantage over the EF.

Care to substantiate that? Because AR = b^2/S and the Typhoon's wingspan is only ~2% more than the F-35A/B's, whereas the area (S) is >20% greater.:megalol:

 

The EF's wing area and sweep will also hurt it when it comes to skin friction drag and lift slope. Lift slope is important because the AoA will not only impact the wings, but the body (and everything else outside of the aircraft, like weapons). However, the list slope penalty given to the EF by it's sharp sweep would be reduced if it was in a configuration where it had enough of a wing loading advantage over the F-35.

Skin friction drag is proportional to area (not a square relationship like lift drag and Cl). Yes the Typhoon has larger wings but they are producing lift. The F-35's huge fuselage is not. In a cruising subsonic plane at optimal cruising speed, lift drag and friction drag are roughly equal. So mathematically, because lift drag is proportional to (mass/wing area)^2 or (wing loading)^2 and friction is only proportional to Area, you lose. Due to the F-35's large fuselage it's debatable whether it in fact has less skin friction without you providing mathematical proof, and even just based on wing area, the 20% difference isn't great enough to overcome the Cl^2 variable, which is greater by a factor of 2.1-5.1.

 

By the way if you posted the message when you were half done to get around the login time out on the forum, why not give a heads up in post?

Couldn't be arsed.

 

Perhaps if you could have the courtesy to post some actual calculated facts in your next post rather than simply mentioning areas of aerodynamics that you demonstrate little to no knowledge of (and sometimes incorrect knowledge of), in a vain attempt to cast doubt on real calculations, widely recognised facts about the value of larger wings for extending range and published range figures which all seem to agree with each other and disagree with you.

Edited February 1, 2013 by marcos

[marcos]

You're missing the point of the F-35 program entirely. It's an F-16/AV-8B replacement for the 5th gen world. It's not something that was ever meant to completely dominate in a particular area, much less in every aspect like you seem to berate it for. It's multirole for the era of stealth aircraft. The F-16 is far and away the most flexible and widely-employed (which is itself a significant measure of success) aircraft flown by Western society today and the last few decades, and when you look at the plane itself, it was never an exceptional dogfighter on par with an F-15, nor was it as capable a bombing platform as even an F-111 (assuming it would have been given similar avionics upgrades over the years as the F-16 has). They're aiming for the mark that the F-16 hit, and considering the unequivocal success it had throughout its service life, it's certainly not a bad goal to pursue. The F-35 is absolutely a capable fighter, it's just not particularly exceptional in any one regard.

I appreciate that stealth is an advantage. The avionics are also reputed to be good but arguably no better than many 4.5th gen fighters are, or will be when the F-35 enters service.

 

From what I'm seeing and from the links people are posting, it's struggling to get anywhere near the performance of the F-16, and the F-16 with conformal tanks probably has a better range too, whilst still maintaining a better TWR and wing loading figures.

 

http://defense-update.com/products/c/F-16-CFT.htm

 

Additionally, I can take an AV-8B or GR9 and put it on a helicopter carrier or even a destroyer's helipad and take off with ordnance. I can't do that with an F-35B.

 

I think you're really excessively discounting the advantages of employing low-observable aircraft. Sure, you can't fit a HARM in the weapons bay. Why the hell would you want to if you could drop a vastly more cost-effective SDB on the same target to achieve the same lethality and even less of the risk? (SEAD with HARMs outside of a SAM's range is great, but if you can see the aircraft coming, you can still do something about it, like perhaps send up a couple of your own fighters.)

I'm not discounting stealth but I'm also not happy with the apparent F-35 design team philosophy of 'nothing else matters except stealth' either.

 

An SDB is all very well if you know where the mobile SAM is and it doesn't move. An SDB II can probably hit a moving target but in a time critical environment, having a missile that homes in on the actual source of the transmission is beneficial. Presumably that's why they spend $millions developing ARMs. Waiting a day for an SDB to glide down from 100km away only for it to be shot down by a Pantsir-S1 before it reaches the S-400 radar isn't very useful. Aside from the fact that I'm not entirely convinced that such a radar complex couldn't see an F-35 at that range anyway. A modern AGM-88E could be launched from low altitude based on GPS co-ordinates if a secondary source has picked out the target.

 

Anyways, if you want to launch a stand-off weapon, there's certainly no disadvantage incurred by launching it from an F-35 rather than a Rafael M. A standoff weapon is something employed in spite of the abilities of the dropping aircraft; the only benefit you could actually have is how many of them you can fit on the plane and how far that plane can carry them before needing aerial refueling. They're used when the aircraft itself is incapable of effectively attacking the target. Obviously, if you're looking for future expandability, you want a plane that can fulfill more of its missions with less reliance on specialized weaponry instead of something like the Rafael M which will need those munitions to do the same job from day one.

And all published figures and maths suggest that a Rafale M or Typhoon would be able to carry those stand-off weapons further on internal fuel, especially with conformal tanks planned as an update.

 

Regardless of stealth there's always a chance of being spotted by patrolling aircraft and I'm not sure an F-35 could handle that as well as either of the other 2 aircraft. Yes it has stealth for BVR but the other two have the Meteor, which will comfotably outrange an AMRAAM due to having ramjet propulsion and not having to carry oxidiser. WVR it's no contest. Whilst the infamous 'clubbing baby seals' document is known to be a hoax, in a WVR fight that really would be the case. Is there even a 4th gen US fighter that the F-35 could out-manoeuvre WVR?

 

Bottom line, stealth technology is clearly going to be part of the future of air combat. It's still very cost-prohibitive and annoying with all the development issues at this point in time, so it might seem much more desirable to ditch a few F-35s in favor of some F/A-18E/Fs or Typhoons which will more than hold their own in today's skies. Ultimately though, the growing pains come with the territory of developing a new generation of combat aircraft. Our long-term defense interests are better served by investing in the F-35 and other projects like it rather than copping out for a few 4.5-gen replacements in the meantime. Obviously, we can't bankrupt ourselves building the F-35, but your pessimism for the development process and downplaying of its abilities (you act as if the stealth aspect was just a cool little party piece) is really doing a disservice to what I'm sure will prove to be a very successful aircraft in due time.

That's the problem though. 4.5th gen fighters can hold their own in today's skies, in some areas, even better than the F-35, and they're cheaper, and they're here now. By the time the F-35 is ready, most things will likely have moved to 6th gen. Stealthier 6th gen unmanned aircraft will conduct the high risk missions, co-ordinated by 4.5th gen fighters who will then mop up.

 

For many people performance and cost are real tangible factors limiting effectiveness. Stealth is a large question mark. I could find a hundred different stories on radars claiming to be effective against stealth and other technologies such as IRST. Another feature of the stealth protagonist argument is the assumed 100% success rate for MRAAMs and an underestimation of closing speeds in A2A combat. E.g. the idea of an F-22 being able to pick-off 6 aircraft BVR is nonsense. An AMRAAM will not succeed 6 times in a row based on any available statistics but in training, they're not actually fired of course, so they don't have to.

 

I don't poo-poo stealth and think the F-22 is a great aircraft despite its hiccups, but the F-35 seems mediocre in all areas besides stealth and that's being generous. I honestly don't understand the small wings. Why? Just why?

Edited February 1, 2013 by marcos

[marcos]

Just to save anyone that missed it missing the link ...

 

 

http://www.flightglobal.com/news/articles/reduced-f-35-performance-specifications-may-have-significant-operational-impact-381683/

This is all myself and others have been pointing out. Performance is there for a reason. It's still required even in the presence of stealth.

 

Turn performance for the US Air Force's F-35A was reduced from 5.3 sustained g's to 4.6 sustained g's. The F-35B had its sustained g's cut from five to 4.5 g's, while the US Navy variant had its turn performance truncated from 5.1 to five sustained g's.

Could be something to do with a low TWR and small wings. It also doesn't take a genius to figure out that a reduction in sustained turning performance, means a reduction in lift vs drag performance and consequently a likely reduction in range.

 

Most egregious is the F-35C-model's drastically reduced transonic acceleration capabilities. "That [43 seconds] is a massive amount of time, and assuming you are in afterburner for acceleration, it's going to cost you even more gas," the pilot says. "This will directly impact tactical execution, and not in a good way."

 

For the benefit of Exorcet, also notice how the performance specification of the F-35C with the larger wings hasn't been affected as badly.

 

3rd gen manoeuvrability:

 

Having a maximum sustained turn performance of less than 5g is the equivalent of an [McDonnell Douglas] F-4 or an [Northrop] F-5," another highly experienced fighter pilot says. "[it's] certainly not anywhere near the performance of most fourth and fifth-generation aircraft."

Edited February 1, 2013 by marcos

[Exorcet]

And you've completely ignored the fact that at a typical range-extending cruising speed of Mach 0.8 or less, wave drag is insignificant, hence why civil airliner wing profiles are clearly not selected with wave drag reduction in mind.

 

But I'm not limiting this to cruise, and it's easy to get supersonic flow at Mach .8 since flow likes to accelerate around bodies. Airliners like supercritical airfoils for a reason.

 

 

The vast majority of the lift is down to the wings:

In the vast majority of tube + wings planes, yes. The ratio is more even for fighters.

 

 

It's also apparent that the F-35 has a far larger fuselage with a rounded underbelly to accommodate the bomb bays and the extra fuel it burns.:D It's empirically obvious that it won't beat the Typhoon on L/D here either but if you offer evidence to the contrary in the form of mathematical proof, go ahead.

The EF is going to carry some pretty big bumps on its fuselage when it goes into combat. It's not obvious at all which L/D will be superior.

 

 

Rubbish. It's dominant because maximum range is attained at subsonic cruising speeds where wave drag isn't a major factor as I've already shown.

Fighters pend the majority of time in cruise, but the little time they spend out of cruise it pretty important.

 

 

Care to substantiate that? Because AR = b^2/S and the Typhoon's wingspan is only ~2% more than the F-35A/B's, whereas the area (S) is >20% greater.

 

39.75^2/551 = 2.32

 

35^2/460 = 2.66

 

Skin friction drag is proportional to area (not a square relationship like lift drag and Cl).

It's very much a square relationship. Drag is typically proportional to area. CD x A. For an airfoil, CD_F ~ 2*cf. Although cf does not grow with the square of velocity, but decreases, except at the transitional Re.

Yes the Typhoon has larger wings but they are producing lift. The F-35's huge fuselage is not.

You'll have to support that.

 

Due to the F-35's large fuselage it's debatable whether it in fact has less skin friction without you providing mathematical proof

I agree, which I why I did not mention skin friction for the fuselage.

, and even just based on wing area, the 20% difference isn't great enough to overcome the Cl^2 variable, which is greater by a factor of 2.1-5.1.

Which is down to your arbitrary number selection.

 

 

 

 

For the benefit of Exorcet, also notice how the performance specification of the F-35C with the larger wings hasn't been affected as badly.

Notice that the A original had the highest sustained turn rating, and that the C's acceleration was cut drastically, I'm assuming the wings played a role there. But it would be nice if reports like this weren't vague.

 

Or maybe it's safe to assume 4 g occurs at 100 knots at 80,000 feet with 40,000 lbs of weapons, since LM wouldn't want the plane to look bad. This makes the F-35 far superior to any other fighter.

[4c Hajduk Veljko]

You're missing the point of the F-35 program entirely. It's an F-16/AV-8B replacement for the 5th gen world....

New is, not always but most of the time, better then old. And for that reason I do support F-35 program. But for god sake, why 2500 of it? Why do we have to borrow money from China and Saudi Arabia to build 2500 F-35's? I would say, we would be just fine with maybe 500. And then have a slew of much cheaper F-16, F-18 with latest sensors technology.

 

This whole F-35 program, along with some other insane and unnecessary military programs, will make some people enormously rich, while putting the entire country on a brink of bankruptcy. I don't want to work the rest of my life to pay for unnecessary number of F-35's, when the job can be done with F-16. Just check the debt clock, 16.5 trillion and counting ....

[Cali]

I agree with you hajduk, there are lots of things that can be made. The F-35 program is already cost a ton of money.

[marcos]

But I'm not limiting this to cruise, and it's easy to get supersonic flow at Mach .8 since flow likes to accelerate around bodies. Airliners like supercritical airfoils for a reason.

So you're ignoring the graph I posted, like everything else. Airliner wings have some elements designed to reduce wave drag but only where they don't compromise the reduction of lift drag. Look at the wing profile of an airliner, it's clearly not designed primarily for the reduction of wave drag.

 

http://history.nasa.gov/SP-367/f86.htm

 

If you read the Flight Global link, you'd see that the amount of fuel required for the F-35 to even get supersonic is terrible.

 

Which is down to your arbitrary number selection.

No it's down to maths, which you apparently don't understand. I've already asked you to use whatever figures you like in the same equations and see what they come out at but the fact is you don't understand the equations, which is why you're still talking. Your early attempt at producing your own equations for lift and drag was also wrong as I pointed out. This tells me that you're not actually capable of understanding any explanation, hence this is a waste of time.

 

The rest of your post is just unsubstantiated drivel and I will waste no time on it.

 

 

I agree with you hajduk, there are lots of things that can be made. The F-35 program is already cost a ton of money.

Frankly it looks like Lockheed Martin is just raping the government. That's the difference between a prime defence contractor and a small business. Prime defence contractors think it's their god-given right to make a profit regardless of how incompetently they perform on a given project.

Edited February 1, 2013 by marcos