F-35 Multirole Joint Strike Fighter

[Bonza]

I think that the F-35 is over rated to be honest. its weight to thrust ratio is poor, 4th gen jets such as F-18 will have far greater maneuverability than F-35 making its air to air capabilities weak, also its stealth technology could become compromised fairly quickly. in order for these aircraft to be viable for the UK we are going to have to mount weapons on wing mounts, as the internal bays do not carry enough or key weapons that we will need such as sidewinder and storm shadow cruise missiles. once these weapons are mounted on wings you can say bye bye to stealth, they'll show up on radar as much as any other jet.

and we wont have enough of them to not do this.

it may be a 5th gen but if it loses its stealth ability it may as-well be a third gen jet.
(as typhoon, rafeal, gripen, F-18/16/15 all have better manouverability than f-35 and all can be equipped with the same radar/communication/counter-measures and warfare electronics)

this is made even worse by the fact that we have chosen the stvol version which further increases its weight- therefore making its thrust to weight ratio even worse. and it reduces weapon bay capacity- therefore meaning we will have to mount weapons on wings and further diminish its stealth technology.

if it had been upto me i dont think i would have even purchased them as i dont think the technology is advanced enough yet, and if i had i would have converted our carrier to catovar so we could have the better carrier version at least.

As GF said, read the thread. I don't care how many pages it is, and how long it takes you, read the thread before you post. Your points have been gone over more times than I can count and we're all sick of having to repeat them.

 

[ADMk2]

The 2012 DOT&E "test report" has been released. No real show stoppers in it, the most significant "new problem" is a "green glow" from within the cockpit interfering slightly with the Heads-up display in the HMS.

The older "show stoppers" (as alleged by some) specifically the F-35C tail-hook and the jitter, streaming DAS footage and night vision problems with the helmet appear to be well on the way to being resolved.

Buffet and transonic roll-off appear to be on their way to being resolved and the software, although it's still lagging, is slowly getting towards where it needs to be. Just add the extra w:

ww.scribd.com/doc/78435294/DoD-DOT-E-10-Jan-2012-F-35-Annual-Operational-Test-and-Evaluation-Report"]DoD DOT&E, 10-Jan-2012. F-35 Annual Operational Test and Evaluation Report

 

[Haavarla]

Wasn't there something about cracks and unvarrent vibration on the B versions?
And that this continue to be a major issue?

http://timemilitary.files.wordpress.com/2013/01/f-35-jsf-dote-fy12-annual-report.pdf

 

[StobieWan]

Wasn't there something about cracks and unvarrent vibration on the B versions?
And that this continue to be a major issue?

http://timemilitary.files.wordpress.com/2013/01/f-35-jsf-dote-fy12-annual-report.pdf

There's reference to cracks in various parts, some of these were found at 7,000 hour inspection points, others earlier, particularly those relating to gear and fan door components. I didn't see any indicators that it was a major issue when they were discovered and they're all pretty much fixed in later LRIP iterations.

I think that's why they test ?

 

[VerySneaky]

Wasn't there something about cracks and unvarrent vibration on the B versions?
And that this continue to be a major issue?

http://timemilitary.files.wordpress.com/2013/01/f-35-jsf-dote-fy12-annual-report.pdf

The program announced an intention to change performance specifications for the F-35A, reducing turn performance from 5.3 to 4.6 sustained g’s

Forgive my ignorance, I was under the impression that the F-35A was 9.0 g capable? Obviously the distinction here is in the term 'sustained', but what exactly defines a sustained turn and how is the relaxation of this requirement going to affect its maneuverability?

Without wanting to turn this into an X v Y post, does anybody have any idea where I can find sustained g specs for other aircraft so I have a basis for comparison?

 

[SpudmanWP]

The listing of "9g" refers to the Instantaneous Gs, not the Sustained Gs.

This is the first time I have seen the official specs of Sustained Gs in for the F-35.

 

[ADMk2]

Forgive my ignorance, I was under the impression that the F-35A was 9.0 g capable? Obviously the distinction here is in the term 'sustained', but what exactly defines a sustained turn and how is the relaxation of this requirement going to affect its maneuverability?

Without wanting to turn this into an X v Y post, does anybody have any idea where I can find sustained g specs for other aircraft so I have a basis for comparison?

You can't compare them seriously even if you wanted to. Sustained turn rates depend on a huge range of variables including aircraft weight (including stores, fuel etc) altitude, installed thrust, wing and fuselage area, (for drag) angle of attack and so on.

Sustained is exactly that. How many G's can your aircraft continue to pull through continued turning. Instantaneous refers to the rapid onset of G's when the turn begins. No aircraft can maintain 9G's throughout a turn, an attempt to do so would "over G" any aircraft that has wings.

For overall manueverability, F-35 will be reasonable, especially compared to other loaded up aircraft in similar state (ie: similar stores, fuel, sensors etc). The advantage the F-35 has over most other aircraft, is all that stuff is carried internally, for lower drag.

The problem with just looking at this figure:

The program announced an intention to change performance specifications for the F-35A, reducing turn performance from 5.3 to 4.6 sustained g’s

Is that we don't know the conditions of such. Is the F-35 carrying 50% fuel, 100% fuel or some other figure? What altitude? What airspeed? What stores is it carrying and so on. It's extremely easy to take these figures out of context and portray them as "bad". That doesn't necessarily make it so, however.

Edit:

Those figures seem to be subsonic (M0.8) at low altitude (15K feet) with the "standard" JSF warload of 2x 2000lbs JDAM and 2x AMRAAM missiles, unknown fuel state.

High altitude, supersonic sustained turn rates are higher according to the intended KPP's, as might be expected.

 

[colay]

As I see it, the effectiveness of the F-35 arises combination of it's various attributes and capabilities. Foremost among these would be it's stealthiness and enhanced SA picture generated from onboard sensors suite and external data links. While it may fall a bit short on a couple of kinematic objectives, the jet's HOB missiles launched from a tactically advantageous position should provide all the kinematic performance needed to get the job done. The program roadmap also foresees improvements in engine thrust in the 5-10% range and 25% in fuel efficiency so that is something to look forward to I suppose.

 

[ADMk2]

As I see it, the effectiveness of the F-35 arises combination of it's various attributes and capabilities. Foremost among these would be it's stealthiness and enhanced SA picture generated from onboard sensors suite and external data links. While it may fall a bit short on a couple of kinematic objectives, the jet's HOB missiles launched from a tactically advantageous position should provide all the kinematic performance needed to get the job done. The program roadmap also foresees improvements in engine thrust in the 5-10% range and 25% in fuel efficiency so that is something to look forward to I suppose.

Yep. If performance is a big issue, the thrust could be ramped up significantly with this engine. It's been tested in excess of 50,000lbs on full reheat already. Of course doing such will factor in other issues such as increased fuel burn, engine wear, cost and so on.

It is interesting to note that the overwhelming majority of fighter aircraft users of "low performing" aircraft, invariably invest their dollars in combat system, EW and weapons upgrades, rather than more "poke"...

 

[Haavarla]

Double post

 

[Haavarla]

There's reference to cracks in various parts, some of these were found at 7,000 hour inspection points, others earlier, particularly those relating to gear and fan door components. I didn't see any indicators that it was a major issue when they were discovered and they're all pretty much fixed in later LRIP iterations.

I think that's why they test ?

Well yes, i've read about those ealier cracks around the fan door.
But these seems to be at a much later stage:

“Managing weight growth with such small margins will continue to be a significant program challenge,” it said.
Gilmore’s report also disclosed that durability testing on the Marine version, the F-35B, was halted last month after “multiple” cracks were discovered.
Rein said “we have implemented the fixes” and “expect to resume static testing shortly, as early as” later this week.

Lockheed

What does such fixes imply, increased weight by further strenghtening the airframe?

 

[ADMk2]

Well yes, i've read about those ealier cracks around the fan door.
But these seems to be at a much later stage:

“Managing weight growth with such small margins will continue to be a significant program challenge,” it said.
Gilmore’s report also disclosed that durability testing on the Marine version, the F-35B, was halted last month after “multiple” cracks were discovered.
Rein said “we have implemented the fixes” and “expect to resume static testing shortly, as early as” later this week.

Lockheed

What does such fixes imply, increased weight by further strenghtening the airframe?

It does, which is why there is margin(slim though it may be) for growth in the design. We've already seen a thrust increase for the F-35B, again if they need it, they'll find more. They will also continue to watch the overall weight and continue to look for areas in which they can save weight.

There's no doubt weight continues to be a challenge. I guess this is the price you pay when you design a supersonic, low observable, STOVL fighter aircraft with a certain budget and to meet a spot factor on existing ships you won't change, in order to meet the first ever requirement for such...

 

[south]

Sustained is exactly that. How many G's can your aircraft continue to pull through continued turning. Instantaneous refers to the rapid onset of G's when the turn begins. No aircraft can maintain 9G's throughout a turn, an attempt to do so would "over G" any aircraft that has wings.

For overall manueverability, F-35 will be reasonable, especially compared to other loaded up aircraft in similar state (ie: similar stores, fuel, sensors etc). The advantage the F-35 has over most other aircraft, is all that stuff is carried internally, for lower drag.

The problem with just looking at this figure:

Is that we don't know the conditions of such. Is the F-35 carrying 50% fuel, 100% fuel or some other figure? What altitude? What airspeed? What stores is it carrying and so on. It's extremely easy to take these figures out of context and portray them as "bad". That doesn't necessarily make it so, however.

Edit:

Those figures seem to be subsonic (M0.8) at low altitude (15K feet) with the "standard" JSF warload of 2x 2000lbs JDAM and 2x AMRAAM missiles, unknown fuel state.

High altitude, supersonic sustained turn rates are higher according to the intended KPP's, as might be expected.

Sustained turn rate -> Turn rate you can sustain: i.e. without bleeding airspeed or losing altitude...

Max Instantaneous-> what is the most you can get.... (Not always the G limit) e.g if you are at 200 kts a fast jet won't get 9g because it cannot generate enough lift to do so.

AD - as you said sustained turn rate depends on a number of factors. There are however plenty of jets that can sustain their max G, and this generally happens at a higher speed and lower altitude, hence higher dynamic pressure,more thrust available, means that you can generate the lift required at a lower angle of attack so less drag. G limiters in FCS obviously providing the overstress protection in jets that are so equipped....

With the JSF program announcement that sustained G is being reduced I would hazard a guess that it would be at the same KPP parameters of 15kft, M0.8, 50% fuel.

Not sure where you are getting that high altitude sustained turn rates are higher. If you are talking about the bottom row on the table (G at manouvre weight) I read it that those G numbers shown in the KPP are for an instantaneous turn.

 

[VerySneaky]

Sustained turn rate -> Turn rate without bleeding airspeed or losing altitude... I.e. you can sustain it without anything changing.

Max Instantaneous-> turn rate whilst losing airspeed.

AD - as you said sustained turn rate depends on a number of factors. There are however plenty of jets that can sustain their max G, and this generally happens at a higher speed and lower altitude, hence higher dynamic pressure,more thrust available, means that you can generate the lift required at a lower angle of attack so less drag. G limiters in FCS obviously providing the overstress protection in jets that are so equipped....

With the JSF program announcement that sustained G is being reduced I would hazard a guess that it would be at the same KPP parameters of 15kft, M0.8, 50% fuel.

Not sure where you are getting that high altitude sustained turn rates are higher. If you are talking about the bottom row on the table (G at manouvre weight) I read it that those G numbers shown in the KPP are for an instantaneous turn.

Thanks ADMk and south. Would I be correct in assuming from these statements that while the instantaneous g limit is not a useless stat, it is less operationally relevant and that a good sustained turn is more advantageous in a dogfight scenario?

Obviously there are other factors to consider, but with all other things being equal, how does the revised sustained g limit of the F35A compare to other aircraft? ADMk you said "reasonable", would this be what, middle of the range? Please note that my curiosity is not directed at determining the winner of a dogfight, merely to aid my understanding of what the figures mean operationally.

 

[colay]

9
Obviously there are other factors to consider, but with all other things being equal, how does the revised sustained g limit of the F35A compare to other aircraft? ADMk you said "reasonable", would this be what, middle of the range? Please note that my curiosity is not directed at determining the winner of a dogfight, merely to aid my understanding of what the figures mean operationally.

Operationally, a F-35 loaded with internal ordnance will compare favorably vs. a F-16 or F-18 that is combat-configured with external munitions, sensor pods and EFTs hanging under the wings. The latter will experience a much higher drag penalty and a much larger RCS.

http://www.defensenews.com/print/article/20120118/DEFREG02/301180013/F-35-May-Miss-Acceleration-Goal[/url]



F-35 May Miss Acceleration Goal

By DAVE MAJUMDAR

The F-35 Lightning II’s transonic acceleration may not meet the requirements originally set forth for the program, a top Lockheed Martin official said.

“Based on the original spec, all three of the airplanes are challenged by that spec,” said Tom Burbage, Lockheed’s program manager for the F-35. “The cross-sectional area of the airplane with the internal weapons bays is quite a bit bigger than the airplanes we’re replacing.”

The sharp rise in wave drag at speeds between Mach 0.8 and Mach 1.2 is one of the most challenging areas for engineers to conquer. And the F-35’s relatively large cross-sectional area means, that as a simple matter of physics, the jet can’t quite match its predecessors.

“We’re dealing with the laws of physics. You have an airplane that’s a certain size, you have a wing that’s a certain size, you have an engine that’s a certain size, and that basically determines your acceleration characteristics,” Burbage said. “I think the biggest question is: are the acceleration characteristics of the airplane operationally suitable?”

A recent report by the Defense Department’s top tester, J. Michael Gilmore, says that the Navy’s F-35C model aircraft, which has larger wing and tail surfaces, is not meeting requirements for acceleration.

The report doesn’t say whether the F-35A and F-35B have hit similar snags.

Richard Aboulafia, an analyst with the Teal Group, Fairfax, Va., said that the revelation was not particularly surprising.

“It’s a strike fighter,” Aboulafia said. “It’s not an interceptor; it’s not an F-22.”

Aboulafia said it was unclear whether additional engine power could boost acceleration in the difficult transonic regime. So far, doubts about the aircraft’s aerodynamic performance haven’t diminished Lockheed’s sales prospects, he said.

The F-35 transonic acceleration specifications were written based on clean-configuration F-16 Fighting Falcon and F/A-18 Hornet fighter, Burbage said.

But unlike the Hornet or the F-16, the F-35 has the same configuration unloaded as it does loaded with weapons and fuel, Burbage said. When an F/A-18 or F-16 is encumbered with weapons, pylons and fuel tanks, those jets are robbed of much of their performance.

“What is different is that this airplane has accelerational characteristics with a combat load that no other airplane has, because we carry a combat load internally,” Burbage said, the F-22 Raptor notwithstanding.

Even fully loaded, the F-35’s performance doesn’t change from its unencumbered configuration, he said.

In the high subsonic range between Mach 0.6 to Mach 0.9 where the majority of air combat occurs, the F-35’s acceleration is better than almost anything flying.

Thus far, Lockheed has not had issues with the plane’s acceleration, Burbage said. There are top level Key Performance Parameters from which lower level detailed engineering specification are derived and Lockheed’s job is to meet as many of those specifications as possible within the laws of physics, he said. Discussions are underway about if those original specifications are relevant given the jet’s acceleration in a combat configuration, Burbage added.

Air Force Lt. Col. Eric Smith, director of operations at the 58th Fighter Squadron at Eglin Air Force Base, Fla., and F-35 test pilot, said that flying the aircraft is a thrilling experience.

“I can’t even explain the adrenaline rush you get when you light the afterburner on that thing,” Smith said. “The acceleration is much better than an F-16.”

But the F-35’s aerodynamic performance is not what makes the jet special, Smith said. The F-35 powerful sensors and data-links and how that information is fused into a single coherent and easy to use display are what will make the jet an effective warplane.

Burbage added that while the F-35 is designed as a supersonic fighter, it’s not optimized for the extremely high supersonic speeds that thejr was designed to operate at.

“This is not a supercruising airplane like the F-22,” Burbage said.

 

[ADMk2]

Thanks ADMk and south. Would I be correct in assuming from these statements that while the instantaneous g limit is not a useless stat, it is less operationally relevant and that a good sustained turn is more advantageous in a dogfight scenario?

Obviously there are other factors to consider, but with all other things being equal, how does the revised sustained g limit of the F35A compare to other aircraft? ADMk you said "reasonable", would this be what, middle of the range? Please note that my curiosity is not directed at determining the winner of a dogfight, merely to aid my understanding of what the figures mean operationally.

Unfortunately neither of these terms are particularly helpful by themselves for dogfight comparison purposes. The reason is because fighters don't only turn in level flight. They accelerate, decelerate, climb, dive, turn and so on. They enter engagements at different speeds, altitudes, angles of attack etc.

Also fighters have different levels of installed thrust, different weights and different drag and lift levels. To measure a fighter's overall maneuver performance you need to understand it's turn rate, turn radius, load factors, mach number and altitude.

To put this into perspective, in F-16 v F/A-18 fights the difference usually comes down to the better pilot in full up engagements, or who has more fuel, yet F-16's are usually credited with much superior maximum G, much superior acceleration, much better sustained turn rates and greater specific excess power. Despite these advantages, F-16's don't clearly dominate Hornets in dog fights...

If you want to compare the publicly released KPP's for the F-35 to the F/A-18E/F Super Hornet, you can compare to the 2 attached documents to that effect...

I think the more useful chart is the overall air to air performance goals for the F-35. The F-35 should be better than the F-16C, F/A-18C, F/A-18E and much better than the AV8-2B and A-10C which, when combined with it's overwhelming sensor, LO, EW and C4I capabilities, will produce a superb air combat aircraft.

 

[VerySneaky]

Thanks guys this has been quite helpful!

 

[colay]

Thanks guys this has been quite helpful!

Additional related F-35 information that you may find helpful.

F-35 and Current Weapons | SLDInfo

 

[ADMk2]

Thanks guys this has been quite helpful!

No problems, the other issue is that the F-35 while it will have reasonable maneuver performance (anything that can maneuver better than an F-16C or F/A-18C can never be called "bad") it's combat capability even for dogfighting isn't predicated upon this.

It's predicated on doing everything humanly possible to allow the F-35 the first shot capability. That's why it has the super funky helmet, why it has 360 degree DAS and why it will be armed with increasingly agile and capable missiles.

The idea is that the F-35 will rarely need to turn to kill it's opponents...

 

[fretburner]

Reading through this Flight Global article (Link) which has been discussed here... makes me wonder:

Is it common for the Pentagon or USAF to lower the "performance bar" of aircraft this late? If yes, were the performance bars of the F-22 and F-18E/F lowered, similarly?