The F-35 Thread

[Weta43]

It means there is a potential for poor sustained turn performance, but that's not something any of us can determine

 

Haven't the USN said the sustained turn rate is somewhere around 4.5G ?

 

 

The F-35 could have very effective aerodynamic performance, producing a higher coefficient of lift per square meter of wing.

 

It's true they might have done some black magic and be able to generate more lift per unit area than previous aircraft.

 

You've got to hope so...

[Exorcet]

Haven't the USN said the sustained turn rate is somewhere around 4.5G ?

Altitude? Speed? Payload?

 

"4.5g" is enough to make it the most agile fighter ever if you ignore context.

 

 

 

 

It's true they might have done some black magic and be able to generate more lift per unit area than previous aircraft.

 

You've got to hope so...

It's not magic, it's airfoil and planform.

[Weta43]

Sorry - not my numbers & the D.O.D. didn't really give context :

 

"The US Department of defence'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."

 

(Extended by 43 seconds... )

 

FlightGlobal.com quoting the US D.O.D. - believe them or don't.

 

A maximum sustained turn performance of less than 5g would be the equivalent of an F-4 or an F-5, but if you think perhaps the D.O.D was deliberately downplaying the capabilities of the aircraft by quoting figures for maximum weight, minimum controllable airspeed turns, or perhaps for flight regimes above the stated ceiling, in order to lull foreign air forces into complacency - sure - could be a good plan....

 

(Not black magic but airfoil and planform eh ? who'd have guessed.)

Edited March 9, 2014 by Weta43
To play nicely

[ФрогФут]

No altitude is given. Though additional 43 seconds of acceleration for C is pretty much anyway - payment for bigger wings (don't seem to really help, as landing speed is still high, according to other reports).

Edited March 9, 2014 by ФрогФут

[Basher54321]

Sorry - not my numbers & the D.O.D. didn't really give context :

 

"The US Department of defence'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."

 

(Extended by 43 seconds... )

 

FlightGlobal.com quoting the US D.O.D. - believe them or don't.

 

A maximum sustained turn performance of less than 5g would be the equivalent of an F-4 or an F-5, but if you think perhaps the D.O.D was deliberately downplaying the capabilities of the aircraft by quoting figures for maximum weight, minimum controllable airspeed turns, or perhaps for flight regimes above the stated ceiling, in order to lull foreign air forces into complacency - sure - could be a good plan....

 

(Not black magic but airfoil and planform eh ? who'd have guessed.)

 

 

There is a lot more to sustained G than what you think:

 

http://elementsofpower.blogspot.co.uk/2013/04/the-f-35-and-infamous-sustained-g-spec.html

 

Also bear in mind that the quoted acceleration "thresholds" are in the transonic region where parasitic drag really starts to matter.

 

 

Those DOTE figures unfortunately are very misleading without all the other required factors

[Exorcet]

Sorry - not my numbers & the D.O.D. didn't really give context :

 

"The US Department of defence'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.

 

Basher's link seems to cover this well. No context and the g number is hard to use. If you assume it's a standard speed/alt/payload that's used with other aircraft; is the payload internal or external (drag), how is this payload defined (in particular is the F-35 being penalized for being better at carrying fuel than the teen series)?

 

 

 

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."

 

(Extended by 43 seconds... )

CDw, wing loading isn't doing any favors for the F-35C in acceleration above M.7, maybe even lower than that.

 

FlightGlobal.com quoting the US D.O.D. - believe them or don't.

Believe them or not, I'm not sure how to make use of them.

 

A maximum sustained turn performance of less than 5g would be the equivalent of an F-4 or an F-5, but if you think perhaps the D.O.D was deliberately downplaying the capabilities of the aircraft by quoting figures for maximum weight, minimum controllable airspeed turns, or perhaps for flight regimes above the stated ceiling, in order to lull foreign air forces into complacency - sure - could be a good plan....

Foreign nations presented with this information would ask for context so they could make sense of it. Hanging weapons outside of the aircraft (because all previous fighters would have had to do so) or determining fuel by percent rather than fuel fraction or efficiency would impact the turn rate. I doubt that the F-35 was being flown at near stall speeds or above 60,000 ft, but for all we know (from your source) it could have.

 

(Not black magic but airfoil and planform eh ? who'd have guessed.)

L = W = .5*rho*V^2*CL*S

 

CL goes way up or down just by demand from the weight. CL at 9g is 9 times CL at 1g. Making more CL is not magic by any means.

 

It does tend to increase CDw or make it noticeable sooner so it can't really be increased with care on a fighter. Spreading your lift out on more surfaces than wings lets you lower the CL and may be better for CDw. CDw is more complex than that though, my hunch that the F-35C has more CDw despite lower W/S (and thus CL) is because the wings would effect the cross sectional area distribution as you go down the plane. It's also heavier.

[Exorcet]

There is no point arguing this unless you show the exact equations you are using to come to these conclusions and for the specific cases where your assumptions are valid. Aerodynamics and Flight Control are very complicated subjects and do not lend them selves well to generalities as anyone who has studied them in depth can attest.

 

I think you missed what I was specifically referring to - a specific coordinated turning maneuver case.

 

Well I've gone back and explained in more depth. If you'd like, I don't mind continuing where we left off as I couldn't see where you were trying to go.

 

Again I need to point out the equation you posted, high wing loading does not help. I think you might have been thinking of load factor instead, but wrote the wrong thing. I looked over my posts and more than once I wrote something backwards by mistake so I know it happens.

[NineLine]

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[NineLine]

odaknd0_GnI

[Cyb0rg]

Looks like the 35 (or others) is not that stealth after all..

Came across this article while browsing the site :

 

http://www.liveleak.com/view?i=02b_1395416459

[GGTharos]

Sadly clouds have obsoleted that photonic radar ...

 

It's really funny to see how 'stealth is already obsolete' while everyone's building stealth aircraft. They must not know what all these other peeps know ;)

 

(Incidentally, have you heard about the nanomaterials that turn things invisible? But wait, it gets better ... have you heard that in order for a stealth aircraft to be visible on radar, it would also have to break the laws of physics? The key functionality of stealth is a huge reduction of detection range ... not invisibility. But just that makes things really hard for surveillance and weapon radars. And guess what weapons use for guidance ...)

[Cyb0rg]

Yeah, i guess you right. Probably a raining sky would defeat the photonic stuff.

Anyway, wonder how huge will be that reduction of detection range in the (near) future. IMO is cheaper build better sensors than stealth aircrafts.

[Kuky]

Satellites are not obscured by clouds, you put these photonic radars on satellites and you can track about anything... you can fly bellow the clouds but that makes you fly shorter, your weapons have shorter range, and you are exposed to ground sensors.

 

PS: I'd like to see how long till they can make invisible planes :)

Edited March 22, 2014 by Kuky

[GGTharos]

How are those sats working out for finding flight 370? :)

 

 

They've already made armor (as in tanks) invisible to IR btw.

 

Satellites are not obscured by clouds, you put these photonic radars on satellites and you can track about anything... you can fly bellow the clouds but that makes you fly shorter, your weapons have shorter range, and you are exposed to ground sensors.

 

PS: I'd like to see how long till they can make invisible planes :)

[Kuky]

How are those sats working out for finding flight 370?.

 

The way I understand this photonic radar is it can/will be used to track objects (planes I guess)and not look for them as conventional radar. Its bandwidth could be used for communication (data, video, position etc) so if you were tracking in already you could continue to track it (like current lasers)... and it's not on the satellites yet, right, still being worked on?

 

And like I said, I'd like to see how long till they can have invisible planes that are still aerodynamic (and efficient)... and still invisible to radar, lasers, and optics combined.

[Kuky]

They've already made armor (as in tanks) invisible to IR btw.

 

What will happen to that tank when it gets into dust and dirt and mud? (remember war is very "dirty") Will the tech covering it still work? :music_whistling:

[GGTharos]

I just don't see the difference when it comes to non-cooperative detection and tracking. It's still subject to all the same stuff radar is, the challenges just shift to a different part of the spectrum.

 

My point here with the satellites was that no one has even mounted a radar for such surveillance on satellites (that we know of), and that makes sense given the clutter, volume of space that needs to be looked at etc. I don't see how photonic radar would deal with these challenges. It's a very new technology, and we've seen this 'stealth is obsolete' spiel with other 'new technologies' as well. No one's saying LIDAR is the end of stealth, and AFAIK, it isn't exactly that different from this stuff.

 

The way I understand this photonic radar is it can/will be used to track objects (planes I guess)and not look for them as conventional radar. Its bandwidth could be used for communication (data, video, position etc) so if you were tracking in already you could continue to track it (like current lasers)... and it's not on the satellites yet, right, still being worked on?

 

And like I said, I'd like to see how long till they can have invisible planes that are still aerodynamic (and efficient)... and still invisible to radar, lasers, and optics combined.

[GGTharos]

As far as I could guess, the dust and mud would take on the temperature of the camo blocks.

 

What will happen to that tank when it gets into dust and dirt and mud? (remember war is very "dirty") Will the tech covering it still work? :music_whistling:

[Flagrum]

I heared somewhere that they are researching so called "meta materials" that allow light to "pass around" an object covered with that stuff and thus making it invisible. Think about the camouflage technique used by the Predator in that movie with the same name ... :o)

 

Atm this only works for tiny objects (a few atoms iirc) and only for a very narrow band of electromagnetic waves. So, yeah, just fundamental research atm and seemingly still a looooong way to go ... :o)

 

edit:

http://en.wikipedia.org/wiki/Metamaterial

Edited March 22, 2014 by Flagrum

[winz]

Satellites are not obscured by clouds, you put these photonic radars on satellites and you can track about anything... you can fly bellow the clouds but that makes you fly shorter, your weapons have shorter range, and you are exposed to ground sensors.

 

PS: I'd like to see how long till they can make invisible planes :)

There are few problems with satellite mounted radars. One of the bigest is that the area they can scan is pretty much set by their orbit. Imho they will be at lower orbit, that means they will overfly your area of interest in matter of minutes. Then you'll have to wait hours for another pass near your area. I say near because in each pass they will overfly a different area (because the world is spinning under them).

 

So satellites are great for taking photos you can analyze later, because you can wait for the window the sattelite will overfly your area of interest, take bazillion of photos during the overpas. But not much for real-time tracking

[Faith]

Satellites are not obscured by clouds, you put these photonic radars on satellites and you can track about anything... you can fly bellow the clouds but that makes you fly shorter, your weapons have shorter range, and you are exposed to ground sensors.

 

PS: I'd like to see how long till they can make invisible planes :)

 

Skunk Works made several "invisible" airplanes in the 70's I believe. They could not figure out how to make the cockpit "invisible" also.

[NineLine]

 

http://theaviationist.com/2014/03/28/f35-and-p38-luke/

[aaron886]

What? A post about the F-35? Cool pic. In case anyone missed it:

 

[SkateZilla]

:music_whistling::music_whistling:

http://www.military.com/daily-news/2014/04/07/boeing-growler-eclipses-f35s-stealth-advantage.html?ESRC=todayinmil.sm

[joey45]

The F35 is not a do all aircraft...