The F-35 Thread

[NineLine]

I've heard that figure thrown around before.

 

The M=0.8 and the aircraft load are the assumptions, IIRC...

 

I think 99% of the theories thrown around are assumptions, we really dont know what the F-35 will do until its put into some serious scenarios with experienced pilots at the stick. Even then, how much of that will be made public is pretty hard to say, but I would assume we will only get bits and pieces, and never really enough to come to any real conclusions...

[alpha7-bravo4]

Here is a very interesting discussion ongoing. (with a lot of explanations)

https://www.reddit.com/user/Dragon029?count=26&before=t1_d0r62ye

[Hummingbird]

Can you elaborate on how this works? I must be blind because for the life me I cannot see all that lift going on!

 

The large leading edge root extensions on the F/A-18E form a big lifting surface on a large portion of the front fuselage section. In addition to this a small gap on the top & inner sides of the intakes helps keep the boundary layer intact and better direct the airflow around the rest of the fuselage.

 

The F/A-18C had an even more intricate design solution with a duct splitting the air entering the space in between the nacelles in two, redirecting one part under the fuselage and accelerating the other part up over the fuselage through an opening, generating additional lift.

 

You can see it here:

Edited March 9, 2016 by Hummingbird

[Sweep]

I think 99% of the theories thrown around are assumptions, we really dont know what the F-35 will do until its put into some serious scenarios with experienced pilots at the stick. Even then, how much of that will be made public is pretty hard to say, but I would assume we will only get bits and pieces, and never really enough to come to any real conclusions...

 

Agree 150% (if that's even possible...)

 

Fun to imagine things, though! :D

 

Maybe 40 years from now, we'll know more...

 

It'd be cool to flip through an old (current???) -34 manual for an F-35 at some point! :book:

[Boagrius]

Wasn't there a Lockheed report some years back that put the F-35A's sustained load factor at ~4.9 G's at Mach 0.8 at 15 kft? This whilst armed with two AMRAAMs internally.

 

If this is at all indicative of the current iterations' performance then that would mean its STR is little better if at all than that of an F-4 Phantom.

 

I think you and others might benefit from/enjoy this:

 

PART 1

 

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

 

PART 2

 

http://elementsofpower.blogspot.com.au/2013/05/the-f-35-and-infamous-sustained-g-spec.html

 

PART 3

 

http://elementsofpower.blogspot.com.au/2013/05/the-f-35-and-infamous-sustained-g-spec_26.html

 

PART 4

 

http://elementsofpower.blogspot.com.au/2013/06/the-f-35-and-infamous-sustained-g-spec.html

 

 

About the author:

 

"I am a '3rd Generation Aerospace' Professional and a retired Air Force Senior NCO. I maintained and tested airborne precision guided weapons the first half of my Air Force career [including AIMVAL/ACEVAL, TASVAL79, AIM-9L FOT&E--IYAAYAS!] and flight tested RPVs, Drones and Cruise Missiles [XBQM-106A, Pave Tiger/Panther, CALCM, ACM and 'others'] the second half. Since my AF retirement I have worked on many aircraft, UAV and weapons programs. I have worked systems, flight, and laboratory test programs about half the time, and have worked R&M Engineering, Depot Operations, and Operations Analysis (Combat and Logistics) the other half, I am now the Lead Engineer xx x xxxxxxxxxxxx xxxx xxxx (doing 'stuff') on yet another major weapon systems program and still involved in a wide range of Aerospace Engineering and Military Operations Research activities for multiple programs."

 

 

Ultimately all we can do is speculate about this stuff - I very much doubt we can simply have a cursory look at publically available pictures and info to make any firm conclusions. That said, the above makes for a good read if that's what you want to investigate.

Edited March 10, 2016 by Boagrius

[Exorcet]

I don't think I'd cite the F-18 as being the ultimate in blended body. The F-35 seems to have better blending on the top. The F-18 is actually a bit inbtween something like the F-16/Su-27 and the old box with wings designs before LERX's.

 

The only lifting body problem I see for the F-35 is that the fuselage is tall. A lesser issue is that the bottom isn't completely flat, but all of this area is influenced by the lower surface of the wing. Velocity there will be low and pressure should be fairly uniform. The entire forward half of the plane probably manages vortex lift as well, which likely contributes to its very high AoA capability.

 

I have a hard time seeing the plane as deficient to what's already out there, but it's certainly not meant to be the king of dogfighting.

[Hummingbird]

I don't think I'd cite the F-18 as being the ultimate in blended body. The F-35 seems to have better blending on the top. The F-18 is actually a bit inbtween something like the F-16/Su-27 and the old box with wings designs before LERX's.

 

100% agreed, it is far from optimal, but IMO the F-18 at least incorperates it to an extent, but ofcourse not to the degree of the F-16 and nowhere near that of the Su-27 or F-14.

 

The only lifting body problem I see for the F-35 is that the fuselage is tall. A lesser issue is that the bottom isn't completely flat, but all of this area is influenced by the lower surface of the wing. Velocity there will be low and pressure should be fairly uniform. The entire forward half of the plane probably manages vortex lift as well, which likely contributes to its very high AoA capability.

 

Yes and it is this tall nature that gives it such a boxy shape. To the credit of engineers however they seem to have shaped it as optimally as you could keeping in mind what needs to fit in that space, esp. on the B model, not to mention the stealth precautions.

 

I have a hard time seeing the plane as deficient to what's already out there, but it's certainly not meant to be the king of dogfighting.

 

The C model I see as a very promising aircraft when compared with the aircraft it is destined to replace (F/A-18E), but I have my worries concerning the F-35A based on the same premise of what it is intended to replace.

[Boagrius]

*Obnoxious repost due to new page of thread*

 

^ Hummingbird I think you and others might benefit from/enjoy this:

 

PART 1

 

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

PART 2

http://elementsofpower.blogspot.com.au/2013/05/the-f-35-and-infamous-sustained-g-spec.html

 

PART 3

 

http://elementsofpower.blogspot.com.au/2013/05/the-f-35-and-infamous-sustained-g-spec_26.html

 

PART 4

 

http://elementsofpower.blogspot.com.au/2013/06/the-f-35-and-infamous-sustained-g-spec.html

 

 

 

About the author:

 

"I am a '3rd Generation Aerospace' Professional and a retired Air Force Senior NCO. I maintained and tested airborne precision guided weapons the first half of my Air Force career [including AIMVAL/ACEVAL, TASVAL79, AIM-9L FOT&E--IYAAYAS!] and flight tested RPVs, Drones and Cruise Missiles [XBQM-106A, Pave Tiger/Panther, CALCM, ACM and 'others'] the second half. Since my AF retirement I have worked on many aircraft, UAV and weapons programs. I have worked systems, flight, and laboratory test programs about half the time, and have worked R&M Engineering, Depot Operations, and Operations Analysis (Combat and Logistics) the other half, I am now the Lead Engineer xx x xxxxxxxxxxxx xxxx xxxx (doing 'stuff') on yet another major weapon systems program and still involved in a wide range of Aerospace Engineering and Military Operations Research activities for multiple programs."

 

 

Ultimately all we can do is speculate about this stuff - I very much doubt we can simply have a cursory look at publically available pictures and info to make any firm conclusions. That said, the above makes for a good read if that's what you want to investigate.

Edited March 10, 2016 by Boagrius

[Boagrius]

The C model I see as a very promising aircraft when compared with the aircraft it is destined to replace (F/A-18E), but I have my worries concerning the F-35A based on the same premise of what it is intended to replace.

 

The C model is not replacing the F/A18E or F. That will be left to F/A-XX down the track. The F35C's job will be to replace the USN's classic Hornets.

Edited March 10, 2016 by Boagrius

[Hummingbird]

I read that article several years ago Boagrius, doesn't really sway my opinion anymore than Pierre Sprey does tbh - and Sprey has said some pretty damn odd stuff.

[Boagrius]

I read that article several years ago Boagrius, doesn't really sway my opinion anymore than Pierre Sprey does tbh - and Sprey has said some pretty damn odd stuff.

 

Not a problem. As I said, we are all taking stabs in the dark at the end of the day. The task of "crunching the numbers" on an aircraft when much/all of the pertinent data is not publically available is always going to be one that is fraught with difficulty (at best...perhaps futile at worst) - especially when you lack the qualifications to do so.

 

That said I find Pierre to be much less credible than the source I posted - at least the above appears to be an evidence based argument from someone with a modicum of expertise on the matter. Pierre is little more than a zealot at this point, and a cursory glance at his reasoning makes this painfully obvious.

Edited March 10, 2016 by Boagrius

[Hummingbird]

Not a problem. As I said, we are all taking stabs in the dark at the end of the day. That said I find Pierre to be much less credible - at least the above appears to attempt to be an evidence based argument from someone with a modicum of expertise on the matter. Pierre is little more than a zealot at this point, and a cursory glance at his reasoning makes this painfully obvious.

 

Yes I agree in regards to Sprey, in the beginning I could at least see reason behind a few of his points, but as of late I've watched & read him make so many ignorant statements & false claims that I simply can't take him seriously anymore.

 

I initially gave him the benefit of the doubt considering his seemingly impressive background, but then things certainly started to unravel.

[Exorcet]

100% agreed, it is far from optimal, but IMO the F-18 at least incorperates it to an extent, but ofcourse not to the degree of the F-16 and nowhere near that of the Su-27 or F-14.

Right, though I wouldn't put the F-18 higher than the F-35 in that list.

 

 

 

Yes and it is this tall nature that gives it such a boxy shape. To the credit of engineers however they seem to have shaped it as optimally as you could keeping in mind what needs to fit in that space, esp. on the B model, not to mention the stealth precautions.

The height is more of a slight deviation from ideal instead of a drawback though. As long as air mostly goes front to back and doesn't separate, the height doesn't matter. Thick airfoils produce more lift than thin ones.

 

 

 

 

The C model I see as a very promising aircraft when compared with the aircraft it is destined to replace (F/A-18E), but I have my worries concerning the F-35A based on the same premise of what it is intended to replace.

I think the A has the least to worry about as it's less handicapped by additional requirements. It will probably have to keep speed up to perform at its best (though a large diameter turbofan and high dry thrust are good for low speeds) but I don't think the design is a step back from 4th gen. Other than the short wingspan, there is nothing that stands out to me as an obvious disadvantage.

[Gannet]

Interesting paper by the UK's Royal United Services Institute about integrating the F-35 into both RAF and RN. Emphasis on situational awareness and systems integration - squadrons of ISTARs with teeth. Sorry if previously posted...

 

[ame=https://rusi.org/sites/default/files/20160201_whp_maximum_value_from_the_f-35_web.pdf]https://rusi.org/sites/default/files/20160201_whp_maximum_value_from_the_f-35_web.pdf[/ame]

[probad]

Emphasis on situational awareness and systems integration - squadrons of ISTARs with teeth.

This is really what gets me excited, the F-35 really represents a different paradigm which I expect will become the true mark of the 5th generation. It's not exactly a new paradigm, but the F-35 is new in how purely it expresses the US appreciation for target acquisition as the priority issue. This is in contrast to many other countries (and commentators!) that emphasize the most obviously visible aspects of force (airframe, munitions performance) while quietly brushing aside considerations on how to actually apply them to a highly uncooperative target.

Interestingly, while other countries have been scrambling to acquire new EW platforms the last 20 years, the US has stuck with the old E-3, even so far as to cancel the replacement program; I have to wonder if it is at least in part because platforms like the F-35 will quietly come to represent a new, distributed approach to EWC.

Edited March 10, 2016 by probad

[Emu]

I'm referring to the history of LOAL launches used without m-link ... the results were poor. :)

Well I can't be absolutely certain that ASRAAM doesn't have a datalink but I can't find proof that it does either. However a 5+km OTS shot at low altitude is not an easy test to pass. So I'll leave a question mark on that.

 

 

 

Ah ok, I think I see what you mean: This is used to reduce trim drag and is (AFAIK) most useful during cruise, allowing the aircraft to deflect the horizontal stabilizers less. Regarding high-speed turns, I'm not sure it's used at all unless it's at supersonic speeds ... but the physics of those turns are a little different AFAIK.

 

In a missile, TVC is typically used to reduce Rmin in the initial turn.

Okay I see.:thumbup:

 

 

I think CUDA is just a thing on paper right now, but we will see :)

Definitely a nice to have. It also looks like it's due to be the same size as SDB and SPEAR, and I think BAE is working on a common launcher for Brimstone and SPEAR, so joined up NATO thinking (which is maybe a big ask;)) would be to look at a common launcher for all 1800x180mm weapons (CUDA, SDB, SDBII, SPEAR, Brimstone) and maybe allow for mixed loads too.

[Hummingbird]

Right, though I wouldn't put the F-18 higher than the F-35 in that list.

 

To me it looks better shaped in terms of redirecting the incoming air than the F-35 if we are focusing on how efficiently it will generate lift. The combination of large root extensions and smooth rerouting of airflow around the intakes is what leads me to this opinion.

 

The height is more of a slight deviation from ideal instead of a drawback though. As long as air mostly goes front to back and doesn't separate, the height doesn't matter. Thick airfoils produce more lift than thin ones.

 

If we look at this like an airfoil it is how the leading edge is shaped which causes issues IMO. The first thing the air meets on the F-35 are two open intakes, on an airfoil this means a loss in lift. On the F-18 the air is instead first met by a sharp leading edge, flat on the bottom and curved on the top. The bottom airstream is then more smoothly redirected about halfway down the fuselage.

 

I think the A has the least to worry about as it's less handicapped by additional requirements. It will probably have to keep speed up to perform at its best (though a large diameter turbofan and high dry thrust are good for low speeds) but I don't think the design is a step back from 4th gen. Other than the short wingspan, there is nothing that stands out to me as an obvious disadvantage.

 

The C already seems quite impressive though when put up against the F/A-18.

[Rangi]

Thankfully these days aircraft are not designed on looks, but with computers and wind tunnels. It must have been a very big computer they did the F-35 with, that could work out the RCS calculations as well as the aerodynamics and have room for that big engine, internal weapons and lots of sensors. ;-)

[Hummingbird]

Windtunnels and mathematics have been used for quite a while ;) Today you are able do these things much faster though due to computer based flow simulation, but in the end it all has to be verified in the windtunnel, even today.

[Dudikoff]

The F/A-18C had an even more intricate design solution with a duct splitting the air entering the space in between the nacelles in two, redirecting one part under the fuselage and accelerating the other part up over the fuselage through an opening, generating additional lift.

 

I don't really dig aerodynamics so can you please explain how this design with a duct in the LERX is generating additional lift?

[SkateZilla]

I don't really dig aerodynamics so can you please explain how this design with a duct in the LERX is generating additional lift?

 

By re-directing a portion of Intake Air both up and over the body of the fuselage, and across the bottom, the fuselage becomes a lift surface.

[Exorcet]

I think in the case of the YF-17 there were instability issues without the duct. Basically the LERX was too big/not shaped properly and air couldn't smoothly flow along the top. I'm not sure if I'm remembering this correctly though and I'll need to look it up.

[Donut]

http://www.af.mil/News/ArticleDisplay/tabid/223/Article/688355/f-35-to-touch-down-at-air-shows-around-the-world.aspx

 

It looks like some of us will get to see the F-35A fly this year at Air Shows. I live close to Langley Air Force Base and plan on going to their Air Show in April. I hope the F-35 will do some solo passes and not just fly in formation with the Heritage Flight. It will be interesting either way though to see the F-35 up close and in flight.

[NineLine]

http://www.af.mil/News/ArticleDisplay/tabid/223/Article/688355/f-35-to-touch-down-at-air-shows-around-the-world.aspx

 

It looks like some of us will get to see the F-35A fly this year at Air Shows. I live close to Langley Air Force Base and plan on going to their Air Show in April. I hope the F-35 will do some solo passes and not just fly in formation with the Heritage Flight. It will be interesting either way though to see the F-35 up close and in flight.

 

Around the world... 15 shows in the US and 1 in England.... its a small world after all :)

[cichlidfan]

Hmmm, do I make a trip to Langley or Baltimore. Decisions, decisions.

 

Btw. here is an image from Google Earth, Langley AFB