The F-35 Thread

[probad]

conceptually it can be possible that if you have better the better itr performance, it can make up for slightly worse str, which is better for regaining energy for another itr pull.

itr capacity happens to be more relevant for purposes of defending because they're far less predictable than str maneuvers.

 

ggtharos has the better point though.

 

this whole idea of the f-35 being in a neutral merge is just utter bunk, either someone sneaks up on it -- not a neutral merge -- or it sneaks up on someone else, also not a neutral merge.

its as if we were in 1867 and someone proposed wearing camos and lying in the dirt with scoped rifles and people keep asking how they would hold up in the firing line formation.

Edited June 28, 2017 by probad

[Exorcet]

playing the kinematic game against the missile is all about losing energy, because you're playing off the fact that you have energy income and the missile doesn't. if you don't want to lose energy, guess what, you're not raising the stakes for the missile either.

 

How so? The missile has limited energy regardless. All you need to do is outlast it. You can do this with sustained maneuvers. The missile has to chase you and it spends its energy faster. Spending energy quickly can be dangerous if you can't get it back. The missile has finite energy, but it starts off with far more energy than the fighter has. The worst thing you can do is get into a low energy state at the wrong time.

[probad]

i don't think any nation's aircraft runs into energy issues outwalking missiles near rmax.

 

you are imagining some hyperbolic scenario where someone decides for no good reason to pull 10g aerobrake in bvr, that's not even relevant to the discussion.

Edited June 28, 2017 by probad

[Exorcet]

i don't think any nation's aircraft runs into energy issues outwalking missiles near rmax.

Forcing the missile to maneuver will decrease the effective Rmax, that's one of the things I'm getting at.

 

you are imagining some hyperbolic scenario where someone decides for no good reason to pull 10g aerobrake in bvr, that's not even relevant to the discussion.

That's the not the only way to deplete energy. You can do in slowly by exceeding your sustained turn rate and either not gaining energy between maneuvers or just not gaining as much energy as you spent. This is pretty fuzzy without considering specific scenarios I guess. I'm not meaning to say that flying right at your sustained limit is the best maneuver for every case.

[aaron886]

This thread has really degenerated. Can we go back to F-35 news?

 

Geopolitically important:

 

F-35B Lightning II arrive in Okinawa

[Emu]

G is a function of speed and rate, in other words the F-35C will probably simply pull the same rate but at a lower speed and therefore G, which on top has the effect of reducing the turn radius. Thus the C variants display can be made to look even more "tight", which is usually what people find impressive - hence the obsession with A's tight snap at the top of loops. People love the high alpha show off, myself included (Im a sucker for it), but in real combat it is the sustainable rate that really matters, or atleast it used to be as nobody knows for real how xombat effective the new high offbore missiles would be against an advanced foe.

For a given radius the speed of the A can be approximately 10% higher, so the rate will also be higher. The C will be able to perform tighter turns due to lower speeds but not at the same rate. TWR also plays a part here due to alpha and the C is significantly heavier, therefore the thrust component of acceleration in the turn and climb direction will be lower.

[Hummingbird]

For a given radius the speed of the A can be approximately 10% higher, so the rate will also be higher. The C will be able to perform tighter turns due to lower speeds but not at the same rate. TWR also plays a part here due to alpha and the C is significantly heavier, therefore the thrust component of acceleration in the turn and climb direction will be lower.

 

Yes youre right, what I meant to say was that the C will be able to achieve the same G lower down the speed range, leading to a tighter turn. A brainfart on my part.

 

But it all depends on how much extra lift the C has in relation to excess thrust compared to the A. More lift means less AoA and therefore drag for the same deg/sec. AFAIK the C is limited to the same 7Gs as the A atm, so at airshows the C has the potential to look even more impressive as it will be able to pull that G at a lower speed.

Edited June 29, 2017 by Hummingbird

[Emu]

Yes youre right, what I meant to say was that the C will be able to achieve the same G lower down the speed range, leading to a tighter turn. A brainfart on my part.

 

But it all depends on how much extra lift the C has in relation to excess thrust compared to the A. More lift means less AoA and therefore drag for the same deg/sec. AFAIK the C is limited to the same 7Gs as the A atm, so at airshows the C has the potential to look even more impressive as it will be able to pull that G at a lower speed.

Not quite that simple either, lower AoA means lower Cd but the C has more wing area, so the CdA product may be the same or higher, and the extra weight combined with the extra drag will reduce the ability of the thrust to act in the lift and turn directions. There's also nothing to say Cl or Cl vs AoA will be the same for a different sized wing. All that's likely to be true is lower T-O and landing speeds because it's a carrier aircraft and was therefore probably designed that way.

 

To put the thrust drag relationships in some perspective, the specifications for the F-35A M0.8-M1.2 were downgraded by only 8s but for the C they were downgraded by 43s. So there is clearly a weight and drag penalty for the C.

[probad]

 

inverted negative-g launch testing

[Emu]

Has it fired the AMRAAM from internal bay upside-down yet?

[Tirak]

Has it fired the AMRAAM from internal bay upside-down yet?

 

Haven't found a video of that style test yet, but the F-35 does have a pneumatic launch system called that LAU-147 for AMRAAMs, so it does not appear like that will be a limitation.

[Pilotasso]

Is there such a system for the door mounted missiles? I would be surprised if they did.

[Exorcet]

Not quite that simple either, lower AoA means lower Cd but the C has more wing area, so the CdA product may be the same or higher, and the extra weight combined with the extra drag will reduce the ability of the thrust to act in the lift and turn directions. There's also nothing to say Cl or Cl vs AoA will be the same for a different sized wing. All that's likely to be true is lower T-O and landing speeds because it's a carrier aircraft and was therefore probably designed that way.

Well the C wing is not only bigger, it has a higher aspect ratio. That implies a better CL vs AoA itself to some degree.

 

To put the thrust drag relationships in some perspective, the specifications for the F-35A M0.8-M1.2 were downgraded by only 8s but for the C they were downgraded by 43s. So there is clearly a weight and drag penalty for the C.

That's a different flight regime than low speed though. While you're right, it doesn't really say much about air show performance.

[Emu]

Well the C wing is not only bigger, it has a higher aspect ratio. That implies a better CL vs AoA itself to some degree.

 

 

That's a different flight regime than low speed though. While you're right, it doesn't really say much about air show performance.

But what does it say with respect to Cl/Cd vs AoA?

 

True but air battles are not fought at airshow altitude and dropping that much energy would be foolish. Rmin also tends to be lower speed than max STR/ITR, which is what really makes the difference.

[Exorcet]

But what does it say with respect to Cl/Cd vs AoA?

The L/D will go up as well. L/D vs AoA has dependence on the airfoil. The optimum L/D for the wing should still occur at about the same angle, but it will be at a lower speed with a larger wing.

 

True but air battles are not fought at airshow altitude and dropping that much energy would be foolish. Rmin also tends to be lower speed than max STR/ITR, which is what really makes the difference.

I agree, this partially why the A doesn't use the C's wing, it's probably a handicap in most expected combat situations. I thought the discussion was focused on Rmin turns though.

[mvsgas]

Is there such a system for the door mounted missiles? I would be surprised if they did.

 

AFAIK, yes. Look at 1:23

hBw_9zj_2iE

 

So...are you surprise? :D

 

There was another video of the F-35 sitting on a drop test pit, I'm sure is in one of these pages.

Edited July 1, 2017 by mvsgas

[mvsgas]

Wow, it just dawn on me that this thread has been going for 8 years, 6 months, 15 days and we are talking about some of the same things.

[aaron886]

[Emu]

The L/D will go up as well. L/D vs AoA has dependence on the airfoil. The optimum L/D for the wing should still occur at about the same angle, but it will be at a lower speed with a larger wing.

 

 

I agree, this partially why the A doesn't use the C's wing, it's probably a handicap in most expected combat situations. I thought the discussion was focused on Rmin turns though.

I don't think it's that simple, I don't think Cl or Cl/Cd would just remain the same for a larger wing, I see the variable deteriorating as it gets larger. Compound that with increased weight and I see the Rmin being similar. I also see the smaller wing delaying separation more successfully at higher AoAs relative to size and if you look at the inner LE on the A/B you will note a significant difference vs the C.

 

[Exorcet]

I don't think it's that simple, I don't think Cl or Cl/Cd would just remain the same for a larger wing, I see the variable deteriorating as it gets larger. Compound that with increased weight and I see the Rmin being similar. I also see the smaller wing delaying separation more successfully at higher AoAs relative to size and if you look at the inner LE on the A/B you will note a significant difference vs the C.

 

When looking at the fine details, more things can change, yes. But I have no solid data to work with. I can only go by rules of thumb with the F-35.

 

The smaller A wing will see more influence from the body and LERX that could change the high AoA performance, but because it is so much smaller, it will definitely need to pull high AoA in the first place to generate the same lift as the C wing. The C is heavier but not the weight difference is smaller than the wing area difference if I recall.

[Emu]

A low speed turn will inevitably involve high AoA though, the lack of speed has to be compensated for by AoA, but yes at lower AoA the C will likely generate more lift because that is basically a carrier landing scenario.

[Pilotasso]

AFAIK, yes. Look at 1:23

hBw_9zj_2iE

 

So...are you surprise? :D

 

 

yes :D

[Hummingbird]

Not quite that simple either, lower AoA means lower Cd but the C has more wing area, so the CdA product may be the same or higher, and the extra weight combined with the extra drag will reduce the ability of the thrust to act in the lift and turn directions. There's also nothing to say Cl or Cl vs AoA will be the same for a different sized wing. All that's likely to be true is lower T-O and landing speeds because it's a carrier aircraft and was therefore probably designed that way.

 

A lower AoA & Cl needed for the same rate means a reduced Cdi, and Cdi is by far the largest source of drag in a turn. In other words max ITR (within G limits) is increased, whilst corner speed and Rmin is reduced.

 

To put the thrust drag relationships in some perspective, the specifications for the F-35A M0.8-M1.2 were downgraded by only 8s but for the C they were downgraded by 43s. So there is clearly a weight and drag penalty for the C.

 

There's obviously going to be a drag penalty when you add more surface area, esp. when you increase wing span. But this is going to be felt mainly in straight line speed.

 

In short I definitely expect the C variant to be more capable in any turn compared with the A variant. The Rmin will 100% be smaller, there's no doubt about that, the higher lift to weight ratio will make sure of that.

 

That the LERX might have a larger percentage wise effect over the A's wing is just down to it being smaller, the same size vortice is generated on the C however and over a longer chord area as well, so the C will benefitting atleast as much from the LERX as the A, whilst at the same time enjoying the added lift of the extra wing area, larger LEF & TEF's and increased wing aspect ratio.

Edited July 4, 2017 by Hummingbird

[aaron886]

Why do people keep using "Rmin" in here? In the world of western fighter aircraft, that's a missile's minimum launch range.

[mvsgas]

This stuff makes me laugh. So a couple of years ago (and several hundred post back here) there where a couple of articles written on how the F-35 could not get near any thunderstorm etc, etc.

Looking at the F/A-18 NATOPS that has been floating around I saw this on page I-4-4

4.1.3 Prohibited Maneuvers.

4. Flight in lightning or thunderstorms.

 

So it appears F-35 is like other aircraft, Who would've thunk it?