Forum: General F-35 Forum

sewerrat wrote:

All I know is that John Beesley has stated that the -35 is on par with the -16 in turning and accelleration; and that the -35 is on par with the -22 throughout the subsonic region. As others have said, looking at "static" t/w and wing loading numbers doesn't a prediction make about performance.

The initial variant of that big PW engine isn't going to be the same throughout the life cycle of the -35 either. We may well see a 50,000lb thrust version before its said and done. That should up the ante, so to speak. I don't think the -35 is as big as a slug and is purported by those just looking at wing loading and t/w numbers.

And that was more my point than anything. From what I had read I was surprised any metric showed it as on par with any of these planes. That was more more prompt for posting the T/W numbers than anything. I realize it is just a component but it is an important one all the same. I figured it would lag well behind the planes many seem so worked up about like the SU-35.

F-16.net Sponsor

sewerrat wrote:

All I know is that John Beesley has stated that the -35 is on par with the -16 in turning and accelleration; and that the -35 is on par with the -22 throughout the subsonic region. As others have said, looking at "static" t/w and wing loading numbers doesn't a prediction make about performance.

The initial variant of that big PW engine isn't going to be the same throughout the life cycle of the -35 either. We may well see a 50,000lb thrust version before its said and done. That should up the ante, so to speak. I don't think the -35 is as big as a slug and is purported by those just looking at wing loading and t/w numbers.

I don't see how that could possibly be. It weighs more than an F-15C both empty and loaded, has only 80% of the thrust and only 75% of the wing.

How can it perform as well as an F-15, let alone a F-16?

The key issue is Drag/external ordinance. An F-35A can out turn and acellerate an F-16 with its wet tanks and weapons..
Why must we always go back to this?
I have never seen any US official statement that an F-35A must out turn an clean F-16... I doubt this will be a requirement on the F-35A.

An often-forgotten factor...

delvo wrote:

An often-forgotten factor...

I'm not sure which way you're meaning this. Basically, using the engine to change direction of movement is not a great idea.

Let's say you want to pull 9g, and your t:w is let's say 1. If you pitch to 90 degrees, your engine can contribute no more than 1g, leaving your wings to contribute 8g. Which they won't do at 90 degrees to the direction of flight. And meanwhile you get all that added drag from pitching your plane's largest cross section into the direction of flight. And you lose all the thrust keeping your plane moving, because now it's all being used to change the plane's direction of motion. The graphic strongly illustrates why the F-35 doesn't have and doesn't need thrust vectoring. The F-22 has it because it flies at altitudes where it might provide more efficient pitch control than control surfaces in the thinner air, not for maneuvering in dogfights.

What you want is a plane with the ability to generate 9g at relatively little pitch angle. But it's a plane. To get that ability you have to generate a lot of lift, which means a lot of extra drag for nothing when you're not generating 9g. Everything's a trade-off. The F-35 seems, I think, to have traded the need to pitch up a bit more for a more powerful engine and lower drag through more advanced aerodynamics and internal stores carriage.

Using the engine to change direction makes sense when you're talking about missiles, where t:w is on the order of 20 or more. Didn't the old Nike missiles have a t:w somewhere around 100? To get that, you have to trade off range and durability in a way an aircraft can't.

sewerrat wrote:

All I know is that John Beesley has stated that the -35 is on par with the -16 in turning and accelleration; and that the -35 is on par with the -22 throughout the subsonic region. As others have said, looking at "static" t/w and wing loading numbers doesn't a prediction make about performance.

The initial variant of that big PW engine isn't going to be the same throughout the life cycle of the -35 either. We may well see a 50,000lb thrust version before its said and done. That should up the ante, so to speak. I don't think the -35 is as big as a slug and is purported by those just looking at wing loading and t/w numbers.

Such claims must be put into the perspective. The F-35 may match the performance of the F-22 in a very few areas subsonic, but it certainly won't across the board. A relatively large frontal cross section stemming from the requirement to carry stores and a lot of fuel internally in such a compact aircraft, a clearly higher wing loading and inferior thrust weight ratio, lower sweep angles, no TVC, smaller control surfaces etc. It's ridiculous to believe that the F-35 could match the performance of the Raptor overall in most areas. Sure it will turn as well as other aircraft at high speeds with 9 g at lower altitudes and it may not be much worse when it comes to sub sonic acceleration, but anything else is physically nonsense in comparison to the F-22 at least. In comparison to legacy fighters it will enjoy advantages in some areas due to the internal carriage of weapons and a lot of fuel and that's what matters in the end. But this also depends on the exact configuration of the aircraft and neither aircraft can overcome the natural physical laws.

jeffb wrote:

sewerrat wrote:

All I know is that John Beesley has stated that the -35 is on par with the -16 in turning and accelleration; and that the -35 is on par with the -22 throughout the subsonic region. As others have said, looking at "static" t/w and wing loading numbers doesn't a prediction make about performance.

The initial variant of that big PW engine isn't going to be the same throughout the life cycle of the -35 either. We may well see a 50,000lb thrust version before its said and done. That should up the ante, so to speak. I don't think the -35 is as big as a slug and is purported by those just looking at wing loading and t/w numbers.

I don't see how that could possibly be. It weighs more than an F-15C both empty and loaded, has only 80% of the thrust and only 75% of the wing.

How can it perform as well as an F-15, let alone a F-16?

Drag.... Atmospheric drag. Suface area of controls, speed of constrol surface actuation, engine spool. All I can say is that you should address your concerns with John Beesley, who made these claims, and who has flown all types of 4th gen, the -22, and the -35. If he says the -35 is on par with an F-16, then I doubt he's lying.
When he says that he's flown the -35 with JDAMs and AAMs in the side bays, and there's hardly any degrade in performance, then that's a powerful statement considering how a -16 or -15 perform when loaded out with a couple of JDAMS and AAMS, and at least 1 external fuel tank to match the -35s range of operation.

Just looking at wing loading and t/w, that's just one part of a complex equation. I'm not an aeronautical engineer, but I know enough to know there's more a lot more to figuring how a plane performs than looking at just 2 parameters.

The -35 will most likely spend more time fighting at supersonic speeds than any 4th gen fighter, and has anyone commented publicly on how well it turns and bleeds or doesn't bleed energy like a 4th gen? No. Does anyone in public know how well the big PW performs at high altitudes? No. Does performance degrade like the -18s powerplants at altitude? I bet not. There's a lot that we the consuming public do not know.

Keeping loads near the COG should help its roll rate when loaded. The F-35 is shorter than the F-15C, and probably enjoys better pitch and yaw rates. The nature of the F-35's lighter structure, even being similar in size, can't possibly be a negative. I'm thinking the F-35 will generally run circles around F-16 and F-15.

The first F-35 in combat will probably also spend more time above Mach 1 than the entire fleet of F-15's ever saw. The F-35 is built to stay at speeds that the F-15 drivers can only envy, even if they do sit on more thrust.

madrat wrote:

The first F-35 in combat will probably also spend more time above Mach 1 than the entire fleet of F-15's ever saw. The F-35 is built to stay at speeds that the F-15 drivers can only envy, even if they do sit on more thrust.

Can the F-35 maintain Mach 1.2+ without afterburner? The F135 trades higher thrust from the larger fan, for supersonic performance.

The F-22 is a true supercruise capable jet.

TEG & others make some very interesting points here http://www.f-16.net/f-16_forum_viewtopi ... r-asc.html

Quote:

Can the F-35 maintain Mach 1.2+ without afterburner? The F135 trades higher thrust from the larger fan, for supersonic performance.

Someone here posted that a pilot with the 461st FTS said they could maintain around mach 1.25 without afterburner but needed it to get to that speed in the first place. Take that for what it is worth. It is not a published capability yet.

Please note that the F-35 was not contracted to supercruise, therefore Lokcheed can actually get in trouble for delivering a capability above and beyond what was contracted, because it will be seen as extra cost that could have been saved. While the capability may be useful the contractor can get in trouble for wasting tax payer money on something they were not asked to deliver.

Dumb as that sounds it is the truth of government contracts.

Sufa Viper

If I had to guess, given the F-35's shape and design characteristics, it will not be as maneuverable as the light load-out configurations of select 4th gen fighters.

But, per the F-35's defenders, that shouldn't matter. In fact, the F-35's design appears to follow the idea that maneuverability isn't as important as before. How that will work in combat, however, remains to be seen. There hasn't been a battle between equivalently equipped air forces since the Falkland's War. (I don't count the Gulf War as that was a walkover) So, we haven't had a chance to reset the maneuverability argument.

Finally, I hate to say this but the historic discrepancy between what Lockheed said and what the select acquisition report said, regarding the F-35's flight regime, makes me unwilling to completely trust any Lockheed statement about the program. (and the flight test pilot is Lockheed's) E.g. the issue with supersonic flight & airframe peeling or the transonic buffeting. So, I don't completely trust the test pilot when he says the F-35 as maneuverable, if not better, than the F-16. Its probably true in a bunch of flight regimes (loaded with gas + bombs), but still one can't be sure.

If supercruise is a byproduct of having a clean airframe and a high thrust engine (both are design requirements) then nothing was "added" to make it supercruise and therefore no money was wasted.

A little perspective --

Jon wasn't providing a detailed performance comparison; he was asked to give his general impressions of F-35 up-and-away performance (given that he had flown F-16, F-22 and F-35). At the altitude that the USG has chosen to assess subsonic acceleration, a combat configured (once again, with a USG-specified internal load) F-35A is very comparable to F-22. It may or may not be comparable to F-16 acceleration depending on what one chooses to characterize as a combat load for the F-16, since the F-16 cannot come close to matching F-35 missions systems capabilities without hanging a T-pod, an HTS, and an ALQ to the tune of significant increase in drag index and consequential decrease in accel and turn capability. In the most common configuration that Vipers go to war with (not the made-up stuff in blogs nor the fun stuff often flown/trained with in the Restricted/Warning Areas), the F-35 is easily better in a wide range of performance measures.

Of course, that's also before we start talking about fuel capacity and range. A clean F-35A has ~9200# on board at 50% fuel -- without the drag penalty of external fuel tanks. If the Viper is not carrying external fuel (which means it's not in a combat configuration), it has about 3500# of JP on board at the 50% fuel number. That translates to "less" in a lotta different aircraft performance measures where "more" is not just 'better,' but decisively so. And for those of you who believe that external fuel tanks are dropped a la those wonderful WWII pics of P-51s over Germany, think again. It rarely happens, and usually only in the context of an IFE. You're certainly not going to pickle the T-pod, the HTS, or an ALQ.

The F-35 is not the 'dog' that detractors routinely suggest. Nor is it an F-22 (aerodynamically). But, combat configured, it is a significant advancement in overall capability compared to the jets it was designed to replace. Think about it -- do we really think the USAF, the USMC, the USN, the UK, the Israelis, the Dutch, the Turks, Norway and Japan are that stupid?? Come on man... Cool

Forum: General F-35 Forum

F-35 Kinematics in Air to Air configuration