PPRuNe Forums - Why only 7G ?

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As far as I am aware (which isn't far) the JSF is designed to tolerate 7G.

Why only 7G in a jet fighter when the pilot can for short periods endure 9G ? Is manoeuvring left to the onboard UAV's (Aim9X, Amrams) ? If so why not design to 5G or Airliner 2-3G ?

Any info gratefully received...TIM

Lots of things on a B won't like 9G! :E

They got rid of the Harrier rather than the conventional Tornado, because the Harrier couldn't supposedly do things the Tornado could, then go for another Jumping bean that cannot do or carry the load of the conventional version... I could understand it if you were going to operate in the field, but the fact we are building two bloody great carriers for them it beggars belief.

Out of curiosity how often do you drivers take F 16's and similar to the limit?
A model has a built in gun so maybe a need for aggressive manoeuvring?
B has greater basic mass with similar structure to A (except big hole forward of CofG)
C has big wing and beefed up structure for carrier ops

It could be argued that the superior stealth characteristics of F35 preclude any need for high g tolerance as the opposition will never see it; I think F117 was limited to +6g-3g? Only one was shot down by defenders using unexpected tactics to locate the ac

They were a bit strapped and couldn't afford the mods for the 9g upgrade.

The B is tight on weight anyway and I do wonder how it will cope with the almost inevitable beefing up as it matures.
The nose leg looks a little flimsy for ski jumping at heavy weight also !

Eglin F-35 initial cadre starts transition training - The DEW Line

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The veteran F-16 operational tester and Weapons School grad shared some of his impressions the F-35. The jet is powerful, stable and easy to fly.

"One of the things this aircraft usually takes hit on is the handling because it's not an F-22," Kloos says. "An F-22 is unique in its ability to maneuver and we'll never be that."

But compared to other aircraft, a combat-configured F-35 probably edges out other existing designs carrying a similar load-out. "When I'm downrange in Badguyland that's the configuration I need to have confidence in maneuvering, and that's where I think the F-35 starts to edge out an aircraft like the F-16," Kloos says.

A combat-configured F-16 is encumbered with weapons, external fuel tanks, and electronic countermeasures pods that sap the jet's performance. "You put all that on, I'll take the F-35 as far as handling characteristic and performance, that's not to mention the tactical capabilities and advancements in stealth," he says. "It's of course way beyond what the F-16 has currently."

The F-35's acceleration is "very comparable" to a Block 50 F-16. "Again, if you cleaned off an F-16 and wanted to turn and maintain Gs and [turn] rates, then I think a clean F-16 would certainly outperform a loaded F-35," Kloos says. "But if you compared them at combat loadings, the F-35 I think would probably outperform it."

The F-16, Kloos says, is a very capable aircraft in a within visual range engagement--especially in the lightly loaded air-to-air configuration used during training sorties at home station. "It's really good at performing in that kind of configuration," Kloos says. "But that's not a configuration that I've ever--I've been in a lot of different deployments--and those are the configurations I've never been in with weapons onboard."

Not really anything specifically negative but I wouldn't call it an overwhelmingly positive assesment either.
He's comparing the most capable F35 (the A) vs a run of the mill F16 with ,what sounds like, a CAS load, in which case the F35 sort of outperforms the old F16, but it doesn't seem to be so impressive when loads are lighter (eg. like only A2A missiles for air supremacy tasks).

All this knowing that besides the, albeit very capable, F16 there are also fighters like the F15, the RAFALE and Eurofighter which are all much more capable and have a substantially higher T/W ratio (let alone lower wingloading) than said F16 and ,more worrying, the F35.

I wouldn't call this a ringing endorsement for the F35A from someone who certainly is in a position to know, let alone the much heavier B and C versions.

I understand the argument about comparing performance between combat loaded aircraft rather than their airshow unloaded equivalents but isn't that what the jettison stores button is for.

It would be interesting to know which is the more quickly reconfigurable a conventional jet with hung stores /weapons or a stealh design with fuel and weapons integrated. Having said that you can still have them hung off the stealth design. What price stealth ?

Back to the 7G. Is the consensus that it is worth building jets to manoeuvre upto the restrictions imposed by the pilot or is this level of manoeuvrability not required tactically?

I thought i heard (not a pussy cat!) that USN F18 were restricted to 7G ?!?

TIM

Feel free to correct me if I'm wrong but I believe the classic Hornet was/is limited at 9G, at least the Swiss Hornet's are.
The newer Super Hornets are 7.5G, I think.

Also, just to show what a full loadout can do, a RAFALE with a full load is limited to 5.5G, mind you, a fully loaded RAFALE brings a hell of a lot of weapons and fuel to the fight.

Hornets are all 7.5g bar the Swiss ones.

F35A = F16 replacement = 9g
F35B = Harrier = 7g
F35C = F18 = 7.5g

The point of F35 is sensors and stealth...that there are jets out there that will outperform it shouldn't be a surprise.

Available 'g' is vital in a dogfight; that's why dedicated air-to-air fighters are designed to pull a lot of g. At the inception of F-16 and Typhoon designs the philosophy was that a dogfight would be the end result against a worthy adversary and that manoeuvre potential would ultimately decide the winner; 9g being an uncomfortable yet tolerable limit for sustained fighting.

The philosophy behind F-22 and F-35 is that if they get into a merge something has gone wrong. Both will kill enemy fighters without them knowing what's going on and you don't need 9g to fire a missile. If you did find yourself in a turning fight one would hope that even if the advanced sensors didn't allow you to merge with advantage, modern missile capability would put the fight in your favour.

I would bet that in 99.9% of engagements JSF doesn't pull 7+ g at all.

I'm not sure. While sensors and weapons have increased in capability to allow fighters to kill adversaries BVR better than ever before, I don't think you're ever likely to see suitably ROE to allow you to employ at that range.

I can see a lot of situations where a VID'll be required; and then he's a lot closer, even using an IRST system.

Same question,but not answered..Who is `HE` gonna be...?

5F6B sounds (to me) like a sensible opinion - capabilities generally outperform the ROE restrictions, in which case you can argue that sensors trump all else (the better they are the sooner you can call the other guy a baddie and kill him) or manoeuverability wins out as everyone ends up in a visual range knife fight.

Here's a plan - shoot the politicians and let the airforce draft the ROE... problem solved?

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Out of curiosity how often do you drivers take F 16's and similar to the limit?

Used to depend on how old you were.

My expereince was I could do it just as often as I got older but not for as long. Kind of the reverse of life's other great pleasure.;)

ROE is a fair argument however it depends on the conflict and the rules. The 5th Generation platforms have made huge advances in this regard. After all, sometimes you only have to know who NOT to shoot to distinguish friend from foe. Like I say, it's conflict dependant and won't always apply - so there are a few more tricks up the sleeve ;)

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Originally Posted by ICBM (Post 7210162)

If you did find yourself in a turning fight one would hope that even if the advanced sensors didn't allow you to merge with advantage, modern missile capability would put the fight in your favour.

That's at least what the LM marketing department suggests.
My problem with that is that (at least in a stealthy configuration with only internally carried weapons) F-35 can't employ AIM-9X and is consequently at the moment not planned (budget wise) to be equipped with them.
So once out of the inner AMRAAM envelope you'r in deep s**t vs a HOBS IR missile equipped opponent.

I'm not sure about ASRAAM for the UK version though.

If you can 100% guarantee to kill all the bad guys pre-merge, you only need enough g to position to shot them and turn round once they're all dead. If out-numbered, targeting isn't perfect or Pk/counterneasures leave survivors of the first fox-3s then you have a choice. Blow-through, run and at sometime come back to re-engage. Turn and run, neatly placing the bad guys behind you or stay and fight. Even with off-boresite weapons and versatile aiming, turning at 7g against a 9g+ opponent is a massive disadvantage and is likely to end in tears.

F-15 and F-22 air-to-air pilots are trained to fight at maximum g at corner velocity. Any less and you lose. :eek:

Even LM can't change all the laws of physics.

Just This Once... indeed. Take those bulky red things out and there'd be space for more real weapons. :ok:

Courtney

FWIW: The G requirement and limit doesn't just apply to the dog fight, it also establishes the boundaries of defensive maneuvers you can apply when defeating SAMS and Air to Air missiles via defensive maneuvering ... breaking lock and such.

No further comment.

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Chuckle :rolleyes:

Courtney, LM aren't trying to change the laws of physics and aren't pulling the wool over the eyes of the misinformed either. F-22 is an 'Air Supremacy' fighter; so was the F-15C back in the day and it is no coincidence that the former is its equivalent in 5th Gen terms. Does F-22A require 9g capability? I'd argue not as much which is why she's introduced the ability to point her nose pretty much anywhere so that the HOB mxs can do the rest. JSF is a STRIKE fighter and was not designed as an Air Supremacy fighter at all. The prime design has traded a lot to result in the 3 variants we see today; you want all 3 to be 9g capable? thanks, that'll be $$$$$. You want 8 internal AMRAAM/METEOR per weapon bay? $$$$$ again and you've just increased the size/weight of everything.

So, a few F-22As with a few F-35s are a very good mix for a strike package for a multitude of reasons. You have a predominant AA platform that can do some AG as well as a predominant AG platform that can do AA. SA-wise? Mindblowing!

On balance I believe they've got F-35 mostly right in capability terms. Cost and schedule runaways aside of course but for that you can blame politics at all levels.