Prospects for a light Stealth Fighter

[Elysium]

I kind of have to question the wisdom of pursuing a lightweight fighter, considering the major driver of costs nowadays are the electronics and sensors. Putting them on a small plane, might even make it worse, considering the lack of cooling, power and space puts higher demand on those systems for a given amount of capability.
Afaik, the F-35 delays were partly responsible because of the aforementioned issues.

Case in point - the Gripen E is said to cost $85 million, hardly a 'lightweight' in terms of wallet impact, comfortably in the F-35 price range, with a lot less payload.

 

[H_K]

kind of have to question the wisdom of pursuing a lightweight fighter, considering the major driver of costs nowadays are the electronics and sensors.

Would be interesting to see how much money could be saved with slightly downgraded, off-the-shelf components. Avoid buying the most expensive, bleeding edge gear and go with well amortized « current gen » gear. I believe the Israeli and Turkish companies are very good at this.

 

[Scott Kenny]

I kind of have to question the wisdom of pursuing a lightweight fighter, considering the major driver of costs nowadays are the electronics and sensors. Putting them on a small plane, might even make it worse, considering the lack of cooling, power and space puts higher demand on those systems for a given amount of capability.
Afaik, the F-35 delays were partly responsible because of the aforementioned issues.

Case in point - the Gripen E is said to cost $85 million, hardly a 'lightweight' in terms of wallet impact, comfortably in the F-35 price range, with a lot less payload.

Agreed.

Also, I think that the F-35 has about the smallest realistic payload, 6x BVRAAMs in the bays, or 2x BVRAAMs and 2x 2000lb class, or 2x BVRAAMs and 8x SDBs.

You might end up with an aircraft somewhat smaller than an F-35 if you don't have that VTOL Liftfan volume to deal with, but I strongly suspect that the inlet shaping will end up making a space in the center of the airframe that would make a decent 3rd payload bay.

I mean, the Liftfan is 50" in diameter, plus the length of the gearbox and clutch pack (disregarding the drive shaft as that's in the inlet). A 2000lb class weapon is ~155" long and 25" wide which means that it's theoretically possible to make an FB-35 by stretching the forward fuselage until the space where the liftfan was is long enough for 2000lb bombs, probably a 72"-80" stretch. I'd also stretch the side payload bays that amount to carry big standoff weapons internally in those bays, or pack some extra SDB-sized weapons in there along with a "halfraam". The question for the center bay is then depth: do you leave it only deep enough for one 2000lber, or do you make it deep enough to carry 2x or 3x? If you leave the bay one weapon deep you put a fuel tank on top of it and will probably have more range than the basic F-35, especially since this would require larger wings than even the F-35C to shift the center of lift that far forward.

 

[T. A. Gardner]

From the Design Challenge thread:

That's definitely an interesting idea. Already has internal weapons bays (for 51mm FFARs) and is a pretty light aircraft overall. 17,500lbs empty and that's with a 5100lb J57, not a 2450lb F414. The F414 is 90" shorter than the J57, so depending on where exactly the engine needs to end up for CG purposes it may open up some significant length in the weapons bays. Also, the F414 is 35" in diameter, not 39" like the J57, which should open up more internal volume.

You'd be looking at a ~16000lb fighter empty, and could maybe mess around with a wet wing outboard of the existing wing tanks to make them into weapons bays.

I'd think it could be even lighter with modern materials and design technology over what the 50's offered. Plenty of room in the nose for a radar and associated electronics, the wing provides lots of room for fuel and 'stuff.' The original F4D had a phenomenal rate of climb for the day and I could see that copied here and bettered.
You have room for a weapons bay, and if you are updating the cannon armament, there's more room in the wings from that at about mid span.
So, let's say you end up with modern construction, design, and materials a plane empty at around 15,000 lbs. that is carrier capable as well as operates from land bases.

 

[kqcke for you]

Maybe take an YF-120 engine. A little bit bigger than F414 but got mutch more power. And with a modern spin on it we can expect to cut some weight as well as boost power. If done right you got 2x the dry power or that what f414 gives you with afterburner dry.

 

[Desertfox]

If you want a light fighter you don't need internal 2,000lb bomb capability, when SDBs exist... If you can fit 4 SDBs and a couple of AAMs that should be good enough. You can always go external once the threat has been reduced.

 

[Jackonicko]

I agree on limited success. But isn't that because it's "worse", more expensive, and less available than F-16 rather than any ITAR issues? I mean which competitions has it lost or not been entered in due to ITAR?

I thought you were suggesting that had it been ITAR free then success would have been its due...

Whereas, as you suggest, what Saab have faced is marketing an expensive F-16 with superior sensors and MMI but significantly worse kinematic performance

 

[aonestudio]

Air Force Floats Light Stealth Fighter Concept As Its Heavy Fighter Program May Be In Jeopardy

The Air Force’s top officer touted the concept as a path to develop a less expensive and more flexible fighter design, which is odd considering a top priority was the service’s NGAD heavy fighter. The Air Force’s top officer touted the concept as a path to develop a less expensive and more...

www.twz.com

 

[Scott Kenny]

Air Force Floats Light Stealth Fighter Concept As Its Heavy Fighter Program May Be In Jeopardy

The Air Force’s top officer touted the concept as a path to develop a less expensive and more flexible fighter design, which is odd considering a top priority was the service’s NGAD heavy fighter. The Air Force’s top officer touted the concept as a path to develop a less expensive and more...

www.twz.com

Yeah, USAF doesn't know what it wants.

I mean, it wants/needs a long range aircraft to handle the Pacific. This is a major internal paradigm shift, because up till now the focus has always been Europe. F15s and F22s, and even F35s, are all sized around a European conflict.

And I think a lot of this is the realization of how big and therefore expensive a Pacific-sized aircraft will be. We're talking something that is on the order of 110,000lbs MTOW, because you need some 46,000lbs of fuel to cover the distance demanded.

While it's not wrong to talk about wanting an F16 to go with the F15, or an F35 to go with an F22, I don't see how exactly a lightweight fighter fits into the NGAD mold. If you need affordable mass, that's what the CCAs are for.

 

[totoro]

That's why US is also leaning so heavily into additional bases.
First a bunch of on the Philippines.
Then a further ring - Cocoa/Timor/east guinea/Papua/Palau (this ring would mostly be support planes i imagine)
Then i am sure there will be a bunch more bases on Japanese territory, eventually.

 

[paralay]

A two-seat fighter with a single engine may well replace a twin-engine one. The range will be even slightly longer, F-16 - 1190 km, F-15 - 1045 km. The problem is to place two JASSM or AIM-174 missiles in the weapons bay

 

[Bounce]

Wasn't there a rumor for something based on the F-35, longer fuselage with a cranked arrow planform.

 

[VTOLicious]

Just a reminder: The F-35(A) isn't a lightweight fighter...

• Empty weight: 29,300 lb (13,290 kg)
• Max takeoff weight: 65,918 lb (29,900 kg)

 

[timmymagic]

Look at the list of weapons supplied to Germany along with the F-35, there are only three medium-range missiles per plane!

To be fair to the German's they have other stocks of Amraam to lean on, plus by the time F-35A gets delivered Meteor 'should' be integrated and operational on F-35, which is another stockpile for them to access.

 

[Jackonicko]

I don't see how exactly a lightweight fighter fits into the NGAD mold. If you need affordable mass, that's what the CCAs are for.

1) A lightweight fighter could represent 'low hanging fruit' - something achievable, where the CCAs are increasingly looking hard to achieve, and likely to be very expensive for the limited capability offered.
2) The lightweight manned aircraft within the NGAD 'system of systems' could be more exportable than the full-up NGAD fighter.
3) It's EXACTLY the F-16 replacement outlined by CQ Brown a couple of years ago.

Very similar reasons underpin the UK's ambitions to have a second manned platform within its FCAS 'system of systems'.

 

[Jackonicko]

A two-seat fighter with a single engine may well replace a twin-engine one. The range will be even slightly longer, F-16 - 1190 km, F-15 - 1045 km. The problem is to place two JASSM or AIM-174 missiles in the weapons bay

Hard to see a need for a new fighter to be a two-seater...

 

[Jackonicko]

If you want a light fighter you don't need internal 2,000lb bomb capability, when SDBs exist... If you can fit 4 SDBs and a couple of AAMs that should be good enough. You can always go external once the threat has been reduced.

You probably need something with more stand off reach and a much bigger warhead than an SDB. Not many Taliban or Daesh targets were hardened - but lots of Chinese and Russian target sets will be.

 

[T. A. Gardner]

It's a hard sell to get an air force, any air force, to buy a "lightweight" fighter. Even before WW 2 started, lightweight fighters were not popular. Take the Caudron C 700 series:

or the XP 77

Really doesn't matter what country it is, these planes are never popular with air forces or buyers for air forces.

 

[Jackonicko]

It's a hard sell to get an air force, any air force, to buy a "lightweight" fighter.

They sold a lot of F-16s, and that's the kind of light we're talking... and in fact because of LO it may be a fair bit bigger than that.

 

[Desertfox]

You probably need something with more stand off reach and a much bigger warhead than an SDB. Not many Taliban or Daesh targets were hardened - but lots of Chinese and Russian target sets will be.

Thats not the target set for a light fighter...

 

[paralay]

Hard to see a need for a new fighter to be a two-seater...

It is not necessary, but it is useful to have such an opportunity

 

[Ainen]

They sold a lot of F-16s, and that's the kind of light we're talking... and in fact because of LO it may be a fair bit bigger than that.

How LO makes anything bigger?
LO from this perspective is just shaping.
And it was totally possible to fit normal (not optimized for internal carriage, like CUDA or Falcon series) a2a missiles inside even airborne parasite fighters in 1970s.

 

[Jackonicko]

Precisely because LO implies internal carriage of fuel and weapons.

 

[Ainen]

Precisely because LO implies internal carriage of fuel and weapons.

Neither is particularly troublesome until you want to fly far unrefueled, or carry something big and bulky.

A2a missiles (especially purpose-developed, I heard that country like US is capable of that) and compact PGMs will fit perfectly fine, in adequate numbers.

 

[Jackonicko]

Thats not the target set for a light fighter...

It's the target set for anything that wants to be relevant.

 

[Jackonicko]

Neither is particularly troublesome until you want to fly far unrefueled, or carry something big and bulky.

A2a missiles (especially purpose-developed, I heard that country like US is capable of that) and compact PGMs will fit perfectly fine, in adequate numbers.

That was true when you only wanted to carry AAMs in very limited numbers and when your targets were Toyota pick ups, and when you were operating in benign enough conditions to not need a decent stand off capability.

 

[Foo Fighter]

Personally squeaking, any two seater will have an advantage in reduced workload, something that can only become more important going forwards.

 

[T. A. Gardner]

They sold a lot of F-16s, and that's the kind of light we're talking... and in fact because of LO it may be a fair bit bigger than that.

The 16 started out as lightweight and gained in the design phase. Lockheed / General Dynamics learned from the F-104 that a true lightweight fighter was going to be a non-starter with the USAF.

 

[Ainen]

That was true when you only wanted to carry AAMs in very limited numbers and when your targets were Toyota pick ups, and when you were operating in benign enough conditions to not need a decent stand off capability.

Cuda/falcon-sized missile with a triple pulse engine(see derby-ER) will probably reach normal modern bvr ranges without much trouble. Probably at the expense of a warhead, sure, but this is a manageable sacrifice.
Same form-factor allows SDB II/Spear-3, and even micro cruise missiles. Alternatively, full-sized BVR missile(aim-260?) will fit in place of two; same form-factor allows to fit 250 kg-class long/narrow munition like KAB-250.
Except for CUDA(which is a concept), everything else mentioned is mainline, state of the art, 5th gen weapons.

Following the same 1970s parasite pattern, space for 4 such munitions isn't a big problem. And 4 missiles(or 4 jdam bombs) is normal weapon load of modern f-35.
Granted, larger ones, but numbers are not a problem.

And sdb with a direct hit is good for >90% battlefield targets. For something larger, no one takes away already available f-35s.

 

[VTOLicious]

It's the target set for anything that wants to be relevant.

But than it's not a light fighter. I would call this medium, something like KF-21. And even KF-21's IWBs are rather tight. They definitely wouldn't fit 2000lb JADMs.

And that's the point: Customer requirements determine what's relevant.

 

[Ozair]

Personally squeaking, any two seater will have an advantage in reduced workload, something that can only become more important going forwards.

That is completely opposite to the way fighter aircraft are advancing. Single seat is the only option on almost all 5th gen bar a two seater J-20 and dominates production for most 4th gen.

Looking forward USAF has said an F-22 can operate up to 6 CCAs without overburdening the pilot and avionics and systems are only going to get easier to use. Additionally most new platforms will have significant AI integration reducing workload even further.

 

[Scott Kenny]

How LO makes anything bigger?
LO from this perspective is just shaping.
And it was totally possible to fit normal (not optimized for internal carriage, like CUDA or Falcon series) a2a missiles inside even airborne parasite fighters in 1970s.

LO means carrying weapons and fuel internally for whatever your design weapons load is.

Those airborne parasite fighters were NOT carrying weapons internally. They were hanging weapons on wingtips and under the wings.

 

[red admiral]

Those airborne parasite fighters were NOT carrying weapons internally. They were hanging weapons on wingtips and under the wings.

Some of the microfighter concepts had conceptual tube launched missiles as armament were buried in the airframe. I suppose you could bury some APKWS pods in the airframe today but its not really the same as an AMRAAM etc.

 

[Ainen]

LO means carrying weapons and fuel internally for whatever your design weapons load is.

Those airborne parasite fighters were NOT carrying weapons internally. They were hanging weapons on wingtips and under the wings.

Pay attention to wing roots.
Thus no, it isn't that big of a deal to add space for something like 3-6 SDBs when they're well folded, especially if we skip the gun.

But yes, even a very light fighter is still capable of carrying oversized payloads (which won't fit into f-35) when it needs to.

 

[sublight_]

Would it be completely implausible to have a large, conformal, stealthy fuel tank on the bottom of the aitframe so it can do long range missions while remaining stealthy?

 

[Ozair]

Would it be completely implausible to have a large, conformal, stealthy fuel tank on the bottom of the aitframe so it can do long range missions while remaining stealthy?

Like most of the stuff proposed in this discussion anything is possible, it just becomes an exercise in money and requirements and what is the priority, need to have versus nice to have. Additionally in aircraft design everything is a trade off, if you put weapons in wing roots for instance then there are structural considerations and exhaust issues from missiles. Similarly putting a fuel tank on the bottom of the airframe may come with structural, plumbing and LO considerations etc.

What we know with lightweight fighters is the more you add the less performant the aircraft typically becomes due to weight and drag. Then consider the cooling required for advanced sensors, radar and EW equipment.

Not to speak ill of the dead but Pierre Sprey was a proponent of the lightweight low system aircraft, to the point the F-16 would have remained essentially a day only WVR fighter. I don't think anyone can rationally think that remains a good idea...

 

[Scott Kenny]

Pay attention to wing roots.
Thus no, it isn't that big of a deal to add space for something like 3-6 SDBs when they're well folded, especially if we skip the gun.

But yes, even a very light fighter is still capable of carrying oversized payloads (which won't fit into f-35) when it needs to.

It's not the 6x SDBs you need space for. It's an NSM or Harpoon/SLAM, etc.

 

[Ainen]

It's not the 6x SDBs you need space for. It's an NSM or Harpoon/SLAM, etc.

Nsm, slam and harpoon don't fit inside even the f-35(admittedly, two due to a lack of folding, but the argument still stands), despite all 3 being specifically stand off weapons with air breathing weapon, allowing long range launch below the horizon.
They just don't need stealthy carriage that much, unless you're doing deep penetration... which isn't a light fighter mission in the first place.

The question here thus is a rather simple one: if the goal is to set the bar too high for the sake of not doing something, it's simple, just make 2 2000lbs internal your basic requirement again - and we'll get the same result, again.

But it doesn't mean that a relevant and capable LO fighter can't be done even in a super light (down to 5t empty or even lower, i.e. f-5) weight class; advances in precision and flight control make it viable; China's advantages in manufacturing and, apparently, aerospace hardware:software coupling make it attractive offset.
It's us deciding to add impossible requirements (in this case - impossible for even a 15t empty f-35) that make it doubtful.

 

[kqcke for you]

Nsm, slam and harpoon don't fit inside even the f-35(admittedly, two due to a lack of folding, but the argument still stands),

But JSM can which has most of the capabilitys that they offer

 

[Ozair]

But JSM can which has most of the capabilitys that they offer

Also hard to fault the aircraft for missiles built before it was even designed.

5th gen platforms need 5th gen weapons which are only now just arriving.