Prospects for a light Stealth Fighter

[Scott Kenny]

Sweden has plenty of space to build a 5th Gen fighter equal to the F-35. Let's remind all here that, realistically, and beyond the marketing vocabulary, only a couple of stealth fighter projects will bear capabilities more advanced for the decades to come...

There might be a market for a 5th Gen fighter to the F-35 what the Gripen is to the F-16. Single smaller engine (probably a Snecma M88-3), significantly less range on internal fuel alone, but good STOL capabilities, relatively easy to work on, and fairly cheap to operate. Assuming fairly large weapons bays and mid-sized fuel tanks. Though it may take two M88s or a brand new engine the size of an F110 or so with the sheer size a plane able to carry a Gripen's weapons load internally will end up.

Saab will have to make sure to use zero ITAR items or they will lose sales to the F-35. I mean, the F-35A is right about the same price as a Gripen as-is, so anyone who can get approved for the F-35 will likely buy those instead.

Because the other players in the 5th Gen Fighter markets would be the FC-31, J-20, F-35, and GCAP partners (whether that's one plane or two).

 

[WatcherZero]

I am expecting the Loyal Wingman element to consist of smaller attritable drones for ground attack/recon and a larger wingman escort using one of the same engines as the larger twin engined manned fighter for commonality savings in the air to air role.

 

[TomcatViP]

@Scott Kenny : since Saab has nearly re-invented the Mirage 2000 with their Gripen E (see weight range and dimensions), they are probably ready to give him a thuthful successor.

 

[red admiral]

Saab will have to make sure to use zero ITAR items or they will lose sales to the F-35.

Gripen is nowhere near ITAR free (e.g. the engine) and it doesn't seem to hurt...

 

[timmymagic]

There might be a market for a 5th Gen fighter to the F-35 what the Gripen is to the F-16. Single smaller engine (probably a Snecma M88-3), significantly less range on internal fuel alone, but good STOL capabilities, relatively easy to work on, and fairly cheap to operate. Assuming fairly large weapons bays and mid-sized fuel tanks. Though it may take two M88s or a brand new engine the size of an F110 or so with the sheer size a plane able to carry a Gripen's weapons load internally will end up.

M88 is a dead end development wise, EJ-200 still has significant potential for c30% additional thrust.

Because the other players in the 5th Gen Fighter markets would be the FC-31, J-20, F-35, and GCAP partners (whether that's one plane or two).

And SU-75....although I have my doubts that will ever see the light of day....

Sweden is rather close to potential threats (threat if we're all honest), and so GCAP can deliver potentially what they need in 2 ways.
1. At low fuel weights, take aloft a substantial load of armaments to rapidly counter an opponent's offensive.
2. At high fuel weights, either maintain a long endurance patrol.
Or project arms deep into the enemy's territory.

I think GCAP might be too big for Sweden's tastes but I do wonder if their accession to NATO will change that viewpoint.. It's not just about territorial defence now...they need range for the High North strategy.

 

[Scott Kenny]

M88 is a dead end development wise, EJ-200 still has significant potential for c30% additional thrust.

Wasn't sure about the M88, was mostly going based off of what wasn't a US engine that they could use for a smaller fighter than something the size of an Su27.

Because I fully expect most 6gen fighters to be at least Sukhoi sized. Large internal weapons bays demand it!

And SU-75....although I have my doubts that will ever see the light of day....

As if anyone would trust Russia after 2022... And as if Russia will have any money after the shooting stops.

I think GCAP might be too big for Sweden's tastes but I do wonder if their accession to NATO will change that viewpoint.. It's not just about territorial defence now...they need range for the High North strategy.

Fair point about that.

 

[Scott Kenny]

Going to point out that the Gripen can carry 12klbs weapons load, that's going to equate to large weapons bays. Even if we assume that the GCAP is set up to work like the F-35, where opening days of the conflict are expected to be fought with just the internal weapons and external pylons added for when stealth isn't needed.

I'd expect to see bay capacity for ~6000lbs or so, maybe over 8k in a Gripen replacement. Bay capacity for 4x 2000lb bombs and 2x ASRAAM/AIM-9X, though it will mostly work out to more like 6x ARMAAM/Meteor and 2x ASRAAM/AIM-9X.

 

[A Tentative Fleet Plan]

The original doctrine had the Draken and Viggen dispersed and taking off from roads in the expectation that airfields would be nuclear targets in the case of a Soviet offensive. I don't know what the case is with the Grippen, but it's still a relatively small, light aircraft that could be on distributed deployment. It may be that they consider Tempest/GCAP too big and expensive for this doctrine and are considering whether a single-engine JAS-X is affordable at this point.

The Swedish Bas 90 system (which the Gripen was designed around) involves subsidiary runways on roads dispersed from (but connected by taxiways and close to) already existing airbases, so that they can access higher level maintenance if necessary. If the maintainence resources of main airbases are still accessible, then a large 6th Generation aircraft like GCAP is still viable for Swedish use.

No point having an easily maintainable aircraft if it's completely unusable in the face of modern threats.

 

[A Tentative Fleet Plan]

If there's one lesson from the war in Ukraine, it's that non-stealthy aircraft cannot perform long range strikes against even late Cold War air defences without unacceptable attrition (flying at high altitude puts aircraft in the engagement zones of S-300Ps, S-300Vs and Buks, at low altitude using terrain-following radars, MANPADS cued by passive radars start claiming kills) and that small non-stealthy light fighters (Mig-29 for the Ukrainians, Gripen for Sweden) even if limited air defence taks well within the airspace of your country are still vulnerable to long-range active-radar terminal homing AAMs like the R-37 launched by aircraft operating outside he range of your own air defence systems (and are probably even more vulnerable to penetrating VLO-platforms). I do feel that 4.5 Gen aircraft are a false economy, to penetrate serious defences you need expensive long-ra ge stand-off munitions (and large stocks of them), it's probably cheaper in the long run to use 5th Gen aircraft and JDAM equivalents.

It's not as if the airforces of most WEIRD (Western, Educated, Industrialised, Rich, Developed) countries have enough surplus pilots to fly the theoretical increased numbers of cheaper platforms that could be bought in the first place, so I don't see any loss in building fewer more expensive platforms. The small cheap platforms can be unmanned if they are required.

 

[Forest Green]

People obsessing about GCAP being "too large" don't seem to grasp that it's military utility and affordability are more important than a perception of size = unaffordable.

Unaffordable is a system that cannot be flown in the face of the threat.

There's no such thing as a small functional manned stealth fighter anyway. The requirement to carry fuel and weapons internally instead of hanging them off wings precludes it.

 

[Maro.Kyo]

https://www.secretprojects.co.uk/threads/how-small-can-lo-stealthy-combat-aircraft-designs-get.37600/

https://www.secretprojects.co.uk/threads/design-challenge-lightweight-multirole-fighter-lmf.38539/

Just in case you're not aware, we've had some of these conversation in two separate threads already. We can continue to talk about "light stealth fighter" on these threads and keep this one for GCAP and "Sweden's possible participation in GCAP".

 

[Scott Kenny]

https://www.secretprojects.co.uk/threads/how-small-can-lo-stealthy-combat-aircraft-designs-get.37600/

https://www.secretprojects.co.uk/threads/design-challenge-lightweight-multirole-fighter-lmf.38539/

Just in case you're not aware, we've had some of these conversation in two separate threads already. We can continue to talk about "light stealth fighter" on these threads and keep this one for GCAP and "Sweden's possible participation in GCAP".

Oh, thank you for that!

Off to post some questions in those threads...

 

[WatcherZero]

There's no such thing as a small functional manned stealth fighter anyway. The requirement to carry fuel and weapons internally instead of hanging them off wings precludes it.

Well the F-35 is larger than the Gripen and the F-16 but thats about it, below that you are looking at light fighters with minimal weapons load.

 

[Scott Kenny]

Well the F-35 is larger than the Gripen and the F-16 but thats about it, below that you are looking at light fighters with minimal weapons load.

And these days, I think that the minimum standard load for air patrolling is 4x AAMs, maybe 6x. So that kinda sets everything else. Not a lot of weight, but a fairly long and deep bay.

 

[Forest Green]

Well the F-35 is larger than the Gripen and the F-16 but thats about it, below that you are looking at light fighters with minimal weapons load.

The F-35 weighs 50,000lbs, which is heavier than most Gen 4/4.5 fighters. On physical size, do you only measure length and span, or thickness (top-to-bottom) too? It also forgoes pop-out sidewinders and a little more wing wouldn't go amiss either.

 

[VTOLicious]

There's no such thing as a small functional manned stealth fighter anyway. The requirement to carry fuel and weapons internally instead of hanging them off wings precludes it.

I disagree. 4x AMRAAM and sufficient fuel carried internally in a Gripen sized fighter is absolutely feasible. Check it out here:
https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-512527

 

[paralay]

And these days, I think that the minimum standard load for air patrolling is 4x AAMs, maybe 6x. So that kinda sets everything else. Not a lot of weight, but a fairly long and deep bay.

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

 

[Forest Green]

I disagree. 4x AMRAAM and sufficient fuel carried internally in a Gripen sized fighter is absolutely feasible. Check it out here:
https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-512527

4 MRAAMs is a bit slim for CAP and whilst that looks nice as a drawing, there are a lot of things that look nice on paper that aren't feasible in practice. The internal fuel fraction is also less 30% sans missiles, which is worse than a Typhoon or Rafale, and not many would argue that they have sufficient range on internal fuel alone for all missions.

The ideal stealth air superiority fighter would have 8 missiles (6 MRAAMs, 2 SRAAMs pop-out) and near 1000nm combat radius (2000nm range) on internal fuel. With deeper bays you could even try a 2x4 MRAAM rotary launcher and 2 SRAAMs. The range requirement probably means and internal fuel fraction of nearer 40%, or at least 35% maybe with advanced adaptive cycle engines or something.

 

[riggerrob]

May I remind you that the most likely customers are small second or third world countries who struggle to afford a dozen or two dozen light-weight fighters.

Then they struggle to arfford spare parts, pilot-training, etc.
These tight budgets favor light, single-engined, semi-stealthy fighters that can only carry 2 …. perhaps 4 …. AAM. In practice, they will probably only carry a pair of AAM and fill the rest of their internal weapons bays with spare fuel tanks.
Look at the RCAF mission to intercept Bear bombers intruding into Canadian airspace, especially along Canada’s long Pacific, Arctic and Atlantic coastlines.
The need for lots of range means lots of internal fuel which favours a large delta or diamond wing. Since those planforms do not need horizontal tails, STOL requirements can be met by exotic leading edge slats (see HAL Tejas) blown flaps and the magic of fly-by-wire.
Those silly little radar-grabbing tail surfaces are better left on the ground. Also consider how the next generation of fly-by-wire will eliminate the need for pesky radar-grabbing rudders.

The SAAB Swedish maintenance model of simplified level 1 ground-handling makes a lot of sense especially if these light-weight fighters are going to operate from skeltonized bases in the High Arctic. Even DHL, FedEx, UPS, etc. need more than a day to deliver spare parts to bases at the end of a long supply chain. Interweb connected maintenance advice is all well and good, but some days the only “fix” is a shiny new part and a special wrench.

Thanks for reading the musings of an ex-RCAF airframe technician who quit in disgust after waiting 2 years for CF-18 parts.

 

[Forest Green]

If they struggle to afford 12-24 small non-stealth fighters, then they can't afford stealth fighters.

 

[publiusr]

What surprised me (elsewhere) was the Thud’s low signature due to its intakes. Maybe those…carbon fiber construction and MXene paint would allow a more conventional airframe layout?

https://www.sciencedirect.com/science/article/pii/S2666386422003678

Low Infrared Emissivity and Strong Stealth of Ti-Based MXenes

Advanced scenario-adaptable infrared (IR) stealth materials are crucial for creating localized closed thermal environments. Low emissivity over the broadest possible band is expected, as is superior mechanical deformability. Herein, we report a series ...

www.ncbi.nlm.nih.gov

 

[H_K]

What would be the signature of a small LO fighter with a Silent Hornet-style “Enclosed Weapons Pod” instead of a big weapons bay, and just 2 internal AAMs?

Thinking of something like Boeing’s Model 24F, but without the center bomb bay (or the gun) and a more modern V-tail (YF-23 or Tempest style, instead of separate horizontal & vertical stabilizers).

https://www.secretprojects.co.uk/threads/boeing-fighter-studies-1970s-to-atf.398/post-166555

 

[F-2]

Depending on how light you want to go the Mako fits the bill. Basically a LO F-20

https://www.secretprojects.co.uk/threads/eads-at2000-mako-jet-trainer-concepts.8064/

Not quite an F-35 but if you need cheep your not dealing with a sophisticated IADS. Capable of holding its own against any 4th or 5th gen.

 

[Ainen]

I wonder if small, shallow bay(s) for 2-3 MICA/Derby-sized slim missiles are really so huge; even parasite fighter projects did feature them. The same bay system will fit 4-6 SDBs. More specialist 3.6m class munitions can be developed as needed.

Everything else can fly suspended, if needed. Or be delivered by a CCA/LW.

As a consequence, i really suspect, that provided the will is really here, it's possible to create a ~4 t class(empty) miniature stealth fighter.
No need for M=2, no need for 9G.

Just good stealthy geometry, proper datalinks and full modern cockpit.

 

[F-2]

I wonder if small, shallow bay(s) for 2-3 MICA/Derby-sized slim missiles are really so huge; even parasite fighter projects did feature them. The same bay system will fit 4-6 SDBs. More specialist 3.6m class munitions can be developed as needed.

Everything else can fly suspended, if needed. Or be delivered by a CCA/LW.

As a consequence, i really suspect, that provided the will is really here, it's possible to create a ~4 t class(empty) miniature stealth fighter.
No need for M=2, no need for 9G.

Just good stealthy geometry, proper datalinks and full modern cockpit.

Alternatively, to limit complexity, why not use stealth missiles and ordinance?

They did a mock up of IRIS-T as a stealth missile.

View: https://m.youtube.com/watch?v=-KOV2xM1Afk

 

[Scott Kenny]

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

Sure, but the F-35 is a striker, only carrying 2x AMRAAM as standard. I'm not sure the US has even finished the expansion pack to put 2x AMRAAMs in each bomb rack!

We're talking about making a small plane that is predominantly an air superiority fighter, much like the Gripen.

 

[Scott Kenny]

I am expecting the Loyal Wingman element to consist of smaller attritable drones for ground attack/recon and a larger wingman escort using one of the same engines as the larger twin engined manned fighter for commonality savings in the air to air role.

I disagree with your sizing.

USAF has identified 3 likely Loyal Wingman mission types, and I have added a fourth.

• Recon - This could legitimately be so small that the 6Gen aircraft carries 1-2 internally. I'm picturing something like a MALD with an EO turret, and a second one with ESM systems. General Atomics has recently demonstrated something that size that can recover on the launching fighter.
• EW - This plane I picture being pretty big, basically to replace the Growler. The Growler carries some 7000lbs of jammers, plus another 2000-3000lbs of "need it dead right NOW!" ordnance, in the form of a couple of HARMs, a couple of JASSMs or JDAMs, and a couple of AMRAAMs for self protection.
• Deeper air to air Magazine - This could be a relatively small plane, the Kratos XQ-58 is in roughly the right size class with internal capacity for a pair of AMRAAMs and external capacity for a couple more.
• Penetrating Ground Attack - This would probably use the same airframe as the EW drone, but more or less inverting the jammer to ordnance ratio. 2k-3k worth of jammers, 7000lbs worth of boom. For whatever reason, the USAF is not mentioning this as an option in their design briefs, and that greatly surprises me.

The EW and PGA drones could be the size of the manned 6Gen plane, or could even be bigger. 10klbs internal stowage makes for a very large airframe.

My mental image is that eventually a 6Gen fighter will have potentially a dozen drones around it, so that you can have one or two crew flying the entire Strike Package:

• Manned plane plus 3x Air to Air wingmen and maybe an EW flying top cover,
• 3-4 PGAs and an EW as an entire flight (and possibly multiple flights each of 4x PGAs) making the run into heavily defended airspace,
• a couple of Recons for BDA.

At least early on, it will probably require a back seater to wrangle only one or two drones, but as the AI gets better the number of drones supporting each manned plane will go up pretty dramatically.

I also expect the Loyal Wingman drones to end up a lot like the Century Series, very quickly replaced as the control software gets better and better.

 

[Ainen]

Alternatively, to limit complexity, why not use stealth missiles and ordinance?

They did a mock up of IRIS-T as a stealth missile.

View: https://m.youtube.com/watch?v=-KOV2xM1Afk

As far as i understand, it's pointless (from aircraft' perspective, not their own - stealthy munitions of course are the future).

The problem is reflection of aircraft-pylon-weapon system, which is far greater (and harder to predict) than sum of its parts; mitigation measures are of limited effect here, design really needs to hide payloads inside.

There's airframe masking, though - for example, aircraft is optimized for Lo flight (i.e. for upper hemisphere signature); then weapons suspended and fully covered by airframe will naturally remain hidden.

 

[Scott Kenny]

Oh, right.

Are we going to include Loyal Wingman drone discussion here or is there a separate thread for that already?

 

[H_K]

The problem is reflection of aircraft-pylon-weapon system, which is far greater (and harder to predict) than sum of its parts; mitigation measures are of limited effect here, design really needs to hide payloads inside.

Well how about a flush mounted weapons pod? With the appropriate shaping on the sides & bottom like the Silent Hornet’s EWP but conformally carried under the belly to eliminate unwanted interactions?

A bit like the RA-5C Vigilante’s recon pod maybe, with additional shaping. Or this “Ultra Hornet” what-if:

Post in thread 'Ultra Hornet'
https://www.secretprojects.co.uk/threads/ultra-hornet.14834/post-156144

 

[Scott Kenny]

Well how about a flush mounted weapons pod? With the appropriate shaping on the sides & bottom like the Silent Hornet’s EWP but conformally carried under the belly to eliminate unwanted interactions?

Yes, a conformal weapons pod would be better than a stealthy missile on a pylon.

 

[H_K]

So here’s a rough mash-up of the Boeing Model 24F with the Super Hornet’s weapons pod…

This produces a 9t empty fighter with 5.5t of internal fuel and a single streamlined external load. It is about 500kg lighter empty than an F-16 with CFTs, with 20% more fuel (about as much fuel in fact as an F-16 with CFTs + centerline 300 gallon tank, or an F-16 without CFTs and with 2x 370 gallon tanks).

So it should comfortably outrange & outperform the F-16 even when fully armed with 6 AAMs (or 4 AAMs + 6 SDBs).

 

[TomcatViP]

Pod will affect above estimated range. Here you are just trading the CFT drag for the one from the weapons pod. Essentially there is only a slight improvement, if any, probably cut away by the stealth shaping of the airframe.

 

[H_K]

Here you are just trading the CFT drag for the one from the weapons pod

Stores drag should be in favor of the LO fighter:

F-16: 300 gallon tank + external weapons
Model 24F: 1 Enclosed Weapons Pod

So even if the F-16 with CFTs has slightly less drag « clean », I would expect the LO fighter to have slightly more range overall… unless the LO airframe was very draggy.

 

[TomcatViP]

If you expect...

 

[Scott Kenny]

So here’s a rough mash-up of the Boeing Model 24F with the Super Hornet’s weapons pod…

This produces a 9t empty fighter with 5.5t of internal fuel and a single streamlined external load. It is about 500kg lighter empty than an F-16 with CFTs, with 20% more fuel (about as much fuel in fact as an F-16 with CFTs + centerline 300 gallon tank, or an F-16 without CFTs and with 2x 370 gallon tanks).

So it should comfortably outrange & outperform the F-16 even when fully armed with 6 AAMs (or 4 AAMs + 6 SDBs).

The Boeing EWP only holds 2x AAMs and 6x SDBs. And IIRC the Model 24F holds a pair of Sidewinder-sized missiles in side bays, with a single 2000lb class bomb amidships.

 

[H_K]

The Boeing EWP only holds 2x AAMs and 6x SDBs. And IIRC the Model 24F holds a pair of Sidewinder-sized missiles in side bays, with a single 2000lb class bomb amidships.

Yes I was assuming that the stealth fighter with EWP would retain the side bays for 2x AAMs (hence 4x AAMs total + 6 SDBs) and replace the center bomb bay with an internal fuel tank to achieve useful “F-16 like” range.

 

[Jackonicko]

Gripen is nowhere near ITAR free (e.g. the engine) and it doesn't seem to hurt...

Gripen may be many things, but what it hasn't been is terribly successful on the export market.

 

[red admiral]

Gripen may be many things, but what it hasn't been is terribly successful on the export market.

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?

 

[Scott Kenny]

From the Design Challenge thread:

Might I suggest the Douglas F4D [F5D would be better] as a point of departure?

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.