Design Challenge: Lightweight Multirole Fighter (LMF)

[Scott Kenny]

I absolutely agree that electronic hardware and software is a big cost driver in a state of the art combat jet.
But it would be very interesting to see a reliable reference. Is it publicly known how the cost of airframe, engine, avionics, etc. of the F-35(A) is distributed?

While I haven't seen a breakdown, that doesn't mean someone on the forum hasn't found such a thing.

I've been comparing cost of the Gripen to F-16 block 50/52.

 

[H_K]

I absolutely agree that electronic hardware and software is a big cost driver in a state of the art combat jet.
But it would be very interesting to see a reliable reference. Is it publicly known how the cost of airframe, engine, avionics, etc. of the F-35(A) is distributed?

For the Rafale back in the early 2000s the cost breakdown was roughly:

Airframe (Dassault): €25M 50%
Electronics (Thales): €10M 20%
Engine (Safran): €8M 15%
Other systems: €8M 15%
Total: ~€50M excl. VAT (flyaway)

 

[Scott Kenny]

For the Rafale back in the early 2000s the cost breakdown was roughly:

Airframe (Dassault): €25M 50%
Electronics (Thales): €10M 20%
Engine (Safran): €8M 15%
Other systems: €8M 15%
Total: ~€50M excl. VAT (flyaway)

Thank you!

Huh, that's not quite what I had expected, was expecting the electronics to be more than that, even for the Rafale.

I'd expect the F-35's electronics costs to be equal to airframe costs, due to having more electronics installed and having a relatively cheaper airframe (large production run).

 

[VTOLicious]

Thank you!

Huh, that's not quite what I had expected, was expecting the electronics to be more than that, even for the Rafale.

I'd expect the F-35's electronics costs to be equal to airframe costs, due to having more electronics installed and having a relatively cheaper airframe (large production run).

According to this figure around 15% is propulsion, 35% is for systems and the remaining 50% is for the airframe (CTOL)
But we should consider that "systems" is more than just the mission systems, like the radar, DAS, EOTS, etc.

Source: http://systemarchitect.mit.edu/docs/boas08.pdf

 

[Scott Kenny]

According to this figure around 15% is propulsion, 35% is for systems and the remaining 50% is for the airframe (CTOL)
But we should consider that "systems" is more than just the mission systems, like the radar, DAS, EOTS, etc.
View attachment 708737
Source: http://systemarchitect.mit.edu/docs/boas08.pdf

That may also depend on where they're putting the flight control actuators, etc. Mentally, I file those under "Airframe" not "Systems" but the Rafale example obviously puts those in the "other systems" file.

 

[VTOLicious]

If one compares FAR-21 to KF-21, assuming the fraction "systems" is equal, significant cost saving is possible on propulsion (-1 engine) and on airframe (less material).

https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-517275

 

[H_K]

@VTOLicious Your FAR-21 seems about midway between the 5.7-ton empty Boeing MRF-24X and 9-ton empty MRF-24F designs posted earlier upthread, so I attempted a side-by-side size comparison.

My takeaway is the wing area seems a tad low (similar to the MRF-24X despite much heavier weight), and the overall fuselage size is almost as big as the 9 ton MRF-24F... which makes me wonder if the 7.6 ton empty weight estimate is too optimistic? Once you adjust that up and start increasing the wing size to offset the weight increase, you might end in a weight spiral that lands you somewhere very close to the MRF-24F in terms of overall size & weight.

In other words, is it realistic to make a stealth fighter much smaller than the MRF-24F? What would need to be cut? (Obviously the MRF-24X suggests a pathway, but not clear how that design achieves such a small size aside from possibly some very optimistic assumptions about technology progress in materials and engine size...

[EDIT: added the 9.7-ton X2 Shinshin to the comparison below]

 

[VTOLicious]

@VTOLicious Your FAR-21 seems about midway between the 5.7-ton empty Boeing MRF-24X and 9-ton empty MRF-24F designs posted earlier upthread, so I attempted a side-by-side size comparison.

My takeaway is the wing area seems a tad low (similar to the MRF-24X despite much heavier weight), and the overall fuselage size is almost as big as the 9 ton MRF-24F... which makes me wonder if the 7.6 ton empty weight estimate is too optimistic? Once you adjust that up and start increasing the wing size to offset the weight increase, you might end in a weight spiral that lands you somewhere very close to the MRF-24F in terms of overall size & weight.

In other words, is it realistic to make a stealth fighter much smaller than the MRF-24F? What would need to be cut? (Obviously the MRF-24X suggests a pathway, but not clear how that design achieves such a small size aside from possibly some very optimistic assumptions about technology progress in materials and engine size...

The wing area of FAR-21 is equal to the F-16 (about 28 m²). Consequently it should be sufficient (F-16 is 8,6 ton empty)

 

[H_K]

The wing area of FAR-21 is equal to the F-16 (about 28 m²).

I get the idea, but we don’t know how the lift coefficients compare… the F-16 has a different fuselage/wing planform, more wing-span for high lift devices etc.

How do the FAR-21 wing area and wing loading compare to F-35, X2 Shinshin and others that are more comparable?

(Edit: I added the X2 Shinshin to the comparison... its wing size is about the same as your FAR-21, so perhaps the wing size is fine based on that benchmark)

 

[carvalho2008]

Well, I don't know the author, but I thought of this 5th generation project with the same or similar electronic package as the Gripen NG

 

[carvalho2008]

If one compares FAR-21 to KF-21, assuming the fraction "systems" is equal, significant cost saving is possible on propulsion (-1 engine) and on airframe (less material).
View attachment 708738
https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-517275

Don't get mad at me....but that's what I was trying to say....entirely dorsal engine, the entire air intake duct space becomes new fuel and weapons bays.

The front air intakes become missile bays.

Install auxiliary air grilles, automatic and controlled by the FBW, extending from the belly to the back.

The model will lose some things, but will gain a lot in combat load in stealth bay mode and range and autonomy.

If you can achieve this equation, then you will have a small model but with the loads and autonomy of large fighters...

 

[Scott Kenny]

Don't get mad at me....but that's what I was trying to say....entirely dorsal engine, the entire air intake duct space becomes new fuel and weapons bays.

The front air intakes become missile bays.

Install auxiliary air grilles, automatic and controlled by the FBW, extending from the belly to the back.

The model will lose some things, but will gain a lot in combat load in stealth bay mode and range and autonomy.

If you can achieve this equation, then you will have a small model but with the loads and autonomy of large fighters...

It's going to take some very careful shaping to keep the dorsal intake(s) fed during high alpha maneuvers. I don't believe that you can add belly vents without severely compromising the stealth detailing.

 

[carvalho2008]

It's going to take some very careful shaping to keep the dorsal intake(s) fed during high alpha maneuvers. I don't believe that you can add belly vents without severely compromising the stealth detailing.

The grille making up the air ducts opens like gills or shutters only when the plane is in a steep attitude. They are closed when in straight flight or small curves.

This should work well because when the plane is turning very hard with the nose tilted, the belly is exposed to the strongest direction of the airflow, thus collecting the necessary supplementary airflow.

Another important point of attention is that this type of maneuver means that the plane is already in a dogfight and no longer in BVR combat.

 

[VTOLicious]

I get the idea, but we don’t know how the lift coefficients compare… the F-16 has a different fuselage/wing planform, more wing-span for high lift devices etc.

How do the FAR-21 wing area and wing loading compare to F-35, X2 Shinshin and others that are more comparable?

(Edit: I added the X2 Shinshin to the comparison... its wing size is about the same as your FAR-21, so perhaps the wing size is fine based on that benchmark)

The wing loading is in the region of 500 kg/m². That's a reasonable number.

 

[VTOLicious]

One cannot simply ignore the brains of thousands of aerospace engineers that came to the conclusion that dorsal intakes are unsuitable for supersonic fighters with certain maneuverability requirements.
I would guess every major combat aircraft manufacturer has had a look at this intake configuration at least once. For instance...

 

[VTOLicious]

Don't get mad at me....but that's what I was trying to say....entirely dorsal engine, the entire air intake duct space becomes new fuel and weapons bays.

The front air intakes become missile bays.

Install auxiliary air grilles, automatic and controlled by the FBW, extending from the belly to the back.

The model will lose some things, but will gain a lot in combat load in stealth bay mode and range and autonomy.

If you can achieve this equation, then you will have a small model but with the loads and autonomy of large fighters...

I get the idea and appreciate your effort.
However, see my post above... I agree to disagree.

 

[carvalho2008]

One cannot simply ignore the brains of thousands of aerospace engineers that came to the conclusion that dorsal intakes are unsuitable for supersonic fighters with certain maneuverability requirements.
I would guess every major combat aircraft manufacturer has had a look at this intake configuration at least once. For instance...
View attachment 708832

 

[carvalho2008]

 

[carvalho2008]

 

[carvalho2008]

 

[carvalho2008]

 

[carvalho2008]

But with the engine 100% external and dorsal, above the airframe and hidden by the side empennages

The Fuselage below continues in the longitudinal and free direction, giving space for a second bay, or expanding the original, or even more electronics, in addition to + 2 lateral conformal bays where the original air intakes were in the frontal section and cheeks of the hunting.

These changes can reduce final speed and perhaps some maneuverability, but increase internal load by 50% to 70%. The plane will absurdly reduce the need for external loads that compromise invisibility.

An exchange between the external engine Versus external load....the engine would not be more visible than any tanks or underwing missiles.

 

[red admiral]

One cannot simply ignore the brains of thousands of aerospace engineers that came to the conclusion that dorsal intakes are unsuitable for supersonic fighters with certain maneuverability requirements.

I think it's more just "higher risk" rather than "unsuitable". And for previous projects then generally there's no strong disadvantage to a different intake location so why take the higher risk?

 

[carvalho2008]

By moving the wings back to rebalance the CG and adding canards, you will have more wing surface without changing the wingspan.

The plane still has the length and wingspan you designed, but the concept actually changes from a 100% BVR dogfighter to something like an A-7 stealth and BVR... more versatile and resistant to dirty runways and will probably be improved by canards , takeoff distances.

Its project is smaller than the Turkish Kizileuma UCAV. it looked beautiful, but in a low-cost appeal like this UCAV, see that it did not exceed the range and load of its requirements...that is why in fact there seems to be a need to move the engine to increase range and load in mode stealth. See that the Ucav doesn't even have pilot facilities and yet, there was a lack of space.

It is a niche that I believe will greatly increase concepts like this UCAV. Because it has Canards and almost 2 meters more wingspan, it is sized for STOL requirements, which is once again important for this type of product proposal. I just placed the engine above and it ended up looking very similar.

 

[VTOLicious]

I think it's more just "higher risk" rather than "unsuitable". And for previous projects then generally there's no strong disadvantage to a different intake location so why take the higher risk?

I chose "unsuitable" because there are indeed applications for which it is considered suitable and was implemented indeed.

 

[VTOLicious]

To explore another option of "beast mode" I've created a fuel tank for the installation in the main weapons bay. It has a capacity of 450 gal / 1700 l (1360 kg) and a weight of 1500 kg (I accounted ~10% for the structure).

With this tank installed the internal fuel capacity is increased to 5700 l (4560 kg). That is 42,5% in addition to the normal capacity of 4000 l (3200 kg).
With the weapons load depicted the takeoff weight is 14702 kg, or 92% of the maximum.

 

[kqcke for you]

Could one make a hybrid of the Air intakes right now and dorsal? Maybe take the Volume we get now and Splitt it between the two. 30% each of the 2 (total 60%) we have right now (so they can shrink to a size we're they only get 60% of the total Volume of Air we get in) and 40% for the dorsal. Could be a solution for the dorsal debate but im no expert for this

 

[GTX]

What's the point of this so-called Lightweight Multirole Fighter?

 

[VTOLicious]

What's the point of this so-called Lightweight Multirole Fighter?

In short: FAR-21 is intended to provide meaningful capability at reduced cost and the basis for a "loyal wingman" version.

Technology wise I think of KF-21, which uses the same engine as well...
https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-624360
https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-517275

 

[GTX]

In short: FAR-21 is intended to provide meaningful capability at reduced cost and the basis for a "loyal wingman" version.

As stated already, something like the FA-50 is going for ~US$40-50M a copy. A Saab Gripen E/F is reportedly ~US$85M a copy. Therefore, I question what sort of capability one is considering here. Talk of advanced sensors and low observability capabilities mean that one is going to be looking at something equal to or greater in cost than even these which undermines the "reduced cost" part.

If you say that something smaller is considered with reduced weapons payload it soon reaches a point where one would have to say "why bother"? These days, no-one realistically is going to want the manned modern equivalent of a F-5 or, dare I say, a Folland Gnat/HAL Ajeet, which is where this seems to be aiming for.

The only way to get some sort of acceptable outcome with cost vs capability is to do some radical change which removes a major cost driver, hence why I suggest the UCAS approach since it removes major costs/weights such as the crew and associated items such as ejection seat, life support, cockpit displays etc. Moreover, as a uninhabited platform, there is arguably no need for flights other than operational ones which would have the effect of being able to reduce airframe life etc (and thus further on weight/cost) - e.g. design for 1000hrs (or less) rather than 8000+hrs.

Simply put, designing something like a modern manned fighter is going to have to be a compromise/trade-off between capability, cost and weight. Any mythical low cost, low weight platform which also has high capability is simply a unicorn. If you say that capability can be reduced you have to wonder if your crews would welcome going into battle in an inferior product. If you say that capability is paramount, you rapidly get back to high cost.

 

[red admiral]

Those are all relevant points, but this is just a concept in some level,of engineering detail. Its not actually being proposed to be built by a real company. Many real companies (and other organisations lile RAND) do conceptual design of a range of options in order to understand the engineering trade offs, and provide inputs to operational and cost analysis to understand the cost-effectiveness.

I would also suspect that there is only a small market for a "5th gen F-5" or "5th gen smaller Gripen" but this tries to explore what such a concept could be like. It feels like a logical place to explore as there is always interest in what a "cheaper" option would be like. It's not necessarily a good option but is different than say a concept going head to head with F-35A or NGAD.

Comparison with the existing uncrewed "loyal wingman" / "fighter" UCAS (say MQ-28) is difficult as this is significantly larger and significantly more capable with much greater performance and payload (weapons and sensors). Is this the right balance? Who knows? Generating these concepts for analyses helps to understand this.

 

[VTOLicious]

As stated already, something like the FA-50 is going for ~US$40-50M a copy. A Saab Gripen E/F is reportedly ~US$85M a copy. Therefore, I question what sort of capability one is considering here. Talk of advanced sensors and low observability capabilities mean that one is going to be looking at something equal to or greater in cost than even these which undermines the "reduced cost" part.

If you say that something smaller is considered with reduced weapons payload it soon reaches a point where one would have to say "why bother"? These days, no-one realistically is going to want the manned modern equivalent of a F-5 or, dare I say, a Folland Gnat/HAL Ajeet, which is where this seems to be aiming for.

The only way to get some sort of acceptable outcome with cost vs capability is to do some radical change which removes a major cost driver, hence why I suggest the UCAS approach since it removes major costs/weights such as the crew and associated items such as ejection seat, life support, cockpit displays etc. Moreover, as a uninhabited platform, there is arguably no need for flights other than operational ones which would have the effect of being able to reduce airframe life etc (and thus further on weight/cost) - e.g. design for 1000hrs (or less) rather than 8000+hrs.

Simply put, designing something like a modern manned fighter is going to have to be a compromise/trade-off between capability, cost and weight. Any mythical low cost, low weight platform which also has high capability is simply a unicorn. If you say that capability can be reduced you have to wonder if your crews would welcome going into battle in an inferior product. If you say that capability is paramount, you rapidly get back to high cost.

This conceptual design shows that a 5th generation stealth fighter in the weight class of a Gripen is indeed feasible from a technical point of view. It provides a resonable weapons and fuel load and based on its physical parameters resonable performance can be expected as well. You may have noticed that I chose a rather conservative design approach to avoid discussion on credibility (e.g. the much discussed dorsal air intake).

However, estimations on combat aircraft flyaway cost are not in my area of expertise. The only thing I said in this regard is that in direct comparison to KF-21 cost is saved on propulsion (-1 engine) and on airframe (less material). That's matter of fact.

Anyhow, luckily this thread is titled Design Challenge and not Sales Challenge

 

[carvalho2008]

Those are all relevant points, but this is just a concept in some level,of engineering detail. Its not actually being proposed to be built by a real company. Many real companies (and other organisations lile RAND) do conceptual design of a range of options in order to understand the engineering trade offs, and provide inputs to operational and cost analysis to understand the cost-effectiveness.

I would also suspect that there is only a small market for a "5th gen F-5" or "5th gen smaller Gripen" but this tries to explore what such a concept could be like. It feels like a logical place to explore as there is always interest in what a "cheaper" option would be like. It's not necessarily a good option but is different than say a concept going head to head with F-35A or NGAD.

Comparison with the existing uncrewed "loyal wingman" / "fighter" UCAS (say MQ-28) is difficult as this is significantly larger and significantly more capable with much greater performance and payload (weapons and sensors). Is this the right balance? Who knows? Generating these concepts for analyses helps to understand this.

Master Red Admiral,

I'm a fan of the Folland Gnat, I need to be faithful to this in a test of a 5th fighter. generation, although I sought to add or force some changes in the general approach of the proposed design.

Fighters grew a lot in weight and size and this was related to their range and the need to have many weapons in view of the kill rating of their time. Nowadays, smart weapons have an absurd NEZ hit rate, much higher than 20 years ago. With a smaller amount of smart bombs or missiles, you can achieve a good hit rate. A classic 5th generation F-35 fighter is disadvantageously limited by its internal weapons bay. If you carry weapons and fuel under the wings, you lose all your stealth investment. In addition to this, came the Loyal Wingman (not yet tested in practice). This can all vary greatly depending on the multitude of different missions in combat. It is in this aspect that my suggestions focus on leveraging reach as a top priority in a small project, as reaching the opponent without being reached is extremely strategic. By expanding the internal bays, in addition to the range, you can exchange weapons or the best balance of the weapons/fuel mix for each mission. Integrating canards add wing surface and short takeoffs. As the project in question is smaller than kizileuma itself and this in turn has a promise of on-board employment, it also results in the addition of yet another feature that does not exist in the other projects.

This is no small feat.

 

[GTX]

However, estimations on combat aircraft flyaway cost are not in my area of expertise. The only thing I said in this regard is that in direct comparison to KF-21 cost is saved on propulsion (-1 engine) and on airframe (less material). That's matter of fact.

My response was based upon your own stated purpose of the exercise being "...intended to provide meaningful capability at reduced cost...", What I am saying in response therefore is that to provide any sort of meaningful capability is at odds with reduced cost. One or the other suffers.

Moreover, if using the KF-21 as a point of comparison and using the engine as a point of differentiation, note that the GE F414 engine as used in that runs at about US$3 - 4M a copy. Even if one factors in reduced airframe costs related to this and maybe even allowing for a doubling of the savings to around US$6 - 8M then you would still be looking at a fighter with reduced capability that is still going to cost around US$60M (based upon KF-21 roles of being ~US$65M each (probably fanciful IMHO unless there was a significant production run or else even further compromises in capability under the skin). Therefore, I again state that this is a unicorn.

 

[Scott Kenny]

My response was based upon your own stated purpose of the exercise being "...intended to provide meaningful capability at reduced cost...", What I am saying in response therefore is that to provide any sort of meaningful capability is at odds with reduced cost. One or the other suffers.

Moreover, if using the KF-21 as a point of comparison and using the engine as a point of differentiation, note that the GE F414 engine as used in that runs at about US$3 - 4M a copy. Even if one factors in reduced airframe costs related to this and maybe even allowing for a doubling of the savings to around US$6 - 8M then you would still be looking at a fighter with reduced capability that is still going to cost around US$60M (based upon KF-21 roles of being ~US$65M each (probably fanciful IMHO unless there was a significant production run or else even further compromises in capability under the skin). Therefore, I again state that this is a unicorn.

Well, yeah.

It's likely not enough cheaper than a KF-21 or even F-35 to really make it viable in the way that the F5s were.

But it gives a solid point for anyone trying to argue for a cheap 5th gen fighter. "Sorry, the minimum entry cost for a 5gen fighter is on the order of $60mil per plane, and it barely gets you the capacity to do anything. Going up to the F-35A does cost 1/3 more but is vastly better in overall performance."

But as a Loyal Wingman, this has some serious pros to it. Not sure how much cheaper and lighter ditching the entire cockpit and all those pilot support systems would make the airframe, but I'd believe saving about 1/3 of the "other systems" costs.

==========================

Personally, I think that making the weapons bay about 9" wider would help the capacity greatly without completely screwing the design. This would enable carrying a single 2000lb bomb plus two AAMs internally for a heavy strike, or packing 8xSDB plus 2xAAMs for a more typical strike mission.

 

[red admiral]

There's a lot of low fidelity US cost forecasting models that use $/lb for unit costs. KF-21 seems a pretty good near neighbour so I'd roughly expect similar $/lb for the airframe, and you've got ~half the engine costs. Looking at the masses then this would put this FAR-21 down at 65-70% of the UPC of KF-21 which is a fair saving. Sure its not as "capable" but it is lower cost. So if KF-21 is really $65mUSD upc then this would be down at around $45mUSD for equal other assumptions (like relatively small production run, low labour costs etc.) - but it could change massively with different programme assumptions.

But even compared to KF-21 there are further reductions possible e.g. with the wider adoption of OTS avionics, and generally trying to minimise the avionics as much as possible. I would suggest that trying to work around an OTS radar is at least as important as trying to work around the OTS engine. Maybe one of the Elta ones makes most sense for this "non-aligned" low cost fighter. Have you thought much about other potential avionics? Or even just a total mass for them?

 

[Scott Kenny]

There's a lot of low fidelity US cost forecasting models that use $/lb for unit costs.

How wide are the error bars on those models?

KF-21 seems a pretty good near neighbour so I'd roughly expect similar $/lb for the airframe, and you've got ~half the engine costs. Looking at the masses then this would put this FAR-21 down at 65-70% of the UPC of KF-21 which is a fair saving. Sure its not as "capable" but it is lower cost. So if KF-21 is really $65mUSD upc then this would be down at around $45mUSD for equal other assumptions (like relatively small production run, low labour costs etc.) - but it could change massively with different programme assumptions.

But even compared to KF-21 there are further reductions possible e.g. with the wider adoption of OTS avionics, and generally trying to minimise the avionics as much as possible. I would suggest that trying to work around an OTS radar is at least as important as trying to work around the OTS engine. Maybe one of the Elta ones makes most sense for this "non-aligned" low cost fighter. Have you thought much about other potential avionics? Or even just a total mass for them?

$45mil is close to the cost of Gripen C/D, isn't it?

 

[BLACK_MAMBA]

But with the engine 100% external and dorsal, above the airframe and hidden by the side empennages

The Fuselage below continues in the longitudinal and free direction, giving space for a second bay, or expanding the original, or even more electronics, in addition to + 2 lateral conformal bays where the original air intakes were in the frontal section and cheeks of the hunting.

These changes can reduce final speed and perhaps some maneuverability, but increase internal load by 50% to 70%. The plane will absurdly reduce the need for external loads that compromise invisibility.

An exchange between the external engine Versus external load....the engine would not be more visible than any tanks or underwing missiles.

Those louvres on the Mig 29 are not for air combat but for unprepared airstrip ops. They open up as the intake itself is closed off. They are not meant to add extra air when manuvering.The intakes are ideally placed for air combat (below the aircraft).

 

[carvalho2008]

Those louvres on the Mig 29 are not for air combat but for unprepared airstrip ops. They open up as the intake itself is closed off. They are not meant to add extra air when manuvering.The intakes are ideally placed for air combat (below the aircraft).

Only auxiliary when dogfight....!

when BVR combat, you don't need this..

 

[red admiral]

How wide are the error bars on those models?

Not that big actually if you take into account other variables like production numbers, rates etc.

You can also split into cost/mass for different aircraft bits e.g. airframe structure, vehicle systems, engine, avionics if you have enough information