USAF/US NAVY 6th Generation Fighter Programs - F/A-XX, F-X, NGAD, PCA, ASFS news

[Ainen]

Agree but I expect there is some fat so close to 60k for the Mk7 should be doable.


Was thinking though if you are going F135 size why then go F135, you might as well use the XA100/101. More expensive again than the F135 but you would design the platform to make full use of the adaptive advantage. That is a step change in range. The timeframe to productionise that engine would be suitable for F/A-XX.

More is always possible(for additional usd), but here I think we did more of a thought experiment on the most affordable navair boost program.
Which is probably to do a f-14a like program: existing radar/missile, engine off the shelf, but result is still an f-4 improved in every single way - especially those that matter.

New goodies can wait, first priority is to cover up for things f-35 and bug can't do well enough in westpac.
Which is (1) operational gaps (still left from tomcat and intruder/prowler retirement) and (2) some technical issues (twin big engine design will hardly have onboard power problems, especially if we pay attention to it from day 1).
40t class naval fighter is an attractive capability, especially since heavier aircraft isn't the same as proportionally larger aircraft.
F-110s can be added later.

If it's feasible - it is simply a way how usn can field something meaningful fast enough and within available budget.

 

[Ozair]

More is always possible(for additional usd), but here I think we did more of a thought experiment on the most affordable navair boost program.
Which is probably to do a f-14a like program: existing radar/missile, engine off the shelf, but result is still an f-4 improved in every single way - especially those that matter.

New goodies can wait, first priority is to cover up for things f-35 and bug can't do well enough in westpac.
Which is (1) operational gaps (still left from tomcat and intruder/prowler retirement) and (2) some technical issues (twin big engine design will hardly have onboard power problems, especially if we pay attention to it from day 1).
40t class naval fighter is an attractive capability, especially since heavier aircraft isn't the same as proportionally larger aircraft.
F-110s can be added later.

If it's feasible - it is simply a way how usn can field something meaningful fast enough and within available budget.

Sure a mild upgrade and spiral update other systems in over time makes some sense. Problem is we know what the USN want and it is more than you are suggesting;

advanced sensors, advanced lethality, advanced range, and being able to integrate with manned and unmanned capabilities together

Navy Making Final Selection For F/A-XX Stealth Fighter, Plans For 2030s Service Entry

While the Air Force’s NGAD fighter initiative currently paused, the Navy is pushing ahead with its similar F/A-XX stealth jet program. With the Air Force’s NGAD currently paused, the Navy is pushing ahead with its F/A-XX carrier stealth fighter.

www.twz.com

Question is of those requirements what changes from the current generation?

Advanced sensors - You could argue APG-85 is probably as good a current system as can be bought today but will that be sufficient for a new build airframe in 2035... What else will be required from sensors, perhaps LIDAR, next gen EOTS and EODAS for certain.

Advanced Lethality - Is a AIM-260 and hypersonic ASM sufficient for increased lethality? Do we finally see some sort of Directed Energy Weapon especially if we have a twin engined behemoth with plenty of power generation available? It feels like 5th gen platforms are only finally now close to getting 5th gen weapons. How long would a notional 6th gen platform have to wait for weapons to match its capabilities?

Advanced Range - I expect an Adaptive cycle engine brings this. Simply building a bigger aircraft that holds more fuel but with current generation engines probably won't deliver the range increase the USN want or need.

Manned and Unmanned Teaming - No doubt that will be in place for the platform whether a minor upgrade or a full blown platform but where is the CCA that takes off and lands on a carrier going to come from? MQ-25 isn't sufficient nor capable enough for what the USN will need.

How about the EW mission. Will the F/A-XX incorporate the NGJ internally or will the USN push that mission to an unmanned platform.

Will F/A-XX be single or two seat or both?

USN likely have a good set of requirements, have three keen vendors and a slew of good technologies that are reasonably mature but their budget is the least certain aspect. Will the USN have the money to build what they want or will they have to compromise?

 

[dark sidius]

Sure a mild upgrade and spiral update other systems in over time makes some sense. Problem is we know what the USN want and it is more than you are suggesting;

Navy Making Final Selection For F/A-XX Stealth Fighter, Plans For 2030s Service Entry

While the Air Force’s NGAD fighter initiative currently paused, the Navy is pushing ahead with its similar F/A-XX stealth jet program. With the Air Force’s NGAD currently paused, the Navy is pushing ahead with its F/A-XX carrier stealth fighter.

www.twz.com

Question is of those requirements what changes from the current generation?

Advanced sensors - You could argue APG-85 is probably as good a current system as can be bought today but will that be sufficient for a new build airframe in 2035... What else will be required from sensors, perhaps LIDAR, next gen EOTS and EODAS for certain.

Advanced Lethality - Is a AIM-260 and hypersonic ASM sufficient for increased lethality? Do we finally see some sort of Directed Energy Weapon especially if we have a twin engined behemoth with plenty of power generation available? It feels like 5th gen platforms are only finally now close to getting 5th gen weapons. How long would a notional 6th gen platform have to wait for weapons to match its capabilities?

Advanced Range - I expect an Adaptive cycle engine brings this. Simply building a bigger aircraft that holds more fuel but with current generation engines probably won't deliver the range increase the USN want or need.

Manned and Unmanned Teaming - No doubt that will be in place for the platform whether a minor upgrade or a full blown platform but where is the CCA that takes off and lands on a carrier going to come from? MQ-25 isn't sufficient nor capable enough for what the USN will need.

How about the EW mission. Will the F/A-XX incorporate the NGJ internally or will the USN push that mission to an unmanned platform.

Will F/A-XX be single or two seat or both?

USN likely have a good set of requirements, have three keen vendors and a slew of good technologies that are reasonably mature but their budget is the least certain aspect. Will the USN have the money to build what they want or will they have to compromise?

They must built it no choice the Super Hornet start to be a tired and old plane and the F-35 will never maintain is promise and is not enough for the Pacific theater.

 

[Ainen]

Don't want this thread to turn into mywetdreamaircraft thread, so just a bareminimum example as logical exercise:

Literal F-35 forward fuselage with two engines outside of elongated rear bay section, making space for internal bays in-between (ideally - 2x5m - just a bit longer than vigilante linear bay, for instance).
4xAIM-174B/LRASM/JASSM-XR inside.
More heavy pylons outside for heavy hypersonics, asat, or, indeed, EW loads.

Same connectivity and fire control as basic f-35 blk iv. Maybe indeed second seat for the teaming, twin-seat f-35 wasn't built, but it was proposed - no arcane arts needed. Several times more free onboard power(and power flexibility, second engine!) for future development paths.

More fuel, higher aspect ratio wing(swing wing as an option), and more lift from the fuselage to get range (no reliance on new technology, no long research/testing, fast fielding) - if it was possible on 1960s TF30s, it's most certainly possible on ECU F135s.

Any additional technology later, to avoid budget strain and delays, because Chinese anti-ship dilemma is present now.
Basically - su-75 in reverse. It's indeed a very inelegant, brute force solution, but currently CSG desperately needs those dumb range metrics.

 

[Ozair]

They must built it no choice the Super Hornet start to be a tired and old plane and the F-35 will never maintain is promise and is not enough for the Pacific theater.

I don't think either of those statements are accurate assessments of the situation.

 

[BAROBA]

USN asked for a stealth fighter for Xmas, got the F-18E.

Let's be realistic about what the Navy asks for and what it actually gets.

Another F-18.....?
Thanks Mom....

 

[joshjosh]

They must built it no choice the Super Hornet start to be a tired and old plane and the F-35 will never maintain is promise and is not enough for the Pacific theater.

If readiness is the goal, the navy should reopen the F-18 production line immediately. You fight the war with the stuff you have, and right now we have F-18s. Losses in a peer war vs China will not be replaceable without a hot production line, and even a less ambitious F/A-XX won't be in production until the 2030s.

 

[Scott Kenny]

Was thinking though if you are going F135 size why then go F135, you might as well use the XA100/101. More expensive again than the F135 but you would design the platform to make full use of the adaptive advantage. That is a step change in range. The timeframe to productionise that engine would be suitable for F/A-XX.

Because the F135 is in production RIGHT NOW, and is common to the F35C.

Can go to the adaptive engines later on, if/when the F35s get them.

Just like the F-14 used a whole pile of off the shelf systems to be fielded faster: existing radar, missiles, engines, etc all went into the F-14A, while the -B was supposed to be the definitive version with new engines. Then you add capabilities to the radar and avionics in the F-14C...

 

[Ozair]

Because the F135 is in production RIGHT NOW, and is common to the F35C.

The intention isn't for F/A-XX to field as soon as possible. It is intended to IOC in the early to mid 2030s. In that context there is plenty of time for the XA-100/101 to mature and be available. Commonality is good but not king, there are already a number of different engines on the boats so removing the F414 and adding the XA-100/101 won't make that much of a difference especially in the context of the rest of the changes that would come with F/A-XX replacing the SH.

Can go to the adaptive engines later on, if/when the F35s get them.

I think that ship has sailed so to speak and it won't be happening any time soon. I expect even the smaller NGAP would be a better option than the F135 given the timeline of NGAP is approx 2028.

 

[Training_Dummy]

If readiness is the goal, the navy should reopen the F-18 production line immediately. You fight the war with the stuff you have, and right now we have F-18s. Losses in a peer war vs China will not be replaceable without a hot production line, and even a less ambitious F/A-XX won't be in production until the 2030s.

Without addressing your premise, Boeing is clearly in no position to credibly deliver warfighting capacity given its current situation. The US would be silly to entrust anything to Boeing besides ensuring extant system sustainment and delivering EX and T-7. It’s troubling but this is exactly the sort of creative destruction that could allow L3, Anduril, whoever, to embrace greatness through superior engineering and a non-legacy/union cost base.

 

[Manuducati]

If a current in service engine then reusing the F414 in the EPE variant makes sense. Navy already knows and is very happy with the engine, it is significantly lighter than the F110 and I expect they will be able to, with five years of concerted dev effort, get the thrust and durability close to the F110-129. Would also be a good export market for GE given that engine size has been popular on non US fighters.

F-414 are great engines but already underperforming with the F/A-18E-F Super Hornet. Even with the hypothetical 20% thrust increase of the EPE, I don't think they would be a solution for the F/A-XX. With internal weapons bay(s) and the fuel needed for PTO, I don't see the XX being less than 20% heavier than the Bug. Meaning poor thrust to weight ratio, poor acceleration, marginal one engine out performance, poor kinetics (to increase weapons performance).
You need at least F110-GE-432 level of performance.

 

[icyplanetnhc (Steve)]

The F135 is a massive engine at just over 6,400 lbs; that’s 2,000 lbs heavier than even the F110-400 with the extended tailpipe. How would you design an airframe around two such engines while having a relatively large internal fuel load, weapons bay, and "bringback" and also be within the limit of the Mk. 7 arresting gear?

EDIT: With around 54,000 lb limit on the arresting gear and assuming that you have 20,000 lbs of internal fuel (a bit more than the F-35C) and a very optimistic airframe empty weight of 32,000 lbs without engines (contractor empty weight, and the F-35C is around 28,000 lbs, Super Hornet is around 27,000 lbs), you have a "bringback" of 9,200 lbs of fuel and weapons, about the same as a Super Hornet but this is being very optimistic with the weights. Not that upgrading the arresting gear on the Nimitz-class carriers is out of the question, but things to consider.

 

[DrRansom]

If the Navy can pull out an ADVENT-powered F/A-XX in the next 10 years, a sort of super F-14 with heavy-missile armament, there is a very high probability the USAF is forced to buy it.

 

[FighterJock]

That is what I was thinking DrRansom. That is if the USAF end up cancelling the NGAD altogether without having anything that they can fall back on, then the F/A-XX is the only game in town for both services.

 

[Moose]

Without addressing your premise, Boeing is clearly in no position to credibly deliver warfighting capacity given its current situation. The US would be silly to entrust anything to Boeing besides ensuring extant system sustainment and delivering EX and T-7. It’s troubling but this is exactly the sort of creative destruction that could allow L3, Anduril, whoever, to embrace greatness through superior engineering and a non-legacy/union cost base.

So say we disqualify an established airframe builder and award to a team that has never built a full-size combat aircraft and that's the team which falls behind on milestones and/or runs over on cost. What's the plan then?

 

[DrRansom]

That is what I was thinking DrRansom. That is if the USAF end up cancelling the NGAD altogether without having anything that they can fall back on, then the F/A-XX is the only game in town for both services.

The more cheeky-prediction is that the F/A-XX can be 4++ gen stealthy, something like the SU-57, forward quadrant only, and the USAF will still get forced to buy it.

 

[FighterJock]

Don't say that DrRansom. That would not what both services would want, a 4++ gen fighter would be a step backward for them. And not the full 6th gen leap that it would bring especially from the F-22/F-35 5th Gen.

 

[Ozair]

So say we disqualify an established airframe builder and award to a team that has never built a full-size combat aircraft and that's the team which falls behind on milestones and/or runs over on cost. What's the plan then?

The current understanding is only LM, NG and Boeing are bidding on F/A-XX. The smaller entrants may be subs but I expect the smaller entrants see more value and opportunity in CCAs and that is where they are focusing their efforts.

The more cheeky-prediction is that the F/A-XX can be 4++ gen stealthy, something like the SU-57, forward quadrant only, and the USAF will still get forced to buy it.

That makes no sense and almost certainly the USN wouldn't even award a contract to a vendor offering that. The set of requirements they are using will almost certainly require all aspect stealth and they have the f-35C reference point to work from. The USN has rotated a lot of personnel through the F-35 JPO so will have an excellent corporate knowledge of what they want.

 

[DrRansom]

Don't say that DrRansom. That would not what both services would want, a 4++ gen fighter would be a step backward for them. And not the full 6th gen leap that it would bring especially from the F-22/F-35 5th Gen.

My argument for 4++ gen design is that I don't know how you get all-aspect stealth off a carrier deck while meeting range, payload, persistence goals. Not to mention, F/A-XX will also have to externally carry large ASMs, which is not in the least bit stealthy.

In the interest of something now in a reasonable budget, I can see the Navy reducing stealth requirements compared to the USAF's NGAD goals. The success of the NGAD program certainly argues for lower performance specifications.

But we will see - and soon if the Navy wants to sneak a march on the USAF.

 

[Training_Dummy]

as I take a step back and consider all of Boeings issues - Max, Starliner, T-7, 777x, balance sheet, labor strike, even ramping up EX, it’s hard to believe DoD giving Boeing anything but a CCA contract. Does NG go three for three on Raider, F/A-XX and maybe a rescoped manned PCA?

 

[Moose]

as I take a step back and consider all of Boeings issues - Max, Starliner, T-7, 777x, balance sheet, labor strike, even ramping up EX, it’s hard to believe DoD giving Boeing anything but a CCA contract. Does NG go three for three on Raider, F/A-XX and maybe a rescoped manned PCA?

It wasn't that long ago people were expecting NG to go to pieces if it didn't win B-21. Which to say both "NG's cooking" and "don't write off anyone."

 

[Training_Dummy]

So say we disqualify an established airframe builder and award to a team that has never built a full-size combat aircraft and that's the team which falls behind on milestones and/or runs over on cost. What's the plan i

It wasn't that long ago people were expecting NG to go to pieces if it didn't win B-21. Which to say both "NG's cooking" and "don't write off anyone.

Great point

 

[Training_Dummy]

So say we disqualify an established airframe builder and award to a team that has never built a full-size combat aircraft and that's the team which falls behind on milestones and/or runs over on cost. What's the plan then?

I guess what you’re saying is devil we know. Fair point. As for being established, what does history or pedigree even mean except to remind us how far Boeing has deviated from its roots on both sides of its bloodline? And my comment about L3 and Anduril wasn’t about NGAD or F/A-XX per se, or even CCA incr 1, but rather that middle distance where CCA incr X truly might blur some lines.

 

[Ozair]

as I take a step back and consider all of Boeings issues - Max, Starliner, T-7, 777x, balance sheet, labor strike, even ramping up EX, it’s hard to believe DoD giving Boeing anything but a CCA contract. Does NG go three for three on Raider, F/A-XX and maybe a rescoped manned PCA?

At the very least the commercial aspects and past performance will be evaluated by the USN team running the tender and at that stage Boeing may not be looked at as favorable. Noting the contract won't be fixed price perhaps that becomes less of an issue, Boeing might be better positioned when the US Govt assumes some of the risk.

 

[Desertfox]

as I take a step back and consider all of Boeings issues - Max, Starliner, T-7, 777x, balance sheet, labor strike, even ramping up EX, it’s hard to believe DoD giving Boeing anything but a CCA contract. Does NG go three for three on Raider, F/A-XX and maybe a rescoped manned PCA?

Most of Boeing's problems are Boeing Commercial, Boeing Military is just fine. Its got issues but so do the other two.

The USAF backup isn't F/A-XX its GCAP. GCAP is basically an 80% NGAD.

 

[flateric]

Most of Boeing's problems are Boeing Commercial, Boeing Military is just fine.

Yeah, it's blooming

Boeing to cut 10% of workers as defense unit loses $2B in 3 months

Performance on fixed-price programs is “simply not where it needs to be,” CEO tells employees.

www.defenseone.com

 

[Elysium]

My argument for 4++ gen design is that I don't know how you get all-aspect stealth off a carrier deck while meeting range, payload, persistence goals. Not to mention, F/A-XX will also have to externally carry large ASMs, which is not in the least bit stealthy.

In the interest of something now in a reasonable budget, I can see the Navy reducing stealth requirements compared to the USAF's NGAD goals. The success of the NGAD program certainly argues for lower performance specifications.

But we will see - and soon if the Navy wants to sneak a march on the USAF.

Honestly the whole thing sorta makes sense to me now. USAF cancelling NGAD because it doesn't see any credible opponent against who can create a qualitative and quantitative superiority against them in the near future (except for China). Additionally, the advancement on anti-stealth tech with medium-to long wave radars on the ground means the only design that can be truly considered stealthy will be broadband stealth designs, which are not compatible with fighter-like agility. And probably even those will be at risk of being shot down. That means only drones can do the job.
A hypothethical Super Raptor with more stealth, and bigger missiles would still lose to a ground based SAM with medium-wave radars and even bigger missiles.

The calculus changes against China. Not only they have the capability to build advanced fighters in numbers (as they're doing right now), the advantage of SAM cover disappears (although it might make some sense to reintroduce Kirov-style cruisers with their floating SAM bubbles, but that's just a flight of fancy, getting sidetracked). In this scenario, a fighter might still be the king of the skies. If we think about the see-first-shoot-first calculus, we can solve the issue 2 ways, either going the full stealth-route or making a plane with moderate stealth, but bigger radar and missiles (the thing DrRansom referred to as Su-57 like). I'd argue the first option already exists in the shape of the B-21, so going for the second option makes more sense imo, so I'm inclined to agree with DrRansom's proposal.

 

[bring_it_on]

The USAF backup isn't F/A-XX its GCAP. GCAP is basically an 80% NGAD.

How do I know it isn't 20% NGAD? Like what are you basing your assumptions on since we know exactly zilch in terms of what the USAF requirements were for NGAD and what technologies it matured, and demonstrated for inclusion on it or what the two teams still in the running offered as part of their submission for EMD? And also not a whole lot is known about the GCAP for that matter.

 

[Scott Kenny]

The F135 is a massive engine at just over 6,400 lbs; that’s 2,000 lbs heavier than even the F110-400 with the extended tailpipe. How would you design an airframe around two such engines while having a relatively large internal fuel load, weapons bay, and "bringback" and also be within the limit of the Mk. 7 arresting gear?

You'd need to make a lighter airframe than an F14.

Shouldn't be too hard, the swing wing is heavy. And most of the rest of the fuselage is metal, not composites, so there's plenty of places to find that you can reduce weight.

 

[Ainen]

Iirc f135 includes quite a lot of weight which is normally on the airframe, making direct number unfair.
Otherwise its thrust to weight would be in nk-32 area, I.e. a heavy bomber engine

 

[FighterJock]

GCAP is basically a UK NGAD, we know next to nothing at all about performance or what technologies will be included in the final design.

 

[Training_Dummy]

Most of Boeing's problems are Boeing Commercial, Boeing Military is just fine. Its got issues but so do the other two.

The USAF backup isn't F/A-XX its GCAP. GCAP is basically an 80% NGAD.

I don’t agree. Its engineering culture has eroded from the top down, it has a legacy cost base (non right to work states, labor unions, etc) and has not delivered a fully internally developed airframe since F-15 and C-17. Maybe I’m thinking about this all wrong and this is the perfect time to break up BA, put new “real (externally sourced) leadership” in Boeing Defense and Space and give them the scaled down PCA component of NGAD.

 

[Training_Dummy]

For those who think I’m anti Boeing and to those brilliant engineers at Boeing (some of whom may be lurking), far from it. My father was a test pilot for McD, I grew up on air show flight lines etc etc. I’m just trying to work this out, since the knock on effects seem non trivial.

 

[icyplanetnhc (Steve)]

You'd need to make a lighter airframe than an F14.

Shouldn't be too hard, the swing wing is heavy. And most of the rest of the fuselage is metal, not composites, so there's plenty of places to find that you can reduce weight.

There are also areas that will drive weight higher. As a Fighter/Attack, I'd imagine that the F/A-XX would at least need internal weapons bay the size of the F-35C's, if not larger. For range and endurance, it would likely have to carry more internal fuel than the 16,200 lbs that the F-14 had.

I'm not sure why the F/A-XX would want to trend towards an F135-sized engine, when the likely larger NGAD is likely to use NGAP engines that are smaller, around F119-size. I believe the Lockheed/Boeing A/F-X design (AFX-653 if I recall) had PW7000 engines, which were F119-derivative engines but smaller, at around 25,300 lbf thrust, although granted, the mission priorities as Attack/Fighter is different from F/A-XX. I just don't think one should be enamored and carried away by the raw static thrust number of the F135 and try to seek applications for it left and right, even when it may not make sense.

EDIT: I'm not sure of those PW7000 thrust numbers, which came from Flight International Jan. 26 - Feb. 1, 1994, reflect the dry thrust or augmented, but regardless, the point stands even for A/F-X, the engine thrust is understood to be a bit less than the F119.

 

[Sundog]

The engines for the F/A-XX aircraft will be sized for the mission. I don't see them being three stream engines, because I don't think the navy has much need for super cruise, but I could be wrong. That will save them money. Having said that, it will be a new engine or an engine that uses an existing a core and a new fan, or something like that and I see it being twin engine aircraft with engines smaller than the F-135.

 

[Josh_TN]

Three stream is not necessary for super cruise; the bigger benefit is range/endurance, and I cannot imagine the USN does not think that is a priority.

 

[Scott Kenny]

There are also areas that will drive weight higher. As a Fighter/Attack, I'd imagine that the F/A-XX would at least need internal weapons bay the size of the F-35C's, if not larger.

I'm assuming closer to the A-12 bay size, room for 4x 2000lb plus 2x AMRAAM.

For range and endurance, it would likely have to carry more internal fuel than the 16,200 lbs that the F-14 had.

Yes, I'm assuming more like 25,000lbs if not more. Though since the F-35 carries some 18,000lbs and has a 1500nmi range, we're probably talking more like 35-40klbs of fuel internally to feed a pair of F135 engines.

I just don't think one should be enamored and carried away by the raw static thrust number of the F135 and try to seek applications for it left and right.

It's not about the static thrust. It's about the logistic advantages of having one engine type across the air wing. Static thrust is a bonus.

 

[Ozair]

I'm assuming closer to the A-12 bay size, room for 4x 2000lb plus 2x AMRAAM.

That seems a bit big to me. I am thinking bay depths similar to the F-35 so 2x 2000 lbs plus AAM but longer to allow larger munitions in, such as JASSM. That may also allow for a separate bay for AIM-120 sized weapons similar to F-22 but not side mounted. Could even lengthen the bay to be just beyond 18ft which would allow SDB sized munition to be packed in three length wise.

Yes, I'm assuming more like 25,000lbs if not more. Though since the F-35 carries some 18,000lbs and has a 1500nmi range, we're probably talking more like 35-40klbs of fuel internally to feed a pair of F135 engines.

F-35 is ~1500nmi one way.. A realistic F-35A/C combat radius on a high altitude profile would put it closer to 800 to 850nmi. I cannot see F/A-XX having 35k lbs of fuel especially if you want the payload to be as suggested above. That is where the Adaptive engines come into play to reduce the fuel use during cruise.

It's not about the static thrust. It's about the logistic advantages of having one engine type across the air wing. Static thrust is a bonus.

In most cases the best metric is the dry thrust. The aircraft won't want to be in afterburner for long periods so an engine that has high mil power but comparatively lower augmented thrust, like the F135 and F119, is the better option.

 

[Scott Kenny]

That seems a bit big to me. I am thinking bay depths similar to the F-35 so 2x 2000 lbs plus AAM but longer to allow larger munitions in, such as JASSM. That may also allow for a separate bay for AIM-120 sized weapons similar to F-22 but not side mounted. Could even lengthen the bay to be just beyond 18ft which would allow SDB sized munition to be packed in three length wise.

Well, in the A-12 that was 4x bays. AMRAAMs in two bays, and two bays each big enough to hold 2x 2000lb bombs (or more practically, 1x HARM/Harpoon and 1x 2000lb LGB/JDAM).

An 18ft long bay is not a bad idea, however.

F-35 is ~1500nmi one way.. A realistic F-35A/C combat radius on a high altitude profile would put it closer to 800 to 850nmi. I cannot see F/A-XX having 35k lbs of fuel especially if you want the payload to be as suggested above. That is where the Adaptive engines come into play to reduce the fuel use during cruise.

Well, the assumed combat radius I think the USN wants is on the order of 2000nmi. Which makes things ... complicated.

In most cases the best metric is the dry thrust. The aircraft won't want to be in afterburner for long periods so an engine that has high mil power but comparatively lower augmented thrust, like the F135 and F119, is the better option.

Right, but again the primary driver was logistic commonality with the F-35C.

My concept was all the avionics of an F35, two F135 engines, the larger bay(s), and a crapton of fuel. Two seats so the backseater can wrangle drones, and alternatively play RIO/bombardier-navigator.

Edit: this is basically exactly how the F-14 was built: take existing sensors and engines and drop them into a new airframe.

 

[Josh_TN]

No one is putting two F135s in anything.