CGI - Possible configuration of the Boeing F-47 NGAD

[Sferrin]

Model 432 internal layout, length 19.5 m, wingspan 14.0 m, volume 77 m³ ...

Any TVC? Fluidic TVC?

 

[Training_Dummy]

I really do love everything but I have this sneaky feeling F-47 will have very interesting main wings. I think Rodrigo’s bird like F-47 configuration comes closest for me, at least in spirit.

To crystallize the spirit of what I mean, perhaps the sweep and angle of the wings are such that it could shield the thermal signature of the exhausts 40d off of port and starboard? This would allow the exhausts to focus on minimizing ventral and dorsal IR signatures while allowing for more degrees of freedom to employ known solutions for just lateral TV (mechanical, fluidic, 2D, 3D, etc) since ya know, canards are as American as french fries now (don’t be a little pitch, you know what I mean).

 

[dark sidius]

Most probably the best way to reduce wingspan / area without changing the overall layout too much.



I always design solid models. This way, SolidWorks can display the body volume directly.
Knowing the volume allows for an estimation of the weight. A density of around 580 kg/m³ seems appropriate to estimate the maximum takeoff weight of a modern supersonic combat jet.
More info here: https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-507567




112 m³ of solid body volume is truly enormous!
For comparison, my model 432 is 77 m³ "raw" (solid model, without any hollow space) and my KF-21 model, based on the KAI three-view drawing, has a volume of 51 m³. I think the F-35 has a volume of around 50–55 m³ and the F-22 around 60–65 m³.

Which brings me back to the topic of density: Ideally, we would know the exact volume of the F-22 (or a similar twin engine stealth fighter) in order to make a good estimate of its density. This would then allow us to obtain a realistic assessment of the weight of our own model.

Model 432 internal layout, length 19.5 m, wingspan 14.0 m, volume 77 m³ ...

Beautiful model but still does not match with the official rendering, not same Nose shape , too much triangular shape fuselage, with the little picture we have Reddington777 seem to be near of the F-47 official rendering. But you can be right if the official picture is a Debunk of the real shape .... ARRRgggg it will never end before the public roll-out

 

[Reddington777]

112 m³ of solid body volume is truly enormous!
For comparison, my model 432 is 77 m³ "raw" (solid model, without any hollow space) and my KF-21 model, based on the KAI three-view drawing, has a volume of 51 m³. I think the F-35 has a volume of around 50–55 m³ and the F-22 around 60–65 m³.

Which brings me back to the topic of density: Ideally, we would know the exact volume of the F-22 (or a similar twin engine stealth fighter) in order to make a good estimate of its density. This would then allow us to obtain a realistic assessment of the weight of our own model.

Model 432 internal layout, length 19.5 m, wingspan 14.0 m, volume 77 m³ ...

Yeah, I think with the given length assumption and planform shape, I dont see it going down that low. Making it shorter though might, as the rest of the dimensions scale accordingly.

My J-36 model with the troughs has a volume of 136m³, just as a upper bound value.

Yeah as I was modeling it, I think a lot of the F-47 will sit between J-XDS and J-36 just because the US is building only a single air superiority fighter. There's no opportunity to have a larger and smaller air superiority fighter.

I think the current planform would offer a larger volume than J-XDS just because the nose seems proportionally wider. The rest of the body (assuming length is accurate) would be at least equal or possibly longer. So if the F-47 had a volume between J-XDS and J-36, I wouldnt be surprised. Given where the volume sits now, which still ends up lower than the J-36, it might still make sense - especially since J-XDS should have a larger volume than 5th gen fighters by quite a margin.

I haven't compared the fuselage thickness to the J-36 (without the dorsal intake) yet. If it ends up being thicker then Ill make it thinner. Otherwise Ill leave it as is.

 

[Reddington777]

I really do love everything but I have this sneaky feeling F-47 will have very interesting main wings. I think Rodrigo’s bird like F-47 configuration comes closest for me, at least in spirit.

To crystallize the spirit of what I mean, perhaps the sweep and angle of the wings are such that it could shield the thermal signature of the exhausts 40d off of port and starboard?

If that implies the wings goes up to or past the end of the plane, well I like that idea because it fits the firebird patch. The problem then is you need a high wing sweep and possibly a correspondingly high wingspan. How much wing sweep? How much wingspan? and how much of the exhausts plume do you want to cover with it?

If someone familiar with aerodynamics could speak more about whether long, 60+degree sweep dihedral / andhedral wings would be viable on a fighter, Id love to know.

 

[targetpractice]

I think a lot of the F-47 will sit between J-XDS and J-36

Agree 100%

 

[VTOLicious]

Yeah, I think with the given length assumption and planform shape, I dont see it going down that low. Making it shorter though might, as the rest of the dimensions scale accordingly.

Yeah as I was modeling it, I think a lot of the F-47 will sit between J-XDS and J-36 just because the US is building only a single air superiority fighter. There's no opportunity to have a larger and smaller air superiority fighter.

I think the current planform would offer a larger volume than J-XDS just because the nose seems proportionally wider. The rest of the body (assuming length is accurate) would be at least equal or possibly longer. So if the F-47 had a volume between J-XDS and J-36, I wouldnt be surprised. Given where the volume sits now, which still ends up lower than the J-36, it might still make sense - especially since J-XDS should have a larger volume than 5th gen fighters by quite a margin.

I haven't compared the fuselage thickness to the J-36 (without the dorsal intake) yet. If it ends up being thicker then Ill make it thinner. Otherwise Ill leave it as is.

Size and weight of the F-47 depend significantly on its engines. It can be assumed that the XA102/103 engines deliver higher thrust than the F119, but lower than the F135 (35,000 vs. 43,000 lbf). Consequently, I expect a maximum thrust of approximately 40,000 lbf (18,144 kgf) and a maximum takeoff weight of 96,000 lb (43,545 kg). This represents a 15% increase compared to the F-22.

With an assumed density of 580 kg/m³ and a expected MTOW of 96,000 lb (43,545 kg), this results in a volume of 75 m³. Therefore, I expect the F-47 to fall within this range. Anything significantly higher appears highly unlikely to me.

 

[VTOLicious]

Any TVC? Fluidic TVC?

Pitch (& roll) mechanical, yaw rather fluidic.
I expect that all next-generation fighter jets without a vertical stabilizer will require at least thrust vectoring for yaw control, in addition to control effectors on the wings ("crow mixing" of elevons).

 

[Reddington777]

With an assumed density of 580 kg/m³ and a expected MTOW of 96,000 lb (43,545 kg), this results in a volume of 75 m³. Therefore, I expect the F-47 to fall within this range. Anything significantly higher appears highly unlikely to me.

If your assumed density heuristic is 580kg/m3, then that implies my model is far too big, but the central question is can you still have a MTOW of more or less 96k in a larger, and less dense planform and how much weight the added planform area translates to.

Im not sure where the 580 number comes from (i may have found the research article on it, but that seems to be excluding cavities like intake ducts and what not), but if you assumed that measure from an F-22 or even from more conventional fighters, then it may or may not be strictly enforceable on a large lambda wing.

Taking the J36 internal volume measure of 136m3 (assuming somewhat high accuracy) and your density of 580kg/m3, and assuming the J-36 has three 40k lbf thrust engines, you get a MTOW of 174klbs and a total thrust of 120klbs, or a measly 0.69 T/WR. Thats nearly an F-35 level of T/WR and probably even less than an F-35.

There are good reasons to have a large but less dense planform. You have higher lift and larger control surfaces not to mention a flatter geometry for the same height among many others.

112m3 may well be too big, but it can also be more a function of the weight that greater surface area built with current composites adds to a given MTOW weight calculation than strictly a single measure of density.

--

Went and looked through some old J-36 speculation.

@Nx4eu posted this comment about the J36's MTOW:

https://www.secretprojects.co.uk/th...-aircraft-news-and-analysis.40872/post-847784
Working off the 136m3 volume measurement and various combinations of MTOWs, I get a density of between 300 - 500 kg/m3 (150k lb MTOW + 40k lbf engines iirc). 105k MTOW with 40 - 50klbf engines, gets me to 350 kg/m3. Applying that figure to my 112m2 leaves me at 86,500 MTOW. For an air superiority fighter, the J-36 probably wont be doing 150k MTOW either and in the comment I linked, Nx4eu used 80 to 100 MTOW

 

[VTOLicious]

If your assumed density heuristic is 580kg/m3, then that implies my model is far too big, but the central question is can you still have a MTOW of more or less 96k in a larger, and less dense planform and how much weight the added planform area translates to.

Im not sure where the 580 number comes from (i may have found the research article on it, but that seems to be excluding cavities like intake ducts and what not), but if you assumed that measure from an F-22 or even from more conventional fighters, then it may or may not be strictly enforceable on a large lambda wing.

Taking the J36 internal volume measure of 136m3 (assuming somewhat high accuracy) and your density of 580kg/m3, and assuming the J-36 has three 40k lbf thrust engines, you get a MTOW of 174klbs and a total thrust of 120klbs, or a measly 0.69 T/WR. Thats nearly an F-35 level of T/WR and probably even less than an F-35.

There are good reasons to have a large but less dense planform. You have higher lift and larger control surfaces not to mention a flatter geometry for the same height among many others.

112m3 may well be too big, but it can also be more a function of the weight that greater surface area built with current composites adds to a given MTOW weight calculation than strictly a single measure of density.

The 580 number comes from an earlier discussion, here: https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-507567
This number is not universally applicable, and the greater the deviation from the characteristics of the example aircraft, the more the result will deviate from reality. Ideally, the volume of an aircraft with comparable characteristics would be known, such as the F-22.

However, I applied that number on the F-22 (83,500 lb / 37,875 kg MTOW). The result is 65 m³ of solid body volume, which seems plausible to me. Hence, I consider it good enough for an initial assessment of my model - It's a plausibility check!

 

[Reddington777]

The 580 number comes from an earlier discussion, here: https://www.secretprojects.co.uk/th...eight-multirole-fighter-lmf.38539/post-507567
This number is not universally applicable, and the greater the deviation from the characteristics of the example aircraft, the more the result will deviate from reality. Ideally, the volume of an aircraft with comparable characteristics would be known, such as the F-22.

However, I applied that number on the F-22 (83,500 lb / 37,875 kg MTOW). The result is 65 m³ of solid body volume, which seems plausible to me. Hence, I consider it good enough for an initial assessment of my model.

I had literally just edited calculations based off the J36 into my comment above and found d a density of somewhere between 300 to 500 kg/m3. The 500 number came from a MTOW of 150klb and a thrust of 120klb. The more likely / average cases were between 80klb and 105klb MTOW, and combined with the 136m3 volume estimation came out to between 300 and 350 kg/m3. Applied to my 112m3 measurement, that comes out to roughly 86.5k lb MTOW, which seems in band.

I did however consider how I could change the planform using the numbers you calculated. In tandem with what @Training_Dummy was saying, it could very well be that the plane has a shorter aft fuselage section (or just in general a shorter plane by scaling down all dinensions) while having even more high sweep wings. I think my intakes could probably be smaller and shorter too, which could certainly conclude in a much denser and smaller volume airframe.

Im going to complete this larger model and send it off first, then work on a smaller model with a different planform for the aft fuselage.

 

[Scott Kenny]

Size and weight of the F-47 depend significantly on its engines. It can be assumed that the XA102/103 engines deliver higher thrust than the F119, but lower than the F135 (35,000 vs. 43,000 lbf). Consequently, I expect a maximum thrust of approximately 40,000 lbf (18,144 kgf) and a maximum takeoff weight of 96,000 lb (43,545 kg). This represents a 15% increase compared to the F-22.

With an assumed density of 580 kg/m³ and a expected MTOW of 96,000 lb (43,545 kg), this results in a volume of 75 m³. Therefore, I expect the F-47 to fall within this range. Anything significantly higher appears highly unlikely to me.

That's a bigger MTOW than I've been expecting. Though I suppose 80kish mission TOW plus ~16klbs of external capacity makes sense.

Like how the F-22 takes off at about 65k with full internal fuel and warload.

 

[Nx4eu]

I had literally just edited calculations based off the J36 into my comment above and found d a density of somewhere between 300 to 500 kg/m3. The 500 number came from a MTOW of 150klb and a thrust of 120klb. The more likely / average cases were between 80klb and 105klb MTOW, and combined with the 136m3 volume estimation came out to between 300 and 350 kg/m3. Applied to my 112m3 measurement, that comes out to roughly 86.5k lb MTOW, which seems in band.

I did however consider how I could change the planform using the numbers you calculated. In tandem with what @Training_Dummy was saying, it could very well be that the plane has a shorter aft fuselage section (or just in general a shorter plane by scaling down all dinensions) while having even more high sweep wings. I think my intakes could probably be smaller and shorter too, which could certainly conclude in a much denser and smaller volume airframe.

Im going to complete this larger model and send it off first, then work on a smaller model with a different planform for the aft fuselage.

My 136 cubic meters was based off an aircraft that was 21.5m long. If the J-36 was shorter like 20.5m long as has been previously speculated. This drops the volume down to 118 cubic meters.

If we go as low as TWZ measurements, of 19.5m. This drops the volume down to 101 cubic meters. All of this assuming my model is anywhere accurate.

 

[MadRat]

My opinion is no canard and more of a hooded fore-section. There will be more than 2 areas that open for weapons.

 

[FlyGuy369]

My opinion is no canard and more of a hooded fore-section. There will be more than 2 areas that open for weapons.

Explain hooded foresection!

 

[Reddington777]

So with the numbers that Nx4eu gave, I went to see if scaling down my models and applying different densities would still accommodate the same internals.

These are the calculated densities for each given volume. Then I used each density measure to derive a volume assuming that the MTOW remains 96,000 lbs.

J-36 Assumed Volume	J-36 Density	Max F-47 derived volume for 96k MTOW
101 m3	403.6 kg/m3	92.3 m3
118 m3	471.6 kg/m3	107.9 m3
135 m3	350.2 kg/m3	124.3 m3

I scaled the model to three different lengths and measured their corresponding volume:

F-47 Length	F-47 Volume
18.9m - F-22 length	86 m3
19.7m - Halfway F-22 and YF-23 length	97 m3
20.55m - YF-23 length	110.2 m3

This might seem like a trivial calculation, but each time only the fuselage, intakes and exhaust are scaled. The engines, weapon bays and weapons are not. For each scaled model, I did some remodeling of the intakes. I made the fuselage a bit flatter and altered the contours to be a little more steep to accommodate the 4.6 ft diameter engines. Also had to make the landing gear stowage a little more angled. At 18.9m, I can still get the fuselage to fit, but considering aircraft skin thickness, it's a tight fit that makes me uncomfortable.

For safe measure, I went with a 98m3 volume at 19.8m length. This keeps the large engines, room for side by side SiAWs in the weapon bays and fits the same sized wheels as before as well - all with what I think is a workable margin of separation. Under the assumption that the J-36 still has higher volume, the volume at this length are still under those numbers (meaning a bit higher density).

In the off (and what I think is unlikely) chance that TWZ is right and all the people who measured the Lop Nur satellite capture of the J-36 are all wrong, I think there's still this planform could work:

Using 403.6 kg/m3 as the density and 98m3 as the volume, then our MTOW is 87,198 lb, which still puts us somewhat higher than the F-22.

 

[Reddington777]

Explain hooded foresection!

Hooded foresection sounds like a euphemism for something bad lol...

If im not mistaken, he is referring to the section behind the cockpit where it should transition gradually like a ramp down to the engines - like the F35 and J35 rather than the earlier J-20s, the X32 or the YF-23 where the cockpit comes up like a bubble then quickly blends into the fuselage within a short distance. The F22 sits at a halfway between the two.

@MadRat if you scroll up, omy original wider model had a hooded fuselage, but in my post, I highlighted the shadow behind the cockpit. To me, I find that too steep to be a hooded dorsal neck area. I think looking at the X32 and the MDD ATF designs they are pop up bubble style cockpits and dont have hooded fuselages leading up to the cockpit so I modeled out the hooded part and went with a similar pop up bubble canopy.

As for the canards, I dont like them either, but they are om both renders though and theres no indication that they were painted on like the landing gear was.

 

[VTOLicious]

So with the numbers that Nx4eu gave, I went to see if scaling down my models and applying different densities would still accommodate the same internals.

These are the calculated densities for each given volume. Then I used each density measure to derive a volume assuming that the MTOW remains 96,000 lbs.

J-36 Assumed Volume	J-36 Density	Max F-47 derived volume for 96k MTOW
101 m3	403.6 kg/m3	92.3 m3
118 m3	471.6 kg/m3	107.9 m3
135 m3	350.2 kg/m3	124.3 m3

I scaled the model to three different lengths and measured their corresponding volume:

F-47 Length	F-47 Volume
18.9m - F-22 length	86 m3
19.7m - Halfway F-22 and YF-23 length	97 m3
20.55m - YF-23 length	110.2 m3

...Using 403.6 kg/m3 as the density and 98m3 as the volume, then our MTOW is 87,198 lb, which still puts us somewhat higher than the F-22...

I think it doesn't work this way. As said before, the density number is not universally applicable. You should choose an example aircraft of similar size and characteristics, of which you know weight and volume. We know nothing about the J-36. Neither its actual weight nor its actual dimensions.

To obtain a realistic result, you need:
1) Accurate weight specifications of the example aircraft (ideally empty and maximum weight).
2) A precise three-view drawing from which you can create a 3D model to determine the volume.
...or you have reliable staistical data of various aircraft available.

I admit that the 580 number may not be accurate as well, but I'm confident it's not far off...

That's what I get for the KF-21:
Maximum takeoff weight (From official brochure): 56,400 lb (25,583 kg)
Solid body volume (My 3D model, based on offical 3-view): 50.94 m³
Density: 502 kg/m³

It surprised me that the KF-21s specified maximum takeoff weight is significantly lower than that of the F-35A, even though the KF-21 is slightly larger and has two engines. However, it currently does not feature IWBs. If I were to use the weight of the F-35A (65,918 lb / 29,900 kg) for the KF-21, the density would be 587 kg/m³.
And if I assume, for example, that the F-35A has 4 m³ more volume than the KF-21, I arrive at 544 kg/m³.

Therefore, I am quite confident that a number between 500 and 600 is realistic (to determine the maximum takeoff weight of a supersonic stealth fighter based on its volume, and/or judge if the volume is within a realistic margin in relation to the anticipated maximum takeoff weight).

I made the fuselage a bit flatter and altered the contours to be a little more steep to accommodate the 4.6 ft diameter engines.

4.6 ft (55 in) is a very large diameter. The F135 has a fan diameter of 3.58 ft (41 in) and a maximum diameter of 3.8 ft (46 in). I would assume XA102/103 are in the 40,000 lbf thrust class, and therefore not larger than the F135.

 

[Reddington777]

I think it doesn't work this way. As said before, the density number is not universally applicable. You should choose an example aircraft of similar size and characteristics, of which you know weight and volume. We know nothing about the J-36. Neither its actual weight nor its actual dimensions.

Density should be different between different aircraft and it should fall into a range like you describe, but it's also just determined by what the MTOW and volume is, which are, in turn, determined by how much thrust is available and the TWR of a given aircraft.

In the comment I linked, I simply took some MTOWs from what others have said and used different volumes to get a sense of the range of possible densities I was looking at. I don't see what's "wrong" about looking at different possible densities a new generation of fighter could have and comparing that to my planform. Your numbers are realistic, but there are other plausible densities.

I admit that the 580 number may not be accurate as well, but I'm confident it's not far off...

Therefore, I am quite confident that a number between 500 and 600 is realistic (to determine the maximum takeoff weight of a supersonic stealth fighter based on its volume, and/or judge if the volume is within a realistic margin in relation to the anticipated maximum takeoff weight).

I don't agree or disagree to your numbers really. As I said - it's just a matter of what numbers you are assigning to each input. This probably doesn't need explanation, but for the J-36, if you assume max thrust is always 83% of MTOW, and we go with the 118m3 derived from the 20.5m measurement of the J-36, then you get a density of 512kg/m3. Under the same assumptions, but with a volume of 101m3, you get a density of 598kg/m3. Your range can work. It just depends on MTOW.

Estimates of the J-36 MTOW generally range from 85k lbs to as high as 150k lbs as the extreme highs and lows. Correspondingly, thrust estimates go from 3x 30k thrust engines up to 3x 50k thrust engines. With 3x 30k thrust engines and a MTOW of 103klbs, you get a density of sub 389m3. Sure - density isn't universally applicable, but the point here is to show that there are a larger range of densities that are derived from realistic and plausible parameters especially for aircraft that are somewhat unconventional. Beyond that, its a matter of whether you can or cannot fit the hardware to achieve those specs.

We aren't at that kind of granularity when we're still planform guessing from 1/4 of a plane.

4.6 ft (55 in) is a very large diameter. The F135 has a fan diameter of 3.58 ft (41 in) and a maximum diameter of 3.8 ft (46 in). I would assume XA102/103 are in the 40,000 lbf thrust class, and therefore not larger than the F135.

I can run with 46 inches. Wikipedia states 40inches diameter for the F119. As long as an additional 6 inches to diameter is enough to accomodate the third stream then all is well.

 

[MadRat]

Explain hooded foresection!

Reddington summed it up. With Boeing patents the canards become unecessary. Low drag to the extreme would be the target.

 

[Reddington777]

4.6 ft (55 in) is a very large diameter. The F135 has a fan diameter of 3.58 ft (41 in) and a maximum diameter of 3.8 ft (46 in). I would assume XA102/103 are in the 40,000 lbf thrust class, and therefore not larger than the F135.

I forgot to add - are ACE engines partitioning the same volume / diameter of an F-119 sized engine? or would it be adding volume / diameter to a central chamber that's already F-119 sized?

 

[Scott Kenny]

4.6 ft (55 in) is a very large diameter. The F135 has a fan diameter of 3.58 ft (41 in) and a maximum diameter of 3.8 ft (46 in). I would assume XA102/103 are in the 40,000 lbf thrust class, and therefore not larger than the F135.

It is, but 50-52" would seem reasonable. 55" is the diameter of the F101. ~48" is the max diameter of F100, 110, F119, and even F135.

 

[Scott Kenny]

I forgot to add - are ACE engines partitioning the same volume / diameter of an F-119 sized engine? or would it be adding volume / diameter to a central chamber that's already F-119 sized?

I have been assuming that they're a little bigger. ~2" ish.

 

[Dreamflyer]

Came across this today, in a pdf from 2018.
Text says "USN - UCAS - FAA-XX" but the shape makes me think about the nice assumptions, calculations & creations in this (USAF F-47) thread.

Most probably the image has already been shared somewhere on the forum before (?) but I can´t remember and there are way too many posts about PCA, NGAD, F-47, F/A-XX, etc. for me to go through to check...

 

[baseball801802]

Came across this today, in a pdf from 2018.
Text says "USN - UCAS - FAA-XX" but the shape makes me think about the nice assumptions, calculations & creations in this (USAF F-47) thread.

Most probably the image has already been shared somewhere on the forum before (?) but I can´t remember and there are way too many posts about PCA, NGAD, F-47, F/A-XX, etc. for me to go through to check..

Woah. Im more interested in the MCTUAS. Looks like the bird of prey. Also pretty interesting they listed the F/A-XX as unmanned.

 

[Dreamflyer]

Also pretty interesting they listed the F/A-XX as unmanned.

The document it came from is only about UAS.

Here another very similar but not identical image, published in a document called "Future UAS in a budget constrained environment".
The same shape/configuration with forward-placed canards and BoP-style gull wing is used for USAF´s 'MQ-X' and USN´s 'UCLASS', 'UCAS' and 'FAA-XX' (*) as well.

I think the shape, perhaps just generic and even if it´s only a top-view, corresponds rather closely/especially with what forum-member Redington777 came up with as possible configuration for Boeing´s F-47. Maybe that is just a strange coincidence, maybe not.

(*): Perhaps envisioned (years ago) as an unmanned or optionally manned variant of F/A-XX ?? Just guessing.

 

[Reddington777]

Therefore, I am quite confident that a number between 500 and 600 is realistic (to determine the maximum takeoff weight of a supersonic stealth fighter based on its volume, and/or judge if the volume is within a realistic margin in relation to the anticipated maximum takeoff weight).

I've reached a volume of 80 m2 at 62.2 ft and a density of 544.31 kg/m3. It's taken on a very F-22 looking side profile:

I want to confirm some internals with people:

The wheel clearance and weapon bay clearance seems really really small.
0.0251m (0.988 inches) is the smallest clearance the wheel has to the outer bay doors.
0.0519 m (2.04 inches) is the shortest distance from the wheel to the intake walls.
0.0544 m (2.14 inches) is the shortest distance from the engine casing to the weapon bay wall.

Are these clearances at all plausible? What clearances should I be observing here?

This is after I had to reduce the rear weapon bay width. It carries a tightly packed 3 - 4 AAMs but can't fit two SiAW anymore. Only the front bay can fit that.

 

[Scott Kenny]

I've reached a volume of 80 m2 at 62.2 ft and a density of 544.31 kg/m3. It's taken on a very F-22 looking side profile:

I want to confirm some internals with people:

The wheel clearance and weapon bay clearance seems really really small.
0.0251m (0.988 inches) is the smallest clearance the wheel has to the outer bay doors.
0.0519 m (2.04 inches) is the shortest distance from the wheel to the intake walls.
0.0544 m (2.14 inches) is the shortest distance from the engine casing to the weapon bay wall.

Are these clearances at all plausible? What clearances should I be observing here?

This is after I had to reduce the rear weapon bay width. It carries a tightly packed 3 - 4 AAMs but can't fit two SiAW anymore. Only the front bay can fit that.
View attachment 795323

1-2" wheel well clearance is tight but doable. You'd need to carefully plan where any reinforcing rings are around the inlets, and where any ribs are around the inside of the bays.

The powers that be will not like having the inlets visible through the landing gear doors, so there's a physically separate bay from the inlets. Yes, that adds weight, but it also adds strength.

However.

I think this one is a little too small, the engines too close to the weapons bay. You'd have to route all the inlet spill around the outside of the engine in an attempt to keep things cool, and I just flat think that the distance between the engine centerlines is too close. Need to scale things up a bit.

What was the distances between the engines and weapons bay of the A-5 again? I'd probably use that as the minimum viable.

Edit: what do those dimensions look like if you make the beast 68ft long?

 

[VTOLicious]

It is, but 50-52" would seem reasonable. 55" is the diameter of the F101. ~48" is the max diameter of F100, 110, F119, and even F135.

F135-PW-100 (43,000 lbf):
Max: 46" (1168 mm)
Inlet: 43" (1092 mm)
Fan: 41" (1041 mm)

I don't think the XA102/103 would exceed these dimensions. It could even be a few inches smaller.

 

[Reddington777]

F135-PW-100 (43,000 lbf):
Max: 46" (1168 mm)
Inlet: 43" (1092 mm)
Fan: 41" (1041 mm)

I don't think the XA102/103 would exceed these dimensions. It could even be a few inches smaller.

Going off of wikipedia numbers:

F135: Diameter: 46 in (1,170 mm) max., 43 in (1,090 mm) at the fan inlet
F119: Diameter: Approx. 40 in (100 cm) inlet, 48 in (120 cm) overall, 50 in (130 cm) maximum

The language is sorta vague but F135 seems to have a wider inlet while F119 is wider overall.

Length wise, F135 is larger.

X102/3 was said to be scaled down from AETP, which was supposed to fit the F135 form factor, but who knows if that's length? width? both?

 

[Sferrin]

Came across this today, in a pdf from 2018.
Text says "USN - UCAS - FAA-XX" but the shape makes me think about the nice assumptions, calculations & creations in this (USAF F-47) thread.

Most probably the image has already been shared somewhere on the forum before (?) but I can´t remember and there are way too many posts about PCA, NGAD, F-47, F/A-XX, etc. for me to go through to check...

That FAA-XX UCAS is pretty old. I've seen pics of it around years ago.

 

[Reddington777]

The powers that be will not like having the inlets visible through the landing gear doors, so there's a physically separate bay from the inlets. Yes, that adds weight, but it also adds strength.

Yeah I just haven't modeled it, but the wheels should be in a bay. All these numbers aren't even counting the distance to the separating walls, which I also have no idea how thick they may be.

I just flat think that the distance between the engine centerlines is too close. Need to scale things up a bit.

As I drop the volume, I'm starting to think there's basically only one configuration that's viable on a sub 80m3 stealth fighter and that's the F-22 configuration where you have your weapon bays tucked under your intakes. You can do it the YF-23 way, but that means you'll have sections of airframe with some deep trenches in between those sections of your airframe.

What I think could work is to have something akin to the J-36, which is two narrow, tandem middle bays for the two SiAW. Then adjacent to the narrow middle bays are two flatter, but wider bays to hold the AAMs in. This way, there's also no interference between dropping those AAMs. The planform I'm working with also happens to have a lot of unused space under the intakes. This would also allow me to center the engines a bit more to fit the aft fuselage contours and also create space for the main landing gear stowage bays.

Edit: Like this:

The intakes currently cut through the bay, but I'm going to make the bay conformal around it. The tip of the AIM-260s have 3.24 inches of clearence with the wall of the intakes, so counting the bay walls, something like 1-2 inches of clearance with the intakes. The central bays have a 3.4 inches of clearance with the widest most point of the engine. It's also got plenty of depth and headroom for whatever goes there. This also let's you decide to carry either SiAW/AARGM-ER or some future LRAAM for the center bays while guaranteeing six AAMs no matter which load out you carry. If you really wanted to go crazy with it, you could stick two more sidewinder bays on the side and switch out the center bays for AAMs as well for a total of 10 missiles.

The wheels now have much more breathing room and enough space for a wheel bay and the engines fit better with the tightest bulkhead. The best part is that all of this seems as of now comfortably packaged in 84m3 and could possibly be reduced down to 78m3, which also works with the density that @VTOLicious arrived at.

What was the distances between the engines and weapons bay of the A-5 again? I'd probably use that as the minimum viable.

Not sure. I was using the Su-57 as reference, but not sure how much actual distance is between the bay and the engines here.

Edit: what do those dimensions look like if you make the beast 68ft long?

6.3 inches.

But that has an 105m3 volume. My J-36 referece (assuming max thrust is 80-84% of MTOW, 3x 35,000k lbs engines, 130klb MTOW) has a density of 497.75kg/m3 for the J-36 reference. With that density, The most volume I can reason away with for 96klb MTOW is only 87m3.

 

[flateric]

That FAA-XX UCAS is pretty old. I've seen pics of it around years ago.

1997 at latest

 

[targetpractice]

1997 at latest

What an intriguingly weird thing.

And the dihedral, again. This makes me wonder if the bird of prey dihedral really was just a cost saving solution.

 

[Reddington777]

Such an extreme dihedral anhedral seems to have only found a place amongs UCAVs

 

[VTOLicious]

@Reddington777

F-23A cross section"R" (engine face)... *Measurements in mm

 

[Michel Van]

i just wonder
since Boeing merge with McDonnell-Douglas
Could F-47 based on JAST 7 concept by McD-D ?

 

[Scott Kenny]

X102/3 was said to be scaled down from AETP, which was supposed to fit the F135 form factor, but who knows if that's length? width? both?

Form factor means "fits within all the same maximums", so that's max width/height, diameter, and length.

Yeah I just haven't modeled it, but the wheels should be in a bay. All these numbers aren't even counting the distance to the separating walls, which I also have no idea how thick they may be.

Call it 1" for each wall as a minimum, more like 2" if it's load bearing. And that leaves very little access for assembler's hands and tools.

As I drop the volume, I'm starting to think there's basically only one configuration that's viable on a sub 80m3 stealth fighter and that's the F-22 configuration where you have your weapon bays tucked under your intakes. You can do it the YF-23 way, but that means you'll have sections of airframe with some deep trenches in between those sections of your airframe.

What I think could work is to have something akin to the J-36, which is two narrow, tandem middle bays for the two SiAW. Then adjacent to the narrow middle bays are two flatter, but wider bays to hold the AAMs in. This way, there's also no interference between dropping those AAMs. The planform I'm working with also happens to have a lot of unused space under the intakes. This would also allow me to center the engines a bit more to fit the aft fuselage contours and also create space for the main landing gear stowage bays.

Edit: Like this:
View attachment 795446
The intakes currently cut through the bay, but I'm going to make the bay conformal around it. The tip of the AIM-260s have 3.24 inches of clearence with the wall of the intakes, so counting the bay walls, something like 1-2 inches of clearance with the intakes. The central bays have a 3.4 inches of clearance with the widest most point of the engine. It's also got plenty of depth and headroom for whatever goes there. This also let's you decide to carry either SiAW/AARGM-ER or some future LRAAM for the center bays while guaranteeing six AAMs no matter which load out you carry. If you really wanted to go crazy with it, you could stick two more sidewinder bays on the side and switch out the center bays for AAMs as well for a total of 10 missiles.

The wheels now have much more breathing room and enough space for a wheel bay and the engines fit better with the tightest bulkhead. The best part is that all of this seems as of now comfortably packaged in 84m3 and could possibly be reduced down to 78m3, which also works with the density that @VTOLicious arrived at.
View attachment 795448

The mere fact that there's lots of unused space under the intakes strongly suggests that this is where at least a few bays are.

Not sure whether the USAF would want to keep the Sidewinder bays or use that for avionics, both have their good arguments.

I don't think that the centerline weapons bays would be as deep as you're modeling, I'm thinking not more than 2x SiAW stacked vertically and the rest of it is fuel volume. Maybe just the one SiAW and the rest is fuel.

Not sure. I was using the Su-57 as reference, but not sure how much actual distance is between the bay and the engines here.
View attachment 795440

That's a picture very close to flat on, do we have the length of any of those missiles?

Su57 and A-5 Vigilante are probably the two best points of comparison for the F-47, IMO.

6.3 inches.

But that has an 105m3 volume. My J-36 referece (assuming max thrust is 80-84% of MTOW, 3x 35,000k lbs engines, 130klb MTOW) has a density of 497.75kg/m3 for the J-36 reference. With that density, The most volume I can reason away with for 96klb MTOW is only 87m3.

Ah, yeah, that throws a monkey wrench into the works.

But only ~85-90m3? oof. So hard to make everything fit!

i just wonder
since Boeing merge with McDonnell-Douglas
Could F-47 based on JAST 7 concept by McD-D ?

Certainly possible, though there'd be a whole lot of adjustments overall.

 

[F119Doctor]

Going off of wikipedia numbers:

F135: Diameter: 46 in (1,170 mm) max., 43 in (1,090 mm) at the fan inlet
F119: Diameter: Approx. 40 in (100 cm) inlet, 48 in (120 cm) overall, 50 in (130 cm) maximum

The language is sorta vague but F135 seems to have a wider inlet while F119 is wider overall.

Length wise, F135 is larger.

X102/3 was said to be scaled down from AETP, which was supposed to fit the F135 form factor, but who knows if that's length? width? both?

Wikipedia is wrong - the maximum diameter of the F119 is not larger than the F135. I don’t have exact figures, but horizontal maintenance on the F119 is performed on the standard USAF 3100 work rails with a 48” spacing, and the engine fits within that spacing. The F135 can be transported on a standard 3000E trailer with 48” rail spacing, but the transportation adapter hangs over the rails. Any horizontal maintenance is done on work rails with 60” spacing to allow space for the support adapters.

The maximum “diameter” of the engines is larger in the vertical direction with the gearbox and control components mounted primarily on the bottom. The F135 gearbox is significantly larger than the F119, having multiple airframe components (generator, hydraulic pump) hard mounted to the gearbox, while on the F-22/F119 they are remotely mounted on the Aircraft Mounted Accessory Drive gearbox (AMAD) which is driven via a PTO shaft from the engine gearbox. AMAD accessories make engine replacement much easier, but is a weight penalty vs direct mounting to the engine gearbox.

 

[Dreamflyer]

That FAA-XX UCAS is pretty old. I've seen pics of it around years ago.

1997 at latest

Thanks!
I vaguely remember having seen that one render with the front-views (2nd image posted by Sferrin) in a magazine back in the 1990s, not the other ones. Also didn´t know until now about the existence of the old thread linked by Flateric.
Bit strange that "FAA-XX" term and shape from the 90´s was still used in documents ca. 7-8 years ago, as option for a high-end UCAV for near-peer warfare in a 2035+ timeframe.