Design Challenge: Lightweight Multirole Fighter (LMF)

[kqcke for you]

Different method and purpose. HARV created vortices at the nose with strakes, whereas I try to avoid those with slats.

You want to avoid them because then a dorsal intake where possible? Or it we're better for one? My brain works as good as the German Tiger fleet xD

 

[VTOLicious]

You want to avoid them because then a dorsal intake where possible? Or it we're better for one? My brain works as good as the German Tiger fleet xD

When you look at the attached pic you see the F-22 at high AoA. The sharp edges on the sides of the nose fuselage create vortices / turbulent air. Now if the F-22 would have a dorsal intake this turbulent air would be ingested by the engine.

You want to avoid that!

The slats I've introduced are intended to smoothen the airflow around the nose fuselage and supply the engine with a uniform airflow at higher AoA.

 

[kqcke for you]

Thanks now even i understand it.

 

[carvalho2008]

I'm starting to like this idea and made some concept sketches... The slats smoothen the airflow and guide it over the canopy towards the intake, whereas the LERX create a strong vortex lateral of the intake.
View attachment 709040
View attachment 709041

Master VTOLicius, it seems more complicated than my ventral grill, but if you still insist on mixing and use these slats as collectors for the grill itself??...where does the small, flat duct run to the back?...after all, it It does not need to be responsible for 100% of the engine's intake, just the complementary fraction of the loss in typical situations....this does not necessarily change the upper design of the front section if the duct is flattened following the design of the fighter...it would be viable ?

 

[red admiral]

The slats I've introduced are intended to smoothen the airflow around the nose fuselage and supply the engine with a uniform airflow at higher AoA.

You want to avoid vortex ingestion into the intake in a range of angle of attack and sideslip conditions but there are multiple ways of achieving that. I think that sideslip is probably the more critical case which leads to a need to stop the windward vortex moving too much - hence making it stronger by sharpening or higher sweep angle or trapping it (e.g. vortex flap). Also physically moving the vortex further outboard.

As well as passive shaping and physical effectors like a slat, then there's also flow control effectors e.g. forebody blowing

 

[VTOLicious]

Master VTOLicius, it seems more complicated than my ventral grill, but if you still insist on mixing and use these slats as collectors for the grill itself??...where does the small, flat duct run to the back?...after all, it It does not need to be responsible for 100% of the engine's intake, just the complementary fraction of the loss in typical situations....this does not necessarily change the upper design of the front section if the duct is flattened following the design of the fighter...it would be viable ?

Dear carvalho2008, please don't call me Master. That's kind of weird... and I have no idea what you are talking about, to be honest.

Anyhow, I can only repeat what I said numerous times: In my humble opinion the proposed "ventral grill" isn't a feasible solution to the problem.

 

[carvalho2008]

Dear carvalho2008, please don't call me Master. That's kind of weird... and I have no idea what you are talking about, to be honest.

Anyhow, I can only repeat what I said numerous times: In my humble opinion the proposed "ventral grill" isn't a feasible solution to the problem.

ok, sorry for my poor english. I believe this has created a difficulty in perceiving the texts. I really liked your project.

In this last text, I referred to the fins on the front section that you are proposing. It was a suggestion... from what I understand, you suggest creating fins that detach from the body and separate the vortex, creating a new layer. I don't know if I understood correctly. My question would be if you opened just the bottom part of the fin so that it collects air into an airflow duct that extends from the canopy to the engine air intake. This is what I tried to ask with the illustration above. Wouldn't that duct be enough? I understand that this structure is close to the canopy....

 

[Scott Kenny]

You want to avoid vortex ingestion into the intake in a range of angle of attack and sideslip conditions but there are multiple ways of achieving that. I think that sideslip is probably the more critical case which leads to a need to stop the windward vortex moving too much - hence making it stronger by sharpening or higher sweep angle or trapping it (e.g. vortex flap). Also physically moving the vortex further outboard.

As well as passive shaping and physical effectors like a slat, then there's also flow control effectors e.g. forebody blowing

IIRC, the F18 HARV used a pair of air vents up forward to help control the vortices at 55+deg AoA, over and above the big Hornet LERXs.

 

[VTOLicious]

Wouldn't that duct be enough?

No.

Turbulent air ingested by the main intake is the issue.

 

[VTOLicious]

IIRC, the F18 HARV used a pair of air vents up forward to help control the vortices at 55+deg AoA, over and above the big Hornet LERXs.

@red admiral Forebody blowing is indeed an option to consider. I'm keen to see if NGAD or any other 6th generation fighter will feature dorsal intakes and maybe some novel means to control vortices and guide air to the intakes.

 

[MadRat]

Chisel point noses and chined fuselages act as LERX in modern stealth aircraft.

F-35 has used the genius idea of making the outer edge of its intake sweep forward to leverage the chine segment that was otherwise broken at the intake. Like on an F-15 it creates an oblique shock in the inlet that slows the air flow, and variable area throats (using moving diamond-shaped ramps) help to further optimize it. Unlike the F-15 your ramp reflective signature is virtually non-existent using a combination of angles and materials

 

[helmutkohl]

while I really like the FAR 21 design..
since then, we now have the Bayraktar Kizilelma
which seems roughly more or less the same size. 1 large bay. both around 14.5-7 meters long
the key difference is Kizilelma is unmanned and perhaps cheaper? since its made by Turkey, I assume it to be NATO compatible
Engine might be underpowered

 

[VTOLicious]

while I really like the FAR 21 design..
since then, we now have the Bayraktar Kizilelma
which seems roughly more or less the same size. 1 large bay. both around 14.5-7 meters long
the key difference is Kizilelma is unmanned and perhaps cheaper? since its made by Turkey, I assume it to be NATO compatible
Engine might be underpowered

While Kizilelma-A is about the same size one should not forget that it is a subsonic design, hence much lighter as well (MTOW 8500 kg).

 

[Goha]

View attachment 709084
When you look at the attached pic you see the F-22 at high AoA. The sharp edges on the sides of the nose fuselage create vortices / turbulent air. Now if the F-22 would have a dorsal intake this turbulent air would be ingested by the engine.

You want to avoid that!

The slats I've introduced are intended to smoothen the airflow around the nose fuselage and supply the engine with a uniform airflow at higher AoA.

You cannot get rid of the nose vortex strand using such slats - it will in any case end up in the upper air intake (compensated by measures for the gas-dynamic stability of the engine compressor, for example, a controlled inlet guide vane).

 

[Scott Kenny]

You cannot get rid of the nose vortex strand using such slats - it will in any case end up in the upper air intake (compensated by measures for the gas-dynamic stability of the engine compressor, for example, a controlled inlet guide vane).

Not getting rid of the nose vortex, just keeping it out of the inlet.

 

[Goha]

Not getting rid of the nose vortex, just keeping it out of the inlet.

It won’t work, the vortex moves depending on the sliding angle.

 

[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

 

[riggerrob]

T

he key difference is that NASA’s X-59 is optimized for supersonic cruise at shallow angles-of-attack. It will only fly at moderate nose-up angles-of-attack - at slow airspeeds - during landings and take-offs.

 

[VTOLicious]

T

he key difference is that NASA’s X-59 is optimized for supersonic cruise at shallow angles-of-attack. It will only fly at moderate nose-up angles-of-attack - at slow airspeeds - during landings and take-offs.

Exactly!

 

[Foo Fighter]

Have thewre been any designs with both ventral and dorsal intakes at all? Possibly opening or closing these depending on need might work.

 

[Manuducati]

Have thewre been any designs with both ventral and dorsal intakes at all? Possibly opening or closing these depending on need might work.

I've had this in mind for ages as well. Bottom intakes open only for takeoffs, landings and WVR combat where high AoA is more common, conventional upper intakes for high altitude cruise and maximum stealth.
Something like a larger Saab 35 Draken, with flush intakes above and retractable ones under the thicker part of the double-delta wing. Kind of an upside-down MiG-29 louvers concept.
Of course that would require several moving parts and some challenge with the boundary layer and airflow...

 

[riggerrob]

I've had this in mind for ages as well. Bottom intakes open only for takeoffs, landings and WVR combat where high AoA is more common, conventional upper intakes for high altitude cruise and maximum stealth.
Something like a larger Saab 35 Draken, with flush intakes above and retractable ones under the thicker part of the double-delta wing. Kind of an upside-down MiG-29 louvers concept.
Of course that would require several moving parts and some challenge with the boundary layer and airflow...

MiG-29 has the opposite with main engine intakes below the wings and auxiliary intakes on top of the wings. Those auxiliary intakes are primarily used during take-off to reduce the amount of foreign object debris sucked into engines during ground runs.

Cessna’s A-37 Dragonfly had retractable intake screens for the same reason: reducing the amount of gravel sucked in during ground runs.

 

[Manuducati]

I know, the analogy was for the general concept of dual/alternative intakes, not their specific use. But thanks.

 

[Basil]

This is a Swiss concept from 2016 under the design leadership of Georges Bridel (see also his earlier Piranha concept) for a most cost efficient supersonic capable small training- and air-policing aircraft:

https://www.alr-aerospace.ch/publications/Bridel,%20G%20Janus%20Concept,%20SMi%20Conference,%20London%20September%202016.pdf

 

[VTOLicious]

This is a Swiss concept from 2016 under the design leadership of Georges Bridel (see also his earlier Piranha concept) for a most cost efficient supersonic capable small training- and air-policing aircraft:

https://www.alr-aerospace.ch/publications/Bridel,%20G%20Janus%20Concept,%20SMi%20Conference,%20London%20September%202016.pdf

Interesting! Never seen this one before.
However, it is really small and doesn't feature internal weapon bays.

 

[Scott Kenny]

Interesting! Never seen this one before.
However, it is really small and doesn't feature internal weapon bays.

Wow, that is TINY!

 

[Suricato]

This is a Swiss concept from 2016 under the design leadership of Georges Bridel (see also his earlier Piranha concept) for a most cost efficient supersonic capable small training- and air-policing aircraft:

https://www.alr-aerospace.ch/publications/Bridel,%20G%20Janus%20Concept,%20SMi%20Conference,%20London%20September%202016.pdf

With the small distance between wing TE and elevator LE: Is it possible to recover the aircraft from a deep stall?
With the experience from NH90: How many military costumer like an airplane with 50% composite?
...

Some costumer may have weapon pylons on a lightweight multirole fighter. So an FA-50 or an armed T-7 would be more realistic.

 

[Scott Kenny]

With the small distance between wing TE and elevator LE: Is it possible to recover the aircraft from a deep stall?

Deep stalls happen when the wing blocks airflow to the elevator. With the elevator position, there's basically no flying situation that this plane can get into a deep stall.

With the experience from NH90: How many military costumer like an airplane with 50% composite?

Not any different from one that's 40% composite, which describes most aircraft today.

Some costumer may have weapon pylons on a lightweight multirole fighter. So an FA-50 or an armed T-7 would be more realistic.

The whole point of this thread was to find out the minimum size stealthy fighter. Which means no external pylons.

 

[carvalho2008]

MiG-29 has the opposite with main engine intakes below the wings and auxiliary intakes on top of the wings. Those auxiliary intakes are primarily used during take-off to reduce the amount of foreign object debris sucked into engines during ground runs.

Cessna’s A-37 Dragonfly had retractable intake screens for the same reason: reducing the amount of gravel sucked in during ground runs.

 

[carvalho2008]

 

[Pioneer]

VTOLicious, now I just woke up this morning with the urge to revisit this thread.....
Have to say, I still can't help being impressed with your design and everyone supporting efforts.

Now, I might be taking your intention beyond your realm, but if I recall, you alluded that your LMF was intended for small air forces. In the case of your LMF, do you envisage the designer/builder to be a new aerospace entity or one of the big boy corporations building your LMF?
Now appreciating the games that the U.S. government has been exercising with allowing/blocking the sales of aircraft to given countries due to their U.S. centric technologies/content - in your case VTOLicious the General Electric F404/F414 turbofan. Do you think there's scope of marketing diversity in offering a choice of engines to fit customer requirements, which negates such U.S. government games/manipulation in offering/selling your LMF to the world on a true worldly scale - aka countries not geopolitically inline with the U.S.?

Perhaps a common intake ducting arrangement that facilitates the F404, Snecma M88-4e, European EJ200, Klimov RD-33MK, Klimov RD-93/93MA or
Guizhou WS-13 turbofans.

A universally adaptive engine mount arrangement to allow the fitting of F404, Snecma M88-4e, European EJ200, Klimov RD-33MK, Klimov RD-93/93MA or
Guizhou WS-13 turbofans.

I fully appreciate that this would effect every inch of space and time and effort you've thus far contributed to your design. But just a nagging thought.

Regards
Pioneer

 

[kqcke for you]

Perhaps a common intake ducting arrangement that facilitates the F404, Snecma M88-4e, European EJ200, Klimov RD-33MK, Klimov RD-93/93MA or
Guizhou WS-13 turbofans.

I think this should be easy to do (but i could be wrong)

A universally adaptive engine mount arrangement to allow the fitting of F404, Snecma M88-4e, European EJ200, Klimov RD-33MK, Klimov RD-93/93MA or
Guizhou WS-13 turbofans.

That is a hard thing as all pipes and co. would need to be the same so you could use them and they need to be the same diameter or have an adapter but that needs space.

 

[Pioneer]

I think this should be easy to do (but i could be wrong)

That is a hard thing as all pipes and co. would need to be the same so you could use them and they need to be the same diameter or have an adapter but that needs space.

Thanks for your reply kqcke for you.
Yeah, I appreciate my notion wouldn't be simple, let alone straight forward. Maybe VTOLicious encompassing fuel tanks around the engine might require to be custom-made to allow for the said differences in "all pipes and co" differences in engines?

Again, just a notion that's nagged me all day.

Regards
Pioneer

 

[kqcke for you]

Thanks for your reply kqcke for you.
Yeah, I appreciate my notion wouldn't be simple, let alone straight forward.

Yeah it would be easier for future engines being build to fit the aircraft/ those dimensions.

Maybe VTOLicious encompassing fuel tanks around the engine might require to be custom-made to allow for the said differences in "all pipes and co" differences in engines?

The big problem is that to model this we would need to know everything about the engines. Where which pipe, wire and co. go into and out of those engines and the we would need to have some kind of universal connection / a adapter for each engine . I say its best to understand it if we take some cables for phones (or screws if you want) Lightning, USB C and the some others kinda look similiar but they have some difference. This ignores the different physical size each engine has which would be the next factor to look at.

Again, just a notion that's nagged me all day.

No problem mate. Its an interresting idea but hard to realise. Still mutch easier then what i friend of mine asked me as he wanted to know if one could build one aircraft frame and then have 2 different amount of engines which is really hard to do / close to impossible.