Twin-Tail J-18

[PolluxDeltaSeven]

Hello everybody!!

I know the following is not a real twin-booms or even a classical twin tail...
It's even not a model!! (not yet )

But I hope you like it

It's something I draw few weeks later in the TGV (train between Paris and Lyon). I scaned it and modified a little with Photoshop...




For the short story, this plane is the prototype of the CAC J-18, a little cheap fighter build by the Asian Alliance from 2016, to counter the NATO  Sea Star in Pacific and Indian Oceans...

This light fighter is a STOL plane, able to take off in 150m in fighter mission, and to landing in less than 100m (specially after fuel and weapons used)...
For that, the horizontal tail is used to aim the engines' jet to the high, and a part of the jet is derived between the air intakes to lift the plane's nose...
Retractable canards, inspired by the "Mirage III Milan", are also used on the operationals planes... The engines are also biger and more powerful than those on this prototype...

Used on some modified cargo and tanker ship (like the Royal Navy did during Falklands War), the J-18 is able to operate take off with less than 70m for a ship protection mission...

In 2018, a specific version of the J-18, the J-18Y appeared specially to those carrier operations, with more powerful jets and more capable STOL abilities...

Operate during the "Big One" War from 2017, the J-18 was the biggest ennemy for the Sea Star Squadrons. The two fighters are made for operate from both the little islands and the sea and they became the symbol of this war, exactly as the Spitfre and the Me-109 or the Zero and the Corsair for the WWII...

[Tophe]

I hope you like it

I like it very much.
To understand plainly the design, I think we would enjoy 3 extra explanations:
- as the fins seem lateral, what is the central rear part? A tube to hold more solidly the tail? a tube providing to the rear some pressured air to stabilize the STOL mode?
- is the wing rhomboïdal with the rear part going upward and the front part going downward? (a front view would help, but it is not easy, I understand, to be coherent within the 3 views...)
- what is at the rear of the booms, a kind of radar or rear weapon?
These are just extra questions to appreciate fully, but the main conclusion is: great!

[PolluxDeltaSeven]

Ok, I have something to do tonight, but I will explain the things tomorrow

[Tophe]

Thanks, and remember: there is no hurry at all, this is a hobby
By the way, a 4th question that stroke me while sleeping (yes: I dreamed of your Commonwealth J-18!): how would you prevent the tailplanes to be burnt by the jet exhausts?

[elmayerle]

Let me try answering Tophe's questions and see how close I get:

1)  The middle "boom" between the engines likely is there for structural reasons and to all the engine exhuast flows to be diverted separately.

2)  It's a joined-wing configuration, that's why it looks a bit peculiar.

3)  I'd argue for an aft-facing radar, or at least a substantial RHAW fit as well as other suitable sensors.

4)  I would assume either a careful choice of materials or careful leading edge blowing that keeps the exhuast flow from directly impinging on the tail surfaces.

Overall, it reminds me of a Northrop PD study from around 1982 that I saw while there.

[PolluxDeltaSeven]

I'm back!


For the question you ask, Tophe, Elmayerle done some good answer  



1°
For the central "boom", it's not a tube, because the "boom" has a rectangular section, like the F-22's one...
It's a sort of fin board, used for structural reason, indeed...
With those central "boom", if a reactor has a problem, a reduce flow for example, the dedicate part of the tail could act to reduce the problem, because the two parts of the tail are independents and more robust.
Because of this tail independent, the plane is also more viable after battle damage: if an IR missile or a gun shot destroys one engine and the dedicate tail, the plane is still under control.
The third reason of such a central boom is that the chinese are (in 2020) building 3 real carrier vessel, little one with "ski jump" deck, as the Kusnetsov... A lot of J-18 will be modified with a cross for the classical landing on this new CV, and the cross will be under this liddle boom

2°
You are right, Tophe, the wing is rhomboïdal, a joined wing configuration, as Elmayerle said...
At the begining, I thought about parallel wings, but the drawing was a bigger challenge with joined wings. So the real reason was fun.
But I can imagine that such a configuration, even if it's more difficult to build, is more robust. I also thought that joined wings could cancel the bad effects of the "flèche inversée" back wings (really bad in supersonic and transonic speeds)

I'll post a front view, but it's just a scan of the real initial draw, there is some incoherence with the other views


3°
Interresting...
I first thought about rear weapons, like self-defense Stinger...
But I imagine other...

Of course, one of the rear booms is used to a self-defense radar. With some electronic pods carried at the wing's end, the plane could have, like the Su-47 or the canceled russian T-50, a 360° detection ability in air-to-air missions...
But I think that the rear booms could have some modular systems...

For example, one or two radar, a MAD system for ASW missions, maybe some internal fuel tanks, to increase the range in escort missions etc...
I also thought about a new self-defense system: imagine a little flying sphere with some pulse engines and IR detectors all around it: 20 or 30 of those spheres could be carried and each sphere could intercept an air-to-air or SAM missile, using its engines and detectors to stand between the missile and the plane to protect, and able to explode an ECM charge when the missile is at range and the J-18 far enough...
I don't know you understand what I mean... My English is not good enough to translate what I think (ask me Tophe if you want a PM to explain in French )


That's why I imagine that the type of rear loads could be adapted on the misison. For example a Self Defense Sphere Systeme and a MAD for sea convoys attack, or two SDSS for ground attack missions with no ennemi fighters to deal with but a great SAM activity... etc ...


4°
Oh!! you dream of my new baby??
 

I will simply prevent the tail  to be burnt in using the same material that the engines are made
I don't know if it's possible, but we also could imagine for long range and long time misison a system of internal refreshing, using the internal fuel or azot, but for me, if you choose the good material, as elmayerle said, there is no problem...



Oh!! Elmayerle, I don't know what is "RHAW" and what the Northrop PD are??
It interest me a lot

[PolluxDeltaSeven]

And there is the front view!!

I draw it before the two other, so there is possibly some error, but the whole idea is here






And there is the internal view of the STOL rear system... (the front system is the "canards" and the part of the jet flow ejected between the air intakes...):




As you can see, the tail is drown in the flight configuration (horizontal) and in take off config (jointed and oblique) in the same drawing...
The large grey part is the central boom, also used to protect and separate the engines from explosion etc...

[Tophe]

Great!
Just confirm: there is no PC? (the tailplane would be burnt away...) and the jets are 'double-flux' (in French, 'bypass' maybe in English) to mix burnt hot gas with pressured cool air...
It will work, maybe before the XXIInd Century...  

[PolluxDeltaSeven]

it is double-flux, but with afterburner...

If the Su-35/33/34 central boom is able to support such warmth in 1990, why not a chinese tail in 2020???  
Idem for the F-22's one... And remember the YF-23 with its engines on the upper fuselage, even with afterburner

After all, there is a lot of missiles that use this system (MICA, for example)



Of course, i don't think such a plane could exist in the real world. But in the Alternativ Universe I'm imagining, it is more credible that my Sea Star (link in first post)

[Tophe]

Another night then another dream about the J-18...
May our French designer PolluxD7 or our US engineer Elmayerle understand/explain me...
I present my uncomfortable thoughts: the jet push of a plane has 2 effects:
1- a main thrust moving all the plane as a whole against the external World
2- (for a rear oblique thrust) an internal move, rotating part of the aircraft around the centre of gravity
So your drawing with the rear tailplane giving direction to the thrust may have 2 effects:

If thrust directed upward:
1'- the general push is downward, needing more wing-lift thus speed to take off, opposite to Short Take-Off goal
2'- the tail is going down, the nose (and wing leading edge) is going up, so slowing down and more wing lift, OK for STOL
Contradiction... It would be better to have only 2' and the answer is a rotating wing like the F-8 Crusader's (of both US Navy and French Aeronavale). And joint biplane wings could make a deep improvement for that, all right, giving birth again to the F-8 dead-end.

If thrust directed downward:
1''- the general push is upward, providing lift, allowing to decrease the plane speed, OK for STOL
2''- the tail is going up, the nose (and wing leading edge) is going down, so less lift and more speed is necessary to prevent stall, opposite to STOL goal
Contradiction... It would be better to have tilting jet pipes as close as possible to the center of gravity, and your layout allows this, as requiring rear booms to hold the tail while the jet pipes are rather far front (like on the Yak 141 VTOL).

So I think a Yak-141/F-8 mix named J-19 – more twin-tail to please me even further! – would win the contract and the J-18 would loose...

[Hobbes]

Interesting idea! I've been playing with a STOVL derivative of the Flanker myself: my plan was to move the exhausts forward, much like your design, and replacing the nozzles with Yak-141 rotating nozzles. I'd then add cold exhausts near the intakes (either as Harrier-style rotating nozzles, or with louvred doors in the bottom of the intake ducting) to balance the aircraft.  

[PolluxDeltaSeven]

Hello !!

The main of a upward directed thrust is to play with the position of the plane...
With upward directed thrust at the rear of the plane and a downward directed thrust at the front part of the plane (you can see the nozzle between the air inlets on the front view), you can directly act on the position of the plane around its center of gravity:
The rear part of the plane will go down, and the front part will go up... And the plane is in take off position faster than a classical jet...

I believe it the way the special F-15 (with F-18 horizontal tails as canard and thrust vectoring)  used to short take off... I just had some front downward thrust to add more STOL capacity)

But the other solution you tell is also a good one... For the J-19 (or J-18II) , there are just some modifications to do...
Of course, if the rear thrust is downward directed, the part of the front thrust had to be conciderably increased... If not only part of the plane to take off will be the rear part


But we of course could imagine that after 4 years of operational service for the STOL J-18, the PLAAF, PLANAF and the Asian Alliance want a real STOVL (yes, with all-downward thrust, I think Vertical landings are possible).
The CAC enginers work a lot and the first flight of the J-8II demonstrator takes place only 8 months after the PLAAF ask it...

While the more robust J-18 still act from all the little islands in Pacific and Indian Ocean, the J-18II of the PLANAF (named J-19 in PLAAF and F-19 in the Asian Alliance) replaced the classical J-18 on all the modified tanker ships and little improvised carrier...

The J-18II/F-19 could operate from more little ships as container chips instead of heavy and more useful tankers and the J-19 could be used as a tactical Close Air Support aircaft in the Siberian Front, even if the more simple and robust J-18 is still the first plane for the PLAAF...





Yes...
I could think about it a little more, but the idea is very good ! Thanks Tophe

Interesting idea! I've been playing with a STOVL derivative of the Flanker myself: my plan was to move the exhausts forward, much like your design, and replacing the nozzles with Yak-141 rotating nozzles. I'd then add cold exhausts near the intakes (either as Harrier-style rotating nozzles, or with louvred doors in the bottom of the intake ducting) to balance the aircraft.

Yeeeeah!!!
The biggest STOVL fighter ever build in the world!!!
I love the idea!!


Will it be used by the Russian Navy on the Kiev Class ships or for the Russian Air Forces as a close air support aircaft??

[proditor]

This is just an idea I had kicking around after looking at Trophe's J-19 derivative.  What if you removed the stabilzers and extended the diamond planform to the end of the booms?  Then you cover control, but have a slightly cleaner look.

Dunno if it would work, and I'm no good at Photoshop, so I'll leave it to one of our resident wizards should they feel so inclined.  

[PolluxDeltaSeven]

I could try

[PolluxDeltaSeven]

Et voila!!!

The right wing is modified, as you said...

I think a J-19 with such a wing could be faster, have more weapon's payload, more internal fuel and maybe a better turn rate...
It could be a good idea, for example for a J-19C (or J-18E or F-19C). 40 aircraft produced for the PLANAF as a medium range fighter-bomber and more than 200 units for the export market (Bangladesh, Pakistan, and other member of the Asian Alliance)



Oh!!

And as you can see, this J-19C prototype is presented with the canards spreaded...
Those canards are used on ever version of the J-18/19, but only for take off and landing...