Stealth Aircraft + External Fuel Tanks/ CFTs?

[VTOLicious]

Recently it was revealed that the F-22 will receive stealthy external fuel tanks.


However, what if external fuel tanks would be considered in the design of a LO-airframe from the onset?

Could such a fuel tank keep the impact on the RCS to the absolute minimum, or maybe wouldn't have an impact on RCS at all?
Maybe something like the F-15 CFTs? Or rather wing mounted tanks (CFTs?) that can be jettisoned as necessary?
Would it be worth to consider?
Are there any public available studies?

 

[kqcke for you]

I would guess that Have Dash II could considered as a study of the concept.

 

[raptor82]

26DMU, w/o dorsal CFT：

 

[raptor82]

Some expandable fuel tank designs：

Boeing：

MDC：

Northrop：

 

[Archibald]

And then comes the all too obvious question: could you hide an AIM-174 in such tanks ?

 

[VTOLicious]

This thread is first and foremost about fuel tanks and not about pods to carry missiles. However, I think everyone may agree such fuel tank pods could be used for other purposes as well.

 

[VTOLicious]

I think side mounted CFTs like on the F-15 would be most useful. In contrast to dorsal mounted CFTs (e.g. F-16) the installation/removal is easier. And, in relation to the post above, they could be exchanged with weapon bays pods as well, if increased weapons loadout if prioritized over extended range/endurance.

 

[Scott Kenny]

I think side mounted CFTs like on the F-15 would be most useful. In contrast to dorsal mounted CFTs (e.g. F-16) the installation/removal is easier. And, in relation to the post above, they could be exchanged with weapon bays pods as well, if increased weapons loadout if prioritized over extended range/endurance.

You'd have to make the side-mounted CFTs not interfere with any weapons bay doors. And not interfere with any landing gear doors.

So I think the F-35 would require CFTs on top of the airframe, not on the sides. F-22 might be able to have some smaller CFTs on the sides, or CFTs at least twice that size on top.

 

[VTOLicious]

You'd have to make the side-mounted CFTs not interfere with any weapons bay doors. And not interfere with any landing gear doors.

So I think the F-35 would require CFTs on top of the airframe, not on the sides. F-22 might be able to have some smaller CFTs on the sides, or CFTs at least twice that size on top.

I'm not talking about retrofits. I made this thread to discuss options to include it in the design from the onset.
Would it be worth to consider for one of the 6th generation fighters currently in development (NGAD, GCAP,...)?

 

[VTOLicious]

Some expandable fuel tank designs：

Boeing：

MDC：

Northrop：

I doubt technology is there yet. Especially for supersonic fighters. If so, it would be the perfect solution!

 

[VTOLicious]

26DMU, w/o dorsal CFT：

Interesting! Haven't seen that before.

 

[paralay]

What prevents you from immediately making a more complete fuselage and not hanging these "crutches"?

 

[VTOLicious]

What prevents you from immediately making a more complete fuselage and not hanging these "crutches"?

You could ask the same question for legacy combat aircraft. Additional fuel tanks are means to extend range / endurance as required (without being dependent on a tanker aircraft).

 

[paralay]

Is this some kind of self-deception or a way to get the next tranches for an old plane

 

[VTOLicious]

Is this some kind of self-deception or a way to get the next tranches for an old plane

I don't know what you mean with self-deception. Did you actually read post #1?

 

[paralay]

In my opinion, there is no place for conformal tanks in the Raptor design. It's physically impossible. The only way out is to replace the wing with the possibility of suspension of four external tanks, as was originally intended

 

[VTOLicious]

In my opinion, there is no place for conformal tanks in the Raptor design. It's physically impossible. The only way out is to replace the wing with the possibility of suspension of four external tanks, as was originally intended

I agree. This conclusion is basically the reason for this thread's existence
I used the Raptor as an example, which did NOT take CFTs into account in its design.
But if we design a new stealth fighter, what would be the best solution?

 

[paralay]

To lay down the required internal volumes at the early stages of design. Su-27, tank capacity 30%, range 3680 km. Su-35S, the volume of electronic equipment has been reduced, the brake shield has been removed, and the volume of tanks has been increased by two tons. The range of action, with a higher take-off weight, is increased by 9%
The external theoretical outline has not changed much. RCS, without external weapon suspensions, reduced by half

 

[kqcke for you]

I agree. This conclusion is basically the reason for this thread's existence
I used the Raptor as an example, which did NOT take CFTs into account in its design.

Well if Raptor would have a landing gear that does not go trought the CFT space it would work. Or they CFT has a door for the landing gear/ a door for the landing gear and the original door for it.

But if we design a new stealth fighter, what would be the best solution?

For example a landing gear like hornets which is stored "vertical" in the fuselage and not like F-22's which goes horizontal into the Wing.

 

[VTOLicious]

Well if Raptor would have a landing gear that does not go trought the CFT space it would work. Or they CFT has a door for the landing gear/ a door for the landing gear and the original door for it.

For example a landing gear like hornets which is stored "vertical" in the fuselage and not like F-22's which goes horizontal into the Wing.

Exactly.

There is actually a stealth airframe out there with a main landing gear arrangement that would theoretically allow the installation of F-15 style CFTs...

 

[VTOLicious]

This thread is first and foremost about fuel tanks and not about pods to carry missiles. However, I think everyone may agree such fuel tank pods could be used for other purposes as well.

For instance, internal carrige of weapons was proposed for the Silent Eagle...

 

[Scott Kenny]

For instance, internal carrige of weapons was proposed for the Silent Eagle...
View attachment 735065

There's very little fuel in that one, however. The IWBs eat almost all the volume that holds fuel in the standard CFTs. There's volume for fuel at the very front, and at the back (though I'm not sure the standard CFTs hold fuel that far back).

 

[riggerrob]

Boeing built a mock-up of a faceted "stealthy" center tank/external bomb-bay for F-18D, but I do not know if they test-flew it.

 

[Scott Kenny]

Boeing built a mock-up of a faceted "stealthy" center tank/external bomb-bay for F-18D, but I do not know if they test-flew it.

I think the EWBP (External Weapons Bay Pod) was all bay volume, no fuel.

 

[Wahubna]

The F-35 and F-22 already have conformal fuel tanks....they are in the airplane! As the F-35 and F-22 designers told me...

Their OMLs were shaped to fit in as much gas as possible given the other mission constraints. 5th gen is not like 4th gen where a 4th gen aircraft carries practically everything external. 5th gen is intended to carry as much as possible INTERNAL.

Now for non-stealthy platforms it makes sense. Their OMLs are usually shrink wrapped around the absolute bare essentials with the assumption being they would carry external tanks frequently. A naked F-16 has practically nothing to it. Its fuselage cross section is barely anything other than engine.

So a subtle way to tell if there is probably system level benefit to an aircraft from CFTs is to look at fleet activity. How often do they carry external tanks? If they carry them often, it would probably make a lot of sense to make those often-carried tanks lower drag and molded onto the airplane to free up pylons.

 

[VTOLicious]

The F-35 and F-22 already have conformal fuel tanks....they are in the airplane! As the F-35 and F-22 designers told me...

Apparently not, see first post

 

[Wahubna]

Apparently not, see first post

I would like to point out that is not a current operational config and that aircraft are a system of systems. Meaning put bluntly it is in reality complicated and nuanced. Current operational, combat config is sans tanks. As in yeah they wear tanks to fly formation with Bears but in that case there is an extra win of obscuring its real signature and that mission is about endurance.

Much has been discussed about the F-22s range so I'll refrain from beating that dead horse....but at some point just go design a new plane and give it the range you want.

In general if you are approaching a clean-sheet with the intention of adding CFTs you probably need to reconsider your requirements and sizing. It's cheaper and easier to just stuff it in the plane.