Switchblade: designed flawed?

Ok, the thread title is a cheap trick. But when I look at the Switchblade concept as patented by Northrop Grumman I can immediately see a few things which, to my untrained eye, seem to present huge design challenges to the manufacturer, which when weighed against it’s perceived advantages make it look somewhat less than a top performer.

Would it be stealthy?
Well everyone seems to depict it in a charcoal black “stealth” look so it must be right? Clearly the above fuselage intake position and tailless configuration is intended to reduce RCS; there’s not really any other compelling explanation for those two features. However there are some obvious problem areas, particularly the wing/body intersection and the engine nacelles. I’ve done a rough sketch to show the problem areas from a lower quarter aspect:

The interface between the swing wings and body would be particularly hard to stealth as there is inevitably a gap between the wing and the fuselage. This image of an Su-24 Fencer shows the equivalent problem area:

The Switchblade essentially has that type of high-radar-return interface running halfway down the fuselage. It would be very difficult to make the interface with the build tolerances required in stealth designs.

Several stealth designs have conventional round jet exhausts but this is a trade-offfor stealth, particularly from the side and rear angles. The Switchblade also has an unstealthy rear rather than the stealthized exhausts like on the F-22 or X-45:


High agility?
People normally equate forward swept wings with high agility. A key feature of FSW is a reduction in aileron stall at high angles of attack allowing slower flight (shorter take-off/landing) and certain “super-maneuverability”. However, the patented switchblade configuration emphasized a top-of body intake position (although one configuration was shown with a belly intake) which would be blanked by the forward fuselage at high angles of attack.

The patent image does suggest that the canards (small airfoil surface forward of the wing glove) is a moving surface. However that would present a major challenge with the leading edge of the wing glove:

To reduce the stealth/aerodynamic problems the canard could be non-moving and blended in to form a single aerodynamic interface. This compariative image of the Sukhoi Su-47 in high angle of attack flight shows how the canards need to be at a lesser pitch than the main wing. If on the switchblade these can’t move, then the rearward swept canard would stall, causing a pitch-down of the nose:

This means that the switchblade could not maintain high angle of attack flight in the same way as the X-29 or Su-47 can. Together with the over-fuselage intakes and lack of vertical stabilizers I’d suggest that the switchblade is NOT an agile design.

Flight regime
People seem to believe that the switchblade is an inherently high speed design, often quoting mach 3. That is despite the relatively unswept nose and forward airfoil sections. We also have to consider the stresses on forward swept wings. These increase at speeds and angles of attack and place greatest stress at the wing root, requiring a heavier/stronger wing construction. On the switchblade this high stress area is also the wing pivot – so the stresses would be increased further(?). I’d suggest that the wing has to swing forward at relatively slower speeds meaning that the transonic drag advantage generally inherent in the FSW is not achieved. If the wing has to be swept forward even in subsonic cruise flight, how aerodynamically efficient would this aircraft be? –not very IMO.

Conclusion
I’m open to correction and counter-argument, but to me it looks like the switchblade is neither particularly agile nor stealthy, which casts real doubt on its relevance as a next generation combat aircraft. Just what could it do better than existing projects? – not a lot.

Secondary conclusion
My suspicion is that the switchblade patent is actually an attempt to stop others coming up with a potentially stealthy shape which still allows the highly efficient forward swept wings for slower speed flight – but which requires future/new technology top stealthize the swing wing feature. This logic would suggest that Northrop never intend to actually build switchblade in the exact form in the patent, just block others from exploring this line of thought which one day be possible.

Ref: Links to Switchblade patents:
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[edit on 4-4-2006 by planeman]

Pleasure to read as always...


I agree with you on the stealth factor... but flyin without tailless design can be pretty bad... Sure it gives better stealth... BUT, what about the stability...??

Santa Clause does exist... He lives here in Finland...


[edit on 4-4-2006 by Figher Master FIN]

Its never going to work your right.

Probably something a few guys came up with when they were smoking some 'whacky backy' some saturday night, and they decided to throw it into the public domain for people like us to mull over



The hinges will be impossible to hide to a radar, and the hinges will be impossible to make strong/light enough to handle a FSW design and keep a decent power to weight ratio.


As you mentioned, the aerodynamics are totally wrong for supersonics and low end hypersonics, and the engine intakes are masked at high alpha - all of which leads me to believe its a concept more for airfix than for the airforce.

Wow, an excellent study planeman , but do you think the professional aerospace companies that spend millions and employ hundreds and spend a lot of money to register patents overlook stuff that appear to be obvious design basics ? Perhaps there is more to it than what seems obvious ?

BTW, Russia have come out with their own switchblade equivalent concept.









[edit on 4-4-2006 by Stealth Spy]

StealthSpy, that looks like a joke design to me. What is the logic of having both forward swept AND rearward swept wings and why bring them together as a single wing????? and again, it's trying to look stealthy but ignoring the wing gloves. Has that come from a credible source?

Well its from a Russian site maintained by paralay, and the other information in his site seems credible and provides some cool scoops into russian projects. There are some inputs from Russian radar expert Paul Mead(a.k.a Overscan, Aerospacetech) in his site. Although Paul's shut down his site, he's transferred much of the details to the various sections of his own messageboard >> www.secretprojects.co.uk...


Anyway, there was an accompanying note with the Russian concept's pics which was translated by ATS member bios ...

It reads (posted with thanks to bios) .... the first part of the article just laments the old Soviet war machine that genrously funded weapon systems development.

Then the second part talks about the PAK FA and a large bomber called the T-50 OKB and their possible characteristics.

The article goes on to discuss future programs and what would constitute a 6th Gen aircraft - It says that such aircraft would probably be unmanned and that any manned 6th gen aircraft would most likely be an "airborne command post" directing the unmanned aircraft (UCAVs) to their targets.

The reference to the swing-wing configuration says this:
"For the purposes of flight service at low altitudes and for short takeoff and landing, the Multi-Purpose Fighter could be equipped with a variably swept wing."

Also the aircraft will allow for supercruising very efficiently.

At the end of the article it says that these aircraft projects stand "zero" chance of being built as it stands now, but even so optimistically places them entering service around 2020.

[edit on 4-4-2006 by Stealth Spy]

Paralay has updated his page ... and here is new pics in this very section:

www.paralay.narod.ru...

www.paralay.narod.ru...

www.paralay.narod.ru...

Originally posted by Stealth Spy
Wow, an excellent study planeman

, but do you think the professional aerospace companies that spend millions and employ hundreds and spend a lot of money to register patents overlook stuff that appear to be obvious design basics ? Perhaps there is more to it than what seems obvious ?

Yes, 100% sure. Sometimes designs can be forced onto the engineers for reasons other than performance.

Case in point - Boeing Sonic Cruiser. All the aero engs I know asked the same question as me when finding out about it "Why? Thats just stupid"

Well I think the design has a lot of answers that we don't know. I guess if we returned to the 70's and looked at Have Blue we would say, its impossible that a plane with that shape can fly, it violates almost every aerodynamic principle... and yet it flew because they have managed to create a computer system that made it fly.

My guessing is that the switchblade contains solutions that are not recognisable by outsiders.
Northrop as being one of the top stealth specialist has more that one ace up its sleeve...

As for Boeing's Sonic Cruiser it was a major technology development aircraft. the B 787 Dreamliner used all its technology development and is currently breaking the record for the fastest selling plane...


[edit on 4-4-2006 by carcharodon]

Originally posted by carcharodon

As for Boeing's Sonic Cruiser it was a major technology development aircraft. the B 787 Dreamliner used all its technology development and is currently breaking the record for the fastest selling plane...

It sure as hell didn't use all the wind tunnel development time wasted on the sonic cruiser. Nor the time spent on engine design.

Boeing now believes that the Mach 0.98 Sonic Cruiser airliner will need advanced technology -- all-new engines and an all-composite airframe -- to meet its performance, economic and environmental targets, according to product development VP Dan Mooney.

Mooney says that there was "some early optimism" among Boeing leaders who suggested that the radical aircraft could work with simple derivative engines and a conventional structure. "The preliminary design folks were kind of cringing when they heard those statements," he says.

Composites, however, are necessary to meet weight targets given the Sonic Cruiser's large wing area, and the new engines will represent a balance between noise, efficiency and cross-sectional area.

According to Mooney, the first round of wind tunnel tests last year produced positive results in two important respects. "There were two concerns: the drag rise near Mach 1 and what would happen when the aircraft goes through Mach 1." Tests have shown that the drag rise is flat up to Mach 0.98, without an abrupt increase, and that the design is stable above Mach 1.

AviationNow


I have to comment on his mentioning of the 'magical' eradication of the transonic drag rise - if that truly were the case, then all airliners would already be cruising at M 0.9+, but its simply uneconomic to go much above 0.85. *just looking at a jpeg of proposed SC* Hmm, to be fair there is alot of LE sweep on the wing, at least the inboard section anyway, but not the outboard section. Unless Boeing were proposing to use a shock strength reducer they would get BL seperation for sure.


It is possible that their preliminary wind tunnel tests were not able to run with the correct mach and Reynolds number at the same time (its a side effect of scaled model designs), so they were not seeing shock induced seperation - it would be a remarkable oversight if it were the case though.

well it would be very unstable so ya maneuverable but it has so much drag on it from such a wide front end and when the wings switch positions you would lose all control crash and die b/c your switching the lifting surface so any little disturbance POOf gone

sweet design though!!!!!!!!!!!

Originally posted by Figher Master FIN
Pleasure to read as always...

I agree with you on the stealth factor... but flyin without tailless design can be pretty bad... Sure it gives better stealth... BUT, what about the stability...??

Santa Clause does exist... He lives here in Finland...

[edit on 4-4-2006 by Figher Master FIN]

Stability shouldn't be that much of an issue with modern aircraft; the flight-control systems should be able to handle that.

You made some really good points! As for the issue of the swing wings, I've wondered the same thing. Now, the rounds exausts could work. Check out the jet nozzle on the back of an F-35, it's very simular. However, your other points are something to look into!

Tim

Originally posted by ghost
You made some really good points! As for the issue of the swing wings, I've wondered the same thing. Now, the rounds exausts could work. Check out the jet nozzle on the back of an F-35, it's very simular. However, your other points are something to look into!

Tim

I don't think the F-35 is designed to have a low RCS from the rear quarter though.

Oh look

Originally posted by kilcoo316
I don't think the F-35 is designed to have a low RCS from the rear quarter though.

We can look into that! I thought the latest rage in the US was all-aspect stealth.

Tim

doesn't a convergent/divergent afterburning nozzle, such has the F-35 has, pretty much rule out all aspect stealth?

Originally posted by waynos
doesn't a convergent/divergent afterburning nozzle, such has the F-35 has, pretty much rule out all aspect stealth?

I'm not sure, you might be right!

Tim

Originally posted by waynos
doesn't a convergent/divergent afterburning nozzle, such has the F-35 has, pretty much rule out all aspect stealth?

Pretty much, yes. Both the F-22 and F-35 use some composites in this area, which may or may not be radar-transparent, and RAM but ultimately the exhausts remain a weakpoint and moreso in IR terms.

If you look at a typical stealth exhaust (see X-45 below) it is long, thin and distanced from the turbine to minimise the angles from which radar can penetrate it and to spread the hot air and increase mixing with cooler air to redce the "hot spot" effect:


But those features all reduce the thrust produced which makes it unsuitible for a fighter. This picture of the YF-22 shows the basic problem:

We know that RAM is used to reduce the signiture. Also note that the exhaust is square not oblong - there is still likely to be a significant hot spot in the middle where the exhaust gasses are not mixed with the outside air until some distance behind the aircraft (see my other thread on F-22 IR stealth).

The F-35 is clearly worse in this regard having a round exhaust, presumably to maximise thrust in the VTOL context.

that's a good point concerning the wing glove. in a stealth design any kind of gap or opening let's all kind of radar "bleed" in.
i recall an article a few year back in Avation Week or Popular Science that described an eyewitness account of an aircraft with a similar looking tail arrangement. it was described as extremely manouverable and had double horizontal stabilizers, almost like a sawtooth pattern.
with the switchblade's wings swept backward i can see a similar shape.
I beleive the article was published before the switchblade story came out.
does this ring a bell for anyone?