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I realize the plane is fictional. However, in the Batman Animated Series by Warner Bros, we see this Batjet.

enter image description here

So this got me thinking (and I'm not a physicist): is this air frame configuration even possible? Has a "rounded", forward-swept wing design like this been attempted before? Or would a design like this never actually fly?

Any real-world examples that are similar in nature?

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  • $\begingroup$ @RyanMortensen what? $\endgroup$ – Jon Jun 27 at 2:52
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    $\begingroup$ @RyanMortensen ah I see. $\endgroup$ – Jon Jun 27 at 2:54
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    $\begingroup$ With enough power, anything will fly, as a cursory visit to any R/C group will attest. Are you interested in hearing that or is this about whether this design makes sense from some perspective? $\endgroup$ – AEhere supports Monica Jun 27 at 3:03
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    $\begingroup$ It's actually not difficult to build a kite like this that would fly pretty well. I believe some good father have built one for his kit over these years, somewhere in the world. Airplanes looks like they do now because others are less efficient, not others won't fly. With enough power, anything flies. $\endgroup$ – user3528438 Jun 27 at 4:08
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    $\begingroup$ This is actually one of the few good "hypothetical" questions that's been asked. $\endgroup$ – FreeMan Jun 27 at 16:06
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Yes, rounded wings have been tested in the past. Probably the most famous example is the Vought XF5U "Flying Flapjack". They work perfectly fine. However, the design as pictured does have some flaws.

Efficiency

The lower the aspect ratio (i.e. wider front-to-back in comparison to their length left-to-right), the more inefficient the wing. This is due to there being a lot of area available for the high pressure under the wing to wrap around to the low pressure on top, creating large wingtip vortices. For the Batwing, this would be doubly true, as a large part of the wings have edges on the inside, almost doubling the effect.

Stability

It appears that the engine is either directly behind or directly below the cockpit, putting the center of gravity way too far back compared to the center of lift. This creates an unstable situation, especially at low speed. As the elevator loses effectiveness, the nose of the aircraft will tend to rise, further exacerbating the loss of speed and leading to a stall. Such a stall would be almost guaranteed to be unrecoverable using normal means.

(I say "normal means" because, in the show, the Batwing was shown to have VTOL capability, meaning it has vents in the bottom to redirect thrust down and hover. So, it would be theoretically possible to use engine thrust to rotate the plane nose-down and recover from the stall. If the engine fails, though, this airplane becomes an absolute deathtrap.)

Control Surface Effectiveness

Unfortunately, the animators of the show never animated the control surfaces, so we're left to guess where they are and how big they are. If they're in the standard position in back, that puts them close to the axis of rotation (which goes through the center of gravity, see above), limiting their effectiveness.

The elevators could be moved to the leading edge, but the slipstream on them would cause issues with flutter, and it would take a huge amount of control force to keep them from being pinned at their limits. This also wouldn't help the ailerons (because they'd still be close to their axis of rotation) or the rudder (because there's nowhere to put it other than that big mohawk structure coming off the top of the cockpit).


So, in short, it's possible, but not in any way practical.

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  • $\begingroup$ The XF-5U never flew. Its equally rounded predecessor was the Vought V-173 prototype, which did fly. $\endgroup$ – Guy Inchbald Jun 27 at 13:36
  • $\begingroup$ This very good answer could be improved by mentioning directional stability as well. It might actually have a chance if the cockpit, engine, and vertical fin were reversed. $\endgroup$ – Robert DiGiovanni Jun 30 at 8:40
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Rounded, forward-swept and reverse-tapered designs have all been flown, but never put together.

A rounded example has been given, though it was propeller-driven. The jet-powered Avro Canada VZ-9 Avrocar was a slightly weird VTOL concept which failed to fly properly. Another intriguing one, though intended to be rocket powered, was the Pye Wacket hypersonic missile project.

Forward-swept fast jets include the Grumman X-29 and Sukhoi Su-47.

The Republic XF-91 Thunderceptor had reverse taper. It did what it was meant to do, which was to avoid pitch instability near the stall. But, for rather obvious reasons, it was structurally impractical. The Batjet would suffer the same problem.

The other problem with the Batjet design is centre of mass. It needs to vary from around one-third chord at subsonic speeds to one-half chord at supersonic speeds. The cartoon design has it too far back at around the two-thirds chord position, causing a strong nose-up tendency. Jet thrust at the rear would have to be angled sharply downwards to maintain trim, and this would militate against speeds much higher than a helicopter.

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