Akaflieg Karlsruhe AK-X

Thank you so much Andreas. This project and Mu-31 are projects that seem like they have potential to develop new technology.


On Monday, December 11, 2017 at 12:41:31 PM UTC-8, Andreas Maurer wrote:
On Mon, 11 Dec 2017 14:03:36 +0000 (UTC), Kiwi User
wrote:


Yes, I was aware that this is a complex set of three control surfaces per
wing, but I'm a little confused about their function, but I think that,
listing from root to tip they were elevator,aileron,drag rudder. Is this
a fair description.

Close.

One needs to know that the AK-X works in a completely different way
than any other flying wing ever designed. Despite its similar
appearance, it is not even similar to the SB-13 aerodynamics-wise.

1. The AK-X is a flapped wing. At low speeds, all (!!) control
surfaces move downwards, at high speeds all move upwards. Just like an
ordinary glider. The rudders are in the winglets.

2. Pitch control is done by the inner flaps which work the same way as
a canard. Pitch up: Control deflection down, and vice versa. Perfect
solution concerning lift-distribution.

3. Compare the wing sweep of the AK-X to other flying wings: It is
much greater. This shows good promise to get rid of the pitch axis
oscillations experienced by other flying wings and the CG sensitivity
that has plagued all flying wing designs so far.
However, it needs an extremely stiff wing , which has just become
possible in the last few years after the latest progress in carbon
fibre stiffness.
(Fun fact: The wing is so stiff that the structural test did not
result in the wing spar breaking but in a torsional fracture of the
wing shell!)



Comparison to previous flying wing designs:

All previous flying wings had one huge basic fault:
In order to pitch up (or to fly slow), you had to deflect the controls
up, therefore reducing airfoil camber and thus lift coefficient -
basically exactly the opposite of what you'd like to have
aerodynamically.

The wing of the AK-X works exactly like that of any flapped glider:
Low-speed flight: All flaps deflected "down"
High-speed flight: All flaps deflected "up"


The idea behind this aredoynamic design is, frankly spoken, a touch of
genius. It's the first ever flying wing design ever that in theory
will be able to compete with a conventional design in all areas of the
flight envelope up to very high speeds.

Plus, there are a couple of other benefits:
The wing uses conventional airfoils whose aerodynamic qualities can be
predicted well today. The flapped wing creates the same lift
coefficient as the wing of a conventional design, allowing high aspect
ratio and wing loading.
Behind the cockpit there's a 40 liter water tank (directly at the
center of gravity) and no other structural parts - pretty simple to
replace this tank with an angine and some serious battery capacity.


To me, the only remaining question is the influence of the wing sweep
on spanwise flow - but as I heard the guys are pretty optimistic so
far (they've got a 1:2 model flying with very good results).




Cheers
Andreas