Akaflieg Karlsruhe AK-X

At 20:41 11 December 2017, Andreas Maurer wrote:

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


Andreas,

Thank you very much for the insights. If my father were still alive
today, he would be wanting to follow the progress very closely. The
aerodynamic genius of using the wing sweep to emulate canard
characteristics as opposed to using the sweep for high speed flight
is extremely intriguing. Being able to use current modern airfoils
while reducing drag considerably, should result in very noticeable
performance increases. Also, the advent of newer construction
materials and methods which enable the builders to achieve the
stiffness that is required to overcome other previous wing's
aeroelastic issues cannot be overstated.

Please post any progress updates here whenever you may hear of
them in the future....

RO

On Tue, 12 Dec 2017 03:30:19 +0000, Michael Opitz
wrote:


Thank you very much for the insights. If my father were still alive
today, he would be wanting to follow the progress very closely. The
aerodynamic genius of using the wing sweep to emulate canard
characteristics as opposed to using the sweep for high speed flight
is extremely intriguing. Being able to use current modern airfoils
while reducing drag considerably, should result in very noticeable
performance increases. Also, the advent of newer construction
materials and methods which enable the builders to achieve the
stiffness that is required to overcome other previous wing's
aeroelastic issues cannot be overstated.

Please post any progress updates here whenever you may hear of
them in the future....

I promise.
I happen to be at the Akaflieg Karlsruhe workshop two times per year
so with a little luck I can provide you with some updates if the
Akaflieg guys allow that.


But since we are talking:
Has your father ever talked about (or even flown) the Horten VI (the
24m glider)? I was always amazed that such a thing could be built in
the pre-carbon fibre aera.

There are a couple of reports about the IV, but I couldn't find any
halfways detailed source about the VI.

And, second question:
Do you know if the Horton guys aver considered winglets instead of the
drag ailerons?

Cheers
Andreas

At 00:34 13 December 2017, Andreas Maurer wrote:
On Tue, 12 Dec 2017 03:30:19 +0000, Michael Opitz
wrote:


Thank you very much for the insights. If my father were still
alive
today, he would be wanting to follow the progress very closely.
The
aerodynamic genius of using the wing sweep to emulate canard
characteristics as opposed to using the sweep for high speed
flight
is extremely intriguing. Being able to use current modern airfoils
while reducing drag considerably, should result in very noticeable
performance increases. Also, the advent of newer construction
materials and methods which enable the builders to achieve the
stiffness that is required to overcome other previous wing's
aeroelastic issues cannot be overstated.

Please post any progress updates here whenever you may hear
of
them in the future....

I promise.
I happen to be at the Akaflieg Karlsruhe workshop two times per
year
so with a little luck I can provide you with some updates if the
Akaflieg guys allow that.


But since we are talking:
Has your father ever talked about (or even flown) the Horten VI
(the
24m glider)? I was always amazed that such a thing could be built
in
the pre-carbon fibre aera.



Martin Gregorie provided a pretty good link for a brief Horten
history:

https://scalesoaring.co.uk/VINTAGE/D.../Horten%20IV/H
orten_IVb.html

From that article:

"As Heinz Scheidhauer was the most experienced and long serving
Horten pilot, it is also strange that the test flying of the H IVb should
be passed to Strebel at such an early stage.

Scheidhauer had flown most of the Horten types and despite some
peculiarities, their handling had been generally benign as they were
highly stall and spin resistant. Although the H IVa had been liable to
flutter, it had proved possible to damp it by simultaneous use of the
drag rudders. None the less, he had refused to fly an HIII to explore
its handling at extreme rear centre of gravity positions. On 24 May
1944 he made the maiden flight of the ultra high aspect ratio H VI,
discovering that not only was it subject to flutter at both high and
low speeds but that the entire wing was far too flexible and fragile
for even an expert pilot.

If Zubert’s log book entry is correct, the pilot of the H IVb on 11
August was almost certainly Scheidhauer and this may also have
been its maiden flight – long before the H XIIIa.

Unfortunately just ten weeks after test flying the H VI, Scheidhauer
discovered that the H IVb suffered from truly appalling handling
characteristics and would abruptly drop a wing and attempt to spin
at speeds as high as 77km/h, yet above 110 km/h the wings would
flutter. Later, also he refused to fly the H XIIIa which Strebel tested
from the outset. It seems that Scheidhauer was losing faith in
Reimar’s ability as a designer."


Scheidhauer was a student of Dad's from the first military glider
pilot training class at the DFS in ~1937 where Dad was one of the
three original instructors. Dad also later got him a flight in a Me
163, even though he was from the Horten camp. By 1944 when
Scheidhauer first flew the Ho VI, Dad was pretty deep into getting
operational Me 163 units up and running. His glider logbook shows
one or two Ho III entries earlier, but no Ho VI. He never really
talked about the Ho VI at all. I doubt it flew much considering the
info from the above story.


There are a couple of reports about the IV, but I couldn't find any
halfways detailed source about the VI.

And, second question:
Do you know if the Horton guys aver considered winglets instead
of the
drag ailerons?


I don't know if they considered winglets, and I can't remember what
the aircraft they designed after the war in Argentina looked like.
The person to ask is Peter Selinger. He was also a friend of
Scheidhauer's and received all of Scheidhauer's personal logs, etc
when he passed away. Peter also wrote a book on the Hortens, but
unfortunately, I don't have a copy of it.

"Nurflügel", by Peter F. Selinger and Dr. Reimar Horten
ISBN-103900310092
ISBN-139783900310097

I do have Peter's contact info in case you want it though. We have
been in fairly regular contact with each other since 1985.

RO

Michael,
I am interested in the crosswind landing characteristics of flying wings, do you have any information on the discussed ships? The Genesis-2 has no problem landing in a crosswind, but as the forward speed slows to equal the crosswind speed, the ship turns into the wind and opposite rudder does nothing! After years of stopping on the runway, I deliberately started carrying an extra 10 knots of speed into the desired stopping area, then jump on the good hydraulic brake to stop the ship where desired.
JJ

On Wed, 13 Dec 2017 05:10:38 +0000, Michael Opitz
wrote:

Martin Gregorie provided a pretty good link for a brief Horten
history:

https://scalesoaring.co.uk/VINTAGE/D.../Horten%20IV/H
orten_IVb.html


Thank you very much - extremely interesting lecture that I didn't know
yet.

Scheidhauer had flown most of the Horten types and despite some
peculiarities, their handling had been generally benign as they were
highly stall and spin resistant. Although the H IVa had been liable to
flutter, it had proved possible to damp it by simultaneous use of the
drag rudders. None the less, he had refused to fly an HIII to explore
its handling at extreme rear centre of gravity positions. On 24 May
1944 he made the maiden flight of the ultra high aspect ratio H VI,
discovering that not only was it subject to flutter at both high and
low speeds but that the entire wing was far too flexible and fragile
for even an expert pilot.

Sounds.... interesting and exciting.


Scheidhauer was a student of Dad's from the first military glider
pilot training class at the DFS in ~1937 where Dad was one of the
three original instructors. Dad also later got him a flight in a Me
163, even though he was from the Horten camp. By 1944 when
Scheidhauer first flew the Ho VI, Dad was pretty deep into getting
operational Me 163 units up and running. His glider logbook shows
one or two Ho III entries earlier, but no Ho VI. He never really
talked about the Ho VI at all. I doubt it flew much considering the
info from the above story.

This would be the next interesting topic in RAS: "What the test pilot
thought about the Me-163 as a glider"....

I don't know if they considered winglets, and I can't remember what
the aircraft they designed after the war in Argentina looked like.
The person to ask is Peter Selinger. He was also a friend of
Scheidhauer's and received all of Scheidhauer's personal logs, etc
when he passed away. Peter also wrote a book on the Hortens, but
unfortunately, I don't have a copy of it.

"Nurflügel", by Peter F. Selinger and Dr. Reimar Horten
ISBN-103900310092
ISBN-139783900310097

I do have Peter's contact info in case you want it though. We have
been in fairly regular contact with each other since 1985.


Thank you very mich again - I'm aware of this book, but to be honest:
I was always a little fascinated by the Horten gliders, but not enough
to buy the book since I always thought their designs were some kind of
one-trick-pony.

The book is available on Amazon Germany - just tell me if I should get
you a copy (how's your German?).


Cheers
Andreas

At 05:10 13 December 2017, Michael Opitz wrote:
At 00:34 13 December 2017, Andreas Maurer wrote:

And, second question:
Do you know if the Horton guys ever considered winglets instead
of the drag ailerons?


Andreas,

I just got my copy of the book. The only Horten design which I
found using winglets (although they were ~2-3 meters inboard of
the tips) was on a 4 engine transport, the Ae. 38. The rudders only
moved in the outboard direction, and were controlled by
aerodynamic servo tabs. It only flew once due to being forced
(by nationalistic pride) to use engines that had only 40% of the
power that the aircraft was designed for. It had 30 cubic meters of
storage space. The Ae. 38 was conceived of in 1950 in Argentina.
It eventually flew there in 1960 and was then scrapped.

JJ,

Sorry I didn't answer about your crosswind question earlier. I'm
afraid that I don't know the answer to it though. Unless I find
something about it in the book, anything I would say at this point
would only be speculation except that I don't remember Dad
addressing crosswind landings in the Ho IV. The Me 163 had a
rudder like the Genesis and a much higher approach speed, so it
handled crosswinds like most other aircraft, except when it had
been flown so fast that the transonic flutter had caused the
rudder to disintegrate so badly that only the front spar/hinge
was left. Dad found that result on approach as he tried to slip it
with no result after one particularly high speed flight...

RO

At 14:03 11 December 2017, Kiwi User wrote:

BTW, have you see this article about the Ho S.IVb:

https://scalesoaring.co.uk/VINTAGE/D...n/Horten%20IV/
Horten_IVb.html

Lots of photos, good plan showing the three control surfaces per wing
and
a useful write-up about construction, flying characteristics and where
the airframes went.

A bigger plan is downloadable from he

https://scalesoaring.co.uk/VINTAGE/D...n/Horten%20IV/
Horten_IV_model.html



As far as I know, the replica has not flown.

Thanks for the scalesoaring links, I had not seen them before.

RO