Akaflieg Karlsruhe AK-X

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 Wednesday, December 13, 2017 at 7:42:38 AM UTC-8, wrote:
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

A steerable nose wheel would solve this problem. On my ASH26 Mi, I'd sooner give up the engine than the steerable tailwheel.

On Wednesday, December 13, 2017 at 12:06:56 PM UTC-5, jfitch wrote:
On Wednesday, December 13, 2017 at 7:42:38 AM UTC-8, wrote:
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

A steerable nose wheel would solve this problem. On my ASH26 Mi, I'd sooner give up the engine than the steerable tailwheel.

A steerable nose wheel would only work well, if the main wheel location is moved further back.
RS

On Wed, 13 Dec 2017 11:46:30 +0000 (UTC), Kiwi User
wrote:

On Wed, 13 Dec 2017 01:27:16 +0100, Andreas Maurer wrote:

Hi Andras,


I'm rather worried about spanwise flow originating at the wing root
(similar to the SB-13) - but let's wait and see. The guys (and gals)
know their stuff.

I notice that initial drawings put the wing at the bottom of the pilot's
pod, but in the 1:2 model its just below the canopy rim. Was this for
wing clearance or aerodynamics?

Several causes:
- mainly wing tip clearance: The wing tips are far behind the landing
gear and dihedral is only 2 degrees, they come down when the nose goes
up, creating ground clearance problems

- with the wing out of the way lots of space for a really strong nose
gear (one of the famous weak points of the SB-13)

- the wing spar is now over the knees of the pilot, leaving plenty of
easily accessible space for the controls, mixer and Haenle-type stick
between wing spar and instrument panel

- lots of space for the pilot (I'm 6'7" and fitedt comfortably in the
prototype fuselage on the Aro aviation fair)

In their own (German) words:
https://akaflieg-karlsruhe.de/ak-x/aerodynamik/



I'm a little surprised, too, at the quite minimal root fairings. Is this
what you were referring to when you mentioned spanwise flow at the root?

Well, aerodynamically speaking there is no need for wing root fairings
as long as the complete wing root is in an area of pressure rise.
On a conventional glider the wing is in the area of pressure loss
(aka: where the fuselage gets thinner), resulting in the need for a
wing fairing.

I'm not the designer of course, but I think you can be sure that we'll
get to know all the details in the future.

What I'm referring to can be seen on the SB-13:
http://www.airport-data.com/aircraft...00724103.html#

Look at the little red wing fences - afaik they had to be intruduced
to tame handling (stall?) characteristics.

(Bert: Dein Auftritt! Habe das SB-Buch gerade nicht vor mir, wo der
genaue Grund beschrieben wurde).


It would be interesting to see flow visualisation round them. Though, as
you say, the guys and gals know their stuff, so maybe cleaning up the
wing roots is being left for full size detailed design. After all, the
1:4 model had nothing except a couple of sensor probes at its root, so
just adding the pod was quite a big step aerodynamically.

Definitely.

BTW:
This is the project page of the AK-X 1/2 model:
https://akaflieg-karlsruhe.de/tag/12-modell/
On the spin onboard video you can nicely see how the inner flaps work
as elevator.

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

On Wed, 13 Dec 2017 21:50:57 +0100, Andreas Maurer wrote:

Several causes:
- mainly wing tip clearance: The wing tips are far behind the landing
gear and dihedral is only 2 degrees, they come down when the nose goes
up, creating ground clearance problems

I didn't think of that.

- with the wing out of the way lots of space for a really strong nose
gear (one of the famous weak points of the SB-13)

OK

- the wing spar is now over the knees of the pilot, leaving plenty of
easily accessible space for the controls, mixer and Haenle-type stick
between wing spar and instrument panel

Nice.

What I'm referring to can be seen on the SB-13:
http://www.airport-data.com/aircraft...00724103.html#

Look at the little red wing fences - afaik they had to be intruduced to
tame handling (stall?) characteristics.

OK, understood.

BTW:
This is the project page of the AK-X 1/2 model:
https://akaflieg-karlsruhe.de/tag/12-modell/
On the spin onboard video you can nicely see how the inner flaps work as
elevator.

Yes I found that this morning. Must be new: I've visited that page before
but don't recall seeing it then.

Fascinating to watch those inner flaps thinking they're on a canard!



--
Martin | martin at
Gregorie | gregorie
| dot org

On Wed, 13 Dec 2017 22:21:43 +0100, Andreas Maurer wrote:

If you're interested in the history of soaring and especially in fins
detail of particular gliders its well worth bookmarking the Scale Soaring
website:

https://scalesoaring.co.uk

Just don't be put off by its name! The in-depth documentation and photos
of the gliders it does cover is excellent, e.g the Fafnir. However, its
overall coverage isn't a patch on Martin Simon's "Sailplanes" three
volume series: you'll definitely want them as well. The Scale Glider
crowd rate them highly for his three-view drawings.


--
Martin | martin at
Gregorie | gregorie
| dot org

On Wed, 13 Dec 2017 21:46:06 +0000 (UTC), Kiwi User
wrote:

On Wed, 13 Dec 2017 22:21:43 +0100, Andreas Maurer wrote:

If you're interested in the history of soaring and especially in fins
detail of particular gliders its well worth bookmarking the Scale Soaring
website:

https://scalesoaring.co.uk

Just don't be put off by its name! The in-depth documentation and photos
of the gliders it does cover is excellent, e.g the Fafnir. However, its
overall coverage isn't a patch on Martin Simon's "Sailplanes" three
volume series: you'll definitely want them as well. The Scale Glider
crowd rate them highly for his three-view drawings.

Well Martin,

guess what's been robbing my time for the last couple of hours.......


Brilliant website!

Cheers
Andreas

At 21:21 13 December 2017, Andreas Maurer wrote:
On Wed, 13 Dec 2017 05:10:38 +0000, Michael Opitz
wrote:

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"....


The Me 163 had an L/D of ~17, but the speeds were too high for
any kind of thermal flight, especially for the heavy weaponized
Me 163b version. Between the good L/D and ground effect, it was
hard to get onto the ground in a reasonable distance until Dr
Lippisch had Josef Hubert design under wing dive brakes for extra
drag. Hubert also came up with the wing slots in front of the
elevons to basically stop the tips from stalling at high AOA.

Now, Dad did thermal a fully loaded (10 people) DFS 230 for
up to an hour, and I heard that some of the passengers may have
gotten a little airsick...

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


Thank you very much 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?).

Right after I made that post, I found and bought a copy from an
American seller. Danke für's Angebot. Auf Deutsch geht's mir
auch noch recht gut.......

Gruß,

RO

On 14/12/2017 07:50, Andreas Maurer wrote:
....
Several causes:
- mainly wing tip clearance: The wing tips are far behind the landing
gear and dihedral is only 2 degrees, they come down when the nose goes
up, creating ground clearance problems

Same reason as the dihedral on 707/DC-8, etc tailplanes I understand

- with the wing out of the way lots of space for a really strong nose
gear (one of the famous weak points of the SB-13)

- the wing spar is now over the knees of the pilot, leaving plenty of
easily accessible space for the controls, mixer and Haenle-type stick
between wing spar and instrument panel

Spar OVER the pilot's knees?? Sounds like emergency exits might be
interesting - and not very rapid.

- lots of space for the pilot (I'm 6'7" and fitedt comfortably in the
prototype fuselage on the Aro aviation fair)

In their own (German) words:
https://akaflieg-karlsruhe.de/ak-x/aerodynamik/

--
GC