Akaflieg Karlsruhe AK-X [Archive]

Kiwi User

December 9th 17, 07:44 PM

On Sat, 09 Dec 2017 09:20:40 -0800, Mike C wrote:

> On Saturday, December 9, 2017 at 9:07:18 AM UTC-7, Kiwi User wrote:
>> On Fri, 08 Dec 2017 19:52:04 -0800, Jonathan St. Cloud wrote:
>>
>> > Akaflieg Karlsruhe AK-X
>>
>> Looks like they've got a 25% scale model built and awaiting test
>> flying.
>> If you read German, this looks interesting and has lots of photos:
>> https://akaflieg-karlsruhe.de/project/ak-x/
>>
>> Be aware that your browser may object, though, because its an https
>> site and the certificate expired a few days ago.
>>
>>
>> --
>> Martin | martin at Gregorie | gregorie
>> | dot org
>
> Exciting work!
>
> I hope these students design and build a contest viable swept wing
> sailplane.
>
Lets hope that, unlike the Horten gliders and their earlier SB-13 Arcus,
it doesn't have a nasty high-speed pitch oscillation, that seems to be an
unwanted feature of swept wing tailless aircraft.

I've seen flight reports about a Horten S.IV when it was being flown in
US comps that mentioned that a 'pecking' oscillation limited its cruising
speed and flight reports about the SB-13 show that it shared this
behaviour.

The DH.106 Swallow, an early British swept-wing jet, also showed the same
high speed oscillation. That killed Geoffrey de Havilland Jr. when the
pitch oscillation broke his neck during a high speed run in the 2nd
prototype and almost killed Eric 'Winkle' Brown in the 3rd - he said that
the oscillation was very violent and thought he only survived because he
was smaller than de Havilland and so didn't get his head slammed into the
canopy. When he slowed down below a critical speed the oscillation
stopped as suddenly as it had started

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

Mike C

December 9th 17, 07:55 PM

On Saturday, December 9, 2017 at 12:44:46 PM UTC-7, Kiwi User wrote:
> On Sat, 09 Dec 2017 09:20:40 -0800, Mike C wrote:
>
> > On Saturday, December 9, 2017 at 9:07:18 AM UTC-7, Kiwi User wrote:
> >> On Fri, 08 Dec 2017 19:52:04 -0800, Jonathan St. Cloud wrote:
> >>
> >> > Akaflieg Karlsruhe AK-X
> >>
> >> Looks like they've got a 25% scale model built and awaiting test
> >> flying.
> >> If you read German, this looks interesting and has lots of photos:
> >> https://akaflieg-karlsruhe.de/project/ak-x/
> >>
> >> Be aware that your browser may object, though, because its an https
> >> site and the certificate expired a few days ago.
> >>
> >>
> >> --
> >> Martin | martin at Gregorie | gregorie
> >> | dot org
> >
> > Exciting work!
> >
> > I hope these students design and build a contest viable swept wing
> > sailplane.
> >
> Lets hope that, unlike the Horten gliders and their earlier SB-13 Arcus,
> it doesn't have a nasty high-speed pitch oscillation, that seems to be an
> unwanted feature of swept wing tailless aircraft.
>
> I've seen flight reports about a Horten S.IV when it was being flown in
> US comps that mentioned that a 'pecking' oscillation limited its cruising
> speed and flight reports about the SB-13 show that it shared this
> behaviour.
>
> The DH.106 Swallow, an early British swept-wing jet, also showed the same
> high speed oscillation. That killed Geoffrey de Havilland Jr. when the
> pitch oscillation broke his neck during a high speed run in the 2nd
> prototype and almost killed Eric 'Winkle' Brown in the 3rd - he said that
> the oscillation was very violent and thought he only survived because he
> was smaller than de Havilland and so didn't get his head slammed into the
> canopy. When he slowed down below a critical speed the oscillation
> stopped as suddenly as it had started
>
>
> --
> Martin | martin at
> Gregorie | gregorie
> | dot org

Martin,

SB13 was a Akaflieg Braunschweig project.

Mike

Tango Whisky

December 9th 17, 09:13 PM

On the SB13, the pitch oscillation was discovered to couple to the bending mode of the wing. The spar was therefore build with hogh modulus fibres (a first in aviation) in order to push the bending frequency out.

The pitch oscillation could be mostly suppressed by moving the cg aft.

Which then resulted in a very nasty stall behaviour due to span-wise flow on the swept wing. Boundary fences did help on that.

All in all, tricky optimisations. Plus a complicated lay-up plan for the swept-back spar in order to get the torsional load into the wing skin.

Kiwi User

December 9th 17, 09:43 PM

On Sat, 09 Dec 2017 13:13:31 -0800, Tango Whisky wrote:

> On the SB13, the pitch oscillation was discovered to couple to the
> bending mode of the wing. The spar was therefore build with hogh modulus
> fibres (a first in aviation) in order to push the bending frequency out.
>
Fair enough. I've subsequently found similar comments about the Horten
S.IV and the DH.106.

> All in all, tricky optimisations. Plus a complicated lay-up plan for the
> swept-back spar in order to get the torsional load into the wing skin.
>
From what I've read this seems to be a major problem with all swept
tailless designs.

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

Michael Opitz

December 10th 17, 01:38 AM

>> I hope these students design and build a contest viable swept
wing
>> sailplane.
>>
>Lets hope that, unlike the Horten gliders and their earlier SB-13
Arcus,
>it doesn't have a nasty high-speed pitch oscillation, that seems to
be an
>unwanted feature of swept wing tailless aircraft.
>
>I've seen flight reports about a Horten S.IV when it was being
flown in
>US comps that mentioned that a 'pecking' oscillation limited its
cruising
>speed and flight reports about the SB-13 show that it shared this
>behaviour.
>
>The DH.106 Swallow, an early British swept-wing jet, also showed
the same
>high speed oscillation. That killed Geoffrey de Havilland Jr. when
the
>pitch oscillation broke his neck during a high speed run in the 2nd
>prototype and almost killed Eric 'Winkle' Brown in the 3rd - he said
that
>the oscillation was very violent and thought he only survived
because he
>was smaller than de Havilland and so didn't get his head slammed
into the
>canopy. When he slowed down below a critical speed the oscillation
>stopped as suddenly as it had started
>
>
>--
>Martin | martin at
>Gregorie | gregorie
> | dot org

Martin,

That was my father who re-built and flew the Ho-IV in 1952 USA
contests. He limited himself to no more than 80 mph IAS in order
to keep away from the pitch "pecking" characteristics which made
him uncomfortable. From the late 1930's until the mid 1940's,
he was one of the world's top flying wing test pilots, so he knew
exactly what he was doing when he flew the Ho-IV.

When I showed him the SB-13 designs and photos, the "pecking"
was the first thing he mused about before they even flew it. Once
they flew it, and it was established that it had the same issues, he
just said that he'd thought that they would have solved that issue by
that time.

That is not to say that other designs did not have those issues, or
had not solved them earlier. My father and Heini Dittmar were
the two Lippisch primary test pilots who were with the Me 163 for
basically its entire existence. That team knew it wanted to go fast,
and that slow speed handling issues would only be amplified at
higher speeds, so they concentrated very hard on good handling
characteristics on that bird. Their results showed exceptional
handling as reported by Capt Eric Brown among many others. Dr.
Lippisch and his team overcame those aerodynamic issues, while
the Hortens and the DH.106 Swallow apparently never did.

Dad was from the Lippisch camp, but through a unique set of
circumstances, he had also gained the trust of the competition,
which was the Horten camp. Thus, the Hortens let him fly a number
of their creations as well. His basic opinion was that the Hortens
designed beautiful looking aircraft, but the handling was always
marginal at the very best, even in the slower speed regimes. He
never thought that the Hortens would succeed in high speed flight
as long as they didn't make vast improvements on their designs.

The Ho-IV which he flew in 1952 came from England. It had
belonged to Geoffrey de Havilland Jr. I don't know if it was the
one that Robert Kronfeld had brought to England, or if de
Havilland had brought it there from Germany after the war.
Then, de Havilland sold it to another British test pilot named
Hollis Button who brought it to the USA, and promptly lost control
on his first take-off, thus crashing it. Now, Button was left with a
broken glider that nobody knew how to fix. He hunted Dad down
after he had heard that my father had the skills to fix it. Dad
agreed to fix it as long as he could fly it for the entire next (1952)
year's contest season. So, Dad repaired the Ho-IV over the 1951-
1952 winter and flew it in several contests in 1952. Thereafter, the
Ho-IV went to Mississippi State University where Dr. Gus Raspet
profiled the wings and made performance measurements. After
that, it was parked in a disassembled state in various places,
winding up in the desert SW USA. It was reported that someone
scavenged/stole the metal outer wing panels for use on some
experimental aircraft. Eventually, the Planes Of Fame Museum in
Chino, CA got it, and now have it hung on display in one of their
hangars. Unfortunately, it is very poorly restored with Styrofoam
outer wing panels in the wrong shape, as well as a rather grotesque
looking replacement lower fuselage/pod:

https://www.google.com/search?
q=planes+of+fame+Horten+IV&rlz=1C1CHWA_enUS602US603&tb
m=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwijoqS1lv7XAhVjh
OAKHfxjArEQsAQIKA&biw=1280&bih=918#imgrc=_

Pictures from the Mississippi State flight performance testing, where
Dad had checked out Professor Dezso George-Falvy in order to
continue the program. These photos show how the restored glider
really should look:

http://www.nurflugel.com/Nurflugel/Horten_Nurflugels/ho_iv/Falvy_
Pics/falvy_pics.html

My own personal guess on the "hunting/pecking" problem is that it
probably resides with aero-elastic issues and the swept back high
aspect ratio wing. Given the newest carbon-kevlar+? materials,
maybe the bending and torsional stiffness of a newer construction
wing can help overcome some of these issues.... We will see if and
when the SB-13 gets into the flight testing phase...

RO

Michael Opitz

December 10th 17, 01:45 AM

Oops... I meant AK-X and not SB-13 at the end of my last post.
Meanwhile, TW seems to confirm my suspicions. The Me 163 had a
much lower aspect ratio, and a much stiffer wing than the Horten
designs. This probably eliminated the pitch oscillation issues from
the start..

RO

Mike C

December 10th 17, 05:14 AM

On Saturday, December 9, 2017 at 7:00:10 PM UTC-7, Michael Opitz wrote:
> Oops... I meant AK-X and not SB-13 at the end of my last post.
> Meanwhile, TW seems to confirm my suspicions. The Me 163 had a
> much lower aspect ratio, and a much stiffer wing than the Horten
> designs. This probably eliminated the pitch oscillation issues from
> the start..
>
> RO

My father flew a 1-23 in the 1952 Nationals and said that the Horton had a very good max glide but at high speeds (for the time) the 1-23 was better. He thought it was due to lack torsional stiffness.

Mike

BobW

December 10th 17, 02:26 PM

On 12/9/2017 6:38 PM, Michael Opitz wrote:
>>> I hope these students design and build a contest viable swept wing
>>> sailplane.
>>>
>> Lets hope that, unlike the Horten gliders and their earlier SB-13 Arcus,
>> it doesn't have a nasty high-speed pitch oscillation, that seems to be
>> an unwanted feature of swept wing tailless aircraft.
>>
>> I've seen flight reports about a Horten S.IV when it was being flown in
>> US comps that mentioned that a 'pecking' oscillation limited its
>> cruising speed and flight reports about the SB-13 show that it shared
>> this behaviour.
>>
>> The DH.106 Swallow, an early British swept-wing jet, also showed the
>> same high speed oscillation. That killed Geoffrey de Havilland Jr. when
>> the pitch oscillation broke his neck during a high speed run in the 2nd
>> prototype and almost killed Eric 'Winkle' Brown in the 3rd - he said
>> that the oscillation was very violent and thought he only survived
>> because he was smaller than de Havilland and so didn't get his head
>> slammed into the canopy. When he slowed down below a critical speed the
>> oscillation stopped as suddenly as it had started
>>
>>
>> -- Martin | martin at Gregorie | gregorie | dot org
>
> Martin,
>
> That was my father who re-built and flew the Ho-IV in 1952 USA contests. He
> limited himself to no more than 80 mph IAS in order to keep away from the
> pitch "pecking" characteristics which made him uncomfortable. From the
> late 1930's until the mid 1940's, he was one of the world's top flying wing
> test pilots, so he knew exactly what he was doing when he flew the Ho-IV.
>
> When I showed him the SB-13 designs and photos, the "pecking" was the
> first thing he mused about before they even flew it. Once they flew it,
> and it was established that it had the same issues, he just said that he'd
> thought that they would have solved that issue by that time.
>
> That is not to say that other designs did not have those issues, or had
> not solved them earlier. My father and Heini Dittmar were the two
> Lippisch primary test pilots who were with the Me 163 for basically its
> entire existence. That team knew it wanted to go fast, and that slow
> speed handling issues would only be amplified at higher speeds, so they
> concentrated very hard on good handling characteristics on that bird. Their
> results showed exceptional handling as reported by Capt Eric Brown among
> many others. Dr. Lippisch and his team overcame those aerodynamic issues,
> while the Hortens and the DH.106 Swallow apparently never did.
>
> Dad was from the Lippisch camp, but through a unique set of circumstances,
> he had also gained the trust of the competition, which was the Horten camp.
> Thus, the Hortens let him fly a number of their creations as well. His
> basic opinion was that the Hortens designed beautiful looking aircraft, but
> the handling was always marginal at the very best, even in the slower speed
> regimes. He never thought that the Hortens would succeed in high speed
> flight as long as they didn't make vast improvements on their designs.
>
> The Ho-IV which he flew in 1952 came from England. It had belonged to
> Geoffrey de Havilland Jr. I don't know if it was the one that Robert
> Kronfeld had brought to England, or if de Havilland had brought it there
> from Germany after the war. Then, de Havilland sold it to another British
> test pilot named Hollis Button who brought it to the USA, and promptly
> lost control on his first take-off, thus crashing it. Now, Button was left
> with a broken glider that nobody knew how to fix. He hunted Dad down after
> he had heard that my father had the skills to fix it. Dad agreed to fix it
> as long as he could fly it for the entire next (1952) year's contest
> season. So, Dad repaired the Ho-IV over the 1951- 1952 winter and flew it
> in several contests in 1952. Thereafter, the Ho-IV went to Mississippi
> State University where Dr. Gus Raspet profiled the wings and made
> performance measurements. After that, it was parked in a disassembled
> state in various places, winding up in the desert SW USA. It was reported
> that someone scavenged/stole the metal outer wing panels for use on some
> experimental aircraft. Eventually, the Planes Of Fame Museum in Chino, CA
> got it, and now have it hung on display in one of their hangars.
> Unfortunately, it is very poorly restored with Styrofoam outer wing panels
> in the wrong shape, as well as a rather grotesque looking replacement lower
> fuselage/pod:
>
> https://www.google.com/search?
> q=planes+of+fame+Horten+IV&rlz=1C1CHWA_enUS602US603&tb
> m=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwijoqS1lv7XAhVjh
> OAKHfxjArEQsAQIKA&biw=1280&bih=918#imgrc=_
>
> Pictures from the Mississippi State flight performance testing, where Dad
> had checked out Professor Dezso George-Falvy in order to continue the
> program. These photos show how the restored glider really should look:
>
> http://www.nurflugel.com/Nurflugel/Horten_Nurflugels/ho_iv/Falvy_
> Pics/falvy_pics.html
>
> My own personal guess on the "hunting/pecking" problem is that it probably
> resides with aero-elastic issues and the swept back high aspect ratio wing.
> Given the newest carbon-kevlar+? materials, maybe the bending and torsional
> stiffness of a newer construction wing can help overcome some of these
> issues.... We will see if and when the SB-13 gets into the flight testing
> phase...
>
> RO
>

Thanks for taking time to write this up, Mike. It happens to be stuff I've
been interested in and wondered about for many years!

Bob W.

---
This email has been checked for viruses by AVG.
http://www.avg.com

Kiwi User

December 10th 17, 05:08 PM

On Sun, 10 Dec 2017 01:38:23 +0000, Michael Opitz wrote:

> That was my father who re-built and flew the Ho-IV in 1952 USA contests.
> He limited himself to no more than 80 mph IAS in order to keep away
> from the pitch "pecking" characteristics which made him uncomfortable.
> From the late 1930's until the mid 1940's,
> he was one of the world's top flying wing test pilots, so he knew
> exactly what he was doing when he flew the Ho-IV.
>
Most interesting stuff. Thanks for posting it. On a closer look, I see
exactly what you mean about that horrid lump of block foam that passes
for a subfin, but there's not enough detail to see how bad the tip is -
except that they haven't bothered to make and fit ailerons.

I've found out a little more about that Ho S.IV. It seems to have been
taken to Farnborough by the Royal Aircraft Establishment (RAE)'s Enemy
Aircraft Flight. These were the British equivalent of Rechlin and NACA.
At first I thought it had been collected by Philip Wills or Eric "Winkle"
Brown, but this wasn't the case.

Eric Brown flew it several times while it was at Farnborough as part of a
tailless research project. He liked it and especially to 'praying mantis'
pilot position. I can see that that odd yoke is tilted for roll control,
but what about elevator - do the handles link to that by rotating the
tube they're mounted on? Similarly, I can see the tow release at the
front of the canopy but have no idea where the airbrake and trim controls
might be.

Geoffrey de Havilland must have got the glider from the RAE after they'd
finished testing it. I never knew he was a glider pilot, so can only
assume that he heard of it due to his involvement with the DH.108 Swallow.

I thought Philip Wills had brought a number of gliders back from Germany
but misremembered that. He he visited the Wasserkuppe as a side trip with
the Air Transport Auxiliary and found a lot of gliders there in good
condition. He'd been after a Reiher but, when he found a bunch of Weihes
there he got two of them back to Farnborough - at the time the US forces,
whose zone included the Wasserkuppe, were planning to burn the lot
because some troops had killed or maimed themselves trying to do
untutored bungee launches off the hill so he thought he'd best save at
least some from the bonfire. However, by the time his two arrived at
Farnborough two months later the rest were still untouched in their
hangars, so I wonder if the threatened destruction ever happened.

Anyway, Philip Wills ended up owning one of the Weihes and flying it for
two years before he sold it to Dick Georgeson in NZ, who used it for his
early explorations of mountain wave on the Southern Alps. He flew it for
what I believe was the first significant XC in wave (1953) when he flew
it from Christchurch to Dunedin, getting Gold height in the process and
missing Gold distance by just 3km due to being released a bit too far
south.

Bruce, if you're reading this: does that Weihe still exist and if it
does, is it still airworthy and who owns it?

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

Kiwi User

December 10th 17, 05:46 PM

On Sun, 10 Dec 2017 17:08:41 +0000, Kiwi User wrote:

> I've found out a little more about that Ho S.IV. It seems to have been
> taken to Farnborough by the Royal Aircraft Establishment (RAE)'s Enemy
> Aircraft Flight. These were the British equivalent of Rechlin and NACA.
>
Minor correction: I meant that the RAE was approximately equivalent to
Rechlin or NACA and Edwards.

The Enemy Aircraft Flight was a similar gang to Watson's Whizzers. They
knew each other and worked together and were known to exchange aircraft
on occasion because they operated in different parts of Germany and
surrounding countries. For instance, the only flyable Arado 2324s were in
Denmark and northern Germany, so all of the ones now in the USA were
collected by the EAF. Two were then given to WW in exchange for letting
Eric Brown interview Goering and I think one or two others were passed on
by Farnborough.

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

Michael Opitz

December 11th 17, 12:55 AM

At 17:08 10 December 2017, Kiwi User wrote:

>>
>Most interesting stuff. Thanks for posting it. On a closer look, I see
exactly what you mean about that horrid lump of block foam that
passes for a subfin, but there's not enough detail to see how bad the
tip is - except that they haven't bothered to make and fit ailerons.

It looks like someone may have tried to make the tips "all flying"
control surfaces, as they appear to be skewed off axis somehow.
Also, IIRC, those are elevons (not ailerons) that are missing. IIRC,
the Ho-IV used a system whereby an outboard spoiler was
separately deployed on one wing (or the other) for roll and yaw
control. (in addition to the elevons)

>Eric Brown flew it several times while it was at Farnborough as part
of a tailless research project. He liked it and especially to 'praying
mantis' pilot position.

Dad found the praying mantis position ok, except for when he was
at the end of a long flying day, and his beard stubble started to
become irritated by the chin rest.

>I can see that that odd yoke is tilted for roll control,
but what about elevator - do the handles link to that by rotating the
tube they're mounted on? Similarly, I can see the tow release at the
front of the canopy but have no idea where the airbrake and trim
controls might be.

To be quite honest, I was 1-1/2 years old when Dad flew the 1952
nationals. I was left at home with friends. I never got to look at
a Ho IV cockpit with Dad in my adult life, so I can't answer your
questions. I'm sure that the fellow(s) who precisely rebuilt a
Ho IV a few years ago in Germany can answer those questions
though.

http://www.nurflugel.com/Nurflugel/Horten_Nurflugels/ho_iv/ho_iv_
Restoration/body_ho_iv_restoration.html

>Anyway, Philip Wills ended up owning one of the Weihes and flying
it for two years before he sold it to Dick Georgeson in NZ, who used
it for his early explorations of mountain wave on the Southern Alps.
He flew it for what I believe was the first significant XC in wave
(1953) when he flew it from Christchurch to Dunedin, getting Gold
height in the process and missing Gold distance by just 3km due to
being released a bit too far south.

Dad made one or two 500 Km flights in the Ho IV during the 1952
nationals. That finished his Diamond badge. (#1 Germany, #10
International)...He was still a German citizen at the time, and did
not pick up his USA citizenship until a few years later, although
that did not stop the SSA/USA from also claiming his badge,
awarding him USA #6....

RO

[email protected]

December 11th 17, 08:35 AM

The New Zealand Wheihe

[email protected]

December 11th 17, 08:38 AM

The New Zealand Weihe was restored and I beleive flown by Billy Walker some years ago and was hanging in the Terminal building at Queenstown until a few years ago. Not sure where it is now, it looked great. Apparently not what the council wanted in the terminal.
Tom Claffey
....

Kiwi User

December 11th 17, 02:03 PM

On Mon, 11 Dec 2017 00:55:27 +0000, Michael Opitz wrote:

> It looks like someone may have tried to make the tips "all flying"
> control surfaces, as they appear to be skewed off axis somehow.
> Also, IIRC, those are elevons (not ailerons) that are missing. IIRC,
> the Ho-IV used a system whereby an outboard spoiler was separately
> deployed on one wing (or the other) for roll and yaw control. (in
> addition to the elevons)
>
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.

> Dad found the praying mantis position ok, except for when he was at the
> end of a long flying day, and his beard stubble started to become
> irritated by the chin rest.
>
:-)

> To be quite honest, I was 1-1/2 years old when Dad flew the 1952
> nationals. I was left at home with friends. I never got to look at a
> Ho IV cockpit with Dad in my adult life, so I can't answer your
> questions. I'm sure that the fellow(s) who precisely rebuilt a Ho IV a
> few years ago in Germany can answer those questions though.
>
Fair enough. I didn't realise you were so young at the time.

> http://www.nurflugel.com/Nurflugel/Horten_Nurflugels/ho_iv/ho_iv_
> Restoration/body_ho_iv_restoration.html
>
Do you know if this replica was completed and flown? All I know about it
is in that article about the ongoing building project. About all I know
about it it that it is not the glider in NASM, which is the second IVb
prototype.

> Dad made one or two 500 Km flights in the Ho IV during the 1952
> nationals. That finished his Diamond badge. (#1 Germany, #10
> International)...He was still a German citizen at the time, and did not
> pick up his USA citizenship until a few years later, although that did
> not stop the SSA/USA from also claiming his badge,
> awarding him USA #6....
>
What a nice way to get Diamond distance!

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

https://scalesoaring.co.uk/VINTAGE/Documentation/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 here:

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

Last but not least, there's a great write-up on the restoration of the
example in the Deutsches Museum, Munich:

http://www.twitt.org/HoIVrest.htm

It has decent cockpit photos and says exactly how the control yoke
worked: it slid back and forth on a central tube for pitch and rocked
from side to side for roll control.

FWIW, the example in NASM seems to be the restored S.IVb 2nd prototype,
though its described as a VI both by NASM and elsewhere. It seems as
though these are interchangeable names for the same design.

The best comprehensive list of Horten designs I've found so far is on

http://www.nurflugel.com under

http://www.nurflugel.com/Nurflugel/Horten_Nurflugels/
horten_nurflugels.html

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

Andy Blackburn[_3_]

December 11th 17, 05:08 PM

Great stories Mike.

There is no greater gentleman in soaring (or aviation) than Rudy Opitz. I'm proud to have had the opportunity to know and fly with him during his life..

There's also Albion Bowers' work at NASA Armstrong on the Prandtl wing which has a lift distribution that appears to eliminate adverse yaw, and therefore (some of) the need for vertical stabilizers. Obviously Prandtl's ideas go way back to the early days of flight along with the above-described flying wing concepts. Not sure about the implications for crosswind landings and other practical concerns but it appears to work pretty well.

https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-106-AFRC.html

Andy Blackburn

Andreas Maurer

December 11th 17, 08:41 PM

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

[email protected]

December 11th 17, 10:39 PM

On Friday, December 8, 2017 at 9:52:07 PM UTC-6, Jonathan St. Cloud wrote:
> Anyone know how the Has anyone seen the Akaflieg Karlsruhe AK-X is coming along? Looked like a very interesting project.

An old movie of the 1952 National Contest in Grand Prairie, Texas USA is available on YouTube ...

https://www.youtube.com/watch?v=0M84AKSyGZk&list=UU5YlTf3vecBvsKgwjHtL11A&index=12

at 1:20 or so is Rudy Optiz flying his Horten IV

Bob

Jonathan St. Cloud

December 11th 17, 11:48 PM

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

Kiwi User

December 12th 17, 01:52 AM

On Mon, 11 Dec 2017 21:41:25 +0100, Andreas Maurer wrote:

> 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).
>
If a description I read many years ago of what makes a Hoerner tip work
and why its beneficial is true, then the spanwise flow shouldn't be a
problem.

I know that a lot of tip shapes were described as Hoerner tips, but the
one I'm talking has:

- a minimum LE sweep of 10 degrees on the outermost wing panel

- a straight edge to the tip raked outward toward the TE at at least
30 degrees and should meet the TE at an acute angle,
i.e. not rounded off

- the upper surface curves down to meet the lower surface at an acute
angle

The idea was that the LE sweep promoted spanwise flow toward the tip,
which was encouraged to oppose the tip vortex rotation as it slid over
the convex tip profile. The pointed at the end of the TE anchors the tip
vortex while the roll-down of top surface flowing spanwise out along the
panel and down over the tip shape will tend to move the tip vortex
outward.

I used this tip design for many years on competition free flight F1A
gliders. It worked for me. It was notable that, while models with
conventionally rounded tips needed a lot of tip washout to prevent tip
stalling, my design worked best with unwarped [flat] tip panels.
Directional stability was good too. Minimal fin area is beneficial to F1A
performance and thermal centering, the optimum being just big enough to
kill dutch rolling tendencies. On my design the fin had to be reduced to
a surprisingly small size before the first signs of dutch roll appeared.
Benefits of solid balsa fins: you keep chopping bits off until the dutch
roll appears and then stick the last bit back on.

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

Michael Opitz

December 12th 17, 03:30 AM

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

Michael Opitz

December 12th 17, 04:50 AM

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/Documentation/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 here:
>
>https://scalesoaring.co.uk/VINTAGE/Documentation/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

Andreas Maurer

December 13th 17, 12:24 AM

On Mon, 11 Dec 2017 15:48:44 -0800 (PST), "Jonathan St. Cloud"
> wrote:

> This project and Mu-31 are projects that seem like they have potential to develop new technology.

Absolutely.

Since you mentioned the Mu-31: Also an extremly interesting project,
much more consequent wing-root design than the JS-3, and since it's
otherwise identical to the ASW-27 it should be easy to compare the
benefits of the new design.

Andreas Maurer

December 13th 17, 12:27 AM

On Tue, 12 Dec 2017 01:52:24 +0000 (UTC), Kiwi User
> wrote:

Hi Martin,

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. :)

>The idea was that the LE sweep promoted spanwise flow toward the tip,
>which was encouraged to oppose the tip vortex rotation as it slid over
>the convex tip profile. The pointed at the end of the TE anchors the tip
>vortex while the roll-down of top surface flowing spanwise out along the
>panel and down over the tip shape will tend to move the tip vortex
>outward.
>
>I used this tip design for many years on competition free flight F1A
>gliders. It worked for me. It was notable that, while models with
>conventionally rounded tips needed a lot of tip washout to prevent tip
>stalling, my design worked best with unwarped [flat] tip panels.
>Directional stability was good too. Minimal fin area is beneficial to F1A
>performance and thermal centering, the optimum being just big enough to
>kill dutch rolling tendencies. On my design the fin had to be reduced to
>a surprisingly small size before the first signs of dutch roll appeared.
>Benefits of solid balsa fins: you keep chopping bits off until the dutch
>roll appears and then stick the last bit back on.
>

Andreas Maurer

December 13th 17, 12:34 AM

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

Michael Opitz

December 13th 17, 05:10 AM

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/Documentation/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 Zubertâ€™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 â€“ 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
Reimarâ€™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.

"NurflÃ¼gel", 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

Kiwi User

December 13th 17, 11:46 AM

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?

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?

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.

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

Jonathan St. Cloud

December 13th 17, 03:32 PM

This thread really highlights what a diverse interesting group, peoples the soaring world! I have immensely enjoyed not only the history told in this thread, but the technology these young engineers are exploring. Wish there was a way for non-German speakers to stay updated on the various Akaflieg projects. Thank you for all who shared!
Jon

[email protected]

December 13th 17, 03:42 PM

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

jfitch

December 13th 17, 05:06 PM

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.

Bob Salvo[_2_]

December 13th 17, 08:27 PM

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

Andreas Maurer

December 13th 17, 08:50 PM

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/photo/000724103.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.

Andreas Maurer

December 13th 17, 09:21 PM

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/Documentation/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.
>
>"NurflÃ¼gel", 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

Kiwi User

December 13th 17, 09:31 PM

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/photo/000724103.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

Kiwi User

December 13th 17, 09:46 PM

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

Andreas Maurer

December 13th 17, 10:02 PM

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

Michael Opitz

December 14th 17, 04:00 AM

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.
>>
>>"NurflÃ¼gel", 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 fÃ¼r's Angebot. Auf Deutsch geht's mir
auch noch recht gut.......

GruÃŸ,

RO

[email protected][_2_]

December 14th 17, 04:08 AM

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

Tango Whisky

December 14th 17, 05:40 AM

Yep, as I said in a post above, the oscillation was damped with an aft, but then the stall characteristics turned to nasty. Most of this nastiness was cause by spanwise flow during stall which caused the whole wing to stall very rapidly. We then installed the boundary layer fences (iirc two per wing), and things improved.

Tango Whisky

December 14th 17, 10:31 AM

Le jeudi 14 dÃ©cembre 2017 06:40:58 UTC+1, Tango Whisky a Ã©critÂ*:
> Yep, as I said in a post above, the oscillation was damped with an aft, but then the stall characteristics turned to nasty. Most of this nastiness was cause by spanwise flow during stall which caused the whole wing to stall very rapidly. We then installed the boundary layer fences (iirc two per wing), and things improved.

That should read aft cg.

There actually was another nasty effect (which probably will happen with the AK-X, too):
During the ground run of the aerotow, the SB13 would lift of before the tug (as usual with sailplanes). It would then eventually fly through the vortex which the tug leaves on the runway after rotation and pitch into the ground. This happened on the (inofficial) first flight, and the relation between vortex and pitch down was discovered on the video - there has been a thin layer of snow on the runway which made the vortex visible.
Same would happen if during tow the SB13 reached a somewhat low position and came to contact the downwash of the tug's wing and its vortex - the glider would pitch down and could only be stabilized in a typical low tow position.

So the counter measure was to aerotow with a long rope (80-100 m), brief the tug pilot to do a gentle rotation/lift-off, and stay in low tow position troughout the tow.

Michael Opitz

December 19th 17, 10:23 PM

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