HORTEN IV RESTORATION

 
BACKGROUND
On August 14, 1999, the Deutsches Museum at Flugwerft Oberschleissheim held an open house to display a restored Horten IV before it went on public exhibition.  There were three presentations scheduled:  first was Reinhold Stadler on Horten design principles; second was Edward Uden on this history of Horten airplanes based on information from the Horten archives, and; third was Peter Hanickel (who rebuilt the center section) talking about this specific aircraft, its history and the restoration process.  Once the glider goes on display it will be hung from the roof, so this open house was the last chance for Horten enthusiasts to view it up close, including the interior sections.

Shortly after the open house Reinhold Stadler posted his views of the event, but he didn't have any pictures of the glider.  Fortunately, Eric du Trieu de Terdonck, who also attended, took a number of very fine pictures and forwarded them along to TWITT for publication on our web site.  So the following material is a compilation of both their work for your enjoyment.


 
Ho IV EVENT
   The H IV event on Saturday (8/14) at the Deutsches Museum, Flugwerft Oberschleissheim, is over.  We had a very interesting auditorium with more than 200 people. The finished H IV looks great. 
   Lots of very useful discussions, but unfortunately there was no time to go into detail with everybody.  It was a very inspiring mix of old Horten employees and pilots as well as young researchers and fans.  At least I have learned a lot and new work to do on the Horten airplanes.
   Some of the interesting names available (not sorted either by importance nor alphabet, nor complete as I had no chance to meet all): 

Mrs./ Mr. Nickel, sister of the Hortens, involved in design/Horten pilot and employee, involved in design process
Mrs./ Mr. Zuebert, Horten pilot and employee, later on pilot on the Bachem Natter
Mr. Mayensohn, Horten employee, saved one of the surviving H IV
Mr. Zacher, D-30 pilot on the companion H IV/D-30, flew Horten airplanes
Mr. Uden, runs the Horten archive
Mr. Hanickel, restorer of H IV 
Mr. Bentley, H IX researcher and member of Classic Books
Mr. Gapsch and Kehrer, experienced Horten model pilots with more than 100 Horten wings, have systematically solved the 
      adverse yaw on empirical basis
Mrs./ Mr. Mattlener, the PUL 10 is still alive!

   And I was lucky to meet some other friends of the Nurflugel-email list:

Mr. Ottens, well known H IX researcher
Mr. de Trieu de Terdonck, H IX researcher

   That's what I like!  Afterwards I realized from the guest book that others were here I would have liked to speak to:  Mrs. Ursula Horten with her son Kai.  She was the wife of Wolfram Horten, the third of the brothers.

   I had that many discussions that I even had no time to take photos.  So I will ask other to get some....
   One important person was missing, unfortunately: Mr. Scheidhauer, as his health is not good.  But I phoned with him on his birthday and he was already well informed. He would have liked to see that airplane ready after all this time....

Greetings,            Reinhold Stadler

Additional information from Reinhold:

(ed.  The question was asked about the relationship to this glider and those at the museum in Berlin as part of an exchange arranged by the NASM.  This is his response.)  Thanks for the info on the Berlin aircraft.  Fortunately I have already been able to see these airplanes (H II, H IIIf, H IIIh and H VI) and get some interesting details.  Yes, the H IV here in Munich is a different project.  This airplane never left Germany.  It is the W.Nr. 26, the airplane flown in the famous comparison against the D-30.  After the war the airplane was flown (with new, fixed outer wings) at the BAFO (the British forces in Germany) in Germany.  The CoG-winch towing tests were continued durig this time.  One of the pilots eventually damaged the left wing on landing, and the airplane was never flown again.  It went to a German gliding club, later on into private ownership.  Several  repair attempts were performed.  Finally the airplane was sold to the Deutsches  Museum, but only the wings arrived....


Full view of the Horten IV from the right wing.  On the lower part of the photo you can see Dr. Karl Nickel (black suit) and his wife (Horten's sister).

(Note:  What looks like something sticking out of the left wing is actually the cockpit hatch being suspended over the center section which will be clear as you thumb through the rest of the pictures.)


View of the Horten IV from the left wing.  In this view you can't clearly see the actual dimensions of the wing, but it is very large and the chord at the tip is very small (about your two hands together).  On the right of the wing you can see Mr. Hans Zacher (with the stick) talking with Dr. Nickel.

View of the central part of the wing with the air brakes open.  The jettisonable top hatch can be seen hanging above the cockpit area.  Under the aft part of the hatch (but not clearly visible) are Mr. Reinhold Stadler and Mr. B. Mattlener with his wife.

Bottom aft part of the Horten IV fuselage pod with all the data.  The data was reconstructed by Mr. Peter Hanickel with the help of old photos.  He found that there was a mistake in the book Nurflugel by Dr. Reimar Horten and Mr. P.F. Selinger.  The photos are shown on page 105 of the book and the mistakes are on pages 102 & 229.  The Werk-Nr. 26 is not D-10-1452, but D-10-1451.

View of the center section taken from the aft perspective.  This shows the seat (if it can be called that) and forward instrument panel.  There are other instruments on the control stick (not visible).  You can see the center section has been rebuilt in perfect condition.  Mr. Hanickel did this work with help from a set of 30 photos and a few drawings that still exist.  The space dedicated to the pilot is very small and during the presentation it was said the first Horten IV center section was designed around the pilot, Heinz Scheidhauer, who is not very big.  The next Horten IV had to be enlarged by 10cm, because it was too small.  I (Eric) could see this when Mr. Hans Zacher tried to get into the cockpit since he is a bigger man and didn't fit very well in the small space.  (ed. - You can also see the rudder peddles at the very bottom of the vee structure.  You can also see the armrest pads and large chest pad.)

Another shot from the aft side.  This give a clearer view of the top hatch shape so you can see the cockpit gets even smaller once it's in place.  (ed. - The area protruding down from the lower center of the hatch was probably were the parachute was stored.  The Horten IV tested at Mississippi State had some difficulties keeping the hatch secured during flight because of scant room between it and the pilot's back, with just a little movement causing it to separate.)

Here is more detail of the cockpit section.  The left part of the double stick is visible just off the upper left corner of the chest pad.  Unfortunately, there are no details on this stick.  This is a very interesting part of the aircraft because it is a very nice kinematic system.  As an engineer, I love this system.  It is a square block with instruments on top, a handle on each side, and slides fore and aft on a round tube.  (ed. - This shot also gives you a better look at the arm rests, chin pad and shoulder straps - vertical pieces on either side of the chin pad.)

A closer shot of the instrument panel and now you can see both the sticks at the forward edge of the chest pad.  (ed. - It almost gives you an idea of what it would be like to lay down in the cockpit and look out the front of the canopy.)

Mr. Hans Zacher at the command of the Horten IV.  He has the double sticks in his hands.  Dr. Karl Nickel can be seen standing in the background (long sleeve white shirt with bolo tie).  (ed. - This shot shows what Eric meant about the cockpit size for someone larger than the original pilot.  Obviously, the top hatch would not fit well with Mr. Zacher.)
(Reinhold Stadler - As you can see in the pictures, the H IV center section was quite narrow, the prototype was tailored to Mr. Scheidhauer. Even the series H
IV with slightly larger cockpit wss narrow, as you could see from Mr. Zacher trying it out. Consequently, the center section was enlarged on the H IV b again.)


 
Mr. Zacher making a comment after a remark coming from one of the spectators.  Mr. Hanickel is on the left side of the picture immediately behind the little girl.  (ed. - You can also get a better view of the top hatch from this angle and see the area for a parachute.  The whole thing looks a little claustrophobic for my taste.)

A view from front showing the nose gear.  The wheels are really a dolly that falls away upon takeoff.  The skid can then be retracted during flight.  Landing is on the front skid, which is lowered, and a rear skid that is built into the aft fuselage area.

This is the remains of a wing part from a Horten HoIVb. (Reinhold Stadler - Some short comments to the H IVb outer wing panel.  It's a part of the first H IVb, Werk .Nr. 40, which crashed, killing the Pilot, Mr. Strebel.  The piece is identified by the Werk. Nr. written on it.  It is severly damaged due to the crash and therefore incomplete.  The crash reports say that the airplane obviously encountered heavy wing oscillations which broke one of the wings (left?) apart. Unfortunately the pilot was not connected to the parachute, so Strebel was killed when jumping from the airplane.  The H IVb was a H IV derivative with laminar (Mustang)-wing sections.  Sweep was less than on the original H IV layout. The structure was significantly revised to fit series production standard.  Several components of the series were found at Thierstein at the end of WW 2.  The laminar wing with P-51 (it was a P-51D root section) was also used on the H  XII, look into the Nurflugel-book. This airplane was not extensivly flown due to the end of WW2. Interestingly, the H XII was not designed to the bell-shaped  lift distribution, which is a feature similar to the H IX.   After the war Reimar tried a laminar section again on the H Ib , but was not satisfied (lack of directional stability). The H Ic-layout has  the original Horten-sections again. Horten himself designed several laminar sections, but only a paper survived, missing the tabulated data.  The blue tubular frame (see below) in one of the final pictures of the Deutsches Museum shows a surviving one.  Unfortunately no data on the design survived.)

Remains of the center section from a Horten HoIVb.  I have no details on the history of these parts.  (ed. - This restoration was not part of that commissioned by the NASM, which is working through the Deutsches Technikmueum of Berlin.)

FOR MORE PICTURES TAKEN DURING THE CONSTRUCTION PHASE, CLICK HERE.

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