- In a speech before representatives of
the aircraft industry, Reichsmarshall Goering had announced that no new
contracts would be given, unless the proposed aircraft could carry 1000
kg bombs, fly 1000 km /h, and have a penetration depth of 1000 km; penetration
depth being defined as the total range.
- The Fighter Division requested that the
aircraft also be fitted with 30 mm machine guns, something that would lessen
the machine's efficiency as a bomber.
- "We started drawing and calculating
without a contract. Our plan was to build two full size prototypes. The
initial penetration depth would only be 800 km, since the fuel proof glue
necessary for the full wet wing, was not yet available. On the other hand,
the smaller fuel load allowed a doubling of the bomb load, so we went ahead
and submitted our proposal.
- A contract was awarded with the demand
that the first flight be made in six months! Since the jet engine was not
yet ready, the first machine would be a glider. The previously deactivated
Air Force Command IX was reactivated, and ordered to proceed with the project.
Fortunately, the preliminary work that we did without a contract, put us
sufficiently ahead, so the six month deadline locked feasible.
- There were several reasons for choosing
wood as the building material. Duraluminum required more energy to produce;
over 3000 KWH, versus less than 3 KWH for wood per ton. The required labor
for aluminum production was also much higher; 5000 hr/ton against 200 hr/ton
for wood. In addition, aural was difficult to find, and skilled sheet metal
workers in short supply. Unskilled workers could easier be trained to work
- Typically, a nose rib was built from
a triangular piece of spruce, sandwiched between two plywood sheets, all
scrap wood. Production time: 10 minutes. After the glue dried, the rib
was simply roused out along a master template in less that 5 minutes. The
rest of the wing was built in a similar crude fashion, to pave the way
for mass production by unskilled workers.
- The main box spar contained all cables
and control rods, to free the remaining space in the wing for fuel. That,
we planned to pump right into the wing itself, without tanks or bladders.
To do this, we needed the fuel-proof glue, that could be used to coat the
inside surfaces as well. The glue allowed additional gluing to dissolve
and adhere to already coated surfaces, which greatly simplified construction.
- The skin was very thick: 17 mm, all plywood;
three times the necessary strength. On the production aircraft, this would
be replaced by two 1.5 mm plywood sheets, with a 12 mm layer of sawdust,
charcoal and glue mix, sandwiched in between. The charcoal in this much
lighter skin would diffuse radar beams, and make the aircraft "invisible"
on radar (STEALTH Technology -ed).
- Finally, should a 20 mm shell explode
inside the wing, a relatively harmless hole would result, whereas a metal
wing would balloon out and lose its lift.
- The H IX wing was designed with 3 geometric
and 1.5 aerodynamic twist, to give it the desired bell shaped lift distribution
with all controls neutral. The Frise-nose on the elevons had proven to
be unsatisfactory, so we decided to use blunt nose elevons instead. The
sharply enlarged wing root chord served mainly to eliminate the middle-effect.
The maximum thickness line (T-4 line) therefore made a sharp bend in the
middle, which resulted in the characteristic pointed tail. As this would
affect stability, a test aircraft with large aspect ratio, that had the
control surface far outside the test area, was needed. The H Vl would serve
this purpose, while other preliminary tests were made with a H II and a
- The H IX V-1 took off right on schedule
on March 1, 1944 in Gottingen. The small He 45 towplane barely got off
the ground, so test pilot Scheidhauer released, and landed straight ahead,
after only a short hop. Five days later, he was off again on a snow covered
runway behind an infinitely more powerful He 111. He released at 12000
feet, made an uneventful glide back to the airport, then faced problems
during landing when the drag chute did not function. As the end of the
runway approached, he retracted the nose wheel, and skidded to a stop with
only minor damage.
- The second aircraft, scheduled to fly
three months later, was awaiting its engines, promised in March. Several
weeks passed, and then... Disaster!
- The engines arrived with an accessory
section added to the case, making the cross section oval, and the diameter
20 cm greater! No one had bothered to inform us! Now, just six weeks before
the first flight, we were faced with the problem of fitting an 80 cm engine
into an aircraft with a 60 cm hole in the spar! It meant that the wing
would have to be made thicker.
- To maintain the aerodynamic qualities
of our design, we would have to increase the span from 16 to 21.3 meters,
and the wing area from 42 m2 to 75 m2. Such an aircraft would never reach
the targeted performance, even with higher engine thrust. We choose instead
to do the best we could with patchwork modifications. The wings remained
the same. Another root rib was added 40 cm outside the original, making
the center section 0.8 m wider. The new airfoil was 13% thicker than before,
and the bend in the T-4 line became much larger. The thicker center section
lowered the critical Mach number to 0.75, or a maximum speed of 920 km/in.
- The ratio of movement between the control
column and the elevons could be reduced to by the pilot for high speed
flight. A small high speed drag rudder was supplemented by a larger one
that deployed after the smaller was fully extended. Many parts were scrounged
from other aircraft left at the test facility in Gottingen. The nose wheel,
for instance, came from the tail wheel of a He 177 heavy bomber. We were
even able to use the strut and retract cylinder!
- The men of Air Force Command IX did their
utmost to complete the aircraft before the end of 1944, sometimes working
more than 90 hours per week.
- I remember that Lt. Erwin Ziller made
the first flight about December 18th, 1944, but his log book indicates
that the first flight occurred on February 2nd., 1945. I am quite sure
the first flight of the H IX was also his first in a jet. Our leaders had
little concern for such risks.
- Satisfied with the initial flight, the
Air ministry ordered 40 aircraft to be built by the Goetha Waggonfabrik
under the designation Ho-229.
- It appears that the H IX V-2 had flown
three or four times before tragedy struck on February 18th. The many versions
of the story have a few things in common. The weather was overcast, the
ground soft and muddy. The visibility marginal for a test flight, as Lt.
Ziller took off, retracted the gear and disappeared. We received a report
that one engine had failed, and that the H IX was returning to Oranienburg.
Due to the low ceiling, a shallow approach to the airport was initiated.
Since the hydraulic pump was on the dead engine, gear and flaps were extended
by the emergency compressed air system. Once down, they could no. be retracted.
To maintain his glide slope, Lt. Ziller added power. to overcome the extra
drag, and found to his horror that he could "no longer maintain directional
control; the fully developed drag rudder unable to overcome the asymmetrical
thrust. Rather than lose control, he retarded the throttle to land short
of the runway. The aircraft touched down in a field, slid into an embankment
and flipped over, crushing its pilot.
- The US Third US Army Corps reached the
Goetha plant on April 14th 1945. Here they found the H IX V-3 intact and
nearly completed, and also the V-4, V-5 and V-6 in various stages of completion.
The Ninth US Armored Division found the H IX V-1 in good condition near
Leipzig. Its fate is unknown.
- The H IX V-3 was later shipped to USA,
and is now in the Smithsonian collection, awaiting restoration.
- More amazing pictures of the Ho IX