Horten Ho IX (Go 229) In Detail
In the 1930s the Horten brothers had become interested in the all-wing design as a method of improving the performance of gliders. The all-wing layout removes any "unneeded" surfaces and –in theory at least– leads to the lowest possible drag. For a glider low drag is very important, with a more conventional layout you have to go to extremes to reduce drag and you will end up with long and more fragile wings. If you can get the same performance with a wing-only configuration, you end up with a similarly performing glider with wings that are shorter and thus sturdier.
Walter and Reimar Horten were pioneers of the tailless all-wing aircraft, and built a succession of beautifully graceful sailplanes with outstanding performance in 1936-40, followed by examples with two pusher engines. Their practical experience in building flying wing aircraft was at that time unique in the world. In 1943 Walter Horten became interested in constructing a high-speed aircraft of wooden construction. Reports from Prof. Lippisch's DFS 194 (later Me 163) tests at Peenemunde convinced him that even wooden aircraft could carry jet or rocket engines.
In 1943 Reichsmarschall Göring issued a request for design proposals to produce a bomber that was capable of carrying a 1000 kg load over 1000 km at 1000 km/h; the so called 1000/1000/1000 rule. Conventional German bombers could reach Allied command centers in England, but were suffering devastating losses, as allied fighter planes were faster than the German bombers. At the time there was simply no way to meet these goals; the new Jumo 004B jet engines could give the speed that was required, but swallowed fuel at such a rate that they would never be able to match the range requirement.
A beautiful illustration of the production Ho IX (also known as the Go 229)
This picture is the cover from the model made by Dragon Models Limited (DML)
[1/48 Master Series: Kit#5505 Ho229A-1 Flying Wing].
The model has won several awards and has great detail on it,
including detailed engines, guns, decals, and some metal parts.
The Hortens felt that the low-drag all-wing design could meet all of the goals – by reducing the drag, cruise power could be lowered to the point where the range requirement could be met. They put forward their current private (and jealously guarded) project, the Ho IX, as the basis for the bomber. The Government Air Ministry (Reichsluftfahrtministerium) approved the Horten proposal, but ordered the addition of two 30MM cannon, as they felt the aircraft would also be useful as a fighter due to its estimated top speed being significantly higher than any allied aircraft.
Horten IX V1, W.-Nr. 38
The first prototype Horten IX V1 was built as a glider and was intended for stability tests. It was completed in only six months, and test-flown for the first time in February 1944 in Göppingen.
Walter Horten was aware of the performance achieved by the DFS 194 rocket-powered research aircraft, and thus knew that wooden construction methods were suitable for high-performance aircraft. After seeing the Me 262 in March 1943 he set out to acquire information on the Jumo 004 turbojet engine. Further work on the H VII was abandoned and all efforts were concentrated on the H IX, which originated from Goring's 1000x1000x1000 demand, in which the Reichsmarschall specified that no new project would be considered unless it achieved the following performance figures: a speed of at least 1,000 kph and the ability to carry a 1,000 kg bomb load 1,000 km into enemy territory. Justifiable deviations from these figures would be accepted. At that time Walter Horten was a Hauptmann on the staff of Lln3. He managed to obtain a transfer to Gottingen, where he took over command of Luftwaffenkommando IX. Soon afterward, however, the Kommando was officially disbanded, and as a result Lln3 ceased to be the office responsible for development of the Horten projects. New life was injected into the Horten Firm, when, in August, Hermann Goring informed the company that work on the H IX turbojet fighter-bomber was to proceed with all urgency and that it was to construct a flyable, but unpowered, example as soon as possible.
Luftwaffenkommando IX, which officially no longer existed, continued to be funded and carried on its work, but without direct influence from the Technischen Amt of the RLM. The H IX V1 was an unpowered research glider and received the RLM-Number 8-229. The aircraft was of mixed construction (welded steel tube and wood) and was covered with several layers of plywood of various qualities, the outer layer being of the best quality. This method of construction made radar detection of the aircraft extremely difficult. The pilot was accommodated in a normal seated position. The first flight of the V1 took place on March 1, 1944, at Gottingen with Heinz Scheidhauer at the controls. Following several towed takeoffs, the aircraft was sent to Oranienburg near Berlin for flight testing, with Scheidhauer as pilot. A brief report submitted by the DVL on April 7, 1944, indicated that the aircraft provided an excellent gun platform.
In order to simulate the stabilizing effect of the engines, which were absent from the V1, the aircraft's main undercarriage legs were faired from the outset; only the aircraft's nosewheel was retractable. On March 5 the nose gear failed after it developed a wobble on Oranienburg's concrete runway. A special pressure suit was to have replaced the absent cockpit pressurization, but was never used in practice.
The machine was sent to Brandis, where it was to be tested by the military and used for training purposes. It was found there by soldiers of the US 9th Armored Division at the end of the war and was later burned in a "clearing action."
The second aircraft, scheduled to fly three months later, was awaiting its engines, promised in March 1945. Reimar Horten says in his biography:
In March 1943, the performance curves and installation drawings for the Junkers 004 jet engine came into our hands. Walter had seen the Me 262, and obtained data that had previously been kept secret. Work on the Ho VII was put aside, as we eagerly sought to submit a proposal for the 1000-1000-1000 jet that Reichsmarshal Goering had requested. Our proposal was accepted, and the Reichsmarshal ordered the first Ho IX (8-229) to be flown within six months.
The Ho IX contract generated a flurry of activity that none of our workshops could handle alone. Thus, the work was spread out, and efficiency suffered. For flight tests, a Ho III was modified with 60 sweep back to become the Ho XIII a, and two high aspect ratio Ho Vl's were built in Aegidienberg for "middle-effect" testing.
Despite the hardships, the Ho IX V-1 flew in March 1 as a glider, precise on schedule. The jet powered V-2 was scheduled to fly three months later." 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.
On the more conventional Me 262, this would not have been a problem, as the jet engines were attached under the wing. But for the Horten IX where the jet engines were to be integrated in the wing, it meant that the whole plane had to be redesigned.
After the first successful flight of the Ho IX V-2, the Ho VIII project was approved, and the aircraft was half finished when the war ended. The production contract for the Ho IX was awarded to the Gothaer Waggonfabrik.
Horten IX V2 being prepared for the first flight.
Horten HIX, Werk-Nr.9, 1944/45
The H IX V2 was a test machine powered by two Jumo 004 turbojets and was assigned the RLM number 8-229. It was the world's first turbojet-powered all-wing aircraft. The V2 had a fully retractable undercarriage and was unarmed. The pilot was accommodated in a conventional seated position.
Serious difficulties and delays in construction arose when the planned BMW 003 engines had to be replaced by more powerful Jumo 004s. The diameter of the Junkers engine was greater than that of the BMW product, requiring redesign of the engine bays. Like its predecessors, the aircraft was of mixed construction. The V2's undercarriage consisted of the tailwheel from a wrecked He 177 bomber, which was used as nosewheel, and the main undercarriage from a Bf 109 fighter.
The first test flight was made from Oranienburg on February 2, 1945, with Leutnant Erwin Ziller at the controls, and lasted about 30 minutes. It showed reportedly very good handling qualities, with only a shade of lateral instability. The Horten brothers had known Ziller from the competitions at the Wasserkuppe. Ziller had familiarized himself with all-wing aircraft in December 1944 and January 1945, making several flights in the Horten H IX V1 glider (an He 111 served as glider tug) and the twin-engined Horten H VII at Oranienburg.
Ziller spent the last three days of December 1944 at Erprobungsstelle Rechlin, where he made a total of five flights in the Me 262. These flights provided Ziller with an opportunity to become familiar with the operation and characteristics of the Jumo 004 turbojet engine.
At the end of a second successful test flight on February 3, 1945, Ziller deployed the aircraft's braking parachute too soon on his landing approach. The result was a hard landing which damaged the aircraft's main undercarrlage. Consequently, the third test flight in the Horten H IX did not take place until February 18, 1945. Returning after about 45 minutes in the air, Ziller was seen to dive the aircraft and pull up several times at an altitude of about 800 meters, apparently in an effort to relight an engine. The undercarriage was lowered unusually early, at an altitude of about 400 meters. The V2's speed decreased and, accompanied by increasing engine noise, its nose dropped and the aircraft entered a right-hand turn. The H IX completed a 360 degree turn with its wings banked 20 degrees. It then accelerated and completed a second and third 360 degree turn, the angle of bank increasing all the while. As it began a fourth circle, the aircraft struck the frozen turf beyond the airfield boundary.
Walter Rosler was the first Horten employee to reach the crash site, about two-and-a-half minutes after the accident. In his report he stated: "The first thing I saw was the two Junkers engines lying on the other side of the embankment. I could hear the turbine running down in the still-warm left power plant, while there was not a sound from the cooled-off right engine which lay beside it. . ." There was a strong smell of fuel, but no fire. Other than the jet engines and plexiglass cockpit hood, the aircraft had been completely destroyed. Like the engines, Ziller was ejected from the aircraft on impact. He was thrown against a large tree and killed instantly. Ziller had not used his radio, and had continued to fly the aircraft with an engine out and the undercarriage extended. He did not attempt to use his ejection seat and parachute to safety, and the aicraft's canopy was not jettisoned. It seems certain that he was attempting to save the valuable aircraft.
What had happened? The empty compressed air bottle in the wreckage confirmed that the undercarriage had been lowered with compressed air after a loss of hydraulic power following the failure of an engine. Had there been a stall, beginning at the right wingtip? Had the test pilot been rendered unconscious and unable to react by carbonizing oil from the remaining engine, which had eventually overheated? (There were no bulkheads separating the cockpit from the engine bays.)
Unfortunately, only Leutnant Ziller could have answered these questions, and he had failed to survive. In the opinion of the investigating experts sabotage could not be ruled out.
Almost-completed Go 229 V3 as found by the American troops in Fredrichsrode factory.
Horten H IX V3, RLN-Number 8-229
Despite of this setback the project continued with sustained energy. The prototype shop has been moved to Gothaer Waggonfabrik (Gotha) in Friedrichsrode. In March 1945 work commenced on the third prototype, the Go 229 V3. The V3 was larger than previous prototypes, the shape was modified in various areas, and it was meant to be a template for the pre-production series Go 229 A-0 day fighters, of which 20 machines had been ordered. The Go 229 A-0 pre-production aircraft were to be powered by two Junkers Jumo 004B turbojets with 1,962 lbf (8.7 kN) thrust each. The maximum speed was estimated at an excellent 590 mph (950 km/h) at sea level and 607 mph (977 km/h) at 39,370 ft (12,000 m). Maximum ceiling was to be 52,500 ft (16,000 m), although it is unlikely this could be met. Maximum range was estimated at 1180 miles (1,900 km), and the initial climb rate was to be 4330 ft/min (22 m/s). It was to be armed with two 30 mm MK 108 cannon, and could also carry either two 500 kg bombs, or twenty-four R4M rockets.
The V3 was sent to the United States by ship, along with other captured aircraft, and finally ended up in the H. H. "Hap" Arnold collection of the Air Force Technical Museum. The all-wing aircraft was to have been brought to flying status at Park Ridge, Illinois, but budget cuts in the late forties and early fifties brought these plans to an end. The V3 was handed over to the present-day National Air and Space Museum (NASM) in Washington D.C.
The Ho-229's design employed a thoroughly modern wing shape far ahead of its time. The wing had a twist so that in level flight the wingtips (and thus, the ailerons) were parallel with the ground. The center section was twisted upwards, which deflected air in flight, and provided the majority of its lift. The only existing Ho-229 airframe to be preserved was V2, and it is located at the National Air and Space Museum (NASM) in Washington D.C. The airframe V1 crashed during testing, and several partial airframes found on the assembly line were destroyed by U.S. troops to prevent them from being captured by advancing Russian troops.
This is how the sole remaining Go 229 flying wing is stored today.
It appears complete, but has been disassembled.
Wings are detached, and wheels have been removed from all three undercarriage legs.
Side view of the fuselage (centerplane?) reveals a great deal of internal wing structure.
Basically, Hortens designed their aircraft as they wood design a wooden glider.
This profile view also shows the way in which the two engines are ingeniously hidden within the wing.
Looking at the same part of the aircraft from the rear.
The swastikas appear not to be a part of the original paint scheme.
The wooden-covered parts of the airframe are not in good condition.
Hopefully the full restoration program for the Go 229 to be restored to display condition will commence soon.
Another view of the tail shows a pronounced fuselage spine,
and the blast tubes of two Jumo engines.
Two close-ups showing a distinctive profile of the nose, engine intakes and windscreen.
A glimpse into the main undercarriage well. The untidy layout is apparent.
The front wheel was, unusually, of massive dimensions,
designed to carry the bulk of the aircraft's weight and landing stress.
The aircraft's swept-back wings are stored separately. The wings are entirely plywood-covered.
Of note is that the ailerons and flaps have been removed from their hinges.
The hinges attachment points can be seen at the trailing edge of the nearer wing.
Wing cross-section and attachment gear.
To the right of the wing there is also a set of ailerons and flaps mentioned above.
Everything about this aircraft was unusual, even the shape of the cockpit canopy.
The armoured glass plate was to be built-in behind the curved windscreen,
much in the way it was done on Me 163 rocket fighter.
