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The Horten Flying Wings

[The following was posted on a Usenet newsgroup by John Powell about 1994. If I have trespassed on anybody's copyright, please let me know. -- Daniel Ford]

Preliminary Remarks

The subject of "all-wing" aircraft is too extensive to be covered in depth here. Therefore, only the Horten H V, H VII and H IX (the latter also known as the Ho or Go 229) will be dealt with, all of which were twin-engined aircraft.

Doctor Reimar Horten, together with Dipl.Ing. Peter Selinger, has written about all of his aircraft in detail in the book Nurflugel (Weishaupt Verlag, Graz 1983). Major Walter Horten, at that time Technical Advisor of the General of Fighters in the Reichsluftfahrtministerium (RLM), made feasible the realization of his brother's designs.

Nothing New Under The Sun...

When the newest American super-bomber, the Northrop B-2, was revealed to the public at Palmdale, California on November 22, 1988, many aviation history enthusiasts must have noted that the configuration selected by the aircraft's designers, namely that of the "flying wing," had been resurrected from the dead, as it were. Although present day experience has shown that the all-wing configuration is the best one for avoiding detection by enemy radar (aided by the latest technology in materials, electronics and computers), the same configuration has been in practical use since about 1930. The first jet-powered all-wing aircraft flew in Germany on February 2, 1945, and at the time was also virtually undetectable by radar, partly on account of its mixed construction (wooden wings).

In the United States, John Knudsen Northrop had been working on all-wing aircraft since the end of the 1920s. His first aircraft of this configuration (although it did employ two small vertical tail fins on thin tail booms) was the "Flying Wing," which flew in 1929. Because of poor economic conditions during the 1930s, Northrop's twin-engined all-wing N1M did not appear until 1940, and the N9M until 1942.

Individual projects were undertaken in varlous countries, but in the Soviet Union there were numerous attempts, some of them very promising, to learn the secrets of the all-wing aircraft. The most successful Soviet designer was Boris Ivanovich Chernanovski, who developed a series of projects from 1921 to 1940.

In Germany, the Horten brothers, Reimar and Walter, had in mind a pure all-wing aircraft with no vertical control surfaces of any kind. Inspired by the Stork- and Delta-type tailless aircraft of Alexander Lippisch, they began their work at the end of the 1920s. Successful flight tests of their first tailless glider were carried out at Bonn-Hangelar airfield in July 1933. By 1934 they were working at Germany's "Gliding Mecca," the Wasserkuppe. The all-wing concept had achieved its first practical success.

Although development of the all-wing aircraft began at about the same time in Germany, the Soviet Union and America, there was no collaboration whatsoever between designers. In spite of this, design teams in these widely separated parts of the world were convinced that the all-wing aircraft was the best configuration and pursued the idea with much idealism. It is no wonder, therefore, that the concept has been revived in the present day.

The Northrop "Flying Wings" and the twin-engined Horten H V, H VII and H IX aircraft described herein can in a way be considered the forerunners of the B-2.

The H V was a pure research aircraft equipped with two counter-rotating pusher propellers: The H IX was designed as a twin-engined, turbojet fighter-bomber, and the H VII, also with two pusher propellers, was intended to serve as a trainer for jet aircraft. Detailed descriptions of the three types follow. Horten Va, W.-Nr. 5

The H Va was built in 1936/37 in cooperation with the Dynamit AG in Troisdorf, near Cologne. A synthetic material (Trolitax) were used in the aircraft's construction. Use of this material resulted in a series of problems, even though the glider Hol's der Teufel had previously been built using this method. Several of the solutions to these problems were patented by the Dynamit company. The nose of the H V was covered in clear Cellon and the two pilots occupied prone positions. The aircraft was fitted with a tricycle undercarriage with faired main members (only the nosewheel was retractable), and the two Hirth HM-60-R engines drove two-bladed pusher propellers directly (no extension shafts). The propeller manufacturer Peter Kempel produced the propellers from Lignofol (beech wood impregnated with synthetic resin). The H Va introduced novel movable wingtip control surfaces.

The aircraft's only flight took place at Bonn-Hangelar in early 1937. In the aircraft were Walter and Reimar Horten. The extreme aft location of the engines made the aircraft unstable, and at its low takeoff speed the aircraft's controls were unable to overcome the resulting tail-heaviness at the moment of rotation. The H Va became airborne briefly, then crashed, damaging the aircraft seriously. The injuries sustained by the two men were relatively minor (Walter Horten knocked out his two upper front teeth). Following the accident the Dynamit AG collected the remains of the H Va to carry out tests on the materials used in its construction.

Horten Vb, W.-Nr. 9

The H Vb was a research aircraft built at Cologne-Ostheim using conventional construction methods (wood and steel tube) on instructions from Major Dinort with the approval of Ernst Udet. As a result of the accident with the H Va, the movable wingtip controls were dispensed with and the designers turned to more conventional elevons. The Hirth engines of the unlucky H Va were used again, but were positioned further forward and drove their propellers vla short extension shafts, resulting in a more favorable weight distribution. The H Vb's pilots sat upright next to each other and were provided with individual raised canopies. Like the H Va, the H Vb had a fixed tricycle undercarriage. The aircraft's first flight took place at Cologne-Ostheim in autumn 1937 with Walter Horten at the controls. From the beginning of the war in 1939 until 1941 the aircraft was parked in the open at Potsdam-Werder airfield, which was not altogether beneficial for an aircraft built largely of wood.

Horten Vc, W.-Nr. 27

Efforts by the Luftwaffe-Inspektion 3 (Lln 3, or Luftwaffe Inspectorate for Fighters, whose Technical Department Head was Walter Horten) succeeded in convincing Generalflugzeugmeister Ernst Udet that it was advisable to retum the H V to flying status. In August 1941 a special detachment of Lln 3 was formed in Minden to oversee the reconstruction of the aircraft by the Peschke Firm. Peschke, a former WW I fighter pilot, had established a flying school at Hangelar and later an aircraft repair facility at Minden, The latter facility repaired aircraft such as the Fw 44 Stieglitz, He 72 Kadett, Fi 156 Storch and the RK Schwalbe. Peschke and the Horten brothers knew each other from Hangelar. In charge of the Lln 3 detachment was Luftwaffe Leutnant Reimar Horten. His team consisted of three designing engineers and five other men, including Heinz Scheidhauer, an experienced all-wing glider specialist. Later the special detachment was moved to Gottingen and enlarged to thirty men (soldiers, engineers, craftsmen and so on).

The Horten Vc was converted from the H Vb, which had been badly damaged by the elements. In Minden the two-seat H Vb became a single-seat aircraft. The pilot was accommodated in a normal seated position. The H Va's Hirth engines were retained, as were its steel tube and wood construction and fixed undercarriage. As property of the military, it was finished in standard Luftwaffe camouflage and was assigned the code PE + HO (PE for Peschke and HO for Horten).

The H Vc made its first flight on May 26, 1942. Walter Horten later flew the machine to Gottingen, where Luftwaffenkommando IX was being formed.

Flugkapitan Prof. Dr. Josef Stuper, then Director of the Instituts fur Forschungsflugbetrieb und Flugwesen (Institute for Flight Research and Aviation) at the Aerodynamischen Versuchsanstalt (AVA) Gottingen (Gottingen Aerodynamic Research Institute), carried out test flights in the H Vc. Late in the summer of 1943 an incident occurred involving the H Vc. Stuper took off from the center of the airfield with the aircraft's flaps in the down position. The aircraft's under-carriage struck the roof of a hangar and the H Vc crashed. Stuper escaped without serious injury, but the aircraft was badly damaged. It was subsequently stored at Gottingen in anticipation of restoration following the end of the war. Events were to prove differently, however, as all of the aircraft held there were assembled at the edge of the airfield and burned following Germany's surrender. A projected glider tug based on the H Vc was not built.

Horten VII, W.-Nr. 29

Construction of the H VII took place at the Gottingen Bureau. The aircraft's wings, which were of wooden construction, were built by the Lln 3 workshop, while the center section, which was of welded tube steel construction with Dural skinning, was manufactured by the Peschke Firm in Minden. The aircraft made its first flight in May 1943 with Heinz Scheidhauer and Walter Horten on board. The aircraft had originally been conceived as a flying test-bed for the Argus-Schmidt pulse-jet engine after the H V had proved unsuitable for the role. When this plan was abandoned it was proposed as a fighter training aircraft. The H VII was powered by two Argus AS-10-SC engines drivinq two-bladed constant-speed propellers via extension shafts. The aircraft featured a fully retractable twin nosewheel under-carriage. So-called "wingtip rudders" were used in place of a conventional rudder. The aircraft was assigned the RLM-Number 8-226. The aircraft's pilots were Heinz Scheidhauer, Erwin Ziller and Walter Horten. In autumn 1944 Oberst Knemeyer demonstrated the H VII to Hermann Goring at Oranienburg, after the Reichsmarschall had expressed a desire to see a Horten aircraft in action.

Knemeyer was the RLM flight-test chief and was favorably disposed toward the aircraft developed by the Horten brothers. Goring, a former WW I fighter pilot, had not participated in the later gliding boom and was unfamiliar with the aircraft which emerged from the program. He wanted to see the aircraft fly on one engine, which Heinz Scheidhauer did without any hesitation. The Reichsmarschall was impressed; the Peschke Firm received an order for twenty examples.

Construction of the H VII V2 began in 1944, but the aircraft had not been completed when the war ended. The V3, which was to see the "wingtip rudders" replaced by spoilers above and below the wings, as on the H IX, progressed no farther than the manufacturing of various components.

In February 1945 Heinz Scheidhauer flew the H VII to Gottingen. Hydraulic failure prevented him from extending the aircraft's undercarriage, and he was forced to make a belly landing. The resulting damage had not been repaired when, on April 7, 1945, US troops occupied the airfield. The aircraft presumably suffered the same fate as the H V and was burned.

Horten IX V1, W.-Nr. 38

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."

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. 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.

The assembled Horten 229 in 1950 with its wings attached to the body. Apparently they weren't intended for flight, and the aircraft that can be seen at the Udvar-Hazy Annex to the National Air & Space Museum is once again wingless.

Horten H IX V3, RLN-Number 8-229

The H IX V3 was an unarmed, twin-Jet, single seat aircraft. Further production of the fighter bomber was assigned to the Gothaer Waggonfabrik (GWF). Well-known for its Go 241 cargo glider, Gotha was considered the company best suited to manufacture Horten aircraft. The aircraft's turbojet engines were installed splayed 15 degrees left and right of the aircraft centerline and 4 degrees nose down. The new installation was tested in a center section mock-up. Construction of the H IX V3 was nearly complete when the Gotha Works at Friederichsroda was overrun by troops of the American 3rd Army's VII Corps on April 14, 1945. The aircraft was assigned the number T2-490 by the Americans. The aircraft's official RLM designation is uncertain, as it was referred to as the Ho 229 as well as the Go 229. Also found in the destroyed and abandoned works were several other prototypes in various stages of construction, including a two-seat version.

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.

Technical Data:

Sources

[My guess is that the writer took all his material from Dabrowski's book, and that the other sources are those cited by Dabrowski -- DF]

The Horten Flying Wing in World War II: The History & Development of the Ho 229, by H. P. Dabrowski, translated from the German by David Johnson. (Schiffer Military History Vol. 47, ISBN 0-88740-357-3)

Sources:

R. Horten/ P.F. Selinger: "Nurflugel", Graz 1983 D. Myhra: "Horten 229" Monogram Close-Up No. 12, Boylston 1983

B. Lange: "Typenhandbuch der deutschen Luftfahrttechnik", Koblenz 1986

T-2 Report ''German Flying Wings Designed by Horten Brothers", Wright-Patterson AFB 1946

W. Rosler: "Bericht uber den Fluganfall des Turbinen-Nurflugel-Flugzeuges Horten IX, V2... (1985, unpublished)

Working Discussion on the 229 Mock-up (13. 10. 1944)

DVL Short Report on the Testing of the Flying Characteristics of the Horten IX V-1 (Berlin-Adlershof, July 7, 1944)

Power Plant Installation in Go 229 (Horten), (V3+V5), March 7, 1945, Junkers Flugzeugl- und Motorenwerke A.G.

Flight Log of Lt. Erwin Ziller via Dr. Jorg Ziller

Correspondence with W. Horten, R. Horten, H.J. Meier, D. Myhra, K. Nickel, W. Radinger, R. Roeser, W. Rosler, H. Scheidhauer, P.F. Selinger, G. Sengfelder, R. Stadler.

Update

[Thanks to Geoff Steele of Arlington VA, I have this update on the Ho 229 at NASM. -- DF]

Just read, with great interest, your information on the Horten IX (Go-229). You may be interested to note that the Air & Space Museum in Washington has not only the center section of the V-3 airframe, but also a set of wings for it. There is some conjecture that the wings may not [have been] actually intended for flying (vs. the possibility they were built for static testing of the airframe by Gotha), as the fittings seem somewhat crude and it's not certain that all the control linkages are correct. We will see for sure when we attempt to mate the wings to the center section as the aircraft goes into the process of being restored for display in the new Udvar-Hazy facility at Dulles Airport. That restoration is probably a couple of years away, at least.

Your text mentions that the V-3 prototype has retractible gear and an "internal weapons bay for up to 2,000 lbs. of weapons." I don't believe this information is correct. I've extensively photographed that aircraft center section, and there is no "weapons bay" that I've observed. There is barely enough room for all three of the retractible wheels, due mainly to the large oversize nosewheel (that was a tailwheel of a Dornier bomber scarfed from a boneyard). By the time you retract that wheel rearward and tuck it behind the pilot, and retract the two mains inboard of the jets, there is no room left for 'bomb-type' weapons. There was barely room for the two cannon and their ammunition just outboard of the engines, and I don't believe the V-3 prototype even has those. I think it would have been intended for further flight testing of the airframe, and not a 'serious' armed fighter prototype for actual testing as a gun platform.

It's also interesting that there is a theory that due to instability of the aircraft around the yaw axis, it would not have been a good gun platform after all (especially if one cannon had jammed, which would have created adverse yaw when trying to hold a bead on a target). The pilot would have been unable to control yaw with any 'immediate' precision, thus keeping a stream of shells (with tracers) locked on a target at some range would have been quite difficult. This, then, might have seemed to argue against its value as a fighter, but it could have served a role as a ground attack weapon system because of its speed, slim "target" profile, and potential for carrying external stores.

Regards, Geoff Steel.

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