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Two brothers, one wing.

by Philippe Ballarini
translation: Mike Leveillard

Before evoking the story of the Horten brothers and their strange machines, a review of some background is necessary.

As used as we are to visualize a traditional airplane with a fuselage, we are somewhat taken abashed when looking at a flying wing, and yet, its concept dates back from the dawn of aviation. The benefits of a flying wing become easy to understand when we consider that the fuselage and the tail section produce 30% to 50% of an airplane's drag, thus the reason that purists such as Lippisch or Northrop pursued this concept. The idea of a flying wing is far from being a novelty; it made its appearance at the birth of aviation, and it was a concept adopted by many precursors.

Another essential fact to keep in mind for the comprehension of the Horten brothers' work is to recall the importance that the glider and soaring played in the history of aviation.

While many researchers towards the end of the XIXth century were trying to create a motorized machine, some purists and grand precursors such as Lilienthal or Ferber believed that a flying machine should be aerodynamically efficient and easy to fly before installing an engine. We must note in passing that Lilienthal had conceived gliders without a tail section before the year 1900.

The Horten brothers would become the virtuosos of the flying wing, testing with stubbornness their machines without neither fuselage nor tail section in gliding flight before even thinking of adapting them with an engine. Obsession? Maybe…Whatever the reasons, they would design flying wings exclusively. No other type of flying machine would come out of their drawing board.

Born at the beginning of the 20th century, the brothers had developed from childhood a passion for the concept of a machine flying with the purest of qualities. The Versailles treaty of 1919 theoretically banned the rearmament of Germany, particularly by drastically limiting its aeronautical production. This is how glider flying and soaring in Germany came to play such an important part between the wars, not only in the training of pilots but also in aeronautical research. The renowned Wasserkuppe meetings would provide the perfect stage for the advancement of those researches.

It is within this time frame that Walter and Reimar Horten developed, and built their first flying wing before reaching the age of twenty after studying the work of von Prandlt (published in 1918) on aerodynamics with the emphasis on the benefits of the thick wing. They also benefited from indulgent parents that allowed them to transform the family's house living room into a workshop.

During the entire period that preceded the Second World War, the brothers conceived machines having constantly improved performance.

Their first glider, the Horten Ho I, was first flight tested at Bonn-Hagelar in July 1933. Although it was not a complete success, it opened the way for other models, including the Ho IV with a high aspect ratio wing of 24 meters in span, as well as their Ho III that soared to 7000 meters in 1938.

When the hostilities began in World War two, the Horten brothers were of course assigned to the Luftwaffe. Wolfram, the third brother was shotdown over Dunkerque flying a Heinkel He-111, whereas Walter flew Messerschmitt Bf-109 for 6 months. Reimar was also trained on the Bf-109 but he was soon transferred to a special unit preparing for operation "Sealöwe" (Operation Sea Lion) having for objective the invasion of England. For this operation the Luftwaffe had created a special glider unit. More than 80 aircraft, had been assigned to this operation to deliver ammunitions and supplies for the troops of the invasion force, it included five Ho III and two Ho II especially equipped for this mission. The third Reich had once again found in the gliding schools a mean of "feeding" its war machine.

We know now that the tenacity and dedication of the British RAF pilots caused the invasion of England to be cancelled indefinitely. The cancellation of operation "Sea Lion" actually benefited the Horten brothers, permitting them to continue their projects, whereas the glider pilot training center was transferred to Königsberg. They concentrated on the repairs of their damaged gliders, and to the development of new models supported by Ernst Udet.

In 1942, the Luftwaffe advised Reimar that it was searching for an aircraft, which they could use to test a Schmitt-Argus pulse jet engine. They asked him if he thought that le Ho V two-seater could serve that purpose. According to certain sources, this decision came about following reports from German spies in the USA regarding the work of Northrop. The Ho V structure did not permit such mean of high thrust propulsion so the Horten brothers returned to the drawing board and conceived a stronger and larger wing. It would be the Ho VII, a machine equipped with two "pusher" type propellers and a pulse jet engine.

This new venture did not stop the brothers from pursuing their fundamental researches. As Etrich in 1908, they would be intrigued by the "flying seed"
Zanonia Macrocarpia, which inspired them for the design of their amazing "Parabola".

But it was wartime and Göering was demanding his "1000X1000X1000". What was that all about? Nothing else than an airplane capable of transporting on a distance of 1000 kilometers from its base, 1000 kilos of bombs at a speed of 1000 kilometers per hour.
It was apparently a very unrealistic project for the era, but one that the Hortens (as well as other German engineers such as those from Focke Wulf) came very close to realizing and make operational.

Six months! That was the maximum time allowed to the brothers to have them conceive a prototype, including the assembly methods. It must be remembered that in 1944 the Luftwaffe was already in a desperate state. The glider prototype was ready in a very short time, built of materials consisting of plywood made with a special solvent resistant glue, and some parts of the machine were even made of composite material. Duraluminum had become a rare strategic material in Germany, and its use would have required highly qualified labor, which had been absorbed to serve on the battlefields.

On March 1st 1944, the Ho IX made its first gliding flight at Göttingen. A second machine had been built to be fitted with turbojet engines. Those turbojets promised for a March delivery were late to be delivered, and when they arrived it was a serious disappointment for the Horten brothers. They had been provided with Jumo 004B of 80 centimeters in diameter, whereas the planned jet engines were not supposed to exceed 60 centimeters! For a more classic machine such as the Me-262, it would not have been an insurmountable problem, but for a flying wing in which the jet engines were to be incorporated, it was a different problem. It would have been necessary to completely redesign the Ho IX, but time no longer permitted such a project. Or, it would have been necessary to substantially increase the wingspan, rendering the airplane unable to achieve the speeds adamantly required by Göering. The Horten brothers therefore resorted to "make do" ingenuity and the machine were ready for test flight at the end of 1944.

Test pilot Lieutenant Erwin Ziller's logbook shows that the first flight with the turbojet engines took place on February 2nd 1945, but Reimar Horten asserts that December 18th 1944 was the date of this particular flight.
The RLM (German Air Ministry) had shown satisfaction with the Ho IX, and giving it the code 8-229 it entrusted its construction to the Gothaer Waggonfabrik works. Twenty of the machine's first model was ordered. Several other models had been planned, including two-seaters for training, and night fighters equipped with radar.  We must note in passing that the Horten brothers had developed a special revetment for their Ho IX, made of glue, soot, and charcoal powder, making this already furtive machine practically undetectable with radar.

On April 14th 1945, the American army arrived at the production factory, capturing the Go 229 (Go for Gothaer the official designation) ending the construction of what had been the first jet propelled flying wing. One of those machines is located at the famed Smithsonian museum.

The Horten brothers did not wait for the arrival of the Americans, and as many of their compatriots, it is in Argentina that they would continue to develop their flying wing. Although they had been geniuses in the conception of airplanes, they had none the less been members of the Nazi party.
They went on to design unorthodox gliders, the Horten XV "Urubu" in particular and a giant transport glider the IAME I.A. 28, but only one of this machine was ever built.
Disregarding their political involvement more or less doubtful, the Horten brothers remain no less the "grand masters" of the flying wing.

Their stubbornness in their researches resulted in the production of a flying wing possessing great flying qualities, beginning with the first one produced to the last one, even introducing the piloting of the machine in a laying down position to reduce the extra drag produced with a normal canopy configuration.

Reimar Horten died in 1994. As for his brother Walter, his life ended in December 1998 in Baden-Baden.

And, what else can we say about the Horten brothers' Go 229 (or Ho IX or Ho 229)?
It was a furtive jet propelled flying wing, operational some decades before the F-117 "stealth" the airplane subject of so much publicity during the Gulf War.

Aérostories, 2001.

In 1914, Dunne flew his tailless biplane between London and Paris.
"L'Illustration"  Document    Click

Arnoux experimented his tailless monoplane at Issy in 1913-1914. It was an idea close to the flying wing.
"L'Illustration"  Document  Click

Otto Lilienthal was one of the grands aviation precursors. He is seen here performing a glide from the artificial hill especially built for his tests.  Document "L'Illustration"    Click

Walter Horten in 1929.
Reimar Horten Coll.  Click

High performance gliders atop the Wasserkuppe the world soaring's Mecca. In the foreground a Rheinsperber. The third Reich encouraged the development of glider flying and soaring which provided a formidable source of pilots for the Luftwaffe. Many pilots were trained there at this apparently innocent looking flight school, including the famed Adolf Galland.
Document  "L'Illustration"  Click

The Horten brothers beside their first glider: the Ho I. Reimar Horten Coll.   Click

Hanna Reitsch famed German aviatrix and hard core Nazi admiring the Ho III.
Reimar Horten Coll.  Click

The Ho IV, a superb flying wing with its 24 meters wingspan. Reimar Horten Coll.   Clic

Reimar Horten, Luftwaffe Officer
Coll. Reimar Horten  Click



The Horten Ho V. The similarity with the Northrop first flying wing prototype is striking.
Reimar Horten  Coll.

The Zanonia Macrocarpia grain had inspired in 1908 the creator of the famous Taube. Based on this principle the Horten brothers developed their Parabola.
Reimar Horten Coll.   Click

A Ho IX V1, prototype for the Go 229s. It represents the philosophy of the Horten Brothers: a flying wing glider in its purest form that would be eventually motorized.
Reimar Horten Coll.   Clic

A Ho IX under construction. This document depicts the wood construction of this flying wing. (The clamps are aligned on the left). The jet engines are fictitious.
Reimar Horten Coll.   Click

A Ho IX (Go 229) before a test flight. The out of proportion nose landing gear comes from a Heinkel He 177 heavy bomber.
Reimar Horten  Coll.  Clic

An unfinished G0 22 captured by American troops. Some of those machines were sent to the United States for studies. This photo shows the tubular structure and the wing's profile.
DITE / USIS    Click

The Ho IX-Go 229 was never operational but it came very close. A 1/72nd scale model of this machine is available from Revell.

Aerostories document.  Click