Horten Ho 229

Aircraft described as flying wing have aroused interest of the designers since the early, pioneer years of aviation.

This definition is used to describe aircraft with specific design solutions, allowing for resignation from conventional vertical and horizontal empennage and primarily from conventional fuselage. Virtually the whole airframe comprises only the wing, housing both the cockpit and powerplant. A sub-group of flying wings are tailless aircraft, differing from the traditional designs only in lack of horizontal empennage.

The first flying wings of the Horten brothers
The first designs of flying wings date back to 1784, when Carl Friedrich Meerwein of Freiburg tried to take to the air on a flying wing of his design. However, the first to patent the flying wing design in 1905 was Austrian Ignaz ”Igo” Etrich. His father was interested in aviation, after the death of Otto Lilienthal he purchased some of his gliders. Ignaz Taube founded his own aircraft factory at Wiener Neustadt airfield in 1909. His most famous design was Etrich-Rumpler Taube, built during 1910-1918 in numbers not smaller than 250 units.

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In 1910 Hugo Junkers patented his own version of the flying wing. It was the design of a huge passenger aircraft in flying wing configuration with thick profile, housing the passenger cabin, flight deck and engines driving pushing propellers. According to Junkers’ assumptions the flying wing configuration had better aerodynamic characteristics than traditional designs and allowed for reduction of interference drag due to elimination of drag of non-lift producing elements, which was to ensure attaining higher speeds in case of use of more powerful engines, or economical cruise speeds with less powerful powerplants. The flying wing configuration reduced also the aircraft’s empty weight which allowed for carrying heavier useful load at the same wing area or greater amount of fuel, which automatically increased the aircraft’s range. Since the characteristics described above increased proportionally to aircraft’s size, this solution was most profitable for very large aircraft.
The specific flying wing configuration required pioneer solutions for maintaining stability and control the aircraft. The longitudinal stability could be provided by selection of proper wing profiles or application of proper shape and twist of the wing. Lateral controllability was to be provided by vertical stabilizers on the wingtips or anhedral of the wing outer sections.

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Due to limitations imposed by Allied powers concerning construction of aircraft in Germany after the First World War further Junkers designs providing for the application of the flying wing configuration remained on the drawing boards. Most of the designs provided for construction of huge passenger aircraft, capable of carrying several hundreds of passengers.
Another German designer interested in flying wings was Alexander Martin Lippisch born on 2 November 1884 in München (Munich), who after the First World War was employed at Zeppelin works. However Lippisch focused on tailless aircraft and development of the delta wing.
Only in 1930s brothers Reimar and Walter Horten decided to use the flying wing design in practice. The Horten family came from Bonn, the father. Max Horten was a professor in philology, theology and philosophy at the local university and mother, Elisabeth, studied geography at Oxford University. Walter Horten was born on 13 November 1913, and Reimar Horten on 12 March 1915. Their elder brother Wolfram Horten, born on 3 March 1912 passed to them the interest in aircraft modeling during their childhood. The youngest child in the family was the sister, Gunildine.
As early as 1927 Walter and Reimar Horten enrolled in the nearby Fliegen Gliding Association (Segelflugverein Fliegen). Apart from learning to fly the brothers were fascinated with technical novelties in aviation. They were particularly intrigued by the work of Alexander Lippisch, who designed tailless aircraft and flying wings.

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In 1931, after turning 16 Reimar Horten, along with his 18-years old brother began work on their first glider in flying wing configuration, named Horten Ho I „Hangwind”. Components of the prototype were made by both brothers in the family house at Venusbergweg 12 in Bonn and the final assembly was done in a hangar at Bonn-Hangelar airfield.
The glider’s design was based on earlier works of Alexander Lippisch. It was a single seat flying wing in shape of thick profile flattened delta. The middle section housed faired cockpit. The construction was wooden, the forward section was covered with plywood and the rest with fabric. Ailerons and flaps occupied the entire trailing edge and were actuated by wires. The wing loading was very low, only 10 kg/m2.
Even during the work on the first prototype it turned out that the younger Reimar Horten is a very talented designer with great theoretical knowledge and keen on using new solutions in practice, while Walter Horten was a great organizer and outstanding pilot.
The prototype Horten Ho I was completed in the spring of 1933 and made its maiden flight at Bonn-Hangelar airfield in summer that year. It turned out that the glider has problems with longitudinal stability. Problems with stability were partially solved by adding an extra ballast in the nose, which allowed to shift the center of gravity forward. By spring of 1934 Horten Ho I made several short flights in total time of two hours. The glider’s flight characteristics were rather poor, problems with longitudinal stability persisted. In June 1934 during gliding competition at Bonn-Hangelar Reimar Horten, piloting Ho I glider obtained the certificate of airworthiness for it. Following it the glider was entered into civil aircraft register as D-Hangwind.

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Thanks to registering the glider, it could be officially submitted for gliding competition on Wasserkuppe mountain in Rhön Mountains in Hessen, when the largest German gliding center was located. At that time Walter Horten had already begun his military service in Wehrmacht, while Reimar Horten still attended school. While on leave, Walter Horten towed the Ho I glider, flown by Reimar Horten with a light airplane to Wasserkuppe. There was bad weather enroute and Reimar damaged the glider on landing. Luckily, the damage was not severe and the glider was repaired two days before the end of the contest. Horten Ho I did not take a prized place in the competition, but was awarded a 600 RM prize for original design. It refunded the expense of 320 RM for its construction and gave the brothers initial capital for further activities.
Since Walter Horten had to return to his unit after the leave, Reimar had no possibility to take the glider home after the contest. He contacted Alexander Lippisch, who at that time was the head of Technical Department of German Research Institute for Gliding (Deutsche Forschungsanstalt für Segelflug) and offered cost free handover of the Horten Ho I to the institute. Lippisch was not interested in the gift of the young designer, who was left with no other choice but to burn his construction on the periphery of the airfield.
The second design of the Horten brothers was Horten Ho II ”Habicht” (hawk). The commencement of the work on the new airframe coincided by publishing results of his studies on tailless aircraft by Lippisch. In his essay Lippisch described a method of mathematical calculation helping to obtain optimum wing design, created by Professor Ludwig Prandtl. Reimar Horten took the advantage of opportunity of hearing Lippisch’s lectures in person during his visit at Bonn University. In 1935 Reimar Horten himself commenced mathematical studies in Bonn.

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