Horten Ho 229
Encyclopedia
The Horten H.IX, RLM designation
RLM aircraft designation system
The German Air Ministry had a system for aircraft designation which was an attempt by the aviation bureaucracy of the Third Reich to standardize and produce an identifier for each aircraft type produced in Germany...
Ho 229 (often called Gotha Go 229 due to the identity of the chosen manufacturer of the aircraft) was a late–World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
prototype fighter
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
/bomber designed by Reimar and Walter Horten
Horten brothers
Walter Horten and Reimar Horten , sometimes credited as the Horten Brothers, were German aircraft pilots and enthusiasts, and members of the Hitler Youth and Nazi party...
and built by Gothaer Waggonfabrik
Gothaer Waggonfabrik
Gothaer Waggonfabrik was a German manufacturer of rolling stock established in the late nineteenth century at Gotha. During the two world wars, the company expanded into aircraft building.-World War I:...
. It was the first pure flying wing
Flying wing
A flying wing is a tailless fixed-wing aircraft which has no definite fuselage, with most of the crew, payload and equipment being housed inside the main wing structure....
powered by a jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
.
It was given the personal approval of German Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
Reichsmarschall
Reichsmarschall
Reichsmarschall literally in ; was the highest rank in the armed forces of Nazi Germany during World War II after the position of Supreme Commander held by Adolf Hitler....
Hermann Göring
Hermann Göring
Hermann Wilhelm Göring, was a German politician, military leader, and a leading member of the Nazi Party. He was a veteran of World War I as an ace fighter pilot, and a recipient of the coveted Pour le Mérite, also known as "The Blue Max"...
, and was the only aircraft to come close to meeting his "3×1000" performance requirements, namely to carry 1000 kg of bombs a distance of 1000 km with a speed of 1000 km/h. Its ceiling was 15,000 meters (49,213 ft).
In recent years it has become commonplace to describe this design as the first aircraft to incorporate what is now known as stealth technology
Stealth technology
Stealth technology also termed LO technology is a sub-discipline of military tactics and passive electronic countermeasures, which cover a range of techniques used with personnel, aircraft, ships, submarines, and missiles, to make them less visible to radar, infrared, sonar and other detection...
. but this is not the case, since the primary aim of the Horten brothers was to create an aeroplane that eliminated as much parasitic drag as possible, thus employing a shallow flying wing design. This relied heavily on experience gained with tailless gliders tested since the mid-1930s. However, there was an intention to introduce anti-radar measures that were not part of the initial design.
Design and development
In the early 1930s, the Horten brothersHorten brothers
Walter Horten and Reimar Horten , sometimes credited as the Horten Brothers, were German aircraft pilots and enthusiasts, and members of the Hitler Youth and Nazi party...
had become interested in the flying wing design as a method of improving the performance of gliders
Glider (sailplane)
A glider or sailplane is a type of glider aircraft used in the sport of gliding. Some gliders, known as motor gliders are used for gliding and soaring as well, but have engines which can, in some cases, be used for take-off or for extending a flight...
. The German government was funding glider clubs at the time because production of military and even motorized aircraft was forbidden by the Treaty of Versailles
Treaty of Versailles
The Treaty of Versailles was one of the peace treaties at the end of World War I. It ended the state of war between Germany and the Allied Powers. It was signed on 28 June 1919, exactly five years after the assassination of Archduke Franz Ferdinand. The other Central Powers on the German side of...
after World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
. The flying wing layout removes any "unneeded" surfaces and, in theory at least, leads to the lowest possible drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
. A wing-only configuration allows for a similarly performing glider with wings that are shorter and thus sturdier, and without the added drag of the fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
. The result was the Horten H.IV.
In 1943, Reichsmarschall Göring issued a request for design proposals to produce a bomber that was capable of carrying a 1,000 kg (2,200 lb) load over 1,000 km (620 mi) at 1,000 km/h (620 mph); the so called "3 X 1000 project". Conventional German bombers could reach Allied command centers in Great Britain, but were suffering devastating losses from Allied fighters. At the time, there was no way to meet these goals — the new Junkers Jumo 004B
Junkers Jumo 004
The Jumo 004 was the world's first turbojet engine in production and operational use, and the first successful axial compressor jet engine ever built. Some 8,000 units were manufactured by Junkers in Germany during late World War II and powered the operational Messerschmitt Me 262 jet fighter,...
turbojets could provide the required speed, but had excessive fuel consumption.
The Hortens concluded that the low-drag flying wing design could meet all of the goals: by reducing the drag, cruise
Cruise (flight)
Cruise is the level portion of aircraft travel where flight is most fuel efficient. It occurs between ascent and descent phases and is usually the majority of a journey. Technically, cruising consists of heading changes only at a constant airspeed and altitude...
power could be lowered to the point where the range
Range (aircraft)
The maximal total range is the distance an aircraft can fly between takeoff and landing, as limited by fuel capacity in powered aircraft, or cross-country speed and environmental conditions in unpowered aircraft....
requirement could be met. They put forward their private project, the H.IX, as the basis for the bomber. The Government Air Ministry (Reichsluftfahrtministerium) approved the Horten proposal, but ordered the addition of two 30 mm cannons, as they felt the aircraft would also be useful as a fighter due to its estimated top speed being significantly higher than that of any Allied aircraft.
The H.IX was of mixed construction, with the center pod made from welded steel tubing and wing spars built from wood. The wings were made from two thin, carbon-impregnated plywood
Plywood
Plywood is a type of manufactured timber made from thin sheets of wood veneer. It is one of the most widely used wood products. It is flexible, inexpensive, workable, re-usable, and can usually be locally manufactured...
panels glued together with a charcoal and sawdust mixture. The wing had a single main spar, penetrated by the jet engine inlets, and a secondary spar used for attaching the elevons. It was designed with a 7g load factor and a 1.8x safety rating; therefore, the aircraft had a 12.6g ultimate load rating. The wing's chord/thickness ratio ranged from 15% at the root to 8% at the wingtips.The aircraft utilized retractable tricycle landing gear
Tricycle gear
Tricycle gear describes an aircraft undercarriage, or landing gear, arranged in a tricycle fashion. The tricycle arrangement has one wheel in the front, called the nose wheel, and two or more main wheels slightly aft of the center of gravity...
, with the nosegear
Undercarriage
The undercarriage or landing gear in aviation, is the structure that supports an aircraft on the ground and allows it to taxi, takeoff and land...
on the first two prototypes sourced from a He 177
Heinkel He 177
The Heinkel He 177 Greif was the only operational long-range bomber to be operated by the Luftwaffe. Starting its existence as Germany's first purpose-built heavy bomber just before the war, and built in large numbers during World War II, it was also mistakenly tasked, right from its beginnings,...
's tailwheel system, with the third prototype using an He 177A main gear wheelrim and tire on its custom-designed nosegear strutwork and wheel fork. A drogue parachute
Drogue parachute
A drogue parachute is a parachute designed to be deployed from a rapidly moving object in order to slow the object, or to provide control and stability, or as a pilot parachute to deploy a larger parachute...
slowed the aircraft upon landing. The pilot sat on a primitive ejection seat. It was originally designed for the BMW 003 jet engine, but that engine was not quite ready and the Junkers
Junkers
Junkers Flugzeug- und Motorenwerke AG , more commonly Junkers, was a major German aircraft manufacturer. It produced some of the world's most innovative and best-known airplanes over the course of its fifty-plus year history in Dessau, Germany. It was founded there in 1895 by Hugo Junkers,...
Jumo 004 engine was substituted.
Control was achieved with elevons and spoilers
Spoiler (aeronautics)
In aeronautics, a spoiler is a device intended to reduce lift in an aircraft. Spoilers are plates on the top surface of a wing which can be extended upward into the airflow and spoil it. By doing so, the spoiler creates a carefully controlled stall over the portion of the wing behind it, greatly...
. The control system included both long span (inboard) and short span (outboard) spoilers, with the smaller outboard spoilers activated first. This system gave a smoother and more graceful control of yaw than would a single spoiler system.
Testing and evaluation
The first prototype H.IX V1, an unpowered glider, flew on 1 March 1944. Flight results were very favorable, but there was an accident when the pilot attempted to land without first retracting an instrument-carrying pole extending from the aircraft. The design was taken from the Horten brothers and given to Gothaer Waggonfabrik. The Gotha team made some changes: They added a simple ejection seat, dramatically changed the undercarriage to enable a higher gross weight, changed the jet engine inlets, and added a system to carry cold air to cool the jet engine's outer casing, as the wing was made of wood.The H.IX V1 was followed in December 1944 by the Junkers Jumo 004-powered second prototype H.IX V2; the BMW 003 engine was preferred, but unavailable. Göring believed in the design and ordered a production series of 40 aircraft from Gothaer Waggonfabrik with the RLM designation Ho 229, even though it had not yet taken to the air under jet power. The first flight of the H.IX V2 was made in Oranienburg
Oranienburg
Oranienburg is a town in Brandenburg, Germany. It is the capital of the district of Oberhavel.- Geography :Oranienburg is a town located on the banks of the Havel river, 35 km north of the centre of Berlin.- Division of the town :...
on 2 February 1945.
All subsequent test flights
Flight test
Flight test is a branch of aeronautical engineering that develops and gathers data during flight of an aircraft and then analyzes the data to evaluate the flight characteristics of the aircraft and validate its design, including safety aspects...
and development were done by Gothaer Waggonfabrik. By this time, the Horten brothers were working on the Amerika Bomber
Amerika Bomber
The Amerika-Bomber project was an initiative of the Reichsluftfahrtministerium, the Nazi Germany Air Ministry, to obtain a long-range strategic bomber for the Luftwaffe that would be capable of striking the continental United States from Germany, a range of about 5,800 km...
and did not attend the first test flight. The test pilot was Leutnant Erwin Ziller. Two further test flights were made between 2 and 18 February 1945. Another test pilot used in the evaluation was Heinz Scheidhauer.
The H.IX V2 reportedly displayed very good handling qualities, with only moderate lateral instability (a typical deficiency of tailless aircraft). While the second flight was equally successful, the undercarriage was damaged by a heavy landing caused by Ziller deploying the brake parachute too early during his landing approach. There are reports that during one of these test flights, the H.IX V2 undertook a simulated "dog-fight" with a Messerschmitt Me 262
Messerschmitt Me 262
The Messerschmitt Me 262 Schwalbe was the world's first operational jet-powered fighter aircraft. Design work started before World War II began, but engine problems prevented the aircraft from attaining operational status with the Luftwaffe until mid-1944...
, the first operational jet fighter and that the H.IX V2 outperformed the Me 262.
Two weeks later, on 18 February 1945, disaster struck during the third test flight. Ziller took off without any problems to perform a series of flight tests. After about 45 minutes, at an altitude of some 800 m, one of the Jumo 004 turbojet engines developed a problem, caught fire and stopped. Ziller was seen to put the aircraft into a dive and pull up several times in an attempt to re-start the engine and save the precious prototype. Ziller undertook a series of four 360 degree turns with the wings banked 20 degrees. Ziller did not use his radio or eject from the aircraft. He may already have been unconscious as a result of the fumes from the burning engine. The aircraft crashed just outside the boundary of the airfield. Ziller was thrown from the aircraft on impact and died from his injuries two weeks later. The prototype aircraft was completely destroyed.
Despite this setback, the project continued with sustained energy. On 12 March 1945, the Ho 229 was included in the Jäger-Notprogramm (Emergency Fighter Program) for accelerated production of inexpensive "wonder weapons
Wunderwaffe
Wunderwaffe is German for "wonder-weapon" and was a term assigned during World War II by the German propaganda ministry to a few revolutionary "superweapons". Most of these weapons however remained more or less feasible prototypes, or reached the combat theatre too late, and in too insignificant...
". The prototype workshop was moved to the Gothaer Waggonfabrik (Gotha) in Friedrichroda
Friedrichroda
Friedrichroda is a town in the district of Gotha, Thuringia, Germany. It is situated at the north foot of the Thuringian Forest, 21 km by rail southwest of the town of Gotha. It is surrounded by fir-clad hills and possesses numerous handsome villa residences, a Kurhaus and a sanatorium...
. In the same month, work commenced on the third prototype, the Ho 229 V3.
The V3 was larger than previous prototypes, the shape being modified in various areas, and it was meant to be a template for the pre-production series Ho 229 A-0 day fighter
Day fighter
A day fighter is a fighter aircraft equipped only to fight during the day. More specifically, it refers to a multi-purpose aircraft that does not include equipment for fighting at night , although it is sometimes used to refer to some interceptors as well.Examples of planes that were classified as...
s, of which 20 machines had been ordered. V3 was powered by two Jumo 004C engines, and could carry two MK 108 30mm cannon
MK 108 cannon
The MK 108 was a 30 mm caliber autocannon manufactured in Germany during World War II by Rheinmetall-Borsig for use in aircraft.-Development:...
in the wing roots. Work had also started on the two-seat Ho 229 V4 and Ho 229 V5 night-fighter prototypes, the Ho 229 V6 armament test prototype, and the Ho 229 V7 two-seat trainer.
During the final stages of the war, the U.S. military initiated Operation Paperclip
Operation Paperclip
Operation Paperclip was the Office of Strategic Services program used to recruit the scientists of Nazi Germany for employment by the United States in the aftermath of World War II...
, an effort by the various intelligence agencies to capture advanced German weapons research, and keep it out of the hands of advancing Soviet troops. A Horten glider and the Ho 229 V3, which was undergoing final assembly, were secured for sending to in the United States for evaluation. En route, the Ho 229 spent a brief time at RAE Farnborough in the UK while it was considered if British jet engines could be fitted, but the mountings were incompatible.
Northrop Corporation
Northrop Corporation
Northrop Corporation was a leading United States aircraft manufacturer from its formation in 1939 until its merger with Grumman to form Northrop Grumman in 1994. The company is known for its development of the flying wing design, although only a few of these have entered service.-History:Jack...
was chosen because of their experience with flying wings, inspired by the Horten brothers' pre-war record-setting glider. Jack Northrop had been building flying wings since the N-1M
Northrop N-1M
|-See also:-References:NotesCitationsBibliography* Coleman, Ted. Jack Northrop and the Flying Wing: The Real Story Behind the Stealth Bomber. New York: Paragon House, 1988. ISBN 1-55778-079-X....
in 1939.
Survivors
A Horten H.IV flying wing glider is in the Planes of FamePlanes of Fame
Planes of Fame Air Museum is an aviation museum located in Chino, California, and Valle, Arizona. The museum has many flying and static aircraft, along with multiple rare examples under restoration.-History:...
museum in Chino, California
Chino, California
Chino is a city in San Bernardino County, California, United States. It is located in the western end of the Riverside-San Bernardino Area and it is easily accessible via the Chino Valley and Pomona freeways....
. The only surviving Ho 229 airframe, the V3, is at the Smithsonian National Air and Space Museum
National Air and Space Museum
The National Air and Space Museum of the Smithsonian Institution holds the largest collection of historic aircraft and spacecraft in the world. It was established in 1976. Located in Washington, D.C., United States, it is a center for research into the history and science of aviation and...
's Paul E. Garber Restoration Facility in Suitland, Maryland.
Stealth technology
Northrop-built reproduction
After the war, Reimar Horten said he mixed charcoal dust in with the wood glue to absorb electromagnetic wavesElectromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
(radar), which he believed could shield the aircraft from detection by British early warning ground-based radar
Early warning radar
An early warning radar is any radar system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as early as possible before the intruder reaches its target, giving the defences the maximum time in which to operate...
known as Chain Home
Chain Home
Chain Home was the codename for the ring of coastal Early Warning radar stations built by the British before and during the Second World War. The system otherwise known as AMES Type 1 consisted of radar fixed on top of a radio tower mast, called a 'station' to provide long-range detection of...
. A jet-powered flying wing design such as the Horten Ho 229 will have a smaller radar cross-section than conventional contemporary twin-engine aircraft. This is because, with wings blended into the fuselage, there would be no large propeller disks or vertical and horizontal tail surfaces to provide a typical identifiable radar signature.
Engineers of the Northrop-Grumman Corporation had long been interested in the Ho 229, and several of them visited the Smithsonian Museum's facility in Silver Hill, Maryland in the early 1980s to study the V3 airframe. A team of engineers from Northrop-Grumman ran electromagnetic tests on the V3's multilayer wooden center-section nose cones. The cones are three quarters of an inch (19 mm) thick and made up of thin sheets of veneer
Wood veneer
In woodworking, veneer refers to thin slices of wood, usually thinner than 3 mm , that are typically glued onto core panels to produce flat panels such as doors, tops and panels for cabinets, parquet floors and parts of furniture. They are also used in marquetry...
. The team concluded that there was indeed some form of conducting element in the glue, as the radar signal slowed down considerably as it passed through the cone.
In early 2008, Northrop-Grumman paired up television documentary producer Michael Jorgensen, and the National Geographic Channel
National Geographic Channel
National Geographic Channel, also commercially abbreviated and trademarked as Nat Geo, is a subscription television channel that airs non-fiction television programs produced by the National Geographic Society. Like History and the Discovery Channel, the channel features documentaries with factual...
to produce a documentary to determine whether the Ho 229 was, in fact, the world's first true "stealth
Stealth aircraft
Stealth aircraft are aircraft that use stealth technology to avoid detection by employing a combination of features to interfere with radar as well as reduce visibility in the infrared, visual, audio, and radio frequency spectrum. Development of stealth technology likely began in Germany during...
" fighter-bomber. Northrop-Grumman built a full-size reproduction of the V3, incorporating a replica glue mixture in the nose section. After an expenditure of about US$ 250,000 and 2,500 man-hours, Northrop's Ho 229 reproduction was tested at the company's classified radar cross-section (RCS) test range at Tejon, California
Tejon, California
Tejon is a former settlement in Kern County, California. It was located north of Lebec.A post office operated at Tejon during part of 1895, before the service was transferred to Lebec....
, where it was placed on a 15-meter (50 ft) articulating pole and exposed to electromagnetic energy sources from various angles, using the same three frequencies in the 20–50 MHz range used by the Chain Home in the mid-1940s.
RCS testing showed that a hypothetical Ho 229 approaching the English coast from France flying at 885 km/h (550 mph) at 15–30 metres (50–100 ft) above the water would have been visible at a distance of 80% that of a Bf 109
Messerschmitt Bf 109
The Messerschmitt Bf 109, often called Me 109, was a German World War II fighter aircraft designed by Willy Messerschmitt and Robert Lusser during the early to mid 1930s...
. This implies an RCS of only 40% that of a Bf 109, from the front at the Chain Home frequencies. The most visible parts of the aircraft were the jet inlets and the cockpit, but caused no return through smaller dimensions than the CH wavelength. However, the speed of the aircraft, combined with the 20% advantage created by its stealth characteristics, would have made it a serious threat, able to begin an attack before defenses could be brought into play and continuing at a speed too fast for conventional fighter aircraft to nullify.
With testing complete, the reproduction was donated by Northrop-Grumman to the San Diego Air and Space Museum. The television documentary, Hitler's Stealth Fighter (2009), produced by Myth Merchant Films featured the Northrop-Grumman full-scale Ho 229 model as well as CGI
Computer-generated imagery
Computer-generated imagery is the application of the field of computer graphics or, more specifically, 3D computer graphics to special effects in art, video games, films, television programs, commercials, simulators and simulation generally, and printed media...
reconstructions depicting a fictional wartime scenario where Ho 229s were operational in both offensive and defensive roles.
Variants
H.IX V1- First prototype, an unpowered glider, one built and flown (three-view drawing below).
H.IX V2
- First powered prototype, one built and flown with twin Junkers Jumo 004B engines.
Gotha Developments:
Ho 229 V3
- Revised air intakes, engines moved forward to correct longitudinal imbalance. Its nearly completed airframe was captured in production, with two Junkers Jumo 004B jet engines installed in the airframe.
Ho 229 V4
- planned two seat all weather fighter, in construction at FriedrichrodaFriedrichrodaFriedrichroda is a town in the district of Gotha, Thuringia, Germany. It is situated at the north foot of the Thuringian Forest, 21 km by rail southwest of the town of Gotha. It is surrounded by fir-clad hills and possesses numerous handsome villa residences, a Kurhaus and a sanatorium...
, but not much more than the tubular framework completed.
Ho 229 V5
- planned two seat all weather fighter, in construction at Friedrichroda, but not much more than the tubular framework completed.
Ho 229 V6
- Projected definitive single-seat fighter version with different cannon, mock-up in production at IlmenauIlmenauIlmenau is a town located in the district of Ilm-Kreis, Thuringia, Germany.Ilmenau is situated in the valley of the Ilm river, at an altitude of 431 metres above sea level, and is the biggest town in Ilm-Kreis district, with 6,200 students studying at the Technische Universität Ilmenau. The...
.
Horten Developments:
H.IXb (also designated V6 and V7 by the Hortens)
- Projected two-seat trainer or night-fighter; not built.
Ho 229 A-0
- Projected expedited production version based on Ho 229 V6; not built.