Ho 229
1944 Blue Print of Nazi Stealth aircraft H.IX V1
Role	Fighter/ Bomber
Manufacturer	Gothaer Waggonfabrik, Munich, Germany
Designed by	Horten Brothers. Munich, Germany
First Flight	1 March 1944
Aircraft built	3 (Three only)

Today when we see a photo of US Air Force’s Northtop B2 stealth bomber, we ponder how advance US warfare technology is. But the fact may differ. B2’s stealth design and technology is a virtual copy of 1944 original invention of Hitler’s Aeronautical Engineers Reimar and Walter Horten .

History is witness that German stealth aircraft “Horten H.IX”, (also known as Ho 229 and Gotha Go 229), was a World War II prototype fighter/bomber and built by Gothaer Waggonfabrik of Frankfurt. It was the first pure flying wing, powered by two jet engine and designed to be hard to be detected by radars. This was the first aircraft to incorporate what is now known as “stealth technology”. A personal favorite of Luftwaffe chief Reichsmarschall Hermann Göring. This was the only aircraft to come close to meeting his 100% requirements of performance. Its flew at 1,024 km/h (636 mph) at a ceiling of 15,000 meters (49,213 ft).

Stealth Technology Design and Development

In the early 1930s, as a method of improving performance of German gliders, Horten brothers had become interested in the flying wing design.

The flying wing design removed all unneeded surfaces which lead to the lowest possible drag. “A wing-only” configuration allowed for a similarly performing glider with wings that were shorter and thus sturdier, without additional drag of the fuselage.

In 1943, Reichsmarschall Goring 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".

Reichsmarschall (Marshal of the Empire or Imperial Marshal) was the highest rank in the armed forces of Germany during World War II after the position of Supreme Commander, which was held by Adolf Hitler.

Conventional German bombers could reach Allied command centers in Great Britain, but were suffering devastating losses from Allied fighters. At that time, there was no way to meet these goals — the new Junkers Jumo 004B turbojets could provide the required speed, but fuel consumption was high.

The Hortens concluded that the low-drag flying 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 private project, the H.IX, as the basis for the bomber. The German Air Ministry approved Horten’s 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 aircraft was a mixed construction. The center pods were made from welded steel tubing and wing spars built from wood. The wings were made from two thin, carbon-impregnated plywood panels glued together with a charcoal and sawdust mixture. The wing had a single main spar, penetrated by two jet engine inlets. The wing's chord/thickness ratio ranged from 15% at the root to 8% at the wingtips.

Control was achieved with ailerons and spoilers. Directional stability at low speeds especially while coming in for landing, was achieved by undercarriage covers, which has control surfaces in the trailing edge and could be operated only at the time of landing after the undercarriages were lowered and locked.

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 firm control of yaw than would a single spoiler system.

The aircraft utilized retractable tricycle landing gear. A drag parachute slowed the aircraft upon landing. The pilot sat on a primitive ejection seat. Engines offered thrust lower than expectation and pilots were never satisfied with them.

Testing and evaluation

The first prototype H.IX V1, an unpowered aircraft 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 seats, added a failsafe device that would not open the undercarriage if the projected probe was extended. They changed the undercarriage to enable a higher pay load, changed the jet engine inlet design for lower noise in dive, and as the wing was made of wood, they added a system to rush fresh air to cool the jet engine's outer casing.

In December 1944, this stealth H.IX V1 was followed by second prototype H.IX V2, for which, the BMW 003 engine was fitted. Goring believed in the design and ordered a production series of 40 aircraft from Gothaer Waggonfabrik. The first flight of the H.IX V2 was made in Oranienburg on 2 February 1945.

By this time, the Horten brothers were working on the Amerika Bomber.

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. There are reports that during one of these test flights, the H.IX V2 undertook a simulated "dog-fight" with a Messerschmitt Me 262, 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.^[4]

Unloading of captured Horten Ho 229 V3 in the USA

Despite this setback, the project continued with sustained energy. On 12 March 1945, the Ho 229 was included in the Jäger-Notprogramm for accelerated production of inexpensive "wonder weapons". The prototype workshop was moved to the Gothaer Waggonfabrik (Gotha) in Friedrichroda. 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 fighters, of which 20 machines had been ordered. V3 was powered by two Jumo 004C engines, and could carry two MK 108 30mm cannon 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, 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 and sent to Northrop Corporation in the United States for evaluation. Northrop 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 in 1939.

Survivors

A Horten H.IV flying wing glider is in the Planes of Fame museum in Chino, California. The only surviving Ho 229 airframe, the V3, is at the Smithsonian National Air and Space Museum's Paul E. Garber Restoration Facility in Suitland, Maryland.

Stealth technology

Northrop-built reproduction

After the war, Reimar Horten disclosed that he mixed charcoal dust in with the wood glue to absorb electromagnetic (radar) waves, which he believed could shield the aircraft from detection by British early warning ground-based radar known as Chain Home. 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. Horten's theories were tested by Northrop-Grumman in 2008 through the building of a replica that was found to give a radar cross section only 40% that of conventional aircraft.^[2][4]

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, Marylandin 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-fourths of an inch (19 mm) thick and made up of thin sheets of veneer. 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.^[2]

In early 2008, Northrop-Grumman paired up television documentary producer Michael Jorgensen, and the National Geographic Channel to produce a documentary to determine whether the Ho 229 was, in fact, the world's first true "stealth" 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, 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 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 meters (50–100 ft) above the water would have been visible at a distance of 80% that of a Bf 109. 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.

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 reconstructions depicting a fictional wartime scenario where Ho 229s were operational in both offensive and defensive roles.

Variants

A captured German Horten Ho 229 V3 prototype at the Smithsonian National Air and Space Museum's Garber restoration facility. Placement of engines closest to the cockpit reduced torque on failure of one of the engines and during engine failures, the aircraft performed satisfactorily well.

Rear view of Horten Ho 229 prototype H.IX V1

Ho 229 V3’s revised design also revised air intakes. Engines were placed a bit 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: Two seat all weather fighter, in construction at Friedrichroda, 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 Ilmenau.

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.

Specifications (Horten Ho 229A (V3))

From manufacturer's estimates-three view drawing at top of page shows the Ho IX V1 glider prototype.

Data from The Great Book of Fighters

General characteristics

§ Crew: 1

§ Length: 7.47 m (24 ft 6 in)

§ Wingspan: 16.76 m (55 ft 0 in)

§ Height: 2.81 m (9 ft 2 in)

§ Wing area: 50.20 m² (540.35 ft²)

§ Empty weight: 4,600 kg (10,141 lb)

§ Loaded weight: 6,912 kg (15,238 lb)

§ Max takeoff weight: 8,100 kg (17,857 lb)

§ Powerplant: 2× Junkers Jumo 004B turbojet, 8.7 kN (1,956 lbf) each

Performance

§ Maximum speed: Mach 0.92, 977 km/h (607 mph) at 12,000 m (39,370 ft)

§ Combat radius: 1,000 km (620 mi)

§ Ferry range: 1,900 km (1,180 mi)

§ Service ceiling: 16,000 m (52,000 ft)

§ Rate of climb: 22 m/s (4,330 ft/min)

§ Wing loading: 137.7 kg/m² (28.2 lb/ft²)

§ Thrust/weight: 0.26

Armament

§ Guns: 2 × 30 mm MK 108 cannon

§ Rockets: R4M rockets

§ Bombs: 2 × 500 kg (1,100 lb) bombs

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V S Saxena
Mumbai