Dedicated to all those who served with or supported the 456th Fighter Squadron or 456th Fighter Interceptor Squadron or the UNITED STATES AIR FORCE
The Horten Brothers, Walter and Reimar,
In the 1930's and 1940's in Germany, the Horten Brothers, Walter and Reimar, built a succession of flying wing designs which were quite advanced, and on the cutting edge for their day. Their "Ho" series is as follows:
Ho I - 1931 - a flying-wing sailplane.
Ho II - 1934 - initially a glider, it fitted with a pusher propeller in 1935. Looked very like Northrop's flying wings.
Ho III - 1938 - a metal-frame glider, later fitted with a folding-blade (folded while gliding) propeller for powered flight.
Ho IV - 1941 - a high-aspect-ratio glider (looking very like a modern sailplane, but without a long tail or nose).
Ho V - 1937-42 - first Horten plane designed to be powered, built partially from plastics, and powered by two pusher propellers.
Ho VI "flying parabola" - an extremely-high-aspect-ratio test- only glider. (After the war, the Ho VI was shipped to Northrop for analysis.)
Ho VII - 1945 - considered the most flyable of the powered Ho series by the Horten Brothers, it was built as a flying-wing trainer. (Only one was built and tested, and 18 more were ordered, but the war ended before more than one additional Ho VII could be even partially completed.
Ho VIII - 1945 - a 158-food wingspan, 6-engine plane built as a transport. Never built. However, this design was "reborn" in the 1950's when Reimar Horten built a flying-wing plane for Argentina's Institute Aerotecnico, which flew on December 9, 1960 -- the project was shelved thereafter due to technical problems.
Ho IX - 1944 - the first combat-intended Horten design, it was jet powered (Junkers Jumo 004B's), with metal frame and plywood exterior (due to wartime shortages). First flew in January 1945, but never in combat. When the Allies overran the factory, the almost-completed Ho IX V3 (third in the series - this plane was also known as the "Gotha Go 229") was shipped back to the Air and Space Museum.
[Interestingly, the Horten brothers were helped in their bid for German government support when Northrop patents for the N-1M appeared in US Patent Office's "Official Gazette" on May 13, 1941, and then in the International Aeronautical journal "Interavia" on November 18, 1941.]
If its fuselage, tail, and engine nacelles contribute nothing to an aircraft's lift, why not get rid of them?
Designers pursued the all-wing dream from the first decade of powered flight, notably Jack Northrop in the U.S. and the Horten brothers in Germany. Reimar and Walter Horten were a step ahead, testing an all-wing sailplane in 1933, a twin-engined pusher in 1937, and a turbojet fighter-bomber in 1944. When the war ended, Reimar was working on a six-engine Amerika bomber to carry a hypothetical atomic bomb to New York City.
Postwar, the western Allies dismissed their work, though the British toyed with a transport version of the Amerika Bomber. Walter stayed in Germany and eventually rejoined the Luftwaffe; Reimar went to Argentina and worked for the Peron government. Meanwhile, Jack Northrop was still trying to build a successful all-wing turbojet bomber in the 1950s. That he never hired the Hortens, as German engineers were recruited for the U.S. space program, may been one of history's great missed opportunities.
In the end, all that came from their work was a dozen aircraft whose beauty still astonishes. This is especially true of the Ho 229 fighter-bomber, a batlike warplane that wouldn't look out of place at a 21st-century air show--or combat airfield.
In a speech before representatives of the aircraft industry, Reichsmarshall Göring had announced that no new contracts would be given, unless the proposed aircraft could carry 1000 kg bombs, fly 1000 km/h, and have a penetration depth of 1000 km; penetration depth being defined as the total range.
The Fighter Division requested that the aircraft also be fitted with 30 mm machine guns, something that would lessen the machine’s efficiency as a bomber.
We started drawing and calculating without a contract. Our plan was to build two full size prototypes. The initial penetration depth would only be 800 km, since the fuel proof glue necessary for the full wet wing, was not yet available. On the other hand, the smaller fuel load allowed a doubling of the bomb load, so we went ahead and submitted our proposal.
A contract was awarded with the demand that the first flight be made in six months! Since the jet engine was not yet ready, the first machine would be a glider. The previously deactivated Air Force Command IX was reactivated, and ordered to proceed with the project. Fortunately, the preliminary work that we did without a contract, put us sufficiently ahead, so the six month deadline locked feasible.
There were several reasons for choosing wood as the building material. Duraluminum required more energy to produce; over 3000 KWH, versus less than 3 KWH for wood per ton. The required labor for aluminum production was also much higher; 5000 hr/ton against 200 hr/ton for wood. In addition, aural was difficult to find, and skilled sheet metal workers in short supply. Unskilled workers could easier be trained to work with wood.
Typically, a nose rib was built from a triangular piece of spruce, sandwiched between two plywood sheets, all scrap wood. Production time: 10 minutes. After the glue dried, the rib was simply roused out along a master template in less that 5 minutes. The rest of the wing was built in a similar crude fashion, to pave the way for mass production by unskilled workers.
The main box spar contained all cables and control rods, to free the remaining space in the wing for fuel. That, we planned to pump right into the wing itself, without tanks or bladders. To do this, we needed the fuel-proof glue, that could be used to coat the inside surfaces as well. The glue allowed additional gluing to dissolve and adhere to already coated surfaces, which greatly simplified construction.
The skin was very thick: 17 mm, all plywood; three times the necessary strength. On the production aircraft, this would be replaced by two 1.5 mm plywood sheets, with a 12 mm layer of sawdust, charcoal and glue mix, sandwiched in between. The charcoal in this much lighter skin would diffuse radar beams, and make the aircraft "invisible" on radar (STEALTH Technology -ed).
Finally, should a 20 mm shell explode inside the wing, a relatively harmless hole would result, whereas a metal wing would balloon out and lose its lift.
The H IX wing was designed with 3 geometric and 1.5 aerodynamic twist, to give it the desired bell shaped lift distribution with all controls neutral. The Frise-nose on the elevons had proven to be unsatisfactory, so we decided to use blunt nose elevons instead. The sharply enlarged wing root chord served mainly to eliminate the middle-effect. The maximum thickness line (T-4 line) therefore made a sharp bend in the middle, which resulted in the characteristic pointed tail. As this would affect stability, a test aircraft with large aspect ratio, that had the control surface far outside the test area, was needed. The H Vl would serve this purpose, while other preliminary tests were made with a H II and a H III.
The H IX V-1 took off right on schedule on March 1, 1944 in Göttingen. The small He 45 towplane barely got off the ground, so test pilot Scheidhauer released, and landed straight ahead, after only a short hop. Five days later, he was off again on a snow covered runway behind an infinitely more powerful He 111. He released at 12000 feet, made an uneventful glide back to the airport, then faced problems during landing when the drag chute did not function. As the end of the runway approached, he retracted the nose wheel, and skidded to a stop with only minor damage.
The second aircraft, scheduled to fly three months later, was awaiting its engines, promised in March. Several weeks passed, and then... Disaster!
The engines arrived with an accessory section added to the case, making the cross section oval, and the diameter 20 cm greater! No one had bothered to inform us! Now, just six weeks before the first flight, we were faced with the problem of fitting an 80 cm engine into an aircraft with a 60 cm hole in the spar! It meant that the wing would have to be made thicker.
To maintain the aerodynamic qualities of our design, we would have to increase the span from 16 to 21.3 meters, and the wing area from 42 m2 to 75 m2. Such an aircraft would never reach the targeted performance, even with higher engine thrust. We choose instead to do the best we could with patchwork modifications. The wings remained the same. Another root rib was added 40 cm outside the original, making the center section 0.8 m wider. The new airfoil was 13% thicker than before, and the bend in the T-4 line became much larger. The thicker center section lowered the critical Mach number to 0.75, or a maximum speed of 920 km/in.
The ratio of movement between the control column and the elevons could be reduced to by the pilot for high speed flight. A small high speed drag rudder was supplemented by a larger one that deployed after the smaller was fully extended. Many parts were scrounged from other aircraft left at the test facility in Göttingen. The nose wheel, for instance, came from the tail wheel of a He 177 heavy bomber. We were even able to use the strut and retract cylinder!
The men of Air Force Command IX did their utmost to complete the aircraft before the end of 1944, sometimes working more than 90 hours per week.
I remember that Lt. Erwin Ziller made the first flight about December 18th, 1944, but his log book indicates that the first flight occurred on February 2nd., 1945. I am quite sure the first flight of the H IX was also his first in a jet. Our leaders had little concern for such risks.
Satisfied with the initial flight, the Air ministry ordered 40 aircraft to be built by the Goetha Waggonfabrik under the designation Ho-229.
It appears that the H IX V-2 had flown three or four times before tragedy struck on February 18th. The many versions of the story have a few things in common. The weather was overcast, the ground soft and muddy. The visibility marginal for a test flight, as Lt. Ziller took off, retracted the gear and disappeared. We received a report that one engine had failed, and that the H IX was returning to Oranienburg. Due to the low ceiling, a shallow approach to the airport was initiated. Since the hydraulic pump was on the dead engine, gear and flaps were extended by the emergency compressed air system.
Once down, they could no. be retracted. To maintain his glide slope, Lt. Ziller added power. to overcome the extra drag, and found to his horror that he could "no longer maintain directional control; the fully developed drag rudder unable to overcome the asymmetrical thrust. Rather than lose control, he retarded the throttle to land short of the runway. The aircraft touched down in a field, slid into an embankment and flipped over, crushing its pilot.
The US Third US Army Corps reached the Goetha plant on April 14th 1945. Here they found the H IX V-3 intact and nearly completed, and also the V-4, V-5 and V-6 in various stages of completion. The Ninth US Armored Division found the H IX V-1 in good condition near Leipzig. Its fate is unknown.
The H IX V-3 was later shipped to USA, and is now in the Smithsonian collection, awaiting restoration.
The Horten Ho 229
The Horten Ho 229 (often erroneously called Gotha Go 229 due to the identity of the chosen manufacturer of the aircraft) was a late-World War II flying wing fighter aircraft, designed by the Horten brothers and built by the Gothaer Waggonfabrik. It was a personal favourite of Reichsmarschall Hermann Göring, and was the only plane to be able to meet his performance requirements.
In the 1930s the Horten brothers had become interested in the all-wing design as a method of improving the performance of gliders. The all-wing layout removes any "unneeded" surfaces and –in theory at least– leads to the lowest possible drag. For a glider low drag is very important, with a more conventional layout you have to go to extremes to reduce drag and you will end up with long and more fragile wings. If you can get the same performance with a wing-only configuration, you end up with a similarly performing glider with wings that are shorter and thus sturdier.
Years later, in 1943 Reichsmarschall Göring issued a request for design proposals to produce a bomber that was capable of carrying a 1000 kg load over 1000 km at 1000 km/h; the so called 1000/1000/1000 rule. Conventional German bombers could reach Allied command centers in England, but were suffering devastating losses, as allied fighter planes were faster than the German bombers. At the time there was simply no way to meet these goals; the new Jumo 004B jet engines could give the speed that was required, but swallowed fuel at such a rate that they would never be able to match the range requirement.
The Hortens felt that the low-drag all-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 current private (and jealously guarded) project, the Ho IX, as the basis for the bomber. The Government Air Ministry (Reichsluftfahrtministerium) approved the Horten proposal, but ordered the addition of two 30MM cannon, as they felt the aircraft would also be useful as a fighter due to its estimated top speed being significantly higher than any allied aircraft.
Reichsmarschall Göring believed in the design and ordered the aircraft into production at Gotha as the RLM designation of Ho 229 before it had taken to the air under jet power. Flight testing of the Ho IX/Ho 229 prototypes began in December 1944, and the aircraft proved to be even better than expected. There were a number of minor handling problems but otherwise the performance was outstanding.
Gotha appeared to be somewhat upset about being ordered to build a design from two "unknowns" and made a number of changes to the design, as well as offering up a number of versions for different roles. Several more prototypes, including those for a two-seat "Nacht-Jäger" night fighter, were under construction when the Gotha plant was overrun by the American troops in April of 1945.
The Ho 229 A-0 pre-production aircraft were to be powered by two Junkers Jumo 004B turbojets with 1,962 lbf (8.7 kN) thrust each. The maximum speed was estimated at an excellent 590 mph (950 km/h) at sea level and 607 mph (977 km/h) at 39,370 ft (12,000 m). Maximum ceiling was to be 52,500 ft (16,000 m), although it is unlikely this could be met. Maximum range was estimated at 1180 miles (1,900 km), and the initial climb rate was to be 4330 ft/min (22 m/s). It was to be armed with two 30 mm MK 108 cannon, and could also carry either two 500 kg bombs, or twenty-four R4M rockets.
It was the only design to come close to meeting the 1000/1000/1000 rule, and that would have remained true even for a number of years after the war. But like many of the late war German designs, the production was started far too late for the plane to have any effect. In this case none saw combat.
Horten and B-2
The majority of the Ho-229's skin was a carbon-impregnated plywood, which would absorb radar waves. This, along with its shape, would've made the Ho-229 invisible to the crude radar of the day. So it should be given credit for being the first true "Stealth Fighter". The US military initiated "Operation Paperclip" which was an effort by the U.S. Army in the last weeks of the war to capture as much advanced German weapons research as possible, and also to deny that research to advancing Russian troops. A Horton glider and the Ho-229 number V2 were secured and sent to Northrop Aviation in the United States for evaluation, who much later used a flying wing design for the B-2 "Spirit" stealth bomber. During WWII Northrop had been commissioned to develop a large wing-only long-range bomber (XB-35) based on photographs of the Horton's record-setting glider from the 1930's, but their initial designs suffered controllability issues that were not resolved until after the war. Northrops small one-man prototype (N9M-B) and a Horton wing-only glider are located in the Chino Air Museum in Southern California.
The Ho-229's design employed a thoroughly modern wing shape far ahead of its time. The wing had a twist so that in level flight the wingtips (and thus, the ailerons) were parallel with the ground. The center section was twisted upwards, which deflected air in flight, and provided the majority of its lift. Because of this twist in its shape, If the pilot pulled up too suddenly, the nose would stall (or, lose lift) before the wingtips. This meant that the craft's nose would inherently dip in the beginnings of a stall causing the plane to accelerate downwards, and thus it would naturally avoid a flat spin. A flat spin is difficult to recover from, and many rookie pilots have crashed from this condition. Horten also noticed in wind-tunnel testing that in the beginnings of a stall, most airfoil cross-sections began losing lift on their front and rear edges first. Horten designed an airfoil cross-section that developed most of its lift along the centerline of the wing. Since the center line had high lift and the front and rear edges had low lift, it was called a "Bell-Shaped lift curve". The wings were also swept back at a very modern and optimum angle (his gliders from the 1930's used this sweep long before it became popular) which enhanced its stall-resistance, and also lowered its wind-resistance which helped its top speed. This made the Ho-229 easy to fly and very stall-resistant in all phases of its operation.
The only existing Ho-229 airframe to be preserved was V2, and it is located at the National Air and Space Museum (NASM) in Washington D.C. The airframe V1 crashed during testing, and several partial airframes found on the assembly line were destroyed by U.S. troops to prevent them from being captured by advancing Russian troops.
The Raiders of the Lost Ark
The plane in Raiders looked so unique because it was.
The futuristic Flying Wing was chosen by director Steven Spielberg to represent the
ominous and advanced state of aeronautics in Hitler's Germany.
In the film it is in Egypt for the top secret mission of transporting the sacred Ark of the Covenant.
Production designer Norman Reynolds used a Northrop Corporation prototype of the
Flying Wing (B-36) and drawings by Ron Cobb to design for Raiders of the Lost Ark
this strange plane that has no tail and no fuselage. The plane was built in England by
Vickers Aircraft Company and painted at EMI Elstree Studios in London.
In order to ship the elaborate prop to Tunisia for filming, it had to be
disassembled and sent in parts, then rebuilt on location.
US patent by German Luftfracht-Langguth "tailless airplane" of 1934
While it is a fantasy model, there are a growing amount of people who believe Norman Reynolds got some inspiration from the
Raiders of the Lost Ark was set in 1936...
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.
Year: 1944 Speed: 1200 Km/h; Altitude: 15.000 m
Motors: Heinkel He S 011 A-0
Individual projects were undertaken in various 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 Gotha factory was building the radar-equipped Horten Ho IX, a for that time futuristic jet-engine flying wing. Using the knowledge they gathered from the construction of these now named Gotha Go 229 (the other name used for the Horten Ho IX), they made a proposal for a fighter, the Gotha P60. The P60 used nearly the same wing layout as the Go 229. The first proposal, the P60A, used a cockpit with the crew (2) in a prone position laying side-to-side.
Click on Picture to enlarge
In 1944 the RLM issued a requirement for an aircraft with a range of 11000 km (6835 miles) and a bomb load of 4000 kg (8818lbs). This bomber was to be able to fly from Germany to New York City and back without refuelling. Five of Germany's top aircraft companies had submitted designs, but none of them met the range requirements for this Amerika Bomber. Their proposals were redesigned and resubmitted at the second competition, but nothing had changed. The Hortens were not invited to submit a proposal because it was thought that they were only interested in fighter aircraft..
The Ho XVIII was basically shaped like the Ho VIII, with aerodynamic refinements for a Mach speed of 0.75, 6 jet engines, and was intended to be used as a bomber with 4000 miles operating range, which indicates an intent to bomb America. The idea behind it was probably to carry an atomic bomb to New York or Washington, but luckily for the allies, the bomb was still only theoretical, the engines probably could not have lasted the journey, and the plane could not possibly have been completed before Germany surrendered.
Reimar Horten said in his autobiography:
Our final contract; to develop a six jet long range bomber, was received on March 12, 1945.
To gain some experience with large flying wings, I had proposed to double the size of a Ho III, equip it with six 640 HP pusher engines, give it an endurance of 20 hours at 500 km/h, and the ability to carry a few bombs. Such an aircraft would be useful in the North Atlantic war. The official argument against it was that "our bombers already do 500 km/h!"
The order to proceed with the building of the Ho XVIII came, despite my arguments that preliminary calculations were not completed. Construction was started in Kahla near Weimar in April 1945.
Much too late again. Construction was never finished.
After the Hortens learned of these design failures, they went about designing the XVIIIA Amerika Bomber. During the Christmas 1944 holidays, Reimar and Walter Horten worked on the design specifications for their all-wing bomber. They drew up a rough draft and worked on weight calculations, allowing for fuel, crew, armaments, landing gear and bomb load. Ten variations were eventually worked out, each using a different number of existing turbojets. Several of the designs were to be powered by four or six Heinkel-Hirth He S 011jet engines, and several of the others were designed around eight BMW 003A or eight Junker Jumo 004B turbojets.The Hortens were told to make a presentation for their Amerika Bomber design on Febuary 25, 1945 in Berlin. The meeting was attended by representatives of the five aircraft companies who originally submitted ideas for the competition. No one challenged their assertion that their flying wing bomber could get the job done. A few days later the Hortens were told to report to Reichsmarshall Göring, who wanted to talk to the brothers personally about their proposed Amerika Bomber. There they were told that they were to work with the Junkers company in building the aircraft.
The version that the Hortens thought would work best would utilize six Jumo 004B turbojets, which were buried in the fuselage and exausted over the rear of the aircraft. They were fed by air intakes located in the wing's leading edge. To save weight they thought of using a landing gear that could be jettisoned immediately after takeoff (with the additional help of rocket boosters) and landing on some kind of skid. The Ho XVIII A was to be built mainly of wood and held together with a special carbon based glue. As a result, the huge flying wing should go largely undetected by radar.
Several days later Reimar and Walter Horten met with the Junkers engineers, who had also invited some Messerschmitt engineers. Suddenly it seemed that the Horten's design was to be worked on by committee. The Junkers and Messerschmitt engineers were unwilling to go with the design that the Hortens presented several days earlier. Instead, the committee wanted to place a huge vertical fin and rudder to the rear of the Ho XVIII A. Reimar Horten was angry, as this would add many more man-hours, plus it would create drag and thus reduce the range. The committee also wanted to place the engines beneath the wing, which would create additional drag and reduce the range even further. After two days of discussion, they chose a design that had huge vertical fins, with the cockpit built into the fin's leading edge. Six Jumo 004A jet engines were slung under the wing, three to a nacelle on each side. The bomb bay would be located between the two nacelles, and the tricycle landing gear would also be stored in the same area. The committee would present the final design to the RML and recommended that it be built in the former mining tunnels in the Harz Mountains.
Dissatisfied with the committee designed Ho XVIII A, Reimar Horten redesigned the flying wing Amerika Bomber. The proposed Ho XVIII B had a three man crew which sat upright in a bubble-type canopy near the apex of the wing. There were two fixed main landing gear assemblies with two He S 011 turbojets mounted to each side.
Artwork by Kyle Scott
During flight, the tires would be covered by doors to help cut down on air resistance and drag, a nose wheel being considered not necessary. Overall, the aircraft would have weighed about 35 tons fully loaded. Fuel was to be stored in the wing so that no auxiliary fuel tanks would be required. It was estimated that the Ho XVIII B would have a range of 11000 km (6835 miles), a service ceiling of 16 km (52492 feet) and a round-trip endurance of 27 hours.
Although armament was considered unnecessary, Reimar Horten proposed that two MK 108 30mm cannon could be mounted directly below the cockpit. It was decided that construction was to be done in two bomb-proof hangers near Kala, which had concrete roofs 5.6 meters (18.4 feet) thick. In addition, extra long runways had been constructed so the aircraft could be test flown there too. Work was supposed to start immediately, and the RLM expected the Ho XVIII B to be built by the fall of 1945, which Reimar Horten reported to be impossible. At any rate, Germany surrendered two months later before construction could begin.