Prologue

On June 22nd 2025 seven B-2A bombers carried out strikes in Iran. The total sortie codenamed ‘Operation Midnight Hammer’ lasted 37 hours. They dropped a total of 14 GBU-57 bunker buster bombs on Iran’s Fordow Fuel Enrichment Plant & Natanaz Nuclear Facility . 

The sortie only strengthened the B-2’s formidable reputation of striking distant targets unseen & unheard.. 

The B-2 Spirit is a major milestone in the ongoing evolution of the flying wing.

The Pioneers

Before we get to J W Dunne (considered the father of the flying wing) , we need to first acknowledge a couple of important milestones. The first is Sir George Cayley who in 1799 put forth the concept of a fixed wing ‘machine’, one that had separate systems for creating lift, propulsion & control surfaces. He is the first person to understand the forces that act on a flying machine, weight, lift, drag & thrust. Later in 1810 he worked out the importance of having a dihedral angle at wing roots. The upward angle of wings was “the chief basis of stability in aerial navigation”. It needs to be noted Sir George Cayley was more intent on sharing his knowledge rather than patenting them, and therein lies his greatness.

The second is Alphonse Penaud , best known for his 1871 ‘Planophore’ , a rubberband powered model plane. The design achieved stable flight for 40 seconds demonstrating the stability of fixed wing aircraft designs over any others (such as ornithopters). He teamed up with mechanic Paul Gauchot in 1873 and they patented the monoplane flying wing in 1876. The structure of the ‘flying wing’ had a slight dihedral angle which provided roll stability, they had unswept wingtips and a slight arch on the leading edge with elastic trailing edges, this gave the wing better flexibility when dealing with unstable airflow. The patent contained a detailed performance analysis and is an important milestone as it integrated fixed wings, propulsion & control surfaces into a flyable machine decades before powered flight became a reality.

Between 1906 – 1913 J W Dunne ran his experiments on ‘inherent stability’. From a military background, Dunne collaborated with Col. J E Capper at the British Army’s Balloon Factory to test early designs of his tailless gliders with swept wings. In 1908 his D.1b glider exhibited stable glides after the earlier D.1 crashed unceremoniously. The D.1b ‘s ‘inherent stability’ was achieved through tailless wing design alone.

The D.5 & D.8 were powered tailless biplanes (flying wing configuration) with sweeps up to 30 degrees. The wings featured a washout (a twist reducing the angle of attack at the wingtips) for enhanced stability. The D.5 demonstrated a hands-off flight while Dunne was reading a newspaper). This was a first in the early days of powered flight. The D.10 saw further refinements with a more streamlined design. Dunne’s use of Elevons (combination elevators & ailerons) is considered a first. His designs definitely helped reduce pilot work load. His work would be foreshadowed for the next ten years.

In 1910 the same year Dunne filed his patents, Hugo Junkers too filed a patent for a ‘flying wing or Nurflugel (pure wing). It was for a hollow metal airliner where passengers would sit inside the wing structure (an early blended wing). The fuel and cargo would be in the wings too.  Long-term he envisioned transatlantic flights in such airplanes. His designs had structural integrity due to all metal structures with cantilevered wings and small tails for stability. The G38 was an example of his ideology. He was thrown out of his own company in 1933 as he disagreed with Nazi ideologies.

Between the wars Germany was not allowed to build powered aircraft and this gave rise to a number of glider clubs . Alexander Lippisch worked at Junkers between 1925-27 and this inspired him to take up the ‘nurflugel’ torch. His Storch series of gliders were tailless with swept wings. His Delta series of gliders explored low aspect ratio wings for better roll control. His gliders featured wingtip rudders and elevons. By the early 1930s he had contracted with DFS (Deutsche Forschungsanstalt für Segelflug a.k.a German Institute of Glider Research, a Nazi front) for powered prototypes such as the 1931 DFS 40, a rocket powered tailless plane. Lippisch directly inspired two young brothers who would go on to create one of the most fabled aircraft of all time, enter Reimar & Walter Horten and the aircraft they would create the Ho-229.  

Mentions: The powered Cheyranovskii BICh-3 Tailless research aircraft of 1926 & G T R Hill’s Westland Pterodactyl series of tailless gliders between 1926-32. Hill would go on to design and construct the Westland Dreadnought, the very first purpose built Blended Wing Body.

The sequence of events mentioned above illustrates the evolution of wings over an almost 200 year period starting with Sir George Cayley. The unveiling of the B-2 Spirit in 1988 was 112 years after Alphonse Penaud’s patent of 1876. During the early years of aviation, patents filed in different countries could be viewed or accessed through scientific journals, world fairs & patent translating offices.  Percolation of ideas was slow and the timespan mentioned above makes the point.

The Horten Brothers

Between the wars in Germany several ‘civil clubs’ sprung up where students trained on gliders under the supervision of WW1 veterans. By the mid-late 1920s, the young brothers, heavily influenced by Alexander Lippisch began experimenting with tailless gliders. Their recollections in later life mention they turned their bedroom, attic & basement at home into a workshop, cluttering their family home in Bonn with airplane models. The home based experimentation was important to their later productions. Their gliders were simple tailless constructions with a cocoon for a pilot integrated into the design. The models focussed on keeping parasitic drag (all objects experience drag through the air) down and had better performance than conventional designs.

By 1931 the brothers had moved their activities to Bonn-Hangelar Field, a gliding club where they had access to mentoring, tools & materials from more experienced aviators. Their first full scale glider was the Horten H-I from 1931 and had a 40 foot wingspan, it was constructed of wood and fabric. The design integrated swept wings & elevons.

By the mid 1930s (1933-1937) the Hortens were further refining their designs at Wassekrupp, Germany’s Mecca of gliding. They too had support from the DFS and constructed their subsequent designs (Horten H-II – H-IV).

Each model kept growing in size. The H-II had a 52 foot wingspan while the H-III & H-IV each had a 80 foot wingspan. The materials used got better with funding from DFS, for example they began using plywood i.s.o fabric. The internal structure moved from wood on the initial models to steel and aluminum in later ones. 

H-III was a motorized version which had a 32hp VW engine driving a foldable propeller. Model H-IV was a high performance pure glider.

The models exhibited a bell shaped lift distribution curve across the wing. It is higher near the wing root and tapers off near the wingtips with a smooth non linear profile. This sort of lift balances efficiency & stability and is essential for gliders with no engine to compensate for inefficiencies. The non-linear curve is important as the bell has a flatter peak and falls off at the tips, meaning optimal lift is maintained for longer. 

The gliders achieved this with swept wings of up to 30 degrees, the wingtips had washout built into them and had variable chord, meaning they tapered toward the wingtips from the wing roots. An example of this lift efficiency is when the H-III achieved flights as long as 300 km. 

Reimar Horten’s focus on lift distribution gave their designs a glide ratio of 30:1 i.e they could glide thirty times their height in distance. The focus on lift distribution is also one of the possibilities of the Ho-229’s ‘ stealth properties’ which we speak of later. Ludwig Prandtl was the scientist credited with presenting the concept of spanwise lift distribution in 1919 , Reimar Horten adapted Prandtl’s insights fifteen years later.

The H-V (1937-1943) was an exception to the materials the Horten brothers used for their gliders. They used experimental plastics. The H-V is considered the very first composite materials aircraft, however the first prototype crashed on its very first flight and Hortens reverted to wood as their material of choice. The H-V had a 46 foot wingspan and was powered by two 79 hp Hirth HM 60 R engines from the mid 1920s, powering pusher propellers. Specs gleaned from wikipedia showed the H-Vb(the second of three built) had a cruise speed of 230 km/h and a landing speed of 70 km/h.

It is just about here we observe the iterative design approach the Hortens took. They alternated each glider model with a motorized version, the H-III had a motor as did the H-V, H-VII & H-IX.

The H-VI (1944) reverted back to pure glider form after the learnings from the H-V and had significant design improvements such as a very high aspect ratio of 32.4 and a 80 foot wingspan. The wings had a sweep back of 20 degrees. The refined control surfaces were drawn from H-V data. The model had extensive stall behavior examination using tuft tests done on it. A tuft test is where strings of yarn (tufts) are attached to the entire wing surface and the aircraft is tested either in a wind tunnel (or in the Hortens case in flight). Attached airflow shows the tufts align smoothly with the laminar airflow. Separated flow is when the tufts begin to flutter erratically. Using this test is important to identify stall onset, control effectiveness, drag data & tip stall mitigation.

The H-VII(1944) was once again the H-V under a new guise. It was powered by two 240 hp Argus AS 10C engines. The V8s powered propellers once again in pusher configuration. The pilot seating was side by side vs the H-Vs semi prone position. Key increments included better control surfaces (elevons, spoilers & drag rudders) and in general a more robust internal structure for longer operations.The H-VII had a cruise speed of 300 km/h and service ceiling of over 21,000 feet. (source wikipedia).

The H-VIII(1945) was an upscaled version of the H-VII. It was sold incomplete to the RLM (ReichsLuftahrtMinisterium a.k.a Ministry of Aviation). It had a 131 foot wingspan and was powered by six pusher propeller engines. Each Argus 10 engine developed 236 hp. It represented a clear step in the direction of military applications and was expected to have a 1000 km bombing radius. The incomplete aircraft was destroyed by the Allies.

The H-IX v3 or the Ho-229 was the aircraft that is responsible for the Horten legend. When the allies got to the Gotha factory they found an aircraft unlike any other they had seen. It had bat-like wings and jets for engines (largely unknown then). The H-IX was a direct evolution of the H-V & H-VII designs. It was powered by two Junkers Jumo 004 turbojet engines buried inside the wings. Each of the engines generated 1990 lbs of thrust. The H-IX had a 55 foot wing span and the wings had a 32 degree sweep. It could fly at 977 kmph and had a service ceiling of 49,000 feet. This aircraft was beyond anything the Allies had to offer in terms of speed and agility. 

The tailless wing at such speeds did throw up control related challenges, and in the era before fly by wire computers the aircraft had as many as eight control surfaces for the pilot to manage. The aircraft had a total of four elevons (two per wing), two drag rudders (one per wing) to induce yaw, and two speed brakes to control dives (also known as dive rudders). The v3  was the third in the series after the v1 & v2 and is the only surviving example of the H-IX/Ho-229.

Jack Northrop

Northrop began his aviation journey as a young man in 1916 with the Loughead Aircraft Manufacturing Company. As a mechanical draftsman & engineer, during his first stint there (1916-17) he worked on multiple aspects of the F-1 flying boat. Importantly his work focussed on light weight and high strength structures which would further fuel his focus on efficiency.

By 1917 he was drafted into the US Army where he served as an infantryman, however he quickly transferred to the Signal Corps to analyse Curtiss flying boats. In 1918 Loughead secured his return from the army where he continued his aviation career co-designing the Loughead S-1 a small sports plane that used moulded plywood construction and was known for its  drag reducing streamlined fuselage.

Between 1926-28 after stints with Douglas Aircraft,  Jack Northrop rejoined Loughead Aircraft (soon to be Lockheed) as chief engineer and designed the Lockheed Vega made famous by Amelia Earhart and her 1932 Transatlantic solo flight. The Vega was known for its low drag coefficient of 0.02. His work on the Vega further refined his expertise and focus on lightweight aerodynamic airframes, contributing to his future work on flying wings.

In 1928 Jack Northrop founded the Avion Corporation focussed on developing all metal aircraft with tailless designs and by 1929 he built the Avion Experimental No 1 (Northrop Flying Wing a.k.a X-216H). While it was a flying wing, Northrop retained a twin tail boom, this was for added safety during testing (wings were still being understood). The wing was made of aluminium and was of stressed skin multi cellular construction. Such constructions distribute loads across the entire wing while reducing weight and maintaining structural integrity. The wing demonstrated low Cd of 0.015 but suffered from pitch and yaw instability. Aircraft company consolidation meant that Avion Corporation was acquired by William Boeing as part of UATC (United Aircraft Transport Corporation) and was renamed Northrop Aircraft. At the time Jack Northrop designed the Alpha, a conventional low wing monoplane mail carrier.

Around 1931 the depression played a major role with Jack Northrop and UATC merged Northrop Aircraft with Stearman in Wichita, Jack Northrop refused to relocate and quit. In 1932 with the backing of Donald Douglas, Jack Northrop founded the new Northrop Corporation as a Douglas subsidiary. He developed the Beta, a faster variant of the Alpha and Gamma between (1932-34). The Gamma was a 700 hp mail & research plane. The most famous was the ‘Polar Star” that was transported via ship to Antarctica. This was followed by the Delta which was intended for passengers, however regulations prohibiting single engined aircraft from carrying passengers at night or over rough terrain curtailed this aircraft. Technically it was a success.

Further to these aircraft Northrop’s multicellular wing design greatly influenced the legendary DC-3. By 1937 Douglas was acquired once again and Northrop who yearned freedom to chase his wing designs quit once again and founded the Northrop Aircraft Inc in Hawthorne California.

The N-1M(1940-41) made its first flight in 1940 as Northrop’s first flying wing. It had a 38 foot wingspan and two 65hp Lycoming O-145 pusher prop engines. The skin was laminated wood around a tubular steel frame. It had an adjustable wingtip with a 15 & 30 degree vertical sweep. Its glide ratio was 15:1 and it proved tailless flight stability.

In 1941 the USAF was looking for a new bomber and authorized Northrop to develop the YB-35 flying wing bomber. As a first step Northrop developed the N-9M(1942-45) a one third scale flying wing with a wingspan of 60 feet and two 400 hp O-540 engines. The aircraft had automatic trim, split flaps & drag rudders which were an improvement over the N-1Ms manual controls. The first airframe crashed in 1943 killing the pilot, the reason being pitch control failure, which prompted redundancies to be built into later aircraft. The aircraft had a cruising speed of 320 km/h and a service ceiling of over 21,000 feet with a glide ratio of 18:1. The numbers validated full scale construction of the XB/YB-35.

With a wingspan of 172 feet and four contra rotating pusher props the X/YB-35 was a majestic sight. The aircraft used four Pratt & Whitney R-4360 radial engines. The contra rotating gear boxes caused excessive vibrations leading to mechanical failure and stress. The engines & propellers were owned by AAF ( United States Army Air Force) . None in the supply chain had checked the engines for compatibility with the Hamilton Standard propellers, furthermore nobody took responsibility for the shortcomings either. The XB-35 flew a total of 27 flights between the two aircraft and only one flight was deemed satisfactory. Of the 14 YB-35s built only one was completed and that flew a total of seven flights for a total of less than ten hours. The YB-35 continued to be plagued by the same engine problems that plagued the XB-35. Reverting the engines to single propellers resulted in the aircraft being underpowered resulting in low speed handling issues. 

Jack Northrop grew frustrated with the engines and attempted corrections, however he had severe limitations as the engines and propellers were owned by the AAF. In the meantime the AAF had turned its attention to jets and ordered two of the YB-35s converted to the jet engined YB-49. By 1948 the troubled YB-35 was terminated, never reaching fruition for reasons beyond its control.

The YB-49 had eight Allison J-35-A-15 turbojet engines, each developing 4000 pounds of thrust.The aircraft immediately hit 40,000 feet and cruised at 587 km/h (wikipedia), however with eight engines instead of four the range effectively dropped to half the YB-35. While the specifications were the same, the YB-49 did have four small passive vertical fins on the wings to help with yaw control. The two wings completed approx 25 flights between them, however both crashed in 1948 & 1950 the first killing all its crew including Captain Glen Edwards after whom Edwards AFB is named. 

One more YB-35 was converted to a YB-49A reconnaissance aircraft (with podded engines) however this was never completed either.

Jack Northrop’s dream project was abruptly cancelled in 1950. Northrop himself was deeply anguished to see his dream cancelled and retired in 1952. In 1979 Northrop mentioned the Flying Wing contracts were cancelled because he refused to merge with Convair. Hindsight shows the flying wing program was way behind execution deadlines and over budget, hindsight also shows there was always a place for the flying wing. Alas that was not to be and all the wings were scrapped and none exist today.

The Story of WW2 Stealth Myth vs Reality

The Indiana Jones style discovery of the Ho-229 v3 deep in the German countryside inside a dark deserted hangar created the myth. The fact it looked like no other plane before and was referred to as the batwing only added to the myth, the jet engines solidified it.

The aerodynamic properties of flying wings naturally make them stealthy. The glide ratios of all the powered wings (including the YB-35 & 49) had ratios in the range of 20-28:1 . This compares favorably with the B-2 which has a similar ratio. Physics dictates that all flying wings will look similar and flying wings through the decades attest to this.

The wings were built for speed, their aerodynamics being the enabler. This meant the speed of the Ho-229 was over 75% faster than convention fighters of the time.

The controversial 2009 Nat Geo documentary with Northrop Grumman where a representative replica was made and subjected to RCS tests, showed a 20% decrease in the RCS (Radar Cross Section) properties over conventional aircraft of the time. This combined with the speed of the Ho-229 / H-IX v3 is what would have made the aircraft difficult to counter. Point to note in the documentary was the Northrop Grumman team had difficulty replicating the complex aerodynamic surfaces of the original wing.

A step back from the Horten story tells you this was incomplete. The incomplete H-VIII which was delivered to the Ministry of Aviation highlights the state Germany was in and the increased pace of aircraft iterations (1943-45) along with the H-XVIII Amerika Bomber being just plans on paper point to the incomplete story (much like Northrop’s).

Reimar Horten’s 1983 claim in the book ‘ Nurflugel” about planning for the v3’s successors to be stealthy by mixing carbon in the binding elements & painting the aircraft with graphite sounds opportunistic in view that no hard evidence or documentation was ever found. The Ho-229 did not exhibit any carbon in its adhesives conclusively. The timing of the claim ties in well with the announcement of the B-2 Stealth bomber, and Reimar who for all his achievements was fading into insignificance perhaps wanted to make the best of the reflected glory and renewed interest in the Ho-229. This is the reality.

History finds stories like the Ho-229 irresistible, and there lies the fable.

The B-2 Spirit

By the 1970s military designers were chasing the concept of Stealth. Low RCS is achieved by a cross section of materials, aerodynamic design, electronics & of course masking engine thermal signatures & sound.

By 1979 Northrop’s Tacit Blue program had already proved that stealth was possible and the technology was incorporated in the B-2.

During the 1981 presidential race Ronald Reagan repeatedly dug into Jimmy Carter and his cancellation of the B-1A bomber. In response to this Carter on August 22nd 1980 disclosed the Department of Defence was working on the B-2.

While the development was a black program, the B-2 was less closely guarded than the Lockheed F-117 stealth fighter. The unveiling of the B-2 in 1988 was highly restricted. At least two Northrop employees went to prison for espionage during and after its development.

That the wingspan of the B-2 is 172 feet, the same as the YB-35/49 is perhaps a happy co-incidence, however its capabilities are entirely intentional. Its cruise speed is 1010 km/h, range is 11,000 km, and service ceiling of 50,000 feet the numbers are very similar to the Ho-229/YB-49 (except range).

The control issues all the flying wings faced dissipated as computers took over the pilot’s work load and made continuous split second corrections for stable flight.

A very old Jack Northrop was shown a model of the B-2 a few months before his passing in 1981 and he poignantly commented “ I now know why God kept me alive for the last 25 years”.

The B-21 Raider had its first flight in Nov ’23. While it is smaller than the B-2 , it remains just as exciting. 

Epilogue

In the centre of the Udvar- Hazy hall at Smithsonian sits the H-IX / Ho-229 v3. Everyday hundreds of spectators file past its still figure as if paying homage. The aircraft that launched a thousand dreams continues to do so.

In the skies above it flies the B-2 Spirit protecting a grateful Nation. Thousands of people watch each spectacular fly past. 

Flying wings are pure magic.

Please be sure to read part 2 where the evolution of blended wing bodies is traced in detail. http://theaviationevangelist.com/2025/09/19/the-flying-wing-part-two-the-blended-wing-body/

To be continued….Part Two

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