Prototypes Of Flying Wing Aircraft Design example essay topic

1 When questions are asked about the flying wing, there are those that undoubtedly mention the B 2 Spirit "Stealth Bomber". Most tend to emphasize the great cost and complexity of these aircraft rather than its elemental design. Those of an earlier generation may mention aircraft built by Northrop in the nineteen fifties. These aircraft were considered radically ahead of their time. They started with reciprocating engines turning propellers and eventually evolved into pure jet aircraft. This introduced a new problem inherent with the pure flying wings of the times (before fly-by-wire) and that was a lack of stability.

Unfortunately, many records and working prototypes of flying wing aircraft design were lost in the World War II attacks on Germany which slowed progress. Pilots were unable to make the corrections necessary to keep these aircraft aloft in any actual combat maneuvering. The jets did away with the naturally stabilizing affect of the propellers and engineers quickly learned that stabilizing fins and large wing "fences" were required. Not only were the issues of stability a major source of friction between Northrop and unbridled success, but the very idea of an airplane with no discernable fuselage to wing junction was radical indeed.

Engineering and design techniques slowly being written in stone had to be thrown out the window for these aircraft - these flying wings... When the smoke cleared, all of the hard work had (so they thought at the time) been for naught. The flying wings were passed over in favor of more conventional designs regardless of the potential the flying wing (s) had shown. As it turned out, John Knudsen Northrop's dream of the pure flying wing has been realized in full color potential. Enter the B 2 Spirit - its computer-aided flight controls, with the addition of 2 every available benefit of modern technology to date has proven the lethality and grace at which an air war can be fought.

No huge penalty of parasite drag exists in the wing-to-fuselage junction, leading to inconceivable efficiency. The wing is no longer used to support the "important" parts of the aircraft - it is the aircraft. Stealth technology has, to this date, been completely realized through the tailless "boomerang" silhouette of the flying wing. The recent war in the gulf and its highly sensationalized "Shock and Awe" campaign was led by the B 2. But a question remains...

Where, when, and by whom was the flying wing first conceived and tested with largely promising results which led to Northrop's quest and eventual success with this design? Dr. Reimar Horten died of heart failure at his home in Argentina (emigrated from Germany in 1948) early in 1993. He was unaware of the medal that he had been awarded. The British Gold Medal of Outstanding Achievement in Aeronautics arrived two days later.

Toward the end of the Second World War, Hitler had pinned his hopes on a glorious final victory. This was to be achieved through his "wonder weapons". The pulse jet V 1 and the first ballistic missile, the V 2. (Dabrowski 1995) Considering the condition of the Nazi hierarchy toward the end of the war, I find it amazing the Horton brothers were able to design and test several different designs of the pure flying wing. It should be mentioned; the Hortens were designing and testing flying wing aircraft before the war had even begun and continued to do so throughout the conflict. Their resources 3 were limited - drawn by the production of main-line fighters like the Fokker Wulf 190 and Messerschmitt BF-109, as well as more highly supported (relative to Horten projects) ventures into jet aircraft and their engines and design.

Of note and later discussion is the Horten H IX V 2. This was the world's first jet powered flying wing. (Dabrowski 1995) It managed to make several flights after February 1945 - before the end of the war. Far ahead of its time, the H IX V 2 was to be designated Ho (Horten) 229 and was slated to be built in large quantities as a main-line fighter. (Ginger 2000) It is also of great interest that every German aircraft maker had a flying wing or at least a tailless design on the drawing board at the end of the war.

This is definitely a credit to the brothers Horten and their designing genius. It was the early nineteen-thirties... In the town of Bonn, Reimar, Walter, and Wolfram Horten busied themselves with model building from an early age. Aware of its possible benefits, Reimar and Walter soon turned to the all-wing construction. At this point it should be stated that the Horten Brothers did not invent the flying wing or tailless aircraft. Their convincing designs and successful tests did however; attract considerable attention to the type.

As mentioned earlier, flying wing aircraft have some considerable advantages relative to a conventional tailed aircraft. All control functions; all useful load; as well as power plants are accommodated inside a correspondingly thick wing. (Dabrowski 1995) Advantages known, certain aviation pioneers were investigating and working on all-wing designs: John William Dunne (England), Hugo Junkers (Germany), Alexander 4 Soldenhoff (Switzerland), Boris Cheranovski (U.S.S.R. ), and John Northrop of the United States. Surprisingly enough; these pioneers did not collaborate or contact one another. All had hopes and dreams of tailless aircraft. [Throughout the 1930's] "The German people must become aviators", declared the State Minister of Aviation, Hermann Goring.

(Dabrowski 1995) This statement was made during peacetime between World Wars I and II. One must wonder if an ulterior motive was involved even at this time. Sport flying was very much promoted in Germany throughout the thirties and those successful fighter pilots from the first war had lived on during peace time to become famous aerobatic aces and eventual film stars of the period. Flying displays were highly attended - air races, altitude and range record attempts were promoted as national events. Enter the outbreak of World War II... Reimar Horten joined the gliders in Konigsberg and continued his design work on the flying wing.

Walter was trained as a bomber pilot and eventually made his way into fighter planes, scoring seven kills during the Battle of Britain. Wolfram was also a pilot but lost his life in the skies above France. Inspiration for the Horton designs came in the form of tailless aircraft by Alexander Lippisch (1894-1976). Lippisch designs were not pure flying wings in that they relied on small vertical stabilizers and wing fences. Over the course of time, hundreds of sleek, swept wing aircraft sprang from his drawing boards. About a third of these designs were actually realized through production by various people.

5 Following successful testing in 1933 and '34, Reimar and Walter finally received approval for their first manned all flying wing - the H 1. The H 1 was only a glider with a wingspan of approximately thirty-six feet. In honor of their inspiration, the brothers nicknamed it "D-Hangwind" (Up slope Wind) after professor Lippisch's nickname. D- Hangwind won the brothers Horten a prize of six-hundred Reich marks in a design competition in 1934. As for the fate of the H 1 - it was given to Alexander and unfortunately, no one was able to procure a ferry aircraft to tow the large glider off the mountain. After only seven hours in the air, the H 1 was broken up and burned at its site of glory.

(Vandenberg 1997) Perhaps the most famous (or infamous depending on point of view) design of the vaunted professor Alexander Lippisch was the rocket-propelled, Messerschmitt-built, Me 163. This fearsome machine was the first airplane to exceed one-thousand kilometers per hour in level flight. The brave soles piloting the Me 163 would take off and pierce bomber formations, certainly causing some consternation among the slow, lumbering Liberator and Flying Fortress crews. These attacks were more psychological than anything else, as they caused minimal damage due in no small part to their exhaustion of fuel after climbing to intercept. 1935: The first powered aircraft by the Horten brothers was the H IIm, "D-Habicht" or Hawk. It was designed as a motorized glider from the outset - this avoided the troublesome towed takeoffs.

The Hawk was a very lightweight machine with a two-wheeled single-track undercarriage that tended to make the airplane unstable during 6 ground operations. (Dabrowski 1995) In order to stay true to the all wing design, the pilot would lay in a prone position while looking forward through a glazed, transparent leading edge section of the wing. This design element allowed for a very sleek aircraft but the material (called Mip olan) which began its service as a transparent sheet would soon become opaque. However; the availability of a new material called Astral on soon solved this problem as it was donated by another German company.

The engine was a used but overhauled HM 60. It provided the Hawk with surprising performance considering its meager sixty horsepower. The Hawk could climb to one-thousand meters in two and a half minutes and reach one-hundred eighty kilometers per hour in level flight. This engine allowed the brothers to prove the capabilities of their designs and increased their own publicity as well. Soon enough, the engine was replaced by an updated version of the HM 60 designated as the R-spec. With eighty horsepower this made the Hawk quite a performance oriented machine.

Satisfied with the added performance, the Hortens also modified the wingtips; giving the pilot the ability to change wing dihedral in flight! The eventual fate of the H II is unknown. Successor to the H II was the H d. It was now 1942. For all intents and purposes, it was simply a larger version of the H II.

It had a wingspan of just over twenty meters and was driven by a Walter Mikron engine. Like its predecessor the aircraft proved to be nearly idiot proof and the only complaints came from the lack of power and unreliability from the fifty-five horsepower Mikron. The H d is a milestone for the Horten bothers in that it was demonstrated to the professor of the Aerodynamics 7 Research Institute, Ludwig Prandtl. His glowing report to the RLM ensured the Hortens would be able to continue their research into the increasingly difficult war years. As a direct result of the disappointing performance of the Mikron engine, the brothers soon replaced it with an air-cooled Volkswagen engine and re-designated the aircraft H d. Test flights began in January of 1944, with the moveable wingtip idea having been tried the previous year it was scrapped due to "technical difficulties".

As with its sibling, the H's fate is unknown. H Va. Built entirely of synthetic materials and powered by twin H 60 R-spec engines (Dabrowski 1995) it was a veritable showcase for the Dynamit company that had assisted the Hortens in previous ventures - notably, supplying the improved transparent wing sections that provided the pilots with outward visibility. The H Va provided the Dynamit company with a rolling test bed for their revolutionary materials and eventually led to patents for solutions on material bonding, uniform thickness, and rigidity etc. Crewed by two pilots (Reimar and Walter) the H Va was not the success hoped for. Its first flight proved to be its last; for the twin counter-rotating engines mounted far back in the fuselage (in hopes of eliminating the long driveshaft of mid-mounted engines) proved to be too heavy and caused enough rearward moment as to make the airplane unstable at low airspeeds and (relatively) high angles of attack as in takeoff.

Also to blame was the variable-geometry flight control system which utilized counter-rotating wingtips. The Horten brothers went back the drawing boards after getting approval from the RLM and began construction of a second twin-engine flying wing designated H Vb. This 8 aircraft was much more conventional by direct comparison; utilizing construction of wood and steel tube as opposed to the synthetic materials which had yet to be perfected. Also, the variable flight controls were scrapped in favor of the standard arrangement of control surfaces.

The pilot no longer lay in the prone position and sat upright, thereby ending any lay-down Horton flying wings. These H Vb's were used as fighter pilot trainers in modest numbers but proved very effective in this role. Throughout the war years, access to material had become increasingly difficult and many Horton designs were left in various states of completion. It is with great admiration that the Horten brothers were able to design and test jet variations of their pure wing designs. Previously mentioned in this paper was the H IX V 2, which was to be designated H 229.

The impetus for design of the H IX came in 1943. Walter Horten had obtained performance curves of the then new, Junkers Jumo 004. These performance measures were developed from the awesome Messerschmitt 262, the first operational jet fighter. From this point, work ceased on the most recent creation of the brothers' (H VII) and all effort was focused on their new hot rod. The first steps in the development process of the H IX were the requirements laid down by Reichmarschall Hermann Goring (Dabrowski 1995).

This called for an aircraft capable of carrying a 1,000 kilogram bomb-load to a target 1,000 kilometers away at a speed of... 1000 kilometers per hour. It was hence named: Project 1000 X 1000 X 1000. So rigid were these guidelines, that no aircraft that failed to meet these minimum 9 expectations would be accepted.

The ending result of this project was the first flying wing ever to take to the air. This was no easy feat however. In August of 1943, orders for decentralization in the development ranks severely hindered development and testing of the H IX. Previously located in one area, workers were transported in all directions throughout Germany.

To make matters worse, the team responsible for the H IX was inexplicably disbanded from an officer up in the ranks and possibly connected to a competing aircraft manufacturer. With the support of Goring, the team reformed itself and continued under a veil of secrecy. Operating independently of the Generalfeldmarschal's orders while still receiving funding would be looked upon as highly illegal and counter-productive to the "glory" of the Reich. The H IX was made in the conventional sense, (by Horten standards anyway) using steel tube and wood for the aircraft frame. Most of the skin was of wood as well, except for the areas near the engines which were of tempered sheet metal. Pre-production models were tested sans engines in February of 1944 (remarkably on - schedule!) and proved to be very stable flying machines.

Soon enough, actual tests began on an H IX variant built to use the BMW 003 turbojet engine. Unfortunately, delays in receiving the 003 resulted in the Hortens having to use the Jumo 004. The 004 was more powerful but it was also a larger engine, thus extensive modifications had to be made on the aircraft - enough to quantify a full redesign. 10 The engines were not the only delays in the project...

Most mechanical parts were sourced from other production airplanes. For example: the retractable nose wheel was actually a tail wheel retrieved from a wrecked He (He inkle) 117 bomber. The retractable main gear supports were removed from a BF 109. In early February 1945, the H IX was finally ready for trial runs.

Test Pilot Erwin Ziller was a capable pilot with whom the Hortens had worked previously and met with great success. He did not however, have much experience in jet aircraft - a cumulative five hours in an Me 262 was the extent of his turbojet time. His first flight in the aircraft was uneventful. The second flight resulted in a collapsed nose gear from his premature release of the braking chute upon landing. Later that same month all tests of the H IX V 2 ended... Ziller was in the midst of his third flight in the Horten aircraft when onlookers spied him deviating from the flight plan and conducting high altitude rapid descents (to approximately 800 meters) in apparent attempt to restart a flamed-out starboard engine.

It should be stated here that the mechanic who conducted the preflight run-up of the Jumo 004's did not agree with continuing the flight testing, due to random flame-out, until a suitable replacement engine could be found. None were available then, and probably not for a long time after. One the fourth and final attempt, the H IX was seen to descend lower than previously and abruptly lowered its landing gear and, subsequently, its high drag gear doors. Onlookers heard a loud turbine "noise" as the aircraft entered an increasingly steep spiral. Lieutenant Erwin Ziller did not eject nor did he survive. 11 Investigation after the crash led to several conclusions ranging from hydraulic failure, which explained an empty pressurized air canister for lowering the landing gear, to an aggravated stall induced by the increased drag and high bank angle.

Questions were raised about Ziller's actions in the airplane. Did he lose consciousness from carbonized oil in the cockpit? Why did he not eject? Was he trying to save the aircraft? Was sabotage involved? Answers led to more questions with the H IX V 2.

It had been proven in un powered flight time and time again. It was not time for the V 2. It was the last Flying wing to be completed by the Horten brothers before the allied invasion forced a retreat and the leaving behind of the second turbojet-powered flying wing ever created - the H IX V 3. Would more progress have been made given more time and resources? Definitely. Walter and Reimar Horten paved the way for the future of the flying wing.

Various examples of their machines are in states of restoration in museums in the United States Others were tested and examined to determine their actual effectiveness. To date; of all plans and designs of the Horten brothers, whether fantasized or realized, none have been as advanced as the H IX V 3. No doubt Northrop and others have learned many lessons from these fantastic airplanes. We " ve seen what proper funding can do to virtually any project.

Bibliography

Hurst, Ronald A. (1982) Pilot error: the human factors.
London, Great Britain: Granada Publishing Company. Oster, Clinton V. (1992) Why airplanes crash.
New York, NY: Oxford University Press. Owen, David. (1998) Air accident investigation.
Great Britain: J.H. Haynes & Co. Ltd. Wire, Christopher. (1998) Unmanned aircraft of the millennium.