Junkers

Junkers Flugzeug- und Motorenwerke AG (JFM, earlier JCO or JKO in World War I, English: Junkers Aircraft and Motor Works) more commonly Junkers , was a major German aircraft and aircraft engine 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, initially manufacturing boilers and radiators. During World War I, and following the war, the company became famous for its pioneering all-metal aircraft. During World War II the company produced some of the most successful Luftwaffe planes, as well as piston and jet aircraft engines, albeit in the absence of its founder, who had been removed by the Nazis in 1934.
History.
World War I.
The history of Junkers aircraft production begins with the Junkers J 1 mid-wing monoplane (not to be confused with the later, all-metal sesquiplane ground attack aircraft with the "IdFlieg" designation J.I which had a factory designation of J 4). Research for this aircraft began in 1914 and was interrupted by the start of the First World War. The prototype aircraft, named the "Blechesel" (Tin or Sheet-metal Donkey), was completed in very late 1915 after the outbreak of the war. This aircraft is significant in that it was the first flyable aircraft to utilize an all-metal "total structural" design. Contemporary aircraft were built around wooden frames constructed in a rib-and-stringer fashion, reinforced with wires, and covered with a stretched fabric. The J 1 was a semi-monocoque design, using steel ribs and sheeting that formed both the stringers and the skin. At the time aluminium was still fairly expensive; and the desirable 1906 invention of German metallurgist Alfred Wilm, that of duralumin alloy, could not be worked in sheet form without damaging flaking occurring, so the J 1 was made of sheet electrical steel. It was quite heavy as a result, which translated into poor climb and maneuverability, yet its clean monoplane layout, which even featured a "belly" radiator installation for its Mercedes D.II inline-six cylinder engine, had very low drag, and the J 1 was one of the fastest aircraft of its day, reaching speeds of 170 km/h, with only a 120 hp engine for power.
Following the J 1, a series of "J-designated" (by the Junkers firm itself) aircraft followed, each advancing the state of the art in terms of strength and weight, but no single design progressed much beyond the prototype stage in terms of production potential. The Junkers J 2 was an extensively "cleaned up" and armed single-seat fighter descendent of the J 1, while the J 3, a never-completed single rotary engined mid-wing monoplane design that only consisted of covered wing panels and a nearly complete fuselage frame, replaced the smooth exterior electrical steel sheeting with corrugated duralumin. "IdFlieg", in charge of aircraft evaluation, was unconvinced of the monoplane layout of these designs, and ordered a sesquiplane design as the J 4. Junkers took this opportunity to produce all the flying surfaces (wings and horizontal stabilizer) of the J 4 aircraft of corrugated duralumin (except for some fabric on the rear fuselage, and the armored steel fuselage "bathtub") in order to lower weight. The J 4 became Junkers' first design to enter production, with orders totalling 283, of which about 184 were delivered to operational units. Since it was the first design from Junkers to serve in the Luftstreitkräfte's ""J"-class" of armored, infantry co-operation aircraft, which also had the Albatros J.I and AEG J.I serving with it in the same capacity, the curious and confusing instance of the Junkers J 4 armored all-metal sesquiplane getting the German military designation "J.I" was one caused solely by the Luftstreitkräfte's choice of designation letter for "all" of its armored, ground forces co-operation aircraft.
Junkers continued to believe in the monoplane layout constructed entirely in metal, and continued the J-series with a number of newer monoplane designs. One of the most successful was the all-duralumin J 7 technology demonstrator aircraft prototype, which went through five major and minor changes in its airframe design during tests throughout 1917 and which was later stretched to form the two-seat J 8. The J 8 was the first cantilever monoplane design, and looked extremely "modern" when compared to contemporary wire-braced biplane designs. The J 8 was put into limited production by the Junkers-Fokker Werke (a collaborative firm founded through strong influence of the German government on October 20, 1917) as the J 10, receiving the "IdFlieg" designation of CL.I, a small number of which saw service on the Eastern Front just before the war ended. Likewise, the single-seat J 7 itself led to the J 9 design, built in small numbers as the Junkers D.I low wing fighter by both the Junkers firm itself (abbreviated "Jco" or "Jko") and the Junkers-Fokker-Werke AG (abbreviated "Jfa") — with the resulting three-letter abbreviation of either firm usually marked on the J-9's landing gear wheel covers.
The corrugated duralumin wing and fuselage "skin" introduced in the J-series became a trademark of Junkers aircraft built in the 1920s and '30s. Development continued during the course of World War I, including a growing (but troublesome) partnership with Fokker, as the "Junkers-Fokker Aktiengesellschaft". Several Junkers designs were licensed to Fokker during this period. The visual similarity of Junkers and Fokker aircraft during the next decade, especially after Reinhold Platz adapted some of the Junkers design concepts, but mostly crafted in wood for the Fokker designs' wing structures instead of the all-metal Junkers construction techniques, is attributable to this early affiliation. The Great War ended with German Navy trials of the model J 11, which was an all-metal floatplane prototype.
Early inter-war period.
In the immediate post-war era, Junkers used their J8 layout as the basis for the F-13, first flown on 25 June 1919 and certified airworthy in July of the same year. This four passenger monoplane was the world's first all-metal airliner. Of note, in addition to significant European sales, some twenty-five of these airplanes were delivered to North American customers under the Junkers-Larsen affiliate and were used primarily as airmail planes.
The Treaty of Versailles signed only days after the F-13 flew, initially forbade any aircraft construction in Germany for several months. After that span of time only the design of civilian aircraft was permitted to Germany. With a partial relocation of the Junkers firm to the Fili western suburb of Moscow, the Junkers firm was able to restart its aircraft manufacturing concern within the borders of the Soviet Union in 1922, the partly revitalized Junkers firm developed a series of progressively larger civil aircraft including the single-engined G.24 and three-engined G.31. Neither aircraft was a commercial success. With the expiration of treaty restrictions in 1926, Junkers introduced the Junkers W33 and Junkers W34 series which did find significant commercial success via large production orders in passenger, freight hauling, and, somewhat later, military configurations. The W-33/W-34 series also set multiple aviation "firsts" including records for flight duration, flight distance, altitude, rocket assisted take-off and inflight refueling between 1926 and 1930.
Junkers' produced a design study in 1924 for a visit to the United States. The study outlined a four-engined 80-passenger plane, incorporating a forward canard wing, as well as a main wing, both of which were fitted above twin pylons. Called the Junkers J.1000 Super Duck passenger seating was to be provided both in the main wing and the hull sections of the craft. This Junkers design, including a scale model, was intended to illustrate an aircraft capable of trans-Atlantic operations of 8 to 10 hours and was completely revolutionary for its day.
It was in 1922 that American engineer William Bushnell Stout, and in 1924 that Soviet engineer Andrei Tupolev each adapted the Junkers corrugated duralumin airframe design technologies for their own initial examples of all-metal aircraft in their respective nations – for Stout, the Stout ST twin-engined naval torpedo bomber prototype aircraft, and for Tupolev, the Tupolev ANT-2 small passenger aircraft, who had the assistance of the Soviet government's TsAGI research center in achieving success with light-weight metal airframes.
The basic principles outlined in this design were later introduced in the Junkers G.38, which was introduced and put into regular service by Deutsche Luft Hansa. At the time of its introduction, this four-engined transport was the largest landplane in the world carrying thirty-four passengers and seven crew members. The G.38 sat some of its passengers in the wing area outboard of the fuselage, the front of which was covered with windows.
Also, in 1932, Junkers joint project with Maybach designed and built an aerodynamic car but found due to the depression that the market for high end luxury cars was saturated.
Financial troubles.
Around 1931 the company suffered from a series of financial difficulties that led to the collapse of the group of companies. The existing shareholders pressured Hugo to leave the company. Hugo, however, was the patent holder on a wide variety of the technologies used in most of the existing Junkers designs, including many of their engines.
A plan was started to solve both problems by "buying out" Hugo's engine patent portfolio and placing it into the hands of a new company, the Junkers Motoren-Patentstelle GmbH, which was eventually formed in November 1932. The new company would then license the technologies back to the various companies, most notably what was then Junkers Motorenbau (one of many "Jumo" companies). However, before Junkers actually transferred his patents to the Patentstelle, the collapse of the Junkers consortium was solved by the sale of the Junkers Thermo Technik GmbH to Robert Bosch, whose company still uses the brand name. Adolf Dethmann, a Communist activist and friend of Hugo, was appointed managing director.
Nazi takeover.
The Nazi party came to power in Germany in 1933, and all German aviation development was shifted away from long-range civil aircraft types. Hugo Junkers himself was forced to transfer all his patents to the Nazis, who doubted that Junkers (a socialist and pacifist) would comply with their plans. Shortly after, his holdings were expropriated and he was placed under house arrest. The company that had pioneered commercial aviation development for at least a decade was relegated to relatively small one- and two-engined military design competitions issued by the "Reichsluftfahrtministerium" (RLM) the "Reich Aviation Ministry". Two exceptions to this were the Ju 52 and the Ju 90.
Ju 52 development had started in 1928 as a single-engined commercial transport and evolved, initially to a two-engined, later into the classic "trimotor" design for which the "Tante Ju" became world-famous. The Ju 52 was a bona fide commercial success, with over 400 airplanes delivered to various airlines around the world prior to the outbreak of World War II, including the countries of: Finland, Sweden, Argentina, Brazil, Uruguay, Ecuador, Peru, Mexico, South Africa, Denmark, Norway, Italy, UK, Belgium, Hungary, Estonia, Greece, Spain, and of course, Germany. As a consequence of its rugged design, Spain and France resumed Ju 52 production after cessation of the Second World War.
With the introduction of the Junkers Ju 86 bomber of 1934, Junkers abandoned the corrugated sheeting of his earlier designs. The basic layout was used in the four-engine Junkers Ju 89 heavy bomber, but this program ended with the death of Walther Wever, and his Ural bomber program along with him. Junkers then adapted the Ju 89 to passenger use, introducing the Junkers Ju 90, one of the first planes specifically designed for scheduled trans-Atlantic flights to the US. Developed in 1937, the aircraft suffered multiple setbacks with crashes of prototypes in 1937 and 1938. Further refinements enabled certification in 1939 and spurred South African Airways to make an initial order for two aircraft fitted with US-built Pratt & Whitney engines. Just as the aircraft was being readied for its first commercial flights, World War II began. With the outbreak of hostilities, all models were requisitioned by the Luftwaffe for military air-transport roles, and later, long-range maritime patrol.
World War II.
Military aircraft production was begun by the company in the 1930s and eventually monopolized all its resources. Perhaps the most notable design was the Junkers Ju 87 "Stuka" dive bomber, one of the Luftwaffe's most effective aerial weapons in the early-war period and continually used for bombing attacks as an integral part of the Blitzkrieg strategy. The Stuka was used both for precision tactical bombing and the strafing of enemy positions, acting as a sort of "airborne artillery" that was able to keep up with the fast-moving tanks and attack defended points long before traditional artillery could be brought into range. Later in the war it was fitted with two large-calibre, "Bordkanone 3,7" 37mm underwing autocannon and employed in a "tank busting" role against Soviet armour. It gained notoriety for its use at both Dunkirk and later Stalingrad, where it caused enormous destruction under Field Marshal Wolfram von Richthofen's VIII Air Corps.
Perhaps even more successful was the Junkers Ju 88, the primary medium bomber of the German forces. It was used in practically every role imaginable; level bomber, shallow-angle dive bomber, night fighter, and bomber destroyer, as well as in anti-shipping raids. A variety of improved versions were also produced over the course of the war, including the Ju 188 and Ju 388 which included numerous features for better performance, but never replaced the Ju 88 outright. A much more formidable aircraft was also planned, the Junkers Ju 288 for the "Bomber B" design competition, which it handily won — but the required high-power engines never worked properly in tests, and as the design was also plagued with insufficiently strong main landing gear, the effort was eventually abandoned.
The Ju 52 was a transport aircraft, roughly equivalent to the Allies' DC-3 Dakota, that was also modified to carry out bombing raids. A total of 4,845 Ju 52 were produced before and during World War II, leading to widespread use delivering men and supplies in support of the German war effort. The Ju 52 had previously seen service in the Spanish Civil War, where it took part in the Condor Legion's destructive raids on Durango and Guernica in 1937 which illustrated to the world—for the first time—the destructive potential and horror of strategic bombing. Unfortunately for its pilots and military passengers, by the outbreak of World War II, the Ju 52 was a thoroughly obsolete military design and unlike many other famous Luftwaffe aircraft, the "Tante Ju" was cumbersome, slow, and therefore vulnerable to attack. This resulted in many losses, namely at Crete and Stalingrad.
The abortive "Amerika Bomber" design competition for a trans-Atlantic range strategic bomber saw the Junkers firm build two prototypes of its six-engined Junkers Ju 390, basically a stretch of the four-engined Ju 290 transport — competing against the trio of Me 264 four-engined prototypes as the only fully airworthy competitors for the contract, which had included designs from Focke-Wulf and Heinkel that were never built, with the competition ended in July 1944 due to the developing need for interceptors to defend the Reich.
Post World War II.
The Junkers company survived the Second World War and the formation of East Germany, and was reconstituted as Junkers GmbH and eventually merged into the MBB consortium (via joint venture Flugzeug-Union-Süd between Heinkel and Messerschmitt in 1958). Messerschmitt ended the joint venture in 1965 by acquiring control of JFM AG and absorbing it within Messerschmitt in 1967. Within West Germany, Junkers GmbH was engaged in research on the future of aerospace transportation during the fifties and early-1960s. During this period, Junkers employed the famous Austrian engineer and space travel theorist, Eugen Sänger, who in 1961 completed work for the design of an advanced orbital spacecraft at Junkers. Junkers GmbH was absorbed within MBB and the Junkers name disappeared in 1969.
Junkers Jumo.
Junkers also ran an engine factory, and in 1923 they separated it from the parent to form its own company, Junkers Motorenwerke, or Jumo. This company expanded greatly in the 1920s and 30s, with factories spread across Germany. Jumo was the first company to produce a successful aircraft diesel engine in material numbers, the opposed-piston layout two stroke Jumo 205, and it was the first German company to offer a truly modern engine suitable for aviation in the form of the 650 hp, inverted-V12 Jumo 210. But, with the rapid advances in airframes, after a few years this engine was considered to be underpowered, causing Jumo to respond with the much larger Jumo 211, the most-produced German aviation engine of any type during the war years. Perhaps unsurprisingly, the 211 saw widespread use in Junkers bombers — most often in a "unitized" form for the Junkers Ju 88A, and also in the competing Heinkel He 111H medium bomber — but was little used otherwise, due largely to the better power output of the competing Daimler-Benz DB 601. Further development of the 211 led to the superb Jumo 213, which was in high demand for an increasingly large variety of late-war piston-engined aircraft. Their only attempt at an over-1,500 kW output piston engine, the Junkers Jumo 222, suffered from inadequate metallurgy and internal design for what was otherwise a very innovative engine design, with nearly 300 examples produced solely as test examples — the aviation engine firms of the Third Reich had considerable challenges in developing piston engines that could exceed the 1,500 kW output level that would be able to operate with proven combat reliability. However, the world's first production axial-flow compressor-equipped turbojet engine, emerged from the "Jumo" firm in 1944 as the Jumo 004, becoming the first turbojet engine to be considered of production quality, and was used in the then revolutionary Messerschmitt Me 262A jet fighter.
Products.
Aircraft.
The Junkers firm's early aircraft were identified by the letter J for Junkers followed by an Arabic type number. From 1919 they introduced an additional sales designation using the same number but prefixed by a letter indicating the role of the aircraft:
Just once, the same number was used to identify two different completed types. This pair was the T 23 and G23, both also known as J 23.
During World War I, machines in service used the regular Idflieg aircraft designation system to specify their design's purpose, also promoted by the Flugzeugmeisterei (Air Ministry), again a letter number system indicating role:
The best known and most confusing example is the Junkers J 4 armored-fuselage, all-metal sesquiplane, known to the military as the Junkers J.I.
The single letter company prefix was not replaced by the twin-letter Ju prefix until 1933. This RLM system – from the Third Reich's air ministry – applied to all German manufacturers; the first Junkers aircraft to receive a Ju number was the W 33, so retrospectively it became the Ju 33. However, earlier aircraft built in Moscow like the H 21 were often described by a Ju number, e.g. Ju 21.
Aircraft engines.
All Junkers diesel engines were two stroke, opposed piston designs, an arrangement he invented in the early 1890s. It was intended to provide an alternative to Nicholaus Otto's patented four stroke which would run on low grade fuels such as blast furnace waste gases. By 1896 Junkers engines were generating electrical power in steelworks.