|Trip page||This page contains excerpts from several sources found on the internet. It is gathered as background information for a write-up of a trip we made to Dessau.|
The history of the Junkers Flugzeugwerke
Hugo Junkers was born on February 3rd, 1859 in a small town named Rheydt near Monchengladbach in Germany as the third out of seven sons of Louise and Heinrich Junkers. Hugo Junkers grow up at Rheydt and went to junior high school there from 1867 to 1874. He continued his school education at the vocational school at Barmen between 1875 and 1878.
In 1878 Junkers started his engineering studies at the university of Berlin. In 1881 he moved to Aachen and continued his studies at the Rheinisch-Westfalische Hochschule Aachen. Hugo Junkers graduated in 1883 at the age of 24 from the Institute of Technology Aachen as "Governmental Mechanical-engineering Supervisor".
Hugo Junkers as student, 1878
On the suggestion of Adolf Slaby, who was his professor in Berlin, Wilhelm von Oechelhaeuser called him to Dessau in 1888 and charged him with the development of a large high-performance gas engine.
In 1890, they founded jointly the "Gas-engine Test Station Von Oechelhaeuser and Junkers" ("Versuchsstation für Gasmotoren Von Oechelhaeuser and Junkers"), where, after two years of intensive work, in 1892 a new two-stroke opposed-cylinder engine was developed, which may be considered the great-grandfather of the later Junkers heavy-oil and flight-diesel engines. For his first gas engine Junkers had already to solve some difficult problems. Under his supervision, a reliable ignition system was developed.
After a short period of cooperation with Von Oechelhaeuser, Hugo Junkers founded, in 1892, his first company under the name "Hugo Junkers Civil-Engineer" in Dessau. There, he started to exploit his patent for the "calorimeter", a measurement device to determine the caloric contents of gases.
Hugo Junkers, a brief overview
Hugo Junkers (3 February 1859 - 3 February 1935) was a German engineer and aircraft designer. As such he is generally credited with pioneering the design of all-metal airplanes and flying wings.
As founder of the Junkers Flugzeug- und Motorenwerke AG he was one of the mainstays of the German aircraft industry in the years between world war I and world war II. In particular his multi-engine all-metal passenger- and freight planes helped establish airlines in Germany as well as all over the world.
Although his name is also linked to some of the most fearsome German warplanes of the second world war, Hugo Junkers himself had nothing to do with their development. He was forced out of his own company by the Nazi government in 1934 and died in 1935.
Next to aircraft, Junkers also built both Diesel and petrol engines and held various patents on thermodynamic and metallurgic subjects.
Amongst the highlight of his career were the Junkers J 1 of 1915, (the first aircraft to use an all-metal skin, cantilever wing design and minimal external bracing), the Junkers F-13 of 1919 (the world's first all-metal passenger plane), the Junkers W-33 (who made the first successful east-to-west crossing of the Atlantic ocean), the Junkers G-38 'flying wing' and the Junkers Ju 52, affectionately nicknamed 'Tante Ju', one of the most famous airliners of the 1930's.
One of the first commercial products was, besides the calorimeter, the gas geyser, which was derived from the calorimeter. This device was since 1895 industrially produced by the new company "Junkers & Co., Ico", followed by many other products related to "gas-thermo-technology". The profits of this successful operating enterprise provided the economic foundation for Hugo Junkers' test and research institutions where he could conduct his pioneering and fundamental research free of financial constraints.
The instant success Junkers and his partners had in the area of aircraft engineering is certainly based on the wealth of experience gathered within decades in the field of applied research, especially in fluid mechanics and material sciences as well as in the area of manufacturing technology.
His career as a university lecturer began in September 1896 with his appointment as professor of thermodynamics and as head of the "Mechanical-engineering Laboratory" at the Institute of Technology Aachen. Only some weeks later, he founded in Aachen the "Research Institute Professor Junkers, Aachen" ("Versuchsanstalt Prof. Junkers, Aachen") and further institutions followed within the next years.
So Junkers consequently operated, apart from his enterprise Ico in Dessau and his teaching activities in Aachen, his own private test organisations. Essentially funded by the profits of Ico, he was able to work independently on his self-posed scientific and technical problems.
It is not exactly identifiable at what time Hugo Junkers became interested in aeronautical technology. Certain is, that he already gathered literature about topics related to airship aviation during his university studies. In 1885, he wrote down the following questions concerning aeronautical technology:
- Under what conditions of "Mechanics" can a body be kept floating in the air?
- What kind of shape needs a body to develop at a certain velocity a lifting force?
- What are suitable propulsion systems for such an airship?
Astonishing are, in discussing these questions, Junkers' thoughts concerning propulsion, which he wants to realize by "sucking in or ejecting air": "One could propel an airship forward by the reaction (force) due to an outpouring body (gas etc)". He thinks about a machine "working with high pressure and compressing a gas at low pressure".
These ideas are still utopian at the time when his first theoretical and practical tests commenced, but they show how far the creative thinking of Hugo Junkers was ahead of its time. Also many years later, he was occupied with questions of unconventional propulsion means far away from the propeller principle common at that time.
Hugo Junkers' first practical activities in aeronautics were inspired by Hans Reissner, who in 1906 had been appointed professor of technical mechanics at the Institute of Technology Aachen.
Since then, he conducted experiments with a Voisin-biplane, for which he could raise Junkers' interest. They had a lively exchange of thoughts and it became obvious that Junkers intensively thought about improvements.
Hans Jacobus Reissner
On January 15, 1908 he wrote to Reissner, among other things, about "one's own comprehensive tests with corresponding wing geometries" which one should conducts. Reissner now decided to design his own aircraft, which should, as advised by Junkers, be equipped with corrugated metal wings.
The production of the aluminium surfaces caused problems since none of the metal-processing companies addressed saw fit to comber previously corrugated sheet metal, i.e., to realize a cambered wing shape.
This difficult manufacturing task was finally solved at Ico. Junkers' firm built the flying surfaces of Reissner's design, and also built its radiator. The "Reissner Duck" was tested in 1912 and for Junkers this meant the first step into manufacturing sheet metal in aircraft engineering.
The Reissner Ente (Duck)
In 1911, Junkers was appointed head of the Institute of Aerodynamics at the Technical University of Aachen. Due to his application, a small wind tunnel was built which Junkers used for systematic measurements.
Initially, he tested models with equal drag and found that large, aerodynamically shaped bodies produced as much drag as plates, spheres or rods with considerably smaller cross sections.
Bodies to study air-flows
Since Junkers was not satisfied with the possibilities of this small wind tunnel, he built his own wind tunnel at the Versuchsanstalt Prof. Junkers, Aachen (Research Institute Professor Junkers, Aachen). From these studies, the idea of a "thick wing" was born.
Probably during the development of the Reissner Ente Hugo Junkers also started to think about initial Aircraft Engine Designs within the Versuchsanstalt Prof. Junkers, Aachen. In 1913 Junkers acquired the Magdeburger Werkzeugmaschinenfabrik (Magdeburg Machine Tool Works) and founded the Junkers Motoren GmbH (Junkers Motor Works) in Magdeburg, which built large diesel engines for the propulsion of ships. In December 1913 the Versuchsanstalt Prof. Junkers, Aachen ordered the M27 at Jumo Magdeburg for experimental design tests of a future aircraft engine.
The M27 was the starting point of Junkers aircraft engine developments. The construction work on that engine was also stopped with the breakout of World War I. The Magdeburg production was ceased and the Junkers Motoren GmbH was dissolved. The remains at Magdeburg were sent to Aachen, where oil engine research and constructions were continued at the Versuchsanstalt Prof. Junkers, Aachen.
World War I
With the outbreak of World War I Hugo Junkers moved back from Aachen to Dessau where he founded the Forschungsanstalt Prof. Junkers, which continued the Junkers research work at Dessau.
During these early war years, the Junkers studies were mainly focused on the design of all-metal aircraft constructions and the development of oil engines.
The history of Junkers aircraft production begins with the Junkers J-1 mid-wing monoplane. In May 1915 Junkers' researches had progressed far enough for him to invite a delegation of Miligary officials to visit the Junkers' facility in Dessau and witness the progress that had been achieved.
J-1 before its first flight on 12 December 1915 in Dessau
To his disappointment, Junkers found the military sceptical of his designs. An aircraft made from metal, created in a company that "made kitchen utensils", was regarded with suspicion.
In spite of this, Junkers managed to obtain a contract for a test machine, the Junkers J-1. It was decided the aircraft should be built from steel (tubing) and thin sheet iron, materials tat Junkers was intimately familiar with.
The prototype aircraft, named the Blechesel (Tin Donkey), was ready for its first flight test on 12 December 1915. 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. Following static load tests and engine thrust tests, the completed J-1 was taken to the Fliegerersatzabteilung 1 airfield in Döberitz just west of Berlin for its flight tests, that were done in December 1915 and January 1916.
The Junkers J-1 was probably not flown again after January 1916. However, it survived World War I and was placed on display in a Berlin aviation museum. It met its end during one of the bombing raids on Berlin during World War II.
Junkers was not only concerned with the airfoil shape in his tests but also with the optimum wing aspect ratio. Initially, he experimented with small aspect rations since he wanted to combine a small-span wing with favourable lift and drag values.
Wind tunnel Aachen
Junkers started his measurements not on airfoils, but on a sphere followed by increasingly more slender ellipsoids of the same cross section.
That way he proved that the cross section does not have a large influence and
that thick cross sections are not only permissible but, within certain limits, are even better than thin cross sections (that is without considering the advantages due to the omission of the wing braces).
Junkers was not only concerned with the airfoil shape in his tests but also with the optimum wing aspect ratio. Initially, he experimented with small aspect rations since he wanted to combine a small-span wing with favourable lift and drag values.
Only through his measurements, he recognized the advantage of large aspect rations.
The next step in his tests concerned the determination of the best camber of the airfoil skeleton (centre) line.
Without knowledge of Lilienthal's experiments, he reached the fundamental conclusion:
It was shown that the degree of camber of this line was extraordinarily important for the amount of lift generated.
It is an important result of my investigations that not so much the individual form of the pressure or suction side of the wing is important but the shape of the skeleton (centre) line.
Junkers did not find the most favourable drag on the thinnest airfoil, as was generally assumed at that time, but on airfoils with average thickness ratios of 1:5 - 1:10. It was found that, at equal camber of the centreline, more favourable drag values were also found for airfoils with a convex lower surface. Systematically measured were, in addition, the aerodynamic moment and the movement of the centre of pressure locations. Here, too, was the thicker wing superior to the thinner one.
The problem of structural height was, at that time, fairly well solved by the biplane, where the upper and lower surfaces were joined by struts and braces to a very rigid airframe.
This is, however, negatively compensated by aerodynamic disadvantages.
Junkers wanted to investigate experimentally, and without prejudice, the question whether biplanes or monoplanes were the best solution.
After extensive biplane measurements he came to the conclusion
that the interference between the two finds of the biplane is aerodynamically always an unfavourable one regardless of the arrangement of the wings.
Junkers summarized these findings in four points as follows:
- The aspect ratio should be as large as possible.
- The camber of the centreline is controlling the aerodynamic properties of a wing.
- A think airfoil, including the generally avoided convex lower side, may also provide good results.
- The multi-wing plane is inferior to the monoplane.
Following the J-1, a series of J-designated 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.
The Inspectorate of Flying Troops, in charge of aircraft evaluation, was unconvinced of the monoplane layout of these designs, and ordered a sesquiplane design as the J-4.
Junkers J-2, 1916
Junkers J-4 / J-I
The J-4 was desired as a low-flying armoured anti-infantry aircraft, from which hand grenades and small handheld bombs would be thrown off over frontline positions and ditches, while the "bath tub" armoring protected engine and crew against the bullets from carbines and machineguns.
The Junkers building method appeared also particularly suitable, as a complete metal airplane hardly or not at all could be set on fire by the opponents hand-arms.
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 armoured 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 armoured, infantry co-operation aircraft, the Junkers J-4 received the German military designation "J-I".
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 J-7 which went through five major and minor changes in its airframe design during tests throughout 1917, 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 as the J-10, 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 by both the Junkers firm itself, and the Junkers-Fokker-Werke AG (abbreviated "Jfa"), as the Junkers D.I low wing fighter plane. The Great War ended with German Navy trials of model J-11 which was an all metal floatplane prototype.
Junkers-Fokker Werke AG
Towards the end of 1917 Junkers and Fokker formed the Junkers-Fokker Werke AG to build all-metal aircraft. This merger was forced upon Junkers by the military authorities. They felt that Junkers, unlike Fokker, lacked mass-production experience, nor was he a pilot, an asset which counted highly in those days.
The aircraft department of Junkers & Co was separated from Junkers & Co and integrated into the Junkers-Fokker-Werke AG. Additional capacity was transferred from the Fokker Werke at Schwerin. The remaining Junkers & Co was concentrated on its classical thermodynamic applications, like the gas stoves and military equipment for the war time production. Junkers & Co, as well as the Junkers Research Institute remained completely under control of Hugo Junkers.
Initially Junkers & Co (abbreviated "Jco") and the Junkers-Fokker-Werke AG produced in the old Jco facility. But on 13 June 1918 Junkers & Co left the facility and turned over into a new nearby facility. The former Jco facility was completely taken over by Junkers-Fokker-Werke AG.
After the end of World War I, Anthony Fokker retreated from Germany. On 3 December 1918 Fokker left the Junkers-Fokker-Werke AG as a partner, the partner contract was dissolved on 24 April 1919. A total of 321 aircraft were built at Junkers-Fokker-Werke AG.
During the 15 month of existence, a lot of differences were discussed between Hugo Junkers and Anthony Fokker, which mostly resulted from Fokker's priorities for his Schwerin facilities instead of the Dessau plants. Only little experience interchange was gained on both sides during this period, as Junkers was not willing to supply technology experience to Fokker and Fokker was not willing to offer significant production knowhow to Junkers. In sofar the Junkers-Fokker cooperation was unsuccessful.
However, at the end of World War I Hugo Junkers had an own aircraft production facility at Dessau, which was capable for large scale serial production. This was the nucleus for the future aircraft production plant at Dessau. On 2 June 1919 the Junkers-Fokker-Werke AG was renamed into Junkers Flugzeugwerke AG Dessau.
In December 1918 Hugo Junkers had advised his research team to design a new all metal passenger airliner, which could built the initial product for a newly formed aircraft manufacturing company.
Junkers used their J-8 layout as the basis for the F-13. The designation letter F stood for Flugzeug, aircraft; it was the first Junkers aeroplane to use this system. Earlier Junkers notation labelled it J-13. Russian built aircraft used the designation Ju 13.
The design was made under the leadership of chief engineer Otto Reuter at the Junkers-Flugzeugwerk AG in Dessau.
Construction started on February 10, 1919 and on July 25 the prototype of the Junkers F-13 (with identification D-183, which later became D-1) was flown for the first time with test pilot Emil Monz at the controls. The first flight already showed, despite the relatively low performance of the 160 hp Daimler engine, the large potential of the aircraft, which achieved a speed of 165 km/h.
Construction of the first J-13 / F-13
To make the world aware of the new aircraft and demonstrate its efficiency, a second plane – which was actually planned as a seaplane and therefore equipped with a 185 hp BMW IIIa engine – was tested. The test results indicated that at least 7 people could carried to a height of 6000 m safely. On 13 September 1919 pilot Emil Monz took the aircraft with seven passengers for a record flight, reaching a world record altitude of 6750 meters.
First Junkers F-13 "Herta"
Cockpit of the F-13
F-13 "Annelise" after the world altitude record
Junkers' aim of attracting attention through publicity paid off. Immediately foreign firms and governments began discussion with Junkers regarding production and sales of the F-13. Junkers began an extensive program of workshop construction and equipment purchase for series production of the F-13.
The Treaty of Versailles, signed only days after the F-13 flew, initially forbade any aircraft construction in Germany for several months. Article 201 banned aircraft and aircraft parts manufacture for six months after the signing of the treaty, and 202 ordered the surrender of all military and naval aviation materiel to Allied and associated governments within three months. Within six months nearly all of the major wartime aircraft producers closed their doors. Meanwhile Junkers' position appeared to strengthen.
The success of the F-13 and the attention surrounding its debut brought a succession of foreign visitors to the Dessau factory, including representatives of the Dutch, Belgian, Japanese and Czechoslovakian governments, Finnish businessmen, and also American businessmen, in particular John Larsen, a Swedish-born entrepreneur.
The Junkers F-13 was designed from the beginning with two goals: to be the first all-metal airliner and the first series-produced airliner. The design, with the engineering designation J-13, was made under the leadership of chief engineer Dipl.-Ing. Otto Reuter at the Junkers-Flugzeugwerk AG in Dessau. Construction started on February 10, 1919 and on July 25 the F-13 was flown for the first time with test pilot Monz at the controls.
Within two months after the maiden flight the F-13, powered by an 185 hp BMW III a engine, established a world record by lifting 8 people (1,153 lb, 523 kg) in 86 minutes to a height of 22,146 ft (6,750 m) on September 13, 1919. Due to this world record the F-13 became known all over the world in no time and request came in from many companies and governments.
After initial production there was a ban on all aircraft manufacturing in Germany, implemented by the Allied powers from WW I from 1921 to the middle of 1922. To earn money Junkers started his own airline Junkers Luftverkehr AG in 1921, using mostly F-13s; the company became part of Luft Hansa in 1926. In the end the F-13 was sold to over 35 countries, flew in all continents and was used operationally till 1943. The F-13 opened many routes, was used in exploration missions, and established several records in distance, height and duration.
The small single-engined monoplane was a complete new design featuring development of the metal-use on earlier planes produced by Junkers during WW I. The cantilever un-braced low-wing had an immensely strong structure of duralumin spars and corrugated dural skin. The two pilots were seated in an open cockpit with the four passengers in an enclosed cabin, in later version the cockpit was also enclosed.
Initially flown with the 160 hp Mercedes D IIIa engine, a number of other engines were used, with the 310 hp Junkers L 5 powering most of the 322 aircraft built. Of these, five were built in the Junkers factory in Moscow-Fili, known as Ju 13, they served with the Russian and Persian forces armed with a machine gun for self-defense; and two were built in Venice by Transadriatica.
There were 8 basic models, with sub-versions there were 23 models and almost all of these, alternatively to the L (landplane) version, could be fitted with either floats on the W (seaplane) or skies on the S (snow plane) version. Next to the range of engines there were: straight or swept wings; triangle, rounded and square fins with different areas; differences in the wing length or area; and more.
John Larsen, who before the war operated as the Curtiss Aeroplane and Motor Corporation's European representative, immediately grasped the importance of the F-13 and travelled to Dessau to view the plane.
Junkers realized the potential market for the F-13 in the United States, and rebuffed Larsen's initial request for a license agreement to produce the F-13. Larsen offered to buy 100 F-13's from Junkers in the first year and erect a factory to produce 100 more F-13's in the United States the following year.
Larsen sold the Junkers F-13 in the U.S.A. under the marketing name JL 6. To increase publicity and encourage sales, Junkers immediately provided two "propaganda aircraft", both of which Larsen then employed in a series of record-breaking flights across the United States and Canada throughout 1920 and 1921.
After an initial order by the United States Postal Service of eight F-13's, a series of mysterious crashes plagued the aircraft between August 1920 and February 1921. Investigations revealed the source of the problem to be American gasoline, which unlike the European gasoline mix ate through the rubber seal connecting the fuel line to the motor, resulting in a fuel leak into the engine cowling. Press coverage of F-13 accidents proved devastating to the Junkers-Larsen venture, as prospective buyers shunned the craft for less flammable designs.
In addition, the Versailles Treaty Articles 201 and 202, which came into force on January 10, 1920, ended exports of the F-13 to the United States. Finally in 1921 the Junkers-Larsen-Corporation was dissolved with the result of financial losses on both sides.
Junkers Joint Venture in Russia
In 1922 the German government asked Junkers for his support in the German-Soviet military corporation. The Soviets asked Germany to help Russia in the setup of a modern Russian aviation industry. Junkers began preparations for production in Russia. In Russia work proceeded slowly, hampered by inadequate infrastructure. On November 26, 1922, German and Russian authorities reached an agreement, under which Junkers received concessions from the Russian government. The Russians got the better of the bargain, but Junkers, faced with mounting financial pressures, accepted the terms.
Factory refitting consumed more capital than the Reichswehr provided, forcing Junkers to fund these improvements from other areas of the firm. With poor Russian transport infrastructure delaying the arrival of required machine-tools and specialized equipment, Hugo Junkers decided to build the planes in Dessau, ship them to Russia and reassemble them at Fili until the factory came online.
Fili plant, 1922
On January 11, 1923 the French occupied the Ruhr valley. The Ruhr crisis hit Junkers particularly hard, as the Düren Metal Works, Junkers' supplier of duraluminium, lay within the occupied zone, and could not deliver the raw materials. Unable to procure duraluminium from any other source, work at Dessau and Fili ground to a halt.
Russian concerns over Fili gradually mounted during 1923, and the Russians increased pressure on Junkers to speed up production. Caught in a liquidity crisis, Junkers could only continue to assemble aircraft at Fili rather than build them there, a situation the Russians justifiably argued violated the terms of the concession contract. Adding to the firm's troubles, the J-22 design experienced significant performance problems, forcing Junkers into modifying the J-21 design as a substitute.
By December 1924 the Russians received only 73 of the 100 aircraft ordered, and all of those delivered failed to meet the performance parameters established in the December 1922 contract. Junkers' involvement at Fili effectively ended in 1924, although the factory would continue to produce Junkers aircraft until December 1926, when the Soviet Union purchased the factory for six million marks.
Fili became the core of the new Soviet aircraft industry, as designers such as Andrei Tupolev began producing all-metal aircraft for the Soviet Air Force. Experience gained by Tupolev and others at the Fili complex, staffed by Junkers' best designers between 1923 and 1926, proved invaluable, and subsequent Russian aircraft reflected inherited Junkers design characteristics for decades.
The Fili facility was to be used for the construction and maintenance of a basic fleet used by the Soviet Air Force. Junkers was responsible for the setup of the production facility, as well as for the design of several aircraft types, which were required by the Soviet Air Force. The first aircraft to be designed for the Soviet forces was a reconnaissance seaplane, for which the Soviet Government placed an order of 20 aircraft. Junkers started this design under the designator J-20, also Type 20. The design was based on the Junkers J-11 seaplane design of 1918. The first J-20 was first flown in March 1922.
The Junkers J-21 (manufacturer's sales designations T-21 and H-21) was a reconnaissance aircraft designed in Germany in the early 1920s and produced in the Soviet Union at the Junkers plant at Fili for use by the Soviet Air Force. The pilot and observer sat in tandem, open cockpits. Two prototypes were constructed at the Junkers factory in Dessau, the second with a wing of reduced area. Despite the fact that the prototypes were unable to attain the performance that had been specified by the Soviets, series production commenced at Fili in August 1923 where it was known as the Ju 21.
Junkers A-20 / T-20
Junkers J-21 / T-21
J-22 (T-22): single seat fighter version, very similar to the J-21 but with its wing lowered almost to the top of the fuselage to reduce drag, the pilot's cockpit moved back further than the gunner's position on the J-21 and a more rounded rudder. The first of two J-22's flew on 30 November 1923. The J-22 / T-22 was not further produced.
Junkers J-22 / T-22
The successful unveiling of the F-13 in 1919 provided Junkers with an advanced transport design; however few airline firms existed to operate the aircraft. Junkers formulated a business model that stressed close and exclusive cooperation between the manufacturer and the airline.
Within this model Junkers Flugzeugwerke provided aircraft as working capital in exchange for a stake in the airline, and combining all existing Junkers-connected airlines into "Unions" that shared a common marketing strategy, repair and maintenance network, and aircraft pool along international and major regional routes.
For Junkers the advantages included guaranteed sales markets, ongoing returns through maintenance of aircraft and provision of flight personnel and mechanics, and the ability to influence airline policy without substantial capital outlays. In October 1920 Junkers established the Lloyd-Ostflug GmbH in partnership with the Lloyd shipping line, the Albatros firm, and the Ostdeutsche Landwerkstätten (Ola). In 1921 Lloyd and Albatros left the partnership and established the Lloyd Luftdienst GmbH.
Lloyd Ostflug Fokker D VII D-139 and Danziger Luftpost Junkers F-13 Dz 152 at Danzig, 1921
The partnership between Junkers and Ola solidified later that year as Ola merged into the Junkers in an air transport department, Abteilung Luftverkehr. A series of aeronautical expeditions were set out in North and South America, both to publicize the F-13 and investigate future airline routes. Also connections with new airline firms throughout Eastern Europe and Asia were pursued.
Airlines supported by Junkers and flying Junkers aircraft appeared in Switzerland, the Free City of Danzig, Sweden, Austria, Finland, Hungary, Latvia, and Italy by 1923. As Junkers became involved in more airline companies, rivalry between the concern and Deutscher Aero Lloyd increased in intensity and bitterness, as both sides fought to control German airspace.
By 1924 Junkers controlled the largest air transport network in the world. Forty percent of all air traffic travelled on Junkers aircraft in 1924.
Junkers aircraft flew throughout the world, from Bolivia to Japan. The air transport division grew rapidly as its domestic and foreign partnerships expanded.
Junkers F-13 in Japan
This growth came at a price, as the aircraft factory found itself producing aircraft to supply to the new "partners", but the nature of the partnership meant that returns fell far below those of sales on the open market.
Mounting costs from the firm's airline operations encouraged Junkers to remove Abteilung Luftverkehr from Junkers Flugzeugwerke's corporate structure, leading to the establishment of a new firm, Junkers Luftverkehr (Ilag), in August 1924. Despite increasing financial woes, Junkers' aircraft divisions continued to expand throughout 1925.
Aware that sales of transport aircraft such as the F-13 and the new, larger G-24 lacked the power to correct the firm's financial situation, Junkers embarked on a new course; construction of
fabrication centres on the example of the Fili plant and located in Sweden and Turkey.
These new plants could serve as maintenance and modification centres for Junkers aircraft flying the routes of an envisaged airline route linking Scandinavia, through Russia, to Asia and beyond.
Junkers G-24 / G-23 models
The increased German air traffic in the 1920s led to a requirement for a larger passenger transport aircraft. The G-24 was an enlarged development of the F-13. It was originally designed as a single-engine aircraft. Under the restrictions imposed on aircraft in Germany by the Treaty of Versailles, only low powered engines were allowed. So the Junkers company designed their large G-24 airliner to be single-engined, but built it as a tri-motor. The plan was to sell the tri-motors to airlines outside of Germany, who would then install a single, high-powered engine on the nose, and simply remove the wing centre-section plugs that carried the other two engines. However the Military Inter-Allied Commission of Control declared the G-24 design to be a military type aircraft, and outlawed it.
Junkers then resubmitted what was essentially the same design, but under a new designation: Junkers G-23. The Allied Commission ultimately allowed Junkers to build the G-23, even in the single engined version, because it was clearly an airline type.
Junkers continued to build the G24/G23 as a tri-motor because the plane could fly, and even climb, with an engine out. In 1925 most airliners were single-engined, since one big engine will usually be more efficient than several small ones. Twin-engine types could not maintain altitude with an engine out, unless they were so overpowered that the airlines could not afford to operate them. A tri-motor did not have to be so grossly overpowered, to be able to fly with an engine out.
On 1 May 1926, the newly formed German airline Deutsche Luft Hansa started flying passengers on the route Berlin - Königsberg at night using G-24 aircraft. This was the first time any airline, anywhere in the world, flew passengers at night. Between 1925 and 1929, at least 72 aircraft were manufactured, 26 of which went to Luft Hansa.
Luft Hansa decided to modify their G-24s to a single engine standard. The first modifications were done in March 1928. The wing was shortened and the centre engine was replaced with a BMW VIU engine. Junkers called this aircraft F 24ko. A total of 11 G-24s were modified to F 24 standard between 1928 and 1930. By July 1933, most of these BMW-equipped F 24s were again modified with the new Jumo 4 and designated as F 24kay. Most of these F 24s remained in service at the beginning of World War II in 1939. Most of them were used by Luft Hansa as freighter aircraft.
One of the demands of the Soviet forces for the joint venture of Junkers at Fili was the development of bomber aircraft. To fulfil this demands, Junkers designed the Junkers Ju25 as a twin engined bomber aircraft. But the development of this aircraft was to expensive for Junkers, especially regarding the outcoming difficulties with his Russian partners. Therefore Junkers advised to design a military derivate of the G24, which were produced under the designator K30. A.B. Flygindustri built the K30 under the designator R42.
In March 1925 the firm A.B. Flygindustri appeared, with its base at Limhamn, near Malmo, Sweden. Later that year in June 1925 another satellite firm appeared in Turkey, the Türkische Motoren- und Flugzeugbau-Aktiengesellschaft (Turkish Motor and Aircraft Corporation), a firm owned jointly by Junkers and the Turkish state. While these expansions seemed to lay a foundation for future success, and, in the Turkish case, provided badly needed capital that helped keep the firm afloat, neither of them solved the firm's immediate financial problems.
Flygindustri at Limhamn
By September 1925 these costs reached insurmountable levels and forced Hugo Junkers to appeal to the German government for assistance. The government asked Junkers to retreat from the economical management of his company. In November 1925 Junkers had lost control about the majority of his companies. Germany's two largest domestic airlines, Junkers Luftverkehr and Deutscher Aero Lloyd, were merged into a state-run concern, Deutsche Luft Hansa, on 6 January 1926. The new airline took over all facilities of Junkers Luftverkehr, including aircraft, equipment, and personnel. From now on Junkers participated in European air transport only as an aircraft supplier.
As Junkers Flugzeugwerke had lost most of their customers from Junkers Luftverkehrs, the economical situation of Junkers Flugzeugwerke became more and more worser in 1926 under the control of the German government. The pressure on the German government increased. By August 1926 Junkers Flugzeugwerke's monthly losses exceeded one million marks. The Transport Ministry now sought to end involvement with Junkers Flugzeugwerke at the earliest possible opportunity.
On December 10 1926 Junkers formulated a preliminary proposal. He agreed to abandon any further claims against the state in return for the withdrawal of the state supervision of Junkers Flugzeugwerke and the return of all Junkers Flugzeugwerke shares. Junkers also requested the state provide Junkers Flugzeugwerke with the ability to gather private credit so that the firm could rebuild itself.
The German government declared it would dissolve the October 1925 contract, to write off all Junkers Flugzeugwerke's state debts, and transfer its majority shareholding in Junkers Flugzeugwerke to Professor Junkers. In return Junkers had to pay the government one million marks in cash by December 31, 1926, agree to provide 3,700,000 marks worth of equipment from existing Junkers Flugzeugwerke stocks to the National Research Institute and the Air Transport Flight School, and furnish four large aircraft of the state's choosing for Deutsche Luft Hansa, with deliveries to begin on May 1, 1927.
As security the state retained possession of twelve completed Junkers aircraft until these provisions were satisfied. Additionally, Junkers was required to transfer his remaining twenty percent stake in Junkers Luftverkehr, now part of Deutsche Luft Hansa, to the state, and permanently renounce all claims "of any type" against the Reich concerning the Russian enterprise or other connections. The next day Junkers accepted the government's terms, and on December 23, 1926 signed the agreement granting him sole ownership of Junkers Flugzeugwerke.
Junkers once again possessed sole ownership of these ventures, and by March 1927 managed to transfer eight million marks back into Junkers Flugzeugwerke's coffers through both the sale of Fili to the Russian government and, in Turkey, through indirect financing procedures similar to those employed earlier in Russia.
The Reichswehr, disgusted with the outcome of events, resolved to have no further contact with the Junkers concern and excluded it from subsequent rearmament plans. The Transport Ministry, whose use of Junkers aircraft in Deutsche Luft Hansa's fleet required it to maintain relations with the firm, resolved to place the minimum number of orders possible in future.
Junkers began work on two new ambitious designs, each one dramatically different in scale. The first design, the G-38, represented the culmination of his efforts to design a large thick-winged aircraft that contained both engines and passenger space within the wing cavity. With a wing thickness of over six feet, the G-38 also utilized four engines from the Junkers Motorenbau (Jumo), fulfilling Junkers' aim of unity between engine and airframe design. When it first flew on November 9, 1929, the G-38 was the largest land-based passenger aircraft in the world, and would remain the largest until after 1945.
Junkers G-38 front view
The second design was a small single-seat design, the A 50, also known as the "Junkers Junior". In a significant departure from previous designs, Junkers planned to mass-produce the A 50 for the upper class, and market the aircraft through automobile dealerships. Although Junkers hoped for sales of over five thousand, fewer than fifty of the craft were sold, and the crash of 1929 ended any hope for a mass market.
Junkers A 50 Junior
Faced with little hope of attracting military work, Junkers concentrated on the civilian sector, hoping that continued economic stability and the growth of international aviation would provide sales outlets for the firm's products. As well as passenger aircraft such as the G-38, the firm expanded into freight-carrying designs, beginning with the W-33, a streamlined offshoot of the highly successful F-13, and culminating in 1930 in the Ju-52, a hybrid design incorporating both passenger and freight conversions.
Additionally, he expanded his research and development efforts, particularly in aero-engines, in an attempt to realize his long-term aim of developing a viable diesel aero-engine. Junkers intended to overcome his domestic problems through aggressive international marketing, building on the excellent reputation of the firm abroad established by the F-13 and opening up new markets through a series of highly publicized endurance flights. Between 1927 and 1930 Junkers aircraft achieved thirty-one world records of varying types.
Junkers W-33 / W-34
The Junkers W-33 was a direct modification of the Junkers F-13 for cargo operations. The fuselage was lower than that of the F-13 as there was no passenger compartement and the initial series did not have any windows in the cargo compartement. For combined cargo/passenger operations these windows were again introduced on later versions of the W-33. The cargo loading could be performed through a side door or through a door in the cabin roof. It was first flown on 17 June 1926.
Production began in 1927 and ran until 1934 with 198 production machines built. Most of these were built at the Junkers works at Dessau, but a small number were assembled at Junker's Swedish subsidiary AB Flygindustri and in the USSR.
W-33s were used by many operators across the world in the late 1920s and 1930s. They served as general transports and specialised mail planes. The Colombian Air Force used Junkers W-33, W-34 and K 43 in the Colombia-Peru War (1932-1933).
The Junkers W-34 was developed from the Junkers W-33. The first W-34 was first flown just a few weeks after the W-33 on 7 July 1926. While future developments of the W-33 kept the Junkers engines, the W-34 was offered with a bride area of different engines, which also influenced the outside appearance and dimensions of the W-34. Also the cabin roof was a little bit higher as on the W-33, making the W-34 more capable as a combined cargo and passenger airliner. Finally the early serial production W-34 also show differences at the tail unit, which was larger than that of the W-33. The total production numbers for the civil market were around 1,000, a further 2,024 were built under license for the German government.
One Junkers W-34 be/b3e managed to break the then current altitude record on May 26, 1929 when it reached 12,739 meters (41,402 feet). That aircraft carried the markings D-1119 and it was equipped with a Bristol Jupiter VII engine.
In the Spring of 1927, the concern initiated an attempt to supersede Lindbergh's feat by successfully crossing the Atlantic from east to west.
One project involved a seaplane conversion of a G-24 crossing the Atlantic from Portugal via the Azores. The second project envisaged a direct land-to-land crossing from Europe to the United States.
Two Junkers W-33's were converted into long-range endurance aircraft, complete with extra fuel tanks in the wing cells.
The first W-33 "Europa" successfully broke the world endurance record, remaining aloft for over fifty-two hours, but later crashed at the first attempt to cross the Atlantic in poor weather at an airfield near Bremen.
On April 12-13, 1928 the Junkers W33 D-1167 "Bremen" flew from Baldonnel near Dublin in Ireland to Greenly Island, Canada off Labrador in 37 hours. Strong westerly winds took them north of their intended destination, New York, but they landed safely. Enormous celebrations began when word reached Germany that the Bremen had completed the Atlantic flight successfully.
W33 D-1167 "Bremen" Atlantic flight
W-33 "Bremen" after its Atlantic crossing
With the W33 D-1167 "Bremen"
A sensational event was the first flight of the four-engine large transport aircraft G-38 on 6 November 1929 from Dessau. It was at that time the world's largest civilian land aircraft. The G-38 carried a crew of seven. On board mechanics were able to service the engines in flight due to the G-38's blended wing design which provided access to all four power plants. The plane was unique in that passengers were seated in the wings, which were 1.7 meter thick at the root. There were also two seats in the extreme nose. The leading edge of each wing was fitted with sloping windscreens giving these passengers the forward-facing view usually available only to pilots. There were three 11 seater cabins, plus smoking cabins and wash rooms.
Two prototypes were constructed in Germany. Both planes were in service simultaneously until 1936, when the first G-38, D-AZUR, crashed in Dessau during a post-maintenance test flight. Lufthansa had to write off this aircraft due to the extensive damage. The second G-38, D-APIS, flew successfully within the Lufthansa fleet for nearly a decade. With the outbreak of world war II the G-38 was pressed into military service as a transport craft by the Luftwaffe. It was destroyed on the ground during an allied air raid on Athens on 17 May 1941.
During the 1930s, the design was licensed to Mitsubishi which constructed and flew a total of six aircraft, in a military bomber/transport configuration, designated Ki-20.
For Junkers, the Bremen's success also represented an important step forward for the concern in its attempts to reassert its technical superiority in the face of challenges from other domestic rivals, particularly the Dornier Flugzeugbau, whose flying-boat designs dominated the market by 1927.
Dornier Do J Wal (Whale)
Junkers realized that civil aviation's real growth market lay in the United States. He again traveled to America, hoping to build on the publicity and prestige generated by the "Bremen's" flight to corner the imminent transatlantic aviation market.
Unfortunately, as with the G-38 and the A-50 programs, his vision outran the pace of contemporary reality. Disappointed, he returned to Dessau in June 1928 and resolved to focus his attention on Europe, most of all in re-establishing a relationship with German state agencies.
Junkers Works' reputation as a research center remained undiminished. Junkers Flugzeugwerke remained Germany's largest aircraft producer. Professor Junkers offered the G-38 design as a seaplane to the Transport Ministry to demonstrate his adherence to new state priorities. The Transport Ministry agreed to fund the G-38's development.
The G-38 negotiations brought Junkers into line with the requirements placed on other firms by the state within the aircraft industry. Junkers focused attention primarily on events within Germany in 1928, specifically on the Reichstag's allocation of aviation subsidies.
Accepting the restrictions of the Versailles Treaty, Gotthard Sachsenberg proposed German defense needs would be better served through the creation of a fleet of fast transport aircraft that could be instantly converted into bombers and act as a strategic deterrent by guaranteeing a rapid response to any attack. Naturally, the design envisaged for such a fleet was the new Junkers Ju 52.
Junkers Ju 52
The Junkers Ju 52 was one of the most successful designs of Hugo Junkers and Junkers Flugzeugwerke. The design was started in 1928 and was principly based on the W33/W34. Like its precessors, the Ju 52 was designed as a cargo aircraft, which should offer more capacity than the earlier designs. First designs saw a highlevel monoplane with one and two engines, but later the design was changed to a cantilever monoplane with one engine similar to the F 24. These single-engined Ju 52s were later designated as Ju52/1m. However, the single-engine model was underpowered, and after seven prototypes had been completed, all subsequent Ju 52s were built with three radial engines as the Ju 52/3m. Originally powered by three Pratt & Whitney Hornet radial engines, later production models mainly received 770 hp BMW 132 engines, a licence-built refinement of the Pratt & Whitney design.
Lufthanse Junkers Ju 52 in 1934
Junkers Ju 52
Before the nationalisation of the German aircraft industry in 1935, the Ju 52/3m was produced principally as a 17-seat airliner, primarily used by Luft Hansa. The Junkers Ju52/3m was a pure civil aircraft until 1935, when the Nazis announced the foundation of an official Luftwaffe in Germany.
At this time the Reich Aviation Ministry was looking for an adequate bomber aircraft in Germany, which would become available shortly. But most German aircraft did not fit with the Reich Aviation Ministry demand. Therefore the Reich Aviation Ministry decided to use the Ju52/3m as a temporary bomber solution until dedicated bomber aircraft would become available in Germany. In 1934 the Junkers Flugzeugwerke received an order for a total of 1200 Ju52/3m bomber aircraft. The Ju52/3m was redesigned and two machine gun turrets were added in the rear cabin, one in the roof and one in the bottom of the aircraft. The passenger cabin was redesigned as the bomb compartement, where up to 32 50kg-bombs could be put in.
Due to the worldwide economical crisis with the collapse of the New York Stock Exchange in October 1929, Junkers missed the necessary orders from airlines. The circumstances magnified Junkers' contemporary financial difficulties and revealed several key deficiencies within the group's corporate structure.
As the international Depression deepened, unsold aircraft began to accrue at the Junkers Flugzeugwerke plant; between 1929 and 1930, only fifty-two aircraft were sold, less than half of those produced. Seventy years old in 1929, Hugo Junkers proved resistant to change, and he continued to oppose rationalization or reductions of the group's research initiatives.
Other executives within the Junkers Works increasingly criticized Junkers' sole direction of the concern and cited the need for a revision of corporate strategy due to imminent financial collapse. This criticism emerged in 1931, and led to a shake-up of the firm's executive leadership.
On November 20, 1931 several executives were removed from Junkers Flugzeugwerke, and Junkers replaced them with men he considered more loyal, including his former secretary Adolf Dethmann and his twenty-five year old son Klaus Junkers. Dethmann and Klaus Junkers instituted a series of reforms designed to increase efficiency and decrease costs. Unfortunately these initiatives proved unable to offset the firm's growing debts, and Junkers Flugzeugwerke, together with the rest of the Junkers Works, lurched toward insolvency.
Jumo 4 engine
Pratt & Whitney R-1690 Hornet radial engine
Financial difficulties within Junkers Motorenbau (Jumo) provided the catalyst for the entire concern's insolvency.
Engine development followed two paths; further refinement of high-performance gasoline engines for use at higher altitudes, and the systematic development of a diesel aero-engine known as the Jumo 4.
A prototype of the Jumo 4 appeared in early 1928, and expectations quickly rose that Jumo soon would form another foundation of the concern's self-financing structure.
Between 1927 and 1933 the Jumo 4 served as the powerplant base for aircraft design, and Junkers Flugzeugwerke's Ju 52 incorporated plans to use the engine as its primary power plant. Engine development and production required heavy investments in time, personnel, and materials. The Jumo 4 required two years of workshop and flight testing before it could be considered for production, and endurance testing continued until September 1930. Thus for over two years, despite advances in technical areas, no return materialized.
When the Ju 52 appeared in October 1930, Deutsche Lufthansa expressed interest and declared they would purchase the design, but with three engines rather than one, and with engines designed in the United States produced under license by Jumo rival BMW. Faced with Jumo debts that Junkers could not pay, Junkers began negotiations with the Transport Ministry for an extension of credit in an effort to avoid complete collapse. The Transport Ministry called for a thorough examination of the Junkers Works' financial status before further credit could be extended.
At the same time an agreement between Junkers and the Transport Ministry granted a further moratorium of one year on Jumo's debts in exchange for the mortgaging of the majority of Junkers Flugzeugwerke shares.
Faced with bankruptcy, Junkers declared the Junkers Works illiquid on 22 March 1932, and requested the commencement of insolvency proceedings. Per the Transport Ministry's recommendation, the Creditor Committee ordered the creation of a new company, Junkers Flugzeugwerk Betriebs with new management independent of the Junkers Works.
Faced with bankruptcy and the dismissal of his entire workforce, Junkers had little choice but to accept the Committee's decrees. Junkers Flugzeugwerke was required to suspend operations, and the new firm would take over all Junkers Flugzeugwerke production facilities at Dessau. Despite these resolutions, no agreement emerged concerning the properties and assets formally recognized as wholly owned by Junkers himself. As sole owner of all 178 patents registered by the concern, he sought to use them as a lever to retain control.
The Transport Ministry, as principal Junkers Flugzeugwerke and Jumo creditor, sought to force Junkers into surrendering his patents to the state. On 6 November 1932, both sides formally signed an agreement that allowed Junkers Flugzeugwerke and Jumo to use applicable patents. The signing of this agreement ended the insolvency proceedings at the Junkers Works.
Although Hugo Junkers managed to emerge from near bankruptcy and retain control of his concern for the second time in seven years, this time liberation came at a heavy price. On 4 November, in order to redeem Junkers Flugzeugwerke shares mortgaged under the terms of the aircraft firm's settlement, Hugo Junkers was forced to sell the concern's core company, Junkers & Co, to Robert Bosch AG. Also, his continued ownership of majority shareholdings of Junkers Flugzeugwerke and Jumo, as well as the concern's patents, encouraged further action against him.
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 would comply with their plans. Shortly after, his holdings were expropriated and he was placed under house arrest at his home at Bayrischzell, and he was not allowed to have visitors or work without police presence. He continued to fight for his freedom, but his health became worse during the year.
Hugo Junkers died on his 76th birthday, February 3, 1935, while still under house arrest. The nationalized Junkers company became one of the most prominent German aircraft manufacturers. After the war, aircraft production ended, and with the absorption of a small aero-engine plant by the Messerschmitt group in 1975, the name Junkers disappeared entirely.
- Kennzeichen Junkers (German); author: Holger Lorenz
- Power and Initiative in twentieth century Germany; the case of Hugo Junkers; author Richard Byers
- Aeronautical Research in Germany: From Lilienthal Until Today, Volume 147; authors Ernst Heinrich Hirschel, Horst Prem, Gero Madelung
- www.flugzeug-lorenz.de (German)
- www.junkers.de (German)