Junkers F 13

The Junkers F 13 is the world's first all-metal transport aircraft, designed and produced by the German aircraft manufacturer Junkers.

Produced shortly after the end of the First World War, it was a cantilever-wing monoplane with enclosed accommodation for four passengers and a two seat open cockpit. Like all Junkers duralumin-structured designs, from the 1918 J 7 to the 1932 Ju 46, (some 35 models), it has an aluminium alloy (duralumin) structure entirely covered with Junkers' characteristic corrugated and stressed duralumin skin. Internally, the wing was built up on nine circular cross-section duralumin spars with transverse bracing. All control surfaces were horn balanced.

A total of 322 aircraft were manufactured, a considerably large number for a commercial airliner of the era, and were operated all over the world. It accounted for over a third of air traffic in the early 1920s. It remained in production for thirteen years and in commercial service for more than thirty. There were many versions including floatplanes for water landing, skis, mailplane, and different engines. Several survive in various states of repair in museums, and a replica of the type was put back in production in the 2010s, taking flight once again nearly a century after the type first flew.

Development

thumb|left|F 13 cockpit

thumb|The Junkers F 13 viewed from above at the [[Musée de l’air et de l’espace]]

thumb|Deutsches Museum's F 13

What would become the F 13 originated in the work of Professor Hugo Junkers and his Research Institute in Dessau, Germany throughout the 1910s. These efforts were responsible for producing multiple new ideas pertaining not only to aerodynamics but also the employment and working of lightweight metal construction in aviation. was a very advanced aircraft when built, an aerodynamically clean all-metal low-wing cantilever monoplane. It was the world's first all-metal passenger aircraft and Junkers' first commercial aircraft. 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 F 13 first flew on 25 June 1919, powered by a 127 kW (170 hp) Mercedes D.IIIa inline upright water-cooled engine. The first production machines had a wing of greater span and area and was furnished with the more powerful 140 kW (185 hp) BMW IIIa upright inline water-cooled motor.

Many variants were built using Mercedes, BMW, Junkers, and Armstrong Siddeley Puma liquid-cooled inline engines, and Gnome-Rhône Jupiter and Pratt & Whitney Hornet air-cooled radial engines. The variants were mostly distinguished by a two letter code, the first letter signifying the airframe and the second the engine. Junkers L5-engined variants all had the second letter -e, so type -fe was the long fuselage -f airframe with a L5 engine.

The F13 was the basis for developing the Junkers W 33 and Junkers W 34.

Design

The Junkers F 13 was an all-metal transport aircraft; its construction and several of its design features, such as its cantilever wing, were particularly noteworthy for the era. Unlike traditional wings of the era, which had to use external struts and guywires out of necessity, the wing of the F 13 lacked any stay-wires; their elimination meant that a major source of drag was entirely avoided. Another advantage was that, while the polar curve for thin profile wings typically had a relatively restricted range of application, such as for high-speed flight or a rapid rate of climb, of a higher climb, the polar curve of thicker profile wings could perform more adequately across both circumstances.

In terms of its material composition, the F 13 had intentionally discarded traditional materials, such as wood and fabric, in favour of an all-metal approach that had been pioneered by Junkers. This switch eliminated concerns over the variable quality of available wood, and the procurement difficulties in obtaining high quality wood that would be well-suited for aeronautical purposes. It also dispensed with various other concerns, as it was perceived as more difficult to maintain the calibrated dimensions of wood due to warping, the same factor also hindered interchangeability; metal posed less of a fire hazard as well. Unlike Junker's early metal aircraft, which was composed of steel and thus quite heavy, the F 13 was made of duralumin, a light-weight alloy that would find widespread use in aeronautical circles. This metal has greater uniform strength to the aircraft, which made it easier to design; greater ease of calculation increased the economics of this choice as well.

Somewhat offsetting the difficulties of developing a new arrangement to permit the installation of all supporting framework internally, the use of metal enabled a substantial number of new construction features to be adopted. Although the specific gravity of duralumin is greater than that of wood, the weight of the Junkers F 13 was beneath that of all other airplanes, wood or metal, of the same class, as a result of thorough aerodynamic studies conducted by the company. Furthermore, it was also felt that the metal approach would increase structural safety and serviceability. In comparison to its wooden contemporaries, the F 13's all-metal approach was slower to fatigue; it was also less expensive to protect against humidity and most other atmospheric conditions. Termites were unable to damage metal aircraft.

The flight controls were fairly conventional, both the elevator and ailerons were actuated by the pilot via a column with a wheel while the rudder was operated using pedals. Various sliding doors were present for inspection and serviceability purposes for the various control cables, levers, and tubes. Provision was made for the installation of dual flight controls, a feature that was thought to be of particular importance during long-range flights.

The undercarriage was largely composed of steel tubing; a total of four streamlined supports functioned as spring struts.

The aerodynamic efficiency of the F 13 meant that less engine power than had been anticipated could be used; various engines from a variety of suppliers could be installed. Easy access to all points of the engine was possible while various components could be exchanged within a short timeframe. The frontal radiator was specially designed by Junkers to possess a high level of efficiency as well as being relatively lightweight; the pilot was able to regulate the engine temperature via the adjustable shutters. Those aircraft intended for use in a tropical country were typically provided with an additional radiator. Considerable attention was paid to the development of propellers, which was shaped by extensive research into aspects such as the pitch, blade section and diameter. The initial propellers used were composed of laminated wood that was protected by metal along their leading edges and achieved a mechanical efficiency at least equal to that of wooden ones. Junkers also worked on metal propellers of its own make, the hollow sections of which diminishes in line with the laws of bodies of uniform resistance. Advantages presented by metal propellers include the ability to replace a single blade (instead of the whole propeller), a lack of sensitivity to climate influences, and the potential to shape the propeller hub to vary the propeller pitch for either speed or climb.

Behind the single engine was a semi-enclosed cockpit for the crew, roofed but without side glazing. There was an enclosed and heated cabin completed with both with windows and doors. Passenger seats were fitted with seat belts, unusual for the time. The F 13 has a fixed conventional split landing gear with a rear skid, though some variants were fitted with floats or on skis. The cabin was relatively sizable and elegantly furnished for the era; in addition to the four passengers it accommodated, room for another passenger or crew member was present alongside the pilot.

Operational history

thumb|right| F 13 fy D-190 of Lloyd Ostflug then Junkers Luftverkehrs AG.

thumb|The F13 cabin for passengers

Any manufacturer of civil aircraft immediately after World War I was faced with competition from the very large numbers of surplus warplanes that might be cheaply converted – for example, the DH.9C. German manufacturers had further problems with the restrictions imposed by the Inter-Allied Aeronautical Commission of Control, which banned the production of warplanes and of any aircraft in the period of 1921-22. Junkers picked up orders abroad in 1919 in Austria, Poland and the USA and, in the following years with SCADTA (Colombia) and the United States Post Office Department. John Larsen Aircraft in the USA purchased a production licence, their machines being designated JL-6. In 1922 there were sales in England, France Italy and Japan.

The F13 was a very popular civilian aircraft, carrying it is estimated 40% of the world's air traffic in the early 1920s.

Junkers Flugzeugwerke (SD303) has resurrected the Junkers F 13 as an all-new airplane to honor Hugo Junkers’ achievements. The company completed the aircraft in 2016 and it is at EBACE commemorating the type's maiden flight 100 years ago. The model is available for purchase, and three others like it are currently under construction. Work was in progress on the second and third aircraft during 2019, with airframe number two's maiden flight planned for early that summer.

The replica F 13 made its maiden flight on 15 September 2016, the culmination of many of years of work on the part of supporters of the project. . The replica was created from original blueprints and also a laser scan of the type at the Museum of Air and Space at Le Bourget, Paris. The replica has 2600 parts and tens of thousands of rivets and is powered by a Wasp radial engine.

;Rimowa Junkers F 13

:Modern replica first flown 15 September 2016. With the approval of the Junkers heirs, Rimowa Junkers was renamed Junkers Flugzeugwerke AG, and moved to Altenrhein. Their models have modern features, like more and better instruments, while the outward appearance is the one of a Junkers-Larsen JL-6.

Operators

thumb|Ad Astra F13 circa 1920

thumb|Finnish F13 in the 1920s

thumb|F13 floatplanes in Budapest, Hungary

; ( after 1926)

Afghan Air Force acquired four aircraft from 1924 through 1928.

;

Argentine Air Force - three aircraft

;

Austrian Air Force (1927-1938)
Österreichische Luftverkehrs AG (ÖLAG) started flying with F 13 and operated 24 aircraft

;

SNETA

;

Lloyd Aéreo Boliviano received the first F 13 as a gift from the German community on the occasion of the centennial of Bolivian independence.

;

Syndicato Condor - Serviços Aéreos Condor
Varig

;

Bulgarian Air Force
Bunavad operated two aircraft between 1927 and 1928.

;

Chilean Air Force

;

Avianca as SCADTA
Colombian Air Force

; Free City of Danzig

Danziger Luftpost
Lloyd Ostflug

;

Aeronaut operated F 13 between 1922 and 1927.

;

Aero Airways
Kauhajoki Flying Club
Finnish Air Force
Finnish Border Guard

;

Junkers Luftverkehr, primary user until merger with Deutscher Aero Lloyd into Deutsche Luft Hansa
Deutsche Luft Hansa operated about 110 aircraft, a large part taken over from Junkers Luftverkehr.

;

Aero R.T. operated six aircraft between 1923 and 1927.
Aeroexpress Rt. (1923−1930)
Royal Hungarian Air Force

;

Air Iceland operated three aircraft between 1928 and 1931.

;

Imperial Iranian Air Force

;

Latvijas Gaisa Satiksmes Akciju Sabiedriba - national airline, operated three aircraft in 1922–1925.

thumb|First Lithuanian Air Mail stamp (1921) featured Junker F13.

;

Lithuanian Air Force for a short period operated single aircraft, which crash-landed in Lithuania after illegally passing its border in 1919.

Mexican Air Force

;

Mongolian People's Army Air Force operated three aircraft between 1925 and 1931.

;

Aero-Targ leased six aircraft from Danziger Luftpost in 1921.
Aerolloyd (later renamed Aerolot) operated 16 aircraft between 1922 and 1929.
LOT Polish Airlines took over 15 remaining aircraft from Aerolot and operated them between 1929 and 1936.

;

Serviços Aéreos Portugueses operated one aircraft between 1929 and 1931.

;

LARES
Royal Romanian Air Force

;

Deruluft
Aviaarktika operated several aircraft.
Soviet Air Force

;

South African Airways operated four aircraft obtained from Union Airways.
South African Air Force

;

Union Aérea Española UAE
Fuerzas Aéreas
Cruz Roja Española

;

Swedish Air Force
Aktiebolaget Aerotransport

;

Ad Astra Aero operated at least four F 13s (registered CH-91/92/93/94) between 1919 and probably 1930.

;

Turkish Air Force operated three aircraft between 1925 and 1933.
Turkish Air Post operated two ex-military aircraft between 1933 and 1938.
General Command of Mapping (Turkey) operated one ex-air force aircraft (serial no: 882) equipped with aerial photo system from 1933 to 1938.

;

Civil register lists five F 13s during the 1930s

;

United States Post Office Department
United States Navy

Accidents and incidents

thumb|Emergency landing of Finnish [[Finnair|Aero Oy's D335 by the VR warehouses, July 6, 1925, Helsinki]]

thumb|Another angle of the damaged airplane

On 1 September 1920, a Junkers-Larsen JL-6 caught fire and crashed in Morristown, NJ. Max Miller, the United States Air Mail Service's first pilot was at the controls and, along with his mechanic/crewman, Gustav Reierson, perished. They managed to eject all nine mail bags before the plane hit the ground.
On 8 June 1924, a SCADTA F 13, registration A13, stalled and crashed into a tree on takeoff from Barranquilla, Colombia, killing all five on board.
On 10 March 1926, a Latvijas Gaisa Satiksmes F 13, c/n 579, registration No. B-LATA, operating for Aero O/Y, crashed on approach to Helsinki. No fatalities were registered.
On 22 March 1925, a Zakavia F 13, registration R-RECA, crashed on takeoff from Tiflis, Georgia, killing all five on board. This crash is particularly famous because three high ranking Soviet officials died in the crash. Solomon Mogilevsky, Alexander Myasnikov, and Georgi Atarbekov who were flying to meet Trotsky who was in convalescence in Sukhum.
On 24 July 1926, a Deutsche Luft Hansa F 13, registration D-272, crashed at Juist, Germany due to weather, killing all four on board.
On 3 September 1926, a SCADTA F 13, registration A-10, collided with cloud-obscured terrain between Honda and La Victoria, Colombia. The two crew and two passengers were injured, and the aircraft was a total loss.
On 27 July 1927, a Deutsche Luft Hansa F 13, registration D-206, crashed at Amöneburg, Germany after attempting an emergency landing due to engine failure, killing all five on board.
On 26 May 1928 at 08:15, a Deutsche Lufthansa Junkers F 13, registration D-583, crashed at Hahnenberg, Radevormwald, Germany due to pilot error, killing three of five on board.
On 21 July 1930, a Croydon-based Walcot Air Line F 13, registration G-AAZK, crashed at Meopham, near Gravesend, Kent, due to structural failure, killing all six on board including its second pilot, Lt Col George L P Henderson, a pilot with considerable skill and war-time experience.
On 12 July 1932, Czech industrialist Tomáš Baťa died, together with pilot Jindrich Broucek, when his Junkers J13, registration D-1608 crashed after taking off in heavy fog.
On 2 November 1932 a Deutsche Luft Hansa F 13, registration D-724, crashed at Echterspfahl, Germany due to wing separation, killing all five on board.
23 July 1933, registration CF-ALX named "City of Prince George" crashed into a tree on takeoff in the Canadian wilderness. The wreck was later recovered in 1981 and used as the basis for restoration for museum piece. The aircraft was originally named the Königsgeier (King Vulture).]]There are five surviving F 13 airframes, all in museums.
c/n 715, SE-AAC, ex-D-343: On display at the National Museum of Science and Technology (Sweden), Stockholm, Sweden.
c/n 2018: On display at the Deutsches Museum, Munich, Germany. Exported to Afghanistan in 1928 and returned to Germany in 1968. Marked as D-366.
c/n 2050 CF-ALX: On display at the Royal Aviation Museum of Western Canada, Winnipeg, Canada. Crashed near McConnell Lake, British Columbia, in 1933 and recovered in 1981. Wreckage formerly displayed at the German Museum of Technology, Berlin, Germany before being restored.

thumb|left|F 13 remains from Canada in the Deutsches Technikmuseum Berlin

;In storage or under restoration

c/n 574, CH-59: Part of the collection of the Hungarian Technical and Transportation Museum, Budapest, Hungary. Used by Charles I of Austria to fly from exile in Switzerland in an attempt to take power in Hungary.

;Replicas

Tomas Bata Memorial, Zlín, Czech Republic

Specifications (F 13)

thumb|200px|Junkers F 13

References

Citations

Bibliography

Andersson, Lennart. "Chinese 'Junks': Junkers Aircraft Exports to China 1925-1940". Air Enthusiast, No. 55, Autumn 1994, pp. 2–7.
Andersson, Lennart. "Talkback". Air Enthusiast, No. 18, April – July 1982. p. 80. .
Dulaitis, David D. "Talkback". Air Enthusiast, No. 18, April – July 1982. pp. 79–80. .
Gerdessen, F. "Estonian Air Power 1918 – 1945". Air Enthusiast, No. 18, April – July 1982. pp. 61–76. .
Guest, Carl-Fredrick. "Talkback". Air Enthusiast, No. 18, April – July 1982. pp. 78–79. .
"All-metal Junkers airplane, type F 13" National Advisory Committee for Aeronautics, 1 May 1926. NACA-AC-6, 93R14603.

External links

Junkers F13 on the Hugo Junkers Homepage.
Junkers F 13 photos from the Budapest Aviation Museum

Development

Design

Operational history

Operators

Accidents and incidents

Specifications (F 13)

See also

References

Citations

Bibliography

Further reading

External links

Development

Design

Operational history

Operators

Accidents and incidents

Specifications (F 13)

See also

Related developments

References

Citations

Bibliography

Further reading

External links