Junkers W 33

Junkers
Industry	Aircraft manufacturing
Founded	1916
Headquarters	Dessau, Germany
Products	Aircraft, including Junkers W 33

The Junkers W 33 was a German single-engine, low-wing monoplane transport aircraft from the 1920s, developed as a larger successor to the Junkers F 13 and later evolving into the Junkers W 34. It was characterized by Junkers' distinctive use of corrugated aluminium alloy skin stretched over an aluminium tube framework. A notable achievement was the Bremen aircraft, which completed the first nonstop heavier-than-air transatlantic flight traveling east to west.

Design and development

Building upon the design principles established with the J 7 fighter,^[1] the W 33 featured a duralumin framework sheathed in corrugated duralumin panels. Unlike the prevalent biplane designs in the UK and US during that era, cantilever monoplanes were more typical in Europe. Junkers set itself apart by extensively applying tightly corrugated metal skins; however, unlike the stressed skins used on aircraft such as the Rohrbach Roland, these panels were not load-bearing. The W 33 directly descended from the four-seat 1919 Junkers F 13, maintaining similar wingspan and length but introducing a more angular fuselage and a freight door on the port side.^[1]

Initial versions of the W 33 retained open cockpits akin to those on the F 13 but eliminated the central structural division between pilot and co-pilot positions. Certain transatlantic models were outfitted with enclosed cockpits. Propulsion came from a Junkers L5 inline water-cooled engine, also utilized in later variants of the F 13. The primary distinction between the W 33 and its successor, the W 34, lay in engine type: the W 33 employed an inline engine, whereas the W 34 generally incorporated radial engines alongside minor cockpit refinements and detail modifications.

The aircraft featured a traditional fixed landing gear with a tailwheel; early models had main wheels connected by a hinged cross axle, which was later replaced by independent three-legged undercarriage assemblies. The letter 'W' in its designation likely stood for Wasserflugzeuge (seaplane), although W 33s operated both as landplanes and floatplanes equipped with twin main floats supported by struts.

The prototype D-921 made its maiden flight as a seaplane on 17 June 1926 at Leopoldshafen on the Elbe River near Dessau.^[2] Production spanned from 1927 until 1934, resulting in 199 units primarily constructed at Junkers' Dessau facility, with limited assembly taking place at AB Flygindustri in Sweden and at Fili near Moscow.^[3] These subsidiaries helped bypass post-World War I Allied restrictions on German aircraft manufacturing.

In July 1934, a W 33 was utilized for testing the Junkers Jumo 210 engine, flying with a 680 horsepower variant on July 5.^[4]

Operational history

Soon after their initial flights, two early W 33 prototypes took part in the Deutschen Seeflug seaplane contest held at Warnemünde in July 1926, with one prototype securing second place.

Throughout the late 1920s and into the 1930s, W 33s were operated worldwide as transport and mail aircraft. Deutsche Luft Hansa employed four units for mail services beginning in 1929. Other roles included aerial surveying and agricultural spraying. Although considered outdated by later standards, some remained in service with the Luftwaffe as training aircraft alongside W 34s.

During the Colombia-Peru War (1932–1933), the Colombian Air Force utilized Junkers W 33, W 34, and militarized K 43 models. The Ethiopian Air Force operated one W 33c during the Second Italo-Abyssinian War.

A single W 33g served as an air ambulance for the Swedish Air Force from 1933 to 1935 under the designation Trp2, possibly assembled at Linhamm like four others exported to Australia. After World War II, it continued service as a utility transport and took part in search-and-rescue operations during the 1952 Catalina affair, an incident involving Soviet MiG-15 fighters shooting down a Swedish reconnaissance plane.

Out of seventeen W 33s assembled in Russia from imported components, at least nine appeared on civil registers. In Russian service, these were designated PS-3 (third passenger aircraft), with at least seventeen enhanced versions produced by GVF workshops under the designation PS-4.

Flight records

The Junkers W 33 achieved numerous milestones, most notably with the Bremen, which completed the inaugural east-to-west transatlantic flight by airplane.

Earlier transatlantic crossings had predominantly followed west-to-east routes, benefiting from favorable winds. However, on April 12–13, 1928, the Bremen (D-1167) journeyed from Baldonnel, Ireland to Greenly Island, Canada against these prevailing winds, taking 37 hours. Strong gusts pushed the plane northward beyond New York, resulting in minor damage that necessitated repairs before the flight could proceed. Today, this aircraft is exhibited at Bremen Airport. Another plane named Europa never left Germany.

In August 1927, a W 33 established Class C world records for both endurance (52 hours and 22 minutes) and distance (4661 km) during a single flight circling Dessau, piloted by Johann Risztics and Edzard. Previous flights had also set comparable duration and distance records while carrying a 500 kg payload. At the same time, similar records were achieved in the Class Cbis seaplane category. Additionally, a W 33 modified with a radial engine (often mistakenly identified as a W 34), piloted by Willy Neuenhofen, set an altitude record of 12,740 meters on May 26, 1929.

The first W 33 assembled in Sweden was finished in May 1930 and subsequently delivered to Japan. On September 24, 1932, J-BFUB Third Hochi Japan-US departed from Sabishiro Beach near Misawa in an attempt to cross the Pacific Ocean but vanished south of Etorofu Island; despite thorough search efforts, no wreckage or survivors were ever located.

Accidents and incidents

On May 15, 1932, D-1925 Atlantis, piloted by Hans Bertram and Adolph Klausman, was forced to land on the Kimberley coast of Western Australia during a flight between Kupang and Darwin due to navigational mistakes; the crew was rescued in June of that year.
On October 29, 1932, D-2017 Marmara operated by Luft Hansa crashed off the coast of Kent during a cargo flight from Croydon to Cologne.

Variants

Junkers W 33: Models -b, -c, -dd, and -f powered by a Junkers L5 water-cooled inline engine.
W 33 -c3e and -he equipped with a Junkers L5G water-cooled inline engine.
W 33 -dGao fitted with a Siemens Sh 20 radial engine.
Junkers W 34: A six-passenger evolution powered by various radial engine types.
Junkers K 43: Swedish-manufactured bomber and reconnaissance variant armed with machine guns.
PS-3: Soviet designation for German-built units.
PS-4: Locally produced Soviet modification.
Trp2: Swedish Air Force designation.

Civil operators

Syndicato Condor

Canadian Airways

Eurasia

SCADTA, one registered as C-33 and sold to Colombian Air Force in 1932.

Deutsche Luft Hansa

One W.33d "Súlan" registered for civil use.

Two aircraft registered for civilian operations.

Three aircraft listed on civil registers.

Deruluft
Dobrolyot, which operated seven units.
TsARB (Central aviation repair base), operating ten aircraft.

Military operators

Colombian Air Force, which operated one W 33 acquired from SCADTA between 1932 and 1939.

Ethiopian Air Force, operating one W 33c from 1929 until 1936.

Luftwaffe

Imperial Iranian Air Force, which used three W 33d models between 1929 and 1943.

Mongolian People's Army Air Force, operating five aircraft starting in 1931.

Swedish Air Force, which employed one W 33g (1933–1938) and two W 34h (1934–1953).

Soviet Air Force, operating twenty-five units.