Junkers G 24


The Junkers G 24 was a German three-engine, all-metal low-wing monoplane passenger aircraft manufactured by Junkers from 1925. Junkers F 24 was the designation for single-engine versions of the same aircraft.

Design and development

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 by Ernst Zindel 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 G24 airliner to be single-engined, but built it as a tri-motor. With three low powered engines the G24 could fly, but was not a viable airliner. 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 center-section plugs that carried the other two engines. However the Military Inter-Allied Commission of Control declared the G24 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 G23. The Allied Commission ultimately allowed Junkers to build the G23, even in the single engined version, because it was clearly an airline type. The plane was always marketed under the G24 designation.
Junkers continued to build the G24/G23 as a tri-motor, because the ruse to circumvent the Allied restrictions also had the benefit that the plane could fly, and even climb, with one 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 one engine out.
On May 1, 1926 newly formed German airline Deutsche Luft Hansa started flying passengers on the route Berlin – Königsberg at night using G24 aircraft. This was the first time any airline, anywhere in the world, flew passengers at night. Previously airlines had flown only mail and freight after dark. If an engine failed, the pilot bailed out by parachute, since a forced landing in the dark is too dangerous. The Junkers G24 could carry passengers, since there would not be any forced landings. The G24s of Luft Hansa also had blind flying instruments and radio navigation.
The aircraft was manufactured in three main batches, with different engine alternatives. Between 1925 and 1929, at least 72 aircraft were manufactured, 26 of which went to Luft Hansa. The G 24 managed to set a number of aviation records involving pay loads. Fritz Horn flew 2,020 km with a payload of 1,000 kg on 14 h 23 min, having an average speed of 140 km/h, setting a new world record.
On 24 July 1926, two G 24s became famous after having flown the 20,000 km route between Berlin and Peking in just 10 stops. This flight ended on 8 September. It was initially meant that they would fly all the way to Shanghai, but they were prevented by military conflicts. On 26 September 1926, the two aircraft landed again in Berlin. Later during the year, a trans-Euro-Asiatic line was created.
Luft Hansa, which operated the largest G 24 fleet in the world, 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 center 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.
The Soviet-German aircraft cooperation in the 1920s led to a Soviet request for a new bomber aircraft. Junkers then designed the Junkers Ju 25 as a twin-engine bomber. But the development of this aircraft was too expensive for Junkers, especially since there were some difficulties with his Russian partners. Junkers then advised his lead designers – Ernst Zindel and Hermann Pohlmann – to design a military derivate of the G 24. By November 1924, the new aircraft was ready, and given the designation G3S1 24 and it was a direct modification of the G 24ba. The aircraft was said to be an air ambulance. Junkers followed up this design with several reconnaissance designs e.g. the G1Sa 24 which was a modified G 24 with only a single engine. The next design, the G2sB 24 was also a bomber, directly derived from the G 24he. This aircraft had a new center wing section and a new nose section, to allow an open shooting area to the forward areas. Junkers decided to produce this design as the general military version of the G 24 and gave it the designation K 30 in 1926.
In 1926, the Finnish airline Aero O/Y acquired a Junkers G 24, which went into service on the Stockholm route. The aircraft was equipped with floats, but not skis, and so could be used in summer only. It remained in service until 1935.
A Swedish G 24 also participated in the rescue of the unfortunate Italian Umberto Nobile expedition to the North pole. This was the first time an aircraft had flown over the Arctic Sea without stops.

Military versions

Junkers offered the K 30 design to the Soviet forces, which ordered a total of 23 K 30s in 1925 and 1926. A production line for the military version K 30 was set up at A.B. Flygindustri at Limhamn in Sweden as the German aviation industry was prevented from building military aircraft in 1926. The parts for the K 30 aircraft were built at Dessau and then shipped to Limhamn, where A.B. Flygindustri built the K 30 under the designation R 42. Some of the R 42s were equipped with machine gun towers and bomb mountings. But several of the R 42s were also shipped without military equipment to Russia. These were later fitted with military equipment at Junkers' factory in Fili, Moscow. The R 42/K 30 was designated JuG-1 in the Soviet Union. They received five 7.62 mm machine guns and could carry a bomb load of 500 kg. This version was used to rescue the expedition of downed balloonist General Umberto Nobile in 1928.
Six more R 42s were delivered to Chile during 1926 plus three K 30s to Spain and two K 30s to Yugoslavia until 1931. The Spanish and Yugoslavian aircraft were produced at Dessau. The K 30 was equipped with either wheels, skis or floats. With the successful conversion of the G 24 into the single-engine aircraft F 24, Junkers was also thinking about a single-engine K 30 in 1931. Like the F 24, this K30do was to be equipped with the Jumo 4 engine and was similar to the initial G1Sa 24. However, no single-engine K 30s were built.

Record flights with the G 24

1926

Data from:Hugo Junkers'' Pionier der Luftfahrt – Seine Flugzeuge, Junkers Aircraft & Engines 1913–1945
;G 24 Prototype: Powered by one BMW IIIa and two Mercedes D.I engines in 1924.
;G 24: Improved version with one Junkers L2 and two Mercedes D.IIIa engines in 1925
;G 24a: Powered by three Junkers L2 engines, attachment on wings, smaller engine cowlings, sometimes also a Junkers L5 as a central engine. Two aircraft destined for Italy were fitted with Isotta Fraschini central engines.
;G 24ba: with three Junkers L2, strengthened attachments and engine mountings
;G 24b1a: seaplane version of the G 24ba for Aero O/Y
;G 24bi: with one Junkers L5 center engine and two L2 engines
;G 24ce: with three Junkers L5, enlarged wing attachment since 1926
;G 24e: with three Junkers L5
;G 24de: strengthened attachments, smaller engine cowlings
;G 24fe: enlarged center wing attachments
;G 24ge: further enlarged wing attachments
;G 24g1e: seaplane version of G 24ge, used for torpedo experiments
;G 24gu: one Junkers L5G central engine and two Junkers L5
;G 24gn: Junkers L5 center engine with, one built
;G 24he: with modified wing, separate undercarriage, aerodynamic cockpit, 14 passengers
;G 24h1e: seaplane version of G 24he
;G 24hu: with three BMW Va engines, one built
;G 24li: modified G 24a/b with Junkers L5 center engine
;G 24mai: Two modified G 24e aircraft with a Isotta Fraschini Asso 200 centre engine for Italy
;G 24nao: with three Rhone Jupiter engines, prototype for the K30
;G 24L: with three Junkers L5G engines
;F 24kae: was a single test bench for DB 600/DB 601 engines.
;F 24kai: a single test bench for the Jumo 211 engine
;F 24kau: with BMW VIau
;F 24kay:Test bench for Jumo 4 in October 1933, plus surviving Deutsche Luft Hansa F 24ko aircraft re-engined with Jumo 4 engines.
;F 24ko: with a single BMW VIU engine
;G3 S1 24: a projected ambulance aircraft from 1924, three Junkers L2 engines
;G1 Sa 24: a projected reconnaissance aircraft from 1924, single-engine
;G2 Sb 24: a projected bomber aircraft with several three-engine approaches
;K 30: military G 24 version of 1926
;K 30b: a fictitious Russian designation for the land version of the K 30
;K 30c: a fictitious Russian designation for the seaplane version of K 30
;K 30do: single-engine version of the K 30 of 1931, with a Jumo 4;not built
;W 41: test bench for Fo 4 diesel engine in August 1928
;TB-2: Soviet military designation for the K 30
;JuG-1: designation for Fili military conversions of the K 30/R 42

Operators

;: Aero O/Y