Junkers G 24

Junkers
Industry	Aircraft manufacturing
Founded	1925
Founder	Ernst Zindel (designer)
Headquarters	Dessau, Germany
Products	Junkers G 24 passenger aircraft

The Junkers G 24 was a German passenger aircraft featuring three engines and an all-metal low-wing monoplane design, manufactured by Junkers beginning in 1925. A variant equipped with a single engine was known as the Junkers F 24.

Development

The expansion of German civil aviation during the 1920s created a need for larger capacity passenger planes. The G 24 emerged as an enlarged derivative of the F 13, initially conceived by Ernst Zindel as a single-engine model. Due to restrictions imposed by the Treaty of Versailles that limited engine power in Germany, Junkers opted for a tri-motor configuration utilizing three lower-powered engines. This design enabled flight but constrained its commercial appeal. The strategy was to export these tri-motors to foreign markets where operators could replace the triple engines with a single, more powerful unit by removing the wing’s center section. However, the Military Inter-Allied Commission of Control prohibited this aircraft as a military design.

Subsequently, Junkers reintroduced the concept as the G23, which received Allied approval for commercial use. Nevertheless, production persisted under the G24 name, maintaining the three-engine layout. This arrangement provided operational benefits: unlike contemporary twin-engine aircraft that struggled to sustain altitude on one engine without excessive power and fuel consumption, the tri-motor could safely continue flying and climbing on two engines.

On 1 May 1926, Deutsche Luft Hansa inaugurated night passenger flights on the Berlin–Königsberg route using G24s, becoming the first airline worldwide to offer scheduled nighttime passenger service. Prior night operations had been limited to mail and cargo; emergency landings at night were considered too hazardous, with pilots often forced to parachute if engine failure occurred. Equipped with instruments for blind flying and radio navigation—supported by a radio operator seated within the passenger cabin due to cockpit constraints—the G24 significantly enhanced safety for nocturnal flights.

From 1925 through 1929, Junkers produced at least 72 units of the G24, delivering 26 of these to Luft Hansa. The aircraft established payload records; notably, Fritz Horn completed a flight covering 2,020 km while carrying a 1,000 kg load at an average velocity of 140 km/h over more than fourteen hours.

On 24 July 1926, two G24s undertook a remarkable journey spanning roughly 20,000 km between Berlin and Peking with only ten stops, concluding on 8 September. Although plans existed to extend the trip to Shanghai, military conflicts prevented continuation. The aircraft returned to Berlin by 26 September. This expedition contributed to laying the foundation for a transcontinental Euro-Asian air route later that year.

Military versions

In the course of Soviet-German collaboration during the 1920s, Junkers developed military adaptations of the G 24 to fulfill Soviet bomber requirements. The initial twin-engine Ju 25 bomber project was abandoned due to excessive costs and complications in cooperation. Instead, chief designers Ernst Zindel and Hermann Pohlmann produced the G3S1 24, a modified version of the G 24ba configured as an air ambulance. Additional variants included the reconnaissance-oriented G1Sa 24 (single-engine) and the bomber model G2sB 24, derived from the G 24he with redesigned center wing and nose sections equipped for forward-firing armament. These developments culminated in a general military variant designated K 30 in 1926.

Junkers marketed the K 30 to Soviet forces, who placed orders for twenty-three units between 1925 and 1926. Due to prohibitions on German military aircraft manufacture, components were produced in Dessau and assembled by A.B. Flygindustri in Limhamn, Sweden under the name R 42. Some R 42s were outfitted with machine guns and bomb racks; others were delivered unarmed to Russia for subsequent armament fitting at Junkers’ Fili facility. Known within the USSR as JuG-1, these planes carried five machine guns of 7.62 mm caliber and could bear up to 500 kg of bombs. The R 42/K 30 notably took part in the rescue operation of General Umberto Nobile’s crashed expedition in 1928.

Further exports included six R 42 units sent to Chile (1926), three K 30s delivered to Spain, and two K30s supplied to Yugoslavia through 1931; Spanish and Yugoslav models were assembled at Dessau. The K30 was adaptable with wheels, skis, or floats for varied operational environments. Junkers also explored a single-engine version named K30do, powered by a Jumo 4 engine in 1931; however, this variant never progressed beyond planning stages.

Design

The Junkers G 24 was a three-engine, all-metal low-wing monoplane designed for passenger transport, evolving from the successful twin-engine Junkers F 13 airliner. Its tri-motor layout combined the efficiency of a central engine with the safety benefits of two additional wing-mounted engines, providing over 50% power reserve to enhance reliability. Aerodynamically refined engine cowlings minimized drag, while the positioning of propellers reduced the likelihood of damage in case of engine failure. The aircraft was engineered to retain controllability even if one of the wing engines ceased functioning.

Both the cantilever wings and fuselage were clad in corrugated duralumin panels, which improved the structure’s ability to absorb and distribute stress in conjunction with internal bulkheads. The main fuselage section carried the majority of structural loads and, together with the low-set wings, offered protection to occupants during hard landings. Its modular construction—applied to wings, fuselage, and engine mounts—facilitated efficient production, road transport, and swift replacement of damaged components or engines.

Configured for airline service, the cabin held approximately 14 leather-upholstered seats arranged alongside windows with an aisle enabling passenger movement. A partition separated the passenger cabin from the cockpit; passengers could observe flight instruments such as altimeter and airspeed through an internal window. Hand luggage was stored in overhead nets, while larger baggage was placed in a compartment located near the lavatory. The spacious rear fuselage allowed passengers to move freely without disrupting flight balance, as pilots compensated by adjusting stabilizers.

The cockpit was equipped with dual flight controls to allow pilot relief during extended flights and featured an array of instruments: compass, gyroscopic inclinometer, engine tachometers, radiator temperature gauges, oil pressure meters, fuel level indicators, and a longitudinal inclinometer. Control elements included ignition switches, throttle levers, fuel valves, and radiator shutters; stabilizer and rudder trim were managed via handwheels positioned between the pilot seats and foot pedals.

The landing gear consisted of steel struts streamlined with duralumin fairings to reduce aerodynamic drag and attached using bolts and bayonet fittings for rapid removal. It incorporated Junkers’ reliable shock absorbers enclosed within duralumin housings for enhanced durability during rough touchdowns and improved airflow. Large disc wheels fitted with balloon tires could withstand braking forces up to 20 metric tons. The wheeled undercarriage could be swiftly replaced by aluminum floats or skis; floats were designed with multiple watertight compartments accessible through inspection hatches and mounted via removable intermediate wing sections—unlike the wheeled gear which connected directly to the fuselage.

Operational history

Initial deliveries of the G 24 began in early 1925, and by late 1927 these aircraft were operating on nearly all scheduled routes across Central Europe.

Luft Hansa, which operated the largest fleet of G 24s, initiated modifications in March 1928 to convert their aircraft into single-engine configurations. This process involved shortening the wingspan and replacing the central engine with a BMW VIU powerplant, resulting in the F 24ko variant. Between 1928 and 1930, eleven G 24s underwent this conversion. By July 1933, most had been further re-engined with Jumo 4 units and redesignated as F 24kay. Many continued service at the outbreak of the Second World War in 1939, primarily functioning as cargo aircraft for Luft Hansa.

In 1926, Finnish carrier Aero O/Y procured a G 24 for its Stockholm route; this aircraft was equipped with floats for summer operations and remained active until 1935.

A Swedish-operated G 24 played a significant role in rescuing members of Italian explorer Umberto Nobile’s North Pole expedition, completing the first nonstop flight over the Arctic Sea.

1926

May 1 – Deutsche Luft Hansa initiated the inaugural passenger night service operating between Berlin and Königsberg.
July 24 – During the Peking expedition, two Luft Hansa G 24 aircraft (D-901 and D-903) completed a flight exceeding 20,000 km (12,400 mi) to Peking.

1927

April 1 – Waldemar Roeder established a new world distance record piloting a G 24L loaded with a 2,000 kg (4,410 lb) payload, covering 1,013.18 km (629.56 mi) in 7 hours and 52 minutes.
April 4 – Fritz Horn surpassed previous distance achievements with a G 24L carrying a 1,000 kg (2,200 lb) load over 2,026.36 km (1,259.12 mi) in 14 hours and 23 minutes.
April 10 – Hermann Roeder set a world speed record flying a G 24L with a 2,000 kg payload over 500 km (310 mi) at an average speed of 175.75 km/h (109.21 mph), also breaking the record for a 100 km distance at 179.24 km/h (111.37 mph).
June 1 – Pilot Zimmermann achieved a speed record on a G 24L carrying a 2,000 kg payload over 100 km between Dessau and Leipzig at 207.26 km/h (128.79 mph).
June 28 – Zimmermann further improved the speed record with a 1,000 kg payload reaching 209.115 km/h (129.938 mph).
August 4 – The South Atlantic expedition flight commenced with a G 24h1e departing Severa aiming to cross the North Atlantic from east to west between Norderney and the Azores but was aborted following an accident.
August 6 – A K 30 seaplane achieved FAI World Records for speed at 171 km/h (106 mph), distance at 1,176 km (731 mi), and flight duration of 10 hours and 42 minutes while carrying a payload of 1,000 kg on a route of the same length.

1928

June 23 – The Afghanistan expedition flight began involving one G 24 and two F 13 aircraft.

Accidents and incidents

On November 6, 1929, a Deutsche Luft Hansa Junkers G 24bi named Oberschlesien (D-903) crashed in dense fog near Marden Park, Surrey, England during its return from Amsterdam to Croydon Airport; four crew members and three passengers lost their lives.
On February 7, 1930, a Chilean Air Force Junkers R-42 J6 was forced to ditch near Punta Arenas due to engine failure resulting in three fatalities out of six occupants.
On November 7, 1930, Syndicato Condor’s Junkers G 24 Potyguar sank off Iguape, São Paulo with one fatality among eight onboard.
On August 31, 1932, AB Aerotransport’s Junkers G 24 Svealand crashed during an emergency landing in the Netherlands following engine failure; both pilots perished.
On October 1, 1938, Syndicato Condor’s G.24ce Ypiranga executed an emergency landing at Coruripe port without casualties; the aircraft was subsequently dismantled.
On August 24, 1939, a Deutsche Luft Hansa Junkers F.24 Düsseldorf made a forced landing in Germany after an engine fire during Daimler-Benz engine test flights; both pilots died.

Variants

Information sourced from: Hugo Junkers Pionier der Luftfahrt – Seine Flugzeuge and Junkers Aircraft & Engines 1913–1945

G 24 Prototype: Equipped with one BMW IIIa engine (180 hp) alongside two Mercedes D.I engines (100 hp) in the year 1924.
G 24: Powered by one Junkers L2 engine (195 hp) plus two Mercedes D.IIIa engines (160 hp) introduced in 1925.
G 24a: Featured three Junkers L2 engines or occasionally a central Junkers L5 engine (310 hp); two Italian units were fitted with Isotta Fraschini central powerplants.
G 24ba: Reinforced mounting points incorporating three Junkers L2 engines.
G 24b1a: A seaplane variant developed for Aero O/Y.
G 24bi: Configured with one central Junkers L5 engine complemented by two L2 engines.
G variants ce/e/de/fe/ge/g1e/gu/gn/he/h1e/hu/li/mai/nao/L: Represented multiple engine upgrades and structural adaptations including seaplane models and test platforms for diesel and Daimler-Benz powerplants.
F variants kae/kai/kau/kay/ko: Served as testbeds for DB series engines such as DB600/601, Jumo models including Jumo211 and Jumo4, as well as BMW VIu engines.
Military adaptations encompassed K30 versions along with proposed ambulance, reconnaissance, and bomber configurations.

Operators

Afghanistan: Afghan Air Force
Austria: Ölag
Brazil: Syndicato Condor
Chile: Chilean Air Force
Finland: Aero O/Y
Germany (Weimar Republic): Deutsche Luft Hansa, Luftwaffe, Condor Syndikat
Greece: SCHA, Hellenic Air Force
Italy: Ala Littoria, Regia Aeronautica, Transadriatica
Poland: Aerolot (operated briefly)
Spain: Unión Aérea Española, CLASSA, LAPE, Spanish Republican Air Force
Sweden: AB Aerotransport
Switzerland: Ad Astra Aero, Swissair
USSR: Aeroflot, Soviet Air Force
Turkey
Kingdom of Yugoslavia: Yugoslav Royal Air Force

Citations

Bibliography

Guenther Stauch, Das Große Buch der Lufthansa, Geramond Verlag, Munich, Germany, 2003.
Anthony L. Kay, Junkers Aircraft & Engines 1913–1945, Putnam Aeronautical Books, London, UK, 2004.
Karl-Dieter Seifert, Der deutsche Luftverkehr 1926 – 1945 – auf dem Weg zum Weltverkehr, Bernhard und Graefe Verlag, Bonn, Germany, 1999.
John Stroud, "Wings of Peace: No.11: Junkers G23 and 24", Aeroplane Monthly, August 1984.
Wolfgang Wagner, Hugo Junkers Pionier der Luftfahrt – Seine Flugzeuge, Bernard & Graefe Verlag, Bonn, Germany, 1996.
"Junkers Airplane 'G 24': All-metal Commercial Airplane," National Advisory Committee for Aeronautics (NACA), June 1927.

External links