Junkers G.38 – Germany’s Enormous Transport

The Junkers G.38 was a large four-engined transport aircraft that was first flown in the late 1920s. Initially constructed to capitalise on the relatively new passenger air travel industry, this commercial transport would have taken cargo and passengers to America from Europe.

With a maximum capacity of 30-34 people, it was a seriously impressive machine for the time it was built. But due to how rapidly the aeronautical industry was developing, it was very quickly out of date.

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Development

In the late 20s, the Junkers Aircraft and Motor Works started the G.40 project – an ambitious design to carry cargo across the Atlantic Ocean. The G.40 was a seaplane and her sister the G.38 was the land-based counterpart.

Germany’s armed forces were extremely interested in the G.40 project. But despite this, it was the G.38 design that went ahead, thanks to financing from the Reich Air Ministry (RAM).

G.38 Blueprints
The unique shape of the G.38 can be seen in this blueprint drawing.

The RAM was responsible for the development and production of aircraft for the Luftwaffe. They had decided for military use the land-based G.38 would be better suited to their needs. 

Design

The G.38 was big, really big. With a wingspan of 44 m (144 ft 4 in) and a sizeable weight of 14,920 kg (32,893 lbs) empty. Fully laden, she would fly through the sky at 24,000 kg (52,911 lbs).

For the late 1920s, an aircraft this large was unheard of. Around this time a lot of aircraft manufacturers were experimenting with larger designs – without much success. 

Unusually, of the G.38’s four engines, two of them were different types. Both were Junkers diesel engines. Whilst similar on the surface, they were completely separate designs.

The innermost engines were the Junkers L88, a water-cooled, 45.8 litre V-12. Whereas the outermost engines were the L8a – a 23 litre six-cylinder in-line engine. Each produced a similar amount of power – 410 horsepower.

The G.38 used two different types of engines
Everything about the aircraft was unique, even its engines. Indicated here by the two types of propellers, it used two different types of engines.

Despite a total of almost 2,000 hp, the G.38 could only manage a measly 140 mph top speed. Whilst in the cruise, she would only fly at 110 mph.

Arguably the most unique features of the G.38 was its passenger compartments, which were located in the wings. The leading edge of the wings had windscreens over them so passengers could see out of the front of the aircraft.

The G.38’s first flight took place on November 6, 1929.

Operational Use

Two G.38s were built in total, the D-2000 and the D-2500. The D-2500 was the second to be built, had a slightly different internal layout and could accommodate more passengers and cargo.

Initially, the D-2000 was used for demonstration flights during 1930 and gained a number of world records for aircraft carrying a payload of over 11,000 lbs (5,000 kg).

It was one of the largest aircraft in the world at the time.

The aircraft was enormous and one of the largest in the world
The G.38 was only beaten in size by later aircraft like the Tupolev ANT-20. Image by Bundesarchiv CC BY-SA 3.0 de.

Both G.38s were delivered to Luft Hansa by 1932 and used as passenger aircraft, moving up to a whopping 13 passengers between London and Berlin. This lasted 4 months before it was decided the first G.38 was to be upgraded to the same specification as the second aircraft that was built.

Once the work was completed the D-2000 could carry more load (now up to 30 passengers) and had more powerful engines. This time it used four of the same L88s engines making over 3,100 hp.

The D-2000 went through a second upgrade in 1934, with even more powerful Jumo 4 engines installed – increasing power by another 1,000 hp. This brought the total to just over 4,020 hp.

Upgraded G.38 D-2000
This image shows the G.38 D-2000 after it received more powerful engines in 1934.

The Jumo 4 engine was first produced in 1929, later going into service in 1932 and was a 6 cylinder opposed piston diesel engine.  

Both aircraft were in service at the same time and saw some success. They were flying until 1936, when the G.38 D-2000 crashed after a test flight. Fortunately, there were no casualties but Luft Hansa wrote off the aircraft due to the amount of damage it sustained.

The D-2500 on the other hand flew with the airline for almost a decade. Once World War II started she was conscripted into military service and became a transport aircraft for the Luftwaffe

She met a grisly end being destroyed by the RAF on the runway in Athens in May 1941. 

Ki-20

After the successful flights of the first G.38, its potential as a bomber was quickly noticed. Mitsubishi showed a clear interest in this idea from the start and in 1930 signed a licensing agreement with Germany for the production of the K51 in Japan. 

A team from Junkers went to Japan to oversee the initial build and to support Mitsubishi.

Ki-20 Heavy Bomber
A Japanese Mitsubishi K-20 heavy bomber.

The first example of this aircraft – named the Ki-20 – was produced in 1931. A further four were produced by 1935. Just like the German G.38, the Japanese also re-engined their aircraft several times for better performance. 

The Ki-20 was used by Japan as a heavy bomber right up until the beginning of World War II.

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Specifications

Crew: 7
Passengers: 30 for the D-2000 and 34 for the D-2500/D-APIS
Length: 23.21 m (76 ft 2 in)
Wingspan: 44 m (144 ft 4 in)
Height: 7.2 m (23 ft 7 in)
Empty weight: 14,920 kg (32,893 lbL
Max takeoff weight: 21,240 kg (46,826 lb)
Powerplant: 2 × Junkers inboard L88 V-12 water-cooled diesel piston engines, 2 × outboard Junkers L8a six-cylinder, water-cooled, in-line diesel piston engines, 413 hp
Propellers: 2-bladed wooden propellers outboard, 4-bladed wooden propellers inboard
Service ceiling: 3,690 m (12,110 ft)
Maximum speed: 140 mph (225 km/h)
Cruise speed: 109 mph (175 km/h)
Range: 2,150 mi (3,460 km)