MIAMI – Today in Aviation, the Junkers G.38, a large German four-engine transport aircraft, completed its maiden flight in 1929.
Only two G.38s were manufactured. Both aircraft flew as commercial transports for Lufthansa (LH) within Europe in the years leading up to WWII. During its early life, the Junkers G.38 was the largest landplane in the world.
During the 1930s, the design was licensed to Mitsubishi, which had built and flown a total of six aircraft in a military bomber/transport configuration designated as Ki-20. The Junkers G.38 had a Crew of seven. Onboard mechanics were able to operate the engines in flight due to the G.38’s blended wing design, which provided access to all four power plants.
Design and Development
During the 1920s, Hugo Junkers made several attempts to produce large-scale commercial transport. His initial attempt, the four-engine JG1, was developed between 1921 and 1922, but Junkers was forced to destroy an incomplete aircraft based on the post-WWI Allied demands of the Treaty of Versailles.
In 1925, Junkers published the design specifications for the proposed eighty trans-Atlantic passenger aircraft-the J.1000 project. Once more, at the end of the decade, the Junkers design team began the G.40 project as a trans-Atlantic mail aircraft. From the G.40 design, which was configured as a seaplane, Junkers also developed a landplane design, which he designated G.38.
Despite the interest of the German armed forces in the G.40 variant, Junkers moved forward with a landplane design. With financial backing from the Reich Air Ministry (Reichsluftfahrtministerium), the G.38 was taken to the construction phase.
The first Junkers prototype—3301 and D-2000—flew for the first time on November 6, 1929, with four diesel engines: two Junkers L55 V-12 engines and two 294 kW L8 inline-6 engines, with a total power rating of 1470 kW (1971 hp). The Reich Air Ministry bought the D-2000 for demonstration flights and took delivery on 27 March 1930.
The G.38 set four world records on its flight tests, including speed, distance, and duration, for aircraft with a payload of 5,000 kg. On May 2, 1930, LH placed the D-2000 in commercial service for both scheduled and charter flights.
The G.38 was structurally compliant with the standard Junkers practice, with a multi-tube spar cantilever wing covered, like the rest of the aircraft in hardened, corrugated Duraluminium, or Duralumin, as it was known as its trade name.
On February 2, 1931, the Leipzig-based Junkers’ yard re-engineered the D-2000 with two Junkers L8 and two L88 engines with a total power rating of 1764 kW (2366 hp) and an increase in passenger capacity from 13 to 19.
As the largest plane in the world, passenger accommodation was sumptuous by today’s standards and was meant to compete with that found on the Zeppelin service offered by DELAG. The aircraft was unique in that the passengers were sitting in the wings, which were 1.7 m (5 ft 7 in) thick at the root.
There were two seats in the extreme nose, too. The front edge of each wing was fitted with sloping windscreens giving these passengers the forward-facing view usually available only to Pilots. There were three 11-seater cabins, plus smoking cabins and laundry rooms. The type’s capacity would later be increased for its operations with LH.
Operations and Upgrades
On July 1, 1931, LH began scheduled service between Berlin and London on flights of up to 13 passengers. The London-Berlin service was stopped in October 1931 to upgrade the aircraft and expand the passenger cabin of the D-2000. Construction lasted from this time until mid-1932 when a second deck was built within the D-2000 fuselage. This increased cargo capacity and seats for up to 30 passengers.
In addition, the D-2000 engines were again upgraded to four L88s, giving a total power of 2352 kW (3,154 hp). Also at this time, the registration of the D-2000 was changed to D-AZUR. In the meantime, the second G.38, with factory number 3302 and c/n D-2500 (later changed to D-APIS), was built with a double-deck fuselage and a capacity of 34 passengers.
Six passengers were transported three per wing at each of the leading edges, while the remaining 22 were transported on two levels in the fuselage. Lufthansa used D-APIS on a scheduled service to the cities of Berlin, Hanover, Amsterdam, and London. This aircraft was named General Feldmarschall von Hindenburg.
In 1934, D-2000 and D-AZUR were upgraded with the Jumo 4 engines, giving them a total power rating of 3000 kW (4023 hp). Both aircraft were in service until 1936 when D-AZUR crashed in Dessau during a post-maintenance test flight. LH had to write off this aircraft due to extensive damage. Test Pilot Wilhelm Zimmermann survived the crash and there were no further casualties.
The second G.38 (marked D-2500, and later D-APIS) operated successfully in the LH fleet for nearly a decade. With the outbreak of WWII, the D-2500/D-APIS was pressed into military service as a Luftwaffe transport vessel. Alas, the aircraft was destroyed on the ground on May 17, 1941, during an air raid by the RAF on Athens.