During the early part of its flying career, the Junkers model G.38 was the largest land-based airplane anywhere in the world. What's more is the giant aircraft was developed under the restrictions of the Treaty of Versailles which hampered German industry following World War 1 (1914-1918) but fittingly played its role during the "Golden Age of Flight" that saw aircraft evolve considerably. The aircraft proved a great study in blended body-wing design for the period and two examples were built primarily for the passenger-hauling role.
Like other Junkers aircraft before it, the G.38 was completed with corrugated duraluminium stressed metal skin. The large cantilever wings were deliberately designed as deep, measuring some 5.7 feet, to house passenger cabins and a pair of engine nacelles. The fuselage, with the cockpit flight deck (stepped arrangement) overlooking the nose, tapered towards the tail. The tail itself was capped by a triple-rudder configuration sandwiched between a pair of horizontal planes. The undercarriage was wheeled though fixed in flight and spatted for some basic aerodynamic efficiency. An operating crew of seven was carried.
Dimensions included a length of 76.1 feet, a wingspan of 144.3 feet and a height of 23.6 feet. Empty weight registered 32,900 lb against a Maximum Take-Off Weight (MTOW) of 46,825 lb.
To power the massive bird, 2 x Junkers L55 V12 water-cooled inline piston engines were initially carried in the inboard engine mountings while 2 x Junkers L8a 6-cylinder, water-cooled inline piston engines were carried at the outboard positions. These gave an output power of 413 horsepower each. Because of the depth of the wing design (internally), not only could passengers be carried in the structures but flight engineers could also access the powerplants in-flight and make necessary repairs / adjustments.
Performance specs included a maximum speed of 140 miles per hour with a cruising speed of 110 miles per hour. Though slow the beast ranged out to 2,150 miles and its service ceiling reached 12,105 feet - certainly better qualities than competing Zeppelin passenger/cargo haulers of the period.
Passenger capacity eventually numbered thirty across three compartments and the persons lucky enough to secure a ticket in the wings were given forward-facing windscreens built directly into the wing leading edges. Lavatories were built-in as were "smoking rooms". The aircraft's MTOW also provided the system with an excellent cargo-hauling capability when used in the dedicated transport role.
First-flight of the G.38 (also recognized as the "D-2000") came on November 6th, 1929 and the launch customer was German carrier Lufthansa with flights seen from Berlin to London beginning on July 1st, 1931. Revision work on the aircraft followed from October onward and resulted in greater passenger-hauling capabilities (a second deck being added). The work also included installation of four L88 series engines of 800 horsepower each. The D-2000 prototype aircraft eventually crashed in 1936 following some maintenance work and the damage proved so great the aircraft was not repaired and set back into active service.
A second prototype aircraft ("D-2500") finished construction and given the same twin deck internal design and its passenger-hauling capability was slightly increased to thirty-four travelers.
Flights soon resumed to various points within Europe and out to London. In 1934 the engine fits were replaced by Junkers 4 (Junkers Jumo 204) series powerplants which boosted overall output power by nearly 1,000 horses. With the D-2000 crashing in 1936, D-2500 continued on alone until Germany found itself in a world war over Europe once again. The D-2500 was requisitioned as a military transport and continued in this role until May of 1941 when she was bombed by Royal Air Force attackers where she sat in Axis-controlled Athens, Greece.
The large aircraft design was licensed out to Mitsubishi during the 1930s which allowed the company to produce a military-minded bomber-transport type. This product was designated "Ki-20" and six were completed from the period spanning 1931 to 1935. These 10-man bombers served with the Imperial Japanese Army Air Force and had a first-flight recorded in 1932.