Design and Development
In 1923, the U.S. Army Air Service was interested in pursuing a mission to be the first to circumnavigate the earth by aircraft, a program called "World Flight". Donald Douglas proposed a modified Douglas Aircraft Company DT to meet the Army's needs. The two-place, open cockpit DT biplane torpedo bomber had previously been supplied to the Navy, thus shortening production time for the new series. The DTs to be modified were taken from the assembly lines at the company's manufacturing plants in Rock Island, Illinois and Dayton, Ohio. Douglas promised that the design could be completed within 45 days after receiving a contract. The Air Service agreed and lent Lieutenant Erik Nelson, a member of the War Department planning group, to assist Douglas. Nelson worked directly with Douglas at the Santa Monica, California factory, to formulate the new proposal.
The modified aircraft known as the Douglas World Cruiser (DWC), powered by a 420 hp Liberty L-12 engine, also was the first major project for Jack Northrop who designed the fuel system for the series. The conversion involved incorporating a total of six fuel tanks in wings and fuselage. For greater range, the total fuel capacity went from 115 gallons (435 liters) to 644 gallons (3,438 liters). Other changes from the DT involved having increased cooling capacity, as well as adding two separate tanks for oil and water. To ensure a more robust structure, a tubular steel fuselage, strengthened bracing, a modified wing of 49 ft (15 m) wingspan and larger rudder was required. The dual cockpits for the pilot and copilot/crewman were also located more closely together with a cutout in the upper wing to increase visibility.
Like the DT, the DWC could be fitted with either floats or a conventional landing gear for water or ground landings. Two different radiators were available, with a larger version for tropical climes. After the prototype was delivered in November 1923, upon the successful completion of tests on 19 November, the Army commissioned Douglas to build four production series aircraft. Due to the demanding expedition ahead, spare parts, including 15 extra Liberty engines, 14 extra sets of pontoons, and enough replacement airframe parts for two more aircraft were specified and sent to way points along the route. The last aircraft was delivered on 11 March 1924.
Read more about this topic: Douglas World Cruiser
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