Douglas 415 / C-74 Globemaster
In 1942 Douglas began to design a larger, would-be successor to the Douglas C-54. The new model, identified in project form as the Model 415, had the same four-engine, low-wing layout as its predecessor, but it was about half again as large dimensionally and twice as heavy. With 3,250hp (2,420kW) Pratt & Whitney R-4360-27 Wasp Major engines, it would cruise at 296mph (476km/h), considerably faster than the C-54. The pilot and co-pilot were separately enclosed in side-by-side bubble canopies, an arrangement later found far from satisfactory from a crew communication standpoint. It was a cantilever low-wing monoplane of all-metal construction, with a conventional tail unit, and retractable tricycle landing gear with twin wheels on each unit.
The C-74's fuselage provided accommodation for the crew and 125 troops, or 115 stretchers with medical attendants, or up to 21840kg of cargo.
Orders were received for 50 examples of a military version known as the C-74 Globemaster.
In 1945, Pan American Airways also recognized the new model’s potential and ordered 26 with seats for 108 passengers. As ‘DC-6’ was already assigned, the civilian version was called the DC-7. Unlike the C-54, the DC-7 was to have a pressurized cabin.
By the time of the first flight on September 5, 1945, the military order had been reduced to 14 units. One, with 103 passengers and crew, flown from the USA to the UK on 18 November 1949, was the first aircraft to fly across the North Atlantic with more than 100 persons on board.
With development costs shared by fewer military airplanes, the cost of the DC-7s rose accordingly. Pan American reassessed its needs, as well as the increased cost of the DC-7s, and elected to cancel its order altogether. Although the DC-7 failed as a civil airliner, Douglas did redesign the fuselage of the C-74 to create the C-124 Globemaster II.