World War 2 (1939-1945) pushed the American military to require all sorts of aircraft types and aviation concerns were only too happy to answer the call. Douglas Aircraft Company had been making aircraft for quite some time, having established operations as far back as 1921, and the firm went on to provide some of the most famous platforms of the war - the A-26 "Invader" attack system, the SBD "Dauntless" naval dive bomber and the C-47 "Skytrain" transport. The Skytrain was a further development of the earlier DC-3 passenger hauler of 1936 and was used extensively during the war with production exceeding 10,000 units before the end.
Following the DC-3 into service for Douglas was the DC-4 product. This model introduced a rather modern tricycle undercarriage, featured two engines on its low-mounted monoplane wing appendages and saw military service as the C-54 "Skymaster". Over 1,200 of this model were produced from the period spanning 1942 to 1947. It was this aircraft that was selected by the Douglas team for modification into a large, long-range heavy-lifter for the U.S. Army Air Forces. Engineers essentially retained the same design lines of the original but made a dimensionally larger version of their DC-4 with working beginning in 1942. This produced the "Model 415" which impressed Army officials enough to order it without a prototype or developmental products as part of a hurried program - a rarity for military market aircraft. The Army order covered a solo test bed platform and 50 production-quality units for service.
By this point in the war, the Army required a heavy-hauler to move man, machine, and supplies across vast distances of ocean. The American military was operating in North Africa, Europe and the Pacific where all manner of war-making goods would be needed. The Model 415 was certainly a step in the right direction from a company experienced in the design and delivery of transport types for military service. The Model 415 was already some 30 feet longer than the C-54 in service, promising even greater strategic capabilities.
The Model 415 became the C-74 "Globemaster" in the U.S. military and featured a long tubular fuselage with the cockpit at front and an unpressurized cargo hold at center. Interestingly, the pilot and copilot sat under individual canopies over the nose - no doubt a detrimental quality to communication and a "feature" that was soon lost on operational models. A tricycle undercarriage was once again used and the low-mounted wing mainplanes now carried two engines each, these engines driving large-diameter, four-bladed propellers. The tail was conventional, featuring a single vertical tail fin with low-set horizontal planes. The standard operating crew numbered five and dimensions included a length of 37.8 meters, a wingspan of 53 meters and a height of 13.3 meters. Empty weight was 39,100 pounds with a Maximum Take-Off Weight (MTOW) of 172,000 pounds. Its hold could carry 125 combat-ready infantry, light armored vehicles, medical litters with full staff or general cargo. Performance from the 4 x Pratt & Whitney radial engines (3,250 horsepower each), coupled to the streamlined design, offered speeds reaching 330 miles per hour, ranges out to 3,400 miles, a service ceiling up to 21,300 feet, and a rate-of-climb of 2,605 feet per minute.
Development of the aircraft proved slower than needed for the first unit was not unveiled until August of 1944 and a first flight not recorded until September 5th of that year. By this time, D-Day had occurred in northern France and opened war along a new front. The fifth C-74 aircraft completed was modified into what would become the DC-6 and this went on to serve militarily as the "C-118".
With the collapse of Germany in May of 1945 and the end of the Japanese Empire that September, the U.S. military abandoned many aircraft initiatives including its contract for fifty of the C-74. Fourteen aircraft were completed before the cancellation and this also affected Douglas' plans to convert the C-74 as a civilian passenger long-hauler (as the "DC-7", company "Model 415A"). C-74s served under the United States Army Air Forces until the air service portion was reworked to become the United States Air Force. One example saw service during the Berlin Airlift of 1948 (alongside C-47s and C-54s) and was pressed into service during the Korean War (1950-1953). In the latter commitment, the C-74 was used to ferry supplies from the American west coast to Hawaii while bringing back injured - it did not enter the formal theater of war.
While limited in procurement and lacking the needed spares, C-74s were eventually pushed to the brink so much so that the line was beginning to show its wear-and-tear by the mid-1950s. In 1956, the series was laid up at Davis-Monthan Air Force Base of Arizona and a bulk of the fleet was scrapped by 1965. A few ended their days in the civilian market but, sadly, non survived the test of time.
The C-74 had a chance to become an classic heavy-hauler of World War 2 but events dictated its reach in-the-field and limited production dictated its longevity in American service. The upcoming C-124 "Globemaster II" would go one to see much better numbers with 448 built and these serving the USAF until 1974.