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The single Douglas DC-1 was the direct ancestor of the DC-3, an aircraft that would revolutionise civil aviation, and of the C-47/ Dakota family of military transport aircraft, the most important Allied transport aircraft of the Second World War.
The DC-1 was developed in response to a specification issued to Douglas by TWA. During the late 1920s most airlines were operating three-engined aircraft with wooden frames and metal skins, based like most military aircraft of the period on First World War technology. By the early 1930s these aircraft were becoming obsolescent, lacking the speed, range and passenger capability to satisfy the airlines.
Things got worse after the fatal crash of a TWA Fokker F-10A on 31 March 1931. In the aftermath of the crash the Bureau of Air Commerce ordered all operators of airlines with wooden frames to make regular inspections of the wing structures. The airline industry finally began to look for more modern all-metal aircraft. Not only would these aircraft be able to carry more passengers, faster, and over longer distances, they would also reduce the need for costly inspections.
In the first half of 1932 the most promising looking new aircraft was the Boeing Model 247, which would make its maiden flight early in 1933. This was an all-metal twin engined aircraft that could carry ten passengers, but Boeing’s entire production capacity would be taken up by a large order placed by United Air Lines (partly owned by Boeing).
TWA realised that their only chance to keep up with United was to develop their own aircraft. The new air line was to be a three engined monoplane, powered by 500-550hp supercharged engines, preferably of all-metal construction, and capable of carrying twelve passengers 1,080 miles at 150mph. The new aircraft also had to be able to take off from any airport used by TWA on two of the three engines. This was the most demanding part of the specification, for TAW used Albuquerque, at 4,954ft. Consolidated, Curtiss, Douglas, General Aviation and Martin were all sent this specification and asked to submit a design.
Douglas responded with the DC-1. Their design differed from the TWA specification by using two 700hp engines in place of the three 500hp engines requested. The design used strong multi-spar wings, while the wing centre-section was built into the central fuselage (the Boeing Model 247 had a simpler system, with the wing spars ran through the centre of the fuselage, where they obstructed the passenger cabin). From the side the fuselage of the DC-1 looked very similar to that of the later DC-3, but with flat sides. The fuselage was made tall enough to allow the passengers to stand upright in the central aisle. The wings already had the familiar DC-3 shape, with the swept-back leading edge and straight trailing edge, although were shorter and had blunt ends.
On 20 September 1932 TWA placed an order for one prototype, with the option to buy up to sixty production aircraft if the design was satisfactory. Work progressed rapidly, and on 1 July 1933, powered by Wright SGR-1820-F engines, the DC-1 made its maiden flight.
This first flight was not a success. Problems with the carburettor fuel lines meant that the engines cut out whenever the pilot attempted to climb, but this problem was soon overcome, and a series of successful tests followed. The most important of these came of 4 September 1933, when the DC-1 made a flight from Winslow, Arizona, to the troublesome airport at Albuquerque on a single engine. The DC-1 having passed this final test, TWA placed an order for twenty slightly modified DC-2s.
The single DC-1 had an eventful life. Douglas used it to investigate the use of Pratt & Whitney Hornet engines, while TWA used it for tests, and to establish a transcontinental speed record of 13 hours 4 minutes in February 1934. It was then passed on to the National Aeronautical Association, who also broke the transcontinental speed record (11 hours 5 mins), before breaking eight world records between 16-19 May 1935. The aircraft was then sold to Howard Hughes, who was planning his own record attempts, but delays meant that he would eventually use a Lockheed 14. The DC-1 was then sold to Viscount Forbes, Earl of Granard, and shipped to England. After a few months in his hands it was sold to a French company acting for the Spanish Republican Government. The aircraft survived the Spanish Civil War, before finally being destroyed in a non-fatal crash at Malaga in December 1940.