<p>Lockheed's reputation was founded on its outstanding series of fast single-engined Vega, Air Express, Sirius, Altair and Orion monoplanes, but the impact of twin-engined designs, such as Boeing's Model 247 and the Douglas DC-1, forced the Burbank, California-based Lockheed Aircraft Corporation to follow suit. Work on such a design began at the end of 1932, and the prototype Model 10 Electra was rolled out on 23 February 1934, making its first flight later that day. Flight testing occupied almost three months, at the end of which the Bureau of Air Commerce awarded the Model 10 Approved Type Certificate No. 551 on 11 August 1934.
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<p>Powered by two Pratt & Whitney Wasp Junior SB engines, and accommodating 10 passengers and a crew of two, the all-metal L 10-A Electra aroused the interest of Northwest Airlines and Pan American Airways before the prototype had been built. Both ordered the Electra, and Northwest received the first two of its order, for training and route-proving, before certification.
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<p>Pan American had held in store a number of surplus Wasp SC engines and these were fitted to the airline's eight L 10-Cs. Eastern Airlines' selection of the 450-hp (336-kW) Wright R-975E-3 Whirlwind radial produced the L 10-B, while Electras with the 550-hp (410-kW) Wasp R-1340-S3H1 engine were designated L 10-E. Total production of 149 aircraft comprised 107 10-As, 19 10-Bs, eight 10-Cs and 15 10-Es.
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<p>In 1936 two Electras were supplied to the US Navy and US Coast Guard, designated XR2O-1 and XR3O-1, respectively. The former was a Model 10-A for the use of the Secretary of the Navy and the latter a Model 10-B used by the Secretary of the Treasury. Four Lockheed 10-As were also purchased by the US Army Air Corps; three were delivered in 1936 under the designation Y1C-36 and the fourth, in 1937, as a Y1C-37 for the National Guard Bureau. In 1942 26 civil Electras were impressed for communications duties, comprising 15 10-As which became designated UC-36A, four 10-Es (UC-36B) and seven 10-Bs (UC-36C).
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<p>Of particular importance was the single XC-35 which, powered by two 550-hp (410-kW) Pratt & Whitney XR-1340-43 engines, was first flown on 7 May 1937. Built to USAAC order for experiments with cabin pressurization and engine supercharging, this had a redesigned fuselage of circular cross-section and had the standard cabin windows eliminated. For the sponsorship of this development, and its use in what proved to be a valuable research program, the US Army was later awarded the Collier Trophy.
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<hi style=hdr1>Specification</hi>
<list style=aflst>
<item><hi format=bold>Type:</hi> twin-engined light transport aircraft
<item><hi format=bold>Powerplant (Y1C-36):</hi> two 450-hp (336-kW) Pratt & Whitney R-985-13 Wasp Junior radial piston engines
<item><hi format=bold>Performance:</hi> maximum speed 201 mph (323 km/h) at 5,000 ft (1,525 m); cruising speed 194 mph (312 km/h) at 5,000 ft (1,525 m); service ceiling 24,000 ft (7,315 m); range 666 miles (1,072 km)
<item><hi format=bold>Weight:</hi> empty 7,100 lb (3,221 kg); maximum take-off 10,500 lb (4,763 kg)
<item><hi format=bold>Dimensions:</hi> span 55 ft 0 in (16.76 m); length 38 ft 7 in (11.76 m); height 10 ft 1 in (3.07 m); wing area 458.3 sq ft (42.58 m<su>2</su>)
